Foam Sheets

[Motorman]

Got a pack of foam insulation sheets at home depot to fool around with. Mainly going to try and make some forms to mold balsa sheets for my fuselage. The sheets are only 3/4" thick so I have to make some glue joints. Don't have a hot wire was just going to shape them with wood working equipment. What can I use to glue foam to foam and still be fairly sandable? If I did hook up a hot wire is there a glue the wire could cut fairly easy?

Thanks,
MM

P.S. To all you who are furiously typing for me to "call Bob Hunt" please stand down, I'm having too much fun doing things myself (it's kind'a like a hobby for me).

[Pat Chewning]

Glue the foam sheets together with 3M 77 spray contact adhesive.  A light coat on each part works great.  Let dry a little bit and then press together.  You can hot-wire cut through the glue joint.

[Tim Wescott]

My local Home Depot only has white beaded foam, which I don't like sanding on.  I've never used the blue stuff -- if you can get it, you're lucky.

Craft stores have blocks of green polyurethane foam in the flower-arranging section; that's what I'm thinking of using in an upcoming project.  It's "crunchy", so it doesn't squirm away from a blade or the sandpaper when you go to cut it.  OTOH, you can't cut it with a hot wire.  Pick your poison...

[Tim Thompson]

377 may or may not melt the  foam. A lot of us have been using  Glidden  " Gripper " primer.  Sounds crazy  but it  works!  Weight it down for 24 hours and your good to go.

The 3M purple 100 sandpaper works great on Home  Depot  white beaded foam. I've done it for years, no problems.

Tim Thompson

[Mike Haverly]

I have at least 10 bucks I've made for assorted projects from Michael's green foam stuff.  It sands real easy and stands up well.  One of the projects is the canopy on last years PA airplane, laid up in the matter you described, compound curves.  I use a layer of 1/32 balsa,  a layer of light silkspan or tissue and a layer of 1/16 balsa all stuck together with aliphatic resin.  It comes out real strong and light.  I've doing my turtle decks and nose pieces the same way.  It is rigid enough that I only have three formers on my airplane and no sagging, aka starving horse look.

[Pat Chewning]

377 may or may not melt the  foam.

3M 77 sprayed onto whit beaded styrofoam,  blue extruded styrofoam, pink extruded styrofoam, while EPP foam, or black EPP foam does not melt it.   I don't know about this "377"    Did you mean 3M 77??   It will not melt the foam.   Don't spray on enough to run or puddle, just a fine mist is all that is needed.

[Perry Rose]

Any foam you use for a mold needs a stiff spine to prevent bending during the wrapping.

[Avaiojet]

MM,

Post a photo, I'd be interested in seeing your fuselage at the stage it's in?

[Target]

3M 77 sprayed onto whit beaded styrofoam,  blue extruded styrofoam, pink extruded styrofoam, while EPP foam, or black EPP foam does not melt it.   I don't know about this "377"    Did you mean 3M 77??   It will not melt the foam.   Don't spray on enough to run or puddle, just a fine mist is all that is needed.

That's because he's in California, as am I, and you're on another state.
The California version of 3m77 uses acetone as the carrier, other states use hexocyclene (?), which doesn't melt foam.
And, we have a lot more traffic...

[dave siegler]

look for 3m 78 if you can get it.  It's foam safe, but the non cali 3m 77 I have doesn't have acetone and doesn't melt foam

[Tim Thompson]

Yes I ment to say 3M77. Stupid phone.

But some 3M77's will melt foam and others won't despite having the same part number and color of can. Yes color matters,sometimes. At least here in California it does.

The Glidden Gripper primer does a much better job then the contact sprays do. The contact spays will come apart after a period of time, and I'm basing this on the old 3M77 spray that we had many years ago as well as the newer versions. The Gripper stays glued together.


Tim Thompson

[Tim Thompson]

Two pieces of construction foam glued together with Gripper. No sign of it seperating

[Steve Hines]

Has anyone tried to sheet wings with it.

Steve

[Target]

377 may or may not melt the  foam. A lot of us have been using  Glidden  " Gripper " primer.  Sounds crazy  but it  works!  Weight it down for 24 hours and your good to go.

The 3M purple 100 sandpaper works great on Home  Depot  white beaded foam. I've done it for years, no problems.

Tim Thompson

Tim-
Is that glidden product only in a brush or roll on product, no aerosol??
I'm always looking for new products, but I would think it may be hard to apply thinly.
Are you thinning it with something, and, are you just using it as a glue when wet, sticking the pieces together, and not like you would a contact cement like 3M77?

Thanks,
Chris

[Randy Powell]

I cut a wing out of gray structural foam. Worked pretty well.

[Pat Chewning]

Has anyone tried to sheet wings with it.

Steve

Yes, I have sheeted wings with it (3M 77) and it works great on obechi or balsa sheeting.

[Tim Thompson]

It's a brush on or roll on.
I don't thin it.  It is wet like a glue. You must weight it down and allow 24 hours to  cure.

Don't think it would make a good glue for sheeting, since it requires weight or pressure to work properly. If you had a hollow wing ,it would come out  flat !

Tim

[Target]

Thanks Tim.
R,
Chris