need advise stiffing boat

davlacey

ive replaced the stringers near enough to how it was originally built the hull is rock solid. today i put in a ash inner gunnell thinking it would stiffen up the side of the boat but nope it still flexs with a push. the side ribs are not fiberglassed to the hull ones only bonded in place for now. will the floor bearers add some strenght or what will here? is pics

Talent

Once you put the thwarts (or benches) in, the boat should stiffen up considerably. Don't know the length but if its more than 12 or 14 feet it should easily take two thwarts. In older style construction the thwarts often came complete with knees bracing the thwart fore and aft on each side against the stringer. Another method of stiffening is to install a foredeck, and, perhaps, an after deck but that might be a bit of overkill. I'd say you will notice a considerable difference with just the thwarts, provided they are built into the structure, rather than being merely propped on the stringers.

Talent

Just looked a photos again and noted no stringers below the gunwhale. Fitting thwarts to the gunwhale might be a bit topheavy. Any other plans?

davlacey

i wasnt planning on putting any seats in as its going to be for potting so i wanted as much deck space as possible. but it makes sense to have something running across the boat i had braces running across to keep the shape and it felt a lot more solid here is what im trying to achieve

fergal.b

Like Talent said putting in the forward locker or a foredeck and the back seat will make a big difference also when you look at gunnels on the other boat they are about 3" wide and 4" deep and there is inside bracing all this will make it a lot stiffer, if you are putting in bracing to carry the floor this will also help.
Your gunnel is not running the full length of the boat plus you need to have both of them fixed in place to form a bowed triangle before it will stiffen up, when adding the gunnels fix at the bow or stern first and pull them in with straps or clamps in equal amounts till they conform to the shape of the boat, they must be longer than the boat to start with as you won't get the uniform shape by adding a piece later, if you cant get timber long enough scarf two lengths together.


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Talent

Agree with Feargal. The scantlings on the other boat look stronger than on yours. It also has fore and aft bouyancy compartments which will add some stiffening. If you're hauling pots you'll need a fairly tough boat as they can add considerably to wear and tear. Also, are you planning to install a pot-hauler? That needs a strong secure mounting. Not wishing to preach safety but lobster boats have an unfortunate safety record and I suspect hauling from the side of a small, light, hull in a sloppy sea can contribute to overbalancing. I'd advise building in bouyancy, like the boat in your second set of photos. And I would seal them, and not allow them be used for storage. An open bouyancy compartment is worse than useless.

murphym7

I am not an expert, but I would imagine once you add the bracing to carry the deck and add the deck, that will firm the whole thing up.

fergal.b

Another idea would be to add gussets to your frames and make the gunwales a lot bigger this would make the sides very strong and would be a handy base to sit the pots on while you clean them out.

davlacey

yea the gunnell is about a foot to short what would be the best way to scarf another foot in. i added a piece in today to make up the lenght and it didnt sit right was like a sharp angled step between the 2 pieces no matter what i tried.it had a hauler but its more for messing with a few pots on a fine day. i might put a buoyancy tank running across the middle of the boat that doubles up as a seat

fergal.b

The best thing you can do is to put the joint in the straightest part of the boat.

https://www.youtube.com/watch?v=6xQ2X7NM5pY

davlacey

that looks like a lot of work to add a foot to a piece of wood. could i not just do two 45 degree angles and glue with resin its a fairly straight piece slight curve but nothing major

fergal.b

I suppose you could if you wanted but a 45 degree angle won't give much coverage in the joint and won't be as strong. Remember your building something that you will be putting your life and maybe the life of others in so every effort should be made to do the best job you possibly can to insure your safety even if it takes a bit more work, just my opinion





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