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Zach

Building a spinnaker crane?

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Hi Guys,

I've got a Luders 44 that is a masthead rigged sloop, and I'm curious how many inches do you like to see the spinnaker crane eye bolts be forward of the forestay clevis pin, and about how far apart do you like to see the two ears project?

Looking to keep things from chafing and halyard slap to a minimum with two external spinnaker halyards.  The masthead is a new piece with a flat top, trying to figure on all the details before welding it up.

Thanks,

Zach

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Sketch of what you're building? depends also on what size blocks you will use for those halyards. There must be a vertical rib (either above or below) to support the extensions.

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Z:

Old boat, so old questions: Wood spar or alloy?  Internal halyard or external?  Sounds like you want external which seems like a lot of windage and spaghetti and an even larger winch farm.  Do you really want 4 forward halyards? Spin peels, bloopers?

Check with an old timer at Navy or Coast Guard to see how they rigged and flew the kites on those old warhorses.

As to chafe, if your bowman crosses your halyards, you will get chafe.  May not be relevant, but If the tails could run inside the spar, then you would have a chafe point where the halyard leaves the mast for the spinnaker crane.  The further out the crane, the greater the exit angle and the greater the risk of chafe.  If you are trying to avoid chafe with internal tails, you'd need to bring the halyard tail from the crane to a fairlead then through the slot into the mast.  You can check the rigging of the fractional boats that have a masthead kite: external block, halyard tail runs external to a spectacle (fairlead) then through slot.

Some more modern masthead boats use a triple sheaves forward: center for jib and 2 wings for kite or jib change.  Yes, the kite halyards can chafe on the headstay and on the cheeks of the masthead sheave box.  Usually not a big deal though.  3 halyards are pretty sufficient for most boats.  Reducing the kite to 1 halyard and having the ability to use one of the jib halyards would reduce the windage and slap potential 50%

Or ask your rigger & sailmaker.

 

 

 

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Thanks guys...

Pinching,

I'm not sure we have the real estate inside the mast to run triple internal halyards, as to widen the sheave box any more it would take the curved fore and aft faces of the mast almost totally off.  With double halyard sheaves, we are 1 7/8" wide on the new sheave box.

Her old masthead had a one jib, one main halyard.  Mast has a 14 foot taper, is aluminum and ends up at the top 7 inches wide by 4 1/2 at the widest of the oval.  It was a cup shaped that wedged on to the mast, and to service the sheaves the mast and rigging had to come down, and masthead come off.  The plan on the new masthead is to run the sheave axles throu

The old spinnaker crane was a rotating sheave that projected a few inches above the masthead...  But could rotate 360 degrees and meant no antennas or anchor lights on the mast.

 

 

 

 

IMG_6348.JPG

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The new masthead we are building is a double sheave for jib and main the depth of the old slot in the mast.  The scribe lines on the side show the masthead opening.  We kept the centerline widths for the forestay and backstay the same.

It'll get cut down a bit from the total width of the existing flange, but for right now it is easier to clamp onto straight sided.

Zach

 

IMG_6351.JPG

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Top view of the new masthead. 

Forestay clevis pin is 4 inches forward of the mast wall.  Top plate is 8 inches wide by 19 long for scale...

Thanks,

Zach

IMG_6352.JPG

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Yeah you are trying to put a lot of hardware into a small space.

A similar but slightly more recent welded allow MH is shown below, though not for a Navy 44.

As you can see, the shroud connections are distributed a bit more than just at the MH fitting.

 

Good luck with your project.  P

Mast 26.JPG

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Indeed.  That is one that we've been wrestling with as the aluminum masthead would take a bit of work to put the cap shrouds in the same place.  We've talked about machined aluminum blocks bolted on, and slots with toggles hanging through as the bent tang welded to the top of the stainless masthead doesn't translate well to aluminum.

I've already got the new standing rigging ready to go, so I'm debating hanging a tang/ gusset plate a foot or so down from the top of the mast and cutting off the ends of the shrouds to replace the swages with norseman fittings. 

Thanks for the feedback,


Zach

 

 

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Got down to the mast over the weekend and widened the slot for the new pieces.  Still have a bit of trimming to do to fit it to the welds. 

masthead.JPG

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Not a great pic, but this is a Swan 65 masthead, as designed by the master rigger himself, Rod Stephens.

The cranes are separate. 

Spin halyards enter the mast about 6 feet down - staggered slots, one a foot or two below the other so you don't have a "tear here" set of holes.

201511_6d40a3a8c535b786799b5295a71d176a.

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Looks like a nice setup! 

Is that a 2:1 main halyard, or just a very beefy topping lift I'm seeing?

I dropped the masthead back off with the machinist, going to end up with a 1/2 inch plate top plate to hang a pair of spinnaker blocks off, and add a welded bit under the sheaves so they can be changed without dropping them down the mast.

Do you guys have any input on compression sleeves for cap shrouds through bolts?  I've got the new shrouds made already in the old length, so the thought is to move down a foot and change to cut of the swages off and go with a mechanical end fittings at a shorter length. 

Everything we've been talking about for mounting the cap shrouds using the old location/length involves thinking outside the box a bit and a lot of machine work to do, as the stainless strap tangs welded to the top of the old masthead don't convert readily into aluminum. 

Cheers,


Zach

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