Dave,

I can't give you dimensions unless I know what loads are acting on your boom. Magnitude and direction. Contrary to what some people believe, I don't do guesswork.

>>Wouter, I actually like your design

Which one of the two ?

After some though I would personally do it even simpler in your case. Just two vertical planks and alu strips as top and bottom. And have the the outward facing corners of the timber plancks rounded at a woodshop. That should be sufficient to score "good" on the hurting your head aspect.

The sides of the boom can then still be given a non-constant contour optimizing for load baring and weight.


>>Aluminum strips on the 3 edges?

I really doubt wether you'll need that. Just alu on top and bottom (can also be carbon of course)


>>Thickness? The same width as the thickness of the timbers?

Probably not. Alu (carbon) is much stiffer then timber and also weights significantly more per volume. So you are looking at relative thin alu strips compared to the timber. And that is all you'll need anyway.


>>I'll consider an aluminum pole, What dia, and wall thickness?

Also for this I need to know the loads and such. However 80x2 round sections are pretty much commonly available and should hold. Such a section should only weight 3.40 kg (7.5 lbs) per 2.5 mtr (8 feet) length. This is probably bigger then needs be but it will give you a feeling of what we are talking about. If such a section is made out of carbon then it would still weight about 2.30 kg (= 5 lbs). So how much are you willing to spend on 2.5 lbs weight savings ?


How long is the foot of your mainsail ? And what kind of purchase are you using on your mainsheet ?



>>A 4" dia carbon tube has been suggested, anyone agree with that?

I find that a larger diameter. I think you can do with less. Note that 8 foot 80x2 mm alu tubes (about 3 inches outer diameter) are also as rearbeams on homebuild Blade F16's. There it handles sheet loads of about 300 kg at midbeam. Surely it will hold up as a boom.

But lets give you a proper design, so allow some time to get the laod data of your boat and run them through some calculations.


>>Wall thickness?

If going for a pure aluminium tube then you never need more then 2 mm walls. If you can get 1.6 mm then that would be perfect as that would be 25 % weight savings.


>>Most affordable source of such a pole?

Without a doubt your local alu supplier.


>>Any other thoughts or considerations on my original T proposal?

It can be done better.


Wouter