Should I be aiming for any particular weight range?

The weight of 3 x 7’ lengths of timber is quite substantial although I realise that a lot of this will be planed away …

Just thought I would check!

I am aiming for my finished board to be 6’6" x 15 1/2" x 3/4". As I said made of pine - probably 3 lengths, glued side by side before planing to rough thickness and then shaping.

While I don’t know a helluva lot about alaias, I did have a look at the link you gave and links from that. Interesting stuff indeed.

I also noticed your drawing shows a volume of approximately 11.6 liters: excellent, that yields a weight of something like 5-7 kg, depending on the particular species of pine you use. http://www.simetric.co.uk/si_wood.htm could be useful in getting that number down some.

Also, you can calculate the specific gravity of your planks and then plug that figure into the volume. Your 7’x3"x1" plank is right at 252 cubic inches for full 3" x 1" section stuff. If that were water ( specific gravity of 1.0) it’d weigh in at right about 4.13 kg ( 9.1 lbs) Weigh your plank, divide that by the applicable one of those figures and you have specific gravity. Multiply that by the volume in liters from your drawing and you have a weight in kg.

Okay, if your 7’x3"x1" stuff is more a ‘nominal’ section size, say 3/4" x 2 1/2", just measure, multiply those numbers out and run them through the nifty online calculator at http://www.onlineconversion.com/waterweight.htm and there you are.

Hope that’s of use, looking forward to seeing how it turns out

I don’t think it will matter much, weight that is. I’ve always heard that a wooden board responds very differently once it’s in the water and floating. I think Paulownia is being used as much for it’s supposed resistance to taking on water as much as for weight and ease of shaping. If you have not purchased wood you could go with kiln dried clear cedar or redwood and it will be lighter and easier to shape. Like you, I did my first out of pine, then a followup with cedar. Both are tons of fun (built for prone riding), and I just glued up a redwood “blank” for number three.