Windlass specification issues

Discussion in 'Boat Design' started by MikeJohns, May 25, 2006.

  1. M&M Ovenden
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    M&M Ovenden Senior Member

    Hi Fred,

    I wouldn't think a stater motor would be used for a windlass. I thought they are designed for high torque/short time, and running them for 2 minutes would lead to early death.

    They must be custom wound for this application, right ?

    Hi Mike,
    the 12 V 24 V question is a big one. Doubling the voltage allows 4 times the power down a cable with the same losses. It's hard to justify going to 24V for one piece of equipment vs running some big 4/0 cables (or perhaps a second battery up front with 2/0 cables).

    Cheers,
    Mark
     
  2. FAST FRED
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    FAST FRED Senior Member

    hey must be custom wound for this application, right ?

    Nope , remember they are expected to work REALLY hard while cranking that 454 into life . They dont work that hard at all just yanking an anchor & some chain aboard .
    While starter motors are a poor choice to run an engineroom blower , 5 min a day at recovering the ground gear is small stuff.

    The big advantage of tiny replacement cost , and universal avilibality sure beats having a "more efficent" motor that costs hundreds and months to replace.

    When the local Autozone has a sale , there $24 each.

    Even I can afford a spair!!

    FAST FRED
     
  3. MikeJohns
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    MikeJohns Senior Member

    One extra consideration

    Decent spur gears will last forever and are very efficient. Worm drives are an engineering nightmare re wear and power loss. So worm drive units should have easily and cheaply available replacements, usually the worm is hard and the gear is soft and wears rapidly, look at replacement costs. As far as machinery goes they are pretty simple and many fishing boat here have them made to order for the same price as off-the shelf units. usually based on a stainless steel frame and plate cover.

    Mark
    I agree 24 v is a pain if you are running 12v alternators since if you use contactors to shift the parrallel series battery setup you can't run the alternator into the system at the same time. You could go 24 V from the start for the major power hungry systems. It's less of a pain tapping off 12 volts for the low power electronics than producing 24 from 12 v banks for the current hungry gear.

    I'd be interested in your thoughts on this as an elect eng.

    Cheers
     
  4. FAST FRED
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    FAST FRED Senior Member

    Not an electrical engineer , don't even play one on TV.

    A thought , most cruisers will have an inverter for silent use of shore side toys.
    If it were of suficent size it could run a 120 or 240v electric windlass motor.

    Advantage would be the power , cheap replacement cost (water proof industrial motors are common) and vastly simpler wiring to the windlass.

    Speed controll would be easy .

    Only downside , a good Sine Wave inverter is expensive , but if its aboard anyway....


    FAST FRED
     
  5. bntii
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    bntii Senior Member

    Seems more likely that the vessel with a large enough bank to supply an inverter for this application will have a gen set to do the job better. No?
     
  6. FAST FRED
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    FAST FRED Senior Member

    Sure , but getting underway the main engine is on & probably will be on for a while.Battery charging is avilable , no noisemaker required.

    Remember the windlass will require power depending on the LOAD , so in most operations is simply recovering the anchor & chain.

    No bigggie, IF you own that BIG inverter.

    FAST FRED
     
  7. bntii
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    bntii Senior Member

    Any ideal what amperage is in the ball park?

    I just put a 2 kw inverter in our boat and like the ideal of the light ga 120 cable run forward.

    T
     
  8. M&M Ovenden
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    M&M Ovenden Senior Member

    Hi Fred,

    I had not actually thought about the idea of using an inverter to power an AC windlass motor. This idea really has some merit. I'll put some more emphasis on the need for a sin wave inverter. Motors won't like the square wave of a modified sin wave inverter. The square wave current will see a larger impedance from the motor windings. To make a long story short the motor will need to 'work' harder with a square wave input, more work = more heat =reduced mean time to failure.

    I don't think I would personally go this route, as the inverter is just one more link in the chain, so to speak. While solid state electronics are getting more and more robust, there is still a chance of failure with all those components inside. I would think this would be the weak link of the system.


    Hi Mike,

    I'll start with a little disclaimer. I'm not employed as a 'battery engineer' nor do I have a PHD in Chemistry. I have however read many technical articles on the subject of lead acid batteries (Gell,AGM,Wet) from a personal interest standpoint (liveaboard ,on the hook for 2 years) and also as a requirement for my employment (instrumentation back-up batteries and SCADA applications).

    While there are many ways to accomplish a split 24V / 12V system, I think the battery series / parallel switch would be one of my least favorable choices. I'm not saying this approach won't work, but I have a few reservations. The interconnects will be cumbersome, good quality contacts will be expensive, the switch would likely have negative effects on the battery bank life span and the chance of applying the wrong voltage to equipment either through a mechanical failure or human error.

    From an engineering standpoint the numbers will always say to go with the 24V system. Cable gauges can be smaller for the same power transmission, yet the voltage is not yet high enough to pose a danger to users. The numbers don't take into consideration other factors involved in the decision cycle.

    12V stuff is everywhere. It's been used on boats,cars, RV's for a long time. Many more products are developed for this market than for the 24V market (trucks, light aircraft, buses). My employment has taken me to places like the Sahara desert in Libya, the rainforest's of Bolivia and the middle of nowhere Alaska. 24 V equipment in remote places like these is much harder to find than it's 12V equivalent. While I hope one day to take my boat to remote locations, and armed with the knowledge that the one thing you'll break is the one thing you don't have a spare for, a 12V system makes sense.

    Engines in the range for our boat have a 12V system. It is possible to keep this split from the house bank, but this yet adds another layer of complexity. Being able to use the house battery to start the engine quickly might change the outcome of a sticky situation.

    Most branch wiring will be 14 gauge anyway, as this is the minimum requirement for 15A breakers (most commercial panels come populated with them). LED lighting is so efficient it's almost a .0non issue (except for the fact you'll find more 12V LED products).

    The biggest consideration then is the high draw equipment. Windlasses, bow thrusters, inverters. If a boat was to have multiple high current users I would likely start to favor a 24V bank. In our case we plan on just having a windlass, all other equipment will be located close to the battery bank.

    It would be great to get some other feedback from people that have made the 12V / 24V system choice, and if they have and suggestions / regrets.

    Luckily, we have a some time to make a firm decision. If it becomes too much of a headache we can always opt for a manual windlass. Something along these lines seems about right:


    Cheers,
    Mark Ovenden
     

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  9. FAST FRED
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    FAST FRED Senior Member

    "12V stuff is everywhere. It's been used on boats,cars, RV's for a long time'

    And most of the house style goodies are very expensive Crap!

    Sure the lights, fans & pressure water , bilge pump or refrigeration is great in 12 /24.
    But things like a 12v blender are 10X as expensive and seldom last a year.

    Again a GOOD inverter saves the day (although hardly cheap).

    I prefer the Trace 2440 which has some great features.
    Sure its a good 100A 3 stage charger , but the best is the "pass thru" feature.

    You set the amps to the using system , say 15a from a puny power cord or 50A from a smaller noisemaker.

    The Trace will ADD current to allow the loads to operate with battery assistance as the set load is exceded.

    A friend is able to park an RV at our place in FL and on a 15A house cord run both air cond , or one air and the washer.

    The huge start load of the Air Cond starting , is handled by the Trace .
    This would allow any cruising boat to install a much smaller noisemaker , with a better chance of running it at 60%+ load , increrasing the srrvice life by NO underloading.

    The Trace also had a "Link" setup that shows the percent of battery charge.
    But its about $4000. and HEAVY !

    FAST FRED
     
  10. Syed
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    Syed Member

    In my humble opinion, compressed air will be a viable alternate for this type of application (Intermittent operation of anchor windlass). A portable gasoline engine driven compressor with a suitable storage tank can do the trick over air motor.

    Syed
     
  11. FAST FRED
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    If youre going to have aboard and maintain a gas engine , why not just gear/belt it to the windlass?.

    A Honda 6hp rototiller engine has a factory 6-1 reduction and is about $500. Brand New.


    The usual is to mount it where the windlass can be used as a Donky engine , hoisting heavy sails or spars , gear from a wharf or the dink , as well as the anchor.

    FAST FRED
     
  12. Syed
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    Syed Member

    You have hit the nail on the head.

    Syed
     
  13. M&M Ovenden
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    M&M Ovenden Senior Member

    Hi Mike,

    That's a very interesting article you posted about anchor rodes. It really backs up 'rules of thumb' that I have read in other locations/books. It seems that most articles like this usually have the line “for extended cruising go up one size of chain”, which leads me to a question for you and the forum.

    Sizing from the ABYC/other articles leaves us with a chain size of 3/8” high test. (Boat is 50ft, up to 55000 lbs). Should we then 'go up one size' ? Looking a ACCO chain, this would put us in the 7/16” market, but it seems this is not a regular stocked item, the next size then being 1/2”.

    Should we:
    1)Stick with the 3/8” and plan on setting second anchors in storm conditions.
    2)Go with 7/16” and deal with any sourcing issues.
    3)Go up to the 1/2” (seems oversized for our boat).

    Looking forward to everyones comments / suggestions.

    Thanks,

    Mark Ovenden
     
  14. MikeJohns
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    MikeJohns Senior Member

    M & M

    It comes back to intended use, but if I had a 25 ton boat I would use ½ HT chain.

    If you are cruising in the Pacific for example then your main insurance is your ground tackle. Rope doesn't like coral and 3/8 is a bit light for a 25 tonne vessel in often exposed anchorages.
    But if you are in more ideal conditions 3/8 HT will be fine. Shock loads on chain can be quite high which that website explains.

    What did you allow for in your weights and moments calcs? You want around 100m of chain if that is your primary rode. Half inch will be about a third heavier though and here we come back to the length of rode, in some cases you will be better with that third as added length or a second chain. In higher latitudes you are often caught unawares with an instant gale and if anchored on what becomes a lee shore you are in relatively shallow water and inevitably the shore is close astern, then only chain thickness saves the day since scope is impossible.

    I’ll add an anecdotal tale here:
    It's not always possible to run out a second anchor. We were asleep anchored behind a reef in bad weather and contrary to the forcast the wind increased to around 50 knots average, the surf started washing over the reef. We had no options but to sit tight, the chain was snatching so hard that we were thrown of our feet at times, I let out chain until we were 6 feet from the rocks astern and endured a miserable 2 hours expecting the chain to snap with every surge. That was 7 years ago and it still scares me today. Our boat is 16 tons and we had 3/8 HT chain. I was using 8 ft of nylon snubber but it may as well have not been there. … Careful inspection of the components afterwards showed a bent shackle but no chain link distortion at all. We had an 80lb plow and it was dug in so deep afterwards that we could hardly trip it.

    All the best
     

  15. Frosty

    Frosty Previous Member

    Mike is spot on. Achoring seems at first such an easy thing to do. I mean all you gotta do is throw the anchor over the side with some rop on it?

    I am not going to add any thing to mikes post exept it is a carefull matching of anchor to chain and boat and comes from skill and experience.

    The bummer is that you only know you got a good hold is when you lift it up!!
     
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