For a 2-up boat my models predict a upwind speed increase in the order of 1 to 1.5% ; over an upwind-downwind race course this translates into about 25 seconds per 45 min. race.
The 1-up setup the increase is about 0.3% less => 20 seconds.
That is what my models say.
Of course these increases ONLY apply when the crew is maxed out on righting moment, meaning fully trapping and is depowering the rig. There won't be much of a performance difference at all in all other sub maxed out conditions.
Wouter
Wouter,
I'd like to understand exactly what you are saying here.
Do you mean that once you have maxxed all the de-powering options (such and downhaul, traveller and mast rotation), you will have this 1% gain?
To put it another way; if you two boats that were exactly the same, and trimmed in the same way, with exactly the same crew weight, in exactly the same place (so DH in the same place, mast rotation etc) that the wider boat would exibit this 1% gain when both crew are fully trapped?
The SCHRS calc of RMOM (Righting moment) comes out thus:
2 up boat
2.5m = 460.75
2.34m = 440.19
460.75 / 440.19 = 1.047 just under 5%
1 up boat
2.5m = 293.5
2.34m = 279.18
293.5 / 279.18 = 1.051 just over 5%
SCHRS defines RMOM as
1/2 the beam x (weight of boat + crew weight) + number of trapezing crew x COG of average person (0.93cm) x average weight of person worldwide (75kg)
RMOM = 0.5 x BEAM x(boat weight+ combined crew weight) + Num-trpx 0.93x75
I dont feel that 5% extra RM will provide 1% more speed around the course, overall, in a spectrum of conditions.
I assume your 1% gain Wouter is in a single, ideal windspeed condition?
I'd really like to understand this (without too much science, it is Sunday and I am tired as if people really feel that the SCHRS model needs re-visiting on this, the management group will.
