How many board feet do I need

[tburris]

Im getting ready to start on my Allegra 24. My questons is how do I figure out how many board feet of Port Offord Cedar do I need to buy to strip plank the haul? The strips are going to be 1 inch by 3/4 inch, I was thinking about 700 or 800 board feet is that to much for a boat of this size? The Allegra is 24' long with a full keel and a 8' beam.

Thanks

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[Aramas]

Wow - you guys still use board feet?
I do it by looking at the output spreadsheet and working from areas and thicknesses. I suppose the manual version would be to use bits of string to measure the sections, then work up a rough expansion.
ie Run a bit af string around each section on the body plan, measure the string and write it down. Draw a straight line the length of the boat (to scale) then draw straight lines at each section using the measurements you got from the string. You could either use simpson's rule to get the area, or just do it on graph paper (making a fairish curve around the ends of the section lines) and count the squares.
That gives you the area, so it's easy enough to figure out from there.
The first rule of engineering - Ignore what you can't approximate, then approximate the hell out of everything else.

[Bob Smalser]

I'd have to see the plans to compute the actual surface area of the hull in square inches, but once I had that it would be easy considering a BF is 1" by 12" by 12".

If you are buying roughsawn cedar, you'll get it a full 1" thick for a real economy over planed 4/4 stock, which will run 3/4" to 13/16" and cost more....but it may cost a tad more time fairing.

Also take into account that all widths are generally nominal in the boards you are buying, and you have to include that in your calclations. For example, 1BF of roughsawn 1X12" generally is only 11 1/4 wide airdried. Plus up your calculations by 7 pct for 12" stock, 10pct for 8", 11pct for 6", and 13pct for 4" stock widths....

...and not every lumberyard computes it that way, so check, first. Some use true as opposed to nominal widths, depending on what you are buying.

Remember that sawkerfs consume a 16th, so you'll need another 5-10pct plus up to accommodate sawdust, depending upon stock width.

Strip is a very economical way to use BF, I'd only add 5-10pct overage to my calculations for slack depending on lengths of stock available and the quality (knots) in that stock.

But why Port Orford? Nice material, but ain't it a lot more spendy than Western Red, which is perfectly adequate?

[ 08-03-2003, 03:13 AM: Message edited by: Bob Smalser ]

[Paul Scheuer]

Your 700 - 800 BF sounds a little high. But there's always the next project. (That's part of the disease).

For a rough estimate, if your shape is approximated by a half-cylinder 24 feet long, with a 8 foot diameter, your area is about 300 square feet. At one inch thick that's 300 BF.

As noted above, you should allow for kerfs, and more if you are going to avoid knots.

[tburris]

The reason why Port Offord was that I wanted to lighten up the interior. I also like the properties of P.C. I found a lumber yard that has some nice 1x4's clear VG he wants $3.50 a board foot. I havent looked into Western Red not sure what its running a board foot or the availability of it here in Oregon. I thought maybe I was a little high on the amount that I thought I would need. I will probably stay around 400 to 450 bf thats a good place to start :D

[Bob Smalser]

I'd look around some. In that quantity, you can get roughsawn WR for a better price than that. Look for small and portable sawmillers locally.

If you were to buy 500BF this week of fresh green, WRC in the 2-dollar range and immediately rip and stack your strips, you've almost three months of drying season left. WRC is one of the more user-friendly woods to dry.

If you picked an open, sunny, sloped site, stickered each board deck and covered the top with tarpaper so as to leave open sides, you could get those strips pretty close to the ideal 18pct M/C by the end of the drying season on 1 Nov. Old free pallets make good bases.

[ 08-03-2003, 05:34 PM: Message edited by: Bob Smalser ]

[Art Read]

One caution with Western Red if you're not used to it... Some people have VERY strong alergic reactions to it's sawdust. It 'bout knocked me on my ass after just a few hours of cutting and sanding it to build my floorboards. Awful flu-like symptoms combined with asthma bad enough that I was very close to going to the emergency room. I've never had, before or since, ANY particular problem with wood dust, but that stuff is nasty. Lot of sawdust gets made strip planking a boat...

[Nicholas Carey]

My back-of-the-calculator computation suggests maybe 300 board feet of 'finished' strips, maybe a bit more -- about 200 strips 1" x 3/4" x 24 feet or thereabouts.

Factor in the extra percentages as detailed above.

If you're ripping strips with a regular table saw, a regular blade takes a 1/8" kerf. A thin-kerf blade has a 3/32" kerf. With an 1/8" kerf, you're looking at 12-1/2 percent waste in the form of sawdust ripping 1 inch strips out of 8-inch boards. With a thin-kerf blade, you're looking at about 9-1/2 percent waste in sawdust.

[paladin]

...and ...a little more waste if'n you izz gonna make bead and cove or tongue and groove planks....