Kids F12

Mark I'm hoping that as long as the hulls look modern and can handle the unstayed rig, it wont be too hard to reinforce sidestay and forestay positions if neaded during the building process, to upgrade the rig anytime. Then I would have cats suitable from 7 up to learner adults. I have the tools, workshop and have committed myself to building at least one cat with traps next winter and would like to setup a production line for the club if possible. I already have Chris's option and would love to see RG's so go for it guys lets see your plans <img src=

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regards

The tubular frame is also a good place to rig a spray and wind deflector if desired, at the cost of some aerodynamic drag.

Is there a way to make the frame somehow more atractive? Given enough time, the best engineering solution will become the standard of beauty, but in the short term style is a key marketing issue.

OK, here is my design, a bit modern for sure, but 11 kids have seen it now and all with no exceptions wanted one yesterday. Whether the rest of the planet is of the same mind, only time will tell.
I designed this so it will have 2 hull options, most of the pic's that follow are of the hard chined version because that is what I believed would spark the initial interest, the round bilge version (similar profile) is based around my new F16 design with the appropriate changes and is more geared to older kids, a conventional rig and traps, perhaps even a kite. I'll finish this version as time or interest permits.
To get the round bilge one out of the way, its the first pic, all the rest are of the hard chined version.
I should also note that everything is within Wouters posted guidelines except for the luff length which is just a bit longer.

Cheers
RG

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The luff length as given by my was determined by the stiffness of the mast and what I know will work from my class 5 landyacht sails. It is not a hard boundery. I'm already thinking to stiffen up the mast to have it bend less and allow the battens to pop more easily in light winds. This desire coincides with the desire to use the same section for the beams and the bottom part of the mast.

How much is your luff longer ?

Wouter

Thanks for sharing RG. What's your target crew weight? Also curious about the narrow transoms. What's the thinking behind that? I know your A cat hulls are also narrow at the stern, but also through the whole length I think, so this seems like an interesting departure.

Mark,
65 kg would be the max if you raced it but I put enough in it so its comfortable at 120 kg (kid & adult) also. Best range would be 40-50 kg.
Hull transoms and/or narrow hulls have nothing to do with narrow, its all about slightly lower drag and minimizing the pitching. The 2 hulls show are actually quite different but both do the same thing more or less. The round bilge hull has more than 8% less WSA, is more than 6% fatter and almost 10% more WPA and a fatter transom than the hard chined version, yet the pitch rates are almost identical (within 1%) so just looking at physical sizes has very little to do with the dynamics. The thing you might have missed is that the chine goes downwards for a long ways aft before it rises again, is quite good for keeping the transom out without having a big fat shape at the back that just drags water. The other thing to remember is that if you can keep the pitching under control, you don't need a lot of reserve buoyancy at the back to counter stuff thats not happening.
Wouter,
197mm longer
RG

I would have thought that the narrow transoms would help sit the back down when your aft in a blow and make keeping the bows out easier, no ?
Aerynt

That's really great! I want one too! There are hundreds of positive things I could say, but they wouldn't help as much as some constructive observations:

1) That gooseneck looks like it would

bite

the fingers. Would it make sense to use the Laser standard system - and perhaps the same boom as well? Maybe another boat's standard system that fits?

2) Each mast support tube is curved near the extremity to enter the deck perpendicularly, when a straight tube cut in the right angle would be easier and cheaper to manufacture. Is this for aesthetic reasons, to provide a better holding point when hiking/trapezing, or for yet another reason?

3) Why the rudders seem to have no Ackerman compensation? It would probably facilitate manouvers.

4) I'd like to know if what Wouter wrote about daggerboards stands true with this design. How much would be lost if one daggerboard was eliminated? And without daggerboards? Would it still beat a Laser? In my opinion, the boat just has to outsail the Laser. Faster than that might be too much.

5) Is there anything else that could be done to simplify or improve its maintenance, use and safety?
Built in beach wheels that double as fenders/bumpers when raised? Hard tramp? A **** for safety? Back rests? Single rudder? More grab points for beaching? Butterfly nuts in the bolts that attach beams to hulls for easy assembly? Standard righting pole? Reefing system? A shark's mouth painted in one bow and a big smile in the other? (just brainstorming).

Great job!

Very interesting...great start.

Comments and Questions:

1) Any reason for not putting more volume lower in the hull?

2) The profile looks hot but the head on view makes the hull cross section look quite dated… As if you have a very up to date profile, but a 20 + year old hull cross section.
Is picture # 123637 depicting the same hull as shown in picture # 123641? It may just be an optical illusion… but the picture shown with the rig on it looks like a “stretched out version of the non rigged hull. The picture of the hull ( #123637) looks stubby in comparison to the hull in picture (# 123641)

3) If you are going to have dagger boards why would you want such a deep V hull section? Small mono hulls are fun because they tack “on a dime” Would not a flatter bottom shape make the small cat tack much easier?

Best Regards,
Bob

Luiz,
yup, the gooseneck is a mess but the piece it's mounted on is tricky, first the tube there is a clamp (2 half shells that open so you can rotate the mast into place, this just leaves the aft half to attach the braces to and you can't rivet anything to it, so whatever is there will have to be welded, next the right angle at the outboard end of the braces goes into a molded recess so the whole brace just drops in vertically, this gives us more bearing area and holds the brace in position while you rotate the rig up to the clamp, seemed like a better way than trying to juggle to pieces that can move at the same time.
As for the rudder compensation, I just hadn't got around to doing it yet, rudders came off the F16 design which has canted hulls and so its not necessary.
As for boards, a quick look showed that the leeway angle was excessive without them, so they got put in.

Bob,
Lower volume is no problem, just use the round bilge version of the hulls, I had thought that the reason to do hard chine hulls was so that it would be easy to make these from playwood and keep it all cheap? The hulls are all the same in the pic's, its just the perspective. As for the deep V, due to entry limitations that are inherent in what you can twist play into, the waterline sections in a hardchine boat are quite draggy, you can offset that a bit by keeping it narrower but that gets you a deeper hull. I don't think there is a perfect answer to this one, it really just gets down to your choices and what you want.
Cheers
RG

RG those hulls are fantastic what sail area are you considering to be maximum and minimum
regards

Jeff,
as per what appears to be the consensus here, sail is 7 sq.m but I could see going as high as 8.5 to 9 sq.m if you had a bit more weight on the boat.
cheers
RG

apart from the fact that it adds a little scale to the picture, every boat should be sold with one of these
cheers
RG

RG your a very naughty boy in two ways. Firstly my children and I would be ecstatic to hike out on that boat not really sold on the bars yet but happy without traps. Secondly I was hoping that boys would consider that rocket to be better than sex and therefore only be after my daughters for their boat <img src=

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Why have a gooseneck at all. The mast is non rotating and the boom can even be totally free handing.

I think it is actually a drawback to use a conventional gooseneck, it will only prevent the rig from totally weathervaning or even being sheet out fully when on a dead downwind course.

As the mast section is round, one can just have a fitting on the end of the boom that is a fork and have that slide over the mast. Well, at least that is how my design has it.

Wouter

Allow me to play the devils advocate.

I did some spec checking and I compared some aspects of RG's proposal to the stated design goals.

RG wrote to me that he used a copy of the Moth rig in his drawings. The Moth rig is not an unstayed rig and it is highly unlikely that an unstayed mast will remain as straight a given in the pictures when loaded up. The Moth rig is actually 8.00 sq. mtr on a 6.250 mtr mast. More specs of other boats can of course be found on : http://www.xs4all.nl/~whijink/F12/

RG's design looks very well and is very succesful in attracting the sailors to the F12 idea. That is a very important development. Without some good promo the F12 project will be struggling. I too appreciate that very much.

Still, I'm a little bit at a loss in how to incorporate this design in the larger F12 scheme. Afterall it is basically his LR2 A-cat design scaled down in size with a Moth rig on it. Neither of these components is particulary inexpensive or easy to (home)build. But homebuilding is indeed regarded as the way to kick-start the F12 class till a more professional builder can be convinced to invest in the project. Of course the chined hull construction, as also shown by RG himself, is alot more in line with these design goals. It may be wise to focus on that part of the design and forget about the fully rounded version as I fear it will really problematic to prototype and build the class on the fully rounded version. We shouldn't give people to wrong idea by showing that version around to much either, for I fear they will never

get

the fully rounded version.

At this instance we must also appreciate how problematic it can be when the class is started and grown initiallly on the chined hull version only to have a professional builder do the rounded hulls later. Will all the boats build in the initial stages by outdated by that, how will their owners react to that, will they even consider building the boats when they are aware that such a thing may happen later. Such considerations are simply skipped over now.

RG comments on how chined hulls are draggy, or at least when compared to say his fully rounded hull. This may give further weight to the problems of transitioning from chined hulls to rounded hull later in the existance of the class. But I also believe it misses the F12 point somewhere. Indeed it stands to reason to expect the chined hull to be more draggy, but how important is this in the greater scheme. A Hobie 16 is seriously outdated in relation to say an F16 but the performance difference between them is only 15 %, most of it coming from the differences in the rig and overall weight. How much of that difference is the result of having inferiour hulls and lacking daggerboards ? Take a look at the Paper Tiger, a chined design that nobody regards as being slow.

This leads us to the following question, which is a very important one for the F12, how much additional cost and building effort is say 5% additional performance worth ?

It shall be obvious that I take a totally different take on things. I feel that it is far more valuable to have a very easily and inexpensively build F12 and work that quality into class growth. I don't believe that losing an X amount of performance (limited to 15% at max) is

worth it

if the class is strickt One-Design and will be beating a laser dinghy anyway.

At a certain point enough is enough and at that time there is more to be gained by optimizing the building time and costs. For a concept (sailing class) to be succesful, the whole picture must be right not just a few parts of it.

Welding ? Something I really tried to avoid in the F12 design. Homebuilders can not easily do it. It is also not needed. The same with bending the tubes.

Daggerboards have been covered already. Interesting to note is that assuming a chined hull is more draggy then it may well be more resistant to sideways slip ! I've sailed boardless cats for a long time and the pointing difference between say a nacra 5.7 and a nacra 5.8 wasn't very large at all. It is to us to decide whether the difference is large enough to decide to use daggerboards on the F12. In this balancing act we must not forget that daggerboards are a custom made item and do indeed add building costs and complexity to the design. They are also one more thing to get broken. To us the decision whether the advantages outweight the drawbacks.

Four of the more important design goals as stated explicetly last january were a F12 that could be build for 3000 Euro's or less by a relative homebuilder in 100 hours or less, fully rigged and derigged in max 5 minutes and fully assembled/disassembled in max 10 minutes. I still believe these to be critical for the succesful launch of the F12 class; otherwise I too would just have taken a CAD drawing of an F16 and scaled that down while replacing the 6 in the class logo by a 2.

Wouter

Interestingly enough the Moths have similar bars as well an nobody is critical of those. I think we have a case of obsessing over a single item here. Most likely nobody gives a damn once the design is sailing. Notice how the Moths even use a bar going forward to stabilize the bottom of the mast. Even 18 foot skiffs have used rods for the same reasons. And yes that is Rohan Veals new Moth design and he is sailing it in the second picture. Now everybody feels it is the epithomy of coolness.

Wouter

How much harder to make the rounded hulls? are we talking another day in the building or another week? That boat is fast out of the water! RG do you have plans on the building of it yet.

Yes my kids want one too! <img src=

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But the high aspect dagger boards are going to get whacked… I caste my vote for going with low profile boards (2/1 max.) for the kids.

Aerynt called me tonight with another angle, his eldest son thinks it will be a babe magnet and is very happy about it <img src=

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RG

As a kid we used to have a half round welded to the boom that sat on an upturned oar rollack (plastic) that was riveted to the mast, vang held it in place and while it got chewed up in a season, could easily be replaced and was cheap. Problem here is that we have slip fit everything and you can't rivet into slip fittings....one way or the other even with this suggestion, you have to weld something
RG