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Old 17-07-2012, 21:43   #1
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Any Riggers out there?

I am possibly looking at fitting a used mast off a monohull onto a big sailing catamaran. It would be used for minor cruising and blue cruising. My question is, if taken easy in heavy winds reefing down the sail could I expect to get by? I have seen on some "home built" cats that have monohull masts and have been around for quite a while. Would I be nuts to think I could get by one one for the next 10 years?
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Old 17-07-2012, 22:51   #2
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Re: Any Riggers out there?

There are really to may variables to really give you a good answer.

Monohull masts are relatively weak compared to a multihull rig because the maximum righting moment of the boat is so different. This means the rig has to handle much greater loads on a multi than a mono.

Of course this is offset by the fact that the spreaders are much longer, so you have more support for the rig.

Absent hiring a professional rigger (Not a local boat guy) to do force calculations there is just no way to tell for sure. You could pick up a copy of Brion Toss' book "The Complete Riggers Apprentice" that has the load calculations you would need to do to determine if it would work. But even then, you are relying on your math skills.
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Old 18-07-2012, 03:18   #3
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Re: Any Riggers out there?

Hi Tmoney,

I strongly suggest that you forget this option, it can be very dangereous.. Not only the cat masts are significantly stronger than those of monohulls , their spreaders, fixing systems, the load distribution on the mast also is quite different. (While all of the monohulls have a backstay, with the exception of Prouts most of the multis don't have a backstay)

Cheers

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Old 18-07-2012, 06:03   #4
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Re: Any Riggers out there?

My brother put a carbonfibre monohull mast into his racing trimaran. He had some serious engineering calculations done by some mates working for NZ top riggers first, and it was cut down from a broken mast from a much bigger mono.

"Principles of yacht design" gives some more calculations that may be useful.

You certainly could not just put it in as is and have any right to expect it to stay up, even if you are taking it easy, the loads on a big multi are huge.

Saying that with enough spreaders and a decent staying base it could be doable, BUT the calculations need to be done properly and you must have complete confidence in the rig.
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Old 19-07-2012, 00:18   #5
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Re: Any Riggers out there?

Only reason I ask is I cannot afford a brand new rig and it is nearly impossible to find a used Cat rig let alone one of the size I need. All the standing rigging can be made however it is needed and spreaders can be added/modified. I would also step the mast down through to the bottom not step it to the deck and would even consider the spreader cables running through the cabin to the bottom of the boat. The only reason for this question is 50-80k for a new Cat rig is out of the question for me.
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Old 19-07-2012, 10:18   #6
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Re: Any Riggers out there?

You should deck step the mast and use a compression post to transfer the load to the crossbeam. This works well and has the added advantage of not requiring a large hole in the roof for leaks to develop.
Standing rigging should be attached to the sides of the vessel as usual, some shrouds are occasionally attached to the inboard hull sides but attaching them to the outboard hull sides gives you a more favorable angle for supporting the rig.
My advice is, as usual, worth what you pay for it.
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Old 19-07-2012, 12:36   #7
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Re: Any Riggers out there?

Quote:
Originally Posted by tmoney View Post
Only reason I ask is I cannot afford a brand new rig and it is nearly impossible to find a used Cat rig let alone one of the size I need. All the standing rigging can be made however it is needed and spreaders can be added/modified. I would also step the mast down through to the bottom not step it to the deck and would even consider the spreader cables running through the cabin to the bottom of the boat. The only reason for this question is 50-80k for a new Cat rig is out of the question for me.
The problem isn't the rigging, or the mast step. Whatever gear you have in this regard will be fine. The problem is the aluminium tube you are trying to put on the boat. A mast section of a certain profile and weight will oly have so much strength. Multihulls require much stronger masts because the loads are much higher than on a monohull of comperable size.

I am sorry, but there just isn't much good news here. A thinner or smaller profile rig just isn't as strong as a thicker larger profile and can't take the loads. There are ways to use a smaller section, but this would absolutely require hiring a NA to engineer a support structure capable of imparting enoug stiffness in your mast to keep it up. Even then depending on how far out of ideal your rig is it may be impossible. Because your rig may not have the compression strength to withstand the loads.

The only other option I can suggest is to start scrounging boat yards for abandoned mast sections from much larger boats. Particularly in hurricane prone places most yards have at least a couple of old rigs lying around, and you might be able to pick one of those up cheap. assuming its from a monohull you will likely need to cut it down somewhat but that is a pretty easy process.
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Old 19-07-2012, 22:14   #8
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Re: Any Riggers out there?

What is your location? What flavor and length is your cat? Maybe we can find you a mast.

Wait a moment... This is Tmoney, isn't it? Still looking at that cat off the Bali Hai?
Didn't I tell you to go and talk to Fritz at Pacific Offshore Rigging on Canon Street? How many times do you need to be told?
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Old 19-07-2012, 22:19   #9
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Re: Any Riggers out there?

Quote:
Originally Posted by tmoney View Post
I am possibly looking at fitting a used mast off a monohull onto a big sailing catamaran.
Bad idea. The bigger the catamaran, the badder the idea.
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Old 20-07-2012, 09:14   #10
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Re: Any Riggers out there?

save your money, DON"T do it. The loads on the cat are so much larger than a mono. The cat doesn't spill any wind by heeling.
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Old 22-07-2012, 18:49   #11
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Re: Any Riggers out there?

The boat I am looking at is in San Diego. Its 52ft in length. It is a nice boat but has not been completely finished. I would have a budget of around 20k to get her rigged up for sailing from scratch basically. I have found full setups tall enough from a monohull for around 2-7k but a used cat mast is pretty hard to find.
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Old 22-07-2012, 21:56   #12
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Re: Any Riggers out there?

Tmoney,

I hate to say it, but even if a rig was free, I am not sure you could meet your budget. By the time you add sails, standing rigging, running rigging, the transport and installation costs, any outfitting, ect... I don't think you can hit $20,000. And if you can the chances you will be able to afford extras like a roller furler on the jib, are very minimal.

Given your budget, I think realistically you either need to find a smaller boat, or find one with an intact rig. For many boats the cost of the rigging is actually a significant part of the value of the boat. In some cases it is worth more than the entire rest of the boat combined.

An Olson 30' I know of for instance broke its mast. The owner found it was cheaper to buy an entire used Olson just for the rig, than it was to buy just a new mast.


I am sorry, and hate to be the bearer of bad news, but I think this project is more than your budget can handle.
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Old 13-01-2013, 14:57   #13
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Re: Any Riggers out there?

Hi verybody out there , I own a Lagoon 42 build 1996, a I am very happy with the boat a the Rig. Seems like the constuctours did a great job there are no signes of weakness.
Do I need to change there supporting wires anyway. Thanks and regards
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Old 13-01-2013, 17:49   #14
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Re: Any Riggers out there?

That's 17 year old standing rigging you got their. If you will be sailing around the harbor , ok but if you are going cruising.......I would definitely change it. I don't think insurance will cover mast failure if the rigging is older than 10 years. Imagine , wind of 20 knts and you flying along..what's going through your mind ? Hope my rigging's gonna hold. I replaced the fore stay , cap shrouds and intermediates last year. My cat is a 2003
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