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Everything posted by WetSnail

  1. A very convenient rule for a country that is surrounded by countries considered safe. But is it even UK law? Someone stood up in the House of Lords and pointed out that even the Home Office, so dedicated to sending Johnny Foreigner back to where he came from (Russian Oligarchs and money launderers excepted) accepts over 70% of asylum applications from people crossing the channel (https://twitter.com/OliDugmore/status/1464536696138178569). If they were, by definition, economic migrants, that would not be happening. Also, as I understand it, the UK, like the USA, does not accept asylum a
  2. Exactly. Designed by a gifted five year old who wants to circumnavigate Fairyland, and made real by a Womble engineer.
  3. You may be able to adjust for your needs. I defined the lower point on the hull, and two on the beam. I drew a circle around the lower point to define where the outer point on the beam, and the strut between them, would end up after folding. Because you wanted waterstays, I thought I could attach the strut to a dolphin striker on a waterstay, which gave me a bit more freedom in where the outer and lower strut could go, and how long it had to be. I rotated and shifted until the whole thing was reasonably narrow. Then I looked at the two points on the beam, drew the perpendicular bisector b
  4. Very nice. What is the reason for the foot of the yard only going to the forward crossbeam instead of the bow? Is it that you don't need to shift the sail that far forward because you have a big rudder, that you want to load up the rudder to provide lateral resistance, that it is safer for the crew, or some combination of those, or something else entirely?
  5. Would this do? Blue is unfolded, orange is folded, the fat lines are the struts of the folding system (and the dolphin striker on the waterstay). I haven't checked what that would do to shrouds. You'd have to adjust the geometry to take care of that once you know how high up the shrouds attach.
  6. You could make a boat trolley with large wheels, perhaps from a fat bike. Given the size of rocks on your beach, I am not sure even that would work, but much of the coast where I live looks similar, and the solution I have seen is light rail. People lay rails into the water and run a boat trolley on those, possibly with a winch installed in a boat house.
  7. There is a wire going from the end of the windward outrigger into the water. The boat may be stabilised by paravane. I found the listing and there are no pictures of the paravanes. To answer Bull City's question, paravanes are foils on strings, like these: https://www.youtube.com/watch?v=qF4A2Wf2alM https://www.youtube.com/watch?v=sJ9qwAQ_ofQ But the wire seems to pull nearly straight down, so it may be more like what you see here, about 10 minutes in: https://www.youtube.com/watch?v=EYp8eVApLrg
  8. If you cut plywood into strips, stacked them on top of each other and glued, then profiled that, you would have half the wood fibres going parallel to span as before, but the other half would not be parallel to the chord, but perpendicular. Would that turn plywood into a good shear web suitable for covering with laminate?
  9. If you mean let them bend, then let's say you build them out of a low modulus material, meaning they bend enough in light wind without breaking in strong wind. You still have the problem that the more wind there is, the more they bend. That is because each batten is sheeted. It must act as a boom for the panels immediately above and below. That is mostly a feature, because you don't need to control twist by pulling hard on the leech, and that reduces loads on sail, yard, boom, and mast, and that is a big difference to the lug rig. But if you make the battens bendy enough to get a good sha
  10. Don't know. But narrow inflatable kayaks are pretty recent designs, so he most likely used one with a fat tube either side of the paddler, and those are quite beamy and stable. I forgot to mention https://woodenwidget.com/ Their Fliptail folding dinghy and Stasha nesting dinghy are both quite light, being skin on frame boats. So those might also be suitable alternatives if light weight is important to 2airishuman. Of course, if the Chameleon is a favourite design, alternatives may be irrelevant.
  11. Jerome Fitzgerald, in one of his books, swore that the best dinghy is an inflatable kayak. And just yesterday, I watched an introduction into what is available: https://www.youtube.com/watch?v=5U8u_rkNTSY I think they are all lighter than what you think of building, and they pack down smaller.
  12. Hitting the bottom while trying not to broach when sailing in through surf. The more the load is sideways, the more friction there is between rudder blade and rudder head, and the less force there is to trigger the kick up. The rudders are designed for beach cats, so this is very much an expected load case. The moment you ground, the load is no longer limited by how much force the water can exert on the foil.
  13. Bought one recently, but haven't used it yet. Looks good, though. If you have a rudder and head, and just want the rudder to kick up, that cam cleat is a perfectly adequate and much cheaper solution. But I can't build a rudder that stands up to that kind of load: https://www.youtube.com/watch?v=hDeI-SIM7No&feature=emb_rel_end
  14. Thanks for the reply. I can understand issues with twist, assuming beam spacing is limited by needing to sheet to a traveller attached to a beam. What do you mean by sailing balance? The relationship between centres of effort and lateral resistance? I assumed the relationship between mast, front beam and foils would remain the same, no matter where you placed the three, and that would take care of balance. Have I overlooked something? If one designed a boat under the assumption that it always foiled above some threshold speed, would there be any drawback to placing front beam and mas
  15. That link shows a plank across the cockpit with a hole that is the mast partner for the mizzen. In the video, at 0:58, that plank is absent. What is holding up the mizzen? The perhaps 20cm bury you can get under the cockpit sole?
  16. One difference that can be important is time. I was flipped backwards sailing out through surf, had a righting line rigged up that I could have just grabbed from under the hull, but was stuck on first flipping it over the hull. I neglected that the water was only about three meters deep, and the mast was stuck on the bottom. Between the extra load from me leaning on the beam so I could get the line over and the extra time of waves bouncing the mast off the bottom, it broke.
  17. It's a daily calibration of the sensor, says one of the scientists using the data: https://www.youtube.com/watch?v=sDHXSGeov3I
  18. Question from someone who has never foiled: I noticed that in Moths, the distance between the main foil and the elevator on the rudder is a large proportion of boat length, and the rig is fairly far forward, the opposite to A-cats on both counts. Now, in displacement mode, placing the rig farther back reduces nosediving in a cat, but is that still necessary once you foil? Is there something to be gained from separating main foil and rudder by the largest distance that the platform allows to give the foils better control over pitch by increasing the lever arm, and place the rig accordingly?
  19. I started with the rule of thumb that steel should not be loaded to more then 1/5 of its yield strength if you want it to last indefinitely. I looked up some fatigue curves (I don't remember how to upload pictures, and don't see that option in the menu), and found that depends more on the type of steel than I had realised. I cross-checked a book on anchoring, which gives the safe working load of BBB chain as 1/4 of breaking load, and for high tensile chain 1/3 of breaking load. Aluminium doesn't have a fatigue limit. No matter how low the load, aluminium will fatigue, and eventually b
  20. Sorry, I am somewhat interested, but not that interested. My description was of a vector diagram, so it should be possible to translate it into a drawing if it interests you enough. If not, we can just drop it. They are not the ones who say there is a problem, and I am not telling them they have a problem. My reasoning is that the load case is similar, and if there were a fundamental problem, it should show up in boats that routinely experience the load case that worries you, and there are a lot more catamarans than proas, each catamaran spending a lot more time sailing downw
  21. 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.
  22. 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
  23. 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
  24. 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.
  25. 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
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