Correcting a Bowed Soundboard

[Darryl Young]

Thought I would try "cooking" my soundboard and see how that goes. Bought some second grade Lutz tops from Shane at High Mountain Tonewoods. This was a pretty good deal in that many of the boards are useable as first grade boards as the knot shadow is either in the soundhole area or in the waist so will be cut away. These tops are very silky so perfectly quartersawn.

I heated the tops in the oven at 200F for 1 hour. It brought some of the sap to the surface that discolored it a bit but it should sand away when thicknessed. I haven't done this before so didn't realize that I should have stacked these tops with stickers and put weight on the top while cooling to keep the tops from curling a bit. So mine are curled side to side a bit.

I've tried steaming/ironing them with an iron and they wouldn't stay straightened out long enough to sticker them. Any other suggestion? I have had this top (still in halves/no joined) stickered flat with weight on top for 6 weeks and it made no difference.

Can I cook the tops in the oven again and sticker flat? If so, should I use a bit higher temp? Any other suggestion? May have to chalk this one up to experience and use it for back strips.

[Tom West]

Darryl: Might be worthwhile wetting the concave side and if that straightens the top sticker it with the top wet and let it dry. Or if it straightens sticker it in the oven and heat again. Shame to waste it if it can be saved. I've not tried this so your on your own.
Tom

[Darryl Young]

I tried misting it with distilled water and it helped a little, temporarily. I wetted the inside of the curve and stickered it. It remains flat while stickered but the bow comes back when removed.

[tippie53]

NO WATER!!!
Often these will propeller bend but once braced will equal out. This is often a result of wood that is sawed on a twisted tree . Adding water may make the problem worse . If you can joint and glue them , the bracing will hold them in shape.

[Darryl Young]

John, does this apply even if the board is only bowed across the grain? It's not twisted or shaped like a potato chiped (meaning warped in two dimensions). It's not real bad but just beyond what I would call normal. Maybe I should post a pic so you guys have a better idea how much bow it has.

Do you think the steam may have hurt as much as it helped?

[tippie53]

especially across the grain. With humidity changes it is not uncommon to see the wood move. When RH goes up the center will rise as the grain expands and when it dries the end will rise as the grain cells shrink.
adding water isn't a good idea . Keep flipping the plates until they stabilize and place weight to keep them flat.
I store my wood weighted while it is unstable ( under 4yr old) Propeller warp is often a result of cutting a spiraled log.
Post a pic so we can see for sure what you got

[Darryl Young]

I'm getting pics now (waiting for them to upload).

For the record, this board was perfectly straight before I baked it in the oven. If I had to guess, I would say the 200F heat freed up the sap to move in the board and when it was taken out of the oven, it cooled quickly and the sap set while the board was in a slightly curved state.

As I mentioned, the board has been stickered inside the house for 2 months and hasn't changed any.......so I'm thinking I could leave it stickered for 2 years and it wouldn't help. Gonna take something more drastic than stickering flat I suspect.

[Darryl Young]

Ok, now you can see how much it is bowed across the grain.......tiny amount of twist from end to end. Doesn't seem the tiny amount of twist is an issue. If you look at the gap between boards, that gap is twice the bow of each board as the boards are oriented so they are bowing in opposite directions.

Warped Soundboard.JPG

[tippie53]

yup
normal put the curved side up and watch that flatten out.

[Darryl Young]

I'll try it......but after 2 months it hasn't flattened any (and I had the curved side up). I pretty well understand how wood moves with moisture changes. Is almost 2 months not long enough? Remember, it was perfectly flat before I "cooked" it.