Where to begin

[CSX]

Hi, I am looking at building a storm hood to cover my sliding companionway hatch on my Tanzer 26.
I have used epoxy and glass to repair tabbing, parts and rebuild a mast step but I have never gone about fabricating a piece from scratch before.

It is basically a rectangle with around 3-4" deep lip and I was thinking I would core it wit a thin core-cell foam.
So I have been reading here and there about plugs,molds, and materials to make them and I am at a crossroad and thought I would ask for some help and opinions on what others would use to make such a part.

Any thoughts?

[marshmat]

Is it critical that this thing be as light as possible?

If you're not trying to get it to be ridiculously light, I think you'd be far ahead in time, cost and ease of construction if you just build it out of wood and epoxy. Building a mould takes at least as long as building the part you'll get from it.

[dskira]

Matt intersting design.
It is in development stage?
Daniel

[marshmat]

Daniel- yes, that thing ( Trailer cruiser revisited... as a trimaran ) is in development and I'll be starting to build some of her components later this summer.

CSX- sorry for the digression.

[CSX]

no problem.
nice vessel too.

I'm not real concerned about weight, but I don't mind taking the time to learn the mold etc. and the less weight the better

If I made a plug what type of wood would I use?

maybe a female mold out of Styrofoam would be easier?

Originally Posted by CSX

I'm not real concerned about weight, but I don't mind taking the time to learn the mold etc. and the less weight the better

If I made a plug what type of wood would I use?

maybe a female mold out of Styrofoam would be easier?

Any wood for a mould. Styrofoam is much trickier to handle than wood.

The easiest way I am aware of, is ply over temporary frames (I assume you have a "profile" in the hatch?), probably two sheets of thinner ply to make bending easy. It is hard to beat a sheet of ply in terms of weight to strength relation.
Properly sealed it may outlast the rest of the boat.

Regards
Richard

[tinhorn]

Originally Posted by apex1

The easiest way I am aware of, is ply over temporary frames

And if you build those frames with reverse curve, and substitute Abitibi or other "whiteboard" for the plywood, presto-zoomo--instant mold. You can build the lip around the edges right in the mold.

You'll likely want to radius the sharp corner at the lip. I used to use clay (and a #10 screw with flat washer attached, as a "radius scraper") to build the radius. I'd apply mold release wax to the clay with my fingertip, and I'd make sure there was a sufficient layer of gelcoat over the clay in order to sand and polish the less-than-ideal finish to perfection.

[CSX]

Is there a certain type of clay that needs to be used?
The white board sounds like a good idea.
Easy to bend

[tinhorn]

I used a clay that came from a fiberglass supplier. I'm not sure if a kid's clay is suitable, but I suspect that even peanut butter would work if it was thick enough not to flow. (I've built tons of molds from whiteboard. To avoid nail holes, use contact cement.)