I have a peice of wood ( forgot what type) previously planed to about 1/4" thickness. Approx. 8" wide. I cut one stringer out about a year ago and laid the remaining board on the ground against a wall inside my garage.
Now I am hoping cut one more stringer but the board has a pretty good “bow” in it across the width. (not the length)
Should I wet the board and clamp it flat? Any other tricks to getting it flat? Layed on the ground it is probably bowed up 3/8" to a 1/2" or so on each side.
I’m using construction grade 2# EPS with Gorilla white wood glue. I’m assuming I need to worry about this??? The stringer will only be about 2.75" at the max. so maybe no big deal?
I don’t know anything - sounds like its cupped, not warped or bowed to me. Best to post some pics. Also, have you tried a dry run, clamping it between foam to see if the clamping pressure flattens it out?
Cupping ?..backsawn timber is more prone to cupping that quarter sawn timber…try cutting your profile , oversized by 1/8" or 1/4" . If it’s good quarter sawn stock , it may flatten out a fair bit…if not , put it back where it was stored for year , reverse side up ( on level cleats) and it may flatten out…keep in mind that uneven texture on each side , such as one side planed smooth , and one side rough sawn (or bandsawn) , will atomatically produce cupping due to mismatched surface tension. All timber needs to be stored in a proper area , that keeps it flat and well ventilated on both sides.
Thumbs up from me for making your own blank. The 2# EPS sounds like a score, it’s mostly 1# around here. Here are some thing I have learned (the hard way) over a half-dozen blanks:
To the original question, use a nice(r) piece of wood for the stringer. Any of the defects in Huck’s picture will make it harder to impossible to make a straight glue-up. Any knots near or on the exposed edges of the stringer will make it harder to plane the stringer down to the foam.
Don’t cut the outline of the board before gluing in the stringer. It’s easier to clamp the pieces when they are blocks instead of curved. Some wood blocks between the clamps and foam can help too.
Don’t use a ‘Skilsaw’ type saw on the EPS. Stingray told me not to do this, I did not listen, pride comes before the fall. Eventually the saw will catch and kick and trash your foam.
Test your glue. I had a total disaster with EPS and Elmer’s white glue once trying to glue sheets into a rockered blank. It worked in small sample form but not over a surfboard-large area because it could not dry. For stringer to EPS I use Gorilla Glue (the foaming PU kind) and follow the directions for dampening the pieces with water to help with the curing/drying reaction.
Check the stringer ‘line’ before the glue sets. I have a couple boards where the stringer ‘took a walk’ on one of the ends. Not enough to notice right away but enough to make you shake your head later. If I had the space I’d build a big table for glue-ups with a trued backstop and push the pieces in from the outside.
Pic is of a 4’ double-ender blank I just made to practice routing finboxes. -J
