Here is the latest-and-greatest attempt at the profile view of the Freestyle 14 catamaran. I've been to a few regattas lately and sailed on a couple spinnaker boats and have been taking notes on their hull designs. [note: this picture is not exactly level]



Please make any comments and critiques in the Formula 14 forum in the post "Wanna help design the next F14?"

I think the daggerboard looks like it is to far to the rear. This would cause an unbalanced helm. You would have a lot of lee helm.

Your rudder looks a little short for that much rocker. Either put less rocker in the hull or make a longer rudder. The minute the boat gets bow down in the slightest the rudder will be almost out of the water.

Just an opinion,
Mike Hill
Tiger #1520

put your design into some kind of digital format. IE, a crayon sketch isn't much to base an opinion on. Its quite imperfect. (although quite colorful!)

I'm doing something similar right now designing a hull shape, let me know if you want some pointers on turning out a rough digital sketch.

Regarding the daggerboard placement: This sail is going to have a rather wide square-top, and the mast will be raked back more than in the picture (mast drawn vertically in the picture for simplicity). If someone knows a better method of guesstimating the CoE of the sail, and thus the proper daggerboard placement, I'd really appreciate the help.

Regarding the rudders: I have Dotan's Sampson 25 rudder system that will go on this boat (or a H14 rudder system). The rudders in the picture are likely not drawn to scale.

Regarding the tools I'm using: I don't know how to use CAD, but colored pencils and rulers I can handle!

Daggerboard placement will depend on what you want to achieve...if you want to give the 'shared lift' concept a shot, put them way forward of the CE. If you want to go with a more traditional line of thought, put them on or slightly behind the CE for more balance with the head sail up.

For the purpose of this generic discussion, you can approximate the Center of Lift from the sails at approximately 1/3 back from the leading edge. You should consider where that center of lift goes with the headsail working too. However, it's hard to do an accurate calculation without going into drastic detail about lift from each sail and the various lift angles in 3D. I suggest you take a design that you like (Taipan, Nacra 5.2, etc.) and perform this generic calculation with sail area and assuming lift at 1/3 back from the leading edge to determine the position of the daggerboards relative to the sail drive. Then use the parameters learned with the parameters of your boat to determine a relative daggerboard placement ... that would help eliminate some of the wild details you would have to accomodate.

Daggerboard placement is also very dependent on the sideways resistance of the hull as a whole. For example the Taipan design has the board further back than a design with the much more rounded bow section. With the Taipan the hull itself forward of the mainbeam tends to act as a daggerboard itself making it necessray to place the daggerboards further back to compensate. So it dependent on the behaviour of your hulls too.

It is never simple.

Wouter

Your design looks alot like my Supercat 15!! If you get the hull design right you won't have to worry about daggerboard placement because you won't need them. Good luck!
Heinz Smith
Fleet 42
Supercat 15 and 17

10' beam you say? How will you disassemble for trailer width?

What about foils?

10' beam? Nah, 8' or at most 8'6" (US max legal width). I believe foils are outlawed in the F14 class as well. It's supposed to be a class that keeps things pretty simple and can cater to women and children as well as the rest of us.

Regarding the Super Cat 15 similarity: the cross-sections of this F14 will be very different from the SC15. The F14 will have high-bouyancy bows (though they will be rounded off on top like the SC15) which will make it difficult to "drive the bow down" to help with pointing ability.

I'm working on a new design with reduced aft rocker now... cutting it down from 12" to 6".

A lot of "little" changes in Draft #5.

1)The section of maximum width was moved from being centered under the mast to being entirely ahead of the mast. The reason being to give a better foil shape to the entire hull, and to gain more leverage against the rig.

2)The daggerboard has been moved forwards 6". This puts it around 1/3 aft of the mainsail luff.

3)The mast rake has been drawn in. I set it so the sidestays go almost vertically from the chainplates to the mast hound (which is set 2/3 up the mast)

4)The deck drops 6" after the rear beam. This allows the rudders to be mounted lower and allows the aft rocker to be lessened to 6" from the previous 12".

5) The fore rocker is still only 3", but it now ends 5' from the bows instead of 6'



I might move the fore rocker back to the 6' mark, I'm not sure I like it as much in this draft as in the previous one.

I drew the boat on an oversized grid to help you all get a feel for the dimensions, and actually managed to get a pretty level picture of it this time.

Again, I'd prefer if you respond to the post in the F14 forum, just to keep the information all in one post for other readers.