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Sep 21, 2007, 05:34 PM
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Foam Core cutting


I have some R-Max Polyisocyanurate 20lb density 2"foam sheets.
I tried the hotwire cutter one one and it did not appear to be able to cut it well ,it smoked and burnt the foam??

Any bright ideas?

Regards Andrew
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Sep 21, 2007, 10:10 PM
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I have no idea what that type of foam is that you describe. I can say that the typical foam that is used for hot wire cutting weighs anywhere from 1.5 to 2.6 pounds per cubic foot. If yours weighs 20 pounds per cubic foot, then that might be a problem even if you could cut it. If your foam is a typical extruded foam made by Dow or Owens Corning (blue or pink) and in the density range I describe then you should be able to cut it with a hot wire and we would need more details about your attempt before we could offer advice.
Sep 21, 2007, 10:52 PM
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Phil thanks for the reply.

Please see the attached PDF ,I am now thinking this stuff my have some kind of thermal additive (Fire retardent)?
It feels similar to the blue and pink foam nice and solid not powdery...My hot wire cutter is home made and I am currently using SS fishing leader wire to cut foam just cant seem to get any blue or pink foam around here.

Looking forward to any idea's.

Regards Andrew.
Sep 21, 2007, 11:32 PM
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Shaper Dave's Avatar
Hi Andrew,

Im not sure what Im reading on the spec sheet but it sounds like it may be a resin based foam such as polyurethane which is also used for insulation in some cases.
This foam cannot be hot wired and will just smoke and melt.

Dave
Sep 22, 2007, 12:04 AM
solastagia
kcaldwel's Avatar
...
Last edited by kcaldwel; Jan 25, 2012 at 09:40 PM.
Sep 22, 2007, 07:57 AM
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Kevin,Dave,

Thanks I think you are correct...the foam seems to stick and burn on the hot wire...
Hmm, I will keep looking ,no Home Depot in this part of the world!

Andrew
Sunny Barbados.
Sep 23, 2007, 05:43 AM
Registered User
If your foam is a light tan or brown color and came with a foil or paper coating this foam will not cut with a hot wire. test a sample with a drop of CA glue. it should take the glue without disolving. This particular foam I find very useful to make fairings or wing tips as it can be CA'd in place and sanded to shape and then covered with monocoat as the foam is not affected by the heat from the iron.
Sep 23, 2007, 12:52 PM
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How about this type of foam...has a good PSI rating and is a polystyrene foam?

Lowes sells it in Miami FL.

Really would like High-Load 60 ,does anyone have foam supply in Miami Fl.

I ship to the Caribbean from Miami.

Regards Andrew
Sep 23, 2007, 09:07 PM
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RomanG's Avatar
Quote:
Originally Posted by fishovertime
How about this type of foam...has a good PSI rating and is a polystyrene foam?

Lowes sells it in Miami FL.

Really would like High-Load 60 ,does anyone have foam supply in Miami Fl.

I ship to the Caribbean from Miami.

Regards Andrew
Andrew,
First foam you posted (Polyisocyanurate) is type of polyurethane foam, based on the data sheet it is 2 pound (per cubic foot) foam so it is not heavy but that kind of material starts to melt at 400 degrees Celsius - not good for wire cutting.

Second foam is expanded polystyrene, which has beads and does not give same finish quality as High-Load foam ( extruded polystyrene) when cut with hot wire. If you go with Type IX it should be closest to High Load 60 as far as mechanical properties. This should cut nicely with hot wire.

Roman
Sep 23, 2007, 09:30 PM
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Thread OP
Any good foam suppliers in Miami FL.

Regards Andrew
Sep 24, 2007, 08:47 AM
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If shipping foam is an option for you then you can order from anywhere. Since foam is used primarily as insulation you will have a much harder time finding it in warm climates like Miami. It is easier to find in northern climates. You may find the following links useful:

https://www.rcgroups.com/forums/show...16&postcount=4

https://www.rcgroups.com/forums/show...ar#post5252142

https://www.rcgroups.com/forums/show...ar#post6630763

https://www.rcgroups.com/forums/show...ar#post6640423
Sep 24, 2007, 04:22 PM
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Phil,

Thanks ,unfortunatly I cannot seem to find asuitable foam here in Barbados.
It looks like importing from Florida is my only option.

Thanks for the links.

Regards Andrew.
Sep 25, 2007, 08:51 AM
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David Forbes's Avatar
Andrew,
Good luck finding anything over 3/4" thick in FL. Best I can do in North FL is 3/4", Home Depot sells the pink tougue and groove and Lowe's has the blue. It is possible to cut 60" DLG cores out of this. I have some 2" pink that I bought in Ohio last summer, and I note that the cell size seems to be larger, and the foam seems crisper and stands up to sandpaper better than the t&g foam. I don't know what to attribute this to. The 2" is labeled Foamulair 150, niether of the t&g boards have a designation for density, maybe Phil knows the difference. XP-4 cores are about 2 to 3g lighter from the 2" stock, so maybe that is an indication of higher density in the t&g. By the way, the t&g comes with a saran wrap type film on it that can either be ignored or peeled off.
Dave
Sep 25, 2007, 10:49 AM
Chuck 'Em and Chase 'Em
Fly2High's Avatar
You can also use Plazamate instead of HiLoad 60. Plazamate is HighLoad but with a 1/4" wide by 1/2" dee cut on the long side along the edge so that if two Plazamates are put side by side they make a 1/2" x 1/2" drainage channel. I live in NY and this is what I was able to find locally.

Frank
Sep 25, 2007, 04:42 PM
Registered User
Quote:
Originally Posted by fishovertime
I have some R-Max Polyisocyanurate 20lb density 2"foam sheets.
I tried the hotwire cutter one one and it did not appear to be able to cut it well ,it smoked and burnt the foam??

Any bright ideas?

Regards Andrew
Polyiso is a special kind of foam which has a much lower coeficient of heat transfer which makes it perfect for insulation. But it's not very good for wings.


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