Mast Design 101

[Cheechako]

You should find a used aluminum mast and save some money. The specs aren't nearly as critical as many believe. In fact you see heavy crossections on small boats and vice versa. The specified cross section you mentioned seems small for a 41 ft boat. Sure, some things matter. The other thing is spreader placement (vertically) is not a huge thing either. I designed my own on the 31ft I built many years ago. I then took the design to a popular Naval Architect and paid to discuss it and have him evaluate it. It was a great discussion, and I learned a lot.. especially how little spreader location matters +/- a few feet.

[chris95040]

Originally Posted by zeehag

varnishing yearly is a dock queens luxury.
mine is painted and hasnt been repainted for 10 years.
yes it is in need.
the rough look now lets me be able to inspect the glue lines readily and feel the integrity of the wood. i plan on stepping and maintaining once i arrive in mazatlan, hopefully this year, as there is a location in which this is possible for lesss than many pay.
i like my spruce masts and booms, yes, hollow box with reinforcement blocks handily located, as they are repairable easily.
they do not suffer corrrosion nor electrolysis nor lignting attraction.
aluminum ones cost minimum 15000 usd new EACH plus booms, and are more difficult to repair. spruce is relatively rot resistant, and makes excellent masts. i have 2 of em. love em. just paint them if you dislike varnishing so much.

ps did i say that replacement of one boom made of wood here is less than 300 usd TOTAL, as opposed to the many thousands of dollars required for replacement of aluminum booms, each??

These are great points - and I do consider keeping the rig the way it is. But its a lot of weight aloft (600 pound rig in total, vs. 300 for one built around an aluminum mast) and the resorcinol glue seams are getting old, too. I keep it well tuned and haven't had a seam open up since last year, but the first few years I was chasing them down, opening them up further and gluing with epoxy. I imagine I'll be rebuilding the mast in the next few years if I keep it.

Ease of repair is another excellent point. Painting... I'd be too chicken, I want to see whats up w/ the wood. But again, a great counter to the "too much work" argument.

I think the mix of maintenance and improved performance, particularly upwind, with aluminum is whats really pushing me in that direction. Other owners have done the change and reported a significant improvement in stiffness. (On the other hand, they report that the roll is a lot less mellow with a lighter stick in the air.)

[Jim Cate]

Chris, don't be too concerned by the 'easier to repair" factor mentioned above. If you take normal care in assembling an alloy mast and boom, it will not need "repair" in the foreseeable future. Eventually sheaves will need lubing or replacement... just like those in a timber spar will. But the mast and boom themselves... probably never happen.

And whacking 300 lbs off the rig weight... wow, that should make a very noticeable difference in stiffness. Racers spend big bucks to shave a few pounds or even ounces off; they would be delirious with joy at the thought of 300 lbs!

Well maintained timber spars are handsome, but unless one is of the concours de elegance mind set, alloy spars make far more sense for a cruising boat IMO.

Jim

[Stumble]

Originally Posted by chris95040

I got a rough estimate for an aluminum mast at $10K USD. That's not including boom, rigging wire, etc.

I got a similar estimate for carbon, for $30K USD.

My thought was "wow, carbon is a lot more expensive. Forget that."

Now I'm thinking, I may have just gotten an insane quote. I wonder if you could point me to some suppliers? I love the idea of a nice lightweight carbon rig, even if it would be a bit strange on a CCA-era cruiser. Theres a guy in my boatyard with a 50 foot, triple spreader carbon mast that he can lift by himself. Really neat.

I think you more likely got an insane price on the aluminium rig. When we replaced the aluminium spar (only) on our 24' trimaran two years ago the extrusion including shipping was $12,000 ex VAT, IIRC. There is no way a mast for a 40' boat is going to be $10k.

There is a great blog https://www.morganscloud.com/2009/02...-and-benefits/ where they switched to a carbon mast. For their 41' Swan the price for an aluminium rig was $30k, and the carbon was $55k 6-7 years ago. Since then carbon prices have dropped aluminium has stayed about the same. Aluminium will still be cheaper, but the prices are moving towards each other. Getting hard prices for rigging is difficult, but when Tartan switched to all carbon masts for their boats they mentioned that the Tartan 40 mast was about $40,000 or about a $10,000 premium over aluminium.

If your current rig weights in at 600lbs (wow) figure an aluminium mast would be 300, and a carbon at around 200lbs. The effect on the boat would be startling. An absolute night and day difference in how stiff the boat is. That works out to be almost 12,000ft*lbs out of the rig, or like adding a one ton keel bulb to the bottom of the keel, or ten fat guys on the rail. It would be a huge difference in performance. So much so I would recommend having a rigger at least run the numbers to check everything.

[UNCIVILIZED]

Originally Posted by Cheechako

You should find a used aluminum mast and save some money. The specs aren't nearly as critical as many believe. In fact you see heavy crossections on small boats and vice versa. The specified cross section you mentioned seems small for a 41 ft boat. Sure, some things matter. The other thing is spreader placement (vertically) is not a huge thing either. I designed my own on the 31ft I built many years ago. I then took the design to a popular Naval Architect and paid to discuss it and have him evaluate it. It was a great discussion, and I learned a lot.. especially how little spreader location matters +/- a few feet.

On the used tube, I concur, as previously stated. Although when doing so, it helps to have a bit of rig design 101 under your belt.
That said, I can't speak to the conversation which you had with the NA. However, if you start doing the math on rig design, it becomes real clear that spreader placement truly does matter. That is, unless you Grossly oversize the tube. Meaning that you use one which is Ixx, & Iyy numbers far, far greater than what's really needed, based on the boat's stability.
In which case you're doing yourself a great disservice, with regards to both the boat's motion, & her performance/performance potential.

[Pauls]

Shopping around for your mast extrusion supplier can save you significant money. I'd recommend you check with Lefiell. They have a good selection of spars and I found their prices to be good.

[tenchiki]

One "contrary" thought: a heavier rig is more resistant to being rolled or pitchpoled by wave action in very heavy weather. If you are thinking of going that way.

[HappyMdRSailor]

Originally Posted by chris95040

I got a rough estimate for an aluminum mast at $10K USD. That's not including boom, rigging wire, etc.

I got a similar estimate for carbon, for $30K USD.

My thought was "wow, carbon is a lot more expensive. Forget that."

Now I'm thinking, I may have just gotten an insane quote. I wonder if you could point me to some suppliers? I love the idea of a nice lightweight carbon rig, even if it would be a bit strange on a CCA-era cruiser. Theres a guy in my boatyard with a 50 foot, triple spreader carbon mast that he can lift by himself. Really neat.

Out of curiosity...

Why would you spend 10k on an aluminum extrusion when you can buy one used for about $1500 with spreaders and wire???

There's 10ish that are about your length requirement on that ebay site...

[chris95040]

Originally Posted by Stumble

I think you more likely got an insane price on the aluminium rig. When we replaced the aluminium spar (only) on our 24' trimaran two years ago the extrusion including shipping was $12,000 ex VAT, IIRC. There is no way a mast for a 40' boat is going to be $10k.

That number came from Klacko spars. It was even (roughly) itemized. Its a 3/16" wall thickness, 9.65" x 5.9" section. I have heard numbers like $20000 from riggers.

Originally Posted by Stumble

If your current rig weights in at 600lbs (wow) figure an aluminium mast would be 300, and a carbon at around 200lbs. The effect on the boat would be startling.

That's what sistership owners tell me! Regarding consulting an NA, I think thats wise, but again, I'm guided by plans from Phil Rhodes which include both the aluminum and the spruce rigs.

Originally Posted by Jim Cate

Chris, don't be too concerned by the 'easier to repair" factor mentioned above. If you take normal care in assembling an alloy mast and boom, it will not need "repair" in the foreseeable future.

Originally Posted by HappyMdRSailor

Out of curiosity...

Why would you spend 10k on an aluminum extrusion when you can buy one used for about $1500 with spreaders and wire???

There's 10ish that are about your length requirement on that ebay site...

Because I want to hemorrhage money!!

I'm definitely exploring the used mast option. Got a few salvagers looking into it for me, and I'll check out ebay. The problem for me is when the mast is "*about* your length requirement": If its too short, thats no good. I don't want to redo my sail plan. If its too long, I'll have to relocate the spreaders after cutting it to size, possibly.

And if its used, I won't get that warm and fuzzy this-thing-is-bulletproof feeling.

But I'm definitely checking out whats out there.


Thanks for all the help, everyone! All these contributions are great.

[Cheechako]

Do a walkabout in Boat yards too. Often there are a few abandoned ones around. If your timing is good you may find some after a yard has cut up some abandoned boats before they sell the aluminum as scrap.

[rgleason]

Weight aloft makes a huge difference in stability. The alu will likely weigh less than wood, but get an adquate section but not too heavy, she will be much better in heavy winds and stand up. We have experienced this with S&S 46' 1945 wood vessel.

[Blue Stocking]

If I may ask, which of Phil's boat do you have ? By mast height, sounds like a Reliant or a Bounty. My Reliant 41 still has the perfect condition, 50 yr. old Douglas Fir, built-up stick. A number of owners who changed to Aluminum masts thought that the lighter weight changed the roll centre of the boat, to it's balance detriment.

[rgleason]

Yes the center of effort gets lower and radius of gyration changes. It is a stiffer faster boat IMHO.

[chris95040]

Originally Posted by Blue Stocking

If I may ask, which of Phil's boat do you have ? By mast height, sounds like a Reliant or a Bounty. My Reliant 41 still has the perfect condition, 50 yr. old Douglas Fir, built-up stick. A number of owners who changed to Aluminum masts thought that the lighter weight changed the roll centre of the boat, to it's balance detriment.

Reliant. What exactly do you mean by "to it's balance detriment"?

What I've heard is basically that the boat gets stiffer, you can reef later, and make less leeward motion when fighting upwind.

As a negative, although the rolling motion traveling downwind has shorter distance with less mass aloft, it also has faster speed, which is likely less comfortable.

[Matt Johnson]

opps.... double post.