Expanded Polystyrene Foam

In the photo, no prep was done. We had some guys here say no prep was needed.

Typically, we would vacuum a sanded part as it is a heluva mess.

Even in good marine foams; hardware is best installed in decored areas recored with cabosil and epoxy or cab n milled glass n epoxy.

 

I would never go up in that bird. I'd love to see coupon testing.

 

Keith, that’s an interesting video. And, the narrator says, “it won’t take point loads”. When the XPS is crushed it releases gas from the cells which over time thru expansion and contraction contribute to delamination. It is interesting the loads that it takes. Seems like a delicate flower to touch.

The fiberglass technique for wetting out and cutting the tabbing was clean. Got to remember that one.

 

The older cloth covered surfaces couldnt take point loads either.....

 

I think that same reason is the cause of the delam in my picture. Some outgassing or some other reason the edge bonds failed related to the xps crushing a bit as the bag pressures are high on the edges. We vac and make a light air blast on all our parts going under vac.

 

I doubt very much the method in the vid would ever be used again since you can achieve better ratios and higher strength with vac.

The problem, of course, is distortion. The panels can't deform.

 

The method used by Mike Arnold is the system developed by Burt Rutan and what was called "moldless composite construction". There is a booklet that describes the process that can be bought pretty cheap at www.aircraftspruce.com
MOLDLESS COMPOSITE SANDWICH 4TH EDITION | Aircraft Spruce https://www.aircraftspruce.com/catalog/bvpages/moldless.php?clickkey=67710

 

Example of a plane made using this technique doing an aerobatic routine.