Joakim

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About Joakim

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  1. Joakim

    gyro autopilot compas heading

    You don't really need anything special for that purpose. Even a 8 bit processor can do all that. An AP is always limited by the rather slow drive unit. 10-100 Hz floating point processing can be done with a $2 (in small volumes) 8 bit chip (AVR, PIC etc.). E.g. I have a 8 bit AVR chip in my boat since 2012. It does all the calculations for instruments, calculates target speeds, start line functions, displays all the data on a graphical display and writes all the instrument data on a SD card etc. At the same time it is a MPPT charge controller for the solar panel and a battery monitor for two battery banks. All that running at 4 MHz, while it could do 32 MHz, and consuming about 10 mA. Similar processors have been available for a long time. I started using AVR in 2001 and the processing speed was up to the task already then. When did Silva release Nexus series? Early 90's? It uses a 8 bit processor to do all the instrument calculations in the server. Processors have come a long way since then. If more power is needed (I really don't think it is!), 32 bit ARM has been available for a long time as well. I did a similar system to my previous boat using a 32 bit ARM running Linux. It was way overpowered for the task, but still took only about 200 mA at 5 V (less than 100 mA at 12 V). That was in 2007. Modern ARM could do the same at a few mA.
  2. Joakim

    PHRF is not run by self-interested clowns

    36 point is only about 5% (depending on the actual rating). This kind of difference doesn't really need that radical differences in design. E.g. same sail area with a 150% genoa vs. a bit higher rig with just a 100% jib has a big effect. Actually that alone can cause about that much change. I just tested in a VPP putting a 9/10 rig and sails (102% jib) from a 1999 design to a boat from designed in 1981 with 7/8 and 150% genua. The change was 37 sec/M with a larger spinnaker and 32 sec/M with the original size spinnaker. The new rig had just slightly more sail area (22.4 m2 main + 16.7 m2 jib vs. 20.2 m2 main + 17.2 m2 genoa). Add to that a bit more efficient appendages and small changes in hull form it's easy to get 36 sec/m differences and even more without any different in the listed parameters. I have done a numerical fit to our local LYS rating system. It includes many more parameters (P, E, J, I, sail areas, LOA, LWL, disp, draft etc.). Still it doesn't explain the difference between say 80's design and a more more design or a difference between a cruiser and a cruiser/racer without adding some kind of a "hull factor" or a "design year". Using a desing year you need to adjust modern cruisers as much older than their real date or some desings like J/24 to much newer than their real data in order to get a good fit to actual LYS number. bgytr told later that the boats had similar hull form etc. I'm just trying to make a point that it isn't easy to give a rating based on basic dimensions and the same basic dimensions doesn't have to mean the same rating.
  3. Joakim

    ORC Missed Opportunity?

    That's a fact around here. During 70's and 80's Scandinavian boats were built in long series and it was very uncommon to have different keel or rig options. I don't mean the keels had identical fairing, but they had the same planform, about the same weight and exactly the same draft. Also the basic rig dimensions were equal even when in some occasions the brand of the mast changed during the production. 80's one off were mostly IOR boats and thus rather easy to rate based on their design year and IOR class. During the current century all boats around here have a huge amount of options. The worst production boat I can think of has had seven different keel options and almost all have two or three. E.g. you may have five X-37's actively racing, but there are at least three keel versions (1.7 m, 2 m and 2.3 m). So your empirical statistic must separate these five boats into three different boat types. With two different rigs that becomes a matrix of six boat types. By different rigs I don't mean aluminium vs. carbon or two vs. three spreader rig (e.g. First 36.7), but a clear difference in the height of the rig.
  4. Joakim

    ORC Missed Opportunity?

    The differences you have spotted are about 2%, which is to be expected when comparing different rating systems. You probably can find those differences between different PHRF fleets. I don't know much about PHRF and have only raced one PHRF race. But I have been involved in our local equivalent empirical system and ORC for more than a decade. When the difference is in the order of 2%, it is extremely difficult to say which one is "correct". Especially for a single number rating for which it is impossible to be "correct" for all conditions and the average "correct" depends on the average conditions and course set up. Our local empirical system (LYS) used to be really empirical. During the 80's most boats were built in long series and they all had identical keels and rigs. Also many of them raced. So there was a lot of data and a statistical rating could be calculated for many boats. For a valid statistical rating you need to have results from several different boats of the same type, preferably tens of them. Since then things has changed dramatically. Now most boats can be bought with 2-4 different keels and 1-3 different rigs. Also many boat models aren't raced actively. So there is just not enough data to statistically calculate ratings. The statistical calculation was dumped in Scandinavia about 10 years ago because of this. Now our LYS is based on some formulas, help from other rating systems and just a feeling. Old ratings are changed when it is felt they are wrong or other rating systems give a clearly different result. For any empirical rating system the big problem is always to get the actual potential of a boat which is badly hidden by the potential of the crew (including boat preparation). In LYS that was dealt with using only the middle 1/3 of the boats of the same type. So you needed big races with many boats of the same type and used only 1/3 of them in order to take out the "too bad" and "too good" crews. You still got the problem that some boat types will have better crews in the average than some others. Even more problematic are the new boat types, one offs and older boats with just a few racing. There is no way to get a real empirical rating for those, since the performance depends so much on crew and boat preparation. Sure you can appeal, if you feel your rating is too bad or your competitors is too good, but there is just no way of dealing with that properly. I can think of many boat types where only one crew is able to produce good results. In two cases these one win most races they sail. There are a few other crews racing the same boat type rather actively but always finishing in the back of the fleet. So what should a rating office do when someone appeals about these boat types? What if that one good crew didn't exist? Are there enough many FUN 23's to really have an empirical rating? Should J/24 rating reflect the performance of the best OD boats or an average J/24 in a PHRF race? There is probably about 5% difference between these. The real benefit of a VPP based rule is that you get the rating for the whole fleet in the same way (as long as you have equally good data for all the boats). You don't have to rule out the performance of the crew. ORC has a huge database of offset files, but it will still lack many boat types. Most are measured ones, not based on designer provided data.
  5. Joakim

    Flexofold three-blade drag vs. two-blade

    Well I did change from VP 3B to Gori 2B Racing so I don't lack that experience. I used the VP for about 2000 M and then changed to Gori in the middle of the season when the boat was lifted to clean the hull. Now I have used Gori for seven seasons and maybe 8000 M. The top speed dropped from 7.4 knots to 7.2 knots. Higher rpm was needed for efficient maneuvering, but with that the acceleration was very good and I don't see it as a problem. A very clear difference was clearly smaller prop walk with Gori making reversing out of my home harbour much easier than with VP. Before I tried the propeller my plan was to change the VP 3B back for cruising, but I never have felt it would be necessary. I don't even race anymore with this boat, but I still keep the Gori Racing. Also there was no change in noise or vibration, but I have a sail drive and there is plenty of clearance from the propeller to the hull. My Gori is just 15x10.5 and as a racing model the blades are rather small. So it's not a very fair comparison to 16x11 3B VP. Even at the same size FoF 2B has much higher bollard pull on reverse than Gori Racing. E.g. the test in Segeln measured 1800 N for 2B FoF and 1000 N for Gori Racing, both 15". I haven't said all 2B propellers are equal to 3B propellers. Just that FoF 2B and 3B are almost equal in performance. There is much more to propeller design than the number of blades. Gori Racing is designed for racing, not for optimal motor performance. Still I find it quite good for motoring and maneuvering. Another option for a racing propeller might be France Helices Racing.
  6. Joakim

    Elan 333 vs Elan 37

    The difference is not at all that big. At the same stretch 1x19 will be maybe 20-30% heavier, but that is just for the wire part. Turnbuckles and end fittings weight about the same. My boat has a rather same size rig as Elan 37. It has a bit over 60 m of standing rigging exluding backstay. The rod part of it weighs well below 20 kg without fittings. So wire would add only 5 kg or so, which is not much at the total rig weight of 170 kg (not including boom and running rigging). Bigger diameter and rough surface makes windage bigger, which is probably much more important than the weight. That's why I really can't understand fiber rigging, which usually has even bigger diameter and saves just a few kg. But windage difference wont make many seconds on an W/L race.
  7. Joakim

    Elan 333 vs Elan 37

    What do you mean by performance? If you mean stretch, it all depends on how your rigging had been dimensioned. You can dimension all the three types for the same breaking strength or for the same stretch. Or somewhere in the middle. Rod has less stretch for the same breaking strength, but you can choose a higher strength wire to equal stretch. Then your rigging is heavier and has more windage, but that part of performance would be more difficult to notice.
  8. Joakim

    Batteries

    It's not that uncommon to hear about a boat that has a flat battery and can't start an engine. 99% of these are user errors and would have been avoided by a really dedicated start battery, that can't be used for other purposes. Also one battery failing in a bank can quite easily flat the whole bank. Most sail boat diesels use very little current while running. Charging problems doesn't hinder the use of the engine. I don't think low voltage cutout works very well for LA batteries. What voltage would you use to make sure you can have many attempts to start and still be able to use most of the battery capacity? What would happen when a heater tries to start while a fridge compressor is running. The battery voltage can drop several tenths and go below the cutout.
  9. What kind of boat do you have? Where does the number 8 come from? What stops you and owners feeling the same racing in the normal division with 4 on board? As I told earlier I have always raced short handed according to your crew number list. Many others have raced the same boats with bigger crews, but I haven't seen any problem with that. This has included W/L races, long and short offshore races, handicap and OD classes. I have even raced in an OD national championchip regatta double handed, while the next smallest crew was 5 and some had 7 (First 31.7, maximum crew weight 550 kg). It was a lot of fun and we did very well. The owner had prepeared the boat well for efficient 2H sailing on a W/L cource. The result in a race depends much more on the boat preparation and the level of the crew than on the number or weight of the crew. If an owner feels he can't have a good result due to having a smaller crew, competing in a "short hand class" with a crew of 4 (or even 5/6!) will just make him dissappointed. He will still do as bad as he used to.
  10. Joakim

    New wireless wind transducer from B&G

    According to the manual you can set up a ST60 Wind as a master or as a repeater in the intermediate calibration. ST60 Wind Close Hauled is always a repeater. Should work and needs just AWA and AWS. Seatalk network does not transfer TWA and TWS, which are calculated in each instrument.
  11. According to your list I have always sailed shorthanded without knowing that. 22 feet with 2-3, 28 with 4 (occasionally 3) and 35 with 5. All those with a symmetrical kite. I have never had a bigger crew nor felt I would need to have. Of course more rail meet would have slightly helped in heavy weather, but I really hate to have part of the crew just rail meet. Why put shorthand in a separate class. Just give them SH positions and prizes, but let them win full crews, if they can. I have won several races doublehanded against full crews without any rating benefit.
  12. Joakim

    Pogo 12.50 Polars File

    Seems quite optimistic. Compare to these. Note two different keel versions. https://www.google.fi/url?sa=t&source=web&rct=j&url=http://data.orc.org/public/WPub.dll/CC/91322.pdf&ved=2ahUKEwix-Z7_yPzeAhUxi8MKHZyvC_YQFjAAegQIAhAB&usg=AOvVaw2zFll_UrQUGSwKZCUPrQC6 https://www.google.fi/url?sa=t&source=web&rct=j&url=http://data.orc.org/public/WPub.dll/CC/65019.pdf&ved=2ahUKEwix-Z7_yPzeAhUxi8MKHZyvC_YQFjABegQIARAB&usg=AOvVaw10Mb6v1iqngDUO8bSXcude
  13. It's really not that hard to install a wire connector or splice. How can you fix these at sea, if you don't know how to do them and rely on "professionals", which are not always that good.
  14. Spring-cage is old and not available anymore from Phoenix Contact for M12-5. E.g. https://www.phoenixcontact.com/online/portal/us?uri=pxc-oc-itemdetail:pid=1432583&library=usen&tab=1 Says no longer available and replaced by https://www.phoenixcontact.com/online/portal/us?uri=pxc-oc-itemdetail:pid=1424652&library=usen&tab=1 Which is a push-in connector. Still very easy to use.
  15. Joakim

    The 2018 Golden Globe Race

    Mark has reduced the distance to VDH by more than 100 M during the last two days. Mark has sailed 331 M during the last 48h and VDH only 228 M. Was that expected after getting around the Horn?