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Mast Inspection Opinions

4045 Views 36 Replies 10 Participants Last post by GeorgeB, Mar 16, 2015

casey1999

Discussion Starter · Mar 4, 2015

Got the mast down to inspect and repaint. The fitting shown in attached pic looks to be 316 SS and is riveted (heavy stainless rivets) and through bolted (at the tangs used for forward and aft lower shrouds). This fitting clam shells around the mast and is fit perfectly to the mast shape. If not sealed well, however, water and salt could work its way between the fitting and aluminum mast and corrode- if that happened the mast could break as this must be a high stress point- seeing the mast is very firmly connected with 4 lower shrouds and a baby fore stay- a total of 5 connection points at this fitting with the addition of the spreaders. Note the spreaders do not pass through the mast- the spreaders fit into sockets in this fitting and held by one stainless through bolt (as shown in pic).

So request opinion- does the fitting look ok to leave as is and assume no major corrosion (note I can get a fiber optic camera and inspect the inside of the mast at this location- to make sure no corrosion through the mast wall)? Or would you recommend to remove the fitting? I would like to remove the fitting- but afraid I might open a can of worms and not be able to get the fitting installed as well as it is now- fitting might spring open on removal.

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casey1999

Discussion Starter · #21 · Mar 7, 2015

aloof said:
The inside of the mast is open to the air. Water, salt, and air are okay. The surfaces under fittings don't get enough air. Good primer, paint and some sealants keep the water and salt away while reducing electrolysis from the different metals.

Alloy aluminum used in masts is quite resistant to seawater if left bare and open to the air.

Booms usually break at the vang attach point because of the (foolish) use of stainless fittings by many rig builders. That wrap around spreader attachment is not one of the good ideas for longevity. Pretty and shiny though heavy, corrosion prone and complicated.

Stainless backing plates are also a terrible idea. Use alloy.

So instead of re painting my entire mast, I could strip all paint, buff it and leave it as is? Where fitting contact the mast, I would use proper isolation between mast and fitting to reduce corrosion.

GeorgeB

· #22 · Mar 7, 2015 (Edited)

Casey, a couple of thoughts. Wasn’t your mast originally anodized? You can check by looking down the inside of the mast and perhaps scratch it to uncover the bare aluminum for comparison. If you are going the polishing route like airplanes be prepared to buff to a mirror finish then apply wax. In a marine environment, you may be doing this every couple of years. (remember, the USAF used to keep their airplanes in bare aluminum while the Navy always painted theirs. Needless to say, I vote for prime and paint). Is the collar split at the mast track side? If so, it should be relatively easy to loosen it so it can slide off easily. Using silicone for galvanic isolation has been a pretty common rigging practice. I’ve never heard of 5200 being used (I admit that I haven’t heard everything yet

). Judicious use of an impact hammer will break any bond line. My biggest concern would be the galvanic corrosion holding the two parts together. Biron Toss recommends Ultra High Molecular Weight Polyethylene instead of Mylar to isolate larger galvanic surfaces.

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casey1999

Discussion Starter · #23 · Mar 7, 2015 (Edited)

GeorgeB,
I wish my mast was originally anodized, but it was always painted. Factory color was white, then painted red which faded in the sun. Yes, the collar is split at sail track- so maybe it can be bent slightly to breathe the bond- I may be able to use the lever arm provided by the two spreaders to bend slightly the fitting, if need be.

Good advice.
Thanks

GeorgeB

· #24 · Mar 7, 2015

I’ve always liked the traditional look of a white painted mast. The couple of mils of paint thickness will protect it from weathering without adding much of anything in weight. I work in the aerospace industry and all of our aluminum parts are completely anodized then any exposed surface is also painted for additional protection. One of my friends is trying to talk me into doing next year’s Pac Cup so perhaps we will bump into each other?

casey1999

Discussion Starter · #25 · Mar 7, 2015

GeorgeB said:
I've always liked the traditional look of a white painted mast. The couple of mils of paint thickness will protect it from weathering without adding much of anything in weight. I work in the aerospace industry and all of our aluminum parts are completely anodized then any exposed surface is also painted for additional protection. One of my friends is trying to talk me into doing next year's Pac Cup so perhaps we will bump into each other?

Ok, paint it is. Seeing you work in aerospace, what is your opinion of titanium chain plates? The environment here is so corrosive, it is something I am considering.

I should have the boat back in the water come summer, so if you are out this way for Pac Cup, send me a note- boat located north shore Oahu, if you would like to sail, I am sure you can teach me a few things.

VallelyJ

· #26 · Mar 7, 2015

So instead of re painting my entire mast, I could strip all paint, buff it and leave it as is? Where fitting contact the mast, I would use proper isolation between mast and fitting to reduce corrosion.

Stop.
Just drill out the rivets, slide the fitting up (with a hammer and drift if it's stuck). clean off any corrosion, separate the dissimilar metals, slide it back, pop in some rivets, and get on with life. Should take an hour or 2 and last another 38 years or until you sell it and buy a condo someplace. Perfection is the enemy of the good.

ccriders

· #27 · Mar 7, 2015

I started to say the reason for painting a mast was so that you can do it again in five years, but that's not really true.
When I owned a bicycle shop we frequently found severe corrosion where the stainless steel strap that holds the brake lever to the anodized aluminum handle bars. I remember one case where I pushed down on the bars and they broke away, held on by just a shard of aluminum. Look at a bike and you can see how sweat would accumulate at that juncture
creating a galvanic potential. I think this is exactly the situation you have with that SS collar around an AL mast.
Now, as to painting, when AL bike frames became very common, many had serious paint problems. As we now know paints that work on steel do not necessarily work on AL and sometimes large patches of paint will just fly off leaving a powdery aluminum oxide surface. Sometimes those riders, instead of painting their bikes, would polish them to a bright shinny finish which would last maybe a couple of weeks. I have not seen such a frame completely corrode through, but there were worrying indicators around welds, seat tubes and where parts were bolted to the frame. Today, painted AL bikes are very durable and last for years, but the paint process is very technical, probably not useful for painting a mast in the boatyard. So do some research on painting aluminum and follow the instructions and you should get a very satisfactory product.
Unfortunately, it's not going to be fast and simple. But then what is when a boat is kept in an environment like yours, and mine. The warm humid sea air rots everything and the best preventive measures only slow it down. A little.
John

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casey1999

Discussion Starter · #28 · Mar 8, 2015

casey1999 said:
On another site I found this comment:

"Some of the S&S 34's have a s/steel band at the spreaders with sockets for the airfoil spreader bars. Some of these where beautifully crafted from the guys at a Taskers. But 30 years of Ali in stainless and the spreaders might not be too flash. Here is a picture of some pullers I made to pull spreaders out of the sockets but in this case the spreaders where so corroded that the socket had to be split to get the rotten spreader out."

Luckily my spreaders are loose in the sockets, so they should pull out no problem. Curious as to how the poster got the fitting off the mast- I sent the poster and e-mail asking this question.

The poster also said he sanded the mast down to bare aluminum, polished and left that way with no painting. So what is the purpose of paint? Could I just remove all the paint and leave bare? After all the inside of the mast is bare aluminum and it sees water and salt- especially at the base.

Well so far so good. Had some time tonight to remove the spreaders from the stainless fitting/sockets. They came out without much difficulty. Worked back and forth while flushing with water. The spreaders looked good with only minor surface corrosion in areas, but about half of the original paint still intact. Interesting thing is that there was no sealant at all between spreaders and sockets. May be a good idea, as if there was sealant, and the seal broke at the top, the entire spreader could fill with water and not drain, leading to major corrosion. So maybe best plan is to coat everything with lanolin and not try to go for a water tight fit.

VallelyJ

· #29 · Mar 9, 2015

My sense of things is that the fit between spreaders and their sockets tends to be fairly loose. Probably any water that gets in will find it's way out. Although, with only half the paint left in there and some surface corrosion, obviously something's happening.
Maybe a layer of mylar around the spreaders inside the sockets, if you don't mind more unsolicited advice? It's not just the water, it's the dissimilar metals in direct contact.
If you lower your mast every couple years or so, the spreaders will be easy to pull, check and renew whatever you put in the sockets. Either way, you're wise to be looking at this stuff.

casey1999

Discussion Starter · #30 · Mar 9, 2015

VallelyJ said:
My sense of things is that the fit between spreaders and their sockets tends to be fairly loose. Probably any water that gets in will find it's way out. Although, with only half the paint left in there and some surface corrosion, obviously something's happening.
Maybe a layer of mylar around the spreaders inside the sockets, if you don't mind more unsolicited advice? It's not just the water, it's the dissimilar metals in direct contact.
If you lower your mast every couple years or so, the spreaders will be easy to pull, check and renew whatever you put in the sockets. Either way, you're wise to be looking at this stuff.

Here in Hawaii it is big money and a lot of my time and effort to take the mast down. Had a truck mounted crane to take it down an trailered it to my house to work on. Quite a job with a 43 foot mast. I don't plan to take this mast down again for at least 10 years. I would think lanolin would be good also. One thing is not good is to have water setting in a small space where capillary action keeps it there, as would happen in these spreader sockets and mast fitting. All in all I think the mast has held up well. It has done a circum-navigation, been knocked down with spreaders in the water, and is the same mast design as used by Jon Sanders, whom did a 360 degree roll in the southern ocean while on non-stop double circum-navigation.

VallelyJ

· #31 · Mar 9, 2015

I don't plan to take this mast down again for at least 10 years.

Then all bets are off. Good luck with it.

casey1999

Discussion Starter · #32 · Mar 9, 2015 (Edited)

VallelyJ said:
Then all bets are off. Good luck with it.

I would not say I need luck, I can tell quite a bit about rig condition by going up the mast and doing a close inspection. Interesting I would say this is probably the first time in 37 years the spreaders have been taken apart and structurally they look nearly new. Interesting also most of the wire and turn-buckles on the rig are originally. And the turn-buckles are of the tubular type that collect salt water and corrode with out you ever knowing because you cannot see inside- scary. I will replace all standing rigging and would plan to that in the future at 10 years or as needed based on inspection, or over stressed rig situations. In any case, there are risk to taking the mast down, a dropped or damaged mast could cost me $20k or more for rig replacement, so one needs to weigh the benefit of doing things. If I needed to shell out $20k, my wife would probably put an end to my sailing, as she would if I spent the money to pull the mast every two years.

casey1999

Discussion Starter · #33 · Mar 9, 2015

I got a reply from a sailor who has exact same mast:

"Removing the band around the mast at the spreaders was easy, Once the rivets are removed you can expand the band and slip it gently sideways off the mast. The fitting is quite flimsy it's self so try not to stretch it unnecessarily. If the spreaders are tight it would be best to remove them first so that the mast will retain the shape of the band whilst the spreaders can be wrestled out.
There was a little corrosion under mine but I'm not concerned, Just surface pitting, I was quite relieved when I cleaned it up. There was quite a coating of duralac on the stainless band and the mast was painted underneath it with paint and duralac.The paint had blistered under it. I haven't reassembled it yet but when I do I will probably paint the section under the band with a paint and duralac. I don't think I will seal it though as I would probably worry about trapping moisture in it.
The spreader sockets are also a trap for moisture so I may just drill a small hole at the bottom side of the socket so moisture can drain.
I still haven't finished the mast off yet. I might leave it until I get the boat back to the ocean so it doesn't get knocked around during transportation. All in all for a 30 year old mast it wasn't to bad, most of the corrosion pitting was simply from chipped paint, stainless steel fittings and fasteners. My boom on the other hand was quite bad with corrosion."

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casey1999

Discussion Starter · #34 · Mar 9, 2015 (Edited)

I am not familiar with Duralac, but it sounds like good stuff:

Here is where to purchase:
http://store.hamiltonmarine.com/bro...ive-joining-compound-tube-174515/4,33364.html

Product Description

Available in 115ml Tubes

Used in the Aerospace industry as an essential corrosion inhibiting material wherever dissimilar material are used.

Description Duralac is an anti-corrosive jointing compound for use between joints of dissimilar metals.

Form Duralac Jointing Compound is a yellow paste prepared from an elastic varnish medium of low moisture permeability, a corrosion inhibiting material barium chromate and an inert filler. It conforms to specification D.T.D. 369B.

Properties Barium chromate is only very slightly soluble in water and hence is not leached out of the joint even in the presence of a considerable flow of water. It is however readily decomposed by acids with the liberation of chromic acid so that it is brought into action only in the presence of corrosive influences. It is tough and flexible, absorbs little water and is resilient to seawater. Shelf life is two years from date of despatch. Store below 20°C.

Uses Duralac is indispensable for the sealing of joints between dissimilar metals of all types including magnesium and its alloys. It is also valuable for the protection of metals in contact with wood, synthetic resin compositions, leather, rubber, fabrics etc. When the components of a structure are of different materials, it is essential that the points or faces of contact should be treated with corrosion inhibiting materials because in the presence of electrolytes considerable differences of potential arise, not only where different metals are in contact, but also where components of the same metal under different stresses are in contact: for example as between the aluminium alloy plates or extrusions and rivets or bolts used in building up the structure, in industrial areas where structures are exposed, in flue ducts and acidic vapours. In close proximity to the sea where a salt laden atmosphere will be met with, structures will need the maximum attention to prevent corrosion due to the electrolytic cells set up by the salt laden moisture deposited upon the structure.

Application Duralac is supplied ready for use and must not be thinned. It is best applied by brush. When Duralac is applied to metal or other surfaces the volatile solvent evaporates and the compound sets to the touch, but remains tacky for a considerable period. It is important that the joint should be closed while Duralac is still tacky - so that it is in such a condition that it will flow sufficiently under pressure to close the gaps in the joint. It will harden somewhat if a thin film is left exposed to the atmosphere for a long period and this will prevent the making of a close joint.

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casey1999

Discussion Starter · #35 · Mar 16, 2015

I got the stainless band off. Not very hard- just drilled out the stainless rivets and gently pried away from the mast. Silicone sealant had been used and the bond was easy to break. The stainless band is in great condition and the mast good condition. One side of the mast had only surface corrosion and very little. The other side had quite a bit of corrosion and some pitting. I do not think the corrosion should effect the strength of the mast- although another 10 years probably would. The corrosion seem to be located where pockets of water were collected and held by the silicon caulk. Interesting there was no caulk at the front of the mast and no corrosion either. There was a compression tube in the mast- held in place by design and will not fall out.

Thanks for all the help on this. Sometimes the hardest part of a job is just starting the job.

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VallelyJ

· #36 · Mar 16, 2015

The corrosion seem to be located where pockets of water were collected and held by the silicon caulk.

I'd suggest not caulking the bottom edge as it's nearly inevitable that water will eventually find a way in and it will need a way to drain out.

GeorgeB

· #37 · Mar 16, 2015

The basic corrosion here is galvanic, which doesn't necessarily need water to propagate the corrosion process. You do need to mechanically isolate the two metals. I think that the original silicon isolator either wore or squished out giving you the mechanical contact that started the corrosion. Biron Toss recommends using UHMW film to isolate the flat surfaces and either Teff Gel or Locktite to isolate threads. Use Tef Gel on the pop rivets.

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