Thanks! That may give me enough to navigate McMaster's spring selection.

I actually have about 9" of room but I wanted the no load length 6" or less
to allow for extension and the adjustment mechanism.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Don Foreman" wrote
I'll assume that the 6" rest length and 3.5" max extension are due to
unmentioned constraints because that's too short for the geometry. The
spring will need a "dead" extension -- a link or piece of wire 2.29"
long.

The load moment at level is 67.55 lbf*in. With the 10" member
horizontal the diagonal spring is at a 16.7 deg angle from
horizontal. It will therefore need to exert 23.5 lbf to balance at
level. Extension at horizontal is 2.15", so spring constant k is
10.93 lbf/inch. To balance "slightly above" level the spring constant
will need to be "slightly greater".