Anyone used cornstarch foam for a blank?

[blackeye]

willi's thread about dcell led me to wonder if a hollow board could be built around a temporary foam core. 

I despair the waste in shaping non-recyclable EPS, and apart from emergency flotation its ongoing function is pretty much nil.  The hollow wood and composite boards are evidence of that. 

Could one shape a giant cornstarch blank then laminate on top then inject water to disappear the foam? 

This is a method where I can understand a layup schedule using additional coring like Dcell (Carbon inside surface, Dcell middle, Kevlar/Sglass outside).

Call this the Cheezie method? (http://www.cheezies.com/static.htm) Paint it orange?

[swordfish1227]

It can be done with other foams as well, you just have to use acetone or gasoline to dissolve the foam.

I think your layup would be much more similar to a boat layup, and have to be much heavier than a standard surfboard layup. Also you will need stringers and support of some type to be able to stand on it.

[headmount]

Carbon fiber stringers?

[blackeye]

gasoline/acetone doesn't work with the waste stream thing.  I don't clean my epoxy brushes in acetone as I am working through a supply of old kids art brushes and just let them harden.  

Point taken on the stringer/bulkhead thing.  I assume the hollow boards are made with them too.  The layup proposal isn't any heavier than suggested in willi's Dcell vs carbon thread.  Except for the stringers.  And bulkheads.  And... (plaintively)... don't hollow boards have them too?  

Yeah, carbon stringers for sure.

[Celeste]

Dude, can the acetone, everything it does for you can be done as well or better with safer less toxic products.  Progressive Epoxy markets a no-solvent cleaner TA 661.  Very low vapor pressure, does not evaporate in a week.   unlike solvents, any residue left does not go hard, it hardens to a jelly.  I have used it so much to clean brushes that it gets thick with the dissolved epoxy, but it still cleans and prevents hardening.  I am sure others have something similar.

If you need thin resin, get low viscosity resin, but if you have to thin, use xylene, lower vapor pressure, slightly less toxic, still a cotoxin that makes epoxy more toxic, but better then acetone.

As for stringers and bulkheads, you can build the foam around then, stringers in longitudinal groves, and bulkheads breaking the foam into sections. 

Using cornstarch would be kind of like lost foam casting, in reverse.  It is an investment process, but not casting

[blackeye]

I'll check out that TA 661.  I have only one overbuilt paddle project to my credit so far, so lots to learn.  Keep it coming. 

I didn't know epoxy could be thinned.  I'll have to look up the specifics for the brand I'm using.   

[PonoBill]

The cornstarch notion might be worth some experimentation. Most things like this leave so much residue that the only advantage of dissolving the foam is that you get rid of the bubbles. But with a water wash it might be a different story.

If I were going to try it I'd use PVC stringers and deck supports. That way if your hull leaked and filled it would still float. That's what saved Boyum's bacon when he left the plug out of his Bullet. It would be fairly easy to make that work. Cut the foam up and use a temporary glue, like a light coat of water-soluble glue, to hold the slices together. Sandwich in the construction you want. Glass the thing, then run a LOT of water through to rinse out the residue.

Most of the weight of a board is in the skin, but it would be an interesting thing to try out.

[headmount]

Wouldn't the solvent that dissolved the cornstarch also dissolve the PVC?

Your new quad copter is very cool.  I'm green.

[PonoBill]

Cornstarch foam dissolves in water.

[headmount]

And I guess I'm proof that PVC doesn't.  Cool

For layups, has anyone ever used carbon/boron cloth? The boron is supposed to supply compressive strength that carbon doesn't.  As a deck patch or within a sandwich?

[Celeste]

The nature of the forces are going to be mostly handled in tensile.  Even in a sandwich the outer layer stretches as the load from a foot is placed on it, just that the inner surface/layer stretches more.  If I still had a FEA (Finite Element Analysis)package, I would work up a demo for you.