Joakim

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16 Whiner

About Joakim

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  1. Joakim

    H5000 Leeway coefficient?

    Having a K factor matrix doesn't really solve the fundamental problem of the model. You still need to pick K with a specific heel angle and you may have very different heel angle in light winds depending on crew position. It would be much better to have a matrix for K*heel for light winds and ignore the real heel. Or even better have a VPP running in the instrument and calculate leeway with the all the models in the VPP.
  2. Joakim

    H5000 Leeway coefficient?

    No, it's not. It's a simple model, that assumes lateral force to be a linear function of heel. Which is accurate as long as there is no crew and the vertical center of effort of the rig is at constant location. This model comes from basic wing theory and stability theory. Lift generated by the keel is increases linearly with leeway and in square of water speed. Heel increases linearly with lateral force. With crew on the windward reel you get more lateral force, especially at low or zero heel, and at higher winds you need to lower the vertical center of effort and get higher lateral force. Expedition shows how well the model agrees with 44.7 polars. But all the accuracy is lost, if you choose to sail the boat with some other heel angle at low wind speeds when you can easily choose the heel angle by changing crew position. E.g. at 6 knots you can easily choose to sail at from over 10 degrees to zero or even windward heel. The model would then give anything from over 4 degrees to zero or even negative leeway (maybe negative is not allowed?) while in real life heel would have almost no effect on leeway at that situation. Or if it has any effect, it is more likely to be reversed (less leeway with increased heel due to rudder loading). E.g. a DIV II windsurfer was sailed with a lot of heel (30 deg?) in light winds in order to reduce leeway, but obviously the rig could still be upright. A more accurate model would ignore heel at low wind speeds until the boat is loaded up. Once loaded up the model should have on offset for heel to count for the crew weight (how much a hiking crew can heel the boat without sails). When the boat becomes over powered, the model should be corrected for lowered center of effort.
  3. Joakim

    H5000 Leeway coefficient?

    What about zero heel or slightly negative heel at 4-8 knots + crew?
  4. Joakim

    Size 30 winch.

    I don't think headsail size is a sufficient information to select a winch. E.g. my boat has a 31 m2 jib and a size 40 winch. No one has said it is easy and many have failed to get the jib tight enough. Needs a lot of force already at 10 knots. It's a modern high aspect ratio jib (14.3 m luff and 4.2 m LP) with some roach and inhaulers. I don't have a genua, but a 45 m2 one would fit the boat. I'm sure it would be much easier on the winch despite much larger size. My earlier boat had a similar, but much smaller jib. 17 m2 and size 30 winch with 6 mm sheet was a real pleasure to use. When I bought the boat I thought the sheets are way too thin, but they were just perfect. Also the sail plan and the stability of the boat has a huge effect on how much the boat can load the headsail.
  5. Joakim

    Bavaria in administration

    Interesting, that you put Oyester in the top despite Polina Star loosing keel + half of the hull resulting in a quick sinking. Only by very good luck there were no casualties. Had it happened earlier when the boat was far a way from the cost the whole crew would have died. Also interesting that you put Moody in the middle, but Hanse and Dehler in the bottom. They all are Hanse brands. Dehler used to be quite good. Before Hanse bought it I would say Dehler was higher quality than X-Yachts. Hanse clearly made Dehler simpler and cheaper to built, but they are probably still good boats and cheaper to buy as well. What about J-boats? Several keel losses (e.g. two J/80) and e.g. several J/111 lost rudder with one boat sinking and all without hitting an object. Hallberg-Rassy probably still makes their hulls partly using spray layup as they have done for a very long time. One quite new HR37 was doomed to be unseaworthy by a marine surveyor due to delamination. It was also found to be out of specs, since spray layup and orthophthalic resin was used unlike what the specifications say. A friend of mine bought a Najad with epoxy hull, but still with polyester gelcoat. Not a good combination and he was able to cancel the deal. Is Salona any worse than X?
  6. Joakim

    Bavaria in administration

    Bavaria has been on the market since 1978, so it also has built a lot of boats that are now old and affordable. Do you have any facts that would make Bavaria any worse than any other production boat at the same price range? Or do you think that we were better off with all the production boats out of the market?
  7. Joakim

    Bavaria in administration

    That's a though question. Is that the only casualty caused by Bavaria? How many casualties have there been on other brand boats? How many boats have they produced. What is the casualty rate per boat built? If you look at those numbers, surely the one off racing boats have the highest casualty rate per boat built. The ISAF list of keel failures is no longer public, but there were dozens of casualties and only one related to Bavaria. Even this year several have died due to keel failures. Do you think that Bavaria is less safe than the average production sailboat? What about average one off boat?
  8. Joakim

    Wind transducers - tall vs short

    Define analog signal. The Silva/Nexus/Garmin output is PWM as you describe. It can be read as an analogue signal (e.g. with a multimeter or a ADC converter) or as digital (measuring the time periods of "one" and "zero"). The newest versions have NEXUS bus output, which is fully digital, but the sensor inside is just the same it has been since 90's. Probably all wind transducers with propeller or cups use pulses for speed. It is just the AWA that can be several different outputs. E.g. Vaisala industrial transducers use purely digital Gray code to define the angle. The one I have at home (from 70's, still works!) uses only 6 bits (5.625 deg/bit) and it still is used by WA25. That is a purely digital system using opto detector for each of the 6 bits. Most boat transducers use two potentiometers giving a pure analogue signal.
  9. Joakim

    VOR Leg 7 Auckland to Itajai

    It seems to me you don't know was OSR overridden or not. Also I haven't seen any confirmation about having or not having an emergency antenna, which could be very different from the "second antenna", which was not installed. I don't know what this "second antenna" is, but I would guess Witt is talking about a permanently installed secondary antenna, not an emergency antenna you would rig, when the mast comes down or for some other reason the mast top antenna failed. This second antenna would, of course, also comply with OSR, if it was not installed to the rig. Actually OSR does not require an emergency antenna for VHF. It only requires it for "a marine radio transceiver" and only when the antenna depends on the mast. VOR boats have other radio transceivers as well so they may comply without VHF/AIS emergency antenna.
  10. Joakim

    VOR Leg 7 Auckland to Itajai

    You have been wondering why they did not have an emergency antenna, but you don't seem to know, if they had or not one on board. Nor do I, but I do know one can make them from cable and as you said OSR requires boats to have an emergency antenna. The skipper said that they would have found Fish, if they had a working AIS antenna. We don't know why they did not have one set up. Maybe on the following legs they start to seriously work on fixing the AIS as soon as they find out it is not working. Maybe they even modify SI to make it compulsory to fix AIS during a specified time, if it is feasible. Electronics is my profession so I may know more than they do about electronics and fixing them. But I don't know their level of knowledge about electronics.
  11. Joakim

    VOR Leg 7 Auckland to Itajai

    Other boats AIS power has a lot to do with my AIS receiving ability. As I told I can see other boats in 1-5 nm range and that is mostly in archipelago, with often islands between the line of sight. That includes boats with antennas on deck level. I hope VOR boats do use AIS for collision avoidance as well in areas with ships and other vessels. That is after all the main purpose of having AIS on board. But the point I tried to make was, that even an emergency antenna made out of coaxial cable is OK for AIS (and VHF), especially if it can be hoisted to a higher location. You can make one in a few minutes using just a knife, if you can get the cable out. Of course it wouldn't have the receiving range of a mast top antenna, but maybe half of that depending on how high it can be hoisted. And just as good range as a normal emergency antenna would have.
  12. Joakim

    VOR Man Overboard

    It could be that they had an emergency antenna, but chose not to set it up after they noticed the antenna had been damaged. Maybe they didn't care that much about AIS until MOB and then it was too late. They have a handheld VHF and other communication hardware, thus it was mainly AIS that failed.
  13. Joakim

    VOR Leg 7 Auckland to Itajai

    No, I'm not. I just told an example. Boats have only 2 W power and not all have mast top antennas. Obviously you would put the antenna as high as you could when searching for a AIS MOB. The antenna in good enough for that, it's just the height that counts. For collision avoidance having the antenna inside the boat is sufficient, at least for avoiding ships.
  14. Joakim

    VOR Leg 7 Auckland to Itajai

    The NYT article uses term "second antenna", not "emergency antenna". It still could be that they had an emergency antenna, but didn't rig it up. Maybe it is too difficult to rig up and they were too busy with MOB. Even, if they had no emergency antenna they could have built one using the cable running inside the boat and this instruction (in Swedish, but picture is enough). The AIS receiver antenna in my boat is built from cable and installed to the bulkhead between cockpit locker and head. Still I can see ships from 5-30 nm and boats 1-5 nm. In an emergency e.g. a halyard can be used to lift this type of antenna as high as the cable reaches.
  15. Joakim

    VOR Man Overboard

    Now it has been confirmed they had no working AIS receiver. "For Scallywag, this lifesaving new technology went away when, two days out of Auckland, the boat’s lone A.I.S. antenna at the top of the 100-foot mast was damaged in the strong winds. “If we had our A.I.S., we would have found him,” Witt said. “I’ve learned that redundancies in this system is an example of change, like a second antenna.”" Source: https://www.nytimes.com/2018/04/18/sports/volvo-ocean-race.html No emergency antenna? No secondary AIS receiver? Mast down and part of crew washed out makes the AIS MOB useless? Or now just strong winds damaging the antenna.