Choice of electric motors as inboards for a catamaran

Discussion in 'Electric Propulsion' started by xellz, Jul 16, 2017.

  1. DennisRB
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    DennisRB Senior Member

    Perhaps you can send your musings to world regularity bodies to have the values changed so they meet your more stringent standards? Perhaps a passing 747 airliner might loose part of its undercarriage and it might land on your boat killing the occupants too?
     
  2. BertKu
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    BertKu Senior Member

    The probability that a 747 is loosing its part of its undercarriage is zero. The probability of somebody dying when, wet, because of salt, maybe has a small cut and has a skin resistance of 1000 Ohm is a reality when sailing in sunny area's and is fiddling with 48 Volt. I am not interested in those so called world bodies. Bert
     
  3. DennisRB
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    DennisRB Senior Member

  4. BertKu
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    BertKu Senior Member

    Dennis I am not willing to go into a silly dispute like I say this and you say that. If you want proof of the pudding. Make both of your hands wet with salt water , make a little wound and put 4 x 12 Volt batteries in serial. Then you put your left hand around the minus an with your right hand you touch around the plus 48 Volt connection. You will be part of the 99% of the population, according to the official report as previous mentioned, that you cannot let lose anymore and will die. At least we don't have a silly person called Dennis not accepting official, not mine, warnings. You want to try it, be welcome, you probably will not be part of the forum members anymore. You will die, here is another proof of dying.


    Just google :
    Dangers of Electrical Shock

    The severity of injury from electrical shock depends on the amount of electrical current and the length of time the current passes through the body. For example, 1/10 of an ampere (amp) of electricity going through the body for just 2 seconds is enough to cause death. The amount of internal current a person can withstand and still be able to control the muscles of the arm and hand can be less than 10 milliamperes (milliamps or mA). Currents above 10 mA can paralyze or “freeze” muscles. When this “freezing” happens, a person is no longer able to release a tool, wire, or other object. In fact, the electrified object may be held even more tightly, resulting in longer exposure to the shocking current. For this reason, handheld tools that give a shock can be very dangerous. If you can’t let go of the tool, current continues through your body for a longer time, which can lead to respiratory paralysis (the muscles that control breathing cannot move). You stop breathing for a period of time. People have stopped breathing when shocked with currents from voltages as low as 49 volts. Usually, it takes about 30 mA of current to cause respiratory paralysis.
    Bert
     
  5. DennisRB
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    DennisRB Senior Member

    Go back and read my posts. I agreed it would not be impossible to be electrocuted. The point it that its extremely unlikely. You can drown in a puddle, you can break your back from falling on flat ground. You could be killed by having airline parts fall on you.

    You are not understanding the point. The requirements you state are so "silly" that the chance of them all happening together are so small you may as well be scared of falling airline debris killing you. Your scenario requires ALL of these things to happen at once.

    Current flow though the heart by one hand being on positive and one on negative. That chance of even this occurring is at a silly small level unless you do it on purpose or are a total mor0n. (I can't believe the forum flags that as a swear word :p)

    That then needs to be multiplied by not one but BOTH hands having open wounds, and each open would directly touching the respective positive and negative terminals while simultaneously being drenched in seawater.

    While all that happens both hands need to be holding the conductors in such a way that the muscle tension clamps onto the conductors rather than pulls away from them.

    If you really think that's a danger worth talking about compared to the thousands of other ways you are more likely to die on a boat you better stay at home. Most boats have 110-240v systems operating on them. Are these people all suicidal Bert?
     
  6. BertKu
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    BertKu Senior Member

    There are many reports that AC up to 500 Volt AC , even with salt water and a wound, people survive. Not by 50 Volt + DC. You are missing the point. Bert
     
  7. BertKu
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    BertKu Senior Member

    More and more sailors will move to electrical DC propulsion, whether it is for moving in or out of the harbours or other reason in the next years to come. DC is totally different then AC, as explained in my previous reply AC is safe up to 500 Volt AC. Your mast is most likely from metal and is earthed via the lightning protection. The engine is normally also to earth. In Brisbane, it is normally too cold to walk barefoot or sail without gloves. If you walk barefoot, you only need one hand to touch the + 48 Volt DC when working on a problem close to the engine or wherever, special on metal boats like aluminium. You don't need 2 hands. You don't need wounds to reach low resistance and work with a tool which is not isolated. All what you need is salty wet hands to reach low skin resistance. If you had googled, you would have read many reports that by up to 10 mA people can be in trouble. 50 Volt DC divided by 10 mA = 5 KiloOhm . To reach 5000 Ohm with salty water is not difficult to obtain with one hand and barefoot.

    My wife always says, don't argue with a person who is not qualified. You lower yourself to his level. All what forum readers should know is, if you go for voltages higher than 48 - 50 Volt, take special precaution. Not a problem to go for 200 Volt DC, but you need to work with insulated gloves and if you work on a problem disconnect the minus side of the battery. Dennis, like I have said before, I am not interested in an argument. For me this topic is closed.
     
  8. BertKu
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    BertKu Senior Member

    Xellz, this is certainly a very good option to have your batteries charged with the product from a French company. I received an invitation to visit them at their stand. It also will be too far for you to travel to the Netherlands, but maybe the product could be of interest to you. Bert

    Invitation to the METSTRADE Show 2017 - register your free visit

    Dear Mr/Ms,

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    We are looking forward to the show and welcoming you there.

    With kind regards,

    SOLAR CLOTH SYSTEM - UK SAILMAKERS FRANCE
    Alain Janet
     
  9. gonzo
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    gonzo Senior Member

    The 50V threshold is a throwback to Edison. His phone systems worked on 48V, so he lobbied for legislation getting any system at less than 50V to get exemptions from many safety regulations.
     
  10. BertKu
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    BertKu Senior Member

    Yes, Edison knew that voltages below 50 Volt DC are not a danger to life. The majority telecommunications products do work on 48 Volt DC, like the Siemens EWSD exchange or the Plessey exchange or any other European exchanges. So I am not surprised that he applied for safety exemption. Bert
     
  11. gonzo
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    gonzo Senior Member

    He developed his phone system at 48 V. Regulations came later.
     
  12. xellz
    Joined: Jul 2017
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    xellz Junior Member

    While catamaran does have quite large area i still think it's not really viable solution, especially this one. If i add solar panels, it will be solid or semi flexible ones and well mounted to avoid any movement by wind. Type you mentioned definitely won't last long and efficiency for area isn't exactly that good either. Nice solution for sails though, especially if have money to spare. For fun and with lots of money sure would be nice to get huge solar array, but sadly it's not for me.

    Diesel genset is still a priority. Want one in 10-12kW range for long trips to different islands and mainland, everything within 40-80km range. But it's still difficult to tell exact speed/energy consumption. Solar is last on my list.

    I'm stuck in paperwork hell currently, but i bought plans for Jazz 30 recently, without plans i can't even continue my fight against japanese bureaucracy. I'm trying to get permission to register this boat as commercial fishing vessel, but catamaran, especially custom build is not really welcome and met a lot of resistance. No financial or any other type of help too, as i originally planed. I'm not sure how and when i can complete this project, but one thing for sure, i will try my best to finish it. Even more because i want to prove, that fuel efficient hull shape is not only for entertainment (i.e. yachts) and that in certain circumstances electric propulsion is already better,safer and more cost effective than common inboard diesels. Not only for expensive show-off projects or tourists attractions. Funny thing is, local fisherman association understands my reasons behind this project and welcomes it, can get some free help during building too. But prefecture officials are stuck in like 50-60 years old ideals.
     
  13. BertKu
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    BertKu Senior Member

    Hi Xellz, I am sorry to read that you are struggling with officials, we had in the last few days also our share of those problems. I understood that you need to concentrate on first come first and indeed can see your point that you leave solar for last priority. Just in case you win the lotto, the Dutch in the solar race over + 3000 km in Australia 2017 came first, due to the fact that they used solar cells which generates also with cloud overcast. By the time you may need solar panels, the Dutch manufacturing may be up and fully running. Good luck with your project. Bert
     
  14. fallguy
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    fallguy Senior Member

    Weight and displacement should be leading your planning. I was considering the Skoota 28 and I didn't feel it had needed displacement for my wishes, so I am building the larger Skoota 32 in foam. The dry weight of the Skoota 28 is 4000 pounds, with an available displacement of 5060. This means you get 1060 of gear and fuel. The downside of the Skoota 28 for you will be displacement will only allow so many batteries. If you extend the boat a frame to a Skoota 30, or you modify the cabin to the Jazz setup; the boat would allow the same displacement at lighter weights and your motor/battery configuration could be bigger. Think of it this way; you can build the same boat lighter and the weight difference allows you more loading.

    What you need to do is a calculation of batteries, the motors that each battery configuration would require and see what the weight would be....

    For example, in gasoline... Gasoline and tanks at 20 gallons each (use 7#). 140# fuel
    20hp motor 100#
    Total for two hulls is 480#. Which allows you 580 for passengers and gear. Take off the captain and you only have room for a passenger or two.

    If you back into the amount of just say 500 pounds for a maximum for your motors and batteries; you would be able to ascertain maximum motors/battery configurations. as you will be at about 250# per side. If you have a motor weight of 150#; you could have batteries that weigh 100, etc.

    And for the Skoota 28, you don't want rudders; it is a hull designed for beaching. Putting rudders on it would be an abomination if you ask me, but perhaps kick up rudders might work and then you'd be limited in beaching to the props.

    I think the next step for you would be to determine the weight of a 4 battery bank, the allowed motor for said by weight and see if you are sadly disappointed in your options. Of course, you would need to include the diesel gen weights and fuel for the diesel generator. So if you have another 50# for that stuff; you are down to say 450# for the two or 225 per side, etc.

    Another thing to consider is building the boat in foam and trying to make her lighter, say more like 3500#, which would allow you 1560 total loading.

    Anyhow, when you do a loading calculation on the vessel and try to fit everything into the 5060 and 4000# dry weight figures; repost.
     
    Last edited: Nov 4, 2017

  15. xellz
    Joined: Jul 2017
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    xellz Junior Member

    High load capability can also lead to more energy consumption. From what i could put together, Jazz 30 is about right for my needs any more and it will be wasted on extra fuel consumption/battery weight etc. Main reasons would be ease of build, wide beam and still more or less efficient. Custom design, advanced lighter materials could get me better end result, but price would also rise considerably and i don't think i can build in anything but plywood/timber. Paying a company to build hull for me would add even more cost and in Japan this cost will be quite large. Majority of the time this boat will be used only by me or one extra person, at most 3-4 passengers. Beaching is not important and will be never done by me.

    Btw, Richard did test his Skoota with 12 ppl in total and still could reach 12 knots. His cabin is sure more heavy than what i'm planning to use, if i remember right from conversation with him, cabin alone was around 300kg if not more.

    Alongside paperwork, i'm currently trying to decide to go electric right away or outboards for undecided time. Electric is kind of unknown and there is some risk to it, but even if have to take small loan for electric propulsion, it should payback quite soon in lower fuel cost and maintenance cost. I'm expecting at least 100-150 days in a year and over 8h every day, diesel genset won't be used around island, only for longer trips or run it occasionally to keep in working condition. Anyway, genset will be bought after actual field tests on energy consumption. A bit hard to estimate, perhaps smaller in 5-6kw continuous output can be enough.


    Oh, and from information on Jazz 30, empty weight is 3100lb, displacement to WL is 5000lb.
     
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