Any tips on how to fix make a flimsy airframe more rigid?

[kdobson83]

I got this wing on banggood for pretty cheap ($14) because I wanted something small, slowish, and had all electronics already.

It's "made" of EPP foam so they say. The center pod is EPP but the wing itself is a softer more flexible foam. Guess it could be a variant of EPP. I was pretty happy with it, seems to be good quality. Paints nice, came with a decent amount of flat carbon shafts, 3d printed motor plate, and nice control linkages. Weights about 230grams or so with a 1806 motor on a 3s 800mah with 9gram servos. Maiden flight looked awesome, was very locked in, slowed down to a crawl, with decent throws. Well, it flew good till the wind started to pick up. It acted as if my control throws went from 100% to 20% in the wind. Like the frame or maybe the control surfaces themselves are flexing badly.

So my question is, is there anything lightweight I can add to the bottom of this to make it more rigid? A long balsa plate maybe? Would covering it in packing tape increase rigidity? I could remove the pod and stabilizers and add tape/heat shrink but I'm not sure this would add rigidity due to it only being maybe 1/2" thick super flexible EPP.
Any help is appreciated!

 

[Brett_N]

how stiff of a breeze?

Adding stiffness won't necessarily help in the wind. These little wings (and little foam planes period!) get tossed around pretty good. I have a 3D plane setup with wing-warping rather than ailerons that I like to take out and bash around when the wind is over 5 or 6mph.

Bigger heavier planes fly better in windier conditions.

that's not a bad little wing though - maybe they'll send me one too

 

[kdobson83]

how stiff of a breeze?

Adding stiffness won't necessarily help in the wind. These little wings (and little foam planes period!) get tossed around pretty good. I have a 3D plane setup with wing-warping rather than ailerons that I like to take out and bash around when the wind is over 5 or 6mph.

Bigger heavier planes fly better in windier conditions.

that's not a bad little wing though - maybe they'll send me one too

It wasn't constant wind, it was gusty wind roughly 5-10mph. It's just felt weird. Like, when the wind was blowing the controls got SUPER un-effective/weak. I added some carbon on the control surfaces themselves so hopefully that'll help.
To be honest, I'm not sure if the flexing of the frame is the issue. Im not sure what's happening that's causing it the issue.

It is a decent wing tho. When it wasnt acting up it flew awesome. SUPER slow, but on 3s with that 1806 and 5x4x3 prop it had plenty of power/speed.

I guess more testing is needed.

 

[kilroy07]

A lot of people use laminating film (especially on fast wings).

I've done it to the cheap $10 glider wings and my Night Raiden's wings/Tail. It really tightened everything up and made the wings much stiffer (especially on the cheap glider) but it would be a pain if you've already glued in those vertical stabilizers/fences....

 

[Merv]

Packing tape or laminate film will help stiffen the wing.

 

[kdobson83]

A lot of people use laminating film (especially on fast wings).

I've done it to the cheap $10 glider wings and my Night Raiden's wings/Tail. It really tightened everything up and made the wings much stiffer (especially on the cheap glider) but it would be a pain if you've already glued in those vertical stabilizers/fences....

Not a fan of the way packing tape looks so I may have to look into laminating film. Been wanting to try it for awhile now anyway. But I used pretty small amouts of hotglue to put on the stabilizers, so it shouldn't be too hard to remove them.
Thanks for the info!!

 

[kilroy07]

I used pretty small amouts of hotglue to put on the stabilizers, so it shouldn't be too hard to remove them.

I swear by the rubbing alcohol method to remove hot glue!

 

[kdobson83]

I swear by the rubbing alcohol method to remove hot glue!

Ok, so quick question on laminating before I buy the film and iron. This wing is a single sheet of pretty flexible "EPP" foam. It does have a few of those flat carbon shafts in it, but it's pretty flexible. Does the laminating film shrink when heated up by the iron? Will this shrinkage cause the wing to bow since I can only do one side at a time? Like the Dollar Tree foam when you remove one side of the paper it curls up a bit. Will the laminating film cause this on my wing?
Thanks for the help!

 

[Merv]

The laminating film will shrink slightly, not nearly as much as old school covering film. You may get a bit of warpage, but it should smooth out when you cover the other side.

It might be a good idea to remove the paper form some DTFB and laminate it. I have laminated small planes made from DTFB w/o paper but never from a single layer of DTFB.

 

[kilroy07]

What @Merv said. The covering film I used... (I'll have to dig up the link, but I'm pretty sure it's here somewhere on the forums...)
shrank only slightly (helps remove wrinkles.... of which I had more than my fair share as it was my first covering job.)

But I did not notice any bowing on the foam glider wings and they didn't have any bracing in them...

Use lower heat (just enough to melt the adhesive...) you can always take another pass...

Take your time around that rounded leading edge... I failed to notice that the leading edge on the N.Raiden wing has a taper towards the tip....
Made for some really (really) ugly wrinkles... notch the film every so often and that will allow it to curve (if you plan on wrapping the edge.)

 

[Steve Fox]

When you go to cover your first plane, start with the iron down too low and slowly increase the temperature till you find what will make the laminate stick without overheating the foam.

There are different micron thickness levels of laminate, the thin stuff is 10x easier to work with and offers plenty of rigidity, don't buy the thicker stuff, it won't work at all well on curved surfaces.

 

[kdobson83]

When you go to cover your first plane, start with the iron down too low and slowly increase the temperature till you find what will make the laminate stick without overheating the foam.

There are different micron thickness levels of laminate, the thin stuff is 10x easier to work with and offers plenty of rigidity, don't buy the thicker stuff, it won't work at all well on curved surfaces.

I ended up getting some 1.5 stuff to experiment with. I'm gonna try it on this cheap banggood wing first. It should be pretty easy, I got all the stabilizers and pod off so it's a flat piece of EPP foam. If all goes well my next attempt will be on the Goblin kit I picked up at FliteFest. And if that goes well maybe an arrow. Got my hobby iron today. Laminate should be here sometime later this week.
Thanks for the tips guys!! If it weren't for this forum I'd never advance my skills in this hobby.

 

[Steve Fox]

I ended up getting some 1.5 stuff to experiment with. I'm gonna try it on this cheap banggood wing first. It should be pretty easy, I got all the stabilizers and pod off so it's a flat piece of EPP foam. If all goes well my next attempt will be on the Goblin kit I picked up at FliteFest. And if that goes well maybe an arrow. Got my hobby iron today. Laminate should be here sometime later this week.
Thanks for the tips guys!! If it weren't for this forum I'd never advance my skills in this hobby.

On flat foam you can get away with thicker stuff, it will make it almost bullet proof but on anything with a curved surface it will be incredibly hard to cover well with the thick film.

I bought the thicker suff at first not knowing what I was doing and it's mega strong but I quickly bought thin stiff when I realised how hard it is to work with, it's cheaper too, I got two rolls each twice as long as the thick film for 2/3 the price!