Foam construction...

Butters · Post by **Butters** » Wed Jun 10, 2009 2:30 am

...as in, what kind of foam? Sources? Hot wire or carving knife? Workability? And what kind of filler/surfacer/putty can/do you coat it with?

Voyager-74656 · Post by **Voyager-74656** » Wed Jun 10, 2009 3:22 am

Interested in this as well...

Umi_Ryuzuki · Post by **Umi_Ryuzuki** » Wed Jun 10, 2009 3:37 am

I use the blue or pink styrene house insulation foam.
Shape with a snap blade, and sand paper.
Fiberglass using epoxy resins. Then sand fill and prime.

http://www.rcgroups.com/forums/attachme ... tid=937189

http://www.rcgroups.com/forums/attachme ... tid=522526

http://www.rcgroups.com/forums/attachme ... id=2561200

seam-filler · Post by **seam-filler** » Wed Jun 10, 2009 4:31 am

An alternative coating is AVES paste - probably more suitable for smaller models.

Although this is a UK site, here is some more info about working with foam....

http://www.barrule.com/workshop/images/ ... /index.htm

Joseph C. Brown · Post by **Joseph C. Brown** » Wed Jun 10, 2009 5:48 am

Here are my 'Scratchbuilding With Foam' class notes that will download as a Word doc:

http://www.starshipmodeler.info/wfest2k ... ss2003.doc

By no means the complete (or The Final Word) on the subject, but reasonably useful.

USSARCADIA · Post by **USSARCADIA** » Wed Jun 10, 2009 9:59 am

They don't stock pink/blue foam sheets here in SoCal, and you might find the same up your way Bill. I've even asked my supplier about it and get a blank stare.

modelnutz · Post by **modelnutz** » Wed Jun 10, 2009 10:03 am

A very nice alterate is sign making foam...urethane foam that is.....commonly used by sign makers.
They often have scrap pc's. which are quite usefull.
Poltester resin will not harm it.

Use breathing protection tho....the dust is nasty.

Rogviler · Post by **Rogviler** » Wed Jun 10, 2009 10:50 am

modelnutz wrote:A very nice alterate is sign making foam...urethane foam that is.....commonly used by sign makers.

Am I just crazy or does this stuff normally retail for $100+ per 4'x8' sheet?

Getting scraps is a great idea.

-Rog

Dr. Yo · Post by **Dr. Yo** » Wed Jun 10, 2009 1:24 pm

Insulation foam is markedly cheaper, but I gather its not as robust
as urethane foam-but its amazing how long a single sheet will last.

A simple battery-operated hot wire will run you about 9-10 dollars
at Micheals or Hobby Lobby. You can get better cutters that run on
household current, but they run upwards of thirty dollars to start.
I do use knives ( the holy #11, which, as it says in the book of Aves
" ...shall cleve thy material, and yea, the tips of thy fingers if thou
dost not keep them sharp and pay attention..." ) but for cutting
involved shapes I like the hot wire a little better.

bluesman · Post by **bluesman** » Wed Jun 10, 2009 2:50 pm

Where do get it? Any home improvement store...Lowes or Home Depot.

Ya got yer blue foam and yer pink foam.

As far as cutting rough shapes ....get a Woodland Scenics wire cutter.

For more advice...see Joes handout.

I don't recall a hunk of foam being 100 bucks...the last 4 by 8 sheet of foam I got was about 15 and change. To get it to fit in da car I scored it with a utility knife and popped it into sections.

Rogviler · Post by **Rogviler** » Wed Jun 10, 2009 3:16 pm

bluesman wrote:I don't recall a hunk of foam being 100 bucks...the last 4 by 8 sheet of foam I got was about 15 and change. To get it to fit in da car I scored it with a utility knife and popped it into sections.

Same here, but for styrene (blue or pink) foam. Seems like someone said they found the urethane foam at a farm and home store and it was up around $100 a sheet. Just curious if anyone found it for less.

-Rog

wetphoenix · Post by **wetphoenix** » Wed Jun 10, 2009 3:32 pm

I use my router, my bandsaw, my scroll saw. dollar store box cutters,disc sander,belt sander, palm sander and sand paper.

I came into a supply of heavier white foam which sands very smooth, almost paintable smooth. I rough shape and finish with bondo to make a blank for vaccume forming...

Scale Solutions · Post by **Scale Solutions** » Wed Jun 10, 2009 8:45 pm

You can use normal white expanded polystyrene, you just have to seal it before you put fiberglass near it, a few good coats of acrylic paint or latex or cling wrap or aluminum foil . The upshot is if your trying to make something hollow quick you just tip some turps in the end after fiber glassing it and eat the foam out.

Wayne Pugh
Scale Solutions

rocketrider · Post by **rocketrider** » Wed Jun 10, 2009 11:50 pm

HDU (High Density Urethane) board is different than the insulating foams. HDU is used in the sign industry to replace wood substrates because it won't rot or decay.

From my local sign supply store regarding "Sign Foam 3"

Sign Foam3 is a closed-cell, high-density urethane (HDU) sign board which is lightweight, yet strong and durable. Ideal for outdoor signage, Sign Foam3 is easily sandblasted, routed, carved or saw-cut. It is chemical resistant, 100% waterproof, unaffected by temperature, and will not rot or decompose. After proper priming, Sign Foam3 will accept virtually any paint.

Its not cheap...
4ft x 8ft x 1in - $178.62
4ft x 8ft x 1-1/2in - $255.94
4ft x 8ft x 2in - $322.59
4ft x 8ft x 3in - $473.22
4ft x 8ft x 3/4in - $143.96

To find a sign distributor near you go here:
http://www.signfoam.com/distributor.html

Glen

Post by **onezero** » Thu Jun 11, 2009 1:14 am

USSARCADIA wrote:They don't stock pink/blue foam sheets here in SoCal, and you might find the same up your way Bill. I've even asked my supplier about it and get a blank stare.

They don't insulate in California?

Go to the local Home Despot or Lowes. Look for this:

http://www.homedepot.com/webapp/wcs/sto ... 075+527397

macfrank · Post by **macfrank** » Thu Jun 11, 2009 8:57 am

onezero wrote:
They don't insulate in California?

Not in Southern California and at least not with blue/pink foam, or anything similar.

The blue and pink foam that I have I got from a friend back in Astronomy; they bought several sheets to insulate some electronics, and they were "imported" from out of state.

Umi_Ryuzuki · Post by **Umi_Ryuzuki** » Thu Jun 11, 2009 1:39 pm

macfrank wrote:
onezero wrote:
They don't insulate in California?

Not in Southern California and at least not with blue/pink foam, or anything similar.

The blue and pink foam that I have I got from a friend back in Astronomy; they bought several sheets to insulate some electronics, and they were "imported" from out of state.

How do houses keep the cool air from migrating to the hot air?
No wonder California has energy issues... It wouldn't take as
much energy to keep a building cool if they insulated the walls
to keep the cool air in.

compucrap · Post by **compucrap** » Thu Jun 11, 2009 2:00 pm

Umi_Ryuzuki wrote:
macfrank wrote:
onezero wrote:
They don't insulate in California?

Not in Southern California and at least not with blue/pink foam, or anything similar.

The blue and pink foam that I have I got from a friend back in Astronomy; they bought several sheets to insulate some electronics, and they were "imported" from out of state.
How do houses keep the cool air from migrating to the hot air?
No wonder California has energy issues... It wouldn't take as
much energy to keep a building cool if they insulated the walls
to keep the cool air in.

they likely use the standard insulation material used in home construction, fiberglass blankets. Its cheaper, comes in long rolls that are easy to install and make your hands itch like crazy is you don't wear gloves.

There are MANY forms of insulation for buildings, don't assume they use nothing at all just because they don't use one of the more obscure (and expensive) materials.

macfrank · Post by **macfrank** » Thu Jun 11, 2009 2:51 pm

compucrap wrote: they likely use the standard insulation material used in home construction, fiberglass blankets. Its cheaper, comes in long rolls that are easy to install and make your hands itch like crazy is you don't wear gloves.

That's what's used here. Rolls of yellow fiberglass blankets.

I still have a few large chunks of both the blue and pink foam, if anyone in the West LA area wants them.

Antenociti · Post by **Antenociti** » Thu Jun 11, 2009 3:05 pm

modelnutz wrote:A very nice alterate is sign making foam...urethane foam that is.....commonly used by sign makers.
They often have scrap pc's. which are quite usefull.
Poltester resin will not harm it.

Use breathing protection tho....the dust is nasty.

commonly called "foamed-PVC" in the UK I believe rather than an extruded polystyrene?

its excellent stuff - build tonnes of wargames structures out of it and it can be carved and sanded nicely. wont crush in the pressure pot either.

------------------------

didnt california ban all forms of extruded polystyrenes (styrofoam, foamular, depron etc) because of "health" reasons...such as it giving off hydrogen cyanide under even low temperatures? (70 degrees C and upwards?)

Chacal · Post by **Chacal** » Thu Jun 11, 2009 4:16 pm

compucrap wrote:
Umi_Ryuzuki wrote:
macfrank wrote: Not in Southern California and at least not with blue/pink foam, or anything similar.

The blue and pink foam that I have I got from a friend back in Astronomy; they bought several sheets to insulate some electronics, and they were "imported" from out of state.
How do houses keep the cool air from migrating to the hot air?
No wonder California has energy issues... It wouldn't take as
much energy to keep a building cool if they insulated the walls
to keep the cool air in.
they likely use the standard insulation material used in home construction, fiberglass blankets. Its cheaper, comes in long rolls that are easy to install and make your hands itch like crazy is you don't wear gloves.

There are MANY forms of insulation for buildings, don't assume they use nothing at all just because they don't use one of the more obscure (and expensive) materials.

In SoCal you're more likely to run across good foam in surfboards. If you can find a 'board maker, he'll have scraps left over (they cut the board shapes out of rectangular blocks of foam, so the 'corners' are discarded.)

macfrank · Post by **macfrank** » Thu Jun 11, 2009 4:23 pm

Antenociti wrote: commonly called "foamed-PVC" in the UK I believe rather than an extruded polystyrene?

I bought a sheet of foamed PVC here in California and it is fantastic stuff - some plastic cements will weld it quite well. It wasn't that expensive either.

It blends well with styrene. Here's a 1/350 Bell D2064 that I scratchbuilt. The upper fuselage is made from the foamed PVC.

Frank

macfrank · Post by **macfrank** » Thu Jun 11, 2009 4:25 pm

Chacal wrote: In SoCal you're more likely to run across good foam in surfboards. If you can find a 'board maker, he'll have scraps left over (they cut the board shapes out of rectangular blocks of foam, so the 'corners' are discarded.)

Not any more! The primary maker of the surfboard foam went out of business a year or two ago. I got a corner scrap years ago, and I still have a large chunk. It's much easier to work with than the blue insulation foam, and common glues won't attack it (nothing seems to attack it).

modelnutz · Post by **modelnutz** » Thu Jun 11, 2009 4:49 pm

macfrank wrote:
Chacal wrote: In SoCal you're more likely to run across good foam in surfboards. If you can find a 'board maker, he'll have scraps left over (they cut the board shapes out of rectangular blocks of foam, so the 'corners' are discarded.)
Not any more! The primary maker of the surfboard foam went out of business a year or two ago. I got a corner scrap years ago, and I still have a large chunk. It's much easier to work with than the blue insulation foam, and common glues won't attack it (nothing seems to attack it).

That stuff was called "Clark Foam"...also a Urethane foam.

macfrank · Post by **macfrank** » Thu Jun 11, 2009 5:28 pm

modelnutz wrote: That stuff was called "Clark Foam"...also a Urethane foam.

Is there an equivalent... other than just getting urethane foam? Something with a smaller cell size. The "Clark Foam" would soak up CA like a sponge.

modelnutz · Post by **modelnutz** » Thu Jun 11, 2009 6:39 pm

I'll start digging into my past research on foam materials and suppliers...I think that I have a link or two.
One supplier that jumps to mind is "Aircraft Spruce and Specialties"
Look em up.

The stuff used for Disney style outdoor figures is a type of refridgerator foam.
Still, it's a urethane based foam.

CNC proofing foam is also urethane ( Ren Foam is one type )
All are kinda pricey...sign maker scrap is the best you can do.
Also, check out companies that supply materials to the fiberglassing world.

There's also a urethane foam available at Home Depot type stores....look for the yellow colored sheet foam that's covered on both sides with foil.
That's urethane as well...but it's kinda weak...usable, but soft...not real dense.

You might try using the can style foam. found at home depot type stores as well...used for gap filling and weather proofing...that's urethane as well

The only issue is the density...too low right out of the can....however..

there may be a trick to try.
Foam density can be increased by constraining the area allowed for foam to expand.
For example...if standard rise = 1/2 lb. per cubic foot and yields a block 2 cubic foot in dim....then the same amount of foam shot into a box half that size will yield a foam of double the density.

Only trouble is the power behind the "blowing" foam....HUGE !

Perhaps a very strong box ???????

Be careful out there kiddies...we're treading in Mythbuster's area here.
Big amounts of power can be released !
Respect the foam...it's sticky and hot when rising !

modelnutz · Post by **modelnutz** » Thu Jun 11, 2009 6:42 pm

Ooops...sorry Mac...forgot to address your comment about super glues soaking in.

I found through trial and error ( mostly error

)
That the best way to glue is to coat both mating surfaces with some super glue...let the glue set up fully...scuff sand...and then glue as normal.
The first layer of glue stops the second application of glue from soaking in and preventing a good bond.

Joseph C. Brown · Post by **Joseph C. Brown** » Thu Jun 11, 2009 7:09 pm

Also, let's not forget Sintra - handy stuff!

http://www.solarbotics.net/starting/200 ... intra.html

I scratchbuilt my Warhawk from this; carves easily, sands great, accepts CA and MEK based glues. Not bad for foamed PVC!

Umi_Ryuzuki · Post by **Umi_Ryuzuki** » Thu Jun 11, 2009 9:12 pm

macfrank wrote:
Chacal wrote: In SoCal you're more likely to run across good foam in surfboards. If you can find a 'board maker, he'll have scraps left over (they cut the board shapes out of rectangular blocks of foam, so the 'corners' are discarded.)
Not any more! The primary maker of the surfboard foam went out of business a year or two ago.
...

Nope, General Plastics still seems to be in business...

http://www.generalplastics.com/
Your local distributor may be a different story...

rocketrider · Post by **rocketrider** » Thu Jun 11, 2009 10:23 pm

Joseph C. Brown wrote:Also, let's not forget Sintra - handy stuff!

http://www.solarbotics.net/starting/200 ... intra.html

I scratchbuilt my Warhawk from this; carves easily, sands great, accepts CA and MEK based glues. Not bad for foamed PVC!

I have a ton of this in my garage, never thought about using it to build, I was saving it for diorama bases.

UPDATE:
Just for giggles I sent away to SignFoam for a free sample kit. they sent 3 7" x 7" samples of the board, soft, medium and hard density, + some adhesive (4-4'Diphenylmethane Diisocyanate).

Pic 1
Pic 2

May make something out of it for fun.
Glen