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]

Originally Posted by 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.

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?