• Announcements

    • Zapata

      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  

atg

Members
  • Content count

    424
  • Joined

  • Last visited

About atg

  • Rank
    Anarchist
  1. what is it?

    Most excellent build. The big issue with twin main foils as I see it is induced drag at takeoff. You really want maximum span there. With two foils you get two more tip vortices than needed, and much more drag when you can least afford it. The strut drag is significant, but with two struts the main foil can be so much higher aspect that it outweighs the loss from the struts, and the struts can be much smaller also. I suspect we may see twin strut moths at some point with the Clive system if the fairing drag can be worked out.
  2. New IC sailor

    Sorry about that. That carriage was a bit of a compromise between Gaudi-esque style, reduce/reuse/recycle, and death needles.
  3. The Transat 2016

    If Riou really lost some important sails just after the start, the new foiler must really be a dog to have only finished 30 miles ahead. Those foils look like they have a ton of induced drag. Avg speed was 12 knots, which is not where you want to be trying to lift a keel boat onto foils. I'd say PRB is looking quite strong for the Vendee.
  4. Bieker-53

    Opinions are like noses. The internet is a giant relief valve so people without the 3.5 large can feel like we are important, too. I matter, dammit! Kind of a genius move by Darpa, from a Marxian standpoint. There are so many more boring things to spend that kind of coin on. It takes some balls to put the details here for everyone to carp at. Say thanks and nice boat, or move on.
  5. ...IC kit...'machete'...'

    Yes if you are inclined to join the fun and like to make stuff this is a nice way to dive in. There is no cheaper way to get a reliable, proven product. If you are a genius NA or boatbuilder then great, but most folks aren't. This kit is for the rest of us.
  6. Team Vestas grounded

    Seems to me if they had turned and tried to go upwind they would have grounded out the keel and boards and ended up sinking in deeper water. In that sense it was better to run full tilt up on the reef after the first bang.
  7. Best "Not a Truck" tow vehicle

    Yeah, you want the tow vehicle to weigh almost as much as what it is towing. No way a VW or anything like it would be safe. Dude a VW touareg TDI is over 5,000 lb. It tows 6,500lb of RIB and trailer without a problem. You need trailer brakes for any serious weight anyway.
  8. Flying Cherubs

    Ah - yes I went quite oversized on the control line and blocks also, to reduce stretch. I think I am running 1/8" spectra at the moment and the blocks are all sized at least 8x line diameter to reduce any friction losses. I recall being startled by the center of lift calculation at high speeds as well. Way behind the foil. It gives me a bit more responsiveness at high speeds, which is fine because my wand loading is a bit light at low speeds. We don't get much breeze in winter but I will try to get out and get a bit of video. Beers, Karl
  9. Flying Cherubs

    Phil and Clive - Thinking about the tailplane, is it actually true that Cl remains constant? I don't think so. As you speed up, yes, Cl needs to go down to keep the foil in the water. But this is precisely what a tailplane does - it is generating more lift with speed, and in Clive's system would therefore reduce the AOA of the mainfoil with increasing speed. This could, if the tailplane is sized correctly and at the proper angle, keep total lift constant - not coefficient of lift - with increasing speed. The tailplane is small in both area and span, and as speed increases it becomes more powerful and tilts the foil more. So adjustment for speed through the water would be automatic. Adjustment for the ride height would not. The wand could drive the tailplane to adjust for ride height, if someone were clever enough to make this work. Personally I think I would do this with rotating shafts and bevel gears. It sounds like a bit of a nightmare, but doable. What say you? Karl
  10. DC Designs

    Bummer dudes. Glad you are OK. It puts the old "journey not the destination" idea of boatbuilding to the test. I always figured I would send mine forward off the roof rack in a hard stop or accident, but somehow never did. And getting rear ended always seemed like a good possibility. Maybe LED bike flashers on the tack fitting? Sorry you missed the regatta. Nothing like long island sound in October. Who are the builders? Oliver? K
  11. Flying Cherubs

    Oh I just saw the photos you posted Clive. For some reason they would not appear before. Interesting that with totally different systems we both had problems with too much wand loading at takeoff! With an extra set of hands you can do a lot about that though. I thought of having a bicycle brake handle on the tiller to pull and get a bit more daggerboard rake for takeoff, then release once flying. Hydraulic or cable. You could do the same to somehow push harder on the rod at takeoff. It has to be convenient wherever you are in the boat while taking off; moving around to adjust it is slow out of tacks and the competition will be long gone if it takes any time to sort out at all. Seems like the joint between uprights and the foil could actually be rather fair when optimized. Decavitator used two uprights on the main foil for the reasons you describe, so you are in good company there I think. All this has me motivated to try to get out more often. My wife works weekends so it isn't always an option, but that should change for the better shortly. Good Sailing, Karl
  12. Flying Cherubs

    Yes many smart people have looked at the problem. And some dumber ones like me. On the flapped vs flapless front Phil has made a good articulation of the pros and cons. Nonetheless if one actually runs the numbers, the flap does not come out ahead of a flapless foil. Flapless allows pushing the structural limits harder, getting more span for a given thickness, and also playing with geometry e.g. anhedral. So the drag you might pick up at takeoff due to a thin nosed 2D foil section is offset, because the foil area can be smaller and the span larger, thereby cutting induced drag considerably. So takeoff drag can remain the same, while high speed drag goes down because the foil area is smaller. Flapless cleans up the T. This comes at the expense of wand load; the paddle does generate a fair bit of resistance unless the entire system is optimized to eliminate both wand loads and friction loads. I think my current system is pretty close in performance actually to a flapped foil. If there is ever another local regatta I will test the theory. It could be a bit lighter, but for a prototype it is OK. After that I should really fire up the router and make an optimized mainfoil mold, as my current foil is bigger than it has to be. I think Clive's boat demonstrates that the world of ideas is far from exhausted when it comes to wand-driven foiling solutions. They may not be easy to dream up, but neither was the flap system. In fact the more I did with my stuff the more respect I had for John Ilett and company. Lots of people have tweaked control systems on the water, but not many have developed entirely new ones. So hat's off Clive. Keep us posted. I agree it would be much more fun with a kid in the boat to share the experience, but right now we are working on swimming lessons, so it is a bit premature! Perhaps my next tilting foil will go into a Cherub hull. K
  13. Flying Cherubs

    On the pivoting DB it is all about keeping the loads down. I am curious about how the tailplane is trimmed; that is a cool idea. Ideally the wand would trim the tailplane and not the foil itself. That would keep loads down. You will want to take a hard look at friction and put bearings everywhere. I used an old magic box with an alu tang to mount the turning block aft of the head of the foil. So I could easily adjust the linkage length with that, even loaded. I did however manage to rip it right off the deck with the deck paint and plexus though, so you may wish to sand down to the carbon and rough the surface of the aluminum up a bit before gluing one on. Nothing like trying to sail dead down through chop to the channel entrance with a daggerboard flopping around willy nilly trying to pitchpole you because the linkage went away. Might be good to have an emergency lock on it somewhere in fact. Fundamentally the wand is fighting a sort of losing battle when the pivot is at the hull exit. I ran a counterspring for a long time on the moth made from several strands of mandrel-dipped rubber UAV launcher tubing hose clamped to some nylon plugs. Then I added a motorcycle steering damper, which survived salt water immersion remarkably well for several years. Let me know if you need one; I'll give you a good price on it. Looks pretty much new actually. One problem is that the spring rate needs to change with the fore/aft position of the crew in the boat. As you vary the loading between the rudder and mainfoil, the moment about the pivot changes. Another problem is that during takeoff, with a spring, the wand load is high because the foil is not generating lift, so the spring needs to be manually engaged as you take off, which is pretty much impossible on a Moth. If you have no spring then great, but your operating load on the wand is going to be higher, leading to more wand drag. Maybe the crew can trim the spring. Two people is a luxury. I could go upwind just fine but the corners in marginal air were very tough due to takeoff, and downwind the settings were hard to dial in. Basically, it was just too much manual adjustment all the time to be competitive around a course for a singlehander. The new system is much better, though it is hard to get the wife to sign up for RIB driving and childcare duties together. Maybe a stainless T top will help...how hard is it to bend 1.25" stainless stanchion stock? K K Hi Rob, I suspect that mechanical linkages are superior, however the simplicity of the tensioned line is very attractive. I hope to minimise the disadvantages by gearing it so that there is lots of movement and low tension in the line. Over the range of movement of the wand, the line moves 70mm. I think that this is about 5x as much as the movement in a Moth linkage. The effect of any stretch is correspondingly reduced. I learnt to drive in a car with cable steering it would never be used now however the cable shift on my road bike is pretty crisp. The return force is generated by having the pivot on the foil forward of the centre of lift. The idea is that the tailplane can be tuned to control the position of the centre of lift and how it changes with speed. During the little bit of flying we have done so far I have been trying to judge the reaction of the wand tip on the water and from that had estimated that we are currently running with about 20kg of load on the centreboard push rod. I had felt that this was perhaps a bit high. Interesting that you numbers are even higher. I am very aware that there is now thousands of man years of Moth flying experience out there and that we have been doing it for 2 weeks, we have a lot to learn. The manual take off was a useful experiment to try and gauge the load on the push rod. I don't see it being routine. Hopefully we can find the AoA for the foil that gives the sweetest take off. I would like controls that independently adjust the take off AoA, the ride height and the gearing. The forecast is looking good for tomorrow with luck we will get some more airtime before it gets too cold for us. Clive
  14. Flying Cherubs

    Cool idea Clive. I would like to see what you have going on up on deck, i.e. compensation for the shifting fore/aft center of lift. Perhaps the tailplane handles things in a way I do not appreciate. Regards, Karl
  15. Artemis?

    I have to both agree with you, yet disagree at the same time! Yes, the sailors are informed, they don't have to be there and they are making informed choices. However, their choices are based on what they see as possibilities are of being killed/injured. That whole equation has just changed and the sailors will now reassess their position based on this information. It wouldn't surprise me if we see some sailors leave AC teams. I have participated in an extreme sport, skiing, where the risks were well known. I have done a number of "first descents" and have skied things on which people have been killed, but although II knew that people died on those mountains (and others), I was able to rationalise what I did because nobody I personally knew was killed. All changed when in the space of 18 months, 3 friends, including one whom I rated as the best extreme skier ever and who was incredibly safety conscious, were killed. Although I still skied stuff that most people would consider dangerous and extreme, I stopped skiing stuff that I considered to be "if you fall you die". The idea that in any sport, the participants know the risks and make choices, therefore it's Ok, is simply wrong. F1 got to understand that 20 years ago, which is why what used to be a very dangerous sport (1 in 20 participants died every year at one point) is now safe. I am not arguing for the cancelling of the AC, or for sailors top leave teams. All I am trying to do is to frame the arguments in the correct light. There is a big difference in the discussion between "these boats are dangerous and people might die and/or get hurt" to one that says "people get killed sailing these boats". Stop equivocating Simon, what exactly are you saying? Yes people demonstrably get killed sailing these boats, people demonstrably get killed sailing all manner of boats around the year around the globe. My point was exceptionally simple EVERY TIME you go on the water you PERSONALLY take responsibility for your own life, full stop. If some one does something egrigiously wrong to cause injury (Drunk driving sheriff mows down innocent sailors in high powered motor boat comes to mind), then sure it's a slightly different matter, but this was very straight forward regardless of how tragic, sailor goes into rough water to sail high power high performance one off prototype boat in brisk conditions, things appear to have come unglued either figuratively or literally, bad outcome ensues. I have sailed high powered boats in rough conditions too and nearly killed myself, complete with literally waking up 4 feet below the water after having suffered a concussion, I was lucky enough to have the time to sort my shit out, get untangled from a hell of a mess and swim my ass to the surface. The risk is pretty fucking real to me, there but for the grace of God I actually woke up and sorted my shit out and did not pass off my mortal coil at the ripe old age of 17. Yes on some level many might argue it is insane that I would continue without calling for helmets and PFD's and support boats and all manner of nanny state incursions into our fair sport. Rather, I simply looked at it and said after returning from the hospital, "fuck, that was close, beware of that in the future" Indeed that one incident informed many decisions on many subsequent sailing days in my life and no doubt saved my bacon later on down the line. I have participated in an extreme sport too, riding a bicycle on my city's streets, I have stood over the grave of one of my best friends after he was mowed down by a drunk driver while on his bike on a City street. I personally chose to stop riding on City streets on my bike because I am surrounded by asshats, as you chose to stop skiing in high risk environments. My personal risk assesment of AC 72's is, that I would trust my own team, and the racers I race against and the available support teams, to go sailing on the boat in SF bay, part of that is knowing what my skill set is, on any given day, perhaps I might have to give it a pass in light of having children, in light of what I thought about the quality of my team mates, the build of the boat, and so on. I have stepped away from things before, I will do it again, I embrace risk, but I manage it too, it's the fundamental expectation of any sailor. So I maintain you equivocate by saying, "What they see as possibilities". If you think for a minute they don't or haven't previously seen the possibility of being killed or seriously injured while doing that job, you are fucking delusional. You are suggesting they are so arrogant, or so stupid, or so blinded by money, that they are unable to see that they could get killed on that patch of water in what are arguably the most high performance course racing boats of all time? Yes to be sure someone getting killed drives home the point, but form day one it was a possibility. As much as it is in a Volvo Ocean race or a Fastnet or Vendee Globe. We are men, we go down to the sea, even if only to have a gentlemenly contest of skill, but we do it with the full knowledge of all those before us that we take our lives into our hands when we do, as we take into our hands the lives of our brothers and trust our lives into their hands. This is what separates us from playing fucking bridge at a table, this is the essence of the commeraderie that sailors enjoy over other sports, our lives are in each others hands and this is serious shit and the stakes are as real as they get. It's special because it really is fucking dangerous, it's not a game, it's life in technicolor and 3D. when you forget that that, then you are in danger. To be clear I am not suggesting that sailors should be expected to take stupid risks, nor am I suggesting that changes should not be made to make things safer for the sailor if it is clear what can be done to do so, but lets be clear, when a boat shits the bed in the middle of the bay and a yard sale ensues, it's really difficult to suggest or speculate with any manner of precision what the possible outcomes are. In F1 they could figure out that crash boxes that dissipated kinetic energy saved lives and so they changed the rules to ensure you could dissipate the energy of a crash to save the life of a driver. How do you determine how a boat might fold up after a cascading failure and in turn where exactly the crew might be during or after said event? Some here cry about the inevitablity of a pitch pole, but by current accounts this accident was the result of a structural failure of the front beam which ended in a boat taco. Lowering the rig would not have changed for one second the performance imperative of saving weight and cutting it close on the main beam specifications. So OK, you can allow for some more carbon on main structural elements, but you all know you will end up chasing it all over the boat as teams try to eek out a performance gain here or there. I would submit that its a fair bit easier to design a safe F1 than it is to design any boat as "safe", if only because in F1 you have one driver doing a very narrow set of activities in a fully enclosed cockpit, with a very predictable set of outcomes in crashes, repeated many many times. Do you want all the crew strapped into pods on either side of the boat? Well OK, great, you can build crash cages around them and make it safer in some regards, but more dangerous in others. Bridge is looking better and better. It is so early in all this that nobody even knows how these boats are most likely to kill people. Whoever quit Oracle months ago due to safety concerns is starting to look pretty smart.