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Building Tips and technical articles. => Building techniques => Topic started by: Doug Moon on December 26, 2012, 10:54:31 PM
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A while back I started a new Riff Raff.
I have been snapping some photos along the way.
1. The list! I build from scratch. Not even a plan. The list helps me stay on track. (Note step 27)
2. The ribs. I cut and sanded ribs to match the lost foam jig from 1/16 balsa I had on hand.
3. Sig wood order. Enough for several planes.
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4. Jig setup with shims and the trailing edge stock.
5. About half the ribs installed. You can see the leading edge molds drying in the back ground.
6. All the rib installed.
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7. Trailing edge sheer webbing. It is a must with Warren Truss rib layouts. It keeps the TE from sagging.
8. I sheer web the back end prior to installing the TE itself. This helps level it out.
9. The wing completed with cap strips but no center section sheeting 6.0 oz. at that stage, pretty average. Ready for bell crank, tip weight box, tips, and line slider.
10. Installed bell crank post. Lead outs, and short push rod. Bell crank is completed and ready to go in. Once the bell crank was installed onto the post I then spun it with compressed air at a very high speed for a good while in both directions. This "wears" it in. A little trick we do to the wheels in the pine wood derby. After just a few minutes of the high speed spin this thing is smooth as silk.
This is the 16th wing built out of this jig. The foam rib forms have seen their better days. Plus I have been working all these years off of Bob Hunt's earlier version, around 2001-2002, of the steps needed to complete the wing. Plus a few turns of my own I have picked up along the way. Once this one was removed from the jig for the first time it had an odd warp in it. I am not sure it was actually a warp. Upright or inverted the trailing edge would lay nice and flat in the jig. But inverted the leading edge was very slightly raised. This is an odd one. I think the rib shapes are finally showing they are not all that perfect anymore. A conversation with Bob and I would try very tight cap strips to see if they might push the wing into place. This along with some good old water, some weights, and shims it was straightened right out and is holding this shape nicely over the past week.
I have since read Bob's updated methods to the lost foam building system and will be making some sorely needed changes to my routine the next time I do this. Of course a new jig will be in order as well. Or I might just go foam.
I will keep you posted as I move along.
Thanks for looking.
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Thanks for posting the pics Doug.
Any source of info is very welcomed, since I'm at Lost Foam 101...
Bob sent me this pic showing the support ribs to prevent the sagging.
Gotta ask him if the TE shearwebs are still necessary though.
Marcus
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Yep, that's Bob's blue building table. I would think with the support ribs in place you would be good to go without the sheer webbing. But either way choose you will have to so something to keep it from sagging.
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"I have since read Bob's updated methods to the lost foam building system and will be making some sorely needed changes to my routine the next time I do this. Of course a new jig will be in order as well."
Hi Doug:
Glad the new instruction booklet was helpful. I want to repeat the offer here that I made elsewhere on this forum to send those PDF files of the updated Lost-Foam instructions to anyone who wants them. There is no charge for this, and they will be sent in four separate email messages as the four PDF files are quite large. Simply email me at robinhunt@rcn.com and request the Lost-Foam instruction PDF files.
Your wing looks great! I'm currently (us electric guys use that word a lot...) working on a Lost-Foam Vulcan wing for use in the project model for a Power 15 system that I'm writing about in my MA column. Here are a few photos of that one.
Later - Bob Hunt
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Aha! Your secret is out Doug! Step 15! No wonder!
If I only I had elves working in my shop...
Looks great Doug!
EricV
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Aha! Your secret is out Doug! Step 15! No wonder!
If I only I had elves working in my shop...
Looks great Doug!
EricV
Dang it! I meant to leave that part out.
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Doug,
Does Santa know that you kidnapped one of crew?
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Doug & Bob,
Happy Holiday!
Thanks for the tex and the great photos!
You guys do excellent work, Kudos to you both!
I'm paying close attention and reading up, BTW. H^^
Doug,
Your TE sheeting? Looks like 3/32". Correct or are you using 1/16"?
Charles
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All of the sheeting is 3/32"
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A while back I started a new Riff Raff.
I have been snapping some photos along the way.
1. The list! I build from scratch. Not even a plan. The list helps me stay on track. (Note step 27)
2. The ribs. I cut and sanded ribs to match the lost foam jig from 1/16 balsa I had on hand.
3. Sig wood order. Enough for several planes.
Lookin GOOD !
Randy
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Tonight I installed the BC and the center section sheeting. I put the BC in as high as I could and still have good clearance over the wing gear mounts. The LO is very close as it travels over that rib. I am going to take the sheer webbing out at that location and work it over some with the Dremel to get a little more clearance. Shouldn't be a problem. At 8 oz now, most of that post will come off later when the wing goes into the fuse. That should cut some weight out.
Next up will be tips, slider, and TW box.
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Tonight I installed the BC and the center section sheeting. I put the BC in as high as I could and still have good clearance over the wing gear mounts. The LO is very close as it travels over that rib. I am going to take the sheer webbing out at that location and work it over some with the Dremel to get a little more clearance. Shouldn't be a problem. At 8 oz now, most of that post will come off later when the wing goes into the fuse. That should cut some weight out.
Next up will be tips, slider, and TW box.
Doug
is the high point of the airfoil on that wing in a straight line? or is is swept back? picture looks as if it is a straight taper
Randy
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Your work looks great, Doug! Is everything else going to be like the Riff Raff you are now flying?
Good Luck!
Bill
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Talked to Bob about those half ribs and the shearwebbing and he said "Do both..." H^^
Marcus
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Doug
is the high point of the airfoil on that wing in a straight line? or is is swept back? picture looks as if it is a straight taper
Randy
Randy,
The spar is straight and gives that illusion. But the highpoint sweeps back with the wing.
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Put in the tip weight box today.
The open box looks a little dirty because it is a used one. Cleaned it up, checked glue joints, added any that was needed and installed it.
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Doug,
On the PSP bellcrank do you put the brass over the leadouts and then bend it or do you have a method that keeps the tubing from crimping on the inside of the bends and then feed the cable through it? Those cranks are so thick I can never get a result I'm pleased with.
I aways feel like I add some sharp corners bending the tubing and that replaces one problem with another. Maybe I'll just start using the bushed ones from RSM. I just ordered a $40 spinner, I might as well get a $20 bellcrank to go with it!
Chuck
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Looking at the pictue of the bellcrank, it looks likeDoug does like I do. Chamfer the holes in the bellcrank or bevel them. Using brass or copper I myself run the tubing thru a torch to red hot and let cool. Makes bending the tubint easier. Aso the tubing is just large enough for the cable to go thru. Now I let Doug explain his method.
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Doug,
Nice work!
Like that balsa WB cover. I beat myself up sanding ply.
Next time!
Charles
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Rock on Doug, but the Cutlass is coming for you...
Derek
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Rock on Doug, but the Cutlass is coming for you...
Derek
Things are getting more interesting by the minute... VD~
Marcus
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Things are getting more interesting by the minute... VD~Marcus
Marcus,
You're right!
Doug has a great build going here. I wish I knew what the Riff Raff looked like? :o
Doug,
I just noticed something! You have twice as many "photo hits" as I do over at The LOSER. The "weight box photos," that is?
No idea why, but KUDOS!! H^^
Keep up the good work, obviously, you pay a great deal of attention to detail. H^^
Charles
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Marcus,
You're right!
Doug has a great build going here. I wish I knew what the Riff Raff looked like? :o
Doug,
I just noticed something! You have twice as many "photo hits" as I do over at The LOSER. The "weight box photos," that is?
No idea why, but KUDOS!! H^^
Keep up the good work, obviously, you pay a great deal of attention to detail. H^^
Charles
Maybe because he is a National Champion and an excellent builder. Just guessing here.
Derek
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I'm still not sure why you need a new plane. Last years model worked pretty good! y1 y1 y1
But the new one looks awesome so far! Your instruction list is so important. Sequence is everything in building.!
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Maybe because he is a National Champion and an excellent builder. Just guessing here.Derek
Derek,
I didn't know that.
Thanks for the heads up.
Charles
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Doug,
On the PSP bellcrank do you put the brass over the leadouts and then bend it or do you have a method that keeps the tubing from crimping on the inside of the bends and then feed the cable through it? Those cranks are so thick I can never get a result I'm pleased with.
I aways feel like I add some sharp corners bending the tubing and that replaces one problem with another. Maybe I'll just start using the bushed ones from RSM. I just ordered a $40 spinner, I might as well get a $20 bellcrank to go with it!
Chuck
The BC is an old Windy delrin crank. I heat up 1/16" brass tubing cherry red then let it cool on its own. That makes it nice and soft. I put the LO through the tube then through the crank. Bend by hand. Then work them back and fourth until smooth.
Yeah it is a think one for sure. But the thickness helps fight against and wobble as it wears. But I have pulled them out of planes with 100s and 100s of flight with no play or wear.
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Hi Doug. One question. Your TE shear webs are cut with the grain going with the span. Does it make any difference if they are cut with a vertical grain? I've seen both, done both, but is one better than the other? Yours are much easier to cut and trim to size. Thanks in advance. H^^
The TE sheer webs are there to keep the TE sheeting from sagging. Long grain will work fine for this application. I find the height of what it should be where the TE touches the rib. Then I use a stripper, the balsa kind, and cut some 1/16". I place them in and it levels the TE and supports it.
I also do this at the back end of the TE sheeting prior to installing the actual trailing edge. That way there is no dips at the back that have to be filled.
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I'm still not sure why you need a new plane. Last years model worked pretty good! y1 y1 y1
But the new one looks awesome so far! Your instruction list is so important. Sequence is everything in building.!
The winner has a couple of issues. It's tail heavy. I had to add 1.25 oz of lead under the motor. I plan to move the numbers around a little on the fuse.
And.... the stupid canopy got deformed at the last contest. That repair is going really make me insane!
The current nose is 9" tail is 17 7/8". I am thinking 9 3/4" nose and 18" tail. Maybe it wont hunt so bad inverted.
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Doug
I hope you don't mind my asking, but I got kinda curious...
Is there any specific reason for the 3/32 sheeting?
Thanks.
Marcus
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I use 3/32 sheeting as the 1/16 would sag between ribs or give up over time.
I used 1/16 sheeting on one of my first 60 sized stunters and it lasted about 350-450 flights before the sheeting buckled. Plus the 3/32 is a little more forgiving and you can be a little more aggressive with it.
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Installed the outboard tip today. Looks like total crap. Gonna have to cut it off and start over. AARRGGGHHHH!!
And I had to stop down and install a brushless system in my RC car. Waiting on LIPOs to come in.
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I went back out and built another tip.
I use the Tom Morris method.
(The numbers are the picture numbers, the steps are in the right order)
1. I cut out a plan form frame of the tip shape I want to use. I also cut a rib that matches the last rib on the wing. Then I sand it off about 1/16-3/32 all the way around.
2. I glue the tip shape onto the rib.
3. Next I prepare two pieces of 1/16 sheeting. One for top and one for bottom. The grain will run with the span.
4. Then I wrap the rib and frame with the sheeting. The grain running with the span makes this easy. But, it is VERY important to place those two small triangle pieces from the rib to the frame prior to wrapping the sheeting. They keep things square as you work the sheeting down. Otherwise it WILL pull the rib out of alignment and the tip will not be straight. You cant really see it but the two triangle pieces don't actually touch the sheeting. There is a gap on purpose. In the past I have had them touch for support. But after dope and covering and sanding they create a highpoint and sometimes can even create a crack. I leave them a tad short on purpose to keep from creating that hard spot.
7. Sand off excess. Make the initial rounding of the edges. Check it to make sure it is straight.
5. Weight is good.
6. Install and rough it in. You can see I had to fill it some at the TE. I did as well at the LE. I always use wood to fill the gaps. Even if it is paper sliver I fit in there and hit with the thin CA.
Sorry the pics got out of order. I had to go back and rotate one.
I think this one is a keeper.
Next will be the inboard tip. It is the same except I put the line slider in it. I will show a few pics of that along the way as well.
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I use 3/32 sheeting as the 1/16 would sag between ribs or give up over time.
I used 1/16 sheeting on one of my first 60 sized stunters and it lasted about 350-450 flights before the sheeting buckled. Plus the 3/32 is a little more forgiving and you can be a little more aggressive with it.
Thanks!
Marcus
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Doug,
Can you tell us what gauge leadout wire you are using? Guessing it is .027.
I am using the same bell crank in my Cardinal build right now and am deciding what wire to use.
George
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This airplane has me concerned. Will you be flying in Open or Expert at the Nats this year, Doug?
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This airplane has me concerned. Will you be flying in Open or Expert at the Nats this year, Doug?
I will be working in Open this year.
What concerns do you have?
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Doug,
Can you tell us what gauge leadout wire you are using? Guessing it is .027.
I am using the same bell crank in my Cardinal build right now and am deciding what wire to use.
George
George,
I got the LO wire from Tom Morris a couple of years ago. It is fairly thick and smooth. Honestly, I cant remember the size. Sorry. If I get it I update the post for you.
Doug
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No problem Doug. I am enjoying this thread.
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What concerns do you have?
I am concerned that you flying that airplane could get a humiliating number of points more than I get.
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I am concerned that you flying that airplane could get a humiliating number of points more than I get.
Says Mr. Front Row Impact...
Derek
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I am concerned that you flying that airplane could get a humiliating number of points more than I get.
How many does it take to be humiliating ????? ;D ;D ;D
I don't really think you need worry about being down on points, your dogs always look pretty good
Randy
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Looking good on the ground doesn't pay that well in points compared to other things one's airplane is supposed to do. The latter is my concern.
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Looking good on the ground doesn't pay that well in points compared to other things one's airplane is supposed to do. The latter is my concern.
Agreed.
Derek
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I got back in the shop yesterday and today.
I built the inboard tip and slider.
I use a piece of basswood inserted in the frame as the slider. The slider is incorporated as part of the tip.
1. Tip shape
2. Layout a piece of basswood that will be the slider
3. Drill the holes for the LOs at the proper angle, this way when the LOs exit the wing there is no bind.
4. Tap the holes 4/40
5. Connect the holes with band saw, careful not go through both ends. Then fill the cut end with a sliver of balsa.
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Inboard tip continued.
6. Test fit the nylon 4/40 screw. I hand drill a small hole lengthwise through the nylon screws. The LOs will pass through the screws. To adjust, you unscrew and slide forward or back and screw into the new hole.
7. Build the frame just as the outboard tip I use two support pieces on each side. Sheet with 1/16 balsa grain running with the span, careful to make sure the 1/16 sheeting is touching both the rib and the frame at the same time when I glue it on. That way it wont pull the rib out of shape when I fit it all the way around.
8. Trim away excess and initial sanding of the edge. 10g, the weight is good.
9. Glue it onto the wing sand it out
10. Different angle after sanding
11. Completed wing, 63" span 9.5 oz.
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The TE sheer webs are there to keep the TE sheeting from sagging. Long grain will work fine for this application. I find the height of what it should be where the TE touches the rib. Then I use a stripper, the balsa kind, and cut some 1/16". I place them in and it levels the TE and supports it.
I also do this at the back end of the TE sheeting prior to installing the actual trailing edge. That way there is no dips at the back that have to be filled.
I built a lost foam Geo Bolt wing in 93 and somehow forgot the sheer web at the TE! I found out the hard way how much strength this adds to the TE when I folded the wing two weeks before the Nats. :o n1 Sagging is just a cosmetic reason for sure. DO NOT omit this step with a lost foam with a 1/4 TE high aspect wing!! ::)
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Deleted message...just a fumble fingered quote of my last post.
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Thank you so much for the wing tip slider idea. I have been wracking whats left of this old brain trying to figure out how to do a slider on a Spitfire wingtip....and there it is! H^^
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Flaps.
Yesterday I built the inboard flap.
I use built up flaps 5/16" thick with no taper.
1. Layout the parts. I use 1/16" balsa to cut the sheeting. I strip out 1/16" as well the width of the hinge I will be using, and strip some 1/8" as well.
2. Laying out the flap frame. I build with CA so it is important to keep everything flat on the surface at all times or it will warp as I apply CA during the build. That is why you see the glue bottles laying along the edge. I have also used thick CA and tack glued it to the bench as well in several areas around the edge. That option actually works the best. I keep it up against a straight edge as I work as well. I lay down the 1/8 frame around the outer edge of the sheeting. I lay down the 1/16"wider piece along the LE.
3. Mark where the hinge slots will be.
4. Then I use 1/32" balsa and add another layer along the leading edge leaving blank areas for the hinges. After I have all of the pieces in place I then use a block sander to thin the 1/32" balsa to the thickness of the hinge.
5. I build in the lucky box. I use 1/64 plywood lined with 1/8 balsa for the thickness of the flap horn wire. I leave it a little wide so I can slide it some side to side when I do the final installation. I glue the horn wire into the box at final installation so it is held in place.
6. Lucky box completed.
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Flap continued.
1. I strip and start laying in 1/16 ribs.
2. Finished the ribs.
3. Final Sheeting is added and the weight looks good.
At this stage the flap is more flexible than it will be once it is doped and covered with polyspan. At that point it becomes very stout. The hings slots are build into the LE and the reliefs for the hinge barrels are sanded in.
The outboard flap will be built in the same manner.
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That's very nice!!
Doug, do you round the TE edges or leave them square?
really looking forward to seeing this ship ready!!
Thanks for sharing.
Marcus
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That's very nice!!
Doug, do you round the TE edges or leave them square?
really looking forward to seeing this ship ready!!
Thanks for sharing.
Marcus
I round off the TE. I have heard that squared off will perform better but I do round them off.
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Doug
I like the idea of make your own adjustable lead out guide as you did. My son has one on a carrier plane, but its exposed. The one you built looks really nice, but what do you use as an insert? I guess I'm assuming you have an insert that you pull out of the lead out hole and move to a new hole.
Duke
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I round off the TE. I have heard that squared off will perform better but I do round them off.
That's why I asked... Have heard the same.
Thanks Doug
Marcus
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Duke,
I will get a pic for you tonight showing what I use.
Marcus,
If I had them squared off I know I would get dents in the sharp edges so I just round them off. I wonder how much a difference it really is?
I know I can tell tapered vs non tapered. Non tapered is more effective.
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Here is a close up of how I move the line then anchor the position.
Each of the holes in the slider are threaded with a 4/40 tap. Then I use my drill press and vice to hold a 4/40 nylon screw and drill a hole lengthwise through the screw. Usually about 3/8" is as far as it goes before the bit walks out of one of the side of the screw. But 3/8" is plenty. Then I pass the LO through the screw and put in place. If I need to move unscrew and slide front to back. Then tighten and go fly.
One of the very last things I do before the first flight is add one drop of silicone based chain lube to the LO at the screw and it will be slick as long as you regularly fly it. I have never had them get stiff or not move freely, even after 1500 plus flights over 8 season.
That pic is taken with my phone. Then cropped and zoomed on my phone. Amazing and so simple.
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LiPo batteries and charger finally came in. Now its on a full brushless system from Castle Creations. The ESC is cool it has a tiny cooling fan on top. You can hear it running with the car is sitting still.
This things hauls ass! Now I can really break something!
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Flaps.
Yesterday I built the inboard flap.
I use built up flaps 5/16" thick with no taper.
1. Layout the parts. I use 1/16" balsa to cut the sheeting. I strip out 1/16" as well the width of the hinge I will be using, and strip some 1/8" as well.
2. Laying out the flap frame. I build with CA so it is important to keep everything flat on the surface at all times or it will warp as I apply CA during the build. That is why you see the glue bottles laying along the edge. I have also used thick CA and tack glued it to the bench as well in several areas around the edge. That option actually works the best. I keep it up against a straight edge as I work as well. I lay down the 1/8 frame around the outer edge of the sheeting.
Not that it matters, but doesn't this actually add up to a 1/4" thick flap and not 5/16"?
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Not that it matters, but doesn't this actually add up to a 1/4" thick flap and not 5/16"?
Yeah its 1/4 plus the 1/32 insert for the hinge slots. Its not quite a full 5/16 but just a tad more than 1/4. But it is consistent all the way through. on both flaps.
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Hey Doug have you tried freezing the nylon screws before drilling them? I have even used shorter drill bits that have a tendency to wander while drilling.
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Here is the wing complete minus the flap horn. Span is 63". What you see here weighs 11 oz. Not super light but should be in the ballpark.
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Doug
Looks great!!
What covering are you using?
Marcus
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LiPo batteries and charger finally came in. Now its on a full brushless system from Castle Creations. The ESC is cool it has a tiny cooling fan on top. You can hear it running with the car is sitting still.
This things hauls ass! Now I can really break something!
You suck. That thing is going to kick ass in the Lee's parking lot races.
Derek
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I am going to use polyspan for the open bays and either carbon veil on the wood areas.
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You suck. That thing is going to kick ass in the Lee's parking lot races.
Derek
I already broke part of the front suspension. It's fixed up though. It's almost uncontrollable. :) :) :) :) :)
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There's a guy who used to bring his RC off road car to use the jumps at our local BMX place. He could do backflips with the car, when it survived...
I like RC off roaders, but with IC, the noise you know... I might get one soon. Have a student who has one but doesn't use it.
Maybe I can trade it for some better grades... LL~ LL~ LL~ LL~
Marcus
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Back in the shop over the past few days and I built the stab. For some reason I really enjoy building the stab. I know once you have read this you will think there is are alot of easier ways to get the same result. But, for me, I like to build this structure even though I am sure it is over built. I have an old one that has a large crack in it that can't be used. I keep it around as a template, you can see it in the first few pics. I sure makes it nice when there is no plan available to have a part to work from.
I use a flat stab just over 1/2" thick. Rounded LE and TE. The span is 29", 4 1/2" root and 2 1/2" tip chord. As with the main wing the stab LE shape must be consistent. I mold the LE out of 1/16" balsa. I use a brass tube attached to a piece of wood. Then wet and wrap as normal. Once the mold has dried I sand a trim the piece from the mold buck. When removing the piece it can tend to curve up a bit. Then I attach it to a piece of 3/32" or 1/8" balsa as a backing piece to keep it straight. I attach the backing piece to the table while attaching the mold to it making sure it stays in place until the CA has fully cured. This will insure it stays straight.
Next I build the trailing edge. I like to build in the hinge slots as I build the TE. I start by attaching the straight edge to the table. Then I attach a piece of 1/4" balsa to the table against the straight edge. Then I glue on pieces 1/32" balsa leaving gaps for the hinges. Next pass over the 1/32" balsa with a sanding block to make sure they are same thickness as the hinges. Then glue down another piece of 1/4" balsa. The TE is complete.
Next I layout the LE pieces and complete the frame. From there I trace and cut the center section sheeting for the top and bottom. Next I have to install the ribs in the sheeted area. From there I install what will be cap strips along the top prior to the ribs. I put them in first so I can get them nice flat against the upper edge. Then I flip it over for the rib install and the last of the cap strips. Trim the edges and clean up any rough edges. Next, round the TE.
It's all finished up. The weight is good.
Just for grins I went back and counted the number of pieces used to make this thing, 96. Yes, it's true, I am near the edge of insanity. n~ n~ n~
The stab went together pretty much as planned. The elevators are a different story. I worked for several hours on Sunday and 3 attempts yielded WAY less than desirable results and alot of wasted time and balsa. I day or two off is in order to come back with a clear mind and get them built correctly.
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Continued
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The finished product.
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Thanks for sharing Doug
That's nice!
Marcus
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Beautiful work Doug. What type of glue are you using for the stab and the wing?
Steve Thornton
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Beautiful work Doug. What type of glue are you using for the stab and the wing?
Steve Thornton
Hello Steve,
I use primarily thin and medium CA on the wing, stab, elevators, top and bottom blocks.
Where epoxy is needed, bell crank mount etc.., I use 5 minute.
At the wing joint I have used 5 minute with milled fiberglass mixed in with great results for many years. Where the pipe exits I use Proset epoxy over 6 oz. carbon in that area of the tunnel.
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A little more progress.
I finished up the elevators. I build the leading edge like the trailing edge of the stab matching the hinge slots.
The trailing edge of the elevators is laminated 1/8" balsa, 1/32" carbon blade spar, 1/8" balsa. This makes it very stiff and still it very light weight.
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Continued,
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Great job!
Do you cover or sheet the stab/elev??
Marcus
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I cover the stab/elev with Polyspan and Sig Nitrate dope.
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Doug....Go to the Team Trials this year....You will do well in Poland! The US team needs you!
PLEASE consider this....PLEASE.
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Here is a close up of how I move the line then anchor the position.
Each of the holes in the slider are threaded with a 4/40 tap. Then I use my drill press and vice to hold a 4/40 nylon screw and drill a hole lengthwise through the screw. Usually about 3/8" is as far as it goes before the bit walks out of one of the side of the screw. But 3/8" is plenty. Then I pass the LO through the screw and put in place. If I need to move unscrew and slide front to back. Then tighten and go fly.
One of the very last things I do before the first flight is add one drop of silicone based chain lube to the LO at the screw and it will be slick as long as you regularly fly it. I have never had them get stiff or not move freely, even after 1500 plus flights over 8 season.
That pic is taken with my phone. Then cropped and zoomed on my phone. Amazing and so simple.
Thanks Doug, I really like this idea.
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Doug....Go to the Team Trials this year....You will do well in Poland! The US team needs you!
PLEASE consider this....PLEASE.
We have discussed this a time or two. I plan on flying at the TT this year instead of running it.
Derek
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We have discussed this a time or two. I plan on flying at the TT this year instead of running it.
Derek
I thought you were going to sit out for one more year. That's good to hear.
Have you built a new take apart plane yet?
And Doug, you should really consider the TT's.
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Doug and Derek:
You could hardly find a better endorsement than one from PW.
Go for it!
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Doug....Go to the Team Trials this year....You will do well in Poland! The US team needs you!
PLEASE consider this....PLEASE.
Thanks for the vote of confidence!! I will certainly think about it this year for sure.
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Built the crutch.
Start with 1/2x3/8 maple beams.
Relieve 1/4" in the tank section of the crutch.
Cut out F1 and F2 from 1/8 hard plywood. I would use 1/16 for F2 on a 65 plane but this is a 75 so I decided to stay with the 1/8 for both.
Using 1/16 balsa trace and cut out three pieces that fit the gap between the beams after initial installation. Laminate with medium CA
Install with epoxy between the beams making sure they are even with the top of the beams.
Cut from 1/8 balsa a filler that spans the area between the to of F1 and F2
Epoxy in place and clamp until dry.
Trim and sand the top piece until it is flush with the top of F1 and F2 and on the sides of the beams.
With the top filler piece in place it ties the beams together across the filler pieces. It also creates a nice platform for the crutch to stand on upside down when installing the fuse sides to the crutch.
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Continued
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I thought you were going to sit out for one more year. That's good to hear.
Have you built a new take apart plane yet?
And Doug, you should really consider the TT's.
No I spent all my extra time building a non take-apart plane to save weight. I am happy with the new one it is MUCH lighter than the Matrix. If I were to make the team I would probably build another one but i still have the Dreadnought that flies really well.
Derek
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A naive question...
The 1/4 relieved from the mounts is for adjusting the tank, isn't it??
Marcus
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A naive question...
The 1/4 relieved from the mounts is for adjusting the tank, isn't it??
Marcus
Yes, the plastic 8oz tank will need some room to move up to get the right setting.
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The dremel must have been smokin' grinding all that wood away on the motor mounts!
Whats the deciding factor in the width of your crutch, the width of that 8 oz tank or the width of the 75?
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Built the fuse.
1/8 48x4 balsa for the sides
Cut out needed slots for cowl, wing, and stab per numbers on the sheet
added 1/32 plywood doublers that extend past the wing
Glue the sides to the crutch
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Fuse continued
Add in filler pieces to keep the proper width top and bottom.
I dont start the taper until just after the TE of the wing. I use a straight taper as well. This makes it easy to keep it all straight.
I dont have one of those really cool fuse jigs. With the help of some RC construction techniques I have come up with a cool way to build the back half of the fuse with the taper and keep it even. I measure the distance from where the taper starts, just about even with the TE of the wing, to the back of the fuse. Then I measure the distance across the fuse at the last filler piece and across at the back of the fuse. I usually have it only 1/8" wide at the back.
Then I cut 1/16 balsa in the shape of a triangle using those measurements. From there I flip the fuse upside down and tack glue it to the last cross piece at the start of the taper. I gently pull the two together and tack glue, using thin CA, the fuse sides every couple of inches to the triangle piece as I work my way to the back of the fuse. It is VERY important that I squeeze them together at the same time. If I dont it will pull it out of shape and the taper will not be even all the way back. Once I have tacked it all the way back and I am satisfied with the taper and all is even I go ahead and glue the whole seam on both sides.
Then I flip it over and measure the distance across the fuse inside to inside at 4 separate stations between the trailing edge and stab leading edge. Using a square I mark along the bottom of the fuse at the same spot the I measured at the top. Next I cut 4 1/8x1/4 pieces of balsa per those measurements. At the same stations along the bottom I pull the fuse sides together and install the balsa pieces. I did drop the balsa pieces 1" into the fuse so I will have room for a pipe floor. Next I glue in some vertical balsa and balsa across the inside of the triangle taper piece. These are my "window frame" formers. Just for added support I go ahead and add some cross bracing. This area will eventually get a pipe floor very tightly fit inside the fuse sides.
I do not go back and remove that piece of 1/16 balsa that created the taper. That stays in place. Along with the pipe floor the back section is a box, very strong and twist resistant. Then the 3/32 molded top and bottom blocks are added creating just that much more support.
Using some 1/32 ply I create some access hatches just below the stab TE. These will come in handy should I need to change the push rod length. Usually I end up adding in some down elevator. These hatches make it a snap.
Now I add the tank floor. I use a 1/16 hard plywood installed with 5 minute epoxy mixed with milled fiberglass. The added milled fiberglass makes for some tough glue joints. Once the tank floor is added the front half of the fuse is now a box as well.
If you noticed I kept the motor mount beams full length. I install the nose ring right onto the end of the motor mount beams. I also tie those motor mount beams into the top of the wing once it is installed. I am certain I am overbuilding in some areas but I have found this method to yield a really strong fuse that will resist twisting and give good support to the motor to help create a good solid engine run.
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Continued
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Here is the list now. Making some headway.
On the fuse all I lack is the nose ring install and then initial nose shaping prior to putting in the wing.
During the fuse build I was able to get three coats of 50/50 Sig Nitrate dope on the wing/flaps stab/elevators. I will cover those soon. I like to cover them prior to going into the fuse.
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Is the Chevy truck on your workbench for hauling around the particularly
heavy pieces of balsa?
Later
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Is the Chevy truck on your workbench for hauling around the particularly
heavy pieces of balsa?
Later
HAHAHAHAHA!! I was wondering if anyone would notice that truck on the bench. Max has many of those hot wheels. i think it's a cool one and somehow it ended up on the bench. It has a sport bike in the bed. So I just keep it up there. Who knows where else it will end up next.
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The dremel must have been smokin' grinding all that wood away on the motor mounts!
Whats the deciding factor in the width of your crutch, the width of that 8 oz tank or the width of the 75?
I have done it with the dremel before and it is a beating of the highest order. But now I just use the band saw and it makes quick work of that task.
On this model the width is driven by the tank. I have made them wider in the past and its nice to be able to slant the tank outward for a cleaner shut off. But on this one I just copied the same as the nats plane. The 75 fits in there nice and snug.
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Just wanted to thank you a lot for making this thread, Doug. I'm learning a lot from it. :)
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Hello,
I may have been away from here but I have been living in the shop.
I have made some progress.
I like to cover the wing and stab prior to installation into the fuse. I also cover the flaps and elevators at this time.
I use poly span. The surfaces are all covered with 3 coats of 50/50 sig nitrate. Sanding the last one only.
Next I use about 90% thinner 10% dope mix to apply the ploy span. I apply the thinner mix to the edges of the surface only leaving the middle area dry.
While one wing panel is drying I do the same thing to the adjacent panel. Once I am sure it is dry I bring out the heat gun and shrink out the poly span. You be surprised how much it will shrink and how it will pull out some pretty big wrinkles with ease. BUT if I shrink it before that thinner edge area is really dry the covering will slip inward and wrinkle and will not be able to be straightened back out. This happened to me on the outboard wing top side of course. I went forward and applied thinner mic over the whole panel thinking I could work it back out and get it straight. The slip was too much and it just wouldnt correct itself. No worries though. At this point since it has been attached with mostly thinner I just wet it again with thinner mix and it easily lifts off the panel. I let it dry out over night and redo that panel the next day with no issues. I cover the flaps elevators and stab in the same method. My thought here is that if all the flying surfaces are prepped with the same covering it is that much easier to get a good consistent base for finishing. It has been working out so far.
Once they are shrunk and covered once completely with thinner mix I let them dry for about 2 days. Then I start with mix of 60% dope 40% thinner. I go for 3 coats. I only sand after the last one and I work the edges first. If I have enough dope in the poly span the excess with flake off just like SS does. From there with a used piece of 320 I lightly sand out all the surfaces and the wing. I am careful not to grind on it. I am simply knocking down the dope fuzz. Poly span is not SS or CFV, it is not designed as a filling covering you can sand down flat. When you cut it with sand paper you weaken it and cause the polyester to fuzz up. The fuzzies can be a nightmare. But a drop or two of thin CA or a couple more coats of dope and you can lightly sand them away. Dope will build up on top of the poly span as you go. After 3 coats of the above mix the lightly sanded surfaces are already feeling very uniform and will fill very easily with dope and zinc and final blocking coat of primer.
Next I built a balsa rack to store my wood. I have been meaning to do this for some time, 6 years!
I also took a queue from Derek's finishing thread and built some much needed jigs for my flying surfaces. I used 1x2 and ripped it on my table saw then ran a bolt through them with a wing nut. Now I can keep flaps and elevators on there and they will stay straight while applying dope and paint. Thanks Derek and Eric V for the tips.
Now I am getting ready to install the wing. First thing I do is add alot of support braces in the bottom area that will be cut out and in the areas around them that wont be cut. Its like chopping a car, you need something to keep things straight when you go to cut out a mian part of the structure. Next I cut out the bottom on my band saw and start the initial fits.
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Thanks for the pics and the reasoning. Learn something everyday.
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Man that is a great idea on the control surface jigs,,
I took a peice of particle board, slit a groove in it, and CA my brass tabs into the slit,, but well its only good for ONE airplane,,
I see a project on my horizon
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I have been making some progress.
I have molded the top and bottom blocks.
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Wing install.
I have alot of pictures of the wing install.
I will try to touch on the process but as always pictures are worth a thousand words.
1-2-3. Initial layout and alignment of the fuse on the table. I use medium CA and kicker and glue the fuse to the table. Using kicker it keeps the glue getting too deep into the wood and it pops off table at the end rather easily. I use two squares to make sure the fuse is lined up square with the building surface.
4-5. Initial fit, just the first of what seemed liked 75,000 fits.
6. Using a small square I am able to measure the height of the trailing edge and the depth of the trailing edge off the of the back of the building surface.
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Wing install continued.
After the wing is properly lined up I tack it in place on the top of the wing to the saddle with thin CA using one of those long extensions to reach up under the wing.
7. Initial fit of the bottom section back into the fuse. Using 1/64 plywood shims to fill the gaps.
8. Shims flush along the outside fuse sides. Once installed remove all the cross braces and filler pieces that kept the bottom piece lined up during install.
9. Next using 1/4" balsa I "block" the wing up against F2 using epoxy.
10. Using 1/32 plywood I bridge the back of the seems inside the fuse.
11. Shape the 1/16 plywood C-clips.
12. Install the C-clips.
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Wing Install continued.
It is important to fill any gaps in the wing saddle with wood. They need to fit flush but not create pressure during the install.
14. Using 1/16" and 1/32" balsa you can see the shim line up on the inside of the fuse. I drop some thin CA on the inside.
15. Score the wood along the fuse outside and lift up
16. I am certain not to cut through it, scoring it is plenty.
17. Lift up and it snaps off with ease.
18. 1/8" Plywood pivot block.
19. Hysol 2 part 24 hour epoxy.
20. Hysol application gun makes for a very easy install. The long stem has baffles in it and it mixes the two part epoxy as it is squeezed through for application.
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Derek,
I didn't know that.
Thanks for the heads up.
Charles
HB~> HB~> HB~> HB~> HB~> HB~> HB~> HB~> HB~> HB~>
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Wing Install continued.
21. Hysol applied with applicator, easy as pie.
22. After the epoxy is dry cut the excess pivot flush with the block and attach 1/16" plywood cover.
23. Block the top of wing up against F2 and relieve any excess maple motor mount.
24. Using a protractor I can adjust the total throw of the flap horn and make sure it is equal in both directions.
25-26. Using 5/32 copper tubing over the flap horn it is easier to see the total throw.
27. Flap Horn push rod connected to the horn.
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Stab install.
1. Remove the top of the fuse above the stab cutout and make an initial fit.
2. Using a flat sander make sure the stab is aligned properly, this takes many tries to get correct. But once it is to my satisfaction I take it in place with CA then apply the Hysol. And then place the top section that was removed back into the fuse.
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Doug,
Thanks for showing so much detail. Really enjoying watching your build and learning a lot!
Take care,
Jason
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Doug,
Thanks for showing so much detail. Really enjoying watching your build and learning a lot!
Take care,
Jason
Thanks and you are welcome.
I am glad people are enjoying the thread. #^ #^ #^
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Marcus sent me massage asking about how I am going to mount my engine.
I use standard maple beams. I mount aluminum pads using 6/32 bolts and blind nuts to the beams. Then I tap the pads for 6/32 bolts and mount the motor to the pads.
I have added a couple of pics to show how it works.
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Thanks Doug.
I'd better get back to the drawing board... H^^
Marcus
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Getting more work done.
Push rod is installed.
Linkage at the flaphorn.
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I also installed thepipe floor.
It is importatnt the pipe floor is tight up against the fuse sides. Helps to build a strong box fuse.
I used a light piece of 3/32
First section installed
Second section all the way back just ahead of the tail wheel area
Another view showing the joint.
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I am very surprised you do not drill the holes for the motor before you add the crutch to the sides. I use to do it like yours until a motor mt split. I now drill them and add the spacer. It looks very nice. I was just given one of those fancy fuselage jigs. I wish I had it 30 years ago.
Ed
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Ed,
That's very good to know. I may switch to that. I havent had an issue but if it did I would be pretty mad about it that's for sure.
Thanks
Doug
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Doug,
Thank you very much for posting this informative building process. It is greatly appreciated and I follow every steps joyfully.
I am crossing fingers it will be continued for the painting process as well.
thank you very much
sina
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Thanks Sina! I do plan to show the finishing as well.
Next is the tail wheel.
I fly off a stooge now most of the time. This has to be bullet proof.
1. Test fit the 1/16" Plywood mount.
2. Using 3/32 wire bend a loop and sew it to the mount using SIG wrapping wire. Once satisfied with the mounting of the 3/32 wire I glue it with 5 minute epoxy.
3-4. Using epoxy I glue in the tail wheel mount and 1/8x1/8 balsa along each side creating more gluing surface attached to both the tail wheel mount and the fuse sides.
5. Slip in some 1/16 balsa to act kind of like a cap.
The other end where the wheel is there is small angle in the corner so the clip holding the model will pull against the wire and not the mounted wheel.
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Next I seal the pipe floor, bottom of the wing, tank and engine compartment.
I use 5 minute epoxy thinned with alcohol until the consistency is the same. Brush it on with an epoxy brush.
Once its dry the wood is sealed and shouldn't absorb any oil. At least it should be resistant.
Trim and test fit the bottom block/pipe tunnel.
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Building the gear.
I use wing gear. I use 1/8 wire for the gear.
1. Initial gear bending.
2. I trace out what I think are cool looking gear doors on 1/64 plywood.
3. Laminate the first one cross grain to the 1/64 plywood using medium CA. It is stronger than just using 1/32 plywood.
4. Gear doors complete.
5. I need to attach the gear doors to the wire. I flatten one side of 5/16 dowel.
6. Using a dremel I groove the dowel.
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Gear Continued,
7. Next I use my dremel and rough sanding drum and rough the gear wire. It removes any residue from the wire. Glue will stick to the surface no problem once it is roughed out. Using 5 minute epoxy I fill the groove a little and slide the wire into the groove then place on the gear door. Using a speed square I make sure the wire dries 90 degrees to the gear door.
8. Once they are dry I use some 1/8 balsa scrap to make some sort of small shock looking actuator. You can see I left a gap in there to also give the appearance of a shock.
9. Complete and in the plane/
10. The finished product will look something like this. The dressing on each end is an aluminum tube cut to fit.
I learned the method of fake shocks from Windy on the spitfire series. I modified the attachment using a grooved dowel.
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Very cool Doug.
Thanks for posting!!
Marcus
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Doug Some very nice idea's. I like the gear. I used that Motor mounting method for a few years so I could change motors. Not sure why I stoped. I think I will go back to it. How thick is the pad??
Ed
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Ed,
The pad is 3/16" thick.
Doug
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More progress.
The bottom blocks are on. I used molded 3/32" balsa.
When I remove the wraps from the molds I sand the blocks before pulling them off the mold. It's easy to get a real nice surface when they are on the mold.
I thin down some 5 minute epoxy with alcohol and sealed the inside of the tunnel before I mount it to the plane. I also seal the tank area, engine bay, pipe valley at this point.
Next I slip it back on the mold and trim the edges off even with the bottom of the mold.
Then I take my time using a long block and sand the edges where the mold will lay nice and flat on the table and then final fit sand it to where it will lay nice and flat on the plane with no pressure to hold it in place. You never want to have to apply much more than a resting hand amount of pressure when gluing the mold onto the fuse. If you do apply alot of pressure to put it in place it will constantly be under pressure trying to twist away from its attachement and could warp your fuse. You will know this when your stab no longer lines up with the wing....ask me how I know this...... Using thin CA I tack the mold in place, each corner first then work my way back alog the sides. Four or five dots per side. Once satisfied I hold the plane vertical and apply thin CA from the front on the seam. It runs down the joint. Once it kicks off I apply a little medium as well in the same manner. Probably overkill. Then I sand out the seams on the outside with the long block. Then fill any gaps.
1. Block tacked in place.
2. Glued from the inside. The block looks a little off on the back end exit area, most of that is trimmed away for the pipe exit. Even though the shell is only 3/32" think there is still alot of shaping to do. On on the front side I will install 1/64" ply flat about 1/2" wide in the lip to help protect it and keep the shape.
3. Finished. The rear block is installed as well in this picture. It is installed in the same manner. The back is open during install and I can run some CA in from there. But since it is very had to see if it is covered I will usually run some thin on the
outside of this seam as well. I just have to make sure I sand it out.
4. I just think this is a funny pic.
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Time for the top block. I thought I would show a little more detail about how I prepare and attach the blocks.
1. Check the controls one last time and blow out any dust that has built up inside.
2. Molded shells still under wraps.
3. Showing the overlap of the shell onto the bottom of the mold buck.
4. Initial trimming of the bottom of the shell. I also sand out any marks left on the wood from the wraps. You can usually see the weave for the fabric left in the wood.
5. Pulled off the block. You can see the initial trimming around the front that was done during the molding to get it to go around the nose section.
6. Sanding the edge nice and flat with the block/t-bar sander.
7. Mold is longer than needed on purpose.
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Continued,
8. Trim the mold to length. I base this on where the back will meet up with the turtle deck. On this model it is right where the fuse taper begins.
9. Large pie shaped piece out of the front is trimmed up for final joining.
10. Joined the two edges together with thin CA. Flipped upside down and prepare to add in some wood under the nose. I like to add in a piece of 1/16 under the far forward nose section of the shell. Helps with a larger gluing surface and additional wood under in case I go through on the initial shaping.
11. I put some medium CA in the shell and press in some 1/16” with the grain going the same direction. I am sure to slightly curve the piece first so the inner part touches the shell first and work it out ward from there. The glue goes off fast so if I press in from the edges it won’t get up into the shell before it kicks there will be spot where it isn’t attached, right where I need it the most.
12. Making sure I have the fit I want with the shell up against the nose ring I start working from the back using medium CA and gluing each side down a little at a time as I work forward. I lift it up ever so slightly and put in several inches of glue and just work my way towards the nose. I start from the back because it is easier to keep it lined up on the fuse sides. There will be overhang on the side at the front to the alignment there is not as critical.
13. All glued down and ready for initial shaping.
14. You can see where that filler piece comes in handy….how do you think I learned that one….??
15. Initial shaping done. I may try to knock it down a little more to get a more subtle dive into the spinner but there isn’t much past that high point. I should have made my filler piece a little longer, that’s always the case by the way. HAHAHAHAAHAHAHAHA! Sometimes I learn and other times, not so much.
16. Here it is with the turtle deck on as well.
This plane is about 2” longer than the last one built with these molds, last year’s model. I made a few adjustments along the way as this will be a 75 model. The turtle deck mold came out a little short in length and in height. I added 3/8” strip of 3/32 to the bottom on each side of the mold. Then trimmed and sanded and attached it in the same manner as the front. Then about 2” in the back was open and I used a small block to fill in the space. Not a big deal really and seam is behind the back of the stab. I think it turned out pretty good. These blocks were added in one building session about 3 hours. It can be tedious but it turns out pretty good and the less balsa dust I breath the better.
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Trying out the rudder.
Just pinned in place as I make sure I have the right size. I think this is a little too big. I will spend some more time getting the right size before I glue it in place.
As you see it here it weighs 28 oz. I really have to watch it from here on out. Still have canopy, stab fillers to the fuse sides, fair in the flaps to the fuse sides, cut the pipe exit and reinforce it, cowl, stab plates, cover fuse, and fillets. Feels like I still have 10,000 miles to go.
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Doug where did you get your epoxy gun and tubes at?
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Hello Brad,
My brother ordered that for me. When he gets back in town I will let you know where he got it.
Thanks
Doug
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Have you got the paint scheme worked out?
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Have you got the paint scheme worked out?
I am conjuring up some new ideas of pain and torture. Of course checkerboards and fades and curves will be in there for sure.... Maybe a slight change in color choices too.
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Doug, are you going to fit elevator tip plates? If so what material do you use?
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Brad,
The glue, glue gun, and extra tips came from McMaster-Carr.
http://www.mcmaster.com/#loctite-hysol/=mczrio
I used the slow drying glue part# "9462™ Impact Resistant—Thick for use on vertical surfaces. Has good shear and peel strength and resists high temperatures and shock. Also bonds wood."
Curare,
I will be adding the tip plates to the stab. That is one of the very last things I do so I dont knock them off durig the build. I use 3/32" balsa sanded flat so it is a little thicker than 1/16". Then dope and cover with polyspan or carbon veil. My brother uses 1/16" lined with with 1/64 ply on one side. I may do that as it makes them alot tougher.
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A little more progress this weekend.
I trimmed a little of the rudder and fit it one more time and then went for it.
I use an airfoiled rudder. Nothing special just sand a nice curve into it.
I also fill the back of the fuse to match flush with the fuse and then sand out smooth.
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Next I worked on the pipe exit.
Where the rear bottom mold meets the front bottom mold I use a piece of blasa in the joint. I forgot to get a pic of it sanded out smooth but I did get back to it and clean it up. I learned early on a lng time ago a butt joint with wood across it on the inside was not enough to hold. That joint has to be strong or it will crack very early in the planes life. This portion of the fuse is under a lot of stress and the tail is always trying to twist. It is important to build all the joints as tight as possible. I add in the filler balsa with thin CA. I will glass it on the inside.
The pipe just barely fits but it is not touching any part of the of the plane and the exit is plenty large enough to get the incoming air from the cowl out across the hot pipe keeping it cool.
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Looks killer, I have always liked the way you do the molded bottom block. I just leave the whole tunnel open on the bottom.
Derek
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Completed the fillers between the elevators and the fuse.
Then got the flaps flush with the sides of the fuse.
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Canopy time.
I cant stand the sun melting my canopies. I usually pretty good about keeping them safe. But on my last plane I have a small indention from the sun at 8:45 in the morning at our last contest. AARRGGGGHHHH!!!
1. I thought about starting out with a blue canopy this time and going silver over it.
2. Talked some with Eric V, Derek B, and Steve F and thought I would try a wood canopy. They said it would be lighter too.... To be honest I wasnt sure it would be.... Inital block, looks great huh?
3. Side of the belt sander made initail carve out a snap!
4. Getting closer.
5. Almost Done.
6. 16g
7. 2g
8. Finished. Looks like it should.
Next up is the cowl.
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The list is getting shorter and shorter...
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Anybody else notice the little silver truck at bottom of the checklist on the bench?
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Great thread...
Got a lot from here.
thanks Doug...
Ship looks better and better!!
Marcus
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Anybody else notice the little silver truck at bottom of the checklist on the bench?
Yep, that little truck has been on the bench through thick and thin on this build. I think, my son 5, put it up there at the start. It's brought me good luck so far.... It's not going anywhere until this is over.
He saw it the other day and asked if I was still using it, like he was thinking he wanted it back. I said I will be done with it soon. He smiled and said "Ok." Than ran off to cause mayhem throughout the backyard!!
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When everything on the checklist is done, you put the plane in the little truck for transport to the field and go fly. n~ n~
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Time for the cowl.
I really like balsa cowls and all the cool curves and vents you make in them but I always figure out a way to damage them or the fuel eats away the mounts and it is a constant battle to keep them in good condition.
I couple of years ago I learned the foam plug covered in glass method and I have had good results so far. It creates a light weight semi flexible fuel proof part.
1. Create a base using 1/32 plywood for the foam plug. This becomes the part of the cowl that is up against the plane when the cowl is mounted.
2. Mount the base to the plane in the same manner as I will once the cowl is complete. I have embedded brass inserts at the front and the washers are glued to the base. I make the base a little bit smaller than the fuse all the way around. The leave a little room for the layers of glass to build up and become flush with the fuse.
3. Protect the fuse from the long sanding block I will be using to shape the part.
4. Add the foam. I use the green foam you find at arts and crafts stores used for fake plants. I epoxy it to the base with 5 minute.
5. Initial shaping is done with a zona saw. This stuff is about as soft as cold butter. It is very easy to dent it or gouge it. I have to be very careful when working with it.
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If your gonna have this ready for the NATS you better get humppen! Looks good.
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6. I switch to a long sanding block and work the part down to match the fuse shape. I am careful to work my way from the back of the model forward so as not to make the front of the cowl smaller than the back. The style here is the cowl is just an extension of the fuse and there is no curve to it.
7. Using a sharpie I draw out what I want the profile to look like.
8. Back to the zona saw and I cut it out. Again I have to be very careful not to squeeze the part when handling it.
9. I have removed the plug from the plane and shaped it down to match the base. I glue a large piece of scrap balsa to the base.
10. Put in my vise and layout the strips of glass and get ready to cover the plug. Mix up some really nasty dark looking ProSet epoxy. Its old but it still dries hard as a rock!
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If your gonna have this ready for the NATS you better get humppen! Looks good.
Once upon a time I thought I might have it ready for the Nats but now I am not thinking that will happen.
As long as the wing keeps blowing I will just keep working on it and see where I end up.
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11. Apply the epoxy and glass with an epoxy brush. I wear latex gloves and use my fingers my fingers to lightly press around the base making sure the glass is making contact all the way around.
12. Another view.
13. After it cures over night I trim away the excess and remove the balsa scrap from the base.
14. Initial fit to the fuse.
15. Initial sanding, using 80-100 grit paper. It is apparent I have made it just a tad too small. I am not going to try to sand the bottom block down to it. Its only 3/32 and I don’t want it any thinner.
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16. Glue the scrap balsa back to the base and back into the vise it goes. I wasn’t real happy with the surface either. I had used what appears to be 4oz cloth. It would take a lot of filler to get it smooth. I had run out of .75 oz and thought I could make it work. I made a quick trip to the LHS and found some .75 oz cloth. I dug around my shop some more and found some 2 oz. Here I have added a layer of 2 oz cloth and several layers of .75 oz cloth. Since the plug is already protected from the initial layers I can really work the cloth our smooth with my hand after the initial application of epoxy and glass.
17. The next day it is ready to be trimmed and sanded. Initial fit looks much better this time and the surface is my more acceptable as well. I find it best to do as much surface sanding as I can before I remove the base and the foam. The part is much stronger and doesn't flex under sanding pressure so I get the surface much flatter.
18. Cutting away the base exposes the foam to be removed.
19. Using the zona saw I cut it all away as best as I can. I know others use foam that can be melted away with solvents but this type is some kind of super nuclear war resistant foam. I have tried to melt it with, lacquer thinner, Sig dope thinner, PPG base maker, reducer, gasoline, mineral spirits, acetone, and anything else I had around the shop. Nothing worked. But I did find on my tests that some of those solvents would damage the part a little making the inner surface a little sticky. But the foam just sat there as if nothing had happened. So, I just cut it away over the trashcan. Simple enough and takes just a few minutes for the initial removal. Then I finish getting it all out with the dremel. I stand next to a fan to keep the dust moving out of the shop.
20. The foam is just about all cleaned out.
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21. All cleaned out, nothing left but the edge of the original base and the glass.
22. Weighs 5/8 oz. It is fuel proof too. It will get clear inside as well.
23. The PA 75 is hiding.
24. Trimmed away the front for proper cooling.
25. The front mounts are completed.
I still have a little ways to go on it. Rear mounts and some filler wood around the front to give it some thickness at the edges. I hope to get that done today.
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You need a bigger engine....
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Very cool approach.
I might try it soon....
Marcus
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Pat Johnston does this. Carve the cowl from blue or gray foam. Fit it then glass it. Then use acetone to remove the foam leaving the fiberglass cowl behind. Cool technique.
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Same way I do my cowls too, I use Urethane foam, it will not melt with solvents either,, you have to dig it out, but it works much easier,,
the blue , pink or white foam will melt,,
That green foam looks like Urethane florists foam for doing plant arrangments
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So how much smaller do you make the base and rest of plug to allow for the wall thickness of finished cowl.
Sounds like you normally make the glass layup from multiple layers of .75oz, how many layers is sufficient ?
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So how much smaller do you make the base and rest of plug to allow for the wall thickness of finished cowl.
Sounds like you normally make the glass layup from multiple layers of .75oz, how many layers is sufficient ?
Hello Allan,
The glass is actually pretty thin. If you make the base smaller by 1/64-1/32 it should be enough to compensate for the layer of glass. If you can manage just 1/64 it should be right on the money. This one initially came out too small. The base only needs to be smaller by just a tad but has to be uniform all the way around.
I normally use 1 layer of 6oz for the strength, then a layer of 2 oz, then a layer of .75 oz for the finish. I also add multiple strips around the mouth area on the corners and all over the nose ring area. But I always had some thin areas and had to be careful of sanding through it at the edges. In the future I will probably go with 3 layers of 2 oz, let it cure then come back with 3 layers of .75 oz. I liked how it came out doing it in two stages. After the initial setup had dried I was able to insert some balsa around the mouth area in those corners and the second layup really added some overall strength in those areas and on the whole part.
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Now I need to complete the rear mounts.
1. I use two pieces of arrow shaft glued in with epoxy mixed with milled fiberglass right at the tank floor/fuse joint. Milled fiberglass in 5 minute epoxy makes for some tough stuff. And since the cowl gets removed many times over its life it’s important that it can take a beating. Plus it kicks off in about 3 minutes instead of 5!
2. Insert two pieces of wooden dowel.
3. Place the cowl on the model and mark the inside where the dowels will be attached. Having a big open mouth makes working inside the part pretty easy.
4. Add balsa to the cowl at the marks. I intentionally make the balsa pieces to think and sand them down to where they are touching the dowels at this point. It takes several fits to get the outside perfectly flush with the fuse and the dowels just resting up against the balsa mounts.
5. Once I am happy with the fit. I drip a little epoxy onto the joint between the dowel and the mount. While this dries I replace the broken blade grips on my helicopter. Helicopters and fences don't get along to well. This gives the epoxy ample time to set. I do this with the cowl on the plane and the front mounting screws are in place and tight. This is how the cowl will be sitting in the final position.
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6. Trim away any excess balsa and add more epoxy with milled fiberglass to the dowel/mount joint.
7. Side view. Round the dowel ends just a tad as the cowl will need to lift up just a tiny bit to go over the needle as it slides off the model.
8. Inside view once it is in place on the model.
9. Mounts are complete and hidden for the most part. The scale still says 5/8 oz. I will come back and add in a piece of 3/32 balsa in the mouth of the cowl to give it a nice uniform thickness across that front edge. Since that is an exposed edge it looks nicer, to me anyways, to have a little thickness there like you would see if it were a balsa cowl. I like this method because the cowl is held in place from two different angles. The part slides in place from the front, spinner has to be off to get it on the model. Then the screws go in vertical.
10. Almost a complete model.
I will come back and add in a ½” wide piece of 1/64 ply flush with the front of the bottom block where it meets the cowl. Not on the edge but actually inside the block. This helps it keep shape and give it strength. I will add a small drain hole, lined with an aluminum tube, at the front of the bottom block and the rear of the cowl as well. I had a leaky tank in my 2009 model and I didn’t know it right away, PA still ran flawless, and several flights was all it took to soak that front lip of the bottom block. Raw 15% nitro sitting inside the fuse for a few days can do some serious damage. I will come back in and seal the engine bay and pipe tunnel again with thinned epoxy.
I have only the fin between the rudder and the turtle deck and it will be done. I can see light at the end of the build tunnel. I add the fillets after I cover the wood so I count them in the finish. What you see here weighs 29.75 oz. That puts me about 1.75 oz over my target. I plan to fill mostly with dope so I am hoping to make some of that back. Just for reference from the tip of the rudder to the nose ring it is 46.75” long. The stab span is 29” and the wing span is 63”.
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You need a bigger engine....
hmmmmmmmmm..... Now that's a good idea. I thought I heard something years ago about a PA 82?? Am I mistaken?? hmmmmm,,,, I wonder if there are any hiding is the Southeast... ;D ;D ;D
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That is more or less what I do. I usually use carbon dowel and aluminum tubing but the same idea.
Nice work.
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Wonderful thread Doug. I'm learning from it and getting inspiration to build. Been practicing any to defend your title? Hope to see y'all at the next Dallas contest.
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The cowl is complete.
I added in some balsa to the front edge and put in the Nicad hole.
I added a 1/64 ply stip inside the front of the bottom block. I also glassed the joint at the opening of the pipe tunnel.
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I added the small fin between the rudder and the canopy.
I as of 5/27/2013 I am calling the build portion of this plane completed. There is more to do but that will get taken care of during the finishing.
Max likes it too.
Last years plane sits beside it taunting the new rookie.
Oh yeah, it weighs 30 oz.
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Lookin' real good Doug!
Been following this from the first piece of wood cut, and I've definitely learned some good stuff to incorporate on my next plane whenever that may be.
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Oh yeah, it weighs 30 oz.
How does that compare to the other one at this stage ?
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How does that compare to the other one at this stage ?
If I remember correctly the other one was 29oz at this stage. Then there was a big problem with the spray gun and I had to reprimer it and ended up adding a bunch of weight to it.
I am going to be using alot of dope filler this time and less primer to see if I can keep the weight down.
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Hope it's okay to bump this one. I'm about a year off from starting to build my first full fuselage plane, probably an Oriental with a glow engine. So I've started keeping an eye out for threads that would make good tutorials for me to bookmark and read. It will be a kit, so much simpler in many ways, but this still looks like a good one for the book. I've built many profile planes, I'm good at that and they look pretty and fly well, but it's time for me to graduate to the next level. I'll start a build thread when the time comes.
Reading, researching, and learning.
Rusty