hatch experiments

[Marshall Moser]

Are you going to cut limber holes in the bottom of the channels for drainage?

[tech_support]

Instead of filets in your grooves, why not use a round nose bit? e.g. http://www.mlcswoodworking.com/ordersta ... _core.html

no fillets on the foam molds, the thickened epoxy fills it. But your right on the MDF molds, if my CNC machine had a tool changer I could have done that pretty easy.

Are you going to cut limber holes in the bottom of the channels for drainage?

some of them will have drains to the bilge or scuppers others will not. With the way I will fit the gasket material these hatches will be be very water tight.

[Marshall Moser]

So you are going to gasket at the top edge of the hatch so no water will pool in the groove? I was curious about that. When I get around to building one, I plan on using channels to divert the water to the sole for my elevated hatches (think exactly what you are doing, but with a channel that extends to the edge of the bulkhead, not just around the hatch. No seals required and no water pooling in the grooves.

[tech_support]

So you are going to gasket at the top edge of the hatch so no water will pool in the groove?

water will pool in the channel if its not drained

[tech_support]

first hatch glassed in, beveled out the hole so it sits about 3/16" proud. I want this so that less water gets in, its not high enough to be a trip hazard.






made a hatch lid, just a simple mold of MDF. The outside of the hatch mold is offset 1/4" around, enough room to fit the stainless piano hinge








This is the last lost mold I cut from the blue foam. Its much cleaner.

[chickenhawks]

The molds will be reuseable, wont they? I really like those hatches and the ability to custom make any size is great. What made the foam mold better? I would able to make a MDF mold with conventional tools but have never used any foam. As always you make this stuff look easy.

[Cracker Larry]

Very cool, Joel.

I doubt the foam molds will be reusable, that stuff isn't strong at all. It probably will not survive the removal process I think that's why it's called a lost mold

[Steven]

The molds will be reuseable, wont they? I really like those hatches and the ability to custom make any size is great. What made the foam mold better? I would able to make a MDF mold with conventional tools but have never used any foam. As always you make this stuff look easy.

With the foam mold, he didn't have to make fillets. The fillets in the MDF mold were used so the parts could be pulled loose from the mold. The MDF mold can be used repeatedly. With the foam molds, ease of release is not a concern. Just tear the mold loose and sand of the foam residue that's stuck to the part.

[tech_support]

thats right, the foam molds are tossed out after one use. After a coating of epoxy, they are coated with mold release prior to laying up the part. The foam is ripped out, and if the mold release is applied properly you are left with a mostly fair part. The part will require more faring, but its not much. There are no fillets in the mold, but you do have to lay some putty on the part so that the glass will conform.

The benefit to this over making MDF molds is that I can make many of these foam/lost molds at once and in any shape I want. Parts pulled off the MDF mold require a little faring too, they are not perfect. Basically, its a way to invest less time into tooling for a one off application.

So far, I pretty happy with the experiment

[Steven]

Are you using polyester or epoxy? What weight/type of fiberglass are you laminating with?