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Old 01-21-2012, 08:39 AM   #1
dvd
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Rigging a Mast Strongback

I would like to rig up a "flopper-stopper" type stabilizer off of my boom (for use at anchor), but I am concerned that my mast rigging is not set up adequately for this type of stress. I have a very substantial tabernacle and a heavy-duty stainless steel spreader/crown at the top of my mast. The crown has fittings for four shrouds (2 fore and 2 aft) but only the fore shrouds are in place, running to chainstays on the side of the bridge at about a 30 degree angle. While the boom is not in use, the martingales act as the aft shrouds. If I use the boom for the flopper-stopper I would then have no tension support to the mast from aft. Nordhavn solves this problem by using "strongbacks," or fixed tubing running from the cabintop to the mast and taking both tension and compression forces. I seems like it would be a simple fix to replace my standing rigging with strongbacks, but I have no idea what to use for material and/or connectors.

Any ideas? [37 ft. Newburyport, 13 ft. beam, 22T]

Thanks,

dvd
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Old 01-21-2012, 09:00 AM   #2
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RE: Rigging a Mast Strongback

Why not just go back to the aft stays?* If not...I guess someone could look up the compression/tension strengths of steel or aluminum tubing and match it to the tensile strength of whatever sized wire was in your standing rigging.*

If you are asking...the attachment points on your cabin would have to be engineered to match (can't just use the old chainplates as they are designed only for tension)...and I would guess you are already in over your head without someone redesigning your rig fror you.
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Old 01-21-2012, 11:13 AM   #3
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RE: Rigging a Mast Strongback

DVD -
where was that picture taken (looking aft toward a city)? What city is that?
Also - not sure if it helps - but I'm attaching a picture of my boat, which the previous owner installed outrigers to, to use "fish" to prevent roll while under way. I am thinking of using them for flopper stoppers, too, while at anchor.
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Old 01-21-2012, 11:24 AM   #4
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Rigging a Mast Strongback

With aft stays I could not swing my boom out 90 degrees to support the flopper-stopper. The stainless steel chain plates, like most everything associated with the rigging on this boat, are substantial and probably overbuilt, sitting on top of and sandwiching the flybridge coaming at a point where it is a solid three inches of thick FRP right above the structural connection to the cabin top (sorry, don't have a picture of that area - just by looking, they appear to be at least as substantial as the cabin-top plates on a friend's Nordhavn 46) and any compressive forces would be transferred to the cabin walls.

I was thinking aluminum tubing, which I could research to get the appropriate type/strength, but I'm at a loss on type of connectors and/or where to look for them. I assume the appropriate connector would include some type of adjusting mechanism equivalent to a turnbuckle?

My friend is off to the Caribbean in his Nordhavn, so I can't look at his rig. Anyone else have a setup like this?

Thanks,
dvd

*

P.S. The pic was leaving NY Harbor heading south to Sandy Hook.


-- Edited by dvd on Saturday 21st of January 2012 12:25:16 PM
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Old 01-21-2012, 11:27 AM   #5
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RE: Rigging a Mast Strongback

7tiger7 --

Nice outrigger setup. Any idea who put that together?

Thanks,
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Old 01-21-2012, 11:27 AM   #6
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RE: Rigging a Mast Strongback

Another option - not a great one - just tie the flopper stoppers off on cleats amidships. You will not have as great an effect, since the lever arm will be shorter in relation to the centerline of your boat... but might be an easy interim solution...
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Old 01-21-2012, 02:42 PM   #7
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RE: Rigging a Mast Strongback

Contact Forspar.* We see a lot of their systems on many differnt boats and they don't look that complicated.

http://www.forespar.com/products/rol...-stopper.shtml

Magma makes a*flooper stopper.* They may also be a source for information.
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Old 01-21-2012, 11:00 PM   #8
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RE: Rigging a Mast Strongback

Hi DVD - I think it was designed and built by the previous owner - I would ask him, but he passed away before I bought the boat.
If you'd like, I can send you more pictures of the way it is set up...
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Old 01-22-2012, 07:39 AM   #9
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RE: Rigging a Mast Strongback

Quote:
dvd wrote:
With aft stays I could not swing my boom out 90 degrees to support the flopper-stopper. The stainless steel chain plates, like most everything associated with the rigging on this boat, are substantial and probably overbuilt, sitting on top of and sandwiching the flybridge coaming at a point where it is a solid three inches of thick FRP right above the structural connection to the cabin top (sorry, don't have a picture of that area - just by looking, they appear to be at least as substantial as the cabin-top plates on a friend's Nordhavn 46) and any compressive forces would be transferred to the cabin walls.

I was thinking aluminum tubing, which I could research to get the appropriate type/strength, but I'm at a loss on type of connectors and/or where to look for them. I assume the appropriate connector would include some type of adjusting mechanism equivalent to a turnbuckle?

My friend is off to the Caribbean in his Nordhavn, so I can't look at his rig. Anyone else have a setup like this?

Thanks,
dvd

*

P.S. The pic was leaving NY Harbor heading south to Sandy Hook.



-- Edited by dvd on Saturday 21st of January 2012 12:25:16 PM
*I'm guessing your setup is*not too different than my boat...I would leave the aft stays and just remove one and swing the boom out 90 degrees.* It only takes me about a minute to unhook a stay...another 30 seconds or so to reconnect and tighten.* Certainly no big deal if I was going through the trouble of setting out flopper stoppers.

I think strongbacks would be pretty unsightly on your style boat.

Remember, the flopper stoppers don't HAVE to be out 90 degrees...
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