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oipigface

Building a 'live' hinge

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oipigface

Anyone any experience to share about this? I've got a piece of 1/8th ply about 16in long and 2in wide. I want to hinge it about 7in from one end. I had a go with a piece of kevlar tape which I sandwiched between the ply and some smaller pieces with chamfered edges to allow movement. I glued it up with epoxy, scraping excess epoxy off both before and after it went off. This effort worked fine but didn't stand the test of time. After a couple of days the kevlar gave way, so now I've got two bits of ply. 

Any ideas as to how such a thing could be made more robust?

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swarrans

The moulded glider manufacturers tend to use peel ply (probably because it is cheaper?).  The key bit is that you need to cut it on a 45 degree bias rather than straight so that you get lots of fibres making the hinge.

 

Simon

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Brett82

Don't know if it will work for your application but I used Geocell fish tank repair silicone on an aileron and its holding up nicely. 

Brett 

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oipigface

Thanks for the help, guys. I've rebuilt it using three layers of kevlar cut on the bias. It seems good enough that I've taken the trouble to paint it.

I did consider using silicone, but I've got kevlar on my shelf at the moment and no silicone.

Pictures will appear on the Graecalis build log thread some time later today.

 

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chiloschista

I did all my recent planes (Trisel, Foka4 and RedAcro) with Kevlar hinges. At first a thick one was used, but this is really not needed. All the last are with thin (~60g/m²) cut at 45° in stripes. One layer only!

It is glued in the sandwich under the veneer, when the wing is put under vacuum. The main, hard work is to free it. Cut at bottom until you feel the fiber, very delicate work, and scrap the upper wood surface with a triangular or square file until you feel the fabrics, even more delicate work. Then start to bend the surface little by little until the resin is broken and the surface moves freely.

It took me three evenings to free the RedAcro control surfaces.

Ric

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satinet

That's not a live hinge though. A live hinge is built in to the layup of the wing.

It's a good how to but not really different to what's been said on here before. I use geocel fish tank sealant. 

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