I sent this once before but it got deleted so I will try again. I contacted the Boulter Plywoods Corp. at 24 Broadway, Somerville MA 02145. www.boulterplywood.com phone 617-666-1340, fax 617-666-8956
This is information on the difference between marine and aircraft grade plywood. Both use the same waterproof glue. The core layers are all the same as the outside layers. The big difference is in the thickness of the layers.The aircraft plys are thinner than the marine plys. They sent me a 6 page catalog. They have okoume B S 1088, the finest marine grade in thicknersses from 1/16,1/8,5/32 in 3 ply, 1/4 in 5 ply, 3/8,1/2,5/8 in 7 ply.Aircraft Birch plywood GL-2 rated. in 1/64,1/32/1/16 in 3 ply, 1/8, 5 ply, 1/4, 12 ply. They carry Sitka Spruce in Marine mast grade and in spar grade. They have them in lengths up to 24 feet.Spar grade is a very good quality spruce. but always get the lumber 1/2 inch wider than necessary, slice off a 1/8 inch slice and subject it to bending.A clean break is very suspect a splintery jagged break is OK. If you find a weak break mark the region of the break on the board then take a slice off the opposite side and subject it to bending. If a break occurs mark the main board. If the marks lie accross from each other you may safely assume that the flaw goes completely through the board at this place.Cut it out. Now you have got two boards but you know that each is good .There are many places that shorter boards can be used. Also a good scarf joint using epoxy glue will yeild a board as good as the original. Ladder grade of sitka spruce is also a source of spar material but after you have checked it for annular rings per inch, slope of the grain and knots and pitch pocket,as well as density, give it the bend test. I am sure that if you contact Boulter, they will send you a copy of their catalog price list. Regards Harold Woods. Orillia,ON. Canada. haroldwo...@rogers.com --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.545 / Virus Database: 339 - Release Date: 11/27/2003
