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DDW

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Everything posted by DDW

  1. A simple passive one is just two diodes. They have to be big enough with enough heat sink capacity to carry the entire current service. These used to exist, but current ABYC recommendations prohibit them, because they will fail into the open condition, ABYC requires they fail "safe", that is, shorted. That isn't easy to do, and the reason they cost so much now.
  2. ^^ Again, this depends on the type of cruising you do. A daysail or overnighter between ports, you can pick your weather ideal for your boat. About 3 or 4 days out you take what you are given, and can only motor until the fuel runs out. If you can cherry pick the weather your averages will be high. If you have to sail in average weather your averages will be average. In that respect, racers (who must sail at the posted starting time) are similar to longer distance cruisers.
  3. My boat D/L ratio is 273. Will do an upwind VMG of about 16 knots. But that is the trawler, and the 380 HP Cummins has to be wound up to full chat. One big problem with sailing fast upwind is that in the seaway developed by the necessary wind, the motion is appalling, no matter the boat (well, above 100' or so LOA it gets better). In flat water and good wind, great - when you can find those conditions. In lighter wind your VMG sucks anyway, and a fast boat only makes it worse unless it is extremely weatherly.
  4. With an offshore corporation and a local shell LLC, the liability will be minimal.....
  5. Yeah, not thinking "manufacture and sell", just "design and test". I doubt large fortunes are being made in the yacht anchor business. Most yacht buyers of anchors value price first and performance second, if at all. However a nice DYI design knowing what you do would let a select few with the skills to make one enjoy it. Right now if I was building one it would probably be like the Spade except with a solid shank. Ti and W would be the next step. Perhaps spent uranium as ballast, the business proposition would be to accept large amounts of cash to dispose of spent uranium, and give the anchor
  6. Steve, liked the self launch test but there is one thing you skipped over: the self launch chain drag for the Spade? My Spades have been fine at that, just wondered how it compared with the others. I have two boats now, on both I designed or modified the sprit/roller to fit the anchor(s) for launching and secure storage. I guess no one else does that? Often quite a lot can be done just by changing the roller size. Have you considered designing your own anchor? You probably know as much or more than anyone in the world on what makes them work at this point ....
  7. Only on the Yanmar, not on Volvo (or at least some Volvos). My Volvo D2-75 has a single boot and no sensor. There are more than a couple of saildrive manufacturers. My aforementioned Volvo has very little on it manufactured by Volvo - the engine says Perkins/Catapillar in the casting but is actually a Shibaura (IHI), the saildrive is manufactured by ZF/Hirth. I think the label on the top might be made by Volvo and perhaps the shade of green paint. Many of the engine parts can be purchased from a local New Holland tractor dealer. Lots of people make anodes for saildrives, I can pick f
  8. With modern seals, a shaft can be as dry as a saildrive. There is a (vanishingly) small possibility of the seal failing and flooding the boat, but no more risk than a saildrive boot failing and doing same.
  9. Those things are resistive loads, and the amperage draw will be proportional to voltage, not regardless of it. For a rough test, since you are going between about 12.5 and 10.5 volts you can ignore that and be within 20% or so.
  10. We did this to mine when it was new. In addition to keeping the barnacles out, it now corrodes only from the outside in, rather than also from the inside out. Having owned both: two identical boats in identical condition, I'd take the shaft drive. Any significant difference in them, I'd let those differences decide, rather than the drive type. It isn't just ease of install, my boat was custom built, could have had whatever I wanted. But the plan dictated either a saildrive or a V-drive, and I took the saildrive over the V drive (with stuffing box under the engine/trans). The positi
  11. This is becoming common. Powersonic for example has a whole line of these in a large variety of sizes (for a couple of years now), very reasonably priced. I am using one for the instrument battery in my glider, and have tested the accuracy of the monitor by charging and discharging several cycles on lab equipment, and it is accurate. I think the parasitic draw is minute, less than the self discharge rate of the battery.
  12. Firefly are a unique technology, considerably more expensive (about 1.5x), and only available in two sizes. LFP batteries are approaching their price point from above. Lifelines (if properly treated) will last a long time. I'm just replacing the 10 year only ones in the trawler, the ones in the sailboat are due for replacement too (15 years old).
  13. 38' boat don't know, but for my 45' boat, the proposed SS rudder post was around 160 lbs, the carbon one we made for it was about 40. And stronger. A minor consideration: with the SS post we were going to need a thrust washer on top to carry the weight, with the carbon we needed a thrust bearing on the bottom to carry the floatation.
  14. On the sailboat I've got the Whale fittings everywhere, and there are a few between the tanks and the 4 way selector valve feeding the pump. Even with the Jabsco there have been problems, particularly with one tank. I chase around and and wiggle or disconnect-reconnect the fittings and get it to work. On the RV it's those cheap compression-sort-of fittings but a pretty short run. Helps to have a nice clear tube going into the pump, you can see if there are bubbles. Suction side leaks are insidious. When first built I could not get more than about 15 gallons of diesel out of one tank before it
  15. Well you have confirmed by suspicion that the suction side has to be truly vacuum tight. Even the typical Whale shark-bite type quick connects aren't vacuum rated. I think the accumulator probably contributes to the priming issues because it can develop very little pressure when dry, and has to push that through the internal check valve. If it also has to do that against pressure in the accumulator it can't make matters easier. I cannot get it to prime into a shut system, I have to open a tap while I prime. Once the gears get a little wet it takes off. A solution I've thought about is to put a
  16. IStream, how much delay do you get when turning on a tap? And where is your pump in relation to the tank? This is only annoying to me when taking a shower, as I have the trigger shower head. Pull the trigger and there is a momentary droop in pressure. It has varied a bit and seem to do with any air in the suction side, and also the water level in the tank. I have had trouble with suction leaks on that side.
  17. My experience with normal pumps w/accumulators, Jabsco variable speed, and Marco variable speed (currently have all those setups in one thing or another). Normal pump with accumulator works, but there is pressure variation between the cut in and cut out point, and the accumulator does not smooth out the pulsing of these multichamber pump designs. The Jabsco ones work - for awhile - and keep pressure pretty constant. There is a slight drop in pressure and lag until it come back up again when you turn on a tap (maybe a half second total time). If there is a pressure spike when you turn off the
  18. If you don't mind being Spam in a can, one advantage of a small boat is that it is stronger for its weight than a large boat. Tillikum is on display somewhere up in the PNW - forget where at this moment but I have seen it - and there is absolutely no way I would take that thing on any body of water wider than a short swim to shore. What he did in that is incredible, not just the seamanship but the depravation of comforts of any sort.
  19. Stabilizers prevent roll. They are quite effective properly done. Cats have a snappish roll and you can do nothing about it. A trawler works pretty well in areas with no wind. That's why around here they call sailboats "trawlers with masts". Mine will do 16 knots if you can afford it (at 7 knots, 1.8 g/hr, at 16 knots, 20 g/hr). We ran into one guy in a little 88'er that was cruising at about 33 knots. He was asked on the radio what his fuel burn was and he said 150 g/hr ("burn it if you got it" he said). But he left Port NcNeil (N end of VanIsle) mid morning and expected to be in Ast
  20. There are many complaints among the trawler crowd about the motion of power cats. Never driven one but I'd think they'd have a quick motion like a sail cat (which is the complaint). A stabilized full displacement hull is said to have better motion. There are a few different stabilizers now, fins and gyros, plus some using the Magnus effect.
  21. There are plenty of trawler style yachts in the 40 - 60' range that are single engine, in fact the majority of them. Sport fishermen or express cruisers will have twins. Many large single engine trawlers have a wing engine, Yanmar saildrive or similar, used as a get home engine. However the entire world's fishing fleet is comprised of single engine diesels and they don't seem to be a problem. Older (and current) large trawlers are likely to be Chinese built, and can vary widely in quality. KK and Nordhavn are at the top, but many brands are well down the quality scale. Issues are plywood
  22. Even though I like the cockpit BBQ, I don't think I'd take for $500. Maybe if he tripled the payment.
  23. Like the "modified sine wave" inverters of the past? These were a square wave with a flat spot at the zero crossing, trying to compete better with true sine wave - at least in the literature.
  24. The PWM controllers I've had have a clock. They run at a fixed frequency and variable duty cycle. Maybe they aren't all that way, don't know. Just a comparator switching around a fixed voltage would be a pretty dumb and very low end unit. Most PWM controllers (even the $15 ones) will do three stage charging etc. - much easier to design and build with dirt cheap voltage controlled PWM ICs and a $0.50 microcontroller.
  25. UHMWPE will definitely do that - it is similar to galling in SS. In a self aligning bearing I'd make the housing out of something harder, either a harder plastic or SS. Ti would be ideal but it is pricey both to buy and to machine. Ultracomp seems very good at this - I have some Ultracomp spherical bearings that are quite small and running at pretty high loads without complaint.
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