Winch numbers nonsense.

[Gary Fox]

Yacht winches should be described by the diameter of the drum, first. Not some arbitrary made-up convention like Lewmar 40. 40 what? Inches? Millimetres? Furlongs? It is deliberately confusing. Nobody seriously uses the obsolete Thames Measurement and similar obfuscations today, just tell me the damn dimensions.
When we have got over that seemingly insurmountable hurdle of clarity, then we can move on to bronze or inox, self-tailing or not, 2-speed etc.
WHY?

 

[dom]

It’s certainly obscure but summarised here - and we all sort of recognise the nomenclature by now:

What do the numbers mean on winches? Why are they so different to my old winches

 

[Roberto]

Power ratio, speed ratio...

 

[capnsensible]

Great rant though. ??

 

[GrahamD]

Power ratio. Assuming a standard length winch handle, a 40 winch would deliver 400kg of pull when 10kg applied to the handle.

 

[geem]

Yacht winches should be described by the diameter of the drum, first. Not some arbitrary made-up convention like Lewmar 40. 40 what? Inches? Millimetres? Furlongs? It is deliberately confusing. Nobody seriously uses the obsolete Thames Measurement and similar obfuscations today, just tell me the damn dimensions.
When we have got over that seemingly insurmountable hurdle of clarity, then we can move on to bronze or inox, self-tailing or not, 2-speed etc.
WHY?

If you did that you might buy a nice fat winch with no power. We used to have some nice fat winches that did just that. Now swapped put for Lewmar 58s.

 

[Gary Fox]

If you did that you might buy a nice fat winch with no power. We used to have some nice fat winches that did just that. Now swapped put for Lewmar 58s.

Ok I understand that. Thank you all for the answers. So what I want to know first is:

1. Drum diameter.
2. Gear ratio. (s)

For example, '100mm 1:10'. If you had known those figures, geem, would it have helped you to get the right winches first time?

 

[GrahamD]

Ok I understand that. Thank you all for the answers. So what I want to know first is:

1. Drum diameter.
2. Gear ratio. (s)

For example, '100mm 1:10'. If you had known those figures, geem, would it have helped you to get the right winches first time?

You need to know first the typical max working load to which the winch will be subjected, ( This obviously has to be below the designed Maximum Working Load of the winch) There is no point in fitting a winch that will break.

The typical max working load depends on factors such a the size and type of the sail, the max expected wind speed and the hull type. Having established the likely working load, dividing this by the power ratio (mentioned in my previous post) gives an estimate of the pressure that you will need to exert on the winch handle, ie you find out whether you will be able to turn the handle.

There are spreadsheets that will estimate this. Harken have a useful tool on their website https://www.harken.com/uploadedImages/Product_Support/Dr_Harken_Tips/Oredering-winches_EN-lg.png. This estimates the required power ratio needed in different situations.

Once you know the required power ratio, it is only then that you look at the diameter of the drum to see if it will fit in the space on the deck and the price to see if it will fit your pocket.

 

[JumbleDuck]

Power ratio. Assuming a standard length winch handle, a 40 winch would deliver 400kg of pull when 10kg applied to the handle.

That would be force ratio. Power ratio would be just under 1.

 

[Gary Fox]

You need to know first the typical max working load to which the winch will be subjected, ( This obviously has to be below the designed Maximum Working Load of the winch) There is no point in fitting a winch that will break.

The typical max working load depends on factors such a the size and type of the sail, the max expected wind speed and the hull type. Having established the likely working load, dividing this by the power ratio (mentioned in my previous post) gives an estimate of the pressure that you will need to exert on the winch handle, ie you find out whether you will be able to turn the handle.

There are spreadsheets that will estimate this. Harken have a useful tool on their website https://www.harken.com/uploadedImages/Product_Support/Dr_Harken_Tips/Oredering-winches_EN-lg.png. This estimates the required power ratio needed in different situations.

Once you know the required power ratio, it is only then that you look at the diameter of the drum to see if it will fit in the space on the deck and the price to see if it will fit your pocket.

Many thanks!

 

[Sandy]

Unless there is an international standard every manufacturer can do whatever they want.

 

[GrahamD]

What I described is generally agreed practice, the number referring to the best power ratio available, so a Lewmar 40 is about the same as the Harken or Andersen 40. An exception was when Pontos brought out their four speed winches they decided to label their Trimmer winches conventionally, (so people would have some understanding of the physical size and maximum working load of the winch) even though the Trimmer 40’s best power ratio was actually 110:1. After Pontos went bust and the designs were bought by Karver the Trimmer 40 is now being marketed as the KPW 110. (KPW stands for Karver Power Winch);

 

[Bodach na mara]

Dear oh dear, 11 replies and no body has got the physics right yet (not even Jumblie). The number is actually the velocity ratio, VR, NOT the force ratio and certainly not power ratio, which as Jumbleduck pointed out is always a value less than one unless you are breaking the law of conservation of energy. The force multiplier is always a bit less than the VR.

The numerical values for winches have changed a lot since I was a lad. Then, quite large yachts like 8 metres used the likes of Lewmar 8CRs. So either the number system has changed or we have got weaker!

 

[GrahamD]

Dear oh dear, 11 replies and no body has got the physics right yet (not even Jumblie). The number is actually the velocity ratio, VR, NOT the force ratio and certainly not power ratio, which as Jumbleduck pointed out is always a value less than one unless you are breaking the law of conservation of energy. The force multiplier is always a bit less than the VR.

The numerical values for winches have changed a lot since I was a lad. Then, quite large yachts like 8 metres used the likes of Lewmar 8CRs. So either the number system has changed or we have got weaker!

I stand corrected. However, Power ratio is the term used by most of the people who sell and fit the winches.

 

[Gary Fox]

So is a winch's gear ratio its velocity ratio? The two terms seem to be interchangeable for simple things such as seesaws with the pivot not being in the middle.

Or, does a winch's velocity ratio include the drum radius and assumed winch handle length?

For example, a bicycle with a front sprocket, or chainwheel, half the diameter of the rear wheel sprocket would give half the speed but twice the torque, better for going uphill.
However, bikes have various different diameter rear wheels, and different length pedal cranks.
These measurements might be considered analogous (if that is the right word) to winch drum diameter and winch handle length.
I think...

 

[geem]

Ok I understand that. Thank you all for the answers. So what I want to know first is:

1. Drum diameter.
2. Gear ratio. (s)

For example, '100mm 1:10'. If you had known those figures, geem, would it have helped you to get the right winches first time?

I didnt get it wrong, the boat came with the winches. I calculated that the existing winches were equivalent to Lewmar 42. The recommendation for our boat from Lewmars charts was 58s

 

[DJE]

So is a winch's gear ratio its velocity ratio?

No. The velocity ratio is the gear ratio multiplied by the handle length and divided by the radius to the centre of the rope on the drum.

 

[Gary Fox]

No. The velocity ratio is the gear ratio multiplied by the handle length and divided by the radius to the centre of the rope on the drum.

Aha! Thanks

 

[Orion Jim]

Winch comparison reference guide.....
Winch Comparisons