Masthead sheaves

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BrightStar
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Masthead sheaves

Post by BrightStar » Thu Mar 29, 2018 10:11 pm

I will be taking my mast down next week and one of the jobs is to check the masthead and base sheaves.

I am thinking of changing these to bearing sheaves - has anyone done this? If so roller or ball bearings?

As I want to get the main to drop freely I will also be inspecting, cleaning the slot.

I am also considering going down one size on the halyard, using a high quality line, again to try to get it to run more freely - any comments?
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paulbelton
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Re: Masthead sheaves

Post by paulbelton » Fri Apr 27, 2018 9:39 pm

Hi BrightStar,

Sorry I missed your post by a couple of weeks however I've recently been attempting the same in order to reduce the friction in the halyard-run on my Fulmar. At 13mm width I struggled to find ball-bearing replacement sheaves for the 90mm diameter sheaves at the masthead and 70mm diameter sheaves at the mast foot. I found Richard at Evolution Rigging (SYH) to be very helpful in discussing alternatives and reducing line sizes was a solution he also proposed. Although it's worthwhile to check the optimum line size of existing clutches and ST winches to ensure they will still operate effectively.

Simply servicing the existing sheaves and housings will do much to help the lines pass more freely, plus a squirt of Pro-Lube or similar (in the sheaves and mast track). In order to access the pin the sheaves rotate on at the masthead I had to remove the mastcap which was held in place by two large diameter nuts. Whilst daunting these came away quite easily to expose the sheave assembly and in fact it (sheaves, spacer plate & pin) literally fell apart in my hands once the cap (including housing) was prised off the top of the mast! A spare pair of hands came in useful on reassembly.

Richard also suggested identifying 'sticking' points in the system by hoisting the sail without sliders to see if they contributed to the problem. One could also try hoisting/dropping the sail from the mast to eliminate the deck hardware as numerous organisers, bulls-eyes and blocks will inevitably slow down the halyard, as will sharp angles in the route from mast to winch. Going back to sliders, we have a couple of cars that engage in the mast track that carry the luff-end of full-width battens, these can exert more friction on the track than the more common white plastic T-shape ones, I don't know whether you are similarly affected? He also mentioned the dreaded halyard-wrap which is a pain to diagnose and even harder to cure.

From what I could find available on the market, you would have to mount external ball-bearing blocks and reroute halyards through these, however I'd be interested to hear how you got on and what option you went for in the end. See you out on the river!
Paul
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Re: Masthead sheaves

Post by BrightStar » Fri Apr 27, 2018 10:34 pm

Like you I couldnt find suitable roller bearing sheaves so I took the mast head off and stripped the sheaves and their axles, the whole arrangement was gunged up with lots of crud n the divider plates.. the whole lot was reassembled with lots of grease.

I stayed with 10mm halyards, being advised that 8mm were marginal unless I went for Dynamee which wasnt in the budget, the 10mm stretching less than the 8mm under the same load.

I cleaned and polished the mast groove, I have two wheeled cars and the rest are plastic plugs, all of which had lots of wax worked in.

I also have a downhaul which is attached to he headboard to help with the doenward motion, the halyard route has the minimum of blocks and turns getting it back to the cockpit.

Brightstar was launched today so waiting for a wind friendly day to get he sails on and try.

I will keep an eye out for you on the river, where are you berthed, I am at RHYC marina
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Re: Masthead sheaves

Post by paulbelton » Sat Apr 28, 2018 5:41 pm

It sounds like we have a similar set up, apart from the headboard downhaul, do you have this routed back to the cockpit too?

Glad to hear you are back in the water, I hope all went smoothly yesterday. We're booked to relaunch in a couple of weeks from OYC so will do likewise and keep an eye out for you on the river.
Paul
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Re: Masthead sheaves

Post by BrightStar » Sat Apr 28, 2018 8:15 pm

Yes I have everything back to the cockpit including the single line reefing. The downhaul is quite effective, usually a sharp jerk gets the main on its way down, need to be careful that it is free running during the hoist.

Yes it will be good to meet, are you coming to the 50th at Stone Point then RHYC.
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Re: Masthead sheaves

Post by Fulmar433 » Sat Apr 28, 2018 8:49 pm

I'd be surprised if it's the mast sheaves are causing a massive amount of friction, I would think it's more likely the mast sliders. You could check the halyard without the sail attached. Attach another line to the halyard and keep a load on the line whilst hoisting the halyard. You should be able to tell if there is excessive friction.
My Fulmar has an external track on the mast with roller cars. Raising and lowering the main is effortless. All I have to do is release the clutch and the sail drops most of the way on its own. Not that it's going to help you, several years ago the sail wasn't dropping as freely as normal. I found the cars were running roughly. I washed them out with WD40 and when most of it had dried out applied some silicon spray. I now spray the rollers at the start of each season with silicon which keeps it working smoothly.
David Metcalfe
Fulmar 433 Jeddo
Lower Halstow, Kent

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Re: Masthead sheaves

Post by BrightStar » Sun Apr 29, 2018 9:43 am

Thanks for that, obviously the interaction or the sail slugs with the track are a significant factor. However in my case, once the mast was down 3 of the 4 mast head sheaves were either solid (so the halyard was skidding over the sheave or so stiff as to be barely movable. After stripping, cleaning, including the sheave groove, and greasing they now rotate freely.
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Re: Masthead sheaves

Post by TyroSailor » Sun Apr 29, 2018 4:32 pm

I've sprayed some PTFE lubricant into my mast track (and elsewhere) and the main now goes up and down like a dream. How long it will last remains to be seen, but it's easily repeatable.
Last edited by TyroSailor on Sun Apr 29, 2018 8:47 pm, edited 1 time in total.
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Re: Masthead sheaves

Post by Fulmar433 » Sun Apr 29, 2018 7:47 pm

I guess my roller cars getting stiff due to crud in them is much the same as you had in the sheaves, just a different place. Fortunately for me, mine were easier to get to and clean. Now I am wishing I had taken some silicon spray with me when I went up the mast to repair my Tri Colour and Anchor light a couple of months ago. I was using the halyard but I could have sprayed the sheave and left some lubrication up there.
David Metcalfe
Fulmar 433 Jeddo
Lower Halstow, Kent

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