My recently acquired IOM has a hitec sail winch which appears (to me) to have an exceedingly large drum attached. (4.5cm across). So much so that it sits under the deck a fraction. This makes removing the drum very difficult, as it means I have to unscrew the whole tray.

I have a smaller one (3.5 cm across). What effect will fitting the smaller drum have?

David

Hi David, I guess the most obvious effect will be that you will reduce the range of the sheet travel roughly in proportion to the reduction in diameter. I believe the important diameter measurement is on the bearing surface of the drum, not the extreme diameter. You may be able to compensate for the reduced travel by using the adjustments available on your transmitter - and maybe you can try that out fairly easily before you remove the drum?

A new winch might feel like a step too far, but there good are advantages to having a quicker winch. I have an RMG on my current boat and although it’s not the quickest it is more than adequate for club racing. The new Red Ant winches look interesting…. would be nice to hear from anyone who has one.

M

Hi Martin, I bought an old 1OM to get a cheap introduction to the class. I still don’t understand pretty much anything  about the electronics or mechanics side, except I have mastered end points on my transmitter, so I will do as you suggest and play around with that.

I don’t think it’s a very fast winch, and I would be reluctant to spend a shed load of money on a new one at this stage. I would be concerned if a smaller drum adversely affected the speed further though?

David

Hi David, Ah yes, I fully understand your points - I’ve been there too (some would say I still am!) and I’m no whiz with electronics either. But as I understand things, your current winch will turn at a certain rate (i.e. turns per second); and so a smaller drum will proportionally reduce the sheeting speed too. Have a fiddle with your transmitter - hopefully you’ll be pleasantly surprised.

Having said all of the above, removing the winch drum is not usually necessary all that often, so maybe you could just carry out whatever maintenance is required, refit the drum and carry on sailing?

M

When does the speed of the winch really matter?

IMHO it is most noticeable on the run when gybing, but if you can find a suitable technique to mitigate this then carry on using what you have and get pleasure from getting the most out of the boat. 

Thank you. You both highlight the importance of the sailing side and I must say that I’ve been astounded at how similar rc sailing and the “real thing” are. 
I suppose what I’m trying to do is ensure that, when I do launch Cygnet, everything works properly and I can enjoy the sailing (racing) without gear failure. Gradually working my way round the boat……….

David 

To a first approximation, a smaller diameter drum will reduce the travel but increase the torque by the ratio of the diameters: in this case travel will be reduced by 78% and torque increased by 30%.

If you look at your current end points you should be able to work out if the winch has enough travel (this may be the reason for the big drum).  For example if you current end points are set to 75% then they need to be increased to (75 x 1/78) = 96%. Note that many transmitters have max end points greater than 100%.

As to the speed reduction; anticipation will get you a long way but everyone gets it wrong sometimes and a fast winch can help on those occasions.  The only time a slow winch is a real issue is gybing in strong winds.  If you sheet in to promote the gybe then you need to let the sheet out fast to prevent a broach.  For a beginner / club racer there are more important things than how fast your winch is.

Sorry should have read what  I wrote before posting!  The drum size doesn't affect the servo torque of course but does affect the force on the sheet, so you need to replace 'torque' with 'sheeting force' in the above.

Thanks John. I appreciate your input and will leave drum as is and tinker. The maths certainly helps!