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Author Topic: Sparky's plywood flap/elevator hinges  (Read 3128 times)

Offline Joe Ed Pederson

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Sparky's plywood flap/elevator hinges
« on: March 17, 2023, 03:19:35 PM »
I watched Sparky's video titled "Hinge Install" on the Minado https://www.youtube.com/results?search_query=Sparky+%22Hinge+Install%22   In the video Sparky said he would make a set of the plywood pocket hinges for $10.00.  Perhaps Sparky still makes them, but I know he's got quite a few irons in the fire and might not have time to make them anymore.   And after the inflation of the last few years, he should charge more for them.     I'm talking about the plywood pockets hinges that have a 1" long tail and a round end with a hole in the middle of the circle.   If it helps identify the piece I'm talking about, in another video he shows that the hole is bushed with the appropriate size brass eyelets.

I could never cut them out precisely enough and especially I couldn't get the round part round.   It would seem these plywood pieces could be lazer cut by the hundreds. 

I just want to ask if anyone knows 1) if these pieces are available anywhere, and 2) if so, who makes and sells them?

Thanks,
Joe Ed Pederson

Offline Craig Beswick

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Re: Sparky's plywood flap/elevator hinges
« Reply #1 on: March 17, 2023, 05:28:11 PM »
Joe,
I am pretty sure Greg, from Southridge CNC, was making them. I think they were a bit more expensive than $10 though. He is in vendors corner.

Craig

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Offline Joe Ed Pederson

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Re: Sparky's plywood flap/elevator hinges
« Reply #2 on: March 17, 2023, 05:40:00 PM »
Thanks, Craig.

I checked his vendor's thread and it says Greg closed up shop in January 2022.

Joe Ed Pederson
« Last Edit: March 17, 2023, 06:45:01 PM by Joe Ed Pederson »

Offline john e. holliday

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Re: Sparky's plywood flap/elevator hinges
« Reply #3 on: March 18, 2023, 12:44:42 PM »
,Joe, do you have one of the hinges?   If so contact Pat King at PDK Laser Cut kits in the vendors section. D>K
John E. "DOC" Holliday
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Offline Ken Culbertson

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Re: Sparky's plywood flap/elevator hinges
« Reply #4 on: October 30, 2023, 02:04:00 PM »
This is perhaps the best hinge available for electric.  But, it leads to the question of sealing the flaps.  It is simple when the hinge is on or ahead of the flap LE but very difficult if the pivot point is 1/8" or more aft of the flap LE.  I have used Robarts recessed 1/8" into the flap to give me an imbedding into the wing.  I have never been able to seal this type of hinge and I am curious if it is even beneficial if there is never a visible gap.  I have flown the same design with standard sealed flaps and imbedded non-sealed flaps and there doesn't seem to be much difference.

Ken

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Offline john e. holliday

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Re: Sparky's plywood flap/elevator hinges
« Reply #5 on: October 31, 2023, 06:17:01 PM »
I myself put clear mylar over the surfaces of the wing and flaps, same with stab and elevater before hinging them.  With these type of hinges I don't think the gap needs to be sealed.  My opinion. D>K
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Online RC Storick

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Re: Sparky's plywood flap/elevator hinges
« Reply #6 on: November 01, 2023, 09:26:00 AM »
I watched Sparky's video titled "Hinge Install" on the Minado https://www.youtube.com/results?search_query=Sparky+%22Hinge+Install%22   In the video Sparky said he would make a set of the plywood pocket hinges for $10.00.  Perhaps Sparky still makes them, but I know he's got quite a few irons in the fire and might not have time to make them anymore.   And after the inflation of the last few years, he should charge more for them.     I'm talking about the plywood pockets hinges that have a 1" long tail and a round end with a hole in the middle of the circle.   If it helps identify the piece I'm talking about, in another video he shows that the hole is bushed with the appropriate size brass eyelets.

I could never cut them out precisely enough and especially I couldn't get the round part round.   It would seem these plywood pieces could be lazer cut by the hundreds. 

I just want to ask if anyone knows 1) if these pieces are available anywhere, and 2) if so, who makes and sells them?

Thanks,
Joe Ed Pederson

I don't make them or sell them anymore as people complained about $10.00 for a set of hinges. It's a loser for me.
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Offline Dan McEntee

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Re: Sparky's plywood flap/elevator hinges
« Reply #7 on: November 01, 2023, 10:27:48 AM »
I don't make them or sell them anymore as people complained about $10.00 for a set of hinges. It's a loser for me.

   Besides your video, does a good drawing or diagram exist anywhere?
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Offline Ken Culbertson

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Re: Sparky's plywood flap/elevator hinges
« Reply #8 on: November 01, 2023, 02:15:01 PM »
   Besides your video, does a good drawing or diagram exist anywhere?
  Type at you later,
    Dan McEntee
You might contact Mark Wood.  He has the equipment to make them.  I have a set of his going into my next ship

Ken
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Offline Miotch

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Re: Sparky's plywood flap/elevator hinges
« Reply #9 on: November 03, 2023, 11:29:42 AM »
I don't make them or sell them anymore as people complained about $10.00 for a set of hinges. It's a loser for me.

Wow.  At this point, I wouldn't walk to my shed to get an envelope and mail air for anything less than $10.  Time is money and $10 sounds like a bargain for something that would work.

Offline Steve Dwyer

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Re: Sparky's plywood flap/elevator hinges
« Reply #10 on: December 28, 2023, 08:31:04 AM »
Has anyone seen the sketch of Sparky's plywood hinges with the brass insert? I been the watching the Profile Viper series I'd like to give it a try.

Steve

Offline Ken Culbertson

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Re: Sparky's plywood flap/elevator hinges
« Reply #11 on: December 28, 2023, 12:38:04 PM »
Has anyone seen the sketch of Sparky's plywood hinges with the brass insert? I been the watching the Profile Viper series I'd like to give it a try.

Steve
I use a method of using Sparkey's version of the European pocket hinge that makes it removable like removable slip out wire on DuBro hinges.  I am making one now.  One elevator is finished.  If you are interested I will post some pictures of the finished one and the process as I make the 2nd elevator.  When finished they are just like Sparkey's only removable.  Super free and solid.

Ken
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Online RC Storick

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Re: Sparky's plywood flap/elevator hinges
« Reply #12 on: December 28, 2023, 01:37:58 PM »
Mine can be made removable too
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Offline Ken Culbertson

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Re: Sparky's plywood flap/elevator hinges
« Reply #13 on: December 28, 2023, 02:42:33 PM »
Mine can be made removable too
Is there a picture or video?  I am always interested in a better way to do things.  An alternative to what I am doing is to get some 1/8" square plastic tubing and make pockets.  I absolutely love your Viper profile.

Ken
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Offline john e. holliday

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Re: Sparky's plywood flap/elevator hinges
« Reply #14 on: December 28, 2023, 11:58:23 PM »
Go to Youtube and search for controline model airplane hinges.  Then scroll down to the video controline gapless hinges by Robert Storick.  The peices look simple enough to make using a good jig saw.  I may get out to the shop and try making somes if I get in the mood. D>K
John E. "DOC" Holliday
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Offline Marty Hammersmith

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Re: Sparky's plywood flap/elevator hinges
« Reply #15 on: December 29, 2023, 03:17:50 AM »
I don't make them or sell them anymore as people complained about $10.00 for a set of hinges. It's a loser for me.

Drives me crazy how people want everyone else to work for free.
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Offline jfv

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Re: Sparky's plywood flap/elevator hinges
« Reply #16 on: December 29, 2023, 05:05:01 AM »
I use 1/2 of a Robert Pin Hinge.  Push the pin out with my drill press and a small diameter wire.  I sand off the small protruding piece of the hinge for aesthetics.  Robert hinge piece goes into the stab or wing and the tubing on the elevator or flap.  I use a carbon fiber rod on my electrics and a wire rod for my IC.  DON'T use a carbon fiber rod on IC.

Since the control surface fits into a concave grove I have found no need to seal the hinges.
Jim Vigani

Offline Ken Culbertson

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Re: Sparky's plywood flap/elevator hinges
« Reply #17 on: December 29, 2023, 06:37:23 AM »
Guess I don't need to post my method now.  It is nearly identical except I use the pocket instead of the Robart.  I was considering the CF for the bushings in the hinge.  I would guess with the Robarts you don't need a bushing.  I use the same tunnel method for the wire.  I was worried at first that the holes would bind but a little beveling of the edges and rounding the tip of the wire ended that worry.  With the hinge line on the TE you get no distortion (bumps) to the airfoil as the flap/elevator.
You can seal them, but it is a Royal PIA to do it and I found that if you get the moving surface into the wing/stab equal the radius, sealing has no effect.  Then there is the side benefit - it looks cool.  I am curious how much gap you allow.  I am using 1/64 on the stab and 1/32 on flaps to account for wing flex.

Ken

I am curious looking at your 5th image.  Your pivot point is behind the elevator radius which will result in a small bump when deflected.  I have been exploring this with Mark Wood and I would like to know if it has any effect.  I use a much different stab airfoil.  Sort of a cross between the sharp LE and the European style thin elevator.
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Offline Steve Dwyer

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Re: Sparky's plywood flap/elevator hinges
« Reply #18 on: December 29, 2023, 08:51:13 AM »
My question was referring to Sparky's plywood hinges that he made and apparently was selling them at one time. I am looking for a sketch and more preferably any tips on making them, I could not find anything on an earlier post. I assume they must be made out of good quality aircraft plywood. Is 1/8" the preferred thickness and are they cut on a scroll saw and finished on a disc sander to a 3/8" diameter? What is the preferred dimension of the shank and is it recommended to coat them with CA to harden the surface before installing?  And of course, what is the recommended grommet part number, ID and source?

The application of these hinges appears to be limited to a 3/8" thick or greater flap, and elevator. I'm wondering though, if anyone has tried them on 1/4" thick material? This would require a thinner diameter CF tube imbedded into the routed grove. The control surface material wall thickness would become limited but then we all have used Dubro's barrel hinges on 1/8" control surfaces.

There is a good display of Sparky's installing plywood hinges with the CF tube on one of his beginning recent Profile Viper videos. There is another some years earlier video of him imbedding a small length of wire beneath balsa blocks instead using a CF tube. To me the CF tube idea is more desirable and with use of a removable pull wire commonly used on cowling on experimental aircraft the surfaces can be taken off if one needed to. But this would require a very secure configuration where the horn wire is inserted in the "horn box" since it would not be epoxied. On this point I must ask, why is Bass Wood more preferred over plywood to make the horn boxes? Lastly for JFV why don't you use CF rod on IC?

One last question for those recommending the Roberts hinge in this application where a continuous rod is inserted through a similarly imbedded tube after removing the Roberts pin. Sparky commented on not using these hinges as they can cause problems. I wonder if the insertion rod alignment can cause binding of if adhering plastic to wood is the concern?

Thanks, Happy New Year,

Steve

Offline Ken Culbertson

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Re: Sparky's plywood flap/elevator hinges
« Reply #19 on: December 29, 2023, 09:35:10 AM »
My elevator below is 1/4" but it will be about 9/32 finished.  Here is a pix of the pocket hinge made by Mark Wood.  It is 5/16" diameter with a 1" x 1/8" shaft made from marine grade 1/8" plywood laser cut.  I use an aluminum tubing bushing with a .030 ID.  I use the same tubing for the internal guided that are epoxied in.  It is anything but weak.  I have clamped one in a vise and put 30lbs weight on it and it did not even twist. With 3 in each flap that would be 90 lbs of flap force required to break them.  I use 4.  The reason I do not use CF tube for the bushings is that it delaminates too easy for that short length, and you have to allow for some flexing in the wing.  Aluminum or brass will not do that.  Also the bushings are easily replaced if they start showing ware.

If I were going to have another set made I would put a slight radius on the arm where it contacts the drum.  Makes it stronger.
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Online Lauri Malila

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Re: Sparky's plywood flap/elevator hinges
« Reply #20 on: December 29, 2023, 12:12:25 PM »
I would rather make them from Tufnol (phenolic/cotton) sheet. No bushings needed. But I don't know how well it can be cut with laser, probably not very well. L

Offline Phil J

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Re: Sparky's plywood flap/elevator hinges
« Reply #21 on: December 29, 2023, 12:16:42 PM »
I sent A DXF file to National Balsa to cut out some blanks on 12" x 12" x 1/8" plywood.  Cost me about 75 bucks for some 240 pcs. that's about .31 cents a piece.  If you need help with a DXF file send me a PM and I can help you out.   I have included a PDF of the ones I had made for 3/8 tail surfaces.

 

Offline Steve Dwyer

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Re: Sparky's plywood flap/elevator hinges
« Reply #22 on: December 29, 2023, 01:54:32 PM »
Ken,

I did not come away thinking CF would be a suitable bearing material. If you refer to James V response (below), he is referring to using CF rod as a guide adjacent to the Roberts hinge and not as a bearing. I still have to ask the question why not use CF in IC applications as Jim states?

I use 1/2 of a Robert Pin Hinge.  Push the pin out with my drill press and a small diameter wire.  I sand off the small protruding piece of the hinge for aesthetics.  Robert hinge piece goes into the stab or wing and the tubing on the elevator or flap.  I use a carbon fiber rod on my electrics and a wire rod for my IC.  DON'T use a carbon fiber rod on IC.

Here's another thought when using CF guide rod with plywood hinges. Why not instead of using a rod the full length of the elevator or flap use a small 3/4 to 1" piece on each side of the hinge? By chamfering the id will allow the hinge wire to easily feed through hinge and on to the next hinge without getting hung up. I haven't weighed CF rod to see if this would help reduce weight, but it would certainly be a cost savings. Also place a couple of guides in the slot as supports to prevent the wire from vibrating.

Thanks for the hinge drawings I'll contact Pat King to see what he would charge.

Steve

Offline Ken Culbertson

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Re: Sparky's plywood flap/elevator hinges
« Reply #23 on: December 29, 2023, 03:36:09 PM »
Ken,

I did not come away thinking CF would be a suitable bearing material. If you refer to James V response (below), he is referring to using CF rod as a guide adjacent to the Roberts hinge and not as a bearing. I still have to ask the question why not use CF in IC applications as Jim states?

I use 1/2 of a Robert Pin Hinge.  Push the pin out with my drill press and a small diameter wire.  I sand off the small protruding piece of the hinge for aesthetics.  Robert hinge piece goes into the stab or wing and the tubing on the elevator or flap.  I use a carbon fiber rod on my electrics and a wire rod for my IC.  DON'T use a carbon fiber rod on IC.

Here's another thought when using CF guide rod with plywood hinges. Why not instead of using a rod the full length of the elevator or flap use a small 3/4 to 1" piece on each side of the hinge? By chamfering the id will allow the hinge wire to easily feed through hinge and on to the next hinge without getting hung up. I haven't weighed CF rod to see if this would help reduce weight, but it would certainly be a cost savings. Also place a couple of guides in the slot as supports to prevent the wire from vibrating.

Thanks for the hinge drawings I'll contact Pat King to see what he would charge.

Steve

I started out using a full aluminum tube and found it totally unnecessary.  I am using a 1/2" piece now on either side of the hinge and it is super.  I tried the CF but found that the ends of the holes would fuzzy up with repeated removal of the wire and that scared me that it would wait till the plane was finished to delaminate and clog a hole and not let me put the wire back in.  CF is not that much lighter than aluminum.
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Offline Howard Rush

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Re: Sparky's plywood flap/elevator hinges
« Reply #24 on: December 29, 2023, 07:23:27 PM »
I would rather make them from Tufnol (phenolic/cotton) sheet. No bushings needed. But I don't know how well it can be cut with laser, probably not very well. L

I couldn’t find any phenolic around Jive Combat Team Laboratories that doesn’t have glass in it. If somebody wants to send me some phenolic, I’ll see how it lasers.
The Jive Combat Team
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Offline Steve Dwyer

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Re: Sparky's plywood flap/elevator hinges
« Reply #25 on: December 29, 2023, 07:54:01 PM »
My elevator below is 1/4" but it will be about 9/32 finished.  Here is a pix of the pocket hinge made by Mark Wood.  It is 5/16" diameter with a 1" x 1/8" shaft made from marine grade 1/8" plywood laser cut.  I use an aluminum tubing bushing with a .030 ID.  I use the same tubing for the internal guided that are epoxied in.  It is anything but weak.  I have clamped one in a vise and put 30lbs weight on it and it did not even twist. With 3 in each flap that would be 90 lbs of flap force required to break them.  I use 4.  The reason I do not use CF tube for the bushings is that it delaminates too easy for that short length, and you have to allow for some flexing in the wing.  Aluminum or brass will not do that.  Also the bushings are easily replaced if they start showing ware.
If I were going to have another set made I would put a slight radius on the arm where it contacts the drum.  Makes it stronger.

Ken,
In your case when using a 1/4" thick finished elevator (9/32) the 5/16" ball of the hinge slightly protrudes above the control surface. I don't see an issue here especially if the elevators are installed after the finishing.
Steve

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Re: Sparky's plywood flap/elevator hinges
« Reply #26 on: December 30, 2023, 01:09:39 AM »
I couldn’t find any phenolic around Jive Combat Team Laboratories that doesn’t have glass in it. If somebody wants to send me some phenolic, I’ll see how it lasers.

I can send you if you want, but propably it would be better to send it when I’m in CA in february.
Prepare for horrible smell.
I noticed that McMaster has a huge sortiment of things calles Garolite. But there are many resin/fiber combinations. L

Online Mark Gerber

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Re: Sparky's plywood flap/elevator hinges
« Reply #27 on: December 30, 2023, 05:57:14 AM »
Robart sells a version of their pinned hinge without the pin.  I used them on my Bearcat III flaps with a removable piece of music wire on each wing so I could detach the flaps if necessary.

Mark Gerber

Offline Steve Dwyer

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Re: Sparky's plywood flap/elevator hinges
« Reply #28 on: December 30, 2023, 07:21:20 AM »
Apparently phenolic resin can be laser cut (YouTube videos) but the edges become darkened like charcoal. The test will be to determine if the 1/8" shank portion material becomes compromised and weakened or brittle with heat and unable to support the protruding bulb of the hinge.

If I have any hinges made in either plywood or something else, I'd prefer not to have the hole made. This would allow me to center drill it to fit my bearing material and diameter of choice.

I stand corrected on my earlier reference to Robarts hinges and not Roberts. It appears they are an option to the plywood configuration and worth consideration. I wonder if the hinge pin easily pushes out or must the cap be drilled off and is there enough heat generated to distort the hole in the plastic?

Steve

Online Steve Berry

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Re: Sparky's plywood flap/elevator hinges
« Reply #29 on: December 30, 2023, 08:08:37 AM »
LOL....you guys are way overthinking these hinges. I've watched Sparky install them many times, and drew up the outline for them in his Viper plans (CAD by yours truly, I might add).

It's simply 1/8" aircraft plywood, 1" long X 1/8" wide tang, and a 3/8" diameter "bulb" on the end with a .059" hole centered that accepts a small brass bushing (https://www.rivetsonline.com/gs2-6-brass-eyelets/gs2-6b) that in-turn accepts a .040" diameter wire.

Take your stationary stock (wing TE/stab), run it through a router to produce a 3/8" diameter half round groove centered in the trailing edge of the stationary piece.

Use a 1/8" wide saw blade (typical table saw blade width) to groove the leading edge of the moving stock (elevator/flap). In this groove, use epoxy or thick CA to secure a carbon fiber rod (3mm OD/1.5mm ID) the whole length (https://alofthobbies.com/collections/pultruded-carbon-fiber/products/3mm-x-1-5mm-x-500mm. Then just simply glue in some balsa to act as a cap over this and trim to size/shape of the moving surface.

Now, here is where it gets a little "sticky". Sparky purchased a cheap Harbor Freight (I believe) bench top table saw that is about as weak as can be. He only uses it for one thing, and one thing only - cutting 1/8" wide (blade width) x just over 3/8" deep slots in the leading edges of the moving stock. Cut right through the carbon tube, as well. This produces the slots for the hinges

Now, just take the hinge, with brass bushing installed & peened over to keep it from falling out (I suppose one could also use brass tubing of an appropriate size, and simply peen it over, as well), place it in the slot, and run the wire through. It should be a free moving fit - if not, sand wherever it binds.

Line up the prepared moving stock and mark where your newly cut hinge slots are on the stationary stock. In these locations, drill a 1/8" diameter hole (same process as a Robarts hinge). Follow that up with a sacrificial hinge that has has the tang cut at an angle. This hinge will be used to broach the round hole and form it into a square hole.

Pre-fitting the hinges a few times will insure the pieces fit together very well. After finishing the entire airframe, 5-minute epoxy or wood glue can be used to secure the tang of the of hinge into the square hole.

Overall, after getting the hinges laser cut, and buying the brass bushings in bulk, the whole hinge system becomes incredibly cheap & easy. Most all of the roads y'all are going down have already been explored by Sparky, and he keeps coming back to the tried and true plywood versions. They simply work, are cheap, and are easy to do.

Steve

Offline Ken Culbertson

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Re: Sparky's plywood flap/elevator hinges
« Reply #30 on: December 30, 2023, 08:18:49 AM »
Ken,
In your case when using a 1/4" thick finished elevator (9/32) the 5/16" ball of the hinge slightly protrudes above the control surface. I don't see an issue here especially if the elevators are installed after the finishing.
Steve
I have considered that.  What I plan, at this point, is to wait to see how much the finish adds and sand them slightly till they are flush.  They will also have to be finished.  I plan to soak them with CA and paint them to match whatever color scheme there is at the hinge line. Lot of busy work, but I love busy work on a plane at the start of a build.  Then it gets close to the end and I just want to finish the GD thing and fly it.  Character flaw.

So far on the elevator I have just built, they do not look odd because the stab is 1/32" thicker on each side with 1/8" of the elevator (1/2 the radius) fully imbedded.  However, you raise a valid point.  I drew up the hinges for a 5/16 tapered flap.  I will be using 1/4" flat/slab so there will be some "bump" unless I change to a tapered flap which I doubt.  I have grown to like the performance of a flat flap even if they do look bad.

ken

In response to Steve B, the size of the "bulb" needs to match the finished thickness of the flap.  It can be any size.  For those of us that do not have a table router, the LE of the elevator once rounded makes a perfect sanding block for the channel leaving you a gap = the thickness of the sandpaper which is just about right.  Don't forget to allow for wing flex.  If the fit is too tight they will bind in corners, not good.  .040 wire is overkill for a full span pull wire.  .027 into a .030 ID tube is enough with bushings to match.  I would avoid using CF tubing anywhere it will be cross cut.  It delaminates far too easily.  Brass or copper.  I also see no need for gromet like bushings.  Just use the size tubing that has the right ID for the wire, push it into the center hole till it is flush and drop some CA on the other side.  When it is set saw it flush and use a small drill in a hand chuck to taper the openings.  If the wire is inserted in any of this keep the fast set CA in separate room until the wire is out.  That stuff will lock up a hinge from 50 yards away and linger in a metal tube for hours waiting for you to insert the wire! VD~
« Last Edit: December 30, 2023, 08:42:30 AM by Ken Culbertson »
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Online Guy Markham

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Re: Sparky's plywood flap/elevator hinges.......... Another Option
« Reply #31 on: December 30, 2023, 09:48:43 AM »
Fourmost  Products has hinges that look like F2b ones . Go to their site as they have 2 sizes. Small  # 144 takes a .046 or 3/64" wire and larger  #145 takes a .062 or 1/16' wire or you could bush the wire into a short brass tube if you think that the wire would enlarge the nylon hinge over time ?
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Offline Steve Dwyer

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Re: Sparky's plywood flap/elevator hinges
« Reply #32 on: December 30, 2023, 11:25:53 AM »
To Steve Berry,
[/quote]
Take your stationary stock (wing TE/stab), run it through a router to produce a 3/8" diameter half round groove centered in the trailing edge of the stationary piece.
[/quote]

Steve,

Am I missing something here, do you mean to run the moving stock (elevator and flaps) through the router to make the 3/8" deep centered groove in the leading edge? You are saying to make the groove in the stationary stock??

Steve D.

Online Steve Berry

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Re: Sparky's plywood flap/elevator hinges
« Reply #33 on: December 30, 2023, 02:47:29 PM »
Very simple...

We'll use the stab as the example, but it holds the same for the trailing edge of the wing.

Using Sparky's Viper as the example.

The stab is about 9/16" thick. Use a 3/8" ball-nosed router bit to route a "groove" 3/16" deep into the stab, full length of stab. This is the recess the elevators will tuck into. If your elevator is more than 3/8" thick, adjust accordingly (e.g. use a 1/2" ball-nose router bit & cut a 1/4" deep groove in stab).

Does that make a bit more sense?

Steve

Offline Ken Culbertson

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Re: Sparky's plywood flap/elevator hinges
« Reply #34 on: December 30, 2023, 04:03:28 PM »
Very simple...

We'll use the stab as the example, but it holds the same for the trailing edge of the wing.

Using Sparky's Viper as the example.

The stab is about 9/16" thick. Use a 3/8" ball-nosed router bit to route a "groove" 3/16" deep into the stab, full length of stab. This is the recess the elevators will tuck into. If your elevator is more than 3/8" thick, adjust accordingly (e.g. use a 1/2" ball-nose router bit & cut a 1/4" deep groove in stab).

Does that make a bit more sense?

Steve
It does if you have a router and a ball nose router bit.

ken
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