GameHard

Hi
I'm really new and I want to know how to make a 43" foam wing stronger. Unless you can send me a big roll of covering materials, can you give me tips on how to make a wing stronger practically and CHEAPLY? (I've hear you can cover with brown bag paper. How would you do that?)
Thanks
Joey

Al Stein

Yes, you can cover with a paper bag.

To do it, you would wet the paper with a solution of white glue or yellow glue thinned with an equal amount of water. Brush it on and let it soak in, making sure that your paper is wet everywhere before applying it to the wing.

To get a good smooth finish, I use plastic gift wrap from the dollar store (only costs a buck a roll -- obviously), wrapped over the paper... so you'd lay out the gift wrap (a piece a little longer than a wing panel and wide enough to wrap over the wing leading edge and cover top and bottom surfaces with a little extra at the trailing edge. The paper gets laid out on that and wetted all over (not drippy wet, just wet through), then that all gets smoothed onto the wing starting at the leding edge and smoothing back with a credit card edgte to get out all the air. Smooth out the underside first, lay it in the bottom cradle half left from the foam cutting, then smooth out the upper surface the same way. Put the upper cradle half on top and add a bunch of weight spread out evenly. Let it dry overnight. It gets quite stiff and does add strength.

You can decorate it with wall paint if you like. If your plane will use an engine, seal it with a clear paint or sealer.

Depending on just how much strength you need/want, you can also add spars or other reinforcements before doing the paper covering. What kind of plane is this you're working on?

GameHard

Oh it's just a cheap foam glider I bought at a toy store. I'm planning to convert it into a 380-powered glider but the wings are made of not very strong foam. It's suppose to be a cheap, don't-care-if-it-crash model as my first plane.

CafeenMan

you can put a couple strips of fiberglass packing tape from wingtip to wingtip. THat will add a lot of strength.

MinnFlyer

My Feedback: (4)

I was going to recommend the fiberglass packing tape too.

GameHard

I've heard it works better when you stretch the tape and then put it on, but on both side so the tape tension doesn't warp the wing. Would that work? Where do you get fiberglass packing tape though?
Thanks

Spaceclam

not that much more expensive is carbon fiber laminate. that stuff i have found particularly useful. just for info, check out www.cstsales.com. there they have anything composite. but to get to the laminate, visit https://www.cstsales.com/Carbon/carbon-laminates.htm scroll down about half way to "0.021 thickness". there, for a 1 inch wide, 36 inch long (the wingspan on those things is supposed to be measured from wingtip to wingtip with the fuselage attatched so you will pretty much cover the whole length) you can stiffen your whole wing more than all the other suggestions combined, while adding less weight than most of them as well. i have used this width and thickness both and they are really incredible. for your purpose, i would get that and put it on the BOTTOM of the wing, because if you manage to catch a wing or something, your wing will want to bend up, not down. use contact cement to attatch it because ca will eat your styrofoam away and epoxy is too britle to flex any. this will make your wing pretty indestructable while only adding about an ounce or two of weight while still allowing your wing to flex just a bit. i love this stuff. it is like a long strip of tape, and because it's fibers are unidirectional lengthwise, so if you line up the length with the leading edge of your wing, you will be very pleased i am sure. i discovered this stuff about a year ago, and i won't do wihtout it. i know at this point, it seems a bit extreme to go carbon fiber, but it's really not. it's just like any nifty tool.

TerrellFlyer

Hi GameHard,packing tape or better yet is unidirectional packing tape can be found at office supply outlets,the best I've found is by 3M,can run a 1 1/2 "or 2"strip where the spar would go, top and bottom,no need to prestretch tape,also some contact cement will eat foam,might test a small area when using said glue

Al Stein

There's no need to stretch fiber reinforced packing tape when you put it on -- as long as it isn't loose it'll be fine. In fact, the glass fibers whould probably prevent you from stretching it.

Regarding carbon fiber -- it has its place, but I'm not sure this is it. Try stretching a piece of common 1/2" glass fiber mailing tape to the breaking point: I doubt that either of us can do it. Now consider what would be left of your wing if it were subjected to the force you put on the glass tape trying to break it: that wing would be in the hurt locker, no doubt. So, your wing would be destroyed before it used all the tensile strength of the very cheap glass tape. Now, carbon is also used to add stiffness under compression -- that's because wing failures usually happen when the upward forces get large enough that the upper part of the wing is compressed out of shape and buckles. While it keeps its shape, it's ususally OK, so stiffness is important in extreme stress situations. Putting in a balsa spar (or laying on some balsa sheeting) will also add a bunch of stiffness at very little cost.

Packing tape is great stuff, too. It'll take a lot of tension-type loading as long as the foam (and any spars or other stiffening) will take the compressions that go with it. Packing tape is pretty cheap and it comes in pretty colors. I have a Floyd and an oown-design sloper that have minimal spars and are covered with packing tape and a little redundant fiberglass strapping tape ... check out [link=http://www.geocities.com/sparkir/]this FLOYD site[/link] for more on how other guys use the stuff.

Remeber, engineering is always a balancing act -- the engineer's job isn't just to get the biggest bang out of what he does, it's to get the best bang for the buck. That means we don't want to spend carbon fiber dollars to do something we could do for glass and balsa pennies unless weight is so critical that saving half an ounce is worth the difference in price. (For instance, an advanced competion thermal soaring plane is a good place for exotic materials.) It's not a matter of being cheap, it's matter of conserving resources that can be better used on another project.

southern_touch9

My Feedback: (3)

If you soak a brown paper bag in a glue/paste type of mix this will add a lot of weight. The simple solution is to insert one CF arrow shaft through the center of the wing at roughly 25% of the chord. I have seen this done on a handful of planes and the wings are still together with VERY VERY little weight added.

Spaceclam

this is exactly where carbon fiber shines. it's lightweight, (like foam) yet very very strong (unlike foam) and it isn't unsightly like paper bags and glue, and doesn't look like a repair the way that fiberglass packing tape does. this is exactly what carbon fiber laminate is for. strengthening while adding as little weight as possible, and keepinga low profile. you should check outthe website anyway. you will find something that will be useful later on.

Al Stein

Actually the glue solution, if diluted and spread rather than just gobbed on full strength, adds very little weight compared to the paper itself. As you say, adding a lightweight spar is a good, light alternative, but you still have to add covering -- to deal with torsion of for no other reason, so the lightness of the spar can be misleading. It has to have the weight of the covering added to it before it can be compared with the weight of the shell of a composite wing. So the paper bag method is probably not as bad as you might first guess... and after all, it is what the original post was asking about.

In the end, it's all good -- it'll work either way and as long as it's done neatly, the weight penalty will be small enough that you can live with it.

southern_touch9

My Feedback: (3)

No torsion Here??

If you look he says its just a light foam glider so there is no need to cover it.

I have seen the kind of glider he is talking about used as a hand launch and it did well.

GameHard

Actually, I'm talking about a $15 hand launch glider without any RC equipment. Kind of like a paper airplane. It's gonna be heavy when I put on a cheap (in other words, heavy) 380 motor and two 17g servos.

Thanks for the tips

Spaceclam

you can't go too cheap with these things you know, you will never be satisfied.

GameHard

It's supposed to be a trainer.

Crashem

There are several threads on Ezonemag.com about converting these types of foam (Walmart) gliders to R/C.
Check them out