I recently shaped a 9’3 triple stinger, and added a tail block. Didn’t get to glass it right away, so I had it on a rack, horizøntal and deck up. After I glassed the bottom, I noticed a bit of twist. And after I glassed the top, it seemed to get worse!
How could this have happened?
Sometimes this happens. Could be the wood, could be resin shrinkage, could be cloth
not straight, could be voodoo. Wave some dead chickens over it, or use weighting to
try and take it out while it’s still curing. Hurry!
Another reason I love Coil Construction. Vac-lamming on a rocker fixture makes twist
impossible.
are the racks …level?
sorry…
…ambrose…
maybe it was the chubby checker
and joey dee and the starlighters
tape playing in the shaping room
while you were asleep.
I would vote for conforming
to supports and atmosphere
although music
is a powerful force
not to be dismissed.
play some john philip souza
maybe it ill go back straight.
if that dont work put it in the sun
and bend it the other way,
like straight.
If I put the cloth on diagonally, will this cause twist when the resin shrinks? I wasn’t aware that the cloth had to be straight.
And by straight, I mean the warp fibers. I have always tried to keep the warp running nose-to-tail straight, but pull the corners in opposite directions to get the yarn (?) not to run straight rail-to-rail. I think this increases snap resisitance. But sometimes, I’ll just slightly turn the entire cloth to lay it down diagonally for the same purpose. But this can cause twist? Maybe so… particularly in the tail where it’s really thin… perhaps.
Thoughts?
I became acutely aware of glassing-induced twist when I was doing mold plugs
for Clark Foam. They had to be glassed heavily to withstand the pressure of the
concrete mold-making process, and they had 3/4’’ to 1’’ stringers to hold rocker
for same. All that fiber and all that wood meant we had to be very careful during
glassing and cure. Any mistakes would either doom the plug or be replicated
thousands of times if it went to production.
The cloth being a little off-axis by itself isn’t a problem, it’s what happens as the resin
shrinks with the off-axis fiber in it.
Can you elaborate?
…or maybe it was just me that was twisted…
…you re put a shaped longb in an horizontal rack…almost always twist if you have a not super perfect balanced rack (like Ambrose said)
except the MDI s that not twist in that condition
was that and the temperature in the room, high or very low
The board was kept in an unheated space, with warm days and cold nights, and changing humidity…sometimes very humid, sometimes very dry…all over the course of a week or two.
The rack is simply two wooden posts sticking out of the wall, a few feet apart, which the board just lays across.
Looks like that’s the issue…
Sorry for the delay, I’ve been shaping…
Ladder racks and temp/humidity changes are not a good combo. Usually you try to
do a 3-point support on a ladder rack, 2 support points on one arm, 1 on the other.
Center the one on the stringer, center the stringer between the other two. This way
you don’t have to worry about the two arms being level to each other.
You may never know exactly what caused your twist, and the board can still ride well
with a little in it. I’d still try to get it out while it’s curing. UN-level a 4-point rack opposite
to your twist. Put the board on there and weight the hell out of it, trying to twist it in
the opposite direction. (it’ll ‘‘spring back’’, I’ve never twisted one the other way doing this).
Let it sit for 3 or 4 days, check it periodically.
After I glassed the bottom, I noticed a bit of twist. And after I glassed the top, it seemed to get worse!
How could this have happened?
Im assuming polyester resin…which can shrink pretty badly, causing twist. Particularly if the cloth weave isnt perfectly aligned. RR epoxy shrinks far less.
Heat the board up, softening the resin and reset it,let it cool and see if that works. I know this works using epoxy but I dunno about polye.
yup !