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I’m redoing my 31B and I want to add a hard top half tower.
Should I go with stainless steel or aluminum?
I was thinking about 1 1/2 inch tubing. If I go with aluminum I wont be able to get it anodized because I’m in Cabo San Lucas Mexico and there are no faculties around here that can do it. Best I can do is powder coating or painting it every few years. Is there that much of a difference in the weight of one from the other? I’m having a 54inch electronics box made ,so I need it to hold the weight of all the gear that’s going up there. This is going in a charter boat so its going to be going out often.
What are the pros and cons on using one from the other.
Thanks for your help, Renegademike

Stainless is generally considered too brittle for a half tower, plus its heavy. Cracking will occur unless each joint is gusseted, and then no guarantees. I'd go with alum. and paint it with Awlgrip and use liberal amounts of CX and you should be fine.

UV

I have never seen a stainless tower on any boat here in Ft. Myers Beach. All towers are aluminum for the aforesaid reasons. Powder coating would hold up better than the paint. Awlgrip would be my choice paint for that if you had to paint it but try to get it powder coated if you can. Dave K

Follow Uncle Vics advice. I have seen a couple stainless towers up here in the noreast. There are heavy and get very ugly later on.

Mike,

How's it coming? Thanks mucho again for the ride to the Aero Puerto.

Think UV hit it on the head. Friend had a stainless half tower on his 28',
kept cracking @ the welds. Replaced it with alum.

Mike
In reading your post I think that you are thinking that the towers are anodized after they are built. Its my experience that you build the tower out of pre anodized pipe purchased from your local aluminum dealer.

Your welder will have to grind a very narrow strip of anodize off of the pipe in the weld area then coat the weld with a protective coating to keep the welds from corroding. I am not sure what they use but it looks to me like aluminum paint applied with an aritst brush just over the weld.

My favorite towers are the anodized towers.......

Harry Babb

I have a radar arch on another boat that was painted with Awlgrip 12 years ago. still looks OK, but will need to be redone soon.

I have a SS 1/2 tower now and have repaired it from time to time to get by, just did another $400 repair last week. I will soon replace w/Aluminum. Go w/ Aluminum.

Polished alum.?

No, Ernest, I think I'm going to paint it. The welder doen't want to fool with that shiney stuff. A couple of people on this board painted their's and all's still good.

Andre,

If your into black I had fabricated aluminum pipe top supports sprayed with truck bed liner and after 5 years it looks like the day they sprayed it. Great for hanging on and stays cool in the heat. They charged a small fortune but it works great.

I'm thinking about painting the next one, I haven't had very good luck painting aluminum. What's the process, primer and top coat that works the best?

Scot,

Sucessfully painting aluminum is, like any material to be painted, plated, or coated, dependant on proper prep techniques. Aluminum oxidizes almost instantly when air contacts the freshly abrated surface so the first step, after sanding or blasting, is to thouroughly acid wash the item.

The most common acid wash is AlumaPrep produced by US Paints, (Awlgrip). There are other brands, and most all are a dilute phosphoric acid. The acid wash chemically converts the surface molecules & stops the oxidation process.

Step two is to alodine the item. Alodine is an acid solution that also contains chemistry to leave a micro surface film that blocks the air from the surface of the aluminum.

Both solutions are applied to the surface, (one at a time, NOT combined together), & kept wet with the wash for at least 5 minutes, and then rinsed well with fresh water. After drying with a clean cloth, the surface is now ready to paint.

All metals should be primed with a proper primer compatible with the top coat paint system to be used. For aluminum, the usually accepted technique is to apply an anti-corrosive 2 part epoxy such as Awlgrip anti-corrosive 545 primer, (yellow in color due to the zinc chromate content), followed by Awlgrip Urethane Top Coat.

One good technique for the primer step, over aluminum, is to thin the epoxy primer with denatured alcohol almost to the consistency of water. Using a very fine tip spray gun, apply a thin coat of the thinned primer, allow the alcohol to flash off, & re-apply the next thin coat. Repeat this step through at least 3 coats and then apply an medium thick un-thinned coat of the primer.

After curing for 24 hours, a complete sanding with 240 grit open coat production sand paper will leave you with a satin smooth surface ready to accept the Awlgrip Top Coat. Be careful, don't sand through to the alumimun or you'll be back to square one...

My preference however, would be to have the item powder coated, but you'll have to find a powder coater that knows his business, is experienced with coating aluminum with it's oxidation problems, & can handle the physical size of the item being coated. If you did find a coater that meets these qualifications, it would still be wise to do your own acid wash & alodine. That way you know for sure the aluminum was properly pre-treated.

You'd also need to incorporate some hidden point of the item for the coater to hook his ground wire to so you don't end up with a spot that has a mar left after the clip is removed.

Br,

Patrick

(Note: I have edited the above post, removing the word isoproyl & replacing it with denatured. Also adding the word epoxy to primer. The addition of alcohol as a reducer works only with epoxy systems.

Most over the counter isopropyl alcohol is 91% & contains 9% water. Water is not something that you want in an epoxy system. Denatured Alcohol contains <0.1% water.)

Thanks Patrick, real details and products by name are extremely useful.