Gato,
As far as I'm concerned you deserve every praise that is coming to you. A great deal of designing is just giving something a try and see how it comes out. You are almost singlehandedly doing that portion for the F12 class.
Ohh, I forget to ask last time. What is your body mass and length.
I ask as it appears the Tabby lifts just fine with you on board. Now I don't expect you to be of my stature but nevertheless ...
As for adult sailing ... I think a 14 feet version with a moderate sailarea and a spar not exuding what you can cartop would be the solution, ... would benefit from a higher freeboard.
I’m thinking of building one for myself
Now, what I'm personally lacking in the "just build it and see" department I make up for in analysis. That is what I did in the F16 class and what I also did in the F12 class.
I actually believe that the F12 can work well for adults. Meaning 85% of the adult women and about 50% of adult males (when keeping the 2.00 mtr width). You may well fall in the last category.
The 7.00 sq. mtr sail area on a 6.00 mtr stick is not really limited to youths. Afterall the laser dinghy has the same size rig with a very oudated sail design and is only 60% slower then a fully charged F18 racing catamaran. This Laser dinghy is actually sailed best by a 80 kg skipper and can be very fast downwind (where it is much less limited by righting moment of the crew).
Additionally, the loading of the F12 hulls and rig is on a par with a 135 kg crew on a F16 when you are around 60 kg - 75 kg. They specificantion that may need to be adjusted is the overall width of the F12. For skippers over 70 kg it is best to make the craft only 1.80 or 1.75 mtr wide instead of 2.00 mtr (and just keep the same rig).
The following combo's of boat weight x mast height x sail area x crew weight x width are very entlightening :
The named ratio is the righting moment of the crew on the luff hull devided by the heeling force of the rig when sheeted tight. A smaller ratio indicates a more overpowered boat.
50 x 6 x 7.0 x 60.0 x 2.00 => ratio 4.05
50 x 6 x 7.0 x 65.0 x 2.00 => ratio 4.28
50 x 6 x 7.0 x 70.0 x 2.00 => ratio 4.52
50 x 6 x 7.0 x 75.0 x 2.00 => ratio 4.76
50 x 6 x 7.0 x 70.0 x 1.75 => ratio 3.96
50 x 6 x 7.0 x 75.0 x 1.75 => ratio 4.17
50 x 6 x 7.0 x 77.5 x 1.75 => ratio 4.27
50 x 6 x 7.0 x 80.0 x 1.75 => ratio 4.38
50 x 6 x 7.0 x 85.0 x 1.75 => ratio 4.58
50 x 6 x 7.0 x 70.0 x 1.80 => ratio 4.07
50 x 6 x 7.0 x 75.0 x 1.80 => ratio 4.29
50 x 6 x 7.0 x 80.0 x 1.80 => ratio 4.50
50 x 6 x 7.0 x 85.0 x 1.80 => ratio 4.71
Other boats in the cat scene have :
109 x 6.78 x 11.12 x 2.35 => ratio 4.04 (Hobie 14 when not trapping; ratio is even higher when trapping ; 5.03)
104 x 6.40 x 8.64 x 2.15 => ratio 4.92 (Hobie Dragoon, 3.91 mtr length)
100 x 6.50 x 9.30 x 2.13 => ratio 4.40 (Paper Tiger, 14 footer no trapeze allowed by class)
118 x 6.10 x 9.20 x 2.13 => ratio 5.08 (Hobie wave, 3.98 mtr length no trapeze allowed by class)
An F16 sloop sailed 2-up and double trapped at 135 kg crew weight has a ratio of 4.13
An F18 sloop sailed 2-up and double trapped at 150 kg crew weight has a ratio of 4.33
Most other modern performance boats are in the range of 4.00 to 4.75 with respect to these ratio's, that is excluding the specialized singlehanders like the A-cats (2.65) and the single handed F16 (3.13) when either is sailed by a 75 kg crew. Note that both the A-cat and F16 1-up are beyond any doubt overpowered boats requiring skills to control. A 40 kg kid (average 12 year old) singlehanding on a F12 will have a ratio of 3.09 ! And he will share the same power-to-drag ratio of a 95 kg singlehanding skipper on a F16. Do we really want to see these toodlers doing 15+ knots while being all on their own and on the edge of control ?
The basic conclusion is that the heeling power (and power-to-drag ratio) of the F12 rig (when placed on a 50 kg platform) is pretty high compared to other designs. That is when sailed by an light to medium sized adult. And sailors seem perfectly happy to sail the Hobie 14, the Hobie wave, Hobie Dragoon or the Paper Tiger. In fact the dragoon is the true youth class < 14 years at the moment. I've sailed both the Hobie 14 and Dragoons as an adult and these are undoubtably fun boats. In fact, the loading per meter waterline length of the F12 with an adult on it is still south of the same ratio's for the other boats.
In fact, the Paper Tiger has the lowest value for this ratio of the alternatives and you'd have to load up the F12 to 156 kg to achieve parity. Achieving a total of 117.5 kg on the F12 (50 + 67.5 crew) achieves drag-to-sail power equality to the Paper Tiger when that boat is sailed by a 75 kg skipper.
The Texel rating system predicts very similar performance for either boat; both Hobie 14 and paper tiger are at rating 135 and the F12 with an adult is at 136. That is under 1 % speed difference around a race course.
In all honesty, I have never understood the large focus on kids when it comes down to the F12. It is far more suited to the crew weight range of 55 kg - 75 kg then for kids of 12 years of age (or younger) who have their mean at 40 kg and of which 85% is in the range 30 kg - 55 kg. Below 10.5 years of age and 95% is below 55 kg (their mean at 35 kg). Although, this also means that two kids crewing together on a F12 will be right back at the ideal weight range.
I hope I don't hurt anybodies feelings but there seems to be a persistant myth that hull length has a direct relation to the age of the crew. As for example that a F12 is for 12 year olds or younger, F14 and F16 for teenagers and F18 for adults. While in reality, the F12 (as it stands) is for best suited for teenagers, females and light males, F14 and F16 are for light to medium mixed crews or medium to heavy 1-ups and the F18 are for medium to heavy doublehanded crews including all male teams.
In fact, Phill Brander was right with his Blade F12, fitted with a 5.5 sq. mtr sail, as intended for 12 years old kids etc. This setup has a ratio of about 4.0 (for a 40 kg skipper and 6.0 mtr mast) and that is what I would put these kids through at maximum if they are to be solo sailing the craft.
To summarize a long explanation. I think the F12 could be a perfect adult (light to medium weigth) solo craft as long as the hulls are designed for the associated weight range and have sufficient freeboard for chop. The rig dimensions are fine as it stands and by making the rig light enough the diving of the platform shouldn't be a problem either. Of course, a rating of 136 (or only 20 minutes slower then a F18 or A-cat (rated at 101) that both completed a windward-leeward race in one an hour is really nothing to be ashamed off either. You will still be doing 11+ knots and beat the laser dinghy in the race by 15 minutes. The current 14 foot alternatives aren't going much faster at all. Ergo, The F12 power-to-drag ratio under an adult skipper is fine too.
Wouter
