stainless steel mast?

[turedogan]

Hi,
I'm building Roberts 434.She is nearly finished.I want to build 16m stainless steel mast.Is there anyone trying this before and how.Thanks.

[Buc]

Why? That's a lot of weight.

[turedogan]

Stainless steel is looking better,shining etc.It is very resistant above water.I don't think it's density is so much bigger than galvanized steel.It is stronger than others so the sheet which is used by rolling to a ellipsoid tube will be thinner.3mm is enough ı think.

[MikeJohns]

turedogan

Stainless is a poor material for anything that repeatedly flexes, so to make such a mast stiff to reduce fatigue fracture would require a lot of weight either in the wall thickness or the staying arrangement. Masts tend to have a lot of movement and I can see fatigue (the bane of stainless steels particularly in a wet salt environment) plaguing such a mast.
Cheaper and more sensible to use anodized marine grade alloy masts if you want a nice clean and shiny finish. Otherwise if you really want a a steel mast then painted Galvanised mild steel is the best option.

[turedogan]

Thank you for your advertisement Mike John
s.Best regards.

[marshmat]

The rapidly changing loads in a mast means that stainless steel, which is very stiff and fatigue sensitive, probably isn't your best bet. All that weight high up certainly doesn't help righting moment either. A marine-grade aluminum alloy is probably the most common and, for most boats, the best option- it's cheap, light, can flex enough that fatigue isn't a huge problem and doesn't readily corrode.

[solrac]

an alternative to "rolling" a metal sheet (I can't imagine how to "roll" on a longitudinal axis something that is about 15/20mts lenght...) might be to "compose" by welding some aluminium tubes & reinforcements to an adequate shape. I realize it's not the ideal shape, but can be a nice aproximation.

[turedogan]

Not in one piece.In a factory ,6 or 8m long pieces can be rolled and weld end to end.Steel or alloy,they said they can do.

[turedogan]

I forgot to say that each pieces are being a half of an ellipsoid.

[RHough]

Hi,
I'm building Roberts 434.She is nearly finished.I want to build 16m stainless steel mast.Is there anyone trying this before and how.Thanks.

I think it would be wise to follow the designer's recommendation for the mast. I doubt that the design provided for a steel mast (stainless or otherwise). There are many aluminum sections to chose from and the engineering has been done.

Have you gone far enough to know how a steel mast compares as far as weight per foot and moments of inertia to an aluminum mast?

[Buc]

Others have said it. You can buy a stock aluminum extrusion for far less than the cost of custom rolling and welding stainless. And note that not all SS lives well in a marine environment. A soft anodized aluminum spar will be silver, though not as shiny as stainless, and weigh substantially less. It will also flex more readily, desirable in a mast.

If you really insist on shiny, consider titanium. Cost will be an object, of course, but it polishes up really nice, flexes well and will be even lighter than aluminum. It's a witch to weld, though. The American 12-meter Weatherly had a mast with the upper third made of titanium.

[gggGuest]

Yep, a titanium mast would be cool. I've got Titanium spreaders on a mast at home: it completely foxed me what they were because the colour and sheen was reminioscent of stainless steel but the weight certainly wasn't. Admittedly cost wise we're talking about ten times or more the cost of a carbon fibre mast, let alone aluminium, but hey, money isn't everything!

[gggGuest]

To my suprise I've discovered that there have been stainless steel spars on a fully professionally designed sailboat. It seems that the Jubilee Sailing Trust's 5m 3 masted Square Rigger Tenacious has them. Rather a different beast though.

http://www.jst.org.uk/frames/index.php?pages=page1041

[mattotoole]

I seem to recall reading about Ti spars on some racing boats back in the 70s. Am I correct, or dreaming? Who would build such a thing today?

Polished Ti would be neat, but I shudder to think about the cost.

I can't imagine trying to maintain a stainless steel mast, to keep it all looking nice. No steel is perfectly stainless. Anyone with a boat knows this.

[turedogan]

Sorry for being silent for along time.By your guidence I undestood that the best methods for building a mast are ''alloy'' or the designers choice ''wood''.Can I built a hollow wood mast as the designers description and after encapsulate it with fiberglass diagonally?How many layers of fiberglass that I can use?

[Buc]

Yes, you can certainly build a wood box mast. It's how masts were built for years. The box will be stronger than a solid mast of the same dimensions and, obviously, mugh lighter. Fiberglassing isn't really necessary, though it would reduce maintenance somewhat. It would also increase the weight. As the glass is primarily for protection, use as few layers as possible; one would be fine.

As for titanium masts on racing boats, I made reference earlier to Weatherly's mast with the upper third made of Ti. Its use was outlawed by the IOR for cost reasons, but Weatherly's mast was grandfathered when she went from being an America's Cup 12-meter to racing in the Pacific Northwest.

(I remember helping the IOR measurer drag the main back to a position aft of the mast for the flotation measurements. It was a two-ply dacron sail and too heavy for both of us. We got it to the front side of the spar and called it close enough. That would have been in about 1972-73.)

[gypsiemarine]

Mate, go down to the marina and have a look at all the masts. 95% aluminium and 5% wood. There is a reason for this.

[DanishBagger]

Mate, go down to the marina and have a look at all the masts. 95% aluminium and 5% wood. There is a reason for this.

Yup, that reason is extruded aluminium, resulting in easier mass production :P

[CORMERAN]

To TUREDOGAN:

The Designer is on the right track - as far as I am concerned.
If wood came out of a lab. it would be called a "wonder" material.
It will endure many more flexing cycles - than most metals.

- The amount of fiberglass is not the first concern.
- Consider that: - fiberglass resin is POROUS.
- Whereas EPOXY is not.
- Also the glass does not have as much fatigue resistance as the woods
preferred to make masts. So - long term it's not really adding much strength.
- To me, the main function of the fiberglass, is to help build up a thick
layer of epoxy. Which is doing the most work in maintaining the
longevity of said mast.
- Also, the glass gives abrasion resistance.

However, be warned.
Making a mast requires diligence and skill. A small flaw has generaly,much greater consequences - than a similer error in the construction of the boat
it's self.

There are good reasons why marinas are filled with boats with
aluminum masts. It's really a challange to do as good a job as the professionals.

[glenville]

My brother recently built a mast for a 34 ft. sailboat using layers
of fiberglass outside a mold. Its not been sailing yet but seems
plenty strong and relatively light. He can sit on the 40 ft mast when its
sitting on workbenchs at the ends!

I'm finishing a Roberts 31 and have a 47 ft alum. mast I'd like to cut down
to size but think it might be to heavy in the end. It's aprox 6x8 in.. Anyone
have any thoughts on cutting shorter an aluminum mast?

mark

[FAST FRED]

Anyone
have any thoughts on cutting shorter an aluminum mast?

No problem although you will need to relocate the spreaders for the new overall hight, as well as any lower shroud or inner forestay mounts.

No big deal. The slightly heavier mast section may even give a better ride than a super lightweight mast .

FAST FRED

[CORMERAN]

To GLENVILLE:
Re: Fiberglass

Yes, one can make a case for fiberglass masts.
They are actually very common.
Although, many people will not have noticed, as they are covered up
by the sleeve of a WINDSURFER'S sail.

However, please note:
Technicaly, the top of the line, windsurfer mast is very sophisticated.
It is vacum bagged - over a steel mold - and cured by hot steam being
injected INSIDE, said mold.
The resin often used is: air craft grade, epoxy.
If memory serves, the carbon fiber masts made this way, have 18 layers of carbon, within only a 1/4 " of wall thickness !
So dense, that if you drop one on the shop floor - it will a make ringing sound
- just like metal will. - And one suspects, will also transmit electricity.

Cutting down a mast - moves one, closer to an off - shore cruiser. A good thing, from a safety point of view, many will agree.
- In terms of you ending up with the new mast, being, in theory
- a bit more heavy than ideal.
I would, personaly, cut off - the heavier, bottom end of the mast. That is,
if the mast you have, is tapered to any significant degree.

What ever you do - it is advisable to make use of a Marine Engineer's
services.

As I've stated - small errors, in mast constuction - can have major consequences.