major help reqd with balsa problem

General Discussion
1

Hi Folks

I’m currently building a 10ft Balsa long board. I have enought 8ft sections of lumbar and 10ft * 5" * 1/4" mahogony stringers.

I had all my balsa wood planned and straightened at 2" thick

I marked the rocker profile on my centre piece of Balsa (and 8ft section and a 2.5ft section) and cut it out.

I then glued the 2 balsa pieces onto the one of the mahogoy stringers. This was done to make a complete rocker. At first I tried to clamp the balsa to the mahogogy but this didn’t work too well coz I had not cut the template out of the mahogony.

Anyway I quicky decided that this was not the best way so I removed the clampes and weighted the Balsa down onto the Mahogoy with all my other pieces of Balsa.

After about 20 mis I looked at the joint between the balsa and mahogoy and noticed that it did not look very flush. I removed all the weight and pulled the balsa off the mahogony (the glue was not set at this stage.) I then observed that the main 8 ft section of Balsa was bowed by about 1/2". This piece was perfectly straight before I cut the rocker profile out

1 - What cause the wood to bow. Did this happen when I cut the rocker profile out or did something during the gluing process cause it

2 - How can I avoid this happening again ?

Any advice would be seriously welcomed

Thanks

Brian

2

Changes in humidity will cause wood to bow. If you can take the bow out while your gluing it up by placing it bend side down and adding clamps at the ends. If you can do this then don’t worry about it, all the other planks will hold it in place.

If it’s bowed soo much that you can’t hold it down while its being glues up, then you should be able to straighten it out enough to allow this.

Just put a little weight in the opposite direction at the point were it starts bow and in a day or so you can get it straight.

Be gentle and add pressure/weight gradually, don’t force it any more than it wants to go or you could snap it, just work little by little.

The wood will want to spring back so take the bend slightly past straight to allow for this.