Author Topic: MORE T-REX (pics added) (Read 5596 times)

Greg L Bahrman · « **on:** December 17, 2009, 07:06:33 PM »

First picture...I found that if I picked at the glue with a flat blade and get a little edge to come up I could grab it with my needle nose pliers and remove it. The glue seems to be only on the surface and not in the joint. So after pulling it up I ran some CA in the joint and followed up with some tri-stock in the joint for added strength. Probably not needed but it's what I did.
My T-rex was a proto-type and it had soft balsa where the cowl screws are so I cut some little 1/2 x 1/2 x 1/8 ply and put it where the screws are so that the wood would not smash every time you tighten the cowl screws.
After cuttling slots in the cowl for air cooling air to pass thru I found that it weak'nd it so I added a small 3/8 X 1/8 stiffener to the cowl as shown, seemed to help. Having fun......

Greg L Bahrman · « **Reply #1 on:** December 19, 2009, 10:24:10 PM »

Engine mounted.... Removed canopy glue and re-did fillet.... Former in front of wing plugged....I mounted the motor and then decided I didn't like it so I redid the mount and the hole for the head....Happy now....Tongue muffler and venturi by Scott Riese....The fuse is so wide that some mufflers both tongue and tube will not clear the side of the fuse so don't forget to check it....As you can see this one from Scott clears just fine.

John Tate · « **Reply #2 on:** December 20, 2009, 08:59:52 AM »

Greg.
What did you use for the fillet material around the canopy?

John Tate

Greg L Bahrman · « **Reply #3 on:** December 20, 2009, 09:22:35 AM »

Hi John,
It's a 2 part epoxy filler called "Super-Fil" from Aircraft Spruce. I bought it on-line. It's light and sands pretty good, not to hard, although it is harder than the balsa so some care needs to be taken when sanding.

Dick Pacini · « **Reply #4 on:** December 20, 2009, 10:02:10 AM »

I have seen that cradle during my search for jigs, but I have lost track of what brand it is and who sells it.

Greg L Bahrman · « **Reply #5 on:** December 20, 2009, 10:41:08 AM »

Hi Dick,
Robart part number 402......http://www.robart.com/Tools.aspx

Steve Helmick · « **Reply #6 on:** December 20, 2009, 04:09:08 PM »

That Robart cradle is available from Tower. As is the Ernst cradle, which I have and rather like. Been thinking about getting a second one, to haul along to the field, actually. The Ernst unit is molded plastic uprights, with a molded plastic tool tray for a base. They give you some foam stuff to put in the yokes. About $11...a nice unit. I'd be worried about the molded styrofoam disolving from fuel residue and sticking to the paint...same could be said for the foam weather stripping that comes with the Ernst cradle, I suppose, but it hasn't proved to be a problem.

Steve

Bradley Walker · « **Reply #7 on:** December 21, 2009, 11:23:11 AM »

I removed the SLC from the noses of all of mine that used IC engines. Then I used one layer of 3/4" glass.

Looks nice BTW.

Make sure to check the line slider.

Greg L Bahrman · « **Reply #8 on:** December 21, 2009, 07:31:49 PM »

Thanks Brad
.......Needle done, there always a pain.....At least I put it on the correct side this time......

john e. holliday · « **Reply #9 on:** December 22, 2009, 08:50:27 AM »

Amazing what has to be done to the ARF/ARC type plane. Still saves a lot of construction time. Great work on the T-Rex. Have dropped hints for Christmas, but as usual I will have to get my own present. MERRY CHRISTMAS

Greg L Bahrman · « **Reply #10 on:** December 22, 2009, 11:04:21 AM »

Hi Doc,
About the work on an ARC/ARF I know what you mean. I guess maybe I am a little to anal about the whole thing. A lot of people just slap them together and go fly. Meanwhile I at home still fixing this and that. Like the needle hole. I put a piece of arrow shaft in the hole but its not necessary, a little CA on the edges of the hole and it would be fine. I am having a good time and enjoy the work but it is not always necessary. In the passed I built a Top Flite Nobler ARF and it turned out to be one of my best flying planes. I stripped it and made new wing tips and added adjustable leadouts, Rounded the leading edge, laminated the flaps, 4 in. bellcrank, Tom Morris controls, etc. etc. I was really surprised because it flew really nice. So while I'm having a good time with this project much of what I do is really not necessary and should not be construed as a must do for the T-Rex. It's just what I did in the process of having a good time. Grins

Bill Barber · « **Reply #11 on:** December 22, 2009, 11:57:18 AM »

Greg and I bought our T-Res's together , his an ARC and mine an ARF . Just starting on mine , but seeing the level of Greg's work makes me more careful with my work. Might have a problem with my ST .60 tube muffler not extending out of the cowl , may need a tongue muffler .
Bill Barber

Bradley Walker · « **Reply #12 on:** December 22, 2009, 12:21:41 PM »

Quote from: Bill Barber on December 22, 2009, 11:57:18 AM

Greg and I bought our T-Res's together , his an ARC and mine an ARF . Just starting on mine , but seeing the level of Greg's work makes me more careful with my work. Might have a problem with my ST .60 tube muffler not extending out of the cowl , may need a tongue muffler .
Bill Barber

Randy has mufflers that are long extension.

Bill Barber · « **Reply #13 on:** December 22, 2009, 12:42:10 PM »

My St.60 is an old one without muffler ears , have a strap-on muffler . Will ask Randy if he has extension for a strap-on muffler .
Bill

Greg L Bahrman · « **Reply #14 on:** December 23, 2009, 12:52:02 PM »

I finished putting diagonal braces in the elevators for torsional stiffness and I lined the hole for the head and the muffler exit with thin plywood (per Claudio Chacon)

Bradley Walker · « **Reply #15 on:** December 23, 2009, 01:00:04 PM »

Nice.

Do you think those little angled braces make a difference? Might be good for the next run.

Greg L Bahrman · « **Reply #16 on:** December 23, 2009, 03:57:46 PM »

<Nice.
Do you think those little angled braces make a difference? Might be good for the next run.>

Hi Brad,
Yes they do make a difference.......BUT......It's a lot of work for a small gain, whether done by the manufacturer or the customer........ I would just stick with your original logic you used on the stab for stiffeness. If the elevators were sheeted they would be great. For some reason mine are really light so I added the extra structure. My stab and the elevators weigh only 2 1/8 oz. which I think is really good for a stab and elevator that is 24 inches long. If I get another T-Rex and the wood is as light as this one, I think I would just sheet the elevators. It might be a smiggen heavier but it would be stiff and straight.......OH and I forgot to mention. After I was done glueing all the braces in place. I brushed about 3 coats of nitrate on everything inside and out making sure every braces got coated 100%. When dry it also adds to the stiffness. I suspect by the time I get the elevators covered with silkspan they will be just fine...... IMHO

Greg L Bahrman · « **Reply #17 on:** December 28, 2009, 02:50:09 PM »

Tank Mount

Douglas Ames · « **Reply #18 on:** December 28, 2009, 04:11:21 PM »

Tank mount looks great, but I'd go with more tension (more rubber bands) Lots of G force with a full tank!
...and as you know, castor oil and Father time aren't kind to rubber bands.

Claudio Chacon · « **Reply #19 on:** December 29, 2009, 04:52:39 AM »

Hi Greg,
I like your work, really nice and clean.
Very clever tank hold down system.

Are you going to do a monocoat job or a traditional dope/tissue finishing?

Cheers,
Claudio.

Greg L Bahrman · « **Reply #20 on:** December 29, 2009, 07:09:07 PM »

Quote from: Claudio Chacon on December 29, 2009, 04:52:39 AM

Are you going to do a monocoat job or a traditional dope/tissue finishing?

Thanks for the kind words Claudio.
Not sure yet, but I think I will do the fuse with Klass Kote and the wing in Monocoat. So far Klass Kote has been good to me and I want to continue to learn how to use it. I have done one plane in Klass Kote and this will be the second. Pic attached

Steve Helmick · « **Reply #21 on:** December 30, 2009, 10:36:22 PM »

Quote from: Douglas Ames on December 28, 2009, 04:11:21 PM

Tank mount looks great, but I'd go with more tension (more rubber bands) Lots of G force with a full tank!
...and as you know, castor oil and Father time aren't kind to rubber bands.

I'd guess that Greg will cinch up the rubber bands or change to neoprene O-rings for the finished installation.

Steve

Bradley Walker · « **Reply #22 on:** December 31, 2009, 09:05:57 AM »

Quote from: Steve Helmick on December 30, 2009, 10:36:22 PM

I'd guess that Greg will cinch up the rubber bands or change to neoprene O-rings for the finished installation. Steve

Use the little velcro straps you can get at the hobby shop.

One thing... you will like it much better if you cant the tank at least 1/4". 1/2" of cant is even better. It will shut off like a kill switch.

Greg L Bahrman · « **Reply #23 on:** January 01, 2010, 02:32:42 PM »

At first glance you probably don't see anything different.....I decided to go with an adjustable rudder, the stock rudder is a straight sheet and sits on top of the fuse......The last plane I built did not have an adjustable rudder and it was always light on the lines even though I airfoiled the rudder. Apparently it was not straight (my fault) but it looked straight. I cut it off and added the adjustable rudder with a couple of degrees of offset and now it has good tension everywhere........On the T-Rex I made a vertical cut removing some of the fuse and made a new rudder to go to the bottom of the fuse and will add an adjustment link. I also hollowed all the solid blocks in the tail area. In the last picture you can see the plugs I put in after drilling the front radiused blocks to lighten them....I appreciate all your comments.....Still having fun.....

Bob Reeves · « **Reply #24 on:** January 04, 2010, 02:36:56 PM »

Think I'll steal your rudder idea, I also like to be able to tweak it, just in case.

Greg L Bahrman · « **Reply #25 on:** January 04, 2010, 07:24:35 PM »

Threaded rod, a couple of clevises and tabs made from 1/16 G10 epoxy fiberglass sheet. Tabs could be made from plywood........For this basically static application I like to use CA hinges. I would not use them anywhere else.

Greg L Bahrman · « **Reply #26 on:** January 05, 2010, 02:10:07 PM »

Added 1/16 plywood fuse stiffeners behind wing and against rear wing former. It is added to make a continuation of the existing ply doublers. I'm not sure it's needed if the bottom fuse insert is put in correctly and tight. Won't hurt anything. The first picture shows the new doubler. The second picture shows the location of the double, it goes on the inside hard against the former in the shown location on both sides. Shown on the outside for reference only. The third picture shows the doubler located on the inside. The holes are not for lightning, they are for glue (CA) access. It's important that the new doubler is tight up againt the former and glued to it. I put a couple of pieces of tri-stock to strenghten the joint after I read Steves flight report. Kind of makes me feel good about all I have done so far.

Bradley Walker · « **Reply #27 on:** January 05, 2010, 04:46:50 PM »

Quote from: Greg L Bahrman on January 05, 2010, 02:10:07 PM

Added 1/16 plywood fuse stiffeners behind wing and against rear wing former.

Perfect. That is the fix. Very nicely done.

I saturated the one I am building with CA on the inside aft of the canopy. In front and behind the former at the rear of the wing. This will make the wood rock hard for about 6 inches and let the stress move from that former. The one i have does not have punk wood in that area, but it only took a few seconds to make sure the area was strong.

Greg L Bahrman · « **Reply #28 on:** January 09, 2010, 07:21:32 PM »

I was not happy with my elevators, they warped when I clear doped them and I could not get them to stay straight so I made new ones and their straight and a lot stiffer. I got the tail feathers covered with silkspan with 3 coats of clear and sanded. They are not glued in place yet and I will not do that until the wing is in place. Yeah, got to work on the wing next. I added a fitting to the muffler for tank pressure and a tube thru the fuse that goes to the tank.......Still having fun!!!

Ron Merrill · « **Reply #29 on:** January 10, 2010, 09:20:43 AM »

Greg, wish i could work with my shop door open. Not even in Texas.

Ron.

Greg L Bahrman · « **Reply #30 on:** January 10, 2010, 12:39:30 PM »

Hi Ron,
Yeah I opened the door while I was clear dopeing the tail feathers. Nice to be able to put a fan up to blow the fumes out. Yuk

Douglas Ames · « **Reply #31 on:** January 10, 2010, 05:05:00 PM »

Quote from: Greg L Bahrman on January 05, 2010, 02:10:07 PM

The holes are not for lightning, they are for glue (CA) access.

What an outstanding idea. CA is always lighter than epxoy anyway.

Greg L Bahrman · « **Reply #32 on:** January 23, 2010, 04:05:22 PM »

I have been working on the wing. It was not as straight as I wanted so I clamped it down to a 1 in. tooling plate. First I sprayed it with water inside and out and when it was dry I added some structure to hold it in place, it also added some stiffeness to the wing. I also made new stiffer flaps. I added shear webs to the trailing edge, as someone already mentioned the wing is hard to handle without breaking the trailing edge or a rib or two. It always makes your heart sink when you hear the wood crack when it's covered and a stranger is launching your plane. Next will be to put the controls in and bond the 2 halves together before covering. I weighed this half and it is 5 5/8 oz. as you see it, uncovered. Wing half, flap, and hinges. So I think I am still OK with the weight even though I added a little weight with the added structure. No matter how light it is, it aint good if it aint straight. I did the same to both halves. At this point I'm not too worried as it will be pulled around by a Stalker 61 side exhaust.....Still having fun.

Bob Reeves · « **Reply #33 on:** January 23, 2010, 04:53:44 PM »

Ya I poked my thumb through the leading edge sheeting just picking it up. I put shear webs in the trailing edge and in the first bay of the leading edge. Made a big difference in the stiffness of the wing and maybe I won't break the trailing edge sheeting.

I sanded 1/32 off each side of the flaps using rods and sheeted them with 1/32 balsa. They are now straight and stiff. While I was at it went ahead and sheeted the elevators with 1/32. They are thinner than the stab to start with so I didn't sand them other than making sure they were flat. They are also straight and stiff.

Greg L Bahrman · « **Reply #34 on:** February 20, 2010, 09:43:29 PM »

Progress has been kind of slow, but we are back at it again. The wing is covered and now I have to do the controls and cover the flaps and start putting it together. I had planned to do the wings with monocoat but since I didn't have the kote and I've been out of work etc. and I already have the silkspan and paint. I think the silkspan is helpful in the strength it adds........I also put silkspan on the fuse........I like this part because it's where it starts to look like a plane. Yeeee Haaaa

Steve Helmick · « **Reply #35 on:** February 28, 2010, 08:29:31 PM »

Quote from: Bill Barber on December 22, 2009, 12:42:10 PM

My St.60 is an old one without muffler ears , have a strap-on muffler . Will ask Randy if he has extension for a strap-on muffler .
Bill

I'd suggest checking with Tom Lay about one of his adapters (screws to center post) and pair that up with a Scott Dinger tube muffler with a longer neck (if required). They're both kinda local to you, at least, and Scott does custom stuff. At this point, I have one of Tom's adapters, but have Randy Aero tube mufflers. I like Randy's mufflers, but they need an angled outlet stack to blow some goo off the plane...so you need to add a "rubber ducky". More $ and more grams.

Steve

Bill Barber · « **Reply #36 on:** February 28, 2010, 11:06:44 PM »

Greg recommended I talked to Scott Riese ,so Scott ended up making me a neck extension for a tube muffler . He also made it bolt on to my ST.60 even though it doesn't have muffler ears . Scott did some creative thinking & very good machine work . Haven't tried it yet , will update when I do .
Bill

Greg L Bahrman · « **Reply #37 on:** March 16, 2010, 07:54:51 PM »

I made a 1/16 ply doubler that glues to the inside of the fuse and the inside of the filler piece that goes under the wing. Simple yet really strong. Made 2 one for each side. Pictures show the cardboard template. I had to slot the fuse and slot the filler piece so the doubler could fit tight against the fuse side. In picture 1 you can see that the doubler will be against the wing. In picture 2 you can see the doublers location except it's going to be on the inside of the fuse sheeting. In picture 3 you can see the end of the filler piece and the slot on the right side, still have to cut the other side.

Wynn Robins · « **Reply #38 on:** March 16, 2010, 09:38:35 PM »

I'm doing mine in similar fashion ........good idea tho.....

Bradley Walker · « **Reply #39 on:** March 17, 2010, 05:13:02 PM »

Another darn good idea, Greg.

Greg L Bahrman · « **Reply #40 on:** March 17, 2010, 08:43:44 PM »

Thanks Wynn and Brad......

Starting to do the pushrods. I think I'll try these 4-40 aluminum rod ends.....Oh and the wheels......I got the info from Doug Moon. There really cool. Doug also mentioned that the tires are replaceable as you can buy new treads to put on your existing rims........neato

Stan Bidowski · « **Reply #41 on:** March 18, 2010, 06:38:26 PM »

Greg, tell us more about the source for these parts. The wheels look good.
What sizes are available, and from who?

Thanks, Stan Bidowski

Greg L Bahrman · « **Reply #42 on:** March 19, 2010, 06:44:43 PM »

Maxx wheels and rod ends. I think Howard posted this one http://www.rcrockcrawling.com/product_info.php?products_id=256

Still have not decided which rod end to use yet. Picture shows the one that came in the kit on the left. The monster from tower in the middle and the aluminum one on the right. The one in the middle is starting to look real good to me. It is twice as thick as the stock one.