Dual Block on Mast

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Dual Block on Mast

Postby 1987DSPrecision » Mon Jan 16, 2017 10:11 pm

I've decided I don't really like tying off the Jib and Main halyards on a cleat attached to the mast.
I always feel like I'm reaching around sail or on the wrong side.
I was on a Colgate 26 that had a very smart setup I really liked.

It went something like this:
Halayrds run down the mast into a dual block. Halyards ran from dual block to a locking cleat on the cabin roof.

I'm thinking a block like this that mounts at the base of the mast (maybe something a tad cheaper though).
https://www.westmarine.com/buy/harken--mast-base-halyard-lead-blocks--P000189451?recordNum=4

Or something like this that attaches to the mast. My concern is will drilling holes in the mast effect strength/stability? Or a mast collar maybe?
https://www.westmarine.com/buy/harken--22mm-double-micro-block--253294?recordNum=7

Finally I'd like it to end in a clutch like this mounted on the cabin deck more accessible for a single-hander trying to drop a sail while hove-to or in irons...
https://www.westmarine.com/buy/ronstan--constrictor-8-5-16-;-line-diameter-1-4-5-16-;-anchor-base-dimensions-1-w-x-4-9-16-l-x-4-1-2-h;-length-of-sock-19-11-16-;-breaking-load-1-350-1-4-;-4-050-5-16-;-weight-5-4oz--14487391?recordNum=34


So aside from the insane prices on some of these items I've linked to...why would this be a bad setup? Is there any reason why a dual block couldn't be mounted on or near the base of the mast and both halyard line be run through it? Is there any reason why a clutch couldn't be mounted on the cabin deck almost center (similar to how jib sheet cleats are located on my boat)?

Thanks for the advice,
Jeremy
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Re: Dual Block on Mast

Postby jeadstx » Tue Jan 17, 2017 3:43 am

I run my halyards through the check blocks at the base of the mast, then to cam cleats with fair leads located on each side of the horn cleats.

Here is a picture of my DS II. The cam cleats shown are from a 1968 )'Day Mariner 2+2 (dad gave me his old used hardware). My DS I is being setup similar, but I'm using new Harken cam cleats with fair leads.

Spinnaker Deck Layout - Lables.jpg
Spinnaker Deck Layout - Lables.jpg (173.75 KiB) Viewed 10785 times


John
1976 Day Sailer II, #8075 - Completed the 2011, 2012, and 2013 Texas 200
1952 Beetle Boat Swan Catboat
Early Rhodes 19
1973 Mariner 2+2, #2607 - Completed 2014, 2015 and 2016 Texas 200
1969 Day Sailer I, #3229
Fleet 135; Canyon Lake, Texas
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Re: Dual Block on Mast

Postby 1987DSPrecision » Tue Jan 17, 2017 9:08 am

Thanks John, that looks much more convenient for singlehanded sailing.
Any issues mounting those cheek blocks to the mast?
1987DSPrecision
 
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Re: Dual Block on Mast

Postby jeadstx » Wed Jan 18, 2017 3:51 am

The lower check blocks are original to the boat. The one for the spinnaker I added, drill a couple holes and rivet in place. Same way the lower ones were done.

I route everything to the cockpit. Really helps when single handing. I try not to have to get on the foredeck, even with crew.

John
1976 Day Sailer II, #8075 - Completed the 2011, 2012, and 2013 Texas 200
1952 Beetle Boat Swan Catboat
Early Rhodes 19
1973 Mariner 2+2, #2607 - Completed 2014, 2015 and 2016 Texas 200
1969 Day Sailer I, #3229
Fleet 135; Canyon Lake, Texas
jeadstx
 
Posts: 1216
Joined: Tue Jul 08, 2008 11:10 am
Location: Dripping Springs, Tx

Re: Dual Block on Mast

Postby Shagbark » Wed Jan 18, 2017 8:25 pm

John,

Did you use aluminum rivets or stainless for the cheek blocks on the mast?
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Re: Dual Block on Mast

Postby GreenLake » Wed Jan 18, 2017 9:07 pm

Just as an FYI:

The load for fastening a cheek block would be in shear. A single 3/16" aluminum rivet has about 225 lbs of shear strength, more for a pair. Some cheek blocks come with four positions for fasteners, for example something like the Ronstan RF285 with a safe working load of 660lb. Not sure they take 3/16" but it would seem that it should be possible with aluminum rivets to get close to the same load as the block is able to handle. (Just use tefgel around/under the SS parts of the block to cut corrosion, esp in salt water).

You'll note that on the production masts, all fittings like tangs for the shrouds, are riveted. But usually with closed rivets that retain the mandrel for additional shear strength.

I've used SS screws for some applications on the boom (outhaul, etc) and those have worked fine so far....
~ green ~ lake ~ ~
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Re: Dual Block on Mast

Postby jeadstx » Thu Jan 19, 2017 5:06 am

I couldn't tell you what the original rivets are. On the cheek block I added, as I recall I used aluminum.

John
1976 Day Sailer II, #8075 - Completed the 2011, 2012, and 2013 Texas 200
1952 Beetle Boat Swan Catboat
Early Rhodes 19
1973 Mariner 2+2, #2607 - Completed 2014, 2015 and 2016 Texas 200
1969 Day Sailer I, #3229
Fleet 135; Canyon Lake, Texas
jeadstx
 
Posts: 1216
Joined: Tue Jul 08, 2008 11:10 am
Location: Dripping Springs, Tx

Re: Dual Block on Mast

Postby Shagbark » Sun Jan 22, 2017 1:48 pm

Would paint work on the SS cheek block where it contacts the aluminum spar to prevent corrosion?
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Re: Dual Block on Mast

Postby GreenLake » Mon Jan 23, 2017 5:30 am

In principle, anything that isolates dissimilar materials from each other would work. The difference would then be in how well such a barrier holds out over time and in contact.

For sealing SS screws going into aluminum spars you couldn't use paint, because you'd need something that creates a film around the threads. It's for those kind of jobs that TefGel was invented. For sealing the bottom plate of a cheek block you might use some different approaches.

If you use aluminum rivets to attach a SS fitting, I would pay attention to the holes, that's where the SS would attach the rivets. In those locations paint may get scraped off during mounting, or crack, and something permanently sticky like TefGel might be more appropriate.
~ green ~ lake ~ ~
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