Help! Expanding wood!

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richardh10

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A few weeks back, I had a new hatch made for the engine access in the cockpit , spent a bit of time fitting an edging to it making sure it is watertight. Just before Christmas put it in place, and stood back to admire. 3/4 inch iroko looked great. Fast forward a couple of weeks and all the rain has put a dirty great bow in the wood.

So the question is how to remedy this. I am fairly confident I can straighten the bend with some clamps while the wood is still wet, but how do I stop it happening again? The hatch is about 18ins wide, so should I split it into say3bits, and put some kind of caulking into the gaps? It obviously has to be watertight or I will get water dripping on the engine, which was why I changed it in the first place!

Any help gratefully received
 
Depends on the room you have but a 2 x 1 hardwood battern on the underside would do the trick ideally screwed through the top with the screw heads hidden with plugs. The battern can stop an inch or so short of the edges. I have a similar arrangement on my lazerette cover. Just an idea. Difficult to advise properly without a photo
 
richardh10 said:
A few weeks back, I had a new hatch made for the engine access in the cockpit , spent a bit of time fitting an edging to it making sure it is watertight. Just before Christmas put it in place, and stood back to admire. 3/4 inch iroko looked great. Fast forward a couple of weeks and all the rain has put a dirty great bow in the wood.

So the question is how to remedy this. I am fairly confident I can straighten the bend with some clamps while the wood is still wet, but how do I stop it happening again? The hatch is about 18ins wide, so should I split it into say3bits, and put some kind of caulking into the gaps? It obviously has to be watertight or I will get water dripping on the engine, which was why I changed it in the first place!

Any help gratefully received
Click to expand...

Iroko is notorious for movement. A photo would help as would a description of construction ie is it made of glued strips? If so, how wide ard the strips?
 
If you use solid wood it'll always swell and shrink according to its moisture content.You can't stop wood from moving so you have to build taking that into account.
I would use good quality plywood and seal it with epoxy and paint or varnish.Maybe even sheath it with a light roving.
 
30boat said:
You can't stop wood from moving so you have to build taking that into account.
Click to expand...
.. and if you pull it flat by brute force, e.g., screw battens to it on the underside, it ought to split when it dries out again, though given that it is small you might get away with it.

I'm guessing from the speed with which it has happened, that you have not sealed the wood with a finish - iroko being durable. If that's the case, the you may be simply asking too much that it stay flat when wet on one side and dry on the other.

If you take the brute force approach of the screwed on battens, rout slots rather than drill holes for the screws along the grain of the battens (across the grain of the hatch) so that the wood can move while still being held flat.

The dining table that I made moves about 5 mm in different conditions even though it's in the house. Worse still, the end at the radiator shrinks independently of the other end.
 
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