Re: Hatch camber

Posted by LeeG on May 3, 2004

Joe, are you using the same ratio as last time? Here's my two bits

1.Cut some 3" tape the width of the underside of the hatch where each rib will be glued. The important part is that the tape extends to the edge of the hatch and not just under the rib. The tape isn't really needed under the rib as much as it's needed in that little patch of plywood around the edge of the rib. Later on you can sand the tape part way down so that the hatch tape will compress evenly without a big edge.

2. put some unthickened epoxy on the end grain of the rib thats going to be glued to the hatch,,edge grain okoume soaks up epoxy like a sponge,,if you put a dry rib onto a marginal or dry fillet mix it'll pull the epoxy out of the joint. If you pull the clamps off too soon (read the hardener bottle for FULL CURE times)then it won't hold.

3. While the rib edge soaks up the epoxy, wet out the tape lightly and the spot on the hatch where it's going then lay the tape down, making sure it's going from edge to edge. You don't need it to be swimming in epoxy,,that's why you put just enough on both pieces.

4. Wipe any wet excess epoxy off the rib then lay a bead of thickened epoxy along the edge of the rib,,maybe 3/8" tall. With your clamps nearby put the rib straight on the tape using a spring or trigger type clamp to hold it in position. Of course this is the part where things can go springing across the table,,that's why the trigger clamps are so nice.

5. with clamps on both ends of the rib carefuly wipe the thickened goop around.

6. LEAVE THE CLAMPS ON ACCORDING TO THE DIRECTIONS ON THE HARDENER BOTTLE FOR CURE TIMES.

The reason for the tape is that when the hatches are strapped down the strap pulls down off the edge of the rib so the tape provides some rigidity to keep the top of the 4mm hatch above the end of the rib from cracking. The more important reason is that on the aft hatch during rescues your entire body weight is pushing down on the hatch,,that stress gets concentrated at the end of the rib,,without the tape distributing the stress or a sculpted fillet right at the end of the rib, as in a rib applied with just a little epoxy, the rib will pull away or the top veneer of the plywood will delaminate.

er,,unless it's 100 degrees I wouldn't remove clamps in 24hrs.

In Response to: Hatch camber by Joe Lombardo on May 3, 2004

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