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Old 29-07-2020, 20:40   #1
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Join Date: May 2018
Location: Washington DC
Boat: Bristol 30
Posts: 96
Using boom bail (on mast) for mounting turning blocks

user billdre suggested me this on another thread. In this thread, I voice my concerns about various turning block mounting options I've thought of. https://www.cruisersforum.com/forums...ls-237586.html

Vessel is a Bristol 30, and I'm trying to run main halyard, 2 single line reef lines (or double, I haven't decided yet), outhaul, topping lift and vang to the cockpit.

My vang is mounted to my ast via through-bolt using a 3/8" bolt, as recommended to me by a professional rigger. Sheer strength for gr5 and gr8 bolts are close to 8000 lbs. Vang seems to see upwards to 4000lbs of load.

Calculations show, assuming 1200lbs of mainsail halyard tension, the turning block will see upwards to 2000lbs forces. My best mounting solution was to have pad eyes through bolted to the mast just above the vang.

Unfortunately, the biggest pad eyes that would let me do that will not survive a bad-case scenario (35kts with full sail up, esp with shock loading in the case of an accidental gybe).

So I'm revisiting the boom bail idea. If I drilled another through-hole right above or below the bail I use for the vang, and mount my turning blocks to that, it should be very very strong. It'll also solve all my geometry problems as the blocks would move with the boom on each tack. I'd share the same bail, but I don't want to overload an already very loaded piece of hardware.



My only concern is that I'll have two highly loaded through-bolts of 3/8" diameter at two points, very close to each other, at the mast. Would this be bad for the mast? I'm worried this would cause the aluminum of the mast to deform.

Thank you in advance.
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Old 29-07-2020, 20:55   #2
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Join Date: Dec 2011
Location: New York
Boat: Columbia 50
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Re: Using boom bail (on mast) for mounting turning blocks

Get a mast step plate.......
Untitled Document
Or given your mast step appears to be on a little raised section, padeyes on the deck (with backing plates), or a big fat eyebolt through that step horizontally with with an eye-nut on the other side.



Matt
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Old 29-07-2020, 21:15   #3
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Re: Using boom bail (on mast) for mounting turning blocks

Quote:
Originally Posted by mlydon View Post
Get a mast step plate.......
Untitled Document
Or given your mast step appears to be on a little raised section, padeyes on the deck (with backing plates), or a big fat eyebolt through that step horizontally with with an eye-nut on the other side.



Matt
Matt, those are all options thought of, but I'm not sure if that is possible with this mast because of that raised section. Not a lot of room there. And I learned from that other thread that drilling through that raised section (which was my original plan) would not work -- its filled with steel plates that are really hard to drill through, and since they are supposed to distribute the load of the mast onto the deck, shouldn't be compromised with either the hole or the inevitable rust after many years of use.

(I also really don't want to pay a rigger. rates are expensive here)
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