Winch Size?

[thedukeryan]

While coming in on Sunday I hear what sounded like a branch breaking. I was sure I just ran over something but when I stopped to look I found that my winch strap completely snapped. It was a brand new 1200# winch. My boat is a 23' Wellcraft Eclipse which I believe weights in at roughly 4000# maybe pushing 5000 when FULLY loaded. Is my problem a undersized winch, poorly built wench or both. It was a SeaSense 1200# winch with a 4:1 ratio if that helps.

 

[salty87]

Re: Winch Size?

you say the winch was new, how old was the strap? they only last a few seasons before getting brittle.

 

[thedukeryan]

Re: Winch Size?

The winch was NEW maybe a month old at most. The previous winch was 1000# but was was pretty worn out so I replaced it.

 

[dingbat]

Re: Winch Size?

Who the heck put a #1200 winch on a #4000 boat trailer?

My boat weighs in right around #5000 with fuel. I have a #4200 electric winch that struggles to pull the boat on the triailer if I'm loaded up fuel. Should have gotten the #6K capacity instead

Can't see using anything less than a #3200 winch on your boat.

 

[thedukeryan]

Re: Winch Size?

The only winch I could find on a weekend locally was the 1200lb one. Figured it had a 1000lb winch on it for who knows how long with no problems. I usually drive the boat up onto the trailer and then just tighten it up with the winch. Even when not driving it up I have never had a problem winching it in. Even my gf who is much smaller than me just cranks it in usually with no problems. Damn thing just snapped while cruising down the road. Was thinking about getting a electric but if your 4200# winch struggles pulling in a 5000# boat I will probably stay with a manual.

 

[skargo]

Re: Winch Size?

I was told to get at least a winch rated for half the weight of the boat, wet and fully loaded. I hope that is a safe, and correct assumption?

 

[thedukeryan]

Re: Winch Size?

That is what I am thinking. I did some more looking and am guessing that mine weighs in closer to 4500 loaded. I think I will try to find one in the 2500 range. Just is frustrating not having a decent selection locally. Maybe its just me but it still strikes me as odd that it snapped so easy. I realize that I was under sized but I thought even a 1200# one would at least hold on with the boat tied down. Good thing I had it chained up.

 

[dingbat]

Re: Winch Size?

I was told to get at least a winch rated for half the weight of the boat, wet and fully loaded. I hope that is a safe, and correct assumption?

Yes and no. The problem is in the way the winches are rated.

Most winches are rated at the drum. Meaning that the load calculation (Force x radius) is based on the diameter of the winch drum without the strap.

Add a full length of strap to the drum and you've increased the working diameter of the winch and thus the load. A change is drum diameter from 1" to 3" will increase the load on your winch by a factor of 3

In my case my boat weighs roughly #5000. Going by your ? weigh method I need a winch capable of pulling #2500 lbs. Sound reasonable but lets do the math.

My winch is rated #4200 lbs at the drum. With an empty drum it pulls my boat without breaking a sweat. Winding 8-10 feet of cable on the drum increases the effective diameter by roughly 2". This increase in effective drum diameter causes the load on the winch to be increased #2500 to #5000 lbs (#2500 x 2?R) .

So much for the 1/2 the weight = winch size theory.

 

[thedukeryan]

Re: Winch Size?

My main concern is finding one that isn't going to snap on me. I am not to concerned with it having enough muscle to pull it on. I figure if we got by fine with a 1000# winch then we should be fine with a 2500lb one. I just don't wanna deal with it snapping again.

 

[skargo]

Re: Winch Size?

Yes and no. The problem is in the way the winches are rated.

Most winches are rated at the drum. Meaning that the load calculation (Force x radius) is based on the diameter of the winch drum without the strap.

Add a full length of strap to the drum and you've increased the working diameter of the winch and thus the load. A change is drum diameter from 1" to 3" will increase the load on your winch by a factor of 3

In my case my boat weighs roughly #5000. Going by your ? weigh method I need a winch capable of pulling #2500 lbs. Sound reasonable but lets do the math.

My winch is rated #4200 lbs at the drum. With an empty drum it pulls my boat without breaking a sweat. Winding 8-10 feet of cable on the drum increases the effective diameter by roughly 2". This increase in effective drum diameter causes the load on the winch to be increased #2500 to #5000 lbs (#2500 x 2?R) .

So much for the 1/2 the weight = winch size theory.

Gotcha. Seems the manufacturers need to step up and make some higher rated winches.

 

[Bifflefan]

Re: Winch Size?

I just got a new 2000# winch for my 16' starcraft.
Im a firm beliver in go twice as big then you dont have to worry.

As a rule of thumb, you must over come 1/3 of the weight to move it on flat ground. So in other words, if it weighs 3000lbs then you must move 1000lbs to get it to move on flat ground.

 

[skargo]

Re: Winch Size?

I just got a new 2000# winch for my 16' starcraft.
Im a firm beliver in go twice as big then you dont have to worry.

As a rule of thumb, you must over come 1/3 of the weight to move it on flat ground. So in other words, if it weighs 3000lbs then you must move 1000lbs to get it to move on flat ground.

What about flat water?

On my offroad rig my winch is at least 2x the weight of my crawler, way more if I use a snatch block and double the line. I've been using that kind of reasoning, and figuring a floating boat, or a boat dragging on wet bunks, or rollers, would offer a lot less weight resistance than if you were pulling the straight weight, know what I mean?

 

[jjc917]

Re: Winch Size?

1/2 the loaded weight of your boat for easy launching and very small grade hills when towing, less than 10% grade not 10 degree incline they are different.

3/4 of weight for steep launches and steep grade towing.

Winches ratings as well as straps and hooks are rated while lifting straight up, which you are not doing. The amount of load decreases as the grade decreases.

My boat a 20', 2700 lb dry weight, loaded at 3000, requires minimally a 2250 lb rated winch, 0.75 x 3000 = 2250, again this is minimal.

So for 4500 lb loaded x 0.75 = 3375 lb minimally.

Thats just on the winch itself, now the strap/cable should be rated at least 1.25 x the rating of the winch. You said the strap broke and not the winch which sounds like the strap may have been under rated. I also believe your 1200 lb winch is way under what you should have.

This is basic physics, Im a Math/Physics grad and did the calculations. There are also a few good sources...

Heres one that talks about line "wrap" and how it increases the load...

http://www.superwinch.com/Trailer_Winch_Selection.html

Its rerally basic physics, Im new to boating but am a math/physics grad student...

 

[skargo]

Re: Winch Size?

Grades while towing?

 

[jjc917]

Re: Winch Size?

Height divided by length, basically how steep a hill is, old geometry aka rise or run...Click the link and it explains it fairly well.

 

[dingbat]

Re: Winch Size?

This is basic physics, Im a Math/Physics grad and did the calculations. There are also a few good sources...

What did you use for a friction coefficient?

 

[soaringhiggy]

Re: Winch Size?

it would depend on what the action on the boat was. If at rest on the bunk and then needed to be moved forward you would have to use μS, if the boat is being moved up the trailer and already in motion you would use dynamic friction μD, but it gets more complicated from there

I like extra capacity in most tools, especially when energy is involved. Working on the edge of capacity, well things go wrong, with more energy they go wrong quicker and are more spectacular.

 

[JoLin]

Re: Winch Size?

Glad I read this thread. I've been debating what size Powerwinch to get for my boat (about 6000 lbs fully loaded). Their RC23 model is rated for up to a 7500 lb boat, the RC30 for up to 11,000 lbs of boat.

I decided to pay the extra $40. for the heavier model and ordered it last night. I don't see any downside to being overcapacitized here, but I sure don't need the winch "stalling" under that heavy a load.

 

[dingbat]

Re: Winch Size?

it would depend on what the action on the boat was. If at rest on the bunk and then needed to be moved forward you would have to use μS, if the boat is being moved up the trailer and already in motion you would use dynamic friction μD, but it gets more complicated from there

It gets a bit more complicated, but you might be surprised.

 

[jjc917]

Re: Winch Size?

What did you use for a friction coefficient?

LOL, um static until it "breaks" loose and then kinetic....any other smart a#$ questions...LOL just kidding though