Stress Relieving The Hull

[Bill Jackson]

Hi guys,

I have started the old San Francisco S XVI. completed the hull assembly, in fact I still have a few pieces to go on the bow area.

I was thinking how, and if there is a way, to stress relieve the hull once its assembled. I and not a carpenter, I I have stress relieved metal after welding steel.

Anybody know about stress relieving wood?

Thanks in advance.

Bill

[amateur]

Nope: wood is not metal. There is more to gain from prebending your wood, in order to prevent stress. (Using moisture/heat/and sometimes a template to get the correct bend)

After assembling your hull will be (at least almost) symmetrical, so that remaining stress will more or less ‘even out’. 

As far as my knowledge goes: after carefully bending and fitting your planks, they should attach with relatively little stress. Therefore, once you glue them (both to the bulkheads and their neighbors) there is no need, and no method for stress relieving. In fact: any excessive heat/moisture after building your hull will damage your work.

Jan

Edited April 28, 2023 by amateur

[bruce d]

Hello Bill, as Jan has said, wood requires a different approach. If movement appears in the wood, you may be able to correct it without drama. Trying to alter the wood's properties may cause the problem you are trying to avoid.

 

In my Mediator build I was aghast to find the hull developed a bow after assembly. It was a central former with bulkheads, typical POB. Despite my first reaction, it was totally fixable. 

Photos below show what did the trick. I used some well seasoned wood to make spacers of the exact width between the bulkheads measured at the centreline (made one and cut it in half to ensure both sides were the same). No two gaps were the same so each spacer was made to suit for a snug fit. Once satisfied the spacer was the right width, I installed it on the tight side, ie the inside of the curve, tight up against the central former, giving a glued surfaces on three sides. Then I installed the matching spacer on the opposite side.  Clamps were used at each step. This deals with (A) straightening the curved central former and (B) ensuring each bulkhead was parallel with it's neighbours and at right angles to the former. I left a gap where the mast was to be located.

Nearly two years on and it is still straight.

 

All this is just my way of dealing with the problem once it appeared: most builds don't have this issue so ... wait and see if you actually have warping or movement and then react. 

HTH,

Bruce