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Jan 10, 2020, 10:34 AM
Registered User
Thread OP
Question

Surface density difference with MPF vs dollar tree vs HD Owen Corning fanfold, etc...


Hey all

I’ve been using dollar tree foam for lots of scratch building planes and wings.
I wanted to try some different material and considering model plane foam. But I would like to know the surface density (ie. grams / in^2) of model airplane foam.

Dollar tree foam is about .19 grams / in^2.

On their website (MPF) they state 2 lb per cubic ft. Each MPF sheet is 6mm. If I do some math on that I get about .12 grams / in^2.

Can anyone confirm for me if that is about correct for MPF? Is it stiffer than DTF?

Thanks!!



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Jan 11, 2020, 11:37 AM
treefinder
springer's Avatar
Dropout, sorry for the delay in answering your questions, but here goes:
I just weighed two samples of MPF and got .15625 and.1625 gm/sq in. That works out to 2.16 and 2.7 lb/cf ft respectively. Both samples were very close to .25" thick, one slightly thicker, one slightly thinner. The thickness spec we set with Adams is 6mm +0/-.5mm and the latest order is running at the high end of spec. The current run has a fine cell structure that probably increases the density a bit. B grade (which has a rough surface texture, you will see it on the website) has a larger size cell structure and has relatively lower density.

Comparing it to Readiboard or Flitetest board (same stuff, basically) MPF is thicker and significantly stiffer, due to a combination of thickness, an integral closed cell skin, and to a lesser extent to recipe differences.The DTF recipe and processing yields an extremely fine cell structure, and flexible foam. Also, if you remove the paper from it, you break all the surface cells of the foam skin, and that weakens the foam both in flex, as well as surface dent resistance; the open cells are very friable, and show imprints easily. I should note that the paper is adhered to the foam only by heat in the post processing when it is applied, which is why pulling it off it takes the outer surface of foam with it. MPF is extruded without paper, and only some heat to straighten the curve induced in extruding, so has an intact and slightly increased thickness skin. I say slightly, as it is no way a "real" skin, but it's presence does aid stiffness.

Compared to Depron, MPF is significantly more durable in the sense that it is more resistant to crash damage, many users have commented that identical planes they have built in both materials, the MPF one will survive crashes much better than the Depron one. That toughness comes with a reduced stiffness compared to an equivalent thickness of Depron, Very few folk have found that to be a problem, however. This was discussed a good bit in the RCPowers forums, and several folk expressed concerns about stiffness in those high speed propjets, but once they actually built with MPF, the concerns didn't turn into complaints. Some added CF stiffeners, while others just went with it.

If you want, PM me your shipping address and I'll send you a sample pack!

Mike Spring
Jan 12, 2020, 07:51 PM
I Look, Listen, and Learn
Timbo383's Avatar
Dropout I cant comment on the math of the density etc., but I do use a lot of dtf and mpf in my builds. The difference between the two is night and day, to what Mike has stated the mpf is far superior to dtf......but at a cost, unfortunately due to the high cost of shipping now days you do pay more per square inch for the mpf. But it is worth the extra cost for better plane builds, I usually use dtf for untested scratchbuilds and after all the mistakes and testing if I like the build I'll make one in mpf to keep.... that is until it takes too many dirt dives to repair.....
Jan 14, 2020, 04:51 PM
Registered User
Thread OP
Thanks for the replies! That was very informative and the type of info I was looking. The math was just about comparing DTF with MPF since I had no other metric to compare. So MPF is slightly lighter per surface area but much stiffer. That's exactly what I want.
(My math made it seem even lighter - but never mind my math).

I heard lots of good stuff about MPF and I wouldn't mind getting my hands on it to make a few wings but the shipping cost has really got me though. I think I'll try the HomeDepot Owens Corning foam at $50 first since I can easily pick that up.
Last edited by dropout; Jan 14, 2020 at 05:04 PM.
Jan 14, 2020, 08:28 PM
I Look, Listen, and Learn
Timbo383's Avatar
The Home depot foam though cheaper will be more brittle than the mpf and also dtf, don't get me wrong it will work ok, just expect more cracks and breaking off of pieces during rough landings. Maybe you can try to incorporate the softer dtf with the Owens Corning to make use of both the stiffness of the OC and the flexibility of dtf, maybe for a larger type of plane you can laminate the two together to get the best of both worlds. Don't know for sure how it will come out but it could be worth a try.
Jan 16, 2020, 06:55 AM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
"The quality of the Foam is remembered long after the price is forgotten !!! “ …
I remember spending big bucks on Balsa for just ONE plane , and that plane would last one crash …
Most Any foam (cost per plane) is waaaaay cheaper than Balsa … and “ a Good Thing” …
JMHO , Buy the good foam , tested , proven , sold by Modelers …
Latest blog entry: Lost plans


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