Does anyone know if there are metal replacement sheaves available anywhere for a P16 mast head? Mine has these cheap white plastic ones which damage easily, and allow the cable to jump off and jam up (a major pain when you can't get the sail up or down). Seems pretty commonsense to me that a sheave used with a steel cable should be made of metal, not plastic. Checked Murray's website and they seem to only have plastic.

Jason

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Jason Kasper
2000 Mystère 5.0XL
Lake St Francis (St Lawrence River)
Lancaster, Ontario, Canada
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They are delron not plastic, and the reason that the wire portion of the halyard jumps the sheave is normally operator error. When you hoist the mainsail you should be pulling directly over the front of the mast. Over the years I have watched numerous sailors pulling the halyard from the side, which puts stress on the sheave and will damage it as well. Normally taking a portion out of the thin upper part which will allow the halyard to jump. If the sheaves were made of metal and the sailor pulls the halyard from the side, the wire portion of the halyard is now the part that will become damaged. Pulling the halyard from the front and over the top will also make the mainsail go up easier.

My 5.7 is an '84, & still has the original sheaves up top. One shows a bit of wear, but not worth replacing, so I don't think the material is a problem. Have a look at the tolerance between the sheave & the sides of the casting. If there is room there, the halyard can come off. This is true whether the sheave is metal or synthetic. It may be that your sheaves are worn, or they have been replaced with an incorrect part.
I put some lube on my pins last year as they were squealing while raising the sail. I don't think I have a photo, but I did look for wear, & noticed there was almost no way for the halyard to jump off. If I pull the wire portion of the halyard to far down, it can jam the connection between the wire & line into the sheave. That can take a good solid yank to free up.

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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Edchris177

The P-16 mast head is differentMy 5.7 is an '84, & still has the original sheaves up top. One shows a bit of wear, but not worth replacing, so I don't think the material is a problem. Have a look at the tolerance between the sheave & the sides of the casting. If there is room there, the halyard can come off. This is true whether the sheave is metal or synthetic. It may be that your sheaves are worn, or they have been replaced with an incorrect part.
I put some lube on my pins last year as they were squealing while raising the sail. I don't think I have a photo, but I did look for wear, & noticed there was almost no way for the halyard to jump off. If I pull the wire portion of the halyard to far down, it can jam the connection between the wire & line into the sheave. That can take a good solid yank to free up.

OK, maybe i've been pulling from the side a bit since i raise the sail with the cat on a boat lift. Regardless i still need two sheaves. Murray's has them but takes an unbelieveable 2-6 weeks to ship them to Canada (for $30 shipping cost, even)! summer'll be over by then so I need to find an alternative. There's a small Hobiedealer nearby, anyone know if Hobie has a similar size sheave on one of their cats?

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Jason Kasper
2000 Mystère 5.0XL
Lake St Francis (St Lawrence River)
Lancaster, Ontario, Canada
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OK, maybe i've been pulling from the side a bit since i raise the sail with the cat on a boat lift. Regardless i still need two sheaves. Murray's has them but takes an unbelieveable 2-6 weeks to ship them to Canada (for $30 shipping cost, even)! summer'll be over by then so I need to find an alternative. There's a small Hobiedealer nearby, anyone know if Hobie has a similar size sheave on one of their cats?

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Jason Kasper
2000 Mystère 5.0XL
Lake St Francis (St Lawrence River)
Lancaster, Ontario, Canada
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take one to your hardware store...the lowes by my house has some similar sheaves i noticed...mayby you can find something to work for the summer. it doesn't have to be exactly the same, but close enough(hand grenade theory). good luck and it definitely works best raising from the front of mast.

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bill harris
hattiesburg, mississippi
prindle 16- "BLUE RIBBON"
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OK, maybe i've been pulling from the side a bit since i raise the sail with the cat on a boat lift.

Kasper, I also keep my cat on a modified seadoo lift. I rotate the mast towards the side I'm standing on, then raise the sail. If your Cat has mast rotation control, cleat it so it stays towards the side you are on. I find that aids greatly in smoothness & when trying to catch the hook.
I know what you mean about the expensive shipping. I stopped in at Murrays while in Carpenteria last year. They were very good at taking me through the wharehouse & picking out parts. I tried to get eveything I needed, or might need, due to shipping costs. I mentioned the issue with expensive shipping to Canada with one of the senior guys there.
He told me that standard shipping gets quoted automatically with the order, BUT, if I were to just call them regarding a small item, "they could just drop it in an envelope for quite a bit less."
For 2 sheaves I would try it, call them. Also, ask them to send it US Postal Service, it will get here quite quickly, (mine came in less than a week) & most times with small items our post office won't bother with Customs charges and/or taxes. If they do, the Customs charge is only $5, vs $20ish from the courier services.

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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Where in Canada are you? Fogh Marine down in the Big Smoke has quite a few parts. I noticed some sheaves in West Marine last week, though they might have been for rebuilding blocks. They will order in anything in the catalog.

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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The P-16 mast head is different

Hullfyer, are you sure? They show the same part #6003 for the masthead sheave, fits the Prindle 16 & all Nacras but the 4.5.
The masthead casting shows #6602 for Nacra, & 6002 for the P16. All other Prindle masthead castings follow the convention 65xx, 68xx, 69xx. Only the P16 shows a "0" as the second digit, leading me to believe it's a typo, not the first one I've picked out in their assembly manuals.
The Prindle assembly manual uses the same diagram for the masthead as the Nacras. Isn't the 16 comprised of 2 sheaves, fore & aft & the same masthead hook (fork) as the older Nacras? IIRC the measurement between sheaves was 2 1/2" CTC on the pins.

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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I am 100% sure. I have one of each in my yard. I am not talking abouut the sheaves being different but the mast heads castings are very different. Nacra 5.2 5.8, hobie 14 and 16, prindle 15 and 16 all use the hook (fork) method as well as some other smaller cats, but all three brands have a different mast head casting. IMO the nacra mast head casting is the best of all 3. When you see one you will understand why it would be harder to have the halyard come off the sheave than the other 2.

OK, you got 'em, you know! There are 2 different mastheads on the Nacras, mine uses the one with 2 sheaves, i've never had a problem. Is it the 1 sheave models that are more prone to derail?

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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The original post was about a Prindle 16, not a nacra, and that is what I replied to.