Best material for freestanding hull (suggestions?)

[ntrabbit]

I just had a couple quick questions about the best material to use in the construction of a hull. I am building a hovercraft this summer, and although I have not designed it yet, I have a good idea in my head. The hull will have a tub like construction, similar to a canoe but wider and flatter.

Bottom Line: After building a plug for the hull (nothing fancy, I don't care about a finished surface, so I don't think a gel coat will be needed) what layup material would be the best for this? It will need to be strong enough to stand in, and not crack or flex too much.

I was thinking that multiple layers of cheap mat might do the job, but I want to keep it as light as possible. On a previous hovercraft that I built, we used 6oz woven cloth over styrafoam. This worked well for that application, but not for what I want to do. Any suggestions would be great, Thanks a lot.

-Nick

[ntrabbit]

Hm... no replies, I guess my topic wasn't interesting enough. Lets try to make it more simple. Here are my requirements:

-light
-not overly expensive
-rough (no gel coat, no nice finish)
-can stand alone (not reinforcement)

What would you use?

[Tohbi]

if you were building over frames and cost wasn't a consideration, i would recommended c-flex. i have a boat built of the stuff and it gives good form over frames.

but for a plug, you will be glassing in your stringers later so cloth and epoxy may be the lightest, strongest approach.

[Not A Guest]

"best material" is hard to recommend.

You might want to replace the foam with light wood - cedar. You might want to increase the glass and resin.

With frames you can use thinner core and faces.

[ntrabbit]

Well, after doing some more research on the hull design, I think I have come up with a solution. I think that a free standing fiberglass tub for a hull would be a bit difficult. I think I will go with a common design that many people have used.

They build the frame out of a light wood, then cover the outside of the hull with 1/8" marine grade plywood. Then they lay 2 or 3 coats of fiberglass cloth over that. I think I would probably use 2 layers of cloth (maybe 6oz?) with a layer of matt between them. Some of the reading I have done says that a layer of matt between cloth helps fill in the small gaps created by the woven cloth, helping to increase bonding and prevent excess usage of epoxy.

-Nick

[danmarine]

90% of what I know about hovercraft comes from the books 'hovercrafting as a hobby' by james perozzo and 'light hovercraft design' by christopher fitzgerald and robert wilson. These books both contain some important factors and calculations which must not be ignored. Research sevtec design hovercraft. I would seriously consider buying a hovercraft in kit form, in the end paying design fees and kit cost comes with a proven track record and a support network.
Hope this is constructive,
Dan