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dealing with bends in a true 2x4 strongback
I just built a strongback from rabbetted MDF to 2" x 4". It has couple of little curves to it.
Nick's book is based on a "2x4" strongback and forms that have 2" x 4" holes, so you can true the forms on the strongback by taking advantage of the small difference, and shimming or using cleats. By building a true 2" x 4", I seem to have lost that option. I have no way to move the molds to accomadate the curves.
Did I just screw up the strongback bigtime? If I do it again, might I get it right? Should I try planing the MDF strongback to true (but no longer 2")? Should I toss this MDF strongback and go back to 2x4's, ala Schade?
-Robert
2 replies:
RE: dealing with bends in a true 2x4 strongback
The quality of the materials may be part of the issue. My current project, a dory, required a beefier strongback so I built the box from 3/4" furniture grade plywood. It's very straight but would be too robust for a dainty kayak. I saw a kayak strongback made of 1/2" ply at a local building expo. The builder told me he'd made several 'yaks off the same form with no problems. His was made of Baltic birch ply.
RE: dealing with bends in a true 2x4 strongback
» Submitted by jmichael - Thu, 9/17/09 » 6:30 PM
I had (have) the same problem only I made my 2x4 strongback our of 1/2 inch plywood. I ended up wetting the plywood and leaving it out in the sun on a flat surface. It straighten it out except on the every ends. The strongback was 12 ft long I just didn't think I would ever find a 2x4 (lumber) any better.
I sanded the strongback with my belt sander, rounded the edges to create space for the forms. I had to adjust the end forms, but the other forms lined up very well with just slims.
I read somewhere to use 3/4 inch ply the next time.
Mike