Cable Cross Section for 12V Winch

Are you willing to accept the risk of compounding the problem of a jammed hoist with the dinghy in a precarious position with the addition of an electrical fire?

Of course not, therefore I am asking... and on the other hand, from the theoretical point of view It did not sound too weird to me as (given the case of a jammed cable and a higher amp requirement) a fuse would blow, and fire would be prevented. In the latter scenario, even if fitted with a 90A cable, the risk of fire would still exist; or not? (I´m not teasing you, just wondering)

Those factors lessen the risk, but they don't eliminate it.

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I phrased my comment as a question, because that really is what needs to be asked, because that is the downside.

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The additional risk may be very small and not worth spending additional money on, or it might be very serious and silly to ignore. Where it falls in that spectrum has a lot to do with the boat, the expected conditions of use, experience of those using it, and your own tolerance for risk and way of valuing things.

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I realize my first answer might have seemed like I was teasing you, but I am not. My inclination, were I required to answer but not with a question, would be to recommend not attempting to save money on the cable, because I am ignorant of far too many of the specifics, because that is the safer option, and because the risk is to someone besides myself.

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To get back to something similar your question, if the winch jammed and say a 40A fuse blew but it was faulty and the case melted when it blew, shorting across to complete the circuit is was supposed to protect, in most situations, a 90A cable would be better to have installed than a 40A cable.

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Perhaps there are other options? Using a shorter length of cable should allow smaller cable to be used.... any chance at moving the installation of the winch? ...or the power distribution?

Is there another piece of equipment in the vicinity that draws that kind of amperage, use of which would never be mandatory at the same time as using the winch? Perhaps this could allow a closer connection?

The fuse part I do not understand.

If the cable is a 25 A cable and the winch draws more to operate you would have to size the fuse to protect the 25 A which means you will not be able to oeprate the winch.

Not being an electrician but I think you get the message that you should not leave any part in your system unprotected. Undersizing the cable seems just not to be right.

Use welding cable of the proper size. Much more flexable than battery cable. Wire is cheaper than boats.

Get the appropriate length of #8 SJOOW 2 or 3 conductor portable cord and use it. It has several benefits: it can be purchased in either black or yellow; it is suitable and approved for submersion in water; unlike welding cable it has all wires encased in one master insulator; welding cable would have to be tied or clamped together; the smallest welding cable that is readily available is #4 and that isn't stocked by many suppliers while #6 is the smallest made; the SJOOW can be sealed with a rubber smooth lined cord grip while welding cable would require 2 of them; and SJOOW is flexible enough for a dingy winch on a boat. Also, 1 foot of SJOOW with 2 conductors is much cheaper than 2 ft of welding cable of the smallest size.

Fuse the cable for 40amps, the rating of the cable, and the winch will be running at half the maximum capacity of 450kg. If the dingy gets swamped and is full of water you will want that extra load capacity. Just remember- "Sailors are optimists until poor planning fails to fill the sails, then they become fishermen with the long stories about the one that got away."

http://www.westmarine.com/circuit-breakers

http://www.westmarine.com/buy/blue-sea-systems--push-button-reset-only-thermal-circuit-breakers--P006557607

Good Luck, Old Salt

A few other types of cords that would also be suitable are: SOOW; SJOW, SJOOW; and STOW. There are several others but these are a few of the most readily available and with cords near the number of conductors and wire sizes you are looking for. Shop around if you can. Include the Internet in your search, many good bargains there.

Good Luck, Old Salt

The run from the battery to the winch is of about 4 meters. According to a chart, it will require a 0 AWG (50 mm2) cable if going for full capacity (900 kg), or a #8 (25 mm2) cable if going for half (450 kg) capacity. Does this seem reasonable?

As I cannot get the circuit breakers you mentioned locally (nor import them), I will use a Perko battery switch + an accordingly rated "slow blow" fuse to replace the thermal circuit breaker I can´t get.

http://www.perko.com/catalog/category/battery_switches/product/150/

What I also figured out is that I also may use some physics, like a set of blocks on the cable, in order to reduce the force (hence, the amps) needed to lift the dinghy.

The most accurate method to determine the maximum load you will encounter is to calculate the weights of the boat, the motor and full fuel tank, and the boat completely full of water. This is the worst case scenario where the boat has swamped and you want to lift it onto the deck. You don't state what the size and configuration of the boat is so I can't give you a good estimate on the max capacity needed. Assuming that the internal capacity is the same as the weight of the boat, 200kg boat and 200li water the gross weight is 400kg.

The 40 amp rating is only the standard for up to 300v and the wire cross section. There is no practical harm in pulling 50 amps for a short time (less than a minute). The current can be raised some more since the run is only 4 meters for a total of actual wire of 8 meters. I would feel confident in lifting 550 kg for a minute or two. This would require a larger circuit breaker or fuse than the 40 amp.

PERKO is a great brand but fuses are less reliable and can go wrong more than circuit breakers. Also battery switches are not intended to make or break the current while under load except in emergencies. Keep on looking for the circuit breaker. Fuses corrode, get wet, get lost, and are hard to see in a rough sea with only the moon for light. They are especially good if you are going to occasionally overload the winch, just up one current level for that lift.

If you look at the life boats on ocean liners you will only see one or two lines going from a block on the boat to the liner's lifeboat davits. Anything more than that and they will tangle, especially natural or synthetic rope, have several pinch points and unless they have extra weights they tend to flop over with the hook upward. They remedy that by using a one part wire rope or at the most a two part wire rope setup and a larger winch. This also reduces the deployment time. Life boats are made to be great going down, not going up. Personally, I would forget the block and tackle rigging. The gross load of the boat is well within the half capacity of the winch, use it and not the more complicated block and tackle. By the time you bought the extra blocks, lines, connectors, etc. you would have spent more than setting the winch system up for a higher electrical load. Also it is very difficult to use two block and tackles at the same time, especially lifting. Imagine doing that with a following sea!

Try harder looking for the circuit breaker of some type. I think that there must be some supplier everywhere that has them in stock or can order it for you. They have many more advantages over the fuse.

My personal choice would be: a 6 meter length of #8-2 SJOOW or other similar cord connected to the winch; a master power toggle switch, rated at least for 40 amps; a spring loaded on-off-on DPDT center off operating switch of 40 amps or more to raise and lower the boat; some good nylon line or a stainless steel wire rope; and a big smile on my face each time it works perfectly and all I had to do was put a few ounces of pressure on the toggle handle switch. I have been a sailor since I was about 6 years old and have seen similar rigs. It is also how I rigged one of my previous sailboats for a dingy.

If you decide to go with the maximum capacity of 900kg, use #3-2 cable. #3 is rated at 85 amps, #2 @ 95amps and #1 @ 110 amps. A much bigger price tag for something you will never use. What would happen weight and healing wise if you added another 900kg to the boat lifting the smaller boat, sink maybe?

Good Luck, Old Salt

Thanks for your thorough reply! I too have been sailing for many years( mainly in the Rio de la Plata), but as my wife does not enjoy sailboats, I have sold mine and went for a 40 years old 55´twin engine steel trawler, which is under restoration now. As there is a lot of work to be done and boats demand more money than a French mistress, I have to be very careful when planning each new work in order to stay within reasonable budget limits. I added a 6 meter mast and boom to the boat (just for aesthetic reasons). To justify the $ spent in the mast and rigging I will use the boom to do the lifting of the dinghy (perhaps only a couple of times a year). Dinghy will mainly be used to get the dog ashore for a pee . Should one day things get hairy, requiring to use the dinghy (it´s actually a 3 meter AVON inflatable with a 10 HP engine) as a life raft, I just have to drop it overboard.

You don't say much about the mast and boom but make sure the gooseneck can handle the additional weight of the dingy on the boom. If the mainsail is gaff rigged make sure your halyard is strong enough for the additional load, same for marconi rigged. Are the stays and struts strong enough, especially when rotating the boom from alongside to over the deck or cockpit?

Also, I would suggest that if the dingy ever becomes swamped and full of water, you should lift it from the transom only or with a slack painter on the bow of the dingy. That way you will not be lifting any substantial amount of water. As the transom, with the motor, rises the dingy tilts with the bow down. This will spill out the water over the bow as it is initially raised. By the time you get the dingy up to the boom by the transom, the dingy will be empty of water. Lift up on the bow painter and the dingy is ready to swing over the boat.

If you haven't yet, I suggest you get a copy of "Chapman's Piloting Seamanship and Small Boat Handling". It discusses this type of situation quite thoroughly.

Good Luck, Old Salt

There is a description of the mast below. The boat will have no sails, except a small one just to control rolling in heavy seas; meaning it will be seldomly used.

About Chapman´s great book: let me tell you it has been my bible since I started sailing many years ago! :-)

I always like to over-engineer everything that may be critical at some time in the future...I can think of any number of scenarios when the full capacity of the winch would be a lifesaver...and we can't be talking that much difference in cost, besides, it's a boat, why did you get it if not to pour every extra penny you have into it ....

As far as cable goes, depending on the length of the run, I'd land in the middle with 40 AMP cable.

old salt always gives great advice and he does this time, too.

Here's a little help: Voltage Drop Calculator to figure the loss for your particular distance.

I agree that welding cable is not necessary for an installation that never moves around.

Also, one more thing to consider.

Winches generate their maximum pulling power with an empty cable spool. As the cable winds onto the spool the power required to lift the same amount of weight increases. The effective ratio (pulling power) of the winch decreases with the larger spool diameter. Maybe a small point, but I expect that most winches are rated with little on no cable on the spool.

I am not disagreeing with you (not smart enough), but the instructions leaflet says the contrary: amp drawing is maximum at full load, while 1/10th running empty. From my empyrical point of view what the chinese guy says also seems more reasonable to me: the higher the resistance to move, the more energy is required to put it in motion.

Maximum full load is the fullest load of the motor on the winch. The least current drawn when lifting the maximum weight load is when the radius of the cable on the drum is at the smallest. This is the point of greatest mechanical advantage and for this reason the motor current draw is the lowest. Example: with a 4" drum with one half a layer of wire on it is the point of lowest current draw. With a 6" radius for the cable on the drum the weight of the load stays the same. The electrical load of the motor is much higher since the motor must do more work to keep the drum rotating at the same rotational speed. Since the radius increases with the amount cable on the drum the motor must work harder to lift at the greater linear speed of the cable

Theoretically if the circumference of the wire on the drum is doubled, twice the mechanical power is required to lift the same weight load. The wire is being lifted at twice the speed of that of the smaller circumference.

If the drum rotates at the same speed and at the same radius of wire, the heavier the load is, the greater the power required to lift the load weight at the same speed.

Increase in current is due to: heavier load; greater radius; and greater drum rotational speed. Decrease in current is due to: lighter load weight; smaller diameter; and slower rotational speed.

Good Luck, Old Salt

We don't disagree, in theory or practice.

I think we are saying the same thing, only differently.

The difference is, with a full spool, there is more resistance to move the load.

Look at an imaginary cross section of an empty spool and a full spool's diameter.

Then consider the different rations involved if it were gears.

It is not a significant difference, but a difference, none the less.

This explains it better. Disregard the fact the there is no water.............................

What Most People Don't Know About Winching

Interesting link. Thank you!

That makes the ratings really easy...and universal!

You could have a reserve single block on the central lift point of the dinghy. I assume you've some sort of multi-point lifting arrangement capable of handle large shifts of weight in the dinghy due to a few dozen gallons of water sloshing around. Do some testing, without the motor and gas tank, but with 100kg of water sloshing. Will you be hoisting over the side, or the stern? Is the mast backstayed enough to take three or four times the weight of the dinghy full of water? Shrouds need to handle possible boom flopping with 300 kg of dinghy+load. (For every big boat there's a bigger wave). Fittings on that boom and mast need to anticipate how useful such a rig is for moving engines, supplies, etc. You may need to use the dinghy as an emergency lift for injured-man-overboard situations. Been there, done that.

The mast is placed at midship and weight will be hoisted over the sides. I am just finishing the construction of the mast & the boom, where I plan to place a single block to help in the maneuvering. The base of the mast will be fixed to the floor of the stern deck and laterally @ 2/3 of it´s height to the roof of the wheelhouse. Two shrouds (one per side) will be attached to the mast´s top running down and forwards forming a " V " ending at chainplates to be fixed laterally to the sides of the wheelhouse. As the freeboard of the boat is of about 2 meters, lifting weigh will have a certain complexity. Therefore I am planning to do a series of tests under different conditions (of the load and the river, at my own and with assistance) as soon as the boat get´s back to the water in some months, being aware it will require a lot of fine tuning before everything runs smooth....

Can I suggest that you raise the location of the upper shroud to higher on the mast. This will increase the "off the side" capacity and lessen the strain on the mast. Also connect the forestay up the mast as high as you can. This is critical while you are holding or lowering the dingy over the cockpit or stern deck. When this is all completed fine tune the stays to even loads. A frequency meter while strumming them like a guitar string can be used for the most accuracy.

A look at old pictures of old sail powered freighters might be worth some ideas. They loaded and unloaded by the boom. Some old ideas are still good ideas.

Good Luck, Old Salt

Because you are rigging a boat, the wiring must comply with the Code of Federal Regulations (CFR) chapter 183, subpart I - Electrical Systems, or you can reference American Boating and Yacht Council (ABYC) section E - 11, or National Marine Manufactures Association (NMMA) - Electrical.

Compliance is in your best interest regardless of other wire size guidelines or practices.

Chuck

Do you mean 33 CFR chapter 183 Subpart I, Electrical Systems? 33 CFR is for Navigation and Navigable Waters (sometimes referred to as "The Coast Guard Section").

http://www.gpo.gov/fdsys/pkg/CFR-2010-title33-vol2/pdf/CFR-2010-title33-vol2-part183-subpartI.pdf

Good Luck, Old Salt

I have read this doc some time ago, but it is written for gasoline engine boats, and specifications are therefore (I guess) stricter than they would be for diesel engines. Do you know if there is a version for such engines?

I have done a complete search of 33 CFR and did not find anything similar for diesel powered boats. As you say, this is for gasoline inboards only:

183.401 Purpose, applicability, and effective dates

(a) This subpart applies to all boats that have gasoline engines, except outboard engines, for electrical generation, mechanical power, or propulsion.

I also searched the same 33 CFR for "diesel" and found nothing related to this. Most, if not all, of the references to diesel were for the transportation of large quantities such as barges, tankers and such. It was also for the storage of diesel fuel and similar products in areas that are subject to maintaining an "Coast Guard Operations Manual" for their facility.

http://www.gpo.gov/fdsys/pkg/CFR-2010-title33-vol2/pdf/CFR-2010-title33-vol2-part183-subpartI.pdf

Good Luck, Old Salt

Its ok to use the 25A cable since you will never hoist more than that but just for added safety as is your concern, include a 30A fuse in the circuit and you will be home and dry

Let me get this straight...

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You are recommending installing a length of cable that will be rated for the estimated maximum load, while the maximum current draw of the winch could be more than 3 1/2 times greater.....and just for safety sake, you suggest installing a fuse would allow 120% of the current for which the cable is rated to flow???

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"...and you will be home and dry..."

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Is that a metaphor for shedding the mortal coil? Or are you predicting 'home and dry' with the more optimistic view, that he would not perish in the fire and would be 'home and dry' because where else would he be since his boat burned down?

And then happy fire fighting!

25 A for 227 kg load? most surprising winch. Is it most inefficient winch? for a hoist of 250 kg you need not more than 5 A. I recommend maximum size of copper cable of 4mm sq. Please recheck the Amps for 250 kg load and then decide.

Hello! thank you for your input, but I must say that instead of sheding light over the issue, it contradicts all the previous opinions, getting me more confused! Can you please explain your point of view?

Thks

I have worked with hoist mfr for 33 years. We had 250 kg hoist which while testing would draw maximum current of 4-5 Amp. How come your winch mfr is specifying current of 25 Amps there must be some confusion. Better refer to local hoist mfr and show the results to your winch mfr and ask him to clarify.

Possible if the winch is really slow.

According to the specs, speeds are: 3.1 meters / min for 230 kg - 2.6 meters/min for 454 kg, and 1.1 meters/min fro 900 Kg. But I don´t know if this is really slow ... or not