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post #11 of 28 Old 12-28-2018
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Re: Rigging spinnaker sheave

This makes me nervous. You can get big loads on the spinnaker block and a failure would surely come at the worst possible time. I'd go with the bolts as worked for others (sounds like your mast may be down, so drilling & tapping should be easy). Also, using a jib halyard for the spinnaker will likely give you the wrong geometry and lead to fouling the halyard(s) on the headstay.

What kind of boat do you have?
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post #12 of 28 Old 12-28-2018
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Re: Rigging spinnaker sheave

??? make the plate a clamp with ear brackets welded on leading edge to take pins for sheaves. If main halyard is masthead and internal maybe longer sheave pin to mate with the wrap around clamp (lower ears).
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post #13 of 28 Old 12-29-2018 Thread Starter
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Re: Rigging spinnaker sheave

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What kind of boat do you have?
Nor'sea 27.

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post #14 of 28 Old 12-29-2018 Thread Starter
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Re: Rigging spinnaker sheave

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??? make the plate a clamp with ear brackets welded on leading edge to take pins for sheaves. If main halyard is masthead and internal maybe longer sheave pin to mate with the wrap around clamp (lower ears).
Good idea, like the idea of clamping the plate using a longer pin. Have to look at the present arrangement to see if it is possible. And check with my welder about welding aluminum. He does outstanding work on stainless.

Yes the mast is down since the boat is in the driveway on its trailer.

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Re: Rigging spinnaker sheave

So make it aSS strap, clamp around the mast above the halyard pin. (so it can't slid down.) Insulate from al. Front ears, bend up frm heavier strap rivet/,weld.
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post #16 of 28 Old 12-29-2018
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Re: Rigging spinnaker sheave

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I've seen that one owner of the same model boat as ours bolted a plate to the mast head then added a couple of blocks at the end of the plate for the flying the spinnaker and sock. I'm guessing that was done so the spinnaker halyard is out front of the forestay which should avoid chaffing. I'm not to fond of drilling holes in the boat so what I'm thinking is to epoxy an aluminum plate on top of the mast head. Then add a block or two at the end of the plate for the halyard. Of course the paint of the top of the mast head would be removed, metal roughed up then JB Weld mixed and applied. Then paint it.



Is this a good plan? Maybe I'm overly concerned about chaffing and this modification is not needed? The boat does have two jib halyards available.



Regards

Jer
I think you over estimate the strength of JB Weld! That is absolutely the wrong application for that stuff. The loads on a spinnaker halyard can be pretty high. If the epoxies area proves too weak you will have a mess on your hands.

Why are you afraid to bolt anything to your mast? Bolting a block is not going to compromise the strength of the mast at all, but will give you a spin halyard you can have confidence in.

If you are not confident drilling and tapping your mast, perhaps you should enlist your local rigger to help.

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post #17 of 28 Old 12-29-2018
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Re: Rigging spinnaker sheave

If you had bought the boat from the factory with a spinnaker halyard how would the block have been installed? I don't think the factory would have glued it on. the factory would have bolted it on. don't over design it. here is one for a CAT 34 or Cat 25, simple and it is easy to build
https://www.catalinadirect.com/index...-c-27-c-28.cfm
https://www.catalinadirect.com/index...-c-34-c-36.cfm

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post #18 of 28 Old 12-29-2018 Thread Starter
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Re: Rigging spinnaker sheave

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If you had bought the boat from the factory with a spinnaker halyard how would the block have been installed? I don't think the factory would have glued it on. the factory would have bolted it on. don't over design it. here is one for a CAT 34 or Cat 25, simple and it is easy to build
https://www.catalinadirect.com/index...-c-27-c-28.cfm
https://www.catalinadirect.com/index...-c-34-c-36.cfm
Captain Len proposed making a bracket held on using the sheave clevis pins. I took a look at the mast head today and instead of holding the bracket on using the sheave pins, the forestay and backstay cleavis pins would work better. Also I thought the bracket could be fabricated using either a channel or angle bracket as a start, then overbored threw a left handed monky wrench into the works. A less than $50.00 solution from Catalina Direct, simple elegant and no hole drilling required to mount it. While that particular Spinnaker Crane won't fit (too narrow for starters) it does provide a starting concept for my fabricator. And I will contact Bob at Nor'sea about the factory option.
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Re: Rigging spinnaker sheave

Don't reinvent the wheel. Drill and tap the plate into the masthead, been done that way since forever and works. Use caulk between the plate masthead to seal out moisture and any chance of corrosion. SS spinnaker cranes with welded loop eyes sticking out horizontally usually end up bending from the downforce. A flat plate with reinforcing ridge welded to the plate and 'U' bolts for block should prevent this. Here's cast one that has the reinforcing ribs. Z-Spar Masthead Spinnaker Bails
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post #20 of 28 Old 12-30-2018 Thread Starter
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Re: Rigging spinnaker sheave

Hi, my name is Shipper Jer and I have trypophobia. (Not really, drilling holes in our boat is the very last thing I want to do)
I do appreciate the recommendation that I drill and tap the masthead then mount a flat plate for the spinnaker crane.
I'm going to mount the crane using the existing holes that are there for the sheave and stay clevis pins.

Nor'sea 27
Don't re-accommodate me, Bro
And the trees are all keep equal by hatchet, axe and saw...RUSH
I invented a new word today, plagiarism.
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