: In my mind by putting the uphaul torwards the middle of the of the stressed
: upper convex side of the spar using weak poly tube would be very easy to
: break. But it seem like you could have the strength of the stressed spar
: by fastening the rope first to the end then to a pulley towards the middle
: for easier handling. Just a thought.

: I was wondering about that and if it made any difference. The picture I
: posted of the guy with the A-frame mast did cut his sail with a big
: concave in the end. Probably for looks since it robs you of some sq
: footage.

: Most likely a crazy idea, especially if the spars could turn side ways, but
: if they didn't it would seem they would have the high strength as do
: bridges that have cables stressed in set concrete plus the strength of an
: arch with the outward pressure as in anchent building of door, window,
: church roofs and bridges.

: John

Hi John,
The internal rope idea would be easy enough to test, and if the rope is adjustable you could vary the tension to see the effects. Having the uphaul at about 2/3 would generate an upward bow to the boom, I see where bending/folding could happen.

I was thinking that a close fitting dowel in the poly tube might work better. That would be more like the cable reinforced concrete where the concrete acts in compression and the cable under tension but in reverse.

Another thing abut crabclaw rigs, sometimes there is a line running between the ends of the booms to adjust belly in the sail. It's set for the conditions, usually tied off to the boom itself.

One thing I did find with the test I did is that a broken wooden spar is easy to do field repairs on, just lash on some strips of wood/bamboo around the broken part. It'll get you back to dry land.

Mike Savage
South West Cork