[casey1999]

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.

 

[Barquito]

I will be interested to hear what the experts think about this. Looks like there is corrosion at the interface. I assume there should be some kind of dielectic material in there that could be replaced. 'Can of worms', is the biggest impediment to getting DIY projects done. It is also what keeps us from getting in over our head.

 

[Jaramaz]

Well ... there is already a lot of info available on SN. Boogie Nights, who posts here far too seldom, has a homepage which describes this:
Boogie Nights

Usually not much to see from the outside, but open the can of worms and you will see. OPen ing is recommended.

/J

 

[casey1999]

I will be interested to hear what the experts think about this. Looks like there is corrosion at the interface. I assume there should be some kind of dielectic material in there that could be replaced. 'Can of worms', is the biggest impediment to getting DIY projects done. It is also what keeps us from getting in over our head.

Yes you are correct, there is a slight amount of corrosion where the fitting meets the mast (top and bottom). I looked at this corrosion carefully and it looks cosmetic- only on the surface. The mast is fairly thick- guessing about 1/8 inch. There was another fitting original to the 1978 mast and it was bed with clear silicone. At the edges of the fitting there was some cosmetic corrosion, but under the fitting, the silicone and original white mast paint were in near new condition. From what I hear of the original boat builder, he did things as best as he could- no cutting corners, so I am nearly certain there is at least silicone bedding under this fitting.

When I say opening a can of worms- I refer to getting the fitting off, but not being able to get it back on nearly as well as it now fits. I might also fatigue weaken the fitting by trying to open it up to get it off the mast- as it now fits like a glove. In other words- I make the condition worse than what it is now, and as it is now may be perfectly fine for another 37 years of hard use.

 

[casey1999]

Well ... there is already a lot of info available on SN. Boogie Nights, who posts here far too seldom, has a homepage which describes this:
Boogie Nights

Usually not much to see from the outside, but open the can of worms and you will see. OPen ing is recommended.

/J

I skimmed some of that sight- found nothing on masts- could you give me date or location of the reference?

 

[casey1999]

BTW, the spreaders will be removed- only one bolt holding- they are somewhat loose in the socket- but still strong. Probably be some surface corrosion at the socket- will repaint.

 

[casey1999]

Well ... there is already a lot of info available on SN. Boogie Nights, who posts here far too seldom, has a homepage which describes this:
Boogie Nights

Usually not much to see from the outside, but open the can of worms and you will see. OPen ing is recommended.

/J

Idiom Definitions for 'Opening a can of worms':

"If you open a can of worms, you do something that will cause a lot of problems and is, on balance, probably going to cause more trouble than it's worth."

 

[ccriders]

On the other hand, will you ever sleep well at night having not opened it up and confirmed its condition? And you know what assume means don't you? When the mast is down is the time to confirm its condition, not hanging from a bosons chair.
John

 

[MarkSF]

If you're worried, drill out the rivets and take a look. Just use a good sharp drill, low speed, high pressure, and lots of coolant. Replace the rivets with McMaster Carr high-strength rivets.

 

[ambianceack]

I would remove the unit too, using the technique MarkSF describes. Is it possible to slide the sleeve up or down the mast for removal rather than spreading it apart; or is there too much hardware in the way. If you are planning to paint the mast you will want to remove the hardware anyways. Then reinstalling all the hardware you can properly deal with preventing any future problems with galvanic corrosion between the different metals (aluminum and steel). Another thought if you do not want to use the rivets is perhaps a couple of pan head screws. Possibly using 4 screws drill and tap new holes. It seems like the rivets only help to in place whereas the thru-bolt is doing the majority of the work. I do not think you would be opening a can of worms, you are just taking on a preventative maintenance project. Do it one step at a time, take pictures of your removal and label everything to help stay organized for reinstalling.

 

[VallelyJ]

I wouldn't hesitate to pull it. Contact between aluminum and SS is obviously fertile ground for galvanic corrosion. I'd worry more about that, given the large area of dissimilar metal contact, than about having to wrestle with the fitting to get it back on.
And I doubt seriously you'd have to do that. The SS isn't likely to spring out of shape after having been held there since the Gerald Ford administration. The fastener holes will position it correctly, and some c-clamps padded with wood, or a similar device, should get it in place if you even need them. And I'll bet you won't.
You could always pull fasteners a few at a time on one side to see if there's any resulting movement or malformation.
The through-bolts might go through SS compression sleeves inside the mast. These tubes keep the bolts from deforming the aluminum when tightened. So when you pull the bolts, follow them out with a stiff wire, screwdriver or pin of some sort to keep the compression sleeves from falling out of position. An easy operation. There also will probably be some structure inside the mast to keep the spreaders from squeezing the mast walls out of shape.
I pulled all the SS fasteners from my mast, coated each one with Tef-gel and re-installed. The tef-gel provides some galvanic insulation between the 2 metals. Lanocote does also. Screws tend to freeze in place over time without that.
You can galvanically insulate the fitting from the mast by sandwiching a sheet of mylar under it.
But I'd definately pull it off. I know that's easy for me to say, but the guy who assembled it in '78 probably wasn't a lot more skilled than you are.

 

[casey1999]

Ok looks like consensus is to remove the fitting. Will do and post some pics of underneath. As suggested, might be able to slide the fitting along the mast- that might have been the way it was originally installed. I think this fitting takes the compression of the spreaders. The pic does not show but it wraps nearly around the mast and is about 8 inches long along the length of the mast, quite a robust piece of stainless.
Regards

 

[Jaramaz]

I skimmed some of that sight- found nothing on masts- could you give me date or location of the reference?

Oh, the link did not link all the way. However, there is a clue in the link, it ends with "this game is rigged" (english humor ..) which also is the name of the chapter. Think it is dated "20th May".

Anyhow, Jayne has a Dehler 36. The mast is in Alu, and ss fittings. On the advice of a rigger she did remove the ss things and found some lack of Alu where it should have been. She got a new mast.
It is a good read for all those having an Alu mast with ss fittings.

This is the problem with ss fittings on Alu. One usually doesn't see how bad it is without removing.

/J

 

[casey1999]

I would remove the unit too, using the technique MarkSF describes. Is it possible to slide the sleeve up or down the mast for removal rather than spreading it apart; or is there too much hardware in the way. If you are planning to paint the mast you will want to remove the hardware anyways. Then reinstalling all the hardware you can properly deal with preventing any future problems with galvanic corrosion between the different metals (aluminum and steel). Another thought if you do not want to use the rivets is perhaps a couple of pan head screws. Possibly using 4 screws drill and tap new holes. It seems like the rivets only help to in place whereas the thru-bolt is doing the majority of the work. I do not think you would be opening a can of worms, you are just taking on a preventative maintenance project. Do it one step at a time, take pictures of your removal and label everything to help stay organized for reinstalling.

Good advice. The only thing I am concerned about is getting a water proof seal on the entire area where the fitting contacts the mast. Insulating Mylar may keep the aluminum from contacting the stainless, but how to keep water and salt out of this very small gap? Depending on what the builder used, I might have a hard time getting the fitting to even slide if he used silicone or say 5200.

 

[VallelyJ]

If it sticks after you remove the fasteners, it could be the sealant or it could be corrosion. Either way, when you replace it, just a simple bead of polychloride sealant, like 3m 4200 around the top ought to seal it. If you just seal it around the top, any water that gets in can get out. Polyurethane sealants like 5200 are good only if you never plan to move the part again. I wouldn't spread sealant on the mast under the fitting, as that will also make future inspection difficult.
But you could also consider coating either side of the mylar with Lanocote, so moisture has no place to go, as long as you don't clean it off where you want the bead of sealant to stick. In fact, with a coat of Lanocote, the mylar might be redundant. But it's your mast, corrosion will stay hidden, so for what it's worth, I'd go with redundancy.

 

[ambianceack]

I agree with ValleylyJ. The Lanocote sold by Forespar should be sufficient to help thwart electrolysis. Not sure if you can climb your mast but my thought is that applying the bead of 4200 or similar product (IMHO stay away from 5200 for that joint) after the mast is stepped might be better since the current bend in the mast, now on ground supports, is likely the opposite bend when stepped so the caulks seal will likely break when the mast is stepped. Also you probably will never keep water out of that joint due to all the flex in the mast when sailing, so the bead of caulk on the joint between the mast and the support piece may prove useless. I would do a good paint job and use the Lanocote. Then complete a visual inspection annually and do a full check every other year or so by simply sliding the support the distance of its own height. as far as removing currently, you will likely need a nail set, a awl or a some sort of punch to move those rivets all the way into the mast or drill through entirely but you will likely oversize the holes. If you end up needing to tap the support piece use a hard plastic hammer head and a block of wood to keep from marring the metal. warm water might be a good solvent to help break the electrolysis if stuck, my thought here is "likes dissolve likes."

 

[VallelyJ]

Good idea re running the bead of caulk after the mast is stepped, if you can get up there. If you can't, put a block under the mast at that fitting to minimize sag between the sawhorses. The amount of mast flex over an 8" length has to be negligible, and polysulfide sealant remains flexible. After all, any substrate on a boat is bound to flex.
Either way, don't leave it out. Water that can't dry will be your biggest enemy in that spot. Might as well keep out what you can.

 

[Dave_E]

Drilling out the rivets should be a no big. Clean the fitting, sand down the corrosion, treat, repaint, put it back together.

 

[casey1999]

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.

 

[aloof]

...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.

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.