Double spreader rigs vs single spreader rigs

Scott T-Bird

Scott T-Bird

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Oct 26, 2008
6,220
Catalina 320 Barnegat, NJ
Sue is chasing down boat advertisements … I'm not sure what has got into her. Perhaps it was the racing we started to do last summer! In any case, she has been pointing out Catalina 34 MK II as something she would like to see. I've been favoring Catalina 320. The vintage would be about the same for both boats - 1996-2001 - in our searches. One thing I noticed between the 2. The taller mast on 34 MK II is a single spreader. The 320 is a double spreader rig. Is there any significant difference? Would a double spreader rig be more performance oriented? Obviously, both are masthead rigs. :what:
 
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dlochner

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Jan 11, 2014
12,392
Sabre 362 113 Fair Haven, NY
Scott, there is the simple explanation and the more complex explanation. I'll stick to the simple. If you get Brion Toss's book, he goes in to greater detail. The big description involves mast stiffness, shroud angles, spreader length and stiffness and chain plate locations. As well as a lot of math and trigonometry.

The short answer is, lighter more flexible masts and masts with a taper require more support in critical areas than a tree trunk mast. Lighter and tapered masts need the second set of spreaders to get the correct angles to keep the mast vertical.

If you look at both boats, I'm going guess the 34 MK II has a stiffer heavier mast than the 320 and the chain plates are further outboard on the 34 than the 320.

It is a performance issue. Lighter more flexible masts allow for using backstay tension to shape sails and reduce weight aloft. Both good things for optimizing performance.
 
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Davidasailor26

Davidasailor26

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May 17, 2004
5,462
Beneteau Oceanis 37 Havre de Grace
The downside of the double spreader rigs is that tuning the rig is a more complicated process, and may require going aloft if the shrouds are not continuous and turnbuckles are above the spreaders.
 
JRT

JRT

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Feb 14, 2017
2,051
Catalina 310 211 Lake Guntersville, AL
The nice thing for my observations from the double on the 310 is the deck is clear and easy to walk without ducking. Also and trim in tighter. The 34 is a nice big boat, especially the mkII. If there was one as nice as my 310 we probably would have gone that way just for the space. But after a year with the 310 I'm happy how it worked out.
 
Ward H

Ward H

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Nov 7, 2011
3,763
Catalina 30 Mk II Cedar Creek, Bayville NJ
@Scott T-Bird Cool that Sue is helping in the search. :biggrin:
But how are you going to fit a C34 into your slip?
Good Hunting!
 
Will Gilmore

Will Gilmore

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Oct 19, 2017
7,845
O'Day 19 Littleton, NH
I could never see the advantage of double spreaders on boats under 45 feet. It seems that any weight savings is lost with the extra set of spreaders aloft as well as the extra cable and hardware. Perhaps, but really? The added complexity would, it also seems to me, to make performance tuning a pain. If it were really so, wouldn't larger high performance boats all have multiple spreaders?

Of course, I suppose it depends on how much you want to spend on a mast :waycool:.

-Will (Dragonfly)
 
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dlochner

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Jan 11, 2014
12,392
Sabre 362 113 Fair Haven, NY
Will Gilmore said:
I could never see the advantage of double spreaders on boats under 45 feet. It seems that any weight savings is lost with the extra set of spreaders aloft as well as the extra cable and hardware. Perhaps, but really? The added complexity would, it also seems to me, to make performance tuning a pain. If it were really so, wouldn't larger high performance boats all have multiple spreaders?

Of course, I suppose it depends on how much you want to spend on a mast :waycool:.

-Will (Dragonfly)
Click to expand
The angle of the mast and shroud is critical. The upper spreader is needed to achieve that angle. On Cats, the boat's beam is wide enough to achieve the angle with a single spreader. On a mono hull with inboard chainplates, the second set of spreaders is necessary.
 
JK_Boston_Catalina310

JK_Boston_Catalina310

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Nov 18, 2010
2,441
Catalina 310 Hingham, MA
There is a simpler answer that probably played more of an issue with Catalina going from single to double spreaders. Single spreader masts "pump" at slips in the wind. It's not loud but something that is noticed when people try to sleep on boats in slips. Catalina 30s have this problem also. On a mooring or the hook it is less noticable.

Good luck with the search.
 
Scott T-Bird

Scott T-Bird

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Oct 26, 2008
6,220
Catalina 320 Barnegat, NJ
JRT said:
The nice thing for my observations from the double on the 310 is the deck is clear and easy to walk without ducking. Also and trim in tighter. The 34 is a nice big boat, especially the mkII.
Click to expand
I don't think I understand this comment unless you weren't making a comparison. Both models appear to have fore and aft lower shrouds mounted the same way.
 
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Scott T-Bird

Scott T-Bird

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Oct 26, 2008
6,220
Catalina 320 Barnegat, NJ
Great comments! As usual, there does not seem to be a clear advantage and always trade-offs. Sue wants to look at a 34 near us over the weekend, so I guess I will have to follow! As always, there are multiple factors to consider!
 
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dlochner

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Jan 11, 2014
12,392
Sabre 362 113 Fair Haven, NY
Scott T-Bird said:
I don't think I understand this comment unless you weren't making a comparison. Both models appear to have fore and aft lower shrouds mounted the same way.
Click to expand
Where are the chainplates on the 320? I believe they are next to the deck house, so the side decks are clear.
 
Scott T-Bird

Scott T-Bird

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Oct 26, 2008
6,220
Catalina 320 Barnegat, NJ
dlochner said:
Where are the chainplates on the 320? I believe they are next to the deck house, so the side decks are clear.
Click to expand
Yes, same as the 34 so I don't think there was intended to be a distinction between the 2 models.
 
JRT

JRT

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Feb 14, 2017
2,051
Catalina 310 211 Lake Guntersville, AL
Scott T-Bird said:
I don't think I understand this comment unless you weren't making a comparison. Both models appear to have fore and aft lower shrouds mounted the same way.
Click to expand
Sorry didn't mean to compare them as if they were different. Just something I started to notice after looking at the Jeanneau 440 and then realized what the design did to favor deck movement, at least in my opinion. We liked the space very much or the 34, but the model we looked at was a MK1 and needed a lot of work to be nice. In the end getting the nicest condition boat was our best criteria to meet since we just don't have time for a project.
 
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dlochner

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Jan 11, 2014
12,392
Sabre 362 113 Fair Haven, NY
JK_Boston_Catalina310 said:
There is a simpler answer that probably played more of an issue with Catalina going from single to double spreaders. Single spreader masts "pump" at slips in the wind. It's not loud but something that is noticed when people try to sleep on boats in slips. Catalina 30s have this problem also. On a mooring or the hook it is less noticable.

Good luck with the search.
Click to expand
I think this is unlikely. Both boats have forward and aft lowers which is a better way to control mast pumping and prebend on the mast.

Scott T-Bird said:
Yes, same as the 34 so I don't think there was intended to be a distinction between the 2 models.
Click to expand
It may be the mast on the 320 is a smaller diameter or is tapered, requiring the added support obtained from the second spreader. Relative to the LOA the 320 has a taller mast, the I on the 320 is only 5" shorter than the 34, with a loa 2 feet shorter.
 
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