Scooby,

I would like to state first that I feel we are on the same track in most aspects relating handicap systems. My current discussion with you is mostly to get the details right as well. No disrespect intended.




I'm sorry to say but you were making more mistakes then that. And you are missing the way in which the F18 rules are indeed fixing the schrs/texel handicap numbers. In addition the Texel handicap number for F18 has come down over the years and you don't give that credit.





There are two arguments to be had here. First f18 class has become faster over time relative to old OD classes. While this is more limited then people often think; it is definately truthful. SCHRS didn't not change over time. Texel however had F18 transition from 104 in 2000 to 101 in 2006 while keeping the old OD classes at the same ratings. Same applies to other modern boats like F20. By the way 3 points rating difference is 1 min 48 second increase of performance per hour. Nearly two minutes. I think this to be rather accurate.

Now people will also understand why I prefer Texel over SCHRS. Texel is just alot more responsive to changing conditions in the catamaran racing scene and stays on top of things.

The other way, is that newer F18 are supposedly faster then the older F18 designs. This is a difficult argument as it is not as straight forward as it might seem. Grab and old dart hawk and slap an updated rig on it and you'll have a competitive F18 again. So yes while it is true that the hart hawk design of 1995 (with rig current for that day) WILL not be competitive in the more serious F18 racing this doesn't mean that an updated version with new sails etc won't be competitive again. Naturally it is very difficult for a rating system (either Yardstick or measurement based) to discriminate in this latter example. It will simply be undoable. Therefor both systems require the crews to keep their boats in excellent condition if the rating is to be fair. No rating will be fair to any beat up blown out boat.





I don't think this to be advantagious and really don't expect this to happen. Why because the measured specs of say the Inter-18 are really not much different at all from those of the Capricorn F18. The used rating formula can not discriminate between the two and I really don't believe that an inter-18 with a new and modern set of sails is that much slower in reality anyway. Alot of the F18 development is to be found in components can be put on any older design. If so desired the complete Capricorn rig can be put on a inter-18, same with the rudders and selftacking rig. Who is going to check that a boat that started life as an Inter-18 is still an inter-18 after several years of F18 racing (modifications) ? If its an F18 then it is an F18. The nacra inter-18 class OD simply does not exist. At least not in the way that I actively controls the modifications to the design.





You can state this another 100 times Scooby but that still doesn't make it true.

Now lets turn this thing around. You tell me what you preceive as the measurements of a rating beating F18 and I will first check whether it is F18 class rules compliant, then whether it is at all practical and then most likely show you that the SCHRS is within 1% of 1.01. 1% is the official uncertainty margin because of the numbers being rounded off.

Give it a shot Scooby and show us.





Okay lets look at this in detail :

For the full F18 class rules go here : http://www.f18.nl/index.html?Frame_Technical.html&Frame_ClassRulesF18.html

B.2.1.2. The maximum distance between the top of the forward crossbeam and the bottom of the upper measurement band of the mainsail shall be 9100 mm. See diagram B.2.1.2.


I wrote 9150 mm earlier but the correct number is 9100 mm. So the mast is limited in length unlike the A-cats.

This also severely limits the mainsail luff length as a low boom is a serious impediment to the crew, especially under spinnaker sailing. This means that on average the mainsail luff length of an F18 is 8.5 mtr. Designs with less will never be rated faster when using their correct amount so we'll ignore those boats for now. The maximum practical luff length on an F18 is 8.7 mtr. And that is absolute maximum as only 40 mm clearance under the boom is really too little. You can't get across on your hands and knees then you'll have to tiger crawl underneath it. Do that with a spi sheet in your hand.

So lets now see what kind of difference going from the average 8.5 mtr to 8.7 mtr makes.

8.5 mtr. SCHRS rating (unrounded) = 1.006191
8.7 mtr. SCHRS rating (unrounded) = 1.002552

a difference of 0.003639 = 13 second/hour racing. = 1/3% = way less then 1 %

This difference is negligible. it is also well in the order of the noise that is enclosed in the rating formula, meaning that we can't say whether this difference is the result of the longer luff or the error made when the rating formula was derived.

So you see while the F18 rules indeed don't actively rule upon the mainsail luff length (as the F16 class rules do), the other rules and what is practical in real life do very much limit all F18's to as good as the same luff length.

From an engineering point of view I can tell you that those 200 mm extra luff length so low on teh mast are really not efficient in any way. Their is far to much turbulance due to the hulls and trampoline that low and the windspeed itself is much lower there then compared to 2 mtr to 9 mtr up.




Agreed. This is why I prefer Texel. Getting things done with SCHRS is a serious pain in the neck. Texel is much easier to talk to and much more accomodating.





Yes and Texel corrected for this by having the ratings go from 104 to 101 over the last 6 years. SCHRS did nothing.




Most of these changes can be put on older F18 designs as well, making them alot more competitive again. Only exceptions are hulls and daggerboards. Rudders, sails, mast etc are all exchangable.




Class rating as a whole, YES. Individual F18 ratings, NO


Wouter