Which timber for beams under cabin floor?

[Kelpie]

I need to replace one of the timber beams under the cabin sole. These beams have deep notches cut into them it carry cross beams, so whatever timber I use needs to resist splitting. I only need a small length so not too concerned on price, for once

 

[Rigger Mortice]

Elm could be good.

 

[KenMcCulloch]

Our 35 year old sole bearers are I understand Larch from the shores of Coniston Water. They have stood the tests of time.

 

[sarabande]

just make sure that the grain does not run diagonally across the load-bearing plane. Any close grained hardwood will be stronger than softwood, but we are not talking critical breaking strains here. Personally I'd go for ash or oak, but I have access to both.


Make sure that the cross beams are a tight fit into the 'notches' to prevent the bearer from flexing.

 

[itchenseadog]

It would depend on the type of boat, the span and size of the bearer. A good guide would be to pare off a shaving from the existing beam and replace with the same. A close grained soft wood suitably treated and protected would be ok.

 

[macnorton]

I have seen garden fence posts used, seems to work ok.

 

[john_morris_uk]

I've used Iroko in the past (but only because I had some to hand). Any decent straight grained hardwood should be fine?

 

[Rigger Mortice]

Any decent straight grained hardwood should be fine?

No. As a rule the straighter the grain the more likely the wood will split along the grain. That's why I suggested Elm which often has a very complicated grain. Traditionally Elm was used to make the hubs of cartwheels. Because it was so good at resisting splitting it could take the tenons of all the spokes. If you made a hub out of a straight grained wood it would soon split in half. The downside of Elm is that it can be a pain to work because of the cross grain.

 

[john_morris_uk]

No. As a rule the straighter the grain the more likely the wood will split along the grain. That's why I suggested Elm which often has a very complicated grain. Traditionally Elm was used to make the hubs of cartwheels. Because it was so good at resisting splitting it could take the tenons of all the spokes. If you made a hub out of a straight grained wood it would soon split in half. The downside of Elm is that it can be a pain to work because of the cross grain.

Perhaps I misuse the term 'straight grained'. Iroko is very complex in its grain structure so by your description should be fine as well?

 

[AndyJ76]

The guys who've just done a very good job of replacing the cabin sole in my boat used sapele. It's another complex grain one

 

[Rigger Mortice]

Perhaps I misuse the term 'straight grained'. Iroko is very complex in its grain structure so by your description should be fine as well?

TBH I don't know. I've never worked with Iroko.
Without piccies it's difficult to know what would be best. It does seem a little unusual to have wooden beams with deep notches beneath a cabin sole. But exactly what is meant by a "deep notch" is not clear either.

If in doubt the best thing may be to replace with whatever was there before

 

[Kelpie]

By 'deep notch' I mean that about half the depth is cut away to take a smaller piece of wood running lengthways.
I think I may have a suitable piece of mahogany somewhere so will try that. Thanks for the explanation re grain and splitting.