Click on my name and you'll see my personal info. You can do the same with Phill's name and see where he sails.
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<br>Anyways, I'm from the Netherlands.
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<br>OKay I've read my own post again and thought that I should explain the "not so much weather helm" better. As you said boards are all the same on the I-XX line. Now you rig will produce considerable less sailforce than the I-18 for which the original boards were designed / optimized.
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<br>Your maximum righting moment Ratio is about 60 % (assuming you are 75 kg's and boat width is 2,6 mtr. and boat weights 150 kg's; I-18 150 kg crew weight, 2.6 mtr wide and 180 kg's boat)
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<br>Your rated sailarea ratio = 12,31 / 14,80 = 83 %
<br>Mastheight ratio = 8,5 / 9 = 94 %
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<br>Heeling moment rig ratio = sailarea ratio * mastheight ratio = 78 %
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<br>So your rig is producing about 78 % of the heeling force as a I-18 would in the same windforce. Your maximum righting moment is only 60 % of that of the I-18. Your thrust ratio and heeling force ratio are then = 60 % / 78 % = 77 % of that of the I-18. This means that your daggerboards are about 1/77 % = 130 % is about 30 % to big for your loades. The daggerboards won't be working at their optimal angle of attack on your boat but at smaller angles. There is often a range of rather optimal angle but 30 % to big might be pushing it a bit. So when you go for alot of weather helm like many asymmetric sailor are eager to advice than the only thing you'll do in relatity is to take load from the already underlaoded daggerboard and load up you rudders. Thus the angle of attack of the daggerboards descreases even more and efficiency drops even more. You could end up (in the extreme case) with annoying weatherhelm and equal or less pointing ability due to a rapid decrease efficiency as a result of small angles of attack. You might want to lift your boards a bit before the other boats do for the same reason.
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<br>Anyways, with perfect neutral helm your daggerboards might be working rather acceptable but your rudders are simply added wetted surface only creating drag when not used for steering.
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<br>What is wise ?
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<br>Well, it can be argumented that alot of weatherhelm is bad. Perfect neutral helm can work quite well but is almost certainly not optimal for your rudder are doing nothing most of the time excepot adding drag. Best bet would be to lift your boards a bit and to induce a little weather helm This way you :
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<br>- Load up the daggerboards more per sq.ft. and go back to the optimal design angle of attack
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<br>- reduce daggerboard wetted surface that you don't really need
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<br>- Open up the possibility to induce weatherhelm without a negative backlash. This weatherhelm will load up your rudders so they will need to contribute to the sideforce resistance. Your rudders will still create drag but at least they now contribute positively. With neutral helm you will never use the rudders even when you lift the boards.
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<br>wel 30 % to big would make raising your boards by 30 % a good starting point.
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<br>Guys (Phill ?) , please correct me when I made an error
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<br>Wouter
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<br>(designing is all about striking the optimal balance between different features)
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