On Sun, Nov 3, 2013 at 5:48 AM, LucD <lucjdekeyser@telenet.be> wrote:
You have a better sense of the proportions but when I extrapolate from a screenshot found on the making of the Sol video there is little encroaching on the prime use portion of the bunk - a mere 15 degree rotation of the bed solves that. And the part lost under the seat is probably not prime storage volume.
All true, except that in little boats, all storage space is premium. The beam is 150mm in diameter, so this is a fairly large chunk of structure inside the small hull.
I also do not understand the requirement for beefing up the internal structure: fixating the original lower beam requires a hole and a lashing as you explained; with the higher beam there are just two holes in existing walls (and no hole in the hull ;-)
With the beam under the deck, the hole is in the hull, which gives it all the support it requires. The other end is under the leeward side of the bunk and the load is primarily upwards. This is taken by the wall. The much smaller loads (keeping the hull upright) are easily taken by a lashing onto the wall. With the beam above the deck, the hole in the leeward wall takes all the loads, but the outboard end sits on the bridgedeck and needs to be tied down to the side of the hull. This is the primary load and it is better if it is taken by the hull rather than the lashing.
Is there a difference in the stresses if the beam is above or below the bridge deck?
No, only in the way they are resisted. On top of the bridgedeck is certainly possible, but the small gain in windage is more than offset by the increase in complexity and loss of internal space.
rob
> ... Putting the beams on the bridgedeck would have
...
> required more internal beefing up and made an already small bunk smaller.
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