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Feb 05, 2013, 06:00 PM
Registered DLG addict
NighthawkF-117's Avatar
I would stay away from blue foam as I've heard when you cut a core with it, it likes to warp. This is due to the way it is extruded at the factory. I use pink foam and have never had any problems with warping or strength.
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Feb 05, 2013, 06:26 PM
Detail Freak
target's Avatar
I have cut plenty of blue foam cores, and none of them warped.

Its not the color of the foam that causes warps.

R,
Target
Feb 05, 2013, 06:29 PM
Master of the Wind
G Norsworthy's Avatar
I've been skinning 1/8" off the top and bottom of the blanks before cutting the cores. Most of the residual stress is in the skin and if you take that off it should not warp.
Feb 05, 2013, 06:36 PM
Master of the Wind
G Norsworthy's Avatar
All the really big planes I have built were made with 40 lb foam from Whitecap. I would be reluctant to make something this big with 25 lb foam as the finger dent resistance is not that good. 60lb will work also but is trickier to cut.

https://www.rcgroups.com/forums/show....php?t=1256550

https://www.rcgroups.com/forums/show....php?t=1073259

Also check out this thread for how to make a big hi aspect wing.

https://www.rcgroups.com/forums/show....php?t=1149551
Feb 05, 2013, 06:37 PM
Detail Freak
target's Avatar
Quote:
Originally Posted by G Norsworthy View Post
I've been skinning 1/8" off the top and bottom of the blanks before cutting the cores. Most of the residual stress is in the skin and if you take that off it should not warp.
^^^^^^
+1.
Also, using the least thick plank of foam that suits your needs is helpful as well.

If a plank seems curved before using for a wing core, I usually find the concave side and sand the high edges a bit with some 60grt on a block, until it sits well on the bench.
Then, slice off the convex top to flatten it.
Then, flip over and slice off a bit more to flatten that.

Then you should have a true, flat, relaxed blank to work with.

It does appear that the pink foam of the same density both cuts better and produces less hairs than the blue foam though....

R,
Target
Feb 05, 2013, 07:47 PM
Registered User
Quote:
Originally Posted by G Norsworthy View Post
I've been skinning 1/8" off the top and bottom of the blanks before cutting the cores. Most of the residual stress is in the skin and if you take that off it should not warp.
What he said This is good practice with most any material you want to shave down . Even with metal on a mill


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