Okay, and this is just the reason why a limit is introduced.
I've read and studied Bethwaites book from back to front and it is indeed a valuable sourse of good practical information.
"The further of the surface level the higher the windspeed" is very true although it's effect on sailpower is far more pronounced in realy light winds than in wind of abou 6 knots and higher.
Go to the following link and take a look at the (simplified) excel sheet I developped to run the numbers on this issue :
http://www.geocities.com/kustzeilen...ulent_improved_accuracy_f16_vs_jav16.xlsI've also run the numbers on modern and older A-cats and found that lengthening the mast while keeping the same sailarea did improve sailpower by some 8 % in the laminair conditions while retaining about 100 % (with respect to older rig) power under in turbulent winds and depowering.
The setup compared in the sheet are a Full compliant F16 with jib and the prospected Javelin 16 setup with just the mainsail.
By replacing the jib widths of the F16 by zero's you compare the uni rig F16 to the uninrig Jav 16
This model doesn't not take into account tip vortexes, but this effect can be assumed to be rather small as both sails have comparable sized squaretops although the aspect ratios are different. I don't expect this difference to account for more than a few % say 2-3 % in a sail power (Not speed).
A rough estimate of resulting gain of speed can be calculated by taking the square root (or 3rd order root) of the sailpower ratio. This decreases the gains made by excess sailpower alot. For example : 108 % power = 1,08 => root (1,08) = 1,039 increase in speed; Third order gives => 1,0259 increase in ratio speed. Real increase in speed will be somewhere between these limits.
What this sheet is showing, to an reader that know how to intepretate the data. Is that the Jav 16 as given will have equal sailpower to slightly more in laminair winds and equal sailpower to slighlty less in turbulent winds when both classes sail in uni-rig configuration. In general the % of advantage in laminair winds is mirrored by an equal disadvantage in turbulent winds. Ofcourse most races are held in turbulent winds.
With the F16 is fitted with a jib (as shown in the excel sheet) the situation becomes :
The Jav 16 in laminair winds can hope to have equality in sailpower. Yes that jib of the F16 doesn't do much but it still results in some 6 to 8 % increase in power which should be sufficient to compensate for the vortex and aspect advantages of a few % of the higher aspect jav 16 sail. Assuming that both mains have been equally optimized in sailshape design ofcourse.
In turbulent winds the jib easily accounts for 20 % more sailpower at relative low costs in righting moment ; 10 % and depowering of the F16 mainsail doesn't affect the jib untill very late so the F16 rig retains large portions of its sailpower to considerably higher windspeeds.
So my personal opinion is that that the Jav 16 will not have a unfair advantage over the F16's. Especially in doublehanded mode without a jib I rather see rather a disadvantage than an advantage.
But this is in relation to the Jav 16 design as present on the Bimare website.
The F16 rules ofcourse need to take into account the fact that a sloop design could be fitted with a taller rig. This fact will set such a tall rig design apart from the Javelin 16 and is resulting in a slightly different performance situation. It is this situation that is determining the mast limit in the proposed rules. Remember it is the jib that takes away much of the advantage a the taller rig has. And the Javelin 16 is made fairer in comparison because the designer choose to not fit it with a jib. Remember this when looking at the rules.
With respect to the Javelin 16, which even has less sailarea than allowed under the F16 rules, I see absolutely no reason to exclude it from racing on the fact that it has a 9 mtr. tall mast.
Wouter
