Boom Diameter

I was just wondering does anyone know why or has anyone tried using a smaller section boom than the current size. The regulations state that the boom must fit inside an 80 mm dia circle but why don't we use a much smaller diameter such as the "A" class ?

Naturally if the mainsheet is run from the centre of the trampoline there would be high bending stresses but if the mainsheet is attached close to the sail clew there would be minimum bending stress on the boom.

Looking forward to some feedback.

40 mm x 2 mm will work just fine without centresheeting.

Wouter

Hi Peter,
For a while the SA boats were fitted with 40x2mm as Wouter suggests, but I`d advise against it, most of the guys who had them bent or broke them, and have all (except maybe two) gone back to using a dinghy mast section which has a lot more stiffness.
Wouter, if you look at the Mozzie rig, you`ll see that the boom sticks out quite a bit behind the rear beam, so the sheeting angle is not vertical, you put quite a bit of load on the boom when sheeted in hard, under compression. Some of the skinny booms had permanent bends after a while becuase of this, and one or two broke but perhaps due to skippers landing on them in a capsize.
If you changed the rig to a squaretop and shortened the foot length to be just longer than the distance between beams, then it would work, but that`s a whole different discussion ...

Steve

Thanks for the feedback guys. Is there anything in between the 40 X 2 mm and the current section that would suit better ?

Check out the Sth African Boom diameters on the Mosquitos Dotan Rudder System image.

It looks like they have a smaller section but have spread the mainsheet loading to reduce any concentrated bending stress.

All,

I have been using the same size boom diameter now in boats for more years than I need to recall, so far without breakages, except when skipper or crew decided that it looked a sof landing...then they bend.

Boom diameter, 50mm x 1.6mm wall thickness....I am presently playing with a newer version of the same theme and so far all looks good...at least on paper, biggest gain will be in weight saving along with some gain in strength.

I have always used a single hanger for the mainsheet system, end sheeting system with no failures due to the loadings.

Food for thought