Maximum height of mainsail

25/10/2012 10:16:24
Can I check my sail plan rule understanding is correct... If using the more usual 5720mm luff main - the rule that the lower band must not be more than 730mm above sheer, the maximum hight for the lower edge of the top band (mainsail) is 6450mm (5720 + 730) above sheer-line? 
The absolute maximum the top band can ever be above sheer-line is 6910mm (6180 + 730), obviously this requires a mainsail with a 6180 luff)??? or have I got it all wrong???
Is there any advantage in going away from 5720 luff other than (say) on the river to get the rig higher? It seems this has become the de-facto standard, probably for good reason.

25/10/2012 12:37:15
Andrew M
All sounds entirely correct.  The formula relating luff length to sail area means that a higher rig and lower sail area will give slightly better windward performance but will be more difficult to hold up in a blow and a bit slower downwind.  The compromise has ended up where it is by a sort of natural selection mainly based on winning the champs on the sea.  As playing with rig dimensions means a new mast & sails experimentation is not cheap and the gains uncertain there has been little recent change, though as you say the river sailors go for tall rigs.

25/10/2012 13:06:06
RH .
JT has a taller rig I believe, not 22'6" but somewhere between 21' and max. There has been very little experimentation with taller rigs on new boats. 
Difficult to hold up in the past with metal masts and fixed shrouds but could be a winner with maderm masts and rig controls.....

25/10/2012 13:30:21
Many talk about this as if its one or the other - i.e. 21ft or 22ft 6" but it seems there is no reason not to go in between? I guess it makes sense to have the mast at least capable of the 6450 (21ft 2") max or perhaps a little more height and then put the top band in the most appropriate place in line with the rule.

25/10/2012 13:34:01
RH .
Lots of 80's NSM2's etc had a 21'8" set up


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