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About MountainCat

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    A-cats, Windsurfing, Skiing and Trail Running.
  1. So Mt Cat.

    What's your price range for an IC.


  2. MountainCat

    DC Designs

    Thank you Dan and the rest of you all for your thoughtful replies on my proposal for a Planing Optimized IC (PO-IC). I don't expect to convince anyone here that it's a better design. I am hoping my boat will be positive proof. I merely want to vet the idea to confirm it's not totally wacky and a waste of time. It seems that at least a few of you think the PO-IC might be fast in specific conditions. Maybe 14 - 20 knots and flat water? In high winds, I think the biggest risk is too much pounding in waves, but I won't know for sure until I try it. The early posts remark how noisy Steve Clark's Josie design was in the waves. For light winds I will make a big effort to optimize the shape for minimum wetted surface and wave making when heeled at 30 degrees. When heeled at 30 degrees, I cannot avoid the hull shape from being quite asymmetric. I am not sure how to think about that. One advantage of the PO-IC is that it will be considerably more stable than other designs with the wide flat sections aft. Not much help though, if it's always too slow. I admit that the semi-displacement narrow designs including and similar to the Chris Maas designs may be very close to optimum for the now existing IC rule; but I am willing to spend some time and effort to see if my ideas have any merit. Already your posts and feedback have me considering several improvements to further optimize the PO-IC design. I think it may be especially important to avoid any bottom curve in the stern flat sections to keep the downward suction force to a minimum. (No sucky time.) I am thinking that I will concentrate all of the bottom curve in the forward 40% of the boat where the cross-sections are curved. In my board sailing, I have compared side by side rockered tail sailboards to straight tail sailboards. The difference is a night and day; the straight tails are very noticeably more low drag and faster while the rockered tail boards are slow to plane and draggy but very easy to turn. I don't think my PO-IC will be "horrifically" slow in light winds if it is properly designed and sailed heeled up on its chine. I think it will be just a small bit slower than other IC's. I am pretty confident my PO-IC will be quite a bit faster than either the foiling moth or the formula boards in 3 to 7 knots due to its longer water line length. FWIW both of these classes with worse light air performance (assumed) than my PO-IC have chosen to sacrifice their light air performance and concentrate exclusively on medium and heavy wind performance. If I am not mistaken, most remarkably, the foiling moths were first dominant in regattas with mixed boat styles and variable wind speeds. Maybe someone with more experience can comment? I don't consider the build risky. If the PO-IC doesn't work satisfactorily, I will just cut off the bottom stern half and fabricate a new one with some curve in the bottom cross-sections. The alternative would be to add sail area and triple the plank length and try to set speed records! ;-) I will try to post my design in the coming weeks. As of now, the design is pretty rough and only in 2D. This is a great discussion by everyone here. I am learning a lot about hull design. Thank you all. M-Cat
  3. MountainCat

    DC Designs

    I am not convinced that an IC hull optimized for early planning would not be fast in most conditions. Yellow Pages/Macquarie Innovation and the Vestas Sailrocket both use planing hull shapes in their hull pods to achieve speeds over 47 knots; so the high speed potential of planing hulls is certainly there. Formula sailboards are similar in size, weight, sail area and typical expected sailing conditions to new rules ICs. Comparing the sail to weight ratio of a Formula Experience sailboard to a new rules IC with a 75kg helm we get: FE Big Rig: 11.0 m2/ 75 + 15 kg = 0.122 m2/kg FE Small Rig: 7.8 m2/ 75 + 15 kg = 0.087 m2/kg New Rules IC: 10.0 m2/ 75 + 50 kg = 0.080 m2/kg So the IC appears to be in a similar power to weight range at least in high winds when the FE uses the small rig. Another way to look at this data is to observe that the IC is underpowered in light winds and could use a larger light wind sail plan! Of course the comparison above is apples to oranges. The Formula board is likely more efficient than an IC in the following number of ways: Canted rig Sleeved mast Bottom of sail closed off with an effective end plate Single foil with size and shape optimized for wind speed The majority of weight is isolated from hull wave shock by the sailors legs My questions are as follows: Are these Formula board advantages so great that their optimized hull shape has no application to a new rules IC design? Are there no hull shape ideas that can adopted from the optimized Formula board design to IC's? The fastest Formula boards have settled on an optimized design with a width of 1000 mm, a dead flat tail section out to hard chines, little to no tail rocker and sometimes with a cutaway step within 300 mm of the tail. IC's have one advantage over Formula boards in that they have no concern for rocker and rail shapes that facilitate sailor initiated turns by leaning. Formula board bottom shape shown above. Formula boards seem to have a very narrow semi-planing wind range. They go from displacement mode at about 6 knots wind speed to what seems to be a fully planing mode at about 9 knots wind speed. The velocity change through the transition is rather amazing as the board speed can go from about 4k up to as high as 16k with a wind increase from 6k to 9k. The speed transition to "planing speeds" is often assisted by the sailor pumping the sail. The large change in board speed over a relatively small change in wind speed seems to me to be evidence that the board is making a clear "break from one regime to another." Has any one tried building an IC with a Formula sailboard type stern? That is: dead flat cross-sections out to the hard chine and a straight keel at the stern (no rocker). Of course such a design would have a much greater wetted surface and would be slow in low winds just as Formula boards are. Low wind speeds <7k might be accommodated in such an IC design by heeling the IC 30 degrees to leeward in light winds to reduce wetted surface in a similar fashion to how inland scows are sailed. I don't see any reason why an IC optimized for early planing can't fully plane in 9k of wind with the right (bigger) light air rig. My IC designs to date for my upcoming build all feature dead flat cross-sections out to hard chines at the stern, stern widths between 900 and 1000 mm and no rocker or keel curvature in the aft half. What do you think are the chances that such a design might be fast? M-Cat
  4. MountainCat

    DC Designs

    I found this thread by searching on "planing hull shape sailing anarchy," I was hoping to find information for use in my planned design and build of an A-class cat. As I read through the posts from the beginning my thoughts evolved as follows: 1. I might find something in this thread useful to my A-class cat design. 2. IC's are very odd boats. 3. I am disappointed not to find more discussion about planing hulls. 4. I am amazed by how much the photos of pointy DC's resemble both skeeter ice boats and miniature speed record proas based on the full sized Crossbow I and Slingshot. 5. These DC's are an interesting class. 6. These DC sailors are an amazingly helpful and friendly bunch. (unusual on SA) 7. DC's are amazingly fast for their size and sail area. 8. DC's are much simpler to build than A-class cats. 9. I might build a DC as practice for my upcoming A-class build. 10. This thread has lots of great technical information. 11. I start to design a DC. 12. I print my design and build a paper model at 1/16th scale. 13. I design 2 more DC's and build 2 more paper models. 14. I am definitely going to build a DC. 15. I might try to charter an IC to race this summer in at least one regatta. 16. I'm spending way too much time reading DC posts and researching IC's. 17. DC's are easier to store than A-class cats. 18. DC's are easier to transport than A-class cats. 19. DC's are cheaper to build than A-class cats. 20. I've become addicted to reading DC posts. 21. I don't think I'll build an A-class cat. By now you can probably tell that I've had way too much IC Kool-Aid. By the way, thank you all for your great posts! Oh yes, back to reality. Where can I find the US IC regatta schedule for 2012 and how can I go about chartering a boat for one of them? Just one more IC nut case, Teejay