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Old 29-06-2020, 12:46   #16
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Re: How Do You Buy a Used Mast?

Exactly!!

I was about to post this to make sure the thread stays on track, but you beat me to it.


I’m not designing or engineering anything. I’m just the nitwit in the purchasing department. Ha ha.

I just want to make sure I can do my job in purchasing to keep the cost low and provide value to the organization by getting a great, used mast that will satisfy the design/engineering of the boat without breaking the bank.

Making sure this used mast fits the criteria of the design/engineering department is what I’m not sure how to do. It would seem length, various diameters and wall thickness defines a mast to me. Those other terms I have no idea about.


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Originally Posted by chris95040 View Post
Folks are correctly mentioning that there are a lot of variables that go into *designing* a rig - stay/shroud locations on the mast, chainplate locations on the boat, spreader configuration, hull's righting moment...

But you aren't *designing* a rig - you already have plans which include the mast design. You already know the answer. Now just stick to the plan, use roughly the same mast section specified in the plans and the same rigging configuration. That's all you need to proceed.

The hurdle is just going to be the impracticality of used rig shopping and getting accurate measures of the mast they are selling. Also, if the section you find is a little bit different than what the plans state, an hour of an experienced rigger's time should be able to figure out if the mast you found is similar Ixx Iyy as your plans call for.

Note that you'll likely be adding new shroud tangs, spreaders, etc per *your* plan, not per the plans from whatever boat the used mast came off of.
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Old 29-06-2020, 14:04   #17
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Re: How Do You Buy a Used Mast?

I think Chotu it's simple to purchase a used mast section for a mono since it's fairly easy to compare sections. I agree about looking at other cats your size and seeing what they have. Ideally you can find a rig of a wrecked cat that is close to what you want. I have been involved with a few used masts installs on cats and monos and they all turned out well.
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Old 29-06-2020, 14:14   #18
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Re: How Do You Buy a Used Mast?

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I think Chotu it's simple to purchase a used mast section for a mono since it's fairly easy to compare sections. I agree about looking at other cats your size and seeing what they have. Ideally you can find a rig of a wrecked cat that is close to what you want. I have been involved with a few used masts installs on cats and monos and they all turned out well.
Cheers
I actually have exact dimensions. A 60í Selden 304 section. I just need to find an equivalent.

See the attached chart for exact specifications.

Why is it different to find a mast with Selden 304 type dimensions for a catamaran than a monohull?

Do you mean monohull sections are much more common, so they are everywhere already set up?

As in... the spreaders will be in the wrong place? Also that I need a diamond rig style and the monos typically donít have that?

As in, converting a mono mast simply wonít work due to preexisting holes everywhere?
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Old 29-06-2020, 14:47   #19
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Re: How Do You Buy a Used Mast?

I think you can use a mono mast, but may have to add some rigging, due to the extra righting moments. Though, it would take someone with more experience than I have, to sort it all out, and end up with a "proper" cat mast.


I'd peruse rigrite.com, they have lots of information, specs, and parts, for older brand masts.

My sailmaker said that our rigging would be the equivalent of that found on a 75 to 80 foot mono. That one sent me for a loop, though my cap shrouds are 12mm and the forestay is 14mm, so they're not small stuff. My point is: I'd look for masts from larger boats. Though, with the weight of your boat, you may be able to use a mast from a similar sized monohull. I'm sure you're at least a tonne lighter than we are. (9 tonnes loaded to cruise, 400l water and 770l fuel; 7.5 tonnes lightship)

https://rigrite.com/A-Main/spar_M.php

Cheers, and good luck.
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Old 29-06-2020, 16:08   #20
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Re: How Do You Buy a Used Mast?

If righting moment is difficult to match, could you size a mast to the sail area, assuming it was mounted like a flag pole in cement?

What I mean is, since cat righting moments are so high, is there a calculation to show the maximum force a sail can exert on a mast (no heeling), in reasonable winds, and reverse engineer the mast to suit?

Can you put a mast from Morgan OI 51, with the sails from a Morgan OI 41, on a 50 foot ultra light Cat?

Just a thought.

Paul.
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Old 29-06-2020, 17:26   #21
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Re: How Do You Buy a Used Mast?

Some here have advised you to get a naval architect or a very experienced rigger to solve your problem. It would also be good to get someone with experience in catamarans. Certainly the large builders of cats have engineers on staff. There was a series of videos on YouTube about rebuilding a Cal 40. I'm certain a new mast was part of the project. Call the owner for advice; it won't be hard to reach him--he owns a marine equipment company. You need to get advice from a professional, not from an internet forum which has good advice mixed with some truly laughable garbage. Good luck.

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Old 29-06-2020, 17:39   #22
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Re: How Do You Buy a Used Mast?

Cracker Boy Boat Works in West Palm Beach has a number of used masts.
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Old 29-06-2020, 18:11   #23
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Re: How Do You Buy a Used Mast?

Sailor's Exchange in St. Augustine has plenty of masts to choose from, all sizes, all length's...as well as spreaders, goosenecks, top of masthead fittings, etc, etc...pretty much everything you would need, including rigging, turnbuckles, toggles, the works.
Sailorman in Ft. Lauderdale the same, but probably larger selection.
One must consider a variety of things.....are you going with a single or double spreader rig...will it be a cutter rig..?
single or double backstay...?
Will it be deck stepped or keel stepped?
what will be the angle of the lower and upper shrouds..??ie, what is the distance from mast to rigging fittings.
the forestay and backstay...?
How high of the deck will the gooseneck be ??
Will the gooseneck need to adjustable ?
Would you want a separate storm track...
Do you want internal or external sail slides...
Are you going to have running backstays...
Are you planning in having any kind of main slab reefing or other reefing arrangements.
Will the boom be part of the package ?
Will you have end of boom mainsheet or somewhere along the length of the boom...
Do you plan on having any kind of main support or tensioner??
Are you planning on a backstay tensioner.
Will the mast be raked or upright...
anodized....painted ??
etc, etc, etc...
some of the above questions need answers and then you can sally forth.
To compute a mast section takes some doing, best done by a computer program, but can be done by hand.
At the end of the day, if you need a 60' stick and know the answers to above questions, you can likely find a section to fit your needs without all the computations, especially if you know what boat it came from.
Hope this gives you some direction.
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Old 29-06-2020, 18:28   #24
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Re: How Do You Buy a Used Mast?

this may not help you, but back in the day, there was a book called " Skene's elements of Yacht design". In the book is a section on how to figure out your mast section. The book is geared for mono's, but may be applicable to cats. It's been around for years.
it's been a while since I've thumbed thru' this book, but back in the day, when I was building my boat, it was a boatbuilder's bible of sorts.
The section on masts can give you a good idea of how to go about selecting a mast.
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Old 29-06-2020, 18:28   #25
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Re: How Do You Buy a Used Mast?

As was mentioned above close enough is good enough. Look at boats similar in length weight and mast height and you have examples that will work. I had a used mast bought by the previous owner but not the same as the original. In fact quite a bit different in that it was deck stepped and double spreader while the original was keel stepped and single spreader. After agonizing over this puzzle I decided to deck step it and build a compression post to support it. It is 6' taller but as it is aluminum it has less wronging moment that the original aluminum mast. I added extra thickness to where the new chainplates were ending up. After I was done I asked a naval architect to look it over. He made one suggestion and added that I had done a good job. A few years later a friend bought a similar boat and it came with the same brand of mast but one size smaller appropriate as his boat is two feet shorter and a bit less beam. Close is good enough. Best wishes
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Old 29-06-2020, 19:24   #26
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Re: How Do You Buy a Used Mast?

Crikeys, guys, pay attention: He HAS the design parameters already. He does not need any further advice about what the extrusion should be. His question is how to determine if a prospective used mast meets those parameters, and that's a significant worry IMO.

I suspect that if the external dimensions and wall thickness are similar, then the moments will also be similar because most aluminium masts are made from similar alloys with similar physical characteristics. That opinion might well be checked out with a rigger or NA... pretty simple question with maybe a simple answer.

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Old 29-06-2020, 19:32   #27
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Re: How Do You Buy a Used Mast?

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Originally Posted by Brigadoon View Post
I bought a used stern rail at Mass Marine Parts, and it was excellent and affordable ~$400 . They have a whole yard full of sailboat parts including lots of masts and booms.

Masts - Mass Marine Parts
617-719-8232 and ask for Jon

They are in Quincy south of Boston and are worth a trip if its's not too far for you
Bingo!

Choru aren't you in new england already? This places has piles of used masts.

Though most will be from older monos...
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Old 30-06-2020, 00:14   #28
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Re: How Do You Buy a Used Mast?

Thanks, Jim.

EXACTLY!

Iím not designing anything. Just trying to buy a used mast with the specs I already have.


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Originally Posted by Jim Cate View Post
Crikeys, guys, pay attention: He HAS the design parameters already. He does not need any further advice about what the extrusion should be. His question is how to determine if a prospective used mast meets those parameters, and that's a significant worry IMO.

I suspect that if the external dimensions and wall thickness are similar, then the moments will also be similar because most aluminium masts are made from similar alloys with similar physical characteristics. That opinion might well be checked out with a rigger or NA... pretty simple question with maybe a simple answer.

Jim
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Old 30-06-2020, 00:15   #29
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Re: How Do You Buy a Used Mast?

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Bingo!

Choru aren't you in new england already? This places has piles of used masts.

Though most will be from older monos...
Yes, I’m in New England, but I’m on my monohull. My catamaran is in Florida. It’s the catamaran that needs the rig.

I’m selling the monohull in about 8 weeks then going to complete the cat.
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Old 30-06-2020, 03:03   #30
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Exclamation Re: How Do You Buy a Used Mast?

I agree with Jim as long as the section is very similar then I would pay a rigger for his opinion on the mast you choose. I have seen a few used rigs on cats that looked like Swiss cheese from all the old fittings. My own used mast l filled those holes with epoxy filler which has not fallen out after four years.
Chotu I was meaning that there will be way more used mono hull masts than cat masts mainly because cats are relatively new to the scene.
Surely there is an old Lagoon mast or similar on the east coast? If it came with sails l would seriously consider it and discard the design you have........ after talking to a rigger.
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