Rebeding fittings. Best practices?

[Snowpetrel]

I've finally pulled the mast. Its nearly stripped of all fittings, and after removing all the flaking paint I'll rebed the fittings, provided I find nothing to nasty underneath them.

I've always beded them on Duralac and plastic sheeting. Is there a better way? What about using sikaflex or similar sealant, or lanolin?

Duralac vs Tefgel, I am thinking tefgel might be better for fastenings. Any other options?

The mast currently has a mix of heavy monel rivets and metal threads securing the fittings. Whats going to be better, or should I go for something else like rivnuts?

I will most likely leave the mast completely bare after stripping it. Any ideas on the best way to sand and protect the aluminium, is something like Hemple alu-protect any good?

[Jentine]

Coating the mast with paint is a cosmetic application. You can strip the mast and do nothing. Like aluminum boats, no coating is necessary because it will oxidize and that will be the protective coating.

[Copacabana]

I picked up some free off-cuts of windscreen tinted film (Mylar), which I use under fittings on the mast to keep SS isolated from aluminium. This doesn't isolate the threads of the screws used to fix the fittings, but that's what Tefgel is for.

[Wotname]

Originally Posted by Snowpetrel

I've finally pulled the mast. Its nearly stripped of all fittings, and after removing all the flaking paint I'll rebed the fittings, provided I find nothing to nasty underneath them.

I've always beded them on Duralac and plastic sheeting. Is there a better way? What about using sikaflex or similar sealant, or lanolin?

Duralac vs Tefgel, I am thinking tefgel might be better for fastenings. Any other options?

The mast currently has a mix of heavy monel rivets and metal threads securing the fittings. Whats going to be better, or should I go for something else like rivnuts?

I will most likely leave the mast completely bare after stripping it. Any ideas on the best way to sand and protect the aluminium, is something like Hemple alu-protect any good?


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Dunno the answer to Duralac vs Tefgel

IMO, you can't beat heavy monel rivets, all rivnuts I have seen corrode or work loose; of course there may be better ones than what I have seen.

Best coating for an Al mast is - air! At least according to Taskers when I asked them for best practice a few years back. They made good money painting masts and did a great job but they advised that the only reason to paint a mast is cosmetic; an unpainted mast will last longer than the best painted one.

[Snowpetrel]

Thanks Wottie and all, good to hear about the rivnut issue, and all the monel rivets seem very good, no corrosion around them, and easy to drill out. Certainly much easier than the metal threads...

Whatever they did worked well. Only minor surface corrosion under the removed fittings so far, and the mast is about 34 years old with no sign that it has been stripped before.

The mylar film idea is good. Ive used icecream container lids, and was thinking those thin plastic cutting boards might work, though the reduction in friction may increase the loads on the fastenings.

Seems like a bare mast it is. I'll need to experiment with the right sandpaper grade. Thinking 120 then 240, with a final wet and dry 800 or so or a polish if it needs it.

[Dsanduril]

I have used a number of plastic sheet materials under fittings on mast and boom, and then a rigger friend suggested PVC pipe wrap tape. Generally 10 mil thick (which is plenty) and self-adhesive, so you can put it on either the fitting or the mast and it stays in place while you deal with fasteners. I prefer to put the tape on the fitting, then I can trim around the edge of the fitting with a razor blade before mounting. I've also tried it on the mast, but difficult not to score the mast a bit when trimming and I'd just rather not have a scratch right where corrosion might be an issue.

2"/50mm is pretty common at the big box stores, 4"/100mm should be relatively available, generally at plumbing supply places.

I have also been using aluminum oxidation paste from the electrical industry rather than Tefgel for going on 20 years. My fasteners come out clean and I've seen no corrosion where I use it. Intended for dissimilar metal connections (copper to aluminum) in the electrical industry it is not marketed at all for this use so up to you if you like the idea (kind of like a doctor prescribing medicine for off-label use - some of them have good experience and knowledge but you do need to use care in evaluating).

[Snowpetrel]

^^ Thanks. Both very good suggestions, and I'll see if I can find some of that tape and paste. The pipe tape also seems perfect for covering the dynex dux backstay to prevent UV and chafe damage.

[Dsanduril]

Originally Posted by Snowpetrel

^^ Thanks. Both very good suggestions, and I'll see if I can find some of that tape and paste. The pipe tape also seems perfect for covering the dynex dux backstay to prevent UV and chafe damage.

Unfortunately I've found that the adhesive isn't that good. I, too, thought it might be a good heavy tape material but it seems to come undone rather rapidly when exposed to sun and water. Could depend on brand/version I suppose. Doesn't matter when it is trapped between fittings, but wrapped around something.... My experience anyway.

[Snowpetrel]

^^ ahh well, thanks for the heads up. Probably just go back to using white electrical tape. Seems to hold up resonably well. Just have to replace it every few years.

[GordMay]

Originally Posted by Dsanduril

... I have also been using aluminum oxidation paste from the electrical industry rather than Tefgel for going on 20 years. My fasteners come out clean and I've seen no corrosion where I use it. Intended for dissimilar metal connections (copper to aluminum) in the electrical industry ...

Indeed; electrical (Cu-Al) anti-oxidant joint compounds like Ideal NoAlox, Burndy Penetrox, Gardner Bender (GB) Ox-Gard are all excellent in this (and other) anti-oxidation applications.
I slightly prefer Penetrox, as it's slightly "thicker" (less runny) than the others.

[Snowpetrel]

^^ Thanks Gordmay, those brand names are going to be useful seaching for them here in aus. Looks like good stuff to have onboard anyway for electrical work.

[Wotname]

Originally Posted by Snowpetrel

...........
Seems like a bare mast it is. I'll need to experiment with the right sandpaper grade. Thinking 120 then 240, with a final wet and dry 800 or so or a polish if it needs it.

I'd probably stop at 400 (used wet) but that's just me. Really depends on the final finish and your willingness to do the hours required for a super fine finish.

There are probably suitable buffing / polishing pads, tools and compounds as used by car detailers etc that would work for an Al mast but I am just a hand sanding sort of guy

[Snowpetrel]

I like the sound of 400 much better than 800. As long as it isn't going to look all swirly from the dock. If I leace it bare it should quickly dull into a nice grey patina anyways. Suits me perfectly.

[Wotname]

Originally Posted by Snowpetrel

I like the sound of 400 much better than 800. As long as it isn't going to look all swirly from the dock. If I leace it bare it should quickly dull into a nice grey patina anyways. Suits me perfectly.

I have always thought naked Al spars look way better on a proper cruising boat than a painted ones - especially when the paint starts getting a bit old.

I understand some others like paint but not me

Swirly indicates you are planning to use tooling when sanding; if so, penultimate tool should be a random orbital sander and then hand finish (wet) longitudinally along the mast. IMO, it will look a million dollars

EDIT: if it gets tiring, concentrate on the couple metres closest to the deck. No one can see much above the first set of spreaders

[Snowpetrel]

As long as it doesn't take a millon hours, looks vaguely ok from 10 feet and isn't going to corrode away into a pile of aluminium oxide I'll be very happy.

Sanding wise thats pretty much my plan. But it will evolve as I go. The bottom panel can be a bit shinier than the upper ones.