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I'm reviving a 1972 Aquarius A21 trailer-sailer. I need to replace the standing rigging. The boat had spreaders when I got it, but apparently that is quite rare with the A21. Here is a picture of one without and one with the spreaders:
Since I'm replacing the rigging, I'm wondering what the spreaders do for a 21' trailer-sailer. They're likely to be in the way when I raise and lower the mast, with much greater likelihood of snagging on something. On the other hand if they are necessary or recommended, then I will reinstall them on the mast after I paint it.
Basically, I'm not sure what the spreaders do. FYI, I have a back stay as part of the standing rigging in addition to the forestay and upper and lower shrouds on each side of the mast.
Spreaders put a better (wider) angle between the stays and the masthead.
There are books out there that explain the math better than I can. Basically the more the stays become parallel to the mast the more leverage they have to resist. It is an exponential thing so the forces go up quickly as the angle is reduced. I think the magic number is 12 degrees between the mast and the stays. With a short mast or wide beam they may not be necessary but most of the time they are.
I think I would look to what the designer planned for. They did the calculations and made the spreader on/off determination. Manufacturers and previous owners may have tried to save money or re-engineer the design without really understanding what they were dealing with.
Or maybe the original design didn't have stays but after a couple of failures the manufacturer and previous owners decided to change it. I think spreaders could only make the design stronger so you wouldn't be hurting yourself there.
Looking at your two pictures again it doesn't look like the spreaders add much angle at the top of the mast so maybe they aren't so critical after all.
Brian Toss's The Rigger's Apprentice has a good chapter on the subject and walks ordinary (non-engineer) types through the design process.
Good luck!
-Britton
-Britton
Work is overrated.
Most everything you read on the Internet is wrong.
On a small boat like the Aquarius (I have a C-22, so I sympathize...) I'd say the spreaders may make it easier to go forward by giving you more room behind/under the stays.
Tony, they may make it a little easier - but the difference isn't too much. Do you have them on your C-22?
Britton thanks for the info on their purpose - I'll do some reading.
Someone suggested that the spreaders weren't part of the designer's plan (Peter Barrett, I think), but that buyers wanted them as an option for their more traditional appearance. If the spreaders were an option to the original design, that sounds cosmetic to me. Also, the shrouds are located in the same place with or without the spreaders and the mast is the same height.
Rick,
Yes, we have spreaders on the C-22. It's a 25' Mast. How tall is the Aquarius mast? I wonder how much stiffness the spreaders would provide on your rig?
I've got to replace the standing rigging, so I thought this would be the time to decide to keep them or not. The length of the upper shrouds will be different with or without the spreaders. The spreaders are in fair condition, with worn areas at the tip openings where the shrouds pass through. The supporting brackets are quite thin metal.
Since I'm going to be trailering her and frequently launching and retrieving her, simplicity of mast raising is an issue. I thought it might be easier without the spreaders - less to foul during the mast raising and lowering singlehanded. Also, the brackets seem rather flimsy and could easily be bent during the process. I don't know if replacements are readily available.
The bottom line is that if the spreaders serve no real purpose other than cosmetic, mast raising and lowering would be simpler and easier without them. I know there is value to cosmetics, and as this discussion continues I find the picture with the spreaders more attractive (or is it the overall look of the boat!).
As Britton has said the spreaders allow more angle to the shrouds at the mast head. Where this really makes a difference is the fact that shroud tension can be less with a greater angle to the mast, and shroud tension is directly translated into mast compression, or a downward thrust on the mast. I think Toss describes it like pushing on opposite ends of a piece of uncooked spagetti. Triangles are very strong structures and speaders change the mast/shroud structure into two separate triangles so each side of the mast contains three distinct triangles intsead of two.
Two very succesful trailer sailers, the San Juan 21 and 23 both use spreaders well.
Perhaps a little thought of how to strengthen the spreader brackets would ease some worry.
Thanks for the feedback. A little more strength in the rigging certainly is a benefit. I also like the idea of additional room to get around on the deck. I'm going with the concensus to keep them. Now lets see if I can improve on the brackets ...
Rick,
Depending on your extrusion, take a look at the brackets for the C-22. You can find them online at Catalina Direct They're a newer, stronger design than the original and would be plenty strong for your boat. There's a different design for oval and flat sided masts.[/url]
