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  #11  
Old 11-06-2012
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Re: Mast Corroison and How to Evaluate it's Condition

Just for a nice exercise,

I've read in many places that masts are design to have an infinite life (Aluminum alloy masts, not wood masts). This is based on the alloy and the elasticity of the alloy/shape used. This is also based on ideal conditions (clean, corrosion free, correctly tuned stays, etc.). Only pure racing masts have a finite defined life. There masts are calculated based on life cycle versus weight. They keep shaving the mast design until it's cycles match what they think will be a minimum.

The stays and other rigging on the other hand typically have a finite life.

That is the problem dealing with a mast which looks to be distressed. It actually was designed to last forever, but will not due to real world conditions.

James L
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Re: Mast Corroison and How to Evaluate it's Condition

James,

It would be almost impossible to design an aluminium mast to last forever. Unlike steel (including stainless) aluminium does not have a flat lining fatigue cycle number, regardless of the size of the design. It is possible to extend the usable life but making it bigger and thicker, but since the fatigue curve doesn't flatline it can't be designed to last forever.

What I don't know, is what are the design specs that are typically used, and the expected design life of one.
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Re: Mast Corroison and How to Evaluate it's Condition

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James,

It would be almost impossible to design an aluminium mast to last forever. Unlike steel (including stainless) aluminium does not have a flat lining fatigue cycle number, regardless of the size of the design. It is possible to extend the usable life but making it bigger and thicker, but since the fatigue curve doesn't flatline it can't be designed to last forever.

What I don't know, is what are the design specs that are typically used, and the expected design life of one.
Greg,

That may be true, I'm just reiterating everything I have read about sailboat design. The authors may or may not be full of bull.

James L
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Re: Mast Corroison and How to Evaluate it's Condition

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Originally Posted by Brewgyver View Post
HighFly, that sounds like an AWFUL lot of money to put into a boat that age.
And the alternative is . . . . . ?

Avery, I have always held the view that the mast actually does very little work and that if your standing rigging is in good shape and serviced/replaced when required, the rig as a whole can be depended on.

Given that I'm not a wealthy sailor, I have always bought older boats, have had a few of them over the past 4 decades and have never had a mast come down, even in really arduous conditions. The only time I have had a rig threaten to fail was when wires/bottle screws failed first.

So corrosion and obvious physical damage (bends, kinks, dents) aside, one of the least important worries in my life is my mast.

Make sure your rigging is in good shape, fix the obvious damage by following sound conventional wisdom and then take a mental holiday.
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Old 11-06-2012
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Re: Mast Corroison and How to Evaluate it's Condition

Brewgyver,

Yes Sir, .. $ 30 K is a liitle salty. I was told not to buy a fixer upper in one of my 1st posts. I was just starting to look at boats to buy. I could have bought a more modern boat & needed next to nothing and just sailed away. I may not have a full $ 30 K in the boat. To be seaworthy and sail away needs rudder, small hole fixed & 2 bulkhead structures, 2 anchors, & misc. -- figure $ 10 K and $ 8,625.00 = $ 18,625.00 and on the water.

The other $ 11,375.00 buys creature comfort, modern nav., dingy w/ mtr., bimi top, swim ladder and all that. Some of the $ 11.6 k could have been added on to any boat I bought; and may not be counted (100%) against I-37.

Is the 1-37 worth $ 18.6 k on the water. I have checked & priced the I-37 from other boats for sale, figured $ 18.6 K was a fair deal. I paid $ 6.7 K for the boat and it had just had $ 20K spent (rebuild eng. & trans., etc., etc.) on it in the last 1 1/2 years. The biggest deal maker for me .. the boat was never negelected.. that I see. It does not smell and not trashed out. Most of all my stuff is old (60, 70, 80, 90's) so he 1970 Islander fits right in. I was in the 1/ 7 Air Cav in Vietnam when this boat was (1970) built. This was a wild & crazy time, we went water sking behind OH-06 Scout helicopters. I smile & laugh, was the best time of my life and worst too. Anyway, I'm into the I-37 (now) and my Son is setting it up as his 2nd man cave. now he can play his music there as loud as he want's. I mentioned earlier, this boat is a father/ son deal too. I look forward to sailing with him (next yr.) and looking for some big smiles (both of us) .

Avery
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Re: Mast Corroison and How to Evaluate it's Condition

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Originally Posted by Brewgyver View Post
HighFly, that sounds like an AWFUL lot of money to put into a boat that age.
Guess I'll just be my old DBA self. Go price a new 37' boat then come on back & tell us if it's worth it.

If 30K get's HighFly out on the water in a boat he wants for the 4 or 5 years he want's to float around, it's worth it.
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Old 11-07-2012
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Re: Mast Corroison and How to Evaluate it's Condition

Avery-
$750 for rudder repairs, this is the rudder that had the bottom two feet snapped off? I'd be surprised if a proper repair was that little, if there was no need to take it apart all the way and then completely rebuild it.
Just remember, if you lose the rudder while at sea, you've got big problems. That's one job you really want to make sure is 100% right.
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Re: Mast Corroison and How to Evaluate it's Condition

HelloSailor,

The $ 750.00 is parts & materials only, I'm doing the Rudder myself. The best price (rough est.) was $ 1,100 to $ 1,500.00 over the phone. I'll take it off and open it up and then make a decision (me or farm the job out). One thing (100%) the rudder that goes back on this boat will be as good as new.

Something I wanted to ask, were you connected with a Navy Air Wing (Carriers) in the Navy ? I thought that you were up on your air stuff and just curious. I had one trip on the Iwo Jima, assault carrier, in 1983. They used this ship for spec. ops and had a sub essort. The Iwo was put in service in 1943, I think that's the right date. We had a 2 week excerise and those (up/ dwn.) steel steps killed me. We had 48 hr. operations (12 Spec. Ops. Hawks) and my legs were hurting me & my back too.. Also, No booze for pain killers and that'a not fair.

Avery

Last edited by HighFly_27; 11-07-2012 at 08:34 PM.
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Re: Mast Corroison and How to Evaluate it's Condition

Just FYI - a few masts for my boat design (Pearson323) have had corrosion problems. The general fix is to cut out the rotted part, and build a riser into the mast step. This keeps the overall mast height/boom height/rigging as before. Oddly, I don't know anybody who used a sleeve.

Having the mast down does also give you an excellent opportunity to inspect/repair/repaint/put in fancy LED masthead and spreader lights. A rebuilt mast is a beautiful thing in an older boat....
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Re: Mast Corroison and How to Evaluate it's Condition

The problem with a sleeve is that unless it perfectly mates with the mast profile, it will fail from localized stresses. So even if the original mast extrusion is still available, the question is what profile matches it? Or, where do you find a tinker who will carefully hand-fit the new section to sleeve the old?

Far simper to cut off two inches, four inches, etc. and just put a taller mast step in the boat.


Avery-
1943...no, that predates me. OTOH I can neither confirm nor deny the presence of any nuclear weapons on board this vessel. (VBG)

I just can't help thinking there must be a way to use plastic (aka "engineered resin" or whatever you want to call it) and a CAD/CAM machine to turn a solid or hollow block into a one-piece rudder and post, with nothing to rot or break unless you sheer the post off. Beneteaus' idea (using a carbon-fiber rudder post and going all composite) sounds good, but then again there's that Airbus tail that fell off, made the same way.

Last edited by hellosailor; 11-07-2012 at 09:21 PM.
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