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WetSnail

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Everything posted by WetSnail

  1. The Bierig Camber Spar is half a wishbone boom inserted into a sail and allowed to rotate around its long axis. One application is to make self-taking jibs, as shown in the attached picture. I have no experience with it myself. I did read a discussion in a cruising forum, where reports were positive. Because a self-tacking jib made with a camber spar should not need a traveller, you may be able to choose from a wider range of designs.
  2. Then, if my calculations are correct, compression load when caught aback is 50% higher than when using the same staying angle as Koehler's KD860. Do you have an opinion on whether my mathematical model is adequate? Your expressed concern was with staying angle. I looked at what is relevant to that. Further, as I did point out, I would also need to know the longitudinal stability of a comparable catamaran. I have never seen data on that. Without that longitudinal stability, hull weight is close to worthless. Koehler's undisclosed cat is the KD860: https://ikarus342000.com/KD86
  3. I think legs offer more power than arms, and when suggesting a recumbent position, I was less concerned with maximum power, and more with the difficulty of pedalling while heeling 30 degrees. If an upright frame is mounted transversally, on one tack you would be trying to pedal while going steeply downhill, on a bumpy ride. I doubt that would produce better power output than a recumbent position, and there would be some risk of falling off head first. If the frame is mounted longitudinally, you will have a hard time pedalling while heeled, and that will again cut into power output. Also, a
  4. Perhaps they see the greater heeling angle as a problem, or headroom above the cranks? Perhaps they are not aware of recumbent bicycles. That position should deal with both issues, if the rotation axis is longitudinal and there is a seat on either side.
  5. Doesn't apply. I wanted to know the compression load when caught aback, as that seemed most relevant to the staying base that concerns you. I am interested in quantifying that. Here is my calculation. I assume that I can decompose all vectors in the horizontal and longitudinal plane, then multiply. If I am wrong about that, my calculations are worthless. Jzero's mast is said to be 6 feet to windward. If that is from the centreline of the lee hull, that gives us one of the relevant numbers. I believe the length is 40 feet, headstays attach a little back from each bow, so about 1
  6. I once followed links back to when things blew up between you and Joe. As I remember it, you two started off friendly, but then Joe said about your first Harryproa that carrying that much weight to weather, on a short hull, would generate unmanageable weather helm. You responded with what I read as "You don't know, you haven't sailed the boat", but which Joe seemed to read as "You are too ignorant to understand why this is not so." (If I am wrong, Joe can correct me.) Having been in the situation where someone who had not sailed your boat told you something that conflicted with your experi
  7. So if not being flipped by a wave were my primary design consideration, I should have an ama like Splinter's (https://epoxyworks.com/wp-content/uploads/2015/10/splinter1-e1495550700432.jpg), half submerged at rest, and perhaps rasing the beams a bit more? And if I want the freeboard, but not a big volume, make the ama narrow, especially above the waterline? If you can get to a place with surf in reasonable time, a simple test should give some idea. Make two voluminous lee hulls from a plastic bottle or two each, or whatever else is convenient. Tape on a pair of sticks. Then tape on
  8. That touches on a question that has been bothering me for years, so seeing that there are people in this thread with enough knowledge to answer, perhaps someone is willing. The traditional Pacific proa designs range from having almost equal hulls to using a log as ama that is barely afloat when at rest. Their modern descendants avoid the barely afloat ama, even though it seems to have some advantages. I read an article by John Shuttleworth that tried to quantify how a wave can capsize a multihull, and two important factors were the area and shape of the weather hull on which a breaking
  9. I think Sven is an inventor first, and sailor second. If all he wanted was to sail, he could have stuck with the boat he had 30 years ago. Amfibie Bris (https://www.yrvind.com/videophoto/bris/amfibie-bris/) is, if I remember correctly, the boat that he let fore reach under small sail in a storm, with the bow board down and rudder up, and after six days found himself 50nm to windward. Amfibie Bris was also the inspiration for the Sofiaboat (http://www.sofiaboat.se/nyasofia_eng.html); at least one of these has crossed the Atlantic. My impression is that there are three reasons why Sven'
  10. If the only thing he wanted to do was to go cruising, he could have stuck with the boat he had 20 years ago. But he likes to experiment, and experiments are what you do if you don't know for sure what is going to happen. Seeing that you knew that in advance, well enough to be sarcastic now, you can probably explain what exactly made the boat unsuitable for its planned purpose.
  11. High Northern latitude in summer. Looks about right to me. Even where I live, still south of the polar circle, for a few weeks the sun is just a few degrees below the horizon at midnight and, I suppose thanks to refraction, light level depends more on cloud cover than time of day.
  12. I can see that being true for the vertical loads, but I think the lateral loads do depend on righting moment. Depending on how much lateral loads contribute to the total, righting moment may matter.
  13. How much difference would it make to take the same approach, spirit, and technology into the B-class? With M20 and Tornado offering off the shelf platforms, and the Vampire project working on foils, the barrier to entry should be a lot lower. Though to include Vampire, B-class rules would have to be modified either to allow greater beam or not to count foils, and I think she has greater sail area. And if you want to open up platforms, you could abandon beam limits to allow in trimarans, or limit cumulative hull length to allow triscaphs, like Loisier 3000 (https://www.youtube.com/watch?
  14. What does "wanking" mean in American English? I suspect the meaning differs from the one in British English.
  15. By your own account, that is a consequence of the rudder being to windward of the forward foil. The L-foil would behave exactly the same. Put rudder and forward foil in line, and I see no reason why the straight inclined foil should be any less stable than the L-foil. whereas a foiler using uptip foils can sail all day on a single main foil. Is there any theoretical reason why it should be better than either an inclined foil or a wand-controlled system, or any empirical evidence? I mean, look at TNZ crashing (https://www.youtube.com/watch?v=wpBkJp4cwrI) or these smaller cats (https://ww
  16. Icarus maintained altitude in any given condition 40 years ago. And it is possible to sail on a single inclined foil. You can find pictures of several different boats with simple inclined foils doing just that here: https://sites.google.com/site/f18foiler/ > The only foil system being tested now(that I know about) that might be better but ,perhaps, not practical on a large boat is the Vampire system with a single wand controlled main foil on the lee side canted 20 degrees outboard. And the man developing this system comments on poor altitude control of the bent foils. Further, Bra
  17. Depends on exactly what is meant by servo. I would call the Moths' wands servos, and likewise the Trifoiler's system. No motors required. I don't understand the recent focus on America's Cup style L-foils. These people were forbidden from using flaps on the foils to prevent flying, then when Team New Zealand used the loophole that the forward foils could have their angle adjusted, did people start thinking this was the best way to fly? Perhaps it gives you cleaner foils with less drag, but it doesn't seem to be such a good solution for stability. Foiling multihulls have been pretty
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