Spinnakers and Gennaker girth rule

The landenburger spinnaker shape is getting flatter and flatter. How far are we off dropping the loose luff all together and just sailing with a hard luff? Reacher, screecher, hooter (or whatever you want to call it)

What is the purpose of the Gennaker girth rule?
The gennaker girth rule : at least 75 % of foot length (SF) at midheight (SMG)

Is it to prevent the sails from being used up wind?

Yes. Of course you can try to use a gennaker upwind, but I believe the rule it to prevent someone optimizing it for upwind; then you'd see some very odd "spinnakers" come out on light air races.

I dont think beachcat spis optimized for downwind VMG will become so flat that they will furl well. The Tornado is pretty fast compared to other beachcats, but the spi is still too full to furl. Perhaps a system like rollgen will work well, but it still leaves extra windage and added weight aloft.
There is a system called rollgen which might work, but it has other disadvantages like making inside gybing harder.
http://www.rollgen.com/index_e.htm


The 75% rule is probably there to stop attempts on developing "Code 0" type sails. Interestingly, not all catamaran class rules include the 75% girth rule

In the F16 class the girth rule is included in the rules because the Texel and ISAF handicap systems will otherwise consider them jibs instead of spinnakers and penalize the boats very heavily.

These system use this girth rule to differentiate between jibs and additional downwind sails like spinnakers.

Wouter

And that is a silly rule. It totally rules out a versatile sail like the Hooter. There is a way to cheat and meet the mid-girth rule, but why not just get rid of rules that were determined by monoslugs.
Rick

Until the hooter is just as fast downwind as todays spis, I think it is a good thing not having to buy another sail.

If the hooter is just as fast downwind as the spis, I agree that it is a silly rule.

I think my question has been answered. That leads me to another question.

If a firm luff arrangement without the girth is faster than a spinnaker, what are the benefits banning it? If it is not, what are the benefits banning it? It is not like we need more upwind sail area in winds over 7-10 knots. So whatever the shape is will be optimized for reaching and downwind. In addition, if this shape is able to be used upwind in light air, it will only make it more enjoyable and make catamarans faster verses other types of boats. I am not suggesting that we have extra sails onboard, just that there may be speed potential lost because of this rule.

Matt

How will we find out when we are bound by that rule in all our development classes?

As far as I can tell there is still an outstanding invitation for a hooter equipped F16 to race against true F16's and proof its worth.

This invitation is now over 3 years old and as of yet no sailor has yet taken us up on it.

I'm not longer an F16 class official but I can tell you that the Girth rule in this class will not be change UNLESS there is a clear advantage in doing so. That means the hooter sail must really have a significant positive impact on the boats behaviour and speed. Otherwise there is no point in offending Texel and ISAF.

For this reason the invitation was made so we could get proper data on which we can validate the choice for either sail. As of yet no good data is available. There is only anecdotal data.

Wouter

Well you could get over this by restricting the number of sails that can be used at a regatta.

In the 18HT class the hooter is outlawed too and there is only one set of sails allowed that can be used at a regatta. If your sail is damaged then you have talk with the RC to exchange it.

The advantage of the hooter is in light winds, when the hooter can be used upwind.

The big ventilos M2 catamarans use those gennakers upwind in light winds.

I don’t understand how inviting a sailor to spend $1200 to take one shot at a hooter shape is going to prove anything one way or another. Especially when it makes you uncompeditive in handicap races and basically useless to the sailor after the test.

I bet if we lifted the rule for F16 and F18, next year at this time we would know if a hooter is faster.

Andi,

I dont think that would work out well, limiting the number of sails. I would definately bring a hooter for distance events, especially if the forecast said light winds, and a spi for windward/leeward racing. I agree with Rick that the hooter is a more versatile sail, but the spi is faster when racing windward/leeward.

Matt,

as far as I have been able to find out, there are no mid girth limits in the Tornado class. There is only a max size of luff, leech, foot and mid girth, no minimum. I think the Tornado class is one of the most competitive classes around, and would have gone that route if there was a consistent advantage. The Tornado is also one of the fastest and widest beachcats around, and as such should benefit from a relatively flat sail building more apparent wind. But they dont go much flatter than the Gran Segel MK-IV spi, as the angles get too wide for a good VMG. For best VMG, the Tornados would use a spi with more draft then the Gran Segel MK-IV, but this is not done becouse they would be killed down the first reach by the boats with flatter kites going over on top of them. In smaller fleets, like the olympics, you can get away with a spi with more draft in it. But a sail so flat that you could use upwind would make the downwind angles too hot. The ORMA60 tris have sails like this, but they are a lot faster than the average beachcat and pull the virtual wind even further forward when going downwind.

If the spin is slower windward/leeward and max luff, leach, foot limitations do not force the hooter to be of smaller area than a spinnaker, this thread is over.

We had a (few) sailors campaigning for and with a hooter. Meaning they already had one. The Bim Javeling 16 being an example. None of them ever took us up on this invitation.

And we'll all understand that a class will not "just lift the rules" and get us in serious disagreement with both Texel and ISAF, hoping some sailor will show up with a hooter, and possibly find out that the Hooter is nothing special.

I'm sorry but that is just a foolish way of governing a class. Accepting assured damage for what is at best a promise is never wise.

So if anybody wants to see more hooters (pun !) in the F16 class then they just have to proof them first.

Anybody not willing to shell out some 1200 bucks for that is not serious at campaigning the hooter anyway. Remember I personally laid down 13.000 Euro's to have the first F16 in existance, that was BEFORE the concept of the F16 was at all proven. So don't expect sympathy from me if anybody is daunted by a mere 1200.

Wouter

Matt,

what I am saying is that so far it looks like the spi is faster on a windward/leeward course.
You have got to have _some_ rules for measuring sailarea, and there are limitations to the geometry of a hooter. I.e. you dont want the same amount of leech area (shoulder). But a hooter would measure in under the Tornado rules. So far, we have not seen any boats use a similar sail in competition. Reason is quite clear, the spi has a better downwind VMG, and the hooter can only be used upwind in light conditions. Most Tornado events dont have predominantly light winds.
The hooter also adds windage (I dont know if it adds more than a snuffer+halyard, but I think so). It also adds weight aloft, and I think the snuffer systems we have today are more robust.

For distance racing, or enjoying myself on a boat, I would be very happy with a hooter.

But then again people will revert to the "its the sailor" theory, not the boat, not the sails, not the talent, not the skill, motivation, athletics or the pizza he or she aint the night before.

LOL I kill me!

The F18 rule is the same.

- The China Sea has very light winds