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Foamies Talk about building, power setups and anything having to do with e-powered foamy planes!

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Old 01-08-2012, 09:38 PM   #1
quorneng
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Default Is Depron a good structural material?

At the risk of being a bit controversial there seems to be view that Depron is a poor structural foam.

Surely the important issue in any airframe material is its strength to weight ratio, both in tension and compression.
As a plastic foam Depron actually has quite a good strength to weight ratio and importantly it has a surface 'skin' as well. In addition with the right glue a joint can be virtually as strong as the material itself.

So if you keep within its stress limits and retain its skin surface you can build quite complex light, strong, rigid structures with a smooth surface.
Not a bad receipt for an airframe!

To test this I made a simple 40" wing in 3mm Depron but using a conventional built up 'rib and skin' structure to replace a solid foam, part reinforced, original.
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One advantage of using a relatively thick wing skin is that it does not need so much support for it to take compressive loads.
The servos were built in making use of the ease by which Depron can be cut and glued.
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To keep the surface skin intact at the trailing edge the top and bottom wing skins were sanded on their inside edges prior to being glued down.
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The final result was a wing with a good Clark Y profile and a smooth waterproof surface.
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To complete the structural test the two wing halves were simply butt jointed together!
Nearly 50% lighter, just as strong and in aerodynamic performance a whole order better than the rather crude 'moulded' foam one it replaced.

Maybe not every bodies 'cup of tea' but to me the opportunities of Depron seemed considerable.


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Old 01-08-2012, 11:42 PM   #2
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Default

actually starting to see threads now were people are substituing it for the balsa.

i am going to do it then cover it in fiberglass for a composite structure on a LARGE plane

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Old 02-08-2012, 09:21 AM   #3
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It looks similar to the anti-static foam that electronic components often come packaged with (Chip legs often stuck into it). How rigid is it in sheet form?
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Old 02-09-2012, 09:18 PM   #4
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Default

Firstly Depron is most definitely not anti static! In dry conditions it sticks to your fingers like glue.

It actually has a surface 'skins' so for its weight it is reasonably rigid and perhaps more importantly it can also take reasonable compressive loads.
This makes it a good material for a stressed skin structure where its light weight and rigidity can be used to advantage.
This is the fuselage tail section of my electric Bachem Natter built up entirely of 3mm Depron sheet.
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It is 7" deep. 6" wide and 13" long and weighs just 1/2oz, yet is strong and stiff enough to carry the tail surfaces and the pusher motor.


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