waterballast set-up for 40ish foot (almost) racing yacht

Discussion in 'Boat Design' started by patrick2wd, Nov 7, 2014.

  1. Joakim
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    Joakim Senior Member

    Then you are looking for a ~1 kW pump and 50+ mm pipes.
     
  2. patrick2wd
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    patrick2wd Junior Member

    how many amps is that kind of contraption pulling, engine would need to run, I think?
     
  3. Joakim
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    Joakim Senior Member

    1000 W @ 12 V = 83 A, but the pump may take less depending on its load. Say 4 minutes of 80 A is just 5 Ah, but at that high current it may take much more (10 Ah??) out of the battery due to Peukert effect.

    You don't need to have the engine running, but you need to recharge after a few tacks. Also battery voltage will drop at that hight load.
     
  4. philSweet
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    philSweet Senior Member

    Estimating power draw from data plate info isn't very accurate. The physics suggest about 10 watts for every l/sec just based on lift. Then factor pipe losses. Now factor mechanical efficiencies, which you have some control over. 100W battery draw would seem closer to the mark for 1000l in 4 minutes with a 1 meter lift. Or 1000W for a 25 second transfer, which would seem like a better idea to me, but more pricey. Most, if not all of the shifting can be done by gravity anyway.
     
  5. patrick2wd
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    patrick2wd Junior Member

    that will be the case here too.. for most of the time, depending on operation

    but we are only working out how/ what/ when etc..
     
  6. Joakim
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    Joakim Senior Member

    Yes it's not much, IF there is an efficient pump and not much other pressure losses. But there are many valves and bends to allow water to be pumped in both directions and also from sea. Even 50 mm piping results to quite high velocities.

    And the pumps are not efficient at all at these operating conditions unless you find one optimised for such a high flow rate + low lift (= axial flow pump).

    I'm not suggesting that 1000 W is accurate, but it is the order of magnitude. I just quickly looked at some industrial pumps cabable of 300-400 l/min at 2-3 m lift.

    With 100 W it will take at least 10 minutes using a modified bilge pump as I have seen in a Class 40 boat. E.g. the 230-250 l/min bilge pumps tested in die Yacht magasine provided only 71-136 l/min through 2 m 32-38 mm pipe and 1.5 m lift without any bends and valves. They were rated 15.5-18 A, but took 9-12 A. So 200 W pumps running at 120 W. That is ~20% efficiency, if you calculate just the potential energy from lift.
     
  7. philSweet
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    philSweet Senior Member

    For what its worth, I used 45% total efficiency. I think that can be had with off the shelf kit. I wouldn't start with a bilge pump, a lot of reserve is built into to those to deal with trash in the water.

    Attached is a screenshot from Grundfos. I just banged in 75gpm at 10' head and this is what it spat out - 222 watts at 10' head, which should be plenty. The pump itself is an ac closed can circulator pump, so not what the OP wants in terms of a motor. But the pump is okay and representative of the efficiencies you can expect in small industrial pumps.
     

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  8. Joakim
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    Joakim Senior Member

    I wouldn't start with a bilge pump either, but you need to use something that can handle sea water and some trash as well, unless you are using only fresh water.

    It is plausible to use only 220 W, but then you need to use a pump like that and be very carefull with the pipe line design. 10' is not that much for a such a complicated system unless you use much bigger than 50 mm pipes or several pumps to simplify the piping.

    The pump you used as an example costs 1300 € (2000 € stainless steel) and weighs 20 kg so I can understand the bilge pump solution I have seen.

    Can you find any 12 V sea water pumps with similar specs?
     
  9. philSweet
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    philSweet Senior Member

    Yes. We don't know what the minimum valve logic is. And we don't know the geometry or the control restrictions. And we don't know the available power. And we don't know the overall risk associated with a failure, so assume it is big. It would be very nice to bump the power up and cut the size of everything by half. I figure about $5000 - $6000 for plumbing. That would drop by $1000 if could be made work with 2" pipe stuff. But I think most needs to be 2.5" ID.

    If we assume single action valves and full logic, you need 14 valves (intake = 4 tanks + sea +bilge; output = 4 tanks + sea + washdown; plus a pair of gravity transfer valves). If you use cheap knife valves on the suction side, you need a suction pressure management loop with a little control valve. The distribution side should use better valves, but could probably manage on knife valves with just a big overflow pipe to limit pressure (earlier price based on all 2.5" remote actuated valves, not knife valves). With 14 valves, the system would be tolerant of any single point failure.

    If you scandalize some of the logic, the piping can be shortened. Some of the pipe can be run inside the tanks and used to support the baffles. If you allow double action on some 3-way valves, you can also save on space, but I don't think I would want to do that unless I had no choice, or had a really big budget for custom stuff (and you will likely loose single point failure robustness).

    One thing I did go looking for and couldn't find are efficient bulkhead fittings with bell ends for the tank connections. They don't seem to exist. It seems one has to mold ones own bell-mouthed sumps and flange them onto the tank bottoms.

    Don't know of any dc pumps that big. They'd be heavy, though. Probably better to run off an inverter. So add another $200 for a dedicated 600W sine wave inverter. Inverter and any electric actuators run off 24 Volt.
     
  10. FAST FRED
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    FAST FRED Senior Member

    We have a 33x28x10.6 sail boat designed b M Griffiths.17,000lb disp.

    With a 40% ballast ratio the installed 105G per side water choice does near nothing .

    A Bronze 2 inch Edson moves the water easily BEFORE we tack , as it just helps the high side gravity feed. Only takes a short while.

    On passages we seldom bother , tho we will consume low side water first.

    Best use of the system so far is blowing older FW overboard if a better supply source is found .

    After winterizing the spring chlorine flush goes fast with a way to dump the water with ease.
     
  11. Tad
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    Tad Boat Designer

    Lots of different ways to look at this problem.

    In Pen Duick V Eric Tabarly used a single hand pump and 7 valves to run four tanks.

    PenDuickV.jpg

    In Katie G Eric Goetz used no pump at all.

    KatieG.jpg

    And Yamaha uses all sorts of plumbing.....

    Yamaha1.jpg

    Yamaha2.jpg
     
  12. philSweet
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    philSweet Senior Member

    Thanks Tad

    It's interesting to see that everybody seems to be okay with knife valves.

    One thought on pumps. If cruisers have electric winches, wouldn't it be nice to have the same motor run the water pump. I think Lewmar and Harken should have some accessories for their electric drive motors. Motors that can run a series 65 winch ought to be able to push a bit of water around.

    A second thought regarding getting the size of the plumbing system down to something reasonable. If you used the sea pickup and dump system like in the Martin design, you could turbo that by installing a small jet of pumped water near the inlet. This would give you the head rise needed for a much more versatile system, and it could be small, 1.5" pressure plumbing or so. Not very efficient on paper, but you might only need it to top off the tank or when you blew a tack or something. The entire system would fit in a 5 gallon pail.

    So basically, you have a sea chest with a few of these things - http://www.lagunakoi.com/Mixing-Eductors-Pond-Fittings-sc-149.html - one in each 2.5" line going to a tank, followed by a check valve in the 2.5" line. But the valves controlling the jets are only 1 or 1.5" valves - much tidier, cheaper, and configured to operate with normal pumps. <edit added> Actually, the check valve could come first, and that might have some advantages.

    <edit added> found these - lovely specs, 30 psi input would give about a 2.5 gain on volume. Too bad about the price:( . You only need to valve 31 gpm at 30 psi or 25 gpm at 40 psi to get 65 gpm transfer. Pump covers deck wash and anchor wash duties as well. I think this could work quite well.

    http://parts.clark-reliance.com/2-ml-eductor-316-ss-tml-18-s/

    Sizing document - http://www.clarkreliance.com/site/applications/DocumentLibraryManager/upload/e-200-1.pdf
     
  13. terrnz
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    terrnz Junior Member

    I looked at waterballast for a boat I am working on. Here is something I found you might find useful.
    The Class 40 and similar rely a lot on water ballast and yes they are similar beam to yours, 4.5M. This gives you a big boat that also needs a lot of sail to push it. The downside for me was that you are carrying an extra 1000kg when you really need it power reaching. Expensive pumps are not necessary as they use a scoop, you can buy off the shelf, which provides enough head, travelling at 6 or 7 knots to fill the tanks under the gunnel and large bore transfer plumbing with gate valves. All this does impinge a lot on the interior not important in a flat out racer but not what I wanted.
    Utilising the fresh water you carry and pumping it from tank to tank, side to side and fore and aft would give you a bit more stability and trim options fore and aft.
    Consider this: a 4.5M beam 12M with water ballast built reasonably lightly gives you a boat of around 4500Kg plus water ballast. This gives around 80000Nm or more of righting moment at 30 deg heel. You are going to need a fair bit of sail to get this going 18m plus of mast. You will have to go to a carbon mast as an alloy spar will simply be to heavy, the sailing loads will be huge and deck gear of a size more associated with a 16m yacht.
    I think you will find the costs spiraling. You could buy yourself a first or second generation Class 40 quite cheaply! a fraction of a cost to build.
     

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  14. patrick2wd
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    patrick2wd Junior Member

    How would you open valves?

    if your sailing singlehanded... what would you use?
    I havent found anything yet..
    and for the pump(s), 24 volt would be good, but could that handle 1500 liters in 3 ,mins?

    there is a company near where I live that do all kinds of electric motors stuff.. but that would only be the engine..
    I'll look at this option later.. and the grundfoss looks good, but pricey..

    and is it that the class40/Orma's/ minitransats use a scope to fill ballast tanks?
    Its been a while since Ive been into this, and for what I remember, there is this scoop that can turn 360 deg. for filling and dumping.. but not sure if that is still used..

    eduit; just refreshed and read the last posts,

    very likely that the boat will be build in carbon, so will be quite a bit lighter that a C40..
    interesting read Terrnz!
     

  15. terrnz
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    terrnz Junior Member

    I think you mean this

    no electric pump needed with the scoop, you need to be travelling at speed, which of course is when you need the righting moment. The tanks must be properly vented and the transfer is from high to low side through large bore pipes (about 3 inch) and gate valves, before tacking.
    this and the BOC before used to have a limit on ballast no more than 10 deg heel, from memory.
    This is not new, its been around for at least 30 years to my certain knowledge.
    You rotate the scoop 180 deg aft to dump water and the venturi effect sucks it out with the aid of gravity.

    Have you done the numbers on loads? How advanced is your project? what sort of racing do you plan? If you intend building in carbon you must have a huge budget?
    You should check out the Class 40 web site if you have not done so already.
    you will find it has all been done before.

    Personally I am more interested in canting keels but the engineering of all designs known to me is agricultural and fundamentally flawed with too many possible points of failure plus I do not like the ides of a bloody great hole in the bottom of the boat.

    Question for you; have seen the imeadiate benefit of dumping only 500 litres of water has on your boat speed in a boat of the size you propose? I have.
    Extra weight is largely the enemy of a sailboat if you want to go fast reaching.
    more weigh=more dollars
     

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    Last edited: Nov 19, 2014
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