biggsy
New Member
How can I calculate the varying loads on a mainsheet?
Load on a mainsheet
- Thread starter biggsy
- Start date
Adonnante
Well-Known Member
Salty John
Well-Known Member
A very simple rule of thumb is:
(Mainsheet load in Kg) = (mainsail area in square meters x 25).
(The mainsail area for this exercise is the nominal area – the triangle formed by luff, foot and
leach. The luff length is known as the P measurement, the foot length is the E measurement.
(P x E)/2 is nominal sail area).
For example, the mainsail area on a Westerly Centaur is 12 sq. m. Multiply this by 25 and we
have a mainsheet load of 300 kgs.
(Mainsheet load in Kg) = (mainsail area in square meters x 25).
(The mainsail area for this exercise is the nominal area – the triangle formed by luff, foot and
leach. The luff length is known as the P measurement, the foot length is the E measurement.
(P x E)/2 is nominal sail area).
For example, the mainsail area on a Westerly Centaur is 12 sq. m. Multiply this by 25 and we
have a mainsheet load of 300 kgs.
Twister_Ken
Well-Known Member
Salty J
Interesting divergence. Your formula gives me a mainsheet load of 861 kg. The Harken calculator gives 580 kg. A substantial difference!
I'd have expected Harken to be the ones to big-up the result, so as to sell me more expensive blocks!
Interesting divergence. Your formula gives me a mainsheet load of 861 kg. The Harken calculator gives 580 kg. A substantial difference!
I'd have expected Harken to be the ones to big-up the result, so as to sell me more expensive blocks!
prv
Well-Known Member
Close enough, I reckon, given the inherent inaccuracies. It needs to withstand the shock-load of accidentally gybing all-standing in a stiff breeze, and I have no idea how to calculate that.
Pete
Salty John
Well-Known Member
The rule of thumb assumes sheeting about 1/3 in from the boom end and 25 knot winds. The biggest single influence on mainsheet load is probably attachment point on the boom so that can really move the load figure up and down.
Twister_Ken
Well-Known Member
OK - mine's right aft on the boom.
Blueboatman
Well-Known Member
Interesting question. You can at least double the steady load just to accommodate a snatch . Bung in a safety factor lets call it X4 for the Westerly 300kg gives 1.2t , which is still nowhere near the boats weight.. Boat knocked down, sail full of water, next wave thumps the exposed keel and 'forcibly' rights the boat dragging all that water filled sail up with it..who knows? Booms buckle and goosenecks break before the main sheet assembly gives way I would say ( unscientifically) ..
I worry about travellers releasing and slamming across, possibly near someone's handy hold...sensibly I see 'stops' on my traveller as well as tackles, for longer passages..
Sorry, waffling without giving a definitive answer!
I worry about travellers releasing and slamming across, possibly near someone's handy hold...sensibly I see 'stops' on my traveller as well as tackles, for longer passages..
Sorry, waffling without giving a definitive answer!
prv
Well-Known Member
Hmm, good point. I've just converted mine from pin-stops to tackles, but I left the stops on the track (pushed up to the ends). I could use these to lock the traveller in place if I was worried about it shifting. Though with a four-part tackle to pull through, I think there's enough friction in mine that it wouldn't run very fast.
Pete
Blueboatman
Well-Known Member
You're going racing aren't cha?
I alway liked the idea of incorporating some sort of shock absorber(s)...