Formula 16 HP class FAQ webpage

This is a result of the assumption that the used measurement system is accurate in reflecting the performance influence of several parameters of which the aspect ratio of the sails is one. It should be underlined that there are strong similarities between the ISAF small cat and Texel handicap systems and that the relative performance predictions are similar to the performance indications as given by Yardstick systems. The measurements systems are based to a large extend on scientic relations and experiments described and conducted by maritime engineers such as Froude and Marchaj. The Texel system for instant does not take sailarea as a parameter in its prediction formula but a parameter called �rated sailarea� which is a function of the sailarea and the luff length of the sail. This is done to incorporate sail effectiveness into the prediction. We all know that high aspect sails are more effecient than low aspect sails.

It is now found that, for example, both the Taipan 4.9 and the BIM 16 have the same �Rated Sailarea� for their mainsails. This is the result of the fact that a longer luff of the BIM 16 mainsail (higher mast) is just enough to compensate for the less sailarea when compared to the Taipan.

When the grandfathered boats are run through the Texel prediction formula, it is found that the named boats are very near in predictive performance. The end goal is ofcourse to make them perfectly equal. But also equal within a margin of 1 % is very acceptable for a grandfathered boat. Mind you this 1% is only an uncertainty margin and not a offset of 1 % in the predictive handicap number.

The answer to the comment is therefor. The differences in particular design features are corrected out by other differences in design features. The sum of all the performance related differences between the designs is therefor equal, thus the performance prediction is equal. This will ofcourse be tested in experiments.

There are several reasons for this. The size of genakers has been heavily discussed but has now been fixed.

First reason is that the F16HP class is an (around) 16 ft class where the grandfathered boats are a little over 16 ft. (Taipan 4.9 and BIM 16) and spot on 16 ft. (Isotope and Cirrus Energy). Texel (as the other measurement systems) prescribes that 16 ft and less boats are only allowed to sail a genaker of max. 17 sq. mtr. A 0.5 sq.mtr. difference is accpetable, a 3,5 sq.mtr. difference isn't

Second reason is that it is found by Julian Bretwaite (designer of the 49-er and several 18 ft. skiffs) that higher genaker area�s are not always better or indeed faster. He found as is described on the int. 49-er webpage that luff length of the genaker is more important and the higher aspect genakers are generally faster when the craft is capable of high speeds. This would favour the 17,5 sq. mtr. genaker over the 21 sq. mtr. This is confirmed by a reknowned sailmaker in NL for he often make genakers smaller than is allowed under Texel for a given genakerpole / shroud / mastheight combination. I personally have a genaker on a 18 ft. boat that is 2 sq. mtr. smaller than allowed for he indicated that he couldn�t put more sailarea in the given trangle (this determined the luff length) without sacrificing the optimal shape.

Third reason is that the F16 HP is intended to be a flexible class that can be sailed with a crew as well as solo using the same parts. A lower aspect 21 sq. mtr. genaker is probably too big to handle and too heavy on the sheet (Julian Bretwaite) for a solo sailor. Other existing solo designs use 12sq. mtr. and 15 sq. mtr genakers. The 17,5 sq. mtr. genaker is already a concession to the 2-up configuration.

Fourth reason is that we aim to sheet the genaker off the sidestay to provide clean gunwales and a clean trampoline. Sheeting a genaker of the rear beam, probably needed on a �just over 16 ft� platform with a 21 sq. mtr genaker, will hamper manouvres and especially when solo sailing.

The fith reason is that it shouldn�t be forgotten that the F16HP boats are alot lighter than the normal catamarans of 16 and 18 ft. length. It can therefor be argumented that they need less genaker area to achive optimal downwind performance. The 21 sq. mtr. genaker area was fixed under Texel for boat of 18 ft. and a little shorter as well as boats that weigh about 20% more than the F16HP boats when looking at overall weight (craft+crew). Having the same downwind performance as an F18 (a design goal for the F16HP) requires a genaker that is 17 % smaller (Direct results of the fact that the F16 HP experiences only 83 % of the drag of a F18) . 17 % less of 21 sq. mtr. (the biggest F18 genaker size) is about 17,43 sq. mtr. We've decided to round it off to 17,5 sq.mtr.

The main reason for this is to limit the uncontrolled splitting of the catamarans scene into smaller incompatible fleets and end up with the same old handicap system blues again. The second reason is that equating the performance will make racing more fun for the F16HP guys because than they can race on a one-design like basis with the very popular F18 class. Meaning more boats on the startline, more fun and a better basis for learning and honing skills.

Equating the performance was also stimulated by the fact that the two base designs around which the framework is designed allready come very close to F18 performance, so why not go the extra mile. And it is a great way to start a class ofcourse.

Furthermore, it must be realized that to get a 16 ft. boat up to speed with respect to a modern optimized 18 ft. design is an big achievement in its own right. This is in no way holding back the true performance of 16 ft. boats. It is actually raising the bar considerably and this will put the 16 ft. design at their very optimum with respect to performance. At these speeds it will not be easy to find considerable gains in performance if not impossible. Maybe the F16HP can be made another 2 or 3 % but is this compelling enough to abandon the fun derived from the �one design like racing� and �less fleets more boats� concepts that equality to F18 provides ? If someone answers with "yes" to this question, and I think we could be persuaded too, than we propose to keep with the concept of performance classes and design a catamaran that is equal in performance to the iF20 class. But for now the bar on F18 performance is high enough.

The set of parameters reflecting the performance potential of a design are put into a prediction formula. This formula will be taking from the system which we have found to be the most accurate in predicting performance. The result of this formula is required to be the same as as the F18 performance prediction. One parameter in the set of parameters is �rated jib area� (calculated from the jib area and its luff length). Now when the set of parameters is not giving the same handicap numbers for the F16HP as for the F18 class than the �Rated jib area� is changed to make the two predictions equal again. This way the jib parameter is the fine tune button.

This will ofcourse only work well when the other parameters have put the design near enough to the F18 performance number and when both F16HP and F18 are comparable in their general make-up. Achieving the last is the task of the F16HP framework.

One of the parameters used in the formula is crewweight. The differences in crew weight will therefor also be equalized by max allowable jib size.

On the question wether this is impractical or not. No it is not impractical; the framework as a whole will make sure that the set of parameters is such that the preformance is already very comparable to the F18, withing a very small margin say 1 %. It is also expected that a crew will let a jib be made for their crewweight and design which is not expected to change much over time. When a crew is changing make-up alot than the owner can choose to buy two or three tactically sized jibs and sail with those. True racers buy new sails often anyway and recreational sailors loose alot more time on bad manouvres and sub optimal trimming to notice the performance difference of 0,5 % due a less optimal jib size. 0,5 % is only 18 seconds in one hour of racings.

Mind you the whole set of parameters for the 1-up configuration (same parameters as the 2-up set without jib parameter), is used to equal out performance of all the one-up configuration. This will also make the 1-up configuration equal to the 2-up configuration allowing them to race on an equal basis. This feature was more or less discovered by luck. It was found that the parameters set of the Taipan and BIM were such that 1-up and 2-up with jib performance was very close to one another. It was found that the measurement system�s predicted positive impact of having a jib was nearly equal to the negative impact of having the extra weight of a crew. Experiments will be held to test this remarkable feature.

Races from the perspective of the crew can be devided into two main considerations. The first is �they want to have a fair race� the second is �the want to have an enjoyable race�. These two considerations are often aclaimed by one-design classes, and with good reason we might add. However many of us are racing more in handicap races than in true One-design classes. In this paragraph the improvement of these two points will be explored with respect to handicap racing and finally with respect to the F16 HP class.

Main considerations which are related to :

Fair Race :

-1- Same conditions for every crew during the race
-2- Consistent relative performance potential under the same conditions
-3- Same chance on particular advantages like for example clean air and wavesurfing
-4- High and consistant accuracy of the handicap rating methode used.

Enjoyable race :

-1- Sailing with the pack while being in direct competition with the others
-2- Easily determinable ranking while still racing.
-3- Similarity with other boattypes.
-4- Handling and skill more important than design inherent performance.
-5- The ability to race in a fair race when handicapping is used.

The problem with many different handicap systems is that they are required to effectively rate an high number of very different boat designs. This will inherently be reflected in the accuracy that these systems can achive. This nearly impossible task is to a large extend the eternal downfall of a handicap system. A few examples;

* When there is a big difference in actual boat performance the impact of changing weather conditions can be significant. We all know that slow boats win when the wind is increasing in strength and the other way around when the wind strength is continiously descreasing.

* When there is a big difference in actual boat performance than the slower boats get always impacted harder by phenomena like tides and watercurrents.

* When there is a big difference in actual boat performance the accidental combination of boatspeed and wave speed will favour one of the boats. Boats much slower than the waves will be sailing below there potential, boats sailing much faster will be held back by climbing each wave and the boat with almost the same speed will get an enormous performance boost.

* When there is a big difference in actual boat performance the slower boat will always start in dirty air and has to fight harder to get clean air which he needs to fully bring out his boat potential.
* The big variety of configurations will cause a spread of ideal conditions over different boat types. This leads to a situation where �this� weather is ideal for boat 1 and bad for boat 2 and vica versa. It will be hard to find conditions where both boattypes are really comparable. This principle is also encountered with respect to the shape of a race course. Some boats �like� gate courses others big triangles. This is especially a big problem when rating long distance races. It can even go to the point where some boats like short triangle courses and other like long legged triangle courses.

There is a way however to decrease and sometimes even cancel out these negative effects by applying some tricks. With respect to these tricks it is important to understand that the difference that a particular factor can have is often directly linked to the time that the factor is impacting. A good point to start from is to assume that the importance of a factor is determined by it impacting potential multiplied by its impact time. This is (partly) the basis on which it can be argumented that when handicap numbers between two boats are brought closer together that the accuracy of the handicap system is increasing disproportionally. When actual performance is closer together (as indicated by the numbers) than there are less factors that impact differently on both designs as well as less time difference in which the factor can impact. The overall effect on performance of all factors will therefor be much less. An example : When all boats finish within 2 minutes of eachother in a race lasting about an hour, than that wind change at the end of the race can only have a very much smaller effect on the overall outcome than when the boats were coming in in a time span of say 5 minutes. In the first situation the wind really needs to drop off very rapidly to make any difference at all. And the 5 minutes situation is also habouring a heavier positive feedback loop. The last boat in (at 5 minutes) is getting the greatest impact of the change and this impact is immediately enhancing the effect itself by elongating the impact time even more. This will mean that the last boat in will have had a disproportionally bigger impact than the last boat in at the two minute situation.

Now when the designs are also very similar in general setup then the offsets or even the errors in a particular handicap system are rapidly descreasing their impact on performance prediction. An example. Say that a particular system is making an error when rating the performance boost given by a genaker. Now when it rates two boats that both have similar sized and shaped genakers than both boats are subjected to the same error and will therefor both be rated wrongly in absolutely sense but rather accurate with respect to each other. They both get the same offset or error remember.

These principles are used in the F16HP framework. We are trying to make the F16HP boats very comparable to the F18 class (and similar classes like iF20) by :

? Giving the F16HP class a similar general appearance. Meaning a jib, squaretop mainsail, genaker, weight, etc all with the same ratio to the F18 class. This named setup is used by nearly all modern designs so F16HP will also be comparable to say the US Inter 20 class or International tornado classes.

? Bringing F16HP up to speed with the F18 class and thus cancelling out factors that only impact significantly when the factor can have different impact times between two boats. In short, equalling absolute impact. Not cancelling out but equalling the cummulative effect.

? Making sure that boat handling is the same as on other boats and that the F16HP has equal changes at the startline. Therefor a jib is needed otherwise F16HP will outpoint other modern designs. This will make the F16HP like all kinds of different race courses in much the same way as the F18 class and other modern designs do.

? Making upwind, downwind and beam reach equal to F18 and thus make the F16HP performance independend of the sailed race course. For this we use genaker size, jib size and platform width because their impact is independend of eachother.

Most of these points will also apply to the 1-up configuration without a jib although less prefectly with respect to the sloop rigged boats. It will however when your looking at other uni rigged genaker boats.

It is left to you, to check that the points of �enjoyable race� are also met by implementing these conditions.