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If I wanted to build hatches like this into my boat floor what is this perimeter drain channel called? Or is it just angle that you weld together yourself. It seems like you should be able to buy an extrusion that is used for the hatch seal and save a few fabrication steps.

Common name I've heard for that is hatch gutter, I believe they aren't typically extrusions but usually formed in-house from sheet on a press brake or brought in as a roll formed profile. You could buy standard alloy u-channel or square tube and rip it to the profile you want . . .

I will look to see if small channel is available. But the square tube is a great idea that I know I can buy. Thanks!

Tfitz, just some notes about channel extrusions.

There are two separate dimension categories or cross sections spec.s - one is ANSI or ASME (structural copies from steel primarily) with tapered legs in channels. The other are still rounded radius in some locations but the legs and throat/web/ are not tapered these are the Aluminum Association AA cross sections. Sometimes the vendors will call the tapered leg shapes "structural" patterns and the others architectural shapes- and this last is an indication the shapes are sharp cornered AND often 6063- which you don't' want unless you have to get stuck with it? So if your local supplier is confused between the AA shapes in 6061 and the ANSI 6063 square channels please be on the look-out for confusion on their part.

Last, the hull stiffener http://www.alascop.com/pdf/al/marine.pdf works great for hatch coamings because they allow the hatch covers' legs to be 110 deg instead of 90. This extrusion is 6061 not 6063, has a good shape for cover edges to fit into, and leaves good room to TIG in the drain pipe overboard.

I'm not saying your local supplier isn't aware of these differences, just that there can be confusion in this topic due to how little may be sold or handled?

Cheers,
Kevin Morin
Kenai

I've seen that hull stiffer at the local aluminum supplier before but I think it's too wide for my application. I will probably go the square tube route or bend my own on a metal brake at work. I haven't started working on Predator Control yet but I am beginning to think about it. It's still too nice outside for me to retreat into my shop for the winter. This global warming stuff has been wonderful so far

Tfitz, I ended up with a design project in the works- and this includes deck hatches. The shape of the gutter/coaming should be sketched in cross section IF there will be hinges? If no hinges these remarks are much less important. These hatches will be (at least) 60"x30" or so, and there are several.

If there are hinges; the hinge line becomes pretty critical- as the hatch leg nearest the hinge line will need to be designed/planned so the gutter and the pivoting leg on the hatch top (side bent or welded leg of the hatch cover) does not swing up into the side of the gutter?

I know (that) you know to plan this; but while drawing these preliminary designs and asking the owner questions about hardware this detail was discussed in detail. So it reminded me you'd planned some flush hatches with gutters/recessed coamings and wanted to post the reminder that the off side (away from hinges) leg is descending into the gutter nearly vertically. But the hinge side is rotating the hatch leg around the pin and that does make either the gutter or the bent sides' legs- important to consider.

All details "hinge" on where the pivot pin line is located- as to leg and gutter sizes. So just a reminder about the gutter design - it may be- you're going with lift off hatches that won't require hinges? so the gutter size could be much narrower ?

Cheers,
Kevin Morin
Kenai, AK