winch for rib, what is the calculation for the approx weight up a slope?

Hugh Jardon · 05 September 2006, 20:30

I am thinking of getting an electric winch fitted for lowering and raising the rib up and down slipways.

I have seen a few winchs around on the web but wanted to see if others recommend a particular sort of winch or ones to steer clear of

my boat and trailer weighs at most 1800 kg but probably nearer 1500kg lets say
I am not sure what the average gradiant is on a slipway, but i wanted to calculate the approximate load on a winch if pulling the boat and trailer up an average slipway. At a guess i would expect the average slipway is between 10 and 40 degrees.

does anyone out there have a rough calculation that shows what effort or equivilent weight a 1800 kg boat and trailer would be when being dragged up a 10 20 30 and 40 degree slope

not sure what cooefficient of drag to use for the wheels but i suspect it should be minimal

schoooooooooooool seems to have been a long time ago and i think i bunked off this lesson

any guidance from experts out there would be appreciated

i am trying to gauge what size winch is suitable and calculate the winch speed at different loads to determine the suitable item
here is one i have found so far which would easily do the job i suspect

http://www.winchdirect.co.uk/dv-9000.htm

Limey Linda · 05 September 2006, 20:47

The winch you have looked at is designed for the front of a 4x4. It is probably overkill in terms of power and cost. It is a worm drive and very slow. A spur gear winch should do the job at half the cost. A general guide line: calculate 50% of the laden weight of the boat ( including fuel etc. ) choose a winch close to that figure and then go to the next size up. For your boat you are going to need one with a steel cable, not strap/rope. I would guess 2500-3500 lbs. will be suitable. If your are not worried about speed, but want more power then replace your existing winch with a 2 speed manual one. Remember you will have to rewire your vehicle to get enough electric power to the tow hitch area for an electric winch. Hope this helps.

Colin F · 05 September 2006, 20:56

AFAIK....

10 degree slope = 313Kg
20 degree slope = 616kg
30 degree slope = 900kg
40 degree slope = 1157kg

please remeber school was a while ago

i did test the figures with a 89 degree slope and it came out as 1799.7kg so i am fairly confident

BogMonster · 05 September 2006, 21:56

Ignore all ratings for electric winches if you need to pull the thing any distance. A 9000lb electric winch will pull 9000lb for a very short time before getting hot and bothered and the same will be true of little ones. A 4500lb Land Rover needs a 9000lb electric winch for any sort of reasonable reserve capacity. This is the reason why I have a hydraulic winch on mine, because with those you get what it says on the tin, 10500lb all day long if you want it not for 2 minutes before something goes pop.

The general rule of thumb is take the weight you are pulling and double it.

Hugh Jardon · 05 September 2006, 22:22

thanks for the posts so far, got me thinking as to which to use. will fit the winch on the back of the MH as i dont fancy reversing this down some slipways!

Limey Linda · 05 September 2006, 23:31

Quote:

Originally Posted by BogMonster

Ignore all ratings for electric winches if you need to pull the thing any distance. A 9000lb electric winch will pull 9000lb for a very short time before getting hot and bothered and the same will be true of little ones. A 4500lb Land Rover needs a 9000lb electric winch for any sort of reasonable reserve capacity. This is the reason why I have a hydraulic winch on mine, because with those you get what it says on the tin, 10500lb all day long if you want it not for 2 minutes before something goes pop.

The general rule of thumb is take the weight you are pulling and double it.

Steven, you are talking about hauling vehicles out of holes, not winching a boat onto a roller trailer. Been there done that. Think you are more than a little off base here. Regards, T.

Poly · 05 September 2006, 23:37

Quote:

Originally Posted by Limey Linda

Steven, you are talking about hauling vehicles out of holes, not winching a boat onto a roller trailer. Been there done that. Think you are more than a little off base here. Regards, T.

Hugh is not talking about getting the boat on the trailer he is talking about parking his "bus" at the top of the slipway (ramp to you lot) and pulling the boat and trailer up the slipway.

Hightower · 06 September 2006, 00:03

You'd be better off using a good sturdy peice of rope for that job, and it's cheaper than a winch.

Limey Linda · 06 September 2006, 00:04

I agree, certainly a "different kettle of fish" However same principles apply but maybe a lower powered winch ?? as trailer has nice round wheels. However, if the MH is at the top of the ramp/slip and you use any winch to get the boat trailer up it's arse end. What do you do then? Perhaps chock the trailer and reverse the MH back to hook up. Seems complicated to me.

codprawn · 06 September 2006, 00:37

Whilst on the subject. What happens to the jockey wheel on the trailer when winching? The wheel isn't really designed for anything other than keeping the trailer nose at the right height for the tow vehicle to connect to - isn't it???

Hightower · 06 September 2006, 00:47

Quote:

Originally Posted by codprawn

Whilst on the subject. What happens to the jockey wheel on the trailer when winching? The wheel isn't really designed for anything other than keeping the trailer nose at the right height for the tow vehicle to connect to - isn't it???

I'll tell you what happens Codprawn......It starts to shout and cry and scream and then dies

.

You can get HD jockey wheels with grooves up the shaft and have once seen a stratigically placed spare wheel on a spare hub used to pull trailer up the hill before reverting back to the jockey.

Limey Linda · 06 September 2006, 00:52

Good point Codders. However, you could replace the jockey with a pair of inflated wheelbarrow type wheels. I agree a standard jockey wheel is likely to bust off if it hits a stone or a crevice on the slip.

BogMonster · 06 September 2006, 05:03

Quote:

Originally Posted by Limey Linda

Steven, you are talking about hauling vehicles out of holes, not winching a boat onto a roller trailer. Been there done that. Think you are more than a little off base here. Regards, T.

Not at all off base T, I shall elaborate

Electric winches are almost without exception vastly over-rated by their manufacturers whether you are talking about pulling a vehicle out of a hole, winching a kettle of fish up a telegraph pole (why do people keep fish in kettles anyway?), or anything else. I used to have an interesting video made by Milemarker (a hydraulic winch manufacturer) which shows the MM hydraulic winch, and two electric ones of a similar capacity, each pulling half their rated load along a flat surface (load measured on a strain gauge or whatever you call it). One of the electrics (Superwinch 9000) overloaded after just 2 feet and the other (Warn 8274) lasted just 25 feet before it cried enough - at HALF the rated capacity. Naturally the Milemarker pulled the load the full 100 feet of cable with no problem. A hydraulic winch would be overkill for this application IMHO, but neither do you want a winch that shifts the boat 2 feet and goes pop!

I was in a hurry to go out; what I meant to say in my original post was whatever the calculation tells you is required (e.g. a pull of 900kg on a 30 deg slope, in the above figures) double it, rather than using the weight of the boat. A 900kg capacity electric winch would struggle to pull 900kg for very long, while an 1800kg one would do a much better job of it and is what I would consider a minimum - you wouldn't need a full size 4x4 winch for this job. You can get into all sorts of calculations about "mire depth" on a 4x4 which means you can need anything up to 3 times the pull of the vehicle's weight to shift it (hence the requirement for snatch blocks to give a double or triple line pull on a 4x4 winch that should shift the vehicle easily), but quite rightly, that is not relevant to a boat on a smooth slipway as it is a steady rolling load.

Apart from the load capacity there is another issue which is speed - most if not all electric winches operating near their rated load capacity are painfully slow. Bigger winch = faster.

I also know somebody with a spare wheel fitted on a hub welded to the trailer drawbar. It was on the trailer of the Wildcat I nearly bought instead of my Humber, and the guy lets the trailer roll into the water on the end of about 10 feet of rope instead of getting his vehicle wet. I have watched him do this and it seems to work well, and I am going to do something similar at some point because my jockey wheel is about to break off the trailer. It also means that the trailer rolls back dead straight, which it might not do on a jockey wheel, and that you can launch it on a rough slipway. He also has quite a neat trick which is to tie the boat's bow eye to the trailer using about 15 feet of rope, let the trailer roll in to the water then stop it suddenly by tapping the brakes on his Land Rover, boat rolls/floats off trailer, pull out trailer on the end of rope which brings boat in to shoreline, hop aboard, off you go

BogMonster · 06 September 2006, 05:09

This might be worth a look Hugh - Goodwinch website

David Bowyer is the UK distributor for Superwinch stuff as well as making his own range of Goodwinch ones. I think they probably do the full range, if you look in the "small winches" section and download the PDF it has some suitable ones, or he has bigger ones in the 4x4 range. Just one thing to make sure: get one with a freespool (allows you to pull the cable out by hand rather than powering it out) as it is a PITA if it doesn't have this!

bedajim · 06 September 2006, 06:10

Will the new motor home have hydraulic levelling = hydraulic circuit you may be able to power the winch from with some pump mods

On our sailing boat we use a 10" pneumatic dinghy launching trolley wheel at the front when launching, no bearings, keeps the trailer straight and will run on uneven ground

James

Richard B · 06 September 2006, 06:16

Quote:

Originally Posted by BogMonster

why do people keep fish in kettles anyway?

They don't, they just cook 'em in kettles!

http://www.cookware-online.co.uk/ish...hopscr317.html

MarkM · 06 September 2006, 07:14

I use the Power Winch ST 712 with a strap. Very comfortable. Before I used a winch with a steel cable. That's no use.
My boat is something like 2000kg incl. load. And it works out fine even on a steep slope. I use a Defender 110 and have the engine running while pulling the boat in. No problems whatsoever. It cost me a battery before, with the engine of the car turned off.

Jono · 06 September 2006, 07:20

Quote:

Originally Posted by BogMonster

......which shows the MM hydraulic winch, and two electric ones of a similar capacity, each pulling half their rated load along a flat surface (load measured on a strain gauge or whatever you call it). One of the electrics (Superwinch 9000) overloaded after just 2 feet and the other (Warn 8274) lasted just 25 feet before it cried enough - at HALF the rated capacity. Naturally the Milemarker pulled the load the full 100 feet of cable with no problem. A hydraulic winch would be overkill for this application IMHO, but neither do you want a winch that shifts the boat 2 feet and goes pop!

...now try the same test with a dead engine....

No help whatsoever.. but here's a good set up. "Hand Friendly" rope and not wire...

bedajim · 06 September 2006, 07:48

[QUOTE=Jono] ...now try the same test with a dead engine....

So why would you want to winch your boat/trailer onto a car with a dead engine at the top of the slip

Jono · 06 September 2006, 08:00

Quote:

Originally Posted by bedajim

[....
So why would you want to winch your boat/trailer onto a car with a dead engine at the top of the slip

I was just having a little dig at the "un-biased" test being described. Believe me an electric winch will be perfectly capable of doing the job in question...