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Go Back   SailNet Community > On Board > Gear & Maintenance > Hairline crack on mast
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Thread: Hairline crack on mast Reply to Thread
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Topic Review (Newest First)
07-27-2010 09:37 PM
scraph I agree that no mast is watertight.

I'm wondering where the dissimilar metal interface is occuring because ... with a steel ship and an aluminum mast it has to be happening somewhere. The photos show the remnants of some sort of enamel coating on the interior of the mast step. Maybe the step is steel and the insert is aluminum. Either way ... if the mast step insert is aluminum as well as the mast itself ... it is rather bizarre for alumina to be building up so aggressively. It should form a hard passivation layer and cease. Maybe ... there has been sufficient motion between the mast and insert to continually form, remove, and re-form aluminum oxide at that interface. I'd like to know whether the damaging corrosion is reduction on the insert or mast.
07-27-2010 08:01 PM
Gary M Welding is the simplest solution, any tapered mast is welded, it is a very common practice. You do need someone who knows what they are doing of course.

Good Luck
07-27-2010 06:29 PM
mitiempo I think it is cast aluminum, as is common with many masts including mine. The deckbase is probably aluminum as well or one of them would be totally destroyed by now. Welding might make sense if it can be done without distortion, by someone who welds aluminum regularly.

ps No mast is watertight from the top I don't think.
07-27-2010 01:22 PM
scraph Providing the mast is water tight? Or the reinforcement "jacket"?

I have no personal experience welding aluminum ... if those cracks can be cleaned and filled with weldment, absolutely. I imagine then it would make sense to really clean up those cracks. Grind a nice, clean channel in their place with a smooth radius at the termination.

It sure looks like that step insert though is a cast piece of carbon steel. That bothers me. I'd much prefer a billet of stainless milled to shape.
07-27-2010 11:57 AM
TQA Hey guys it is at the base of the mast. Masts don't break there. I absolutely agree that it is corrosion related damage where the expansion has caused the "weld lines" produced during the posrthole extrusion process to crack.

But I do not see the need to shorten the mast. Get the base out clean it up get a GOOD ali tig welder to weld the cracks and then refit the base. Winding some carbon fibre / kevlar string and epoxy coating the base can not hurt from a strength point of view providing the top is water tight. But I think I would not bother preferring to leave it so that I could make a regular visual check on the welds.

A raised mast step would work too but I suspect the cost would be higher. Mind you it is a steel boat so a raised step would be easy to do. ?
07-27-2010 10:50 AM
scraph I agree that cutting the affected portion of the mast, reinstalling the mast step insert and having a riser for the mast step fabricated and installed would be a good solution.

You might also want to attempt to determine the cause of this destructive corrosion and solve it before it happens later on down the road. Maybe you could do a hard powder coat to the insert and step to insulate them. Maybe also drill small drain holes at the base of the mast (I imagine water has pooled up on top of the step insert to accelerate this corrosion). If the component that is corroding is the step insert (instead of the mast itself) you could have a new one fabricated of a superior material.

I agree with all that the mast should be cut short and saved. The mast step and all involved components appear to be of dissimilar metals and also not very corrosion resistant. You might seek the advice of a local engineer or machinist on a better solution to the materials.
07-27-2010 10:15 AM
mitiempo It would probably have to be fabricated out of aluminum or stainless. Best to get it done locally I think.
07-27-2010 01:59 AM
WebSurfer3000 Thank you all for all the good ideas.
Does anyone know where I could order a raised step as suggested that I could rivet the mast on plus a collar for extra safety? (The piece must be able to be shipped to Cyprus in the med where the boat is on dry dock!)
07-26-2010 11:31 PM
mitiempo I wouldn't think there is much taper at the heel of the mast.
What about doing what CaptainForce suggested but instead of shortening the rigging raise the step on the deck by the amount you cut off the mast.
07-26-2010 05:32 PM
cormeum looks like someone tried drilling the mast to arrest the cracking already. you need to pull the insert whcih is probably where your problems lie. when that's addressed, welding a band on the base probably would only cost a couple of hundred- if the crack progresses the price to fix it mounts.
Capt. Force's solution is a good one too (if there isnt too much taper to refit the step)
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