Suggestions for upscale Gyroc hinge material

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Apr 22, 2009
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Ok folks, I'm feeling the need to build another BT60 based upscale Gyroc. On my first (and only 'til now) I used the VCR label strip which worked well for about 5-7 flights. It flew great on C11s and D12s. After those first flights I had started to notice it was peeling up and losing its strength. The final straw for this rocket was at Whitakers '02 when I put an E15 in it. On its way up one of the flaps ripped off. Granted, I may never attempt a composite on this scale Gyroc again, but I was wondering if anyone had any suggestions as to the best hinge material for this sized bird.

Here are some of my ideas with concerns:

1. Cardstock - should adhere well with CyA, but after time might tear at seam. A little Florida humidity won't help either.

2. Ripstop Nylon strip - not rigid enough. Flap will offset with main fin.

3. Self-adhesive monokote - might tear easily

4. mini-plastic R/C hinges - stick well and should be durable, but finishing and hiding them will be a bear.

Any suggestions would be greatly appreciated. BTW, here's a link to an old thread on my <a href="">Gyroc Upscales</a> which included a 2.6" 29mm powered version.

I would suggest Tyvec. The stuff is VERY tough. I used to laminate it to balsa sheet to make 'blast tubes' for some of my rubber powered free flight planes.

On a rocket you could probably just CA it on...or use epoxy. We used to slather on a thin layer of white elmer's and wait for it to dry. Once dry you can use a hot iron and iron it onto sheet balsa.

BTW...sometimes you can get free (or very cheap) Tyvec at the post office. It's used for those impossible to open overnight envelopes.

Hint...if you're careful, you can split is apart with an exacto knife. This leaves you two pieces with one size "fuzzy" so the glue can grab better.

Good Luck,
I would suggest small nylon DuBro type hinges. I don't know the thickness of the balsa fins on your upscale but you can often hide the hinges almost completely.

You can slit the balsa fin at the trailing edge with a hobby knife. Make the slit just a little wider and deeper than the hinge. You can then insert the hinge into the fin edge. Repeat the process for the flap.

These hinges usually have 2 or 3 holes in them so they can be secured to the airplane. If you note where the holes are you can drill through the fins and flaps to expose these holes. You can then insert toothpics through the holes and cut them off even with the surface of the balsa. Of course, you'll want to CA everything in place.
1" fibreglass reinforced packing tape is used for the aileron hinges on my D12 powered Edmonds Arcie-II RC/BG. the stuff is tough as nails and adheres well to raw balsa.. should stick Great on a painted surface.
I agree with DON. Here is a good link. I used these alot when used to be in RC. They work great, are easy to install and last forever!
Tower Hobbies is where the link is from...

I also recommend those hinges and here's a neat way to get them installed so that they *stay* in place...

See the attached drawing (note, just for reference, not the right shape for the Gyroc):

Basically, what you do is layer the wing and control flap with the hinge sandwiched in between.

You calculate the thickness of your wing and devide by 3 (rounding off to readily available wood thicknesses...)

You cut out TWO wing patterns (for each wing) (outer layer drawing in the attached image)

Then you cut out a center core with notches for the hinges. The notch should match the size of 1 side of the hinge with (optional) room for 1/2 of the elbow of the hinge.

NOTE: The grain of the outer layers are conventional and parallel with the leading edge. The grain of the core is 90 out from that direrction, as shown. This will give the final wing much greater strength

To assemble, you run a layer of glue on one side of the core then glue it to one of the outer wing layers. Then, using white glue, epoxy or CA as your needs dictate, set the hinges into the provided notches, being careful not to get glue on the hinge elbow. Allowing the glue to ooze up through the holes in the hinge flap provides good strong glue rivets to secure the hinge.

Spread another film of glue on the topside of the core and place the other outer layer wing in place.

Now, press between several books to keep it flat as it dries.

Them hinges ain't going *nowhere*! :)

Hope my drawing is clear enough. I've done this a number of times and, if assembled properly, the elbow of the hinge will give out *long* before your glue joint will...

Another thought, in conjunction with my method above, is to make *real* rivets for your assembly.

WHen you glue the hinge into the notches, you can use a pin to poke a locator hole through the hinge hole and through the one outer layer of the wing, for each hinge hole.

Then, after the assembly is dry, you can use a small drill bit to drill out all the holes, all the way through the wing assembly.

Then it is a simple matter to apply a drop of glue in each hole and push the point of a tooth pick into each hole. Using any of a number of tools, trim these toothpicks down flush wiht the surface of the wing.

These rivets could even add an interesting look to the finished wing and spin tab if left raised a little bit.

The *wing* will shatter to pieces long before these hinges let loose... :)
Great suggestions guys. The hinge approach does seem daunting, but I think I can manage. I imagine since the overall thickness of the fins/flaps will be no more than 1/8" (what has been used previously), I can probably layer up some balsa. I may just go ahead and use 3/16" so that it could withstand an E15 flight.

I also kinda like the reinforced tape idea too. Seems easy to implement and should easily last multiple flights. My *only* reservation about using anything self-adhesive is that it can unstick down the road.

I guess it's off to the races. I'll drop in again once I have parts cut and whatnot.

Thanks again for all of the suggestions.
Originally posted by shockwaveriderz
consider a "Living hinge"
You then just have to slot each surface and glue the hinge in...
Have you actually tried this stuff? I'd think that it'd be dfficult to get adhesive to stick well since it polypropelene. What did you glue 'em with?

What about using a cotton webbing fabric, muslin or even leather for hinges. All these should hold up and be easy to glue down.

Bruce S. Levison, NAR #69055

I had an idea. (I'm putting the final touches on my Gyroc clone from ThrustAero) I didn't remember these being so small when I was a kid....

For the big version....Why not make up a piano style hinge using launch lugs and a 1/8" inch dia. dowel? Cut up 1/2 to 1" lengths of lug tube and alternately glue them to the fin and flap like a piano hinge. You can slide in the dowel and glue it to the outside tubes to keep it together.

....just a thought...

I might be a little late posting to this thread, but I didn't see anyone mention using CA hinges.

Basically, you slot both pieces, slide the CA hinge material into both halves, with a small gap to allow movement. Put some thin CA in there, and it will wick into the hinge/balsa joint making a hinge that will be stronger than the balsa surfaces themselves.

Tower Hobbies carries the stuff, here's a link:
I thought I had said something about em, but vjp is hinges are fast, simple, light and reliable. I have used about every hinging method available thanks to my R/C hobby (the other white meat ;) ) and can say they do work well.

If you look at the kit instructions over on JimZ's website
you will notice the plans call for some elastic cord to be run from the flap to the wing ahead of it, and knotted on the ends to stop it from pulling through the holes. I usually put a good drop of glue on each knot to help make sure they stay tight.
The elastic cord is the same stuff you can buy in the sewing section of your local department store. It is about 1/20 th (or so) inch in diameter, usually white, knit elastic string. You can probably get several yards for like 99 cents.
Richard! Welcome to "The Rocketry Forum!" Wow...I think I know your rockets! I had seen your Gyroc projects a LOOOooong time ago when I had started mine. I also believe I had seen your 7" dia. Patriot on the cover of an older SPR Mag. Very cool to run into you online! (Especially on TRF!) I hope you hang around for a while. This place rocks.

In response to your earlier question regarding the spring flap material, I am currently using 1/16" black round elastic thread on my BT60 based Gyroc. It is commonly found in the elastics department of any fabric store. The BT80 (29mm power!) version used about 5 strands of 1/16" elastic. (I was testing the tension at the time. I would add one band at a time to ensure a tight "flap" recovery positioning.)

Attached is a quick collage of my "Gyroc Legacy" showing various pictures of Gyrocs in action and on static display. I love this rocket!
Thanks eugenefl. Yeah, that's me with the big Citation Patriot. And yes, I started my Gyroc a few years ago, and sort of forgot about it. I want to get it finished now and fly the darn thing! ;)

I just discovered this forum, and I really like it. So I will stick around for awhile.

Thanks again for the info.