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Old Jul 09, 2015, 05:58 PM
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Help!
Foam cored wings

When I go to buy foam for a balsa sheeted wing , what do I ask for? There must be all sorts of types and densities!
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Old Jul 09, 2015, 08:32 PM
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My understanding is and my dlg and gliders use blue foam, its the best for shaping or sanding qualities and is not bad on weight it's insulation foam and used to be available at bunnings , tho it seems it could be a funny yellowish colour these days
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Old Jul 09, 2015, 08:37 PM
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No need to ask, just head to you local Bunnings and pick up a block....

See the last 2 pages of this thread...

http://www.rcgroups.com/forums/showt...light=bunnings

Blue, pink, yellow... same stuff.
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Old Jul 09, 2015, 09:03 PM
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Quote:
Originally Posted by oziflyer View Post
No need to ask, just head to you local Bunnings and pick up a block....

See the last 2 pages of this thread...

http://www.rcgroups.com/forums/showt...light=bunnings

Blue, pink, yellow... same stuff.
NOT TRUE!

Depending on what type of wing you're making, you'll want to use heavier density stuff like XPS foam (extruded polystyrene), or SL (superlight) polystyrene.


If you're building a sport/aerobatic model, with a reasonably thick wing, you'll want to use SL foam, and sheet it with balsa, obechi, thin ply, or even card! the sheeting gives the strength to the wing, and really, the core is just there to hold the sheets apart so you want to have something as light as you possibly can.
This type of wing looks like this:



If you're doing a sloper, or DLG style wing that's bagged, then XPS is what you want. the higher density gives the wing some ding resistance, becuase if you distort the glass outer skin too much, you'll have a spot were the wing can buckle.
Bagged wings are generally done like this:



Choose your wing styles and takes your choice!!
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Old Jul 10, 2015, 06:34 AM
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Quote:
Originally Posted by oziflyer View Post
Blue, pink, yellow... same stuff.
IT'S PARTLY OF TRUE!
Depending on who you get your foam from will depend on the colour you get, its only a die that gives it the colour.
It is essentially all extruded polystyrene, but there is a large range of densities and cell structure.
The rule is: If you want a light plane, use light foam. If you want a heavy plane, use heavy foam.
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Old Jul 15, 2015, 02:58 AM
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Differences with Blue and Yellow

Some suppliers have replaced the Blue foam (insulation foam made by Dow) with a yellow product SUPPOSEDLY having the same qualities/characteristics.
However, its not the same and it cuts differently and is kinda stringy. We have used the yellow for a few builds but now given it the flick
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Old Jul 15, 2015, 05:36 AM
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I disagree. We have cut A LOT of wings (hundreds) with with the blue and the yellow foam and found it to be the same. We did have an issue with the quality of a couple of sheets that we got, it had lumps in it that the wire would catch on, it also had air bubbles through it, we changed to a higher density and the quality is much better.
We found that the air bubbles helped bond the skins to the foam because the adhesive would go into the bubbles giving a better bond. I now run a knife the length of the cores and at 45 deg, about 3mm deep, it gives a better bond and also acts like a small spar.
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Old Jul 15, 2015, 07:49 PM
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Wow, sounds like you're one step away from the 'resin nails' in coremat™ that bond the top and bottom skins together
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Old Jul 22, 2015, 10:11 PM
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Its like chalk and cheese!!!!
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Old Aug 01, 2015, 04:48 AM
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Does anyone in Australia (or Perth preferably) cut foam cores to order?
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Old Aug 01, 2015, 05:08 AM
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Off The Edge Sailplanes do them, but we are on the east coast.
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Old Aug 06, 2015, 02:39 AM
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Quote:
Originally Posted by Scaledown View Post
Does anyone in Australia (or Perth preferably) cut foam cores to order?
I think ijr or pnb mentioned they can cut them try asking on perth slope soaring mines awhile away from finishing (CNC one) got sick of making templates.
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Old Aug 06, 2015, 06:15 AM
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offtheedge.com.au
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Old Aug 17, 2015, 05:13 AM
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Scaledown,
What cores do you want cut?

What Airfoil, 1/2 span, cord, tip...?

I'm in Perth
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Old Aug 18, 2015, 12:29 AM
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Quote:
Originally Posted by mrmick77 View Post
I think ijr or pnb mentioned they can cut them try asking on perth slope soaring mines awhile away from finishing (CNC one) got sick of making templates.
Its nice of you to offer your services to the kind people on this forum.

Glad to see you helping..
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