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Old 01-01-2017, 22:49   #1
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L450 Mast Sheave replacement?

Our spinnaker/gennaker sheave shattered to pieces due to a bit too much halyard tension! The forward mast sheaves axle is contained within the mast. The rigger first suggested we lower the mast and now instead is looking to have a crane with a cage so that he can lift the just mast cap to replace.

Has anyone has this problem and any good ideas for replacing the sheaves? They are plastic so I think our Southern UV got to it and I will put aluminium replacements. Anyone know the sheaves sizes?

Thanks for any advice, Dave
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Old 01-01-2017, 23:48   #2
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Re: L450 Mast Sheave replacement?

Hi Dave I bet you are getting fed up being the pioneer with these issues.

Is this the sheave that you have broken.

Photo taken before I installed spinnaker halyard.

Would not think subject to much UV with a 14 mm Halyard covering the front of sheave the rest is protected by mast.

Guess that big wing of yours would put a fair load on it. Is it run from the mast head or re directed from the lower sheave just above fore-stay.

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Old 01-01-2017, 23:53   #3
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Re: L450 Mast Sheave replacement?

Quote:
Originally Posted by DavefromNZ View Post
Our spinnaker/gennaker sheave shattered to pieces due to a bit too much halyard tension! The forward mast sheaves axle is contained within the mast. The rigger first suggested we lower the mast and now instead is looking to have a crane with a cage so that he can lift the just mast cap to replace.

Has anyone has this problem and any good ideas for replacing the sheaves? They are plastic so I think our Southern UV got to it and I will put aluminium replacements. Anyone know the sheaves sizes?

Thanks for any advice, Dave
Contact Ballenger Spars in California, Watsonville I believe. I bet they will know exactly what size and what to do.
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Old 02-01-2017, 00:05   #4
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Re: L450 Mast Sheave replacement?

Hi Paul, yes that is the one. Our halyard does go to a re direction sheave above the fore-stay. I had replaced that already with a stronger one as Rolf said he and another yacht had that rip out after a lot of spinnaker usage across the Atlantic. However I was using the gennaker when I broke the top sheave, just trying to tension too much. I have shifted the halyard to the other sheave but want to fix as I plan to sail to Vava'u in May.

Thanks Don for the info.
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Old 02-01-2017, 00:28   #5
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Re: L450 Mast Sheave replacement?

When fixing an extra spare halyard may be worth while just to ensure it will never happen again.
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Old 02-01-2017, 00:42   #6
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Re: L450 Mast Sheave replacement?

I thought about that but really I have no need for the halyard so it would just get in the way. It was not too hard to re-thread the halyard to the other sheave so I just need a working spare.

Here is what I did to strengthen the re-director sheave a pad eye with a low friction ring attached.
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Old 02-01-2017, 01:32   #7
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Re: L450 Mast Sheave replacement?

Get a sheave from Garhauer Marine or Harken. The former is what I have and they are nice. Harken will be more money and maybe a little better. Both are are ball bearing sheaves.
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Old 02-01-2017, 01:40   #8
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Re: L450 Mast Sheave replacement?

I'd suggest replacing both of them while you have good access. Since both will have gotten a good amount of UV. And it'd probably be wise to have a spare axle or two on hand when you swap them out, in case the old one is damaged, or accidentally gets dropped.

One "trick" with sheaves is to tie a line around them prior to removal, or attempting to install them. It functions both as a safety line, & a handle, for the sheave. Also, on other trick recommended by some (more for metal sheaves than polymers) is to drill a small hole in the bottom of the rope grove, & tap it for a small fastener. That way you can tie a safety line onto the fastener in order to attach a safetly line to the sheave. It's not one I've tried myself, but perhaps has merit.
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Old 02-01-2017, 08:37   #9
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Re: L450 Mast Sheave replacement?

This has just happened our 450 - watching intently!
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Old 24-02-2017, 02:06   #10
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Re: L450 Mast Sheave replacement?

A cautionary note for many Lagoon owners and especially new owners as you can demand a change at purchase.

You can see from the pictures that the standard Lagoon sheave is plastic, with no bearing inset. We shattered one with the gennaker halyard.

The solution to replace the front sheaves is to drill a hole in the mast (40mm dia) on both sides, take a cotter pin out, remove the axle and replace with an aluminium sheave.

I did the main halyard and topping lift sheaves at the same time, which was a challenge as I was hanging from them :-)

It took 4 hours to replace all and NZD 100 per sheave.

PM if you want the sheave sizes for L450.

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Old 24-02-2017, 10:42   #11
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Re: L450 Mast Sheave replacement?

Thanks, Dave. I find that disappointing that such a low quality item is installed from the factory. I would have expected a sheave with proper bearings given the loads expected.
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Old 25-02-2017, 00:30   #12
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Re: L450 Mast Sheave replacement?

Dave,

Are you at all concerned about weakening the top of the mast there, with the two 40mm holes ?

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Old 25-02-2017, 02:42   #13
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Re: L450 Mast Sheave replacement?

No, not in the least. My assessment was that the top of the mast was well above the shroud attachment points, the gennaker halyard deflector and even the mainsail head so no bending moment or shear force. There are already sizable sections cut out for the mast crane and still plenty of the mast left to support the crane and down forces.

I actually think that the riggers should have made these holes when the mast was originally installed.

Cheers, Dave
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Old 27-02-2017, 02:18   #14
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Re: L450 Mast Sheave replacement?

Quote:
Originally Posted by DavefromNZ View Post
A cautionary note for many Lagoon owners and especially new owners as you can demand a change at purchase.

You can see from the pictures that the standard Lagoon sheave is plastic, with no bearing inset. We shattered one with the gennaker halyard.

The solution to replace the front sheaves is to drill a hole in the mast (40mm dia) on both sides, take a cotter pin out, remove the axle and replace with an aluminium sheave.

I did the main halyard and topping lift sheaves at the same time, which was a challenge as I was hanging from them :-)

It took 4 hours to replace all and NZD 100 per sheave.

PM if you want the sheave sizes for L450.
Dave,

Can you send me the sheave specifics (size, manufacturer, part number, etc.)? Anything else needed?

I just had my rigging checked professionally and I later found plastic sheave pieces on deck...

Thank you.
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Old 27-02-2017, 02:35   #15
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Re: L450 Mast Sheave replacement?

I would also be very greatful for this.
Thanks Dave
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