Hi all,

I recently decided to get into Fpv wings after flying quadcopters for years. I picked up a Baby AR wing pro as it seemed a nice starting point size-wise. It's maiden went very well and all was well. A couple of flights (and bad landings) later, one of the elevons began to break off at the foam hinges. I don't have much experience with this EPP foam material, but I definitely knew when I was building it that those foam hinges were going to be a weak point. After some research online most solutions pointed towards some special kind of tape or hinges made from glue. None of these options enticed me as I wanted something confidently strong and something that did not look like a botched job either. As a temporary measure I simply hot-glued the fracture in the foam and continued on (pictures below). As strong as it was, it broke again from an unfortunate crash, and the repair rendered the hinges to be quite stiff, and not able to throw about half as much. Devastated about my new wing, and replacement parts being non-existent for this model, I had to do some thinking. Previously I had 3D printed a small wing model that relied on fully 3D printed elevons and hinges. So what I'm wondering is should I cut off the elevons and replace the foam hinges with a very thin slit of 3D printed plastic that would slit into the elevon and wing, or just 3D print some elevons with these slits attached and do something similar. Has anyone any experience with this type of repair job or any suggestions? TIA

Pics

Generaly this faom xan be glued and the bad look can be covered with stickers, lucky thing about is that the wing will go stiffer and more rigid and can fly better from repair to repair :-)

Pla might not work about rigidity, i believe.
Wooden elevons would work. As they are more stiff they can be more precise but they does less damping of tourbulences. I havent enough experience there but i belive these can be the benefits about faom or wood.

Personal i would just make a plate, plastic or very thin wood above and under, about 15x20mm maybe, a snadwich to bring the force on a bigger area. that worked well on faom for me.

If you decide to print your hinges, be sure to get some firm TPU for it. I'll be putting a printed plane into the air soon. Just waiting to be able to buy the guts, and that's what it uses for that mechanism. Using 95A hardness TPU from Priline. It's my favorite filament.

(26-Mar-2024, 12:40 AM)Suros Wrote: If you decide to print your hinges, be sure to get some firm TPU for it. I'll be putting a printed plane into the air soon. Just waiting to be able to buy the guts, and that's what it uses for that mechanism. Using 95A hardness TPU from Priline. It's my favorite filament.

Ive printed some test pieces to see how they will adhere inside the foam and to see the ductility of the materials. So far PETG seems like a good option at two layers thick, although it might actually need too much force to deflect. I have TPU, although I am not sure what hardness it is. It feels average. I will try that next and see if it's an option.

 https://imgur.com/a/TgNvfnt

(26-Mar-2024, 01:23 AM)panda0323 Wrote: I have TPU, although I am not sure what hardness it is. It feels average.
 https://imgur.com/a/TgNvfnt

The stuff I'm suggesting is about as hard as tire rubber. Very stiff, but can stretch quite a lot too with minimal fatigue. It's borderline indestructible.

Many use Welders adhesive and another similar called Foam Tac for making hinges with EPP.
There’s many videos on YouTube that show how using them.

Foam Tac is specifically made for EPP planes so costs more Welders is available at places like Home Depot and is not expensive.

They both are great for fast field repairs.

Hot glue hinges will work but if too stiff can strain servos and drain the battery or burn out the BEC.

There are plastic hinges you can buy that slot into both sides of the foam (wing and elevon) or glue to the top of the elevon. Something like this (made from Nylon): https://www.ebay.com/itm/131849278040

So this, or TPU hinge like someone else mentioned, could work great.

ALL my foam planes have "hinges" made this way. Currently thats 15 Slope Soarers inc 150mph plus dynamic soarers, 10 power wings (likewise not slow), and maybe another 10 more traditional wings and a tail type.

Cut out the flying surface.
Chamfer one or both edges (depending on throw desired) on the bottom side of the wing/tailplane so the top edge is not cut by at max 1mm.
Apply a SMALL bead of UHU POR to both edges and allow to nearly dry.
On a smooth surface, Workbench, etc, slide the two edges together firmly to impact glue the two as one.

IF this results in too stiff a "hinge" (rarely, mainly on tiny indoor stuff) then scalpel through leaving sections at ends and intermittantly throughout. This hinge is transparent, flexible, and I have planes inc very fast wings that were made like this near 20 years ago that are still active. After about a decade the hinge line glue might "yellow" visibly if you have used too much

You could also use mylar flexible strip (sold for hinges in model shops), scalpel into each surface, trial fit slide in, mark, roughen the mylar where its in the foam and so inviisible and glue, again POR is suitable.

Some of my fastest thinner section wings have balsa surfaces to keep them rigid and avoid twisting/loss of throw. All my stuff has half span servo rods for this same purpose.