uonlylivetwice

My Feedback: (2)

Sorry to be so stupid....
Ok, I think I get that Foamula and polystyrene are the same thing, right? A guy at Home Depot told me the light, white stuff is open cell, and the pink stuff is closed cell. I couldn't get Pro Bond poly glue to glue balsa to the pink stuff, and he wasn't surprised. But I think from what I have read, the white stuff is also EPS. When you guys are using poly glue, is that on open cell EPS? I read that the fumes from EPP are bad, and yet it seems a lot of guys are building hot wire cutters, so is everyone using EPS? This can't be that hard. I imagine building a wing with the white EPS (very light stuff) would require spars for support. Can anyone help me with an explanation of this different foams, what kind of glue should work, etc?

Thanks very much

blvdbuzzard

The stores around me do not sel the pink, green, blue foam boards so I am stuck using the white stuff. It works well but may not be quite as strong as the other stuff.

All fumes from foam are bad.

I am building a 6 foot wing with the white foam and am noy using any spars. I am sheeting it with 1/16 balsa and glassing the center section. (Really big stik)

I use a resperator when I cut cores. I have not used the pro bond to sheet wings yet. I use a latex contact cement I get at a fabric store. It smells like the sourgum from Dave Brown. I also use epoxy to sheet.

Dru.

triangle

My Feedback: (3)

i can only tell you guys from my own experience, i use the white stuff, styrofoam, i get the, i think, 2lb. kind, use nichromium wire in my cutter, and probond, to sheet it. depending on the kind of flying you are going to be doing, you don't need spars, if you download the manuals from lanier, carden and other recognized great flying and championship winning planes, you'll see that they go up to 40% size with out any spars, 1/16 is my chouce of balsa thickness for wings under 100", after that use 3/32 and some carbon fiber tape or kevlar..... another great thing to use if you have one handy is a vacum pump, i use one for the automotive a/c industrie, and the dfinish is great, and cuts down the drying time (vacumm=pressure=heat=quicker dry times). on the probond is supposed to be 8 hrs dry time, i get it dry in 4 hrs @ 14psi. if you ask i can help you out.... no question is stupid, nobody was born knowing it all we where all @ your position at a certain time

uonlylivetwice

My Feedback: (2)

Thanks a lot for the help. I want to try to build a large, slow flying delta, like some of the plans I have seen shown in other threads. I just don't know a darn thing about foam and adhesives and all that, the guy at Home Depot was rambling about closed and open cell styrofoam, I want to try the lightweight, white stuff, but I assumed it'd need a spar, and I am wondering if I need to sheet the whole thing. I'll have to get some, and try probond on it. I also read some guys use wood glue. Thanks for the help. Any other sheeting techniques? This could be a lot of surface to cover in balsa....

thanks!

Flypaper 2

I think the guy at Home Depot got it backwards. Closed cell is the white stuff, sort of explains itself. White, there is nothing between the cells. Pink or blue, you can see holes between the cells like a sponge.
If your going to build a delta, it needs no spars if your going to sheet it. How big an engine? Slow flying means light. I build foam wings with a spar and sheeted from LE to spar. Put capstrips from spar to TE. Cut out the foam between the capstrips with a hotwire. Makes a wing as light as a wood wing but much stronger. My avatar is built this way. Hope this helps. Don't hesitate to holler. That's why were here, to share.

Flypaper 2

By the way, been cutting foam wings since the 60s. A delta wing is one of the hardest to cut because of the chord length between the root and the tip. If the root ir four times the length of the tip the wire has to move four times as fast at the root. Hotwire doesnt like this but it can be done. Practice on scrap till you get it. Moves to slow at the tip causing it to undercut. You can make the tip template slightly oversize then sand the foam to shape.

uonlylivetwice

My Feedback: (2)

Thanks Flypaper, just one more questions then, before I give this a try. I assume you use the lightweight white foam, what glue do you use? What glue would be suitable for gluing hardwood motor mounts to the foam?
thanks again!

triangle

My Feedback: (3)

PROBOND, WOOG GLUE BECOMES BRITLE, PROBOND DOESN'T......

Flypaper 2

I use epoxy glue the foam doesn't have much strength by itself. You may have to put a vertical former on the back of the beams to spread out the load. Cut a slot in the foam to slide the former into.

Robert Sickels

Just a little help with cutting a delta wing ! make a root template and a trailing edge template at the hing line. Then keep your wire parallel with the leading edge at all times and you will come out with a great wing.I have made F-106 wings and B-58 wings this way. If you have any questions ,you can e-mail me at [email protected] Also on gluing you can use Formica brand ,water base contact cement available at Lowe's. It works very well and it is cheap . Butch

Couch-pilot

I use 3m super 77 from a spray can. A little steep ( between $8 and $12 / can, but works good -doesn't melt the foam.

patternwannabee

My Feedback: (1)

uonly.....

The White stuff is usually 1 lb/cu ft. the Blue is 2# and I think the pink stuff may be somewhere in between. I haven't tried pink, but I've tried Blue and Probond does work on that. Pink is very similar to Blue, so I would think that it would also work on pink also. Is it possible you didn't get good contact while the Probond was curing? or maybe you needed to use more?

Anyway, most sport models use white (Expanded Bead Polystyrene). The Glider guys with their high aspect ration wings (long and thin) use blue (Extruded PolyStyrene). It's denser so a thin wing would have more strength. EPP is pretty expensive, the slope combat guys use that stuff, cause it's pretty resilient and doesn't break. Fumes from EPP are VERY bad from what I've read. But I haven't heard that fumes from EPS or Expanded Bead (white) are harmful.

I agree with Flypaper, you probably don't need spars for a Delta, but you'll probably need something to spread the load on the engine mount. One other thing to consider.. fuelproof the beams real well. If any nitro travels through the beams into the foam, you'll get a loose mount with no way to repair it.