tacomaker Show full post »
tacomaker
I notice the paper tears as well. But what I do to stop this is do multiple passes with a sharp knife. Don't cut through the whole thing with one cut. Do like 3-4 cuts, first cut through the paper, then foam then other paper side. also make sure the foam is sitting on a flat surface and supported well underneath.

My cuts are clean when I do this.
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cheeto_rc
Argonath,
ya the paper tears for me too! i was pretty upset when this happenend to me as i started cuting out the fuse of the f-5 glider pdf. this was my first time scratchbuilding and i was using this glider for a project. i figured that is was the paper not being firmly attached to the foam so when doing a straight cut, the paper started to peel back and bunch up at the knife. What i found works for me is doing a sort of sawing motion with the blade. When i "saw" up and down as i pull back it keeps the paper from bunching up and cuts it really smooth. Usually when i do this however, it does not quite cut the bottom layer of paper so i do the saw technique, the go back and do a standard straight cut and it works perfectly! nice straight cuts all the time. It takes a bit longer (2x the cuts) but i find its worth it because i like things to be exact. hopfully this makes sense and works for you! good luck!
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Jbirky
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actually, I got two 20" x 30" Elmer's foam boards at 3mm and removed the paper. I found that cutting it with the paper backing causes the foam to tear instead of cut.


You need a sharper knife and/or better tecnique.

You need a utility knife that uses cheap, disposable blades. I recommend you get one like the Stanley I use [See Attached]. When I say LIKE, I do not mean it has to be Stanley, but you want a utility knife where you can change the blade without the need for a screw driver or other tools.

This one, you slide the bade all the way forward then press and hold a yellow Tab and it releases the blade. You can then flip it around using the other side. It also opens with room inside to hold about 10 spare blades, which is 20 being you flip them

Finally, you buy a bulk package of blades from your hardware store. I get about 50 at a time for about $5, and I swith them before they get dull and the foam tears.
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Jbirky
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What kinds of glues are you guys using for the foam boards. Since it has paper on the outside, would regular paper glue do?


Hot glue is the best hard glue; I think. When I say hard glue, I know it is rubbery, but when you have tight joints it is hard glue.

Hot glue is only strong when the pieces are tight. That said, you can use paper glue if you can tolerate waiting hours for it to dry.
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Jbirky
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I noticed something about the foam board that I'm not liking and I can't tell if it's me, the knife I use or simply the thickness of the foam board that simply will not cut right.

it's 3 mm thick but when I cut it with a brand new x-acto knife, I noticed that the foam board tends to tear rather then cut.


An exacto knife is too flimsey. Switch to a utility knife.

Also, when you cut, you need a good cutting angle, so that you are trying to slice something not plow through it. The cutting surface of the blade should be almost parallel to the foam to be cut with a very shallow angle.

You also need a meterstick or yard stick for every cut, or it will never be straight. I personally use a T-Square and get perfect cuts (almost) every time.
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Argonath
Well, there's no more paper on my foam board. I removed it and I'm wondering if this is why. I let it soak in the tub with lukewarm water and the backing practically slid right off it on it's own.

So I'm cutting straight 3mm foam with no paper backing and this is what I find is so odd about it. A brand new X-Acto should be able to cut 3mm foam with no problem but it doesn't.

The reason I was using an X-Acto to begin with is to make more precise cuts and I know it's not likely to be the blade because if I drop a sheet of paper edge first on the blade it cuts into the paper just from the force of it falling on the blade.

It's gotta be something I'm doing or the density of the foam is too soft w/o the paper backing.
D.I.L.L.I.G.A.F.
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lakeman
I just checked out Walmert's foam board and it is 5mm thick. The designer of the plane (f-35) specifies 6mm thick board - will there be a huge difference on the wing and control surfaces strength if a 5mm foam board is used instead?
any one ?
thks
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