Body mass data for boys and girls can be found here :

http://www.xs4all.nl/~whijink/F12/

Specific :

http://www.xs4all.nl/~whijink/F12/Body_measurements_boys_2_to_20_years_old.cj41l022.pdf
http://www.xs4all.nl/~whijink/F12/Body_measurements_girls_2_to_20_years_old.cj41l022.pdf


Just for interested readers that may want to review this data.

Wouter

My initial replies.




Is covered in the current design.

However, may not be allowed in strickt F12 OD racing on international level if we ever get to that. Decision here has not been finalized yet, wanting for more experience to have been gained before making this decision.





Current design used a sleeved sail and as such the sail is fitted to the mast when it is still laying on the ground. The bottom of the mast is then attached to the mainbeam by a bolt (or was already attached when the sail was fitted). The rig is then erected from the front and falls into the V-ed slot of the push rods and a single bolt secures the whole setup. Derigging in reverse order. As the design uses no stays the front of the boat is fully clear and it is easy for a person to manouvre here.




My calculations show a different situation. On a boat of this size boards may actually make a very small difference. The design decision here is whether the difference that exists justifies the additional costs, additional building effort, additional risk of damage (warrantee) and the additional weight.

I fully understand that people may do a different balancing but I eventually found that the small difference was not worth the other drawbacks. Remember the F12 as it is now will outpoint the Laser-1 dinghy already. Adding boards may only give an extra 3 degrees pointing at max. It can not be compared to say fitting boards to a 18 foot round bottomed beach cat design were a difference of 10 degrees can be attained.




My initial hull design had them as well; but I was not convinced that the additional building effort was worth it. If anybody finds an easy way to do it then by all means lets have it. I initially concentrated on making things as simple as possible trying to get the weight, cost and building effort down to a minimum.





Please explain further.

I do believe that I understand what you mean, I have such a setup on one of my landyachts, but I want to be sure. It is a very good idea actually although it will complicated errecting the mast. On the otherhand, the rig as designed now also allows the sail to be fitted when the boat is flipped on its side while the mast was prefitted to the platform. I tried to avoid this way of rigged as I'm told most sailors don't have nice clean grass lawns or sandy beaches to rig on.





These hard points will see about 500 kg of loading (comparable to stay chainplates) and I'm not sure that wind surf mast steps can take that amount of sideways loading. I suspect they don't. Also the design of these hardpoint is pretty straight forwards as we stand now. They use standardized marine eye bolts and threaded forks.





Can be done with the current design. The mast can be lowered towards the front by removing the single retaining bolt (or two clevis pins in an alternate design) and it will lay flat in front of the boat with the sail attached. It so designed the sail can be removed easily by pulling it forward. This is basically the standard rigging and derigging method. The mast itself can be taken apart into three seperate sections in the span of literally 5 seconds, just as with the laser dinghy mast.





That is the reason why the standard design doesn't use a windsurfer rig but a rig much like the class 5 landyachts. Basically this rig can rotate around the mast indefinately. As such it can completely weathervane. As it is fully battened it won't flap about. Practically, one can even leave the boat fully rigged without risk of flipping it or damage. In an emergency just unsheet the main sail and let it weather vane completely. I feel this is enough emergency precaution.





Can you tell that I've been working on this project for a while now ?

Seems my design is already pretty close to what your kids desire. Apart from some styling that is.

Wouter

... continuing ...

Jeff,

I want to learn more about the Bic rig.

It seems the Bic rig is a fully battened sleeved sail and I'm having trouble getting the right amount of draft into that rig in winds below 12 knots. I fear I have to use camber inducers to get the rig to perform well. I rather do without these.

How does the Bic rig solve this issue ?

Do you know or can you describe all the elements used in the Bic in detail ?

Thanks alot.

Wouter

It might be prudent to consider designing an F-12 something along the lines of Darryl Barrett’s outstanding F-14 Alpha Omega (a greatly simplified version of course). Any one who has seen the video of his boat would have to admit that he has the F-14 is dialed in…at first look it might appear as if his hull design is a bit boxy, but after studying the video you find that every aspect of the design is there for a reason… it is a good study on optimizing a small cat for maximum performance.

As a side note, anyone who wants to get kids interested in cat sailing should show clips of Darryl’s F-14 video, after seeing it flying around few kids would ever want to go back to an Optimist or Laser. It proves to the kids that you can go really fast on a small catamaran without an 18' + boat that weighs 400 lbs.

Regards,
Bob

G'day Wouter the Bic rig isn't that good with any weight on it the shape of the hull gets it plaining really easily with small kids or in big wind, guys that saw me have a hoot on it in conditions that the rescue boat didn't go out in couldnt get it going the next day in moderate conditions. Its just a windsurfer rig really. The reason I posted really was the fact that as a novice but enthusiastic sailor with 4 kids being encouraged to sail, I had tried it was looking to buy it but was put off by the supprising weight of it. I really want a stack of light weight easy to repair reasonably strong cats which keeps bringing me back to carbon and foam hulls, side stays etc
regards Jeff

Bob,
Like the Glider.
13 ft long with modern sail plan, sails well with or without C/Bs, uni or sloop rigged and even a spinnaker if you want.

The target weight was in response to the talk on the F12 forum at the time. I did that sketch and then did nothing as the F12 appeared to be heading (at a rate of knots) away from what I considered was something worth spending my time on. The return to a genuine kids boat has re-ignighted my interest and I've set aside approx 1 hour a day (until its done) to produce a finalised design. The kitset price as quoted is based upon the original files and will probably come down with the final product. The "optimum" weight for the newer hull is marginally lower (45-50) but not much, as I envisage younger children sailing the boat 2 up and don't want the boat to become unusable with a teacher and student on board.

With 4 designs currently on the go, assuming Phill is going to unvale a Scalpel (small blade), is it time for us as a group to re-visit a set of class rules for these boats?

But am I right that you advocate an unstayed mast? That must significantly constrain the design of the sail plan, yes?

Remember boards are not just for pointing ability.

When we were originally talking about the f12, the design was boardless and it was something that I agreed with, but having spent the last year teaching kids in optimists I can see that quick tacking and gybing are vital for a kids boat and for that reason I know favour boards. Altough I can see that it does add build time.

With that in mind what about leeboards?

Gareth

Mark,
There are designs already out there both with a normally stayed mast and the ugly things above the deck to hold
the mast up.

Not much point in doing anything unless it makes a difference.
So yes the unstayed mast does restrict the rig that can go on the boat.
The advantage comes in simplicity and speed of rigging along with good asthetics. Nothing on the market today that has all 3.

So far current designs are not making that much of an impression in getting the young ones onto the water.

Now if your looking at a boat for 12-16 yr olds they can rig their own boat so the unstayed rig is less important.

Its when the parents have to rig the kids boats the unstayed rig has the real advantage in getting boats onto the water.

This is where I started with the 12 ft concept and believe it is still the driver for such a design.

Regards,
Phill

Do you remember how the rig was made up. Was the sail just a sleeved sail with the mast put inside the sleeve with no other elements/parts being present. Was the mast very stiff, did it hardly bend when you cranked on the mainsheet. Did the battens pop easily when you tacked. In how much wind were you sailing ?

Wouter

I have two idea's with respect to this.

First I've run the math on a boardless design. Without going into mathematical details I garantee that the boat will steer and tack significantly easier and quicker by going to a shorter hull length. Disproportionate easier.

To give an example a 12 ft boardless cat with a deep V-ed keelline with tack/steer almost twice as easily as a 5 mtr. long boardless cat with a deep V-ed keelline like the Hobie 16's and Prindle 16's. That is a huge difference.

Bascially this results comes from the fact that the points of the hull furtherst away from the fullcrum contributed disproportionally to the "tacking/steering" resistance. This is aggrevated by the fact that fluid resistance is quadractically dependent on the speed through the fluid. Of course the bows on a 12 ft hull travel much faster sideways through the water when steering then the bows of a 16 foot hull. The difference being 35 % in speed and therefor result in 135*135 = 183% in drag force alone. Then of course the leverage of the shorter hull is less as well. And like that things really do add up.

Currently I'm going on the expectation that these effects will make the boardless F12 steer easily enough without the need to have daggerboards.


However when a need is found then the vertical sides of the hull will allow an external pivoting boards to be fitted on the inside (or outside) of the hulls. Just a simple bolt going through the head of the board and through the reinforced wall of the hull. With transporting or hitting something the daggerboard will just rotate to a horizontal position alongside the hull.

However, looking over the specs at this time I'm really not convinced that a daggerboards will add much benefit to the design. The line of think here is that that rig is relatively small, its overall area is disproportionally smaller the wetted surface area of the hulls are. The latter is fixed because of the need to carry the given combined weight. Basically you have all that area almost vertical in the water that also wants to resist sideways movement. Now any movement resisted by the hull will deteriorate the benefit of adding a daggerboard as the daggerboard needs some sideways movement to get at its optimal angle of attack of about 2 to 4 degrees.

So we are faced with a fork in the road here. Either we go for daggerboards and then we want the keelline to be as flat and rounded as possible with all related increases in denting and risk of damage. Or we go for the multichined hull that is very resistant to damage and much more easy to build and go for a boardless design. Combining a multichine hull with a daggerboards will mostly deteriorated the strong points of either to a level that may make either negligliable.

Wouter

I believe we are long past that point.

The unstayed rig have gotten more pro's on its listing since then :

-1- Easy to homebuild for much smaller costs then a conventional mast with a sailtrack
-2- Collapsable and easy storage.
-3- Easy homebuilding of the mainsail, sleeved sails are easier to make and recut then sails with bolt ropes.
-4- Less parts required and therefor cheaper
-5- Ability to completely weathervane the rig, that is a safety issue both on land and on the water





But these are so beautiful when you look at how the forces and stresses are transmitted through the platform. Gone is the requirements for having a dolphinstriker or even carbon beams. Gone are the stringers inside the hull and subdecks to make the bows stand up to the forestay loads. Gone is the reinforced bulkhead in the bow to take the bridle fitting. Because of the trampoline tension counteracting the loading of the push rod against the hull, the local reinforcement of the hull can be much lighter and simpler. When needed the same reinforcement can be used to fit the external daggerboard to. And so on and so on.

I know you feel the push rods are very ugly and you have always said so. It is why we diverged on the project. I looked at it from an engineering point of view and saw how nicely it solved many issues in one go.

Recently I visited the owner of the Semprit Skippy and he told me that he and his daughter actually liked these rods as it gave the crew (child) something to hold on to. It gave them an added sense of security. Not I don't believe everybody feels that way, but it is certainly worth taking into account.

Afterall esthetics only go so far, if it makes alot of engineering sense then one should use it even when it is not very esthetically pleasing.

Wouter

G'day again Wouter I would think that the mast was typical of a windsurfer, it was flexible up top stiffer near the bottom and plugged into a hole in the deck. The sail was sleeved and just slid on, the battens stayed in the sail when it was packed up. The boom was basic like an A. It had a vang and a simple to adjust centreboard held in place by shockcord going around it back to the mast this kept enough tension on the board to hold it in position. The main sheet was only 2 to 1 which was really tiring when I was out but the kids had no problem.
My youngest daughter was 8 then and she took it out accross the lake capsised it righted it, sailed it, battens popped easily, loved it probably 8-10knots. I was out in over 30knots when the gusts were so strong downwind that the main sheet was getting pulled out of my hands even then with no stays the mast held no problem as I said with me at 105kg I was able to plane for quite a long time hiked out but under 20knots it wouldnt be much fun for an adult or under 8knots for a kid with expectations. Not to stuff around with your idea but whats to stop somebody that starts their kids on your boat changing the mast and rigging later.
regards

Heres a picture of my then 3yr old son on my old boat, I know the sails are all wrong etc and its embarassing to post but he's the one who's going to sail the F12 and the first new kids on F12's who see adults on the wire will want to be out there. I was strict with him I didn't let him stear the boat from the wire until he was 4
regards

I think this is an interesting marketing question. Neither Wouter's nor Phill's proposed unstayed rigs would support a trapeze. For Phill's targeted under-12 market, that seems perfectly reasonable. For 12-16 I'm not so sure. Chris's design has a stayed rig, so a trapeze might be a possibility. I wonder what Michael & John think?

I think that I'm with Phill on having a boat that the kids can rig as I know the boys are often frustrated that I don't immediately jump when they are ready to go sailing (we live on the beach, so this is quite often). The other thing is that the boat has to be light enough for them to get it down the beach without my help. As for traps, they have ample experience with that and enjoy it, but I'd guess they'd hands down like the independance of going sailing when they want over having to wait for me (even once).
I don't see that unstayed rigs and traps are mutually exclusive as a trap wire would unload the rig when you need it most, will write an email to RG to see if he'll calculate that for me.
Speaking of RG, he sent me a whole new F12 design today to look at and comment on, is hands down the coolest boat Ive seen in a while and the boys agree, hope he posts it here for you all to see soon.
Aerynt

I've seen it as well and it is pretty stunning, so I do hope he posts it.

Gareth

Phill I tried doing a search on the
Glider but could not find any information...

Best Regards,
Bob

Bob,
You probably won't find anything on the Glider.
Designed to take crew weight up to 70kg.
If you were looking at the older kids or light weight adult market and were going to have a stayed mast it would be hard to go past.
I think I still have the specs somewhere. I'll dig them up and send them to you if you like.

Regards,
Phill