Re: installing flush hatc

Posted by LeeG on Oct 30, 2006

Derik, more than one way to skin a cat. My preference is for a 4mm hatch with ribs and glassing as needed for holding shape/strength because doubled hatches require doubled spacers and recreating a hatch mold takes up time that could be spent making the hatch and recesses.

On three CLC kayaks Northbay, Ch18 ( aft deck curve like LT version) and my own design with fairly flat aft decks and one Mill Creek with a bent aft deck I used 4mm flush hatches. The foredecks of the Northbay and Ch18 had regular 16" radius curves.

On the aft decks I made as large a possible round hatch with the opening about 1"-2" from the sheerclamp. The millcreek had an oval aft hatch the same size as a VCP hatch. The Northbay and Ch18 had round fore/aft hatches.

With the front hatch the problem using ribs is the same as the regular Chesapeake hatches, beyond the rib the plywood hatch wants to flare out a bit so it won't follow the deck curve as well but you can split the difference with a slightly tighter rib and putting some glass tape under the rib out to the end of the hatch and sand it halfway through before putting gasket material on.

The aft hatch can be plenty strong with glass and rib(s) as needed. One round aft hatch hatch was absolutely flat with doubled 4oz glass on the bottom and 4oz on top, with a little 3/16"x1/4" rounded rib underneath set crosswise glassed over with 4oz.

The big (14") round hatch hatch had one big transverse rib and two layers of 4oz underneath with 6oz on top.

The oval hatch had three ribs and no underdeck glass with 4oz deck glass.

On the two front hatches one had a transverse rib and one had three like the regular hatches. In retrospect oval front hatches with three little ribs would be better because one rounded hatch puts a lot of bend into the widest rib and tends to make the glassed hatch whiten on top where the rib ends and the hatch tries to flatten out against the glass compressing it a bit. It's not visible if you use straps or configure hatch dogs there.

After cutting out the cured glassed hatch (with fill coats) you need to get the hatch back into it's curve or it'll flatten out and make slight white crinkly images in the glass.

If the aft deck is an LT version you don't have to worry about springback on glassed cutout, sand and glass the underside of the hatch with 6oz or two layers of 4oz and put a rib across that reaches to within 1/8" of the recess.

The recess/spacer plywood doesn't have to be wider than 1" where it glues on to the underside of the deck. I made the spacer about 7/8" with one edge sanded down at an angle, then when it was glued on a finger ran the goop around the edge it makes a smooth transition to the underside of the deck. Make sure to sand the underside of the deck where the spacer goes on.

Therafter the recess goes on after trimming the spacer flush to the cut out hole. Like the spacer the recess can be two or four sections. It's hard to get two sections to fit perfectly but if you can go for it. I make sure to have the grain on the spacer and recess at 90degrees to each other.

The recess ply is twice as wide as the spacer. about 1 3/4" wide, 7/8" for the recess (minus 1/16"-1/8" for booboos) leaving 3/4" for the gasket.

When you sand the underneath edge of the recess to follow the sloped spacer you get a smooth sloping edge going down to the underside of the deck which you'll appreciate when reaching around underneath the deck or dragging bags up out of the hole.

In Response to: installing flush hatches by Derik S on Oct 30, 2006


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