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Jun 07, 2016, 03:34 PM
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A lot of the free plans use 6mm and then interlock everything. I haven't seen a "thickness planer" for foam like there is for wood. Maybe it would work on foam. I don't know.
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Jun 07, 2016, 03:55 PM
springer's Avatar
Probably won't work on DTF. The actual foam cell structure (small cells with thin walls) and polymer recipe is not stiff enough to take the force of a blade without balling up unless it is scalpel sharp. Tough to find a sheet wide blade like that. Hot wire is the best bet, and a gravity feed. I used it to slice EEP, and it worked "ok", lots of strings, but I think styrene will be less stringy. I would still use double thick where ever I could get away with it. It's easy enough to increase slot width, and determine the "reference surface" and insure that slots are aligned to it so the plane builds right.
Jul 20, 2016, 10:53 AM
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davereap's Avatar
why worry , just do the build with whatever is available
6mm depron or 5mm $tree board paper on....., hardly any difference...
with the paper on... their weights are very close..
depron is a higher density foam, heavier and more brittle.. $tree is paper covered , made stiffer and tougher because of the paper..
you can prevent cracking on depron and make it stiffer by using a tape covering, but that adds weight..
Simply build with either.. you wont really notice any difference
only remove some paper if you need curved surfaces.. like flitetest does
You can remove it all if you want ultra light weights, for small models, but then its not as strong.
however on small models a lot of strength is not required
cut slots to suit the material you've got...
Last edited by davereap; Jul 20, 2016 at 11:06 AM.
Jul 20, 2016, 11:43 AM
Registered User
Spoken like a man who has Not used Dollar Store Foam.
At least as sold in North America :-)
The paper sheathing pretty well falls off the foam substrate at the merest whiff of humidity.
That, besides its almost free price, is why I use it.
Not great, if relying on the paper as a part of the foam structure / build

On the other end of the spectrum: Graphics Quality foam boards seem to require a chisel to remove the paper.
But those are expensive and heavy . Too heavy IMO.

PS: Given the increasingly Appalling quality of 1$ foam I've been buying the 'next quality level up" of Adams Ready board from Michaels'
Costs More but they often have 2 for 1 sales So I've a decent stockpile. Note that the Paper is not as easy to remove (1/2 hour water soak does "fine' tho) But the foam is ripple free.
Last edited by Bare; Jul 20, 2016 at 11:50 AM.
Jul 20, 2016, 10:44 PM
Registered User
Smaragos's Avatar
Originally Posted by Bare
Spoken like a man who has Not used Dollar Store Foam.
At least as sold in North America :-)
The paper sheathing pretty well falls off the foam substrate at the merest whiff of humidity.
That, besides its almost free price, is why I use it.
Not great, if relying on the paper as a part of the foam structure / build
It's my understanding that if you use Minwax (regular, not the water-based) as a light coating on the paper, the humidity problem goes away. The Flite Test bunch as a video or two on this.
Jul 21, 2016, 06:46 AM
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flypaper 2's Avatar
The last batch of Elmers , Ross' Craft Board I bought from Dollerama is just about impossible to get the paper off , wetted or dry. I've been using it lately with the paper on for the strength , for some later projects. Takes paint very well. Couldn't do this with the older stuff.
It says ( Distributed by Elmers Products Canada ) on the label if you're looking for it.

Jul 21, 2016, 09:56 AM
flyin' fool
goldguy's Avatar
No more Depron.
Jul 21, 2016, 10:02 AM
flyin' fool
goldguy's Avatar
And I don't care. I'm an EPP man.

If your going to all the trouble to built it, why not build it to last way past your' lost interest level'.
Jul 21, 2016, 12:00 PM
Registered User
Sure EPP can be tough
But it's a PITA to source.
Thick sheets /blocks are too often glued together thin sheets.. tough to hot wire passably
DOW foam is great for most everything, I've found.
Just can't step on a model made of it... without damaging it
Last edited by Bare; Jul 21, 2016 at 12:05 PM.
Jul 21, 2016, 01:53 PM
flyin' fool
goldguy's Avatar
Our local hobby shop stocks EPP at a cheaper price than we pay if we order it on our own from RCFoam, as he get free shipping and picks it up south of the 49th on the mainland. Our last big GROUP order, about $400 cdn, would have cost almost twice his price.

Never ever had sheets glued together from the three different suppliers I've personally dealt with.

We can cash, smash, bash, trash and mash our models, just dust them off and back off punchin' holes in the clouds. Oh................ and walk and drive over them too.
Jul 21, 2016, 04:29 PM
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flypaper 2's Avatar
LOL Well put Frank.
Straight from the heart.
Jan 14, 2018, 01:40 AM
Registered User

Thinning DTF or Depron and bending.

Other ideas - I have been thinning DTF and Depron for curved areas and thinner lighter model wings etc.
I use a simple DIY Hotwire bow and cut the foam sheet using any 12 volts (2 - 3.5 Amps minimum supply) nichrome wire 26AWG (0.4mm diameter)
I place the nichrome hotwire on spacers (drill bits or wire or whatever) on top of a flat tile or piece of glass.
Sortening the length of where the 12 volts supply connects (aligator clip) onto the nichrome wire bow will make it hotter or cooler for cutting.... just experiment.
Place the foam on the glass with a flat thingy (book or whatever) on top and slide it throught the wire at a consistant speed which it wants to cut and you will get an even thickness sheet.
24 inches wide cut is slow and uses 1.8 amps
12 inches is hot and fast and uses 3.5 amps
I cut to 0.7mm for my indoor planes or 2 - 3mm for parkfly fuses.

Bending tight curves without cracking.
Submerge the foam in a tray of boiled water then curve around anything about half the radius as you need and leave some tape or rubber bands around it for a while.
Latter when cooled it will flex back a little, closer to the desired curve.
Jan 14, 2018, 04:43 AM
flyin' fool
goldguy's Avatar
Good idea, thanks for posting.

I cut my onw EPP sheets from slabs too.
Jan 14, 2018, 08:33 AM
jackerbes's Avatar
Another foam that is or at least was much used is the 1/4" +/- thick Dow Protection Board III foam that is intended for use in insulating buildings. That foam comes in bundles of twenty five 24" x 48" sheets that are folded along the 48" edge to make one continuous length of foam. We most often call it FFF for fan folded foam and get it at places like Home Depot and Lowes.

The FFF has a thin plastic membrane glued to one side and the other side is bare and slight porous and slight wavy foam.

It is most often used in multiple layers to build wings with steps like the Kline-Fogelman of KFm# airfoil builds that are much described and detailed in the ** Kline-Fogleman (KFm) Airfoils - Building/Flying Discussion ** thread .

Go to that thread and use the Thread Tools menu to "Show Attachments in this Thread" and you'll see hundreds of images of many different type of aircraft made with various foams. And much of the detail on how to do it will be there too.

We all have preferences and habits for using FFF, mine are to leave the plastic skin on as much as possible and to embed spars or stiffeners of various types between the layers of the KF foam. The folded edge between a pair of the sheets makes a nice leading edge and additional pieces of foam are cut to create multiple steps for KFm wings and build one piece wings of a 48" span. And with clever work, staggered joints, and various types of joiners the edge to edge or " butt joints" can be made to build wider wing spans. My personal best is a 96" wing with an 8" chord for a glider.

Another way to improve the strength of FFF is to glue small dowels or bamboo skewers to the leading and trailing edges of wings and control surfaces to strengthen the part and impart some resistance to it being "dinged" or easily damaged. This is done with the glues described in the following paragraphs.

The FFF layers are bonded to each other with Gorilla Quick or the slower setting reqular Gorilla glu (AKA "GG" or "GQ" glue) that is spread thinly over the water spritzed open side of the foam. The water causes the glue to foam a little and that is where the penetration and strength is gotten.

After the layers are glued together I usually cover the wing with 2.2 mil or so thick colored package sealing tape to give the wing color for visibility in flight and a little more eye appeal. For the tape covering, if it is applied over the plastic skin side of FFF it adheres very well. For the open foam or porous side of the foam I spray a light coat of the Duro #01-01088 General Purpose or 3M 77 aerosol adhesive on the bare foam and then applying the tape over that once the adhesive has set up and is only slightly tacky to the touch (that only takes a few minutes).

The colored package sealing tape is the final element of strength in a multiple layer FFF wing and the contribution it makes to the wing's overall strength is not insignificant. For smaller builds you can even omit the spars between layers if you use the tape on the outside of the foam.

Go to my blog page and you'll see links to posts and threads where I have detailed the use of FFF to build wings and airplanes. And nearly all of them are still alive and well and hanging in my basement!

And anytime you spot any words of wisdom here that interest you, you can click on that persons name in the post the just made to open their blog page and see if you can get more info on the thing that interested you. As a group we are all sharing info freely here and cashing in on the work of others! And loving every minute of it!

Aug 02, 2018, 12:03 AM
vtpraerobatics.blogspot.c om
oldscooler's Avatar
I'd like to try assembling a 2 piece 106" wing with foam board. 10" root, 7" tip. I can buy 6mm 40" x 60" sheets. Any suggestions?

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