urban-wombat
27th June 2006, 04:02 PM
Cutting cedar planks for musical instrument sound boards.. sometimes I have the problem that when cut I end up with a concave profile..the plank size I'm using is 30 cms wide X 25mm thick.. this is cut into two sets each 30cms X 10mm.. if the planks are not concave.. all I do is plane the two inside surfaces flat .. then remove the unwanted timber from the other side so I end up with two planks 30cms X 3mm.. .. but if they end up concave I'm finding I don't have enough thickness to get the inside 100% flat after removing the concane profile..so... what's the trick for cutting thin planks without the unwanted profile? Col
echnidna
27th June 2006, 04:14 PM
If the timber is cupping after you split it down to 300 x 10mm, theres probably internal tensions in the timber.
try ripping it into 3 boards 100 x 10mm.
Then joint edges properly - glue up into 300 x 10.
Alternating the growth rings is a good idea,
but keep all the grain running the same direction.
AlexS
27th June 2006, 05:42 PM
For boards that wide & thin, you need to use quarter sawn stock, otherwise it's inevitable that the boards will cup at some stage. The timber needs to be well dried.
urban-wombat
27th June 2006, 08:02 PM
Bob and Alex thanks for the advice.. I do buy the timber as 1/4 sawn.. I guess the best plan would be buy extra stock and cull those that ain't any good..the only other way I could go is don't book match ..
echnidna
27th June 2006, 08:25 PM
Another idea might be to buy the boards already thickness sanded to 3mm and just join them for width.
have a look at
www.thinboards.com
IanW
27th June 2006, 08:54 PM
U-B - yeah, I like bookmatching (for door panels, not musical instruments) so I'm usually cutting pieces more like 35mm or more thick. And cupping can be even more of a problem with thicker pieces. This is because of tensions created by uneven moisture distribution, as someone has already said. I find the best bet is to put the sawn pieces on stickers, on a flat surface, and weigh them down, and wait and see if they settle (which they most often do) before final planing.
The main problem with trying to flatten or clean up too much after sawing is that you will quickly lose the bookmatch, which kind of defeats the whole exercise!
Cheers,
urban-wombat
28th June 2006, 03:20 PM
Bob and Ian ..many thanks for you help..I may not book-match
jow104
28th June 2006, 06:49 PM
How did they do this 200 years ago?
Did they hand saw or just split?