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Old Jan 20, 2007, 10:26 PM
paintz2007 is offline
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Help!

scratch built foam profile need help with weights


im plannin on buildin a profile extra-edge ish style plane for 3d outta the elmers foam board stuff

lookin at a 26-27 in long body and a 30 or so wing span

im gonna use a park 400 outrunner
20 amp eflite esc
tanic/tp lipo both weigh the same
hitec mini 6 s
and 3 futaba 3110's
plus 2 oz in wiring slash control rods

all should weigh about 8.5 oz

i was wonderin wat the foam weighs

by sq inch would be ok

please help if u have any ideas i wanna keep this as cheap and simple as possible
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Old Jan 21, 2007, 10:07 PM
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ok so now ive scaled it up 15%

to get a 30 inch length

here are some photos of a couple scale sketches i have so far
Old Jan 22, 2007, 08:02 AM
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Try to use a better FFF , Blucor , if you can find it .... it's cheaper in the long run ...try to avoid anything that you have to remove the paper off of , the foam is not as good ....Nice drawings ...
Old Jan 22, 2007, 08:29 AM
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Quote:
Originally Posted by paintz2007
plus 2 oz in wiring slash control rods
You must have some heavy wire & control rods there

I recently built a 28" foam 3Der made from EPP with a full fuz - the AUW was 6.5oz....8.5oz for the equipment alone seems overkill to me.
Old Jan 22, 2007, 10:22 AM
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From the looks of your drawing this plane will fly great and do 3D with your 400, but you must use foam, not foam board.
Old Jan 22, 2007, 04:27 PM
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If it wasn't for the foam
Quote:
Originally Posted by paintz2007
i was wonderin wat the foam weighs

by sq inch would be ok
foam-fly.com reports the following:
White Foam-Core with the paper peeled off:
0.6 Oz/SqFt
Georgia Pacific BlueCor with the skin:
0.75 Oz/SqFt
Black Foam-Core with the paper peeled off:
0.8 Oz/SqFt
Amocor Green Foam with the skin:
0.95 Oz/SqFt
Owens Corning Pink, has no skin:
1.0 Oz/SqFt
White SturdyBoard with the Paper on:
2.0 Oz/SqFt

I use a generic foam board, and peel the paper off. The result is a depron-like foam that weighs exactly 0.6 oz./sq. ft. Some here have told me it is depron, but I don't know for sure. It's also lighter than any other option I'm aware of. BlueCor is 25% heavier. I've built a few planes with it, from high-speed prop-jets to DLG's. It's great to work with, holds up well, and repairs easily. It can be strengthened with CF and/or packing tape, where needed. Avoid iron-on coverings due to warpage. If using packing tape, don't pull it real tight - just snug.

Peeling the paper isn't too bad. It's not fun, but I can peel enough for a plane in under 30 minutes. My local Michael's craft store carries Elmer's and an unknown brand -- 3/16" sheets are about $2 ea. And they have 1/2" thicknesses for about $4 a sheet. If you have easy access to this stuff, by all means try it out. You won't be disappointed.

Blue-cor is very popular, but I've never tried it, because:

1. It would take me years to build enough planes for it to pay off.
2. I don't want to store the unused foam for all those years.
3. We use foam board at work for mounting maps, and just the scraps provide more foam than I'll ever need.
4. The bundles I've seen at Lowe's are all wavy. There's probably a solution to that, but 1, 2, and 3 prevent me from getting that far.
Old Jan 22, 2007, 10:18 PM
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thanks all

soundman my 2.5 oz is a very rough estimate even with that my prospected wing loading about .06 oz/in square
Old Jan 24, 2007, 06:50 AM
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i have the full size plans all drawn out... waitin on some time to go to the store to get some foam

the plans are actually a couple inches shorter than the paper their on

i think im gonna cut them out and get them laminated so they dont get screwed up...

i have about 7 hours in design alone already
Old Jan 29, 2007, 10:00 PM
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hopefully off to get foam this weekend
Old Jan 30, 2007, 05:03 AM
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the rudder looks a bit small for 3D?
Old Feb 02, 2007, 10:50 PM
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got the foam cut out

runnin to the lhs tomorrow to get some sxs

im just gonna swap my e flite 400 and 20 a esc and rx over from my cessna but leave the sxs in that one

all my gear except sxs are removable (velcro) except the sxs so there just gonna chill in there

ill have build pics up when im done

all in all i found a new joy in the hobby in scratch building...

i just hope it will fly

Old Feb 04, 2007, 09:25 AM
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If it wasn't for the foam
Did you peel the paper off the foam? If not, the foam is 2 oz./sq ft., vs. 0.6 oz/sq ft. if you peel it off.
Old Feb 05, 2007, 12:05 AM
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i tried some peeled off easy but was extremely weak...

i hope to maiden tomorrow in our 5 degree f weather...

no school tomorrow cause of wind chill
Old Feb 05, 2007, 12:16 AM
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still more pics


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