JeffS and his kids all took a spin on the Open last March. I've had my neighbors say they'd like to have one to, as advertised, be the next step past the Opti. Tough to justify the $1,300 hull only price when you think "how long will this 8 footer keep Johnny happy?" When will he be wanting for a Laser? Tough for just one of the bunch to justify buying Open hull only if the others don't make the move as well. They've got solid opti (OD) sailing and numbers, so why upset the apple cart? This is where the F12 will shine, I think it will satisfy a broader age span.

Agreed the Open looks sharp, some of these F12 designs look good too. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" /> The F12 must look fast to survive.

Mark II CTMD F12, sorry I'm not as good on rhino as RG. Jeff, yes you could use rotating centre boards, however I will show daggers as standard.

Chris, since you've stuck with a stayed mast and dolphin striker, are you considering the possibility of a trapeze?

And target crew weight is still 45-50kg, yes?

Mark,

target crew weight is still 45-50kg (I've left some extra freeboard in to cater for heavier crews or two people).

The concern with trapping is the extra compression load applied to the rig. The rig I'm looking at is designed for a two person, one on trap dinghy (MG14). With a 60kg person hiking on the cat the mast will experiance similar loads to what it would see with one person trapping on the less stable mono. I've gone with this mast at this stage because its similar in shape to most modern cat wing masts and because fully rigged it will be less than 6kg (a weight that will enable kids to rig their own boats). If you wanted to be able to trapeze its only a matter of talking to whoever you buy the extrusion off and discussing what section they would recommend (you'll propably end up a couple of kgs (4lbs) heavier at the most). The beams and dolphin striker as specified would be fine.

Ok thanks Chris. Presumably no expectation that trapezing is required from a righting moment point of view.

BTW, a question that I also asked of Phill a while back - what do you see as the next step for kids moving out of your F12, either in terms of existing boats or design parameters for a new boat?

Mark,

a 45kg kid sailing this boat would be approximately equivalent to a 70kg Paper Tiger sailor in terms of the ratio of righting moment to heeling moment. While obviously not required I'd also encourage people to build a reef into the main sail so that the boat could be calmed down when required.

Where to next is a difficult question. I competed in my first adult Hobie nationals as a 45kg crew at 12 years of age on a Hobie 18. The obvious answer is a 14' boot (F14) but for most of these you'd want be at least 65kg so depending on the kid and the location you would either keep them on the 12 until they become big enough for the 14 or put them on a 14 and be willing to lock them in the car on windy days.

In the southern states of Australia I can see a very beneficial development being...

F12 --> Paper Tiger --> Mossie --> A cat/ F16

Thanks Scarecrow great looking boat, I was really for traps as you know. We had a light day a couple of weeks ago and I let the kids captain the A, with me not recommending anything just sitting and getting them on & off the beach. They didn't want harnesses or to hike out they were happy with the speed sitting in. They wanted lots of turns, capsises and fun which they had, regarding the dagger boards that I was concerned about, they stopped the boat well of the beach to pull them and release the rudders, my plan is to have a few different length sets of daggerboards to suit experience and kick up rudders. Just from observation I think it was me that wanted them on traps <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" />. The kids would happily sail your boat. As for me the Olypics decision has brought me forward and am currently getting quotes on bulk gear for a build starting early in the new year
regards

Just a stupid question. There is a lot of talk about crew weight, rightning moment and so on. Are you basing these on solid hydrostatic calculations or are you just preforming advanced guesswork?

Good question Gato <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

a composite set of hydrostatics for a couple of winning Uni-Rig boats would look something like this:

LCB 46.7% (fwd of transom)
LCF 45.5% (fwd of transom)
Cb 0.511
Cm 0.809
Cv 0.946
Cp 0.632
Cwp 0.754

My design which is geared more towards the heavier weights performance wise (to keep the heavier (50 kg+) kids from getting bored) looks like this right now:

LCB 47.3% (fwd of transom)
LCF 45.3% (fwd of transom)
Cb 0.393
Cm 0.619
Cv 1.432
Cp 0.635
Cwp 0.797

Would be interesting to see Grob's, Scarecrow's and Phill's numbers also if they have them. I don't think we need to hide these parameters as everyone will eventually see them anyways when we publish the plans and anyone can back calculate them. I would have included something similar to my design, but I don't have any lines handy from which to build a model to compare with, if anyone has a CAD model of something even close, please post it it and I'll throw a hydro's model together for everyone to look at.

Cheers
RG

Incase anyone isn't up to speed on the above abbreviations

LCB = longitudinal center of bouyancy
LCF = longitudinal center of flotation
Cb = block coefficient
Cm = midships coefficient
Cv = volume coefficient
Cp = prismatic coefficient
Cwp = waterplane coefficient

Cheers
RG

Just occurred to me that perhaps some others may not have some hydrostatics software, if so, just yell and I'll do what I can to help you out with getting some numbers for your hull. An igs file of your shape will generally get me started easily.

Cheers
RG

Hi Scarecrow

I actually really like the look of that, without me trying to study between the two, what changes have you made in regards to Mk1 to Mk2.

I'm all for centreboards and stayed rigs, I didn't have any trouble throwing up an stayed rigged aluminium rig when we were kids.

Are the plans available for this one? Also include a set of plans for a bigger shed, I think I'm gonna need it <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Regards

Makes sense, although a Mossie is an F16, right? If F12 is successful as a younger kids boat, maybe it could be the springboard Darryl and Bernie need for the F14, and from there people go to F16/F18/A depending on their preference and to a lesser extent on adult body weight.

Thanks RG, now the things starts to look more serious...

mk II

LCB 46.6%
LCF 42.4%
Cb 0.475
Cm 0.885
Cp 0.639
Cwp 0.721

For those who are a little new to this. Traditional theory is that keeping the LCF and LCB as close as possible will minimise pitching and keeping the LCF as far aft as possible will help prevent nose diving.

A high Cp is traditionally considered quick and a low one is considered easy to turn.

Matt Plans and kit are coming on line over the next couple of weeks (see pricing thread) the price will be slightly lower for the kit as I've eliminated one sheet of ply.

changes between two versions are a basic tidy up (first one was done very quickly) and a reduction in freeboard and some tweeks to the internal structure.

Chris.

I am avere that I might mess the things upp by this, but would it not be a good idea to go for a cat with a little bit more wolume like RG and for the rig to make it like Scarecrow. This would make the boat for a larger range of kids. Say small kids 2 up and older kids 1 up. That would make the platforme last a little bit longer, and also make it more adapted for raids.

Gato....already working on that <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />
Cheers
RG

One thing we should all be thinking about, and Wouter brought it up to me in an email because it hurts the F16 class, is a revenue stream so that those running the class have some funds to help promote and develop ideas/racing etc.

Wouter wanted to do this with common production of stuff like masts, braces, booms and sails etc with a small portion going to the class. While this is a great idea, its sorta goes back to limiting what all of us who are designing various stuff believe in.

My suggestion is that all of us designing each of these designs, add a small fee ($50 ?) that goes directly to the class treasury so they have some funds to pay for things like Scarecrow and I are currently helping to fund because we can. This also implies that we had better get our act together and elect some people to run stuff in short order, finish the class rule <whatever that turns out to be> and generally look a whole lot more like a class than a bunch of people who are in love with a concept.

Later, as the design and experience spiral narrows and we end up with more designs that incorporate more similar features, perhaps we can utilise some of Wouters idea's also.....or if any of you have other bright idea's for adding other possible revenue streams for the class, please speak up.

If you look at the F16 forum right now, they are having a discussion on how best to promote themselves further, but as a class lack the funds to do it in a major way....one of our primary goals as a class from the start should be to give those who run it, the tools (read $) to help get it started on the right foot.

Even small $ could get us the equivalent of the BIC video that we could saturate the web with and get the parents with the $ aware of what we are trying to do.

Cheers
RG

Sounds good to me, a small "licens" fee paid when you buy the plans makes it equal for everyone.