Which mettle is going to be best

H

hardee

New member
Which mettle is the best choice for use on the C-Dory, in primarily salt water use?
a. Aluminum with a powder coating finish
b. Aluminum with an anodized finish
c. Stainless with a brushed finish

The goal is to have a surface that will stand some salt spray, and tolerate a freshwater wash down after each trip and be sturdy. Most of all, not need replacement in 6-7 years.

I am still working on replacing my ScanStrut radar tower that is aluminum with a powder coating finish that has failed after 6 seasons. I have not found a production product similar that will meet what I need, ( 12” rise with a forward lean ), and am looking at having one built, so I can pick what it will be made out of. I do want it out of mettle.

Harvey
SleepyC:moon

January_2010_344.thumb.jpg
 
what failed on your stand? if it's the finish you may be able to just have it powdercoated again.
I've been looking at radar arches and pondering what material, the polished stainless sure looks nice but is so expensive. If you only got six years out of the powdercoated pedestal, maybe the stainless isn't such a bad price
 
I'm surprised that an aluminum radar mount corroded out that fast. For example, Our Journey had a powder coated aluminum mast, which was drenched regularly and it's still going strong after 20 years. It seems to me that a radar support on a C-Dory would be more protected than a sailboat mast.

Where I did have trouble was putting 2 dissimilar metals together: Aluminum and stainless will corrode each other, right through any powder coat. Found this out the hard way. So please say where the support is corroded. If it's where the stainless bolts touched the arch, you can avoid that with plastic washers.

As mentioned above, a stainless radar arch is bulletproof. The one the factory mounted is still good. You might contact the OEM fabricators to see how much one for your boat would cost.

Also, ScanStrut offers a stainless tower and a composite one. The composite plastic one looks neat, will not corrode and is about the same price as an aluminum one. The stainless tower isn't much more expensive.

Boris
 
The "mettle" of stainless steel metal is going to be the best for your radar support. There are some very high quality anodizing which will last for many years--but it is very rare to find these preparations on most consumer grade applications. (Long Beach Ca. Marina has anodized aluminum railings which are about 50 years old, and still look fairly good--but that is the exception)

There seems to be a lot of difference in the durability of powder coated aluminum. It may be the alloy, the technique or materials used. If I wanted to redo the old strut, I would completely remove the coating, then properly acid etch the bare metal, apply two part epoxy chromate coating and final good two part LP paint. I have had that last over 10 years on masts. Bori's comments on dis-similar metals is very important, especially if not properly separated.

Of course the $10 "commode" mount will not corrode at all….
 
If it's metal your speaking of, get out the dollars and do stainless steel. I got a partial credit on my failed aluminum powder coated radar pedestal and went with polished stainless steel. Game over. Pictures in our album
D.D.
 
Another suggestion is use Deft 02-Y-40A zinc chromate epoxy primer (Mil Spec and used on the fighter aircraft landing gear and very tough) then use Awlgrip 545 and color it to match gelcoat

m2cw
 
:oops: I kind of messed up that "mettle" thing didn't I.

Sorry. :oops: :oops:

To clarify. I'm not sure if it is corrosion, but it is for sure powder coat adhesion failure. It is on the base, and appears to have started at on of the bolt holes. The Scan Strut tower is aluminum, and is bolted down with stainless bolts. The failure looks more like failure of the PC to stay attached or bonded to the aluminum, and may be due to the stainless bolt, or that bolt penetrating the coating in the drilled hole, or possibly the wrench making a gouge in the coating when used to tighten the bolt. The powder coating has flaked off of most of the base by now.

Boris, I have looked at the Scan Strut options, and actually have a Stainless tower from them that has a beautiful mirror finish, but it is not tall enough and the rake is aft, not forward, which I prefer, and then it is also too short for what I need. I like the idea of the composite, but really wanted the stainless.

I would love to find a 12" stainless with a forward rake and that beautiful finish, but have been unable to. At the Portland boat show, I talked to a fellow from a Tacoma company that does Aluminum tubing, (biminis, and fly bridge etc) out of aluminum, large bore, (2" up to maybe 3"), anodized with a bright finish. it looked really nice, but I was concerned if it would be sturdy enough.
They assured me it would be a lifetime finish.

I looked through the album for Will-C and the corrosion that it looks like your tower had is more like a true corrosion. Mine looks like the PC is just flaking off. The metal is still intact.

Ken, From what I have been able to find, it was probably a lack of good preparation for the PC, (Although ScanStrut denies that, unless I send it back to them to analyze --ah that would be back to UK :twisted: I will pass on that. I liked the white tower, but I do not want to go through taking this one off, getting it re-done and then having to do it over again in 5 or six years.

As to the spelling, It came from looking at the name on a beautiful, Armstrong cat, based in Port Townsend, except I swapped the "L" and "E". And yes I know the difference, but was not concentrating on what I was doing at the moment, and my spell check didn't catch it. Oh well, thanks all for reading my mind, and for the great comments. I would be open to thought on good custom fab shops, probably stainless, and yes, potter-water, I like the shiny stuff too.

Thataway, I agree, the WC stand would be corrosion free, but i have a thing about wanting the forward rake, and could not figure out how to make that work with those parts. The current ScanStrut will probably go thorough that process after I get it off, and then be sold to a Brat down the line.

Harvey
SleepyC:moon

12_28_2011_Pix_from_Pentax_731.sized.jpg
 
Regarding Harvey's problem with the PC radar tower:

When bolting down powder coated metal structures with bolts, would it be advisable to use nylon washers to avoid having the powder coating crushed between two metal surfaces (which are a much harder material) and would seem to initiate fractures in the powder coating, and then lead to further delamination ?

Seems logical to me, anyway. What do the manufacturers recommend?

Joe. :teeth :thup
 
Maybe I am missing something--but the strut you have now is satisfactory, except for the powder coating. If so, remove all of the powered coating. Sand it by hand until completely bright, use progressive dinner grit sand paper down to about 600. Then wash with soap and water. Blow dry with non oily compressed air. Then brush on Alumiprep33, coat with Alodine 1201, Let dry, coat with epoxy Zinc or Strontium Chromate primer, and then apply your top coat color paint of choice. If properly done, and then installed, this paint job should last longer than the powder coat did. (and if it gets a bit dull, just touch up with new paint.
 
S/S, polished. No other choice IMO. But it will cost. Also, DO NOT USE TANNER MFG! I cannot stress this enough. I had a lousy customer service experience from them and will not use the EVER again. Ask around who does good work besides them.
 
Have you considered having one fabricated for your boat. By doing so, you can achieve the height, and angle you are seeking. Cost might be a bit more, but at least you get what you want.

Im having an awning made locally (Seattle) and going custom was the only way to get the proper look I was after.

If you want a referral, I got someone.
 
hardee, that stainless tower would have a forward rake if you turned it around 180 deg. I believe that the mounting surfaces are parallel and the member that joins them is a truncated cylinder so the geometery is correct.

Just a thought, your choice

Boris
 
journey on":1qot3tgs said:
hardee, that stainless tower would have a forward rake if you turned it around 180 deg. I believe that the mounting surfaces are parallel and the member that joins them is a truncated cylinder so the geometery is correct.

Just a thought, your choice

Boris
Click to expand...

Boris, You are right. and I tried that. The ScanStrut tower is reversible and the top and bottom plate are parallel. Two things. 1. the top plate is predrilled and shaped for the RayMarine dome mounting plate, and the upright "tube" is predrilled for the cable, and that hole is about 1" diameter and on the aft wall (aft being the direction of the tubing with the raydome sitting on the plate in their predrilled position.

I even asked about getting that hole filled or covered and a new one in the back. My other issue with it is that it is too short, or I would have been more persistent in mounting this one reversed.

Thanks for the hints though. The more I think about this the more I think it is not going to be a tubular upright, but a cross or plus sign cross section, and it will be shiny.

Even the current one I have is about 2-3 inches to short so replacing it is seeming more likely.

Harvey
SleepyC :moon

January_2010_344.sized.jpg
 
If the choice is aluminum and custom built, make sure to specify one of the true marine grade alloys such as 5083 or 5086, leave it bare, and isolate the fasteners with nylon or rubber washers/sleeves. Since the cost of custom will be mostly labor, stainless is not a bad choice, again using a marine alloy of either low carbon content or stabilized to prevent weld decay. If you're paying for a custom fabrication it would be wise to specify the exact alloy you want. I love it that you're considering hiring a craftsman to do a custom job, when the overwhelming temptation these days (including for me) is to buy an offshore product on the internet. All the best, Mike.
 
Mike said:
"...specify one of the true marine grade alloys such as 5083 or 5086, leave it bare, and isolate the fasteners with nylon or rubber washers/sleeves."
Click to expand...

Thanks Mike, ??? When you say ..."leave it bare" are you saying to not even have it anodized? I know the aluminum can be highly polished, which would look closest to the SS rails I have now, but wont the salt spot and corrode them unless there is some surface finish like anodize, powder coat or paint?

Thanks for the kudos on the "craftsman". Hope I can find a real one.

Harvey
SleepyC :moon
 
The light pitting you see on bare marine grade aluminum isn't a concern except for cosmetic. These alloys form a protective oxide coating when exposed to the air. Anodizing or occasional waxing will improve cosmetics if that's a concern. The real concern would be selection of a non-marine grade of aluminum with reliance on a surface coating to impart corrosion resistance. Eventually something will get under the coating and corrosion will begin. Anodising, powder coating, etc., will also not stop galvanic corrosion, so your stainless fasteners need to be insulated from the mast itself. Bedding via use of a rubber mounting gasket between the fiberglass hard top should be sufficient to keep saltwater out of that crevice. If a composite unit were available which met your design specs that would probably be the best way to go, but of course you're limited to what's available off-the-shelf. The devil is in the details, but to me that's what makes tinkering with boats so enjoyable. Best, Mike.
 
Mike,

Thanks for the reply. Composite would be perfect IF I could find the right product. Short of that, I'm kind of like a crow, and like the shiny stuff, if I can find it. (Besides, the right SS should last until they make pocket radar or something.)

Harvey
SleepyC :moon
 
If you are using the "commode" style radar mast, couldn't you just put a + piece of aluminum inside the tube? Get a couple pieces as wide and as long as the inside of the PVC tube, notch them together, and drop inside. Since the aluminum will be inside the tube it doesn't have to be structural, welded, painted, or anything else to make it look nice.

Depending on how big your PVC mast is, the insert might not increase your radar reflection enough to bother doing this. But it will work as well as an + mast of the same size would.
 
Back
Top