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stringers/bearers


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Morning all,

I've recently taken on this 17ft Mayland as a project. when I ripped the flooring up I found the stringers to be rotten, which is fine I expected it. My question is should I have stringers running the length of the hull as I only have them running across the width and there's no evidence of any running the length in the past.

Also when it comes to glassing over the new timbers what would be the best rated GSM matting to use? I've fixed up a couple of boats in the past but not had to do this kind of "structural" work before.

b5.jpg

b6.jpg

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Across only should be OK, provided the floor sheet is stiff enough and the bearers are not over spaced.  Most narrowboat floors are 18mm WBP ply, often shuttering ply, on cross bearers at about 600mm centres.

The shallow v bottom gives you a splendid limber hole in the centre, so no need to worry about drainage.

The whole floor when screwed together will be pretty solid, so the bearers only need to be sufficiently well glassed in to hold them in the right place till the floor sheets are down.  There should not be anything structural about them.  It would be a good idea to cover the new ones in a layer of resin (ideally epoxy not polyester) and tissue, just to reducd the likelihood of future rot.

 

N

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Hi Mad Pirate

 

Mine was the same but a different boat. I lmainated the floor inpalce to give it all more strength.

 

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Tell you what have a look on Page 67 on here. saves me copying and pasting pics :) 

 

 

 

Captain Faffer :)

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Just a note on W&T's post above, the cross members are perfectly fine as they end on a strong point, i.e. that ridge in the hull skin and anyway the boat is not going to be crossing the Atlantic but as a general point beware of ending cross members or longitudinal stringers on a piece of flat hull skin, it tends to concentrate stresses which is not really what you want. Its not supercritical on the Grand Union but if you do get enthusiastic and build something that goes to sea and 'slams' into waves and troughs it could just start a crack. Good luck.

  • Greenie 1
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29 minutes ago, Bee said:

Just a note on W&T's post above, the cross members are perfectly fine as they end on a strong point, i.e. that ridge in the hull skin and anyway the boat is not going to be crossing the Atlantic but as a general point beware of ending cross members or longitudinal stringers on a piece of flat hull skin, it tends to concentrate stresses which is not really what you want. Its not supercritical on the Grand Union but if you do get enthusiastic and build something that goes to sea and 'slams' into waves and troughs it could just start a crack. Good luck.

On the OP's boat the cross members end at the chine, which should be fine.

  • Greenie 1
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11 hours ago, Bee said:

Just a note on W&T's post above, the cross members are perfectly fine as they end on a strong point, i.e. that ridge in the hull skin and anyway the boat is not going to be crossing the Atlantic but as a general point beware of ending cross members or longitudinal stringers on a piece of flat hull skin, it tends to concentrate stresses which is not really what you want. Its not supercritical on the Grand Union but if you do get enthusiastic and build something that goes to sea and 'slams' into waves and troughs it could just start a crack. Good luck.

 

10 hours ago, David Mack said:

On the OP's boat the cross members end at the chine, which should be fine.

 

 

Exactly why i ended them on the chine.

 

Bee means not to fix to a flat thin area as it will cause hard spots where the GRP will rub/sit on the timber unless it is supported away from the shell in the building process like a poly foam or sat away with wedges while its part laminated then remove the wedges once they are set to continue to laminate the bearers/bulkheads.

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