How Do You Buy a Used Mast?

[betwys1]

Originally Posted by GRIT

This is a 50 foot catamaran. Section, material, shroud placement, number and angle of spreaders, will all affect whether or not a mast will work on this boat.

The spreaders, and shrouds are of crucial importance in a mast, especially one as loaded as that on a 50 foot cat. If they did not matter, I'd have gladly gotten the bare pole and just put cap shrouds on it, and call it a day. But our mast supports are quite a bit more complicated than that.

I'm afraid your 22 footer isn't a good example of how any old mast will do the trick. Though, indeed, on a 22 footer pretty much any mast will do.

Cheers, and happy sailing.

Paul.

I can thoroughly recommend the gist of Paul's advice.
Surprised to see a Canadian (?) sneering at a sail boat *SO* much smaller than his (Ha!)

[Island Time O25]

Originally Posted by Brigadoon

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

I know that they ship and haul. And may still be a good deal even with shipping charges. Jon's father, Paul, runs the hauling side of the business, Continental Marine.

[pjShap]

Originally Posted by Jim Cate

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

Absolutely correct! The cross-section Ixx and Iyy properties are very sensitive to the section length and width, so be careful about even minor reductions in a replacement mast. If you find a mast that seems appropriate, you might be able to check its manufacturer's website to confirm its properties are similar to the Selden replacement you identified. Spreader placement influences the mechanical loads/performance, and additionally can impact your jib clearance, so be cautious if the spreader locations differ significantly.

[MicHughV]

Chotu,

Hope this works for you...this is the chapter on mast design from Skene's Elements of Yacht Design....might not be applicable to a cat, but may contain useful information for you..

Elements of Yacht Design - Page 118 - Google Books Resultbooks.google.com › books

[MicHughV]

you may have to copy and paste that link...but you will be able to download the pdf chapter on mast design..it has all sorts of graphs, formula's, etc....

[doog]

you are not engineering a mast installation. All you need to do is find a similar boat to your application with similar performance expectations whether it be racing or cruising motor Sailer or high-performance rig. the Mast from that boat will be suitable for your boat. I bought a used mizzenmast from a 50-foot nauticat and it served to beautifully as the main Mast for my 37 foot Roberts. it was headed for the salvage yard to be sold as aluminum by the pound and I got it for a song. Good luck.

[Buzzman]

A second-hand mast from a similar length mono, or even the same length spar from a mono, will probably not work on chotu's cat.

Multihulls have MUCH stronger sectional size and wall thickness due to the MUCH higher 'heeling loads' to which they are subjected. This is a 'rule of thumb' but tends to hold. Some racing boats may have fancy multiple diamond rigs with additional stays in order to limit sectional size (and thus weight of hamper aloft) but, **generally speaking**, multihulls have larger sectional-sized masts than similar length monos, or mono masts of similar length. They are usually of NACA-type profile as well, being much wider in the forward section than the aft. More like a wing profile, or a shortened, stumpy, wing profile...

He might have to get a longer mast, or a same length mast off a bigger, longer mono, that has the same sectional parameters as the Seldon 304 recommended, and then cut it down to suit.

The deck to boom height is not mission critical, as that can be added or subtracted by a good sheet metal specialist. I've done this to repair a break in this area, so it's doable.

But cats tend to have very tall, blade-like sails, so a shorter boom relative to the length of the main spar compared to monos with the same spar length. So boom will probably need to be shortened, and may not be the right profile, again due to the higher loads on the rig generally.

He knows the sectional parameters, everything else can be moved up or down the stick as required, and according to the rigging plan that came with the plan set. Assuming it did come with a rigging plan..??

But, yeah, finding something that will just 'bolt in'??? Nah. Not likely.

Finding something that can be made to 'work'? Very possible! Especially after the hurricanes in the Caribbean, for example. Damaged hulls will likely still have good spars, so even a 'cat specific' spar from a similar length, similar sail area cat might be do-able with some searching around, contacting boat yards and especially riggers in the area.

But moving long spars is not for the faint-hearted. I had to move the 8m (26ft) mast for my 6m Farrier over 1000km several years ago (bought one boat without a mast, and the mast from a different, rotted out hull). All sorts of regulations are involved, especially overall length, that might mean a 60ft mast is 'excessive length' so difficult to transport by road without (expensive) specialist transport. But mine was only 8m/26ft, so I lengthened a spare boat trailer I had, shifted the axle back a few feet, and thus complied with 'overhangs' restrictions, without exceeding 'overall length of combined tow vehicle and trailer rig' of 19m (my rig was less than 12m, as the mast overhung the towball by the max 1.2m allowed, thereby shortening the 'overall' some), and meant I did not have to lengthen the trailer as much. But I had to rig an A-frame to sit it on and keep it level and above 'car windscreen height' so no idiot speared themselves on it in traffic. Red flags, red-and-yellow corner markers etc etc. It was a lot of mucking about, but I got a 'cheap' mast as a result. About $2k landed at my place (so cost of mast, trailer mods, and return travel). Worked for my budget. 'New replacement' was over $4K.

As suggested up thread, might be easier to motor to the mast, having confirmed it is what you want.

[doog]

Just readnig quickly here since this is responding to me. I did say to choose a mast for/from a SIMILAR and COMPARABLE vessel and if this boat is a catamaran then this is the vessel it needs to be similar and comparable to, a CATAMARAN. not a monohull. Similar displacement and design and operation goals..racing, cruising what have you. Motorsailer or coastal cruiser or ...

How it is people can "disagree" with you yet not take the basic outline of what you actually said is a failure not of knowledge or opinion but simple language and logic, and it seems rampant in our time. The fabric of understanding itself seems to be falling apart at the seams..

Of course he needs a cat-rig..stressed accoringly but I persist that the engineering of wall thickness and alloy types and all the considerations are a design level issue addressed in manufacture and not an end user worry..All relevant considerations but youre going to find masts ID'd by what vessel they are installed on, find one with similar parameters and its design will be suitable. leave the wall thickness to the metalurgists..

[Island Time O25]

Some of the posts here remind me of a guy on this forum who awhile back was looking for a "Hunter cleat" for his 40 year old Hunter. Or was it a "Hunter winch"?

[betwys1]

Originally Posted by doog

Just reading quickly here since this is responding to me. I did say to choose a mast for/from a SIMILAR and COMPARABLE vessel and if this boat is a catamaran then this is the vessel it needs to be similar and comparable to, a CATAMARAN. not a monohull. Similar displacement and design and operation goals..racing, cruising what have you. Motorsailer or coastal cruiser or ...

How it is people can "disagree" with you yet not take the basic outline of what you actually said is a failure not of knowledge or opinion but simple language and logic, and it seems rampant in our time. The fabric of understanding itself seems to be falling apart at the seams..

Of course he needs a cat-rig..stressed accordingly but I persist that the engineering of wall thickness and alloy types and all the considerations are a design level issue addressed in manufacture and not an end user worry..All relevant considerations but you're going to find masts ID'd by what vessel they are installed on, find one with similar parameters and its design will be suitable. leave the wall thickness to the metallurgists..

Your response made me smile in sympathy . Here is a person with mast length, wall thickness, major and minor diameters (and presumably alloy) in hand, yet people will insist that finding a duplicate is not good enough; Ixx,Iyy, cat, not mono ....blah, blah, blah <g>
Agreed the furniture needs to be attached according to the plans to provide the desired stiffness etc.

[Chotu]

Originally Posted by betwys1

Your response made me smile in sympathy . Here is a person with mast length, wall thickness, major and minor diameters (and presumably alloy) in hand, yet people will insist that finding a duplicate is not good enough; Ixx,Iyy, cat, not mono ....blah, blah, blah <g>
Agreed the furniture needs to be attached according to the plans to provide the desired stiffness etc.

This is what I’m thinking from the start.

If you have an tubular object and know its length, both diameters in an oval sense and wall thickness, how are there any other parameters???

It’s a tube. LOL.

One thing I’m also wondering about is finishing off a random mast section.

How are the shroud tangs, spreaders, gooseneck and masthead attached?

[Buzzman]

Depends. Some are riveted, some are tapped and threaded for bolts/screws.

[Jim Cate]

How are the shroud tangs, spreaders, gooseneck and masthead attached?

Umm, Chotu, these are things that you should have well in mind before setting out on building a rig, whether new or second hand. Some are welded, some are riveted, some bolted or screwed... but these details are quite important and should be spelled out in the design. Are they not?

Jim

[Chotu]

Originally Posted by Jim Cate

Umm, Chotu, these are things that you should have well in mind before setting out on building a rig, whether new or second hand. Some are welded, some are riveted, some bolted or screwed... but these details are quite important and should be spelled out in the design. Are they not?

Jim

Planning them now, Jim.

Not sure what you’d expect?

I know you have tremendous experience cruising, but Have you built a boat? It’s an endless list of figuring out how to best do everything, then doing it.

It’s 1000 question and more time researching all the options to find the best approach than it is actually “putting hammer to nail”

You can bolt or rivet these things on, for instance. It’s nice to hear from a variety of people what their opinions are regarding that choice and maybe learn of an interesting trick or two.

I’m not afraid to ask all the questions in the world in order to perfect my knowledge.

Of course the plans have a rig. However, maybe I would prefer a bolted on gooseneck fitting as opposed to riveted because I want to remove the gooseneck someday. Maybe there are better ways to attach the tangs than the designer came up with.

[GRIT]

Originally Posted by betwys1

I can thoroughly recommend the gist of Paul's advice.
Surprised to see a Canadian (?) sneering at a sail boat *SO* much smaller than his (Ha!)

I like boats of all sizes, and if you took it as a sneer, then I'm afraid I've mis-worded my post, and offer my apologies.

That's not a sneer. It's simply fact, that smaller boats have more leeway as to what they can use as a mast.

The forces don't go up linearly, when you add length, then add another hull. To suggest that you can put on any old mast, on a 50 foot cat, or 50 foot monohull, is misguided.

I've, just this spring, assembled my mast and rigging myself. My previous boat was a heavy Corbin 39, and the rig on my new boat is humbling, as to it's complexity and robustness. The new boat weighs 66% of what the Corbin 39 did, and yet the rig seems twice the size. (Engineered by Selden)



Cheers.
Paul.