Sail winch arm

I am planning on using the Hitec 815 sail arm, it only travel 140deg’s. so my question is what arm length do I need to sheet the sail in all the way? I wouls assume it is the length from the sheeting post to the boom, right? so what is that average length. I picked the 815 due to the cost as I do not race and maybe sail 4 times a year.


the length of travel you need is from full in to full out, measure this on the sheet rope.
Tahe sail arm length is not critical, you can obtain the correct length of travel by using a fixed point to start the sheet, ie fix the sheet to the boat and run in through a pulley on the arm, you will have to work out the fixed point to give you the correct lenght of travel reqired.

Take a look at the following link !

Alternatively i have just bought a Hitec HS-785 HB sail winch for about the same money, which I hope will do the same job, although it does not have as much torque.

let me know how you get on!

ps you nee to get out and sail more, like every week:D


Hahahaha about getting out once a week, I am the father of three active little boys so this will get us out more once I get for IOM’s built (working on #2) I have the sail winch on my triple crown and it works good, just thought I would try something else with the 815. I will try to keep posted on how things work as I am waiting to open my Christmas present from my wife before installing it. The area I live has frozen water now so this is when the building goes on.


Well I read the link provided and I am confused, arm radius is 90mm, 80mm for pully, then it says 260mm for sheet travel? this is what I have a problem with how do you get 260 sheet travel? I ask about arm length as I am limited by width of boat?

Let’s assume you need 260mm. If you have an arm put it on the servo. If not cobble something up by clamping a piece of wood to whatever servo horn you have. Rotate the servo fully CW. Turn it upside down on a piece of paper and mark the paper at the furthest hole in the arm. Rotate the servo fully CCW (trying not to move the servo) and mark the the same hole. Measure between the two points. Is it more than 260mm? You need a shorter arm. Is it less than 260, you need a longer arm. Clamp a piece of wood to the arm and keep working your way out until you have 260mm. If the arm gets to be too long you can hang a block on the end of the arm, anchor the sheet to the hull and double the travel. This allows you to shorten the arm by half.
This is probably not clear, I don’t express myself well, but it may help. If not ask again and I’ll take another shot.

Don I was figuring out the arm length with a protractor ( trying to remember high school math) but I for got that if you put a block down tha tyou double the length. Thank you