Sealing alu strut - still a no-no?

[merl]

Saw an old thread about sealing alu masts, and the consensus seemed to be that it is a bad idea.

Any new thinking on this?

[BWD]

Many people have done it without problems.
I bought a used Al foil with a mast sealed with what looks like a plug of epoxy putty. No problems so far.
Theoretically it would be best to use something that doesn't expand or contract with temperature change, and sticks very well to the aluminum to prevent moisture seeping up into the mast.
In practice, the mast is never in the water very long -usually just a few hours- and the temperature changes and expansion/contraction are relatively small.
If I sealed a new Al mast, I might choose a high-flex/lower modulus adhesive epoxy or more likely a polysulfide bedding adhesive like sikaflex or 3M 4200 or 5200.
Manufacturers have little motivation to seal them I think, since it introduces a possible defect, that they could be made to warranty, or lose goodwill and market.

[norcom]

One of my aluminum struts came sealed with some hard epoxy in it. The sealant cracked and is now letting water into the mast. I can still get most of it out by waving the mast up and down rapidly. One of these days I plan to drill it out and sealt it back up with some silicone or something that's flexible.

[Peter_Frank]

BWD, what is "small temperature changes" ?

If you mean the ones we experience often, maybe 25 °C (45 F) temperature span then you are right.

As in your car it is maybe 25-26 °C (77-79 F), and the water right now in the winter here is 0 to 1 °C (32-34 F).

In the summer, a hot car can get say 45 °C (113 F), if it is 21 °C outside (70 F)
If water is warm about the same 20 °C (68 F) then it is also a 25 °C (45 F) temperature span.

Whether that is a small change in temperature or not, is of course relative, agree

Wouldnt the best sealing be with a "cork" of some kind in the sealing (like the air screw in our windsurfers for flying) so easy to drain ?

PF

[edt]

I don't understand. I know for a SUP, it can explode, but a mast? it's pretty strong and should be able to handle pressure variations. What was the old thinking about sealing an aluminum mast?

[merl]

I was referring to what I found on the forum, in particular advice from Zeeko not to try to seal the mast. I think the problem might (mainly) be with foam and with inflexible materials. Eventually water gets in and is hard to get out.

http://www.kiteforum.com/viewtopic.php? ... ko#p960547

It sounds like using 3M 5200 flexible sealant (with some kind of foam backing) has worked well for some.

[davesails7]

Yeah, I think the concern is that water finds its way in, gets stuck in there, and causes corrosion. Not that the expansion will break the aluminum, but would cause gaps to let water in.

[edt]

ok. Well the slingshot mast is sealed how did they do it?

[Kamikuza]

ok. Well the slingshot mast is sealed how did they do it?

I think it's a "rubber" bung that goes all the way through. Seems to be standard

[opie]

My Takuma mast came sealed from the factory but now it has water in it that I can't get out. Maybe a fluke or maybe its not that easy to seal.