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