Ajax

Un-tweaking a hatch

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My foredeck hatch is a cast, aluminum Bomar hatch from the mid-80's. It's solid and in good condition. The lens does not leak and the main gasket doesn't leak.

Here's my problem/question- It appears that at some point, someone accidentally dogged the hatch down with a line or other obstruction trapped between the sealing surfaces. Now the frame is just slightly tweaked so that the stbd front corner makes contact before the port front corner. As a result, the port dog does most of the work of sealing the hatch and the stbd side dog does very little, and the seal is not very tight.

Any idea how I can true up the frame?

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Put a line under the opposite side and do the same again....

Just joking

But if it is AL it should be carefully bendable into the right shape.

But better take it of the frame before doing it

 

P.

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Hmm...I might have difficulty getting it off the frame.

I did actually consider putting a wooden wedge under the other side and bending it back, but I wanted to consult the illuminati here, first. It's cast, not extruded aluminum so I'm not sure how much flex it has.

I'd be happy if I got it pretty close.

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This is a high risk operation with cast aluminum. Don't fuck with it until and unless it stops keeping the water out. Surely there are other items on the punchlist that are more important. #airplane

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I hear you. It keeps the water out but it's squishing the gasket unevenly, causing premature wear.  I may just have to live with it.

I like this old hatch because it has reinforcement bars across the lens, on the inside. Most replacement hatches I've found, do not have this feature.

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I've got a similar Bomar with the cast aluminum crossmembers. I haven't measured it but it's a big fucker, at least 24" x 24". Big enough to hit the underside of the boom when opened fully. Replacement cost is ~$1700. The smaller ones aren't much cheaper. I definitely wouldn't try a redneck repair in-place. 

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2 minutes ago, Leeroy Jenkins said:

Could you add a shim to the stbd dog where it contacts the hatch to even out the 'work'?  

Hmmm...quite possibly.  The dogs are aluminum, circular wedges. As you twist the dog, the wedge increases against the static dogging lump.

I could conceivably craft a thin shim of Starboard and glue it to the wedge. That would be the least harmful idea.

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2 hours ago, Ajax said:

Hmm...I might have difficulty getting it off the frame.

I did actually consider putting a wooden wedge under the other side and bending it back, but I wanted to consult the illuminati here, first. It's cast, not extruded aluminum so I'm not sure how much flex it has.

I'd be happy if I got it pretty close.

I had the same problem with a Lewmar hatch and just twisted it back by hand - open to 90 degrees and twist in the required direction.

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Twisting it back involves removing and rebedding. If it's not leaking (either at bedding or gasket) then maybe go for the minor tweak route.

Step 1. Add more rubber on loose/high side/corner

Step 2. Check out new 'fake true' fitting by closing as normal.

Step 3. If possible readjust tightness(of closed position) at the levers/knobs by slightly exaggerating the tightness on the high side. Lever style will be able to be backed off or tightened to a preset closing tightness by adjusting the screw that holds them

--any difference in 'trueness' of hatch between when boat is in water than when on the hard? No? Yes? Either way...

great...proceed straight to...

Step 4 Crack beer and scratch the currently non leaking hatch off the winter to do list

Step 5 Wait until such a time that you decide that maybe your windows/hatches are crazed enough that you want a fresh look. Buy a strip/sheet of acrylic. Budget 2k for pro help and rebed every single window and recut and renew every hatch with new plastic in the old frames...possibly the hatch boards and sliding hatch as well. Rebend and rebed your hatch at that point. You will now have what looks like new everything for the cost of one new hatch.

 

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1 hour ago, Ajax said:

Hmmm...quite possibly.  The dogs are aluminum, circular wedges. As you twist the dog, the wedge increases against the static dogging lump.

I could conceivably craft a thin shim of Starboard and glue it to the wedge. That would be the least harmful idea.

Starboard does not glue happily, if at all.

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4 minutes ago, Ishmael said:

Starboard does not glue happily, if at all.

I was afraid of that.

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IStream,is correct, cast metal parts have different grain and can be broken easily.  If you want to slightly shim the gap, go to an big auto parts supplier and get a small tube of penetrating silicone calking.  Make a small dam to keep it in place and fill the small gap.  The hatch will not be square but the gasket will fill the gap.  Practice on scrap pieces first.  This is tricky to do but it does work.  Good luck.

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I've got scrap PVC sheet and possible some G10 you are welcome to.

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Never mind.... wrong forum... Cary on.

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I had this same problem with a cast hatch (cast hatches are very different from extrusion types like lewmar) . I removed the lid at the hinges, took out the plastic lens. The lens if well bedded adds a lot of support to the frame. I took two plywood pieces and made a sandwich clamp, using some large width wedges to tweak the frame back square. You dont want to spot load the fame with a narrow wedge, cast is somewhat brittle. 

CAVIAT!! there is a chance you can crack the frame and now you have a VERY expensive fix, but this sandwich press has worked for me twice.

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