When calculating transverse frames what would be ...

[ldigas]

Originally Posted by Perm Stress

This cross tie is not fully effective for support for the frame as soon as loads are asymmetric (ex, wave slap from one side) , becouse cross tie itself is supported by identical frame the other side. So, span is B, but, if you are SURE cross-ties will be actually built as in the drawing, you may skimp a bit on frame scantlings.
if loads are symmetrical, like in submerged submarine, span would be A, provided that this cross tie is safe for buckling.
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To play safe, I would assume span B.

This is probably the course I'm going to take ... (since I'm doing a reconstruction of the boat, and this is the part which is "fixed") I will probably take B as unsupported, calculate the frames needed, and (since they won't satisfy the section modulus) just put down ... L50x30x5 and let the gentlemen at the classification society decide whether they will allow it.

The current side frames satisfy the requirements were "A" was the length, but not quite were I was to take "B". So it is an edge case.
But since the boat is build for restricted waters (20NM off the coast), and it will probably never sail in rough weather ...

[rxcomposite]

Originally Posted by ldigas

I was referring to GL Rules for yachts under 24m (I-3-3 part of the Rulebook).

Yes, it is in the fore part - approximatelly 1/3L from the forward perpendicular. I'm not sure about the term "discontinous floor". The floors on the bottom are bottom floors, upon which one diesel tank is fixed, and then above that are the beams, and a wooden deck sole on them, where the cabins are. So, it could be "a raised floor".

I was going to ask you that.

I will go for "B" as that satisfy the class rules. The ends are are bracketed where it connects to the floor and the deck.

Small yachts are sometimes built with different floor levels and are "discontinous". Purist would say anything in between the floor and the deck is a 'tween deck" (in between decks).

I also agree with Perm Stress, that is, you can skimp on the cross tie beam connection on "A" since the "B" (the longer span) has already been satisfied.