So I have been shaping single concaves in my boards.
Specifically I havent been comparing concave depths before
glassing and after glassing. Although, I am going to do this.
However, to those in the know.
How do concave depths hold up in the glassing step.
They lose a bit of depth??, or gain a bit of depth due to rail overlap??.
currently my concave max depth is about .16"
or 4 mm, or between 2/16"- 3/16" inch.
Usually they ‘‘hold up’’ pretty well, an accurate sander will re-create what was shaped. If anything, you might
gain a 1/16’’ (if you don’t take down the lap). This can be a problem when you shape a table-flat bottom and get
it back from the glasser suddenly slightly concave. When doing concaves, you can somewhat allow for this to
yield the final contours you desire. Conversely, if you want table-flat you might roll off the lap area and give the
sander a straight edge (and a six-pack, cuz he’s not gonna like this).
We’ve also found some “pooling” in the lowest centers of concaves, needing a bit of sanding just to get to the glass.
Then again, laps usually get sanded into pretty fully.
Laminating concaves, be sure to wet out till it almost starts to kick, to keep pooling to a minimum and taking less sanding at the next stage.
Found maybe the hotcoat and gloss coat changes your concave depth more than the lam coat, but geez, you gotta do that.
Final sanding takes it down to preferred depthl, if it’s that important to be precise.
Thanks Lee, I forgot about watching the ‘‘pooling’’. Usually that IS in the HC. Not a problem for the pro hotcoater with a UV box,
but something the homebuilder who might be reading this should take note of. Pooling in the HC (or gloss) is also more of a problem
in tighter and/or deeper concaves, defined channels being the most obvious example.
Well thanks for all the comments.
I measured my concave on 2 boards before I sent them to the glasser and then measured them again after they were glassed.
No difference and thats using a digital tire gauge(fowler x-tread) to measure depth. Both boards went to the glasser at max depth .14" concave and came back the same.
My glasser is good!
PureGlass, Costa Mesa