Type of foam for tip rib?

[cjensen]

I'm going to put a styrofoam rib in each of my wingtips, but I'm not sure which type of foam to get. Menards has the pink board, no blue. I've been told that some of the foam won't jive well with epoxy, and that the blue is better.

Anyone?

[Jekyll]

The pink worked fine with west systems epoxy. See if they have some scrap they can give you. I bought a whole sheet and only used about 1 square foot of it. Only $7 though if I recall.

Jekyll

[N713R]

Chad,

The pink board and the blue board are the same stuff called exstruded polystyrene. Just a different manufacturer. I have used the foam board on my cowling and to make the custom fiberglass parts I have made so far. No problems. But, I have wrapped them all in duct tape before putting it on the foam, so there was no direct contact. Try some first. If you need some to try rather than buying some, I have all kinds of scrap pieces. But Yes, I think some of the epoxys and resins are destructive to the foam. Make sure you use the foam that is a solid extrusion, and not the stuff that is made of the little white balls.
I can tell you that Gorilla glue will not damage the foam, and does a very good job of holding it together.

[cjensen]

Perfect! Thanks gentlemen! I have the West Systems epoxy to work with.

Ben, if you have some larger pieces, I'll take 'em. If not, it's cheap stuff in Menard's aviation department...

Takin' a break from the little one already!!??

[cobra]

My guess is that the solvents used are the real problem, not the adhesives. Cannot say for sure, but Id guess that foam is more likely to be incompatable with the styrene resin (used with fiberglass) or the solvent used with urethane resins more than epoxies. Generally speaking, the thinner the materials you work with, the more solvents they probably contain. Bottom line, test your materials on a scrap piece first.

Ive wondered why the spray can urethane expanding foams are not used more to fill open spaces like wing tips. Its available everywhere and cheap. Once it cures it is easy to cut and shape, it sticks to everything in any orientation or shape, and it is very lightweight and durable- waterproof, weatherproof. Warning: dont overdo it (it really expands) or use it in closed spaces (it really expands )- it can be very messy

[N941WR]

Chad,

The blue (Dow) foam worked fine for me with the West System. Don't know about the pink stuff as I didn't have any.

Check out the pictures and text on the bottom of this page.

[RV7Guy]

He Chad,

Either will work fine. The epoxy won't eat foam.

[DanH]

Epoxy won't eat foam. Polyester resin will eat foam.

Dan

[jcoloccia]

Always be sure to throughly cook foam before eating

Seriously, though, just as an FYI, some epoxy will attack foam. 5 minute epoxy in particular can get hot enough during cure to damage foam. I just mention this because it's tempting to use the 5 minute stuff to make a quick repair on some non-structural piece.

[aparchment]

I used Hysol 9462. It's thixotropic, ie. stays where you put it, and it's easy to sand. I have used it a lot in my model jet construction. It sticks to everything. In fact the material around the glue joint will probably break before the glue lets go.

Antony