430 - Replacing Sheaves

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Replacing Sheaves

Printed From: myHanse.com
Category: Hints & Tips
Forum Name: 430
Forum Description: 430 Hints and Tips
URL: https://www.myhanse.com/forum_posts.asp?TID=15388
Printed Date: 27 March 2026 at 01:23
Software Version: Web Wiz Forums 12.06 - https://www.webwizforums.com

Topic: Replacing Sheaves

Posted By: Issywa
Subject: Replacing Sheaves
Date Posted: 07 October 2025 at 04:56

I need to replace the sheaves in my boom as well as those at the masthead.

How difficult was it to do this? Is it simply a matter of using a drift pin and pounding them out?

Replies:

Posted By: Wild
Date Posted: 07 October 2025 at 08:39

Its depends brand and type of the mast and boom.

The replacement by SELDEN masthead is a strait forwards job.

Unscrew one bolt ,lift the allu separator plate ,take bought mainhalyard and toppinglift line off the sheaves, liftup the sheaves together with the shaft.

The only problem with our fractional mast setup is : the only line who’s left to get you up to the top is the spinakker halyard and this is 2meter lower than the top.So you have to find a solution to fix you in the top of the mast🤬😱 when you have to lift up the main-and toppinglift lines.

The boom it very depends which type ,some are easy other very difficult.

Try to contact the brand to get some advice.

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Wild and Wet
Belgium
545e#268

Posted By: Pat Butler
Date Posted: 10 October 2025 at 01:57

Also, according to our local rigger, our mast head unit was totally under-spec (Sparcraft) and so we followed his advice and let him cut out that unit and totally rebuild it to spec. Our problem that led to this was the main halyard would jump off the sheave and get irretrievably jammed between the separating plate and the sheave which was frustrating and potentially very dangerous. Otherwise, replacing the sheaves would have been the same as the above

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"Right Time" Hanse 342 3 cabin, wheel helm, shallow draught. Hull #470

Posted By: Rock
Date Posted: 10 October 2025 at 18:02

Hi pat,

What specifically do you mean with ‘under spec’ ?

BR,

Peter

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Hanse 400e "M-square2" #0241

Posted By: Pat Butler
Date Posted: 10 October 2025 at 20:44

Peter the rigger told us the main problem which he has fixed on a number of production boats, was the plate that separates the port and starboard sheaves is too thin and not welded in place, so it tends to move/bend under load, particularly if you say were trying to reef or raise the main while running down wind. On the Sparcraft masts all that holds the plate in place is a slide too and bottom and the sheave axles running through it. The rigger built one with a sturdier plate that was welded in place. Sheaves could still be removed as per normal for inspection/replacement

Hope that helps

Regards

Pat Butler

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"Right Time" Hanse 342 3 cabin, wheel helm, shallow draught. Hull #470

Posted By: Rock
Date Posted: 11 October 2025 at 20:26

Got it Pat,

I remember the plate to be thin and wobbly when I had the mast down for standing rig replacement.

It may actually be the cause of the wear/chaff I have on my main halyard.

Have to cut off some 20 cm’s every 2-3 years.

Thanks for bringing it up.

Peter

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Hanse 400e "M-square2" #0241

Posted By: Martin&Rene
Date Posted: 12 October 2025 at 14:04

I turn my halyards round end to end every few years and I have even switched the jib and main halyards around to even out the wear. Replacing Dyneema halyards is not cheap, so best avoided where possible.

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Martin&Rene Hanse 341 Dipper Wheel steering, 3 cabin layout, normally based in Scotland

Posted By: Issywa
Date Posted: 31 January 2026 at 07:03

As a follow up to my original post, turns out it was easy to remove the sheaves on my Sparcraft boom. They were easy to pound out by hammering on the end of a drift pin. Now I can revise the single line reefing to a two line system whereby I use a Cunningham to secure the tack points on the luff. I had trouble achieving a flat main so hopefully this will be a better system.

Posted By: Mark_J1
Date Posted: 07 February 2026 at 22:21

If it’s a Sparcraft mast you can climb on the main halyard but still replace the sheaves. The pins are fairly easy to extract. Depends on your climbing skills and comfort operating at masthead though. I’ve done it using climbing strops looped over the masthead to take the my load temporarily. I’ll leave you to think through safety lines and alternate descent solutions ‘just in case’ you can’t replace the sheaves.

If you can borrow/buy a mast ladder that fits, then that makes it a much easier job. I’ve done it both ways and using my ladder makes it much simpler.

Mark

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Hanse 400e "Grey Goose" Hull #31