Okay. So basically we have to decide what portion of the 16 year olds we still want to include in the F12's.

Here some demographic specs taken from the US center for Health statistics. US populace should be somewhere around the middle of the world. In general not very tall (like scandinavia) or vry short (like asia). This to provide some more scientific data to the discussion.

Boys 16 years
5% at or below 47.5 kg
50% at or below 62.5 kg
75% at or below 70.0 kg
90% at or below 77.5 kg
95% at or below 84.0 kg

Girls 16 years of age
5% at or below 42.5 kg
50% at or below 55.0 kg
75% at or below 62.5 kg
90% at or below 70.0 kg
95% at or below 77.5 kg

I restate (form earlier posts) that

Boys AND girls 12 years
5% at or below 30.0 kg
50% at or below 40.0 kg
75% at or below 47.5 kg
95% at or below 60.0 kg


So basically we have to decide what portion of the 16 year olds we still want to include in the F12's.


A few examples

If we want 82% of the 16 years olds to be in the competitive range then the F12 weight carrying ability needs to go up to at least 70 kg

If we want 63% (under 2/3rds) of the 16 years olds to be competitive then the F12 weight carrying ability needs to go up to at least 62.5 kg

If we want 50% of the doublehanded 12 year olds to be competitive (with careful combining of different crew weights) then the F12 carrying ability needs to go up to at least 80 kg. That while we "force" thje top 20% of this group to sail solo (they are above 50 kg and just entering the bottom weight range of the F12 when singlehanding)

Designing the F12 COMPETITIVE weight carrying ability up to 75 kg would allow us to include 94% of all 16 year olds but also 90% of of adult women and 67% of adult males (20 years).

If we copy the competitive range of the optimists, see link provide by Ncik, which is about 40-50 kg then less then boys=max10% + girls=max25% of the 16 year olds will be competitive. Resulting in just under 20% of this combined group being competitive. All others will have outgrown the 50 kg upper limit.



I have attached the demographics graphs for both boys and girls from 2-to-20 years of age. Women havse stopped growing by 20, while male may add some weight (but not length) up to 23 years of age. I propose using this data to fine tune the F12's.

Wouter

Looking over the data provided in the above post.

I think we see a situation developping where designing for the weight range of 50-75 kg is most smart.

We need the upper limit to be as high as at least 75kg to be able to carry 2 normal sized 12 year olds (80 kg would be better still). The same limit guarantees that 94% of the 16 year olds can still race the F12. Side advantage (marketing) is that the majority of parents can then also sail the F12.

The lower limit needs to be at least at 50kg to be able to start moving the top 20% of the 12 year olds into solo sailing the F12.

This 50-75 kg weight range will see the youths singlehanding from 20% at 12 to 94% at 16, the age range Ncik specifies as youths and as the target group for the F12.

If we drop the max weight to 65kg then 1/3rd of the 16 year olds will not be competitive anymore (compared to only 6% when the limit was at 75kg). The competitive participation level at 16 is dropping fast with each kg that is removed from the upper limit.

Personally, I see much reason to follow Luiz suggestion to split the fleet into two racing fleets. As in "below 60 kg" weight and "above 60 kg" weight. That should take care of the bulk od the performance inequality.

Wouter

I've read your post Jeff and I got a question about the following point.





How do you think that adding bouyancy to the hulls will bring the F12 out of reach of youths ?

I would agree with you, refering to "at the expensive of younger users", if I were proposing to increase sail area or something. But I'm not doing that.

I'm just proposing to increase the weight carrying ability of the F12 platform by adding a little more volume and freeboard to the hulls. And this will not have to add much weight at all to the craft. To put things in perspective; increasing the width and the depth (freeboard) of the hulls by 10% (keeping the length the same) should already upgrade the hulls from 120 max displacement to 145 kg max displacement. The difference between max 70 kg crew to max 95 kg crew. At the expensive of what ? 2.5 kg combined for both hulls. Adding only 1.25 kg combined leads to max 82.5 kg crews. The associated cost is pretty negligiable.

Gato is suggesting that he can make the current F12 hulls at 12.0-13.5 kg where the latter number is an actually measurement of his prototype hulls. That leaves 25 kg for everything else on the F12. If we are using carbon masts anyway then we don't need all those 25 kg to complete the craft at minimum class weight of 50 kg. In that case I say, use the difference to increase the volume of the hulls so we extent the weight range for the F12's (in chop etc). I mean it is better than adding pieces of lead right? It would surely improve the marketability of the F12 to the adults/parents.

Wouter

JeffS, It's relly nice to see somebody building instead of talking

If anybody wants to make performance comparisons; here some basic data concerning drag of a catamaran. Source ; MissNylex C-class catamaran research

Platform
Form resistance hulls : 15 % (sailing on one hull)
Skin friction hulls : 22 % (sailing on one hull)
rigging/fittings/beams/hulls : 11 % (parasitic drag / air drag)
Crew : 6 %

Sail related forces.
Centre boards : 21 %
Sails : 25 % (parasitic - form - induced = 1% - 8% - 16%)


By making the hull more volumous we would incur a small increase in skin friction drag for light sailors (youth). Form drag should see only a smaller penalty as the wider hull will also float higher in the water. Note how close to 50% of the total drag is totally related to sail forces that are unrelated to the volume enclosed in the hulls.

Roughly speaking increasing the width and height of the F12 underwater body by 5% (Upgrading max skipper weight from 70 kg to 82.5 kg) would increase hull related drag for the 70 kg skipper by a mere 1.5%.

A 10% increase in both dimensions would upgrade the max skipper weight from 60 kg to 82.5 kg (110 kg displacement versus 132.5 kg) and leads to only 2.5% more overall hull related drag for the 60 kg skipper.


That is the lesson that was learned in both the F18 and F16 classes; increasing hull volume is pretty costless as long as it does't push the ready-to-sail weight over the minimum class weight. Although the Viper F16 is proving that in the way of overall performance the latter is not much of a consideration as well. More a marketing disadvantage. However I feel we still have some leeway with respect to the ready-to-sail F12 weight and the F12 class minimum.

Wouter

Okay, I understand that this is solely intended as a funny remark.

However I still want to respond.

Too many times it appears that talking is considered a "dirty" endeavour. Now okay, I talk (write) too much. It is my job shall we say. As an academic I need to investigate the situation and formulate it correctly as to avoid the organisation from wasting resources on a wild goose chase. Especially one that could have been avoided with some analysis and talk before shooting off in all directions.

That is what I'm trying to do here.

Showing that we are needlessly limiting ourselves to a too narrowly defined F12 setup.

I hate to use the following example, but what would have happened if the F16 group only focussed on getting the singlehanded setup working properly instead of working hard to combining it with a viable 2-up setup ? I can guarantee everybody here that the "1-up + 2-up" capabilities is the biggest selling argument for the F16's. It is one of the big reasons the class has become a succes and grows everywhere.

I'm just trying to draw the attention to a similar potential with respect to the F12's. It could mean the difference between becoming succesful or fail. I kid you not !

Wouter

Spot on. If you trace the complete history of this "debate", back to youth development on the main forum, you'll find a repeating sentement amongst US sailors of...Why do we need another youth boat?

There was interest when this boat was heading in the direction of a platform capable of suporting a "light" adult. I have PM's from more than one American interested in building a prototype boat (at that time). I won a set of plans for a DS12 and have done nothing with them primarily because of the reduced weight carrying capacity. My target sailor was/is a 12yo girl who currently weighs 140 lbs. (63.3kg).

How much interest was shown when this was posted? I beleive the (or an) underlying concern is, what if my kid doesn't like sailing? Then what? I now have a "niche" boat that may be hard to get rid of.

I'm with Wouter on this one (no surprise). Open the range of usage up for the basic formula and it may be more a viable/marketable boat. Think more in lines of skegs vs. daggerboards, i.e. ease of use. Think more development of the unstayed rig, i.e. less time from cartop to water.

The Tabby looks nice BTW, and congratulations to those taking the initiative of actual building, continued design and development. Just thought I'd throw out why I've relegated myself to the sidelines on the F12.

(hijack off)

For me it's simple, there is nothing in the rules to forbit a fat cat, just get one designed and built. It would be a lot easier than to try to convince the existing designers and bulilders to do it for you.

and



How about this side view.

It was designed for 125 kg optimal displacement; this is not the same as MAX displacement. So the 50kg craft with a 75 kg skipper will have the optimal attitude in the water and have the optimal beam clearance. One that is the equal of the 5.00 mtr boats like the Nacra 500, Hobie Max and just a tad less then the F16's when all of these are sailed at 135kg crew weights. Its decks are only 250 mm wide for the 125 kg displacement. A 85 kg skipper will be equal to a 150 kg crew on any of these 5 mtr long boats. That is probably enough. I sailed the nacra 500 at 160 kg and it was fine.

I like this particular hull shape when opting for a skeg. The added benefit of the skeg is thatit takes only about 9 kg at the bow to lift the hulls up to roll the cat tracks under them. That is instead of 21 kg ! A huge difference for a youth boat I say. The skeg brings the fulcrum way forward and you'll notice that. The first mtr in front of the skeg will have an aluminum strip fixed to it. To cut down on keel wear. Of course the true hull will run its keel line in a curve from bow to stern just below the 2.70 measurement line. The skeg itself is just a 20 mm wide plate and protrudes further down.

What I need is a good method of producing such hulls but Gato is developing such a method with his foam plancking idea. That may just do the trick !

How about it John, too poofy ?

Wouter

And here an example of a similar type of hull with a skeg

This is a Nacra 500

The skeg is here smoothed into the hull shape but I suspect we can do the F12 hull shape as a daggerboard design and just omit the daggerboard trunks and inject a flat plate at the keel line. Make slots in the bulkheads and just laminate it in.

We may even do it in one go. Use the skeg to align the bulkheads.

Wouter

The market will decide what the class becomes.

My opinion is that it will not be everything to everyone, it will not be a small performance cat for small adults and a performance kids cat.

The small performance cat for small adults is a bloody tiny niche market if you ask me, and already has the hobie wave vying for those dollars and sailors. The performance kids cat is a currently untapped and potentially significant market, not only for business but also for introducing kids to sailing in general and cat sailing specifically.

You should build the DS12 and let your kid decide if she likes sailing. It is a worthwhile experience building a boat. Plus I see some strong movement in the class so I doubt you'll have a worthless boat at the end of it. Heck, build a Tabby if you want a boat that'll carry a bit more weight.

Regarding design issues, design it, promote it, put something specific on paper/on computer. There is a lot of leeway in the F12 concept, even for a small performance cat for small adults. The Tabby was designed on the cusp of the two weight ranges, not for this reason though, I just like the idea of a very full hullshape on cats.

Ncik, I will soon try to get you some better pics of the Tabby painted and all...

That is like two disagreeing generals saying to eachother, on the eve of a major battle, that each will do their own thing and let the end result determine who was right.

The typical end result of that analogy is of course that they will both loose and they will both have been wrong.

When you are not cooperating with eachother then you'll be much weaker then when you are.

Needless to say that after the battle there won't be enough survivors on the loosing side to regain the former combined strength.





The Hobie Wave has failed in area's outside of the USA. F12 still got a good shot at really becoming an international class.




That is wishful thinking in my opinion. The kids don't hold sufficiently large wallets or drivers license and I don't see any reason why we could expect major sales coming down the road with the way things are going now. That offer by a US producer has died for lack of interest and I don't think the rotomolded Vudu has met its threshold of committed sales yet. Even the concept of kit-building hasn't lifted off yet; although this is just another way of homebuilding anyway.

Lets not forget guys that we are already a few years down the road and Gato is the only at this time who is actually sailing an F12. And he is thinking about making a 14 footer for himself next.

Lots of potential ? Yeah, probably, but not much of that has been realized yet. At some time we have to put some rubber on the road and that means attracting COMMERCIAL BUILDERS. That is not happening yet.Lots of promises but no real breakthrough yet. We are going the way of the F14's rather then the F18's and F16's (who both had more then one commerical builder with boats sold within the year).




That is a mighty big gamble for most parents, if you ask me.

I will personally test the waters first on some second hand Optis or Laser 4.7's if it comes to that. And that is just what we wanted to prevent with the F12.




Yeah, well "a bit" is just not enough.

When I'm a dollar short it won't help much if you thrown me a dime.




This is the same "two generals" theme but with different wording.

I 'm not going to invest resources on a "maybe", that is if I would have them at this time (note I already did a thing like that with the F16's; the money runs out sometime).

This is a thing we have to do all together or we can just forget about it.

But what I don't understand really is why you would the following in a single post.





Either there is potential for it (light to medium adults) or there isn't.

The real issue is whether we ALL TOGETHER build and promote the F12 class as a versatile concept or completely gamble everything on the youths.

I'm out if it is the last and thus leaving only the downunder guys and Gato still in the mix. The Taipan was killed internationally by the same playbook.

With the current downturn in economy I choose versatility overf specialization any day. I think Darwin agrees with me here. Or in sailor terms; there is a reason why we see seagulls everywhere around the globe but not many kolibri's. It may not be the prettiest bird but it sure as hell is succesful.

Or if you will, that Marstom M18 (A-cat+spi) at 80 kg was a bloody nice concept, but marketing wise it failed disasterously when compared to the F16's. That is what I'm getting it. We took the 25 kg hit but gained a pathway to attracting commercial builders and to success. And lets not get started on the 180 kg F18's vs 120 kg M20's as an example to illustrate the same point.

Wouter

I'm deffenetly not abandoning the F12. I will build a 14 feet cat and maybe a 25 feet tri, but that has nothing to do with the F12:s,
The case is that Wouter wants somebody to design (and almost build) a F12 cat that he can sit on himself.

Yes, that is the standard accusation that is thrown at me regulary.

Still, it doesn't adress the points I made in my earlier postings about marketability and dare I say viability.

It is also a bit weird as an accusation, as I think I'm the only one here who has actually founded, build and grown a viable international sailing class once before. Not to mention building a class complient prototype craft that I can actually "sit on myself".

I'm not making these comments because I'm somehow lazy or whatever. Truly, I'm making them because in my opinion the F12 class appears to be failing and there is still time to do something about it.


But I think that I've said my piece and not much more is to be expected from repeating points made earlier.

So I think I'll leave it at that.

Thanks for answer my questions Gato and I look forward to looking at the building pics of your future building plans.

Wouter

Sweet! Thanks Gato.

The class will be whatever it decides it wants to be, but I do suspect it will become the kids cat.

[quote=_flatlander
There was interest when this boat was heading in the direction of a platform capable of suporting a "light" adult. I have PM's from more than one American interested in building a prototype boat (at that time). I won a set of plans for a DS12 and have done nothing with them primarily because of the reduced weight carrying capacity. My target sailor was/is a 12yo girl who currently weighs 140 lbs. (63.3kg).
How much interest was shown when this was posted? I beleive the (or an) underlying concern is, what if my kid doesn't like sailing? Then what? I now have a "niche" boat that may be hard to get rid of.
[/quote]
John it'd be great to build a higher volume F12 if you want to, it would just be another version that can compete under the same rules. The F12 can be altered to suit any use in any region of the world within the very loose rules.
The F12 will easily carry your daughter and a crew or you and your daughter for fun, don't look too much at the figures trotted out but try a small cat yourself if you can. I sail on my lads 11ft Arafura with him and posted a video on this forum of us sailing you can clearly see me jump on it with both of us weighing 140kg on the same side and it not looking unstable or risky. The Arafura doesn't have the bouyancy of any of the F12's. My daughter that sails the F12 is 59kg and she will have a crew taking it to 100+ kg. The technical figures for optimising the F12's is all fine but does it really matter that your 1 inch lower in the water and by using that weight correctly very safe in nearly any weather.
Any adult can jump on this cat and have fun let alone your daughter and a friend.
Wouter you did well to adapt the Taipan 4.9 design into a class thats world wide and if your success with the formula continues you will probably have as many F16's sailing in 5 years as there were Taipan 4.9's sailing 5 years ago. Your input is valuable but its not the same as building a completely new class of cat for kids, now that we have the kids covered It'd be great if you can adapt one of the designs or come up with a new one to suit your regions needs or heavier adults that want to sail it.
regards

I hate to say it but yes being 1 inch lower in the water can be very significant. Of course the boat will never sink when you pile the weight on but it will start to display other undesireable behavior. Examples are ; wave slapping with the back beam (BIM A-cats, older F18HT's, Nacra 500 with lots of weight) or taking the chop on the mainbeam (Taipan 4.9 when 2-up and heavy). The boat can also get very weight sensitive and allow backward flipping when tacking (Hobie 16). Or bad dive resistance.

Interestingly enough all these issue are associated with too little volume in the hulls, never with too much volume. That is one of the reason for my earlier statement that it is relative hard to overdo it with respect to volume.

Wouter

Yes, I understand that the situation is like that.

Will leave it at that or further explore actually building something like this


Regards,

Wouter

The Tabby as The DS12 can take weight up to 70-75 kg depending on how much weigth you build into the boat (displacement 110-120kg)
The funny thing is that some of the people arguing for bigger min weight for the cat (60kg) also wants the boat to be able to carry more weight.