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Old 07-05-2012, 12:20   #1
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Radar Arch - Aluminum vs SST?

I am looking at putting on a radar arch on our sailboat. The arch will encompass a post for the radar, a post for a wind generator and dinghy davits.

The estimates for SST are outrageous!!! 10K +

Itís been suggested on using aluminum ...... any thoughts?
its half the price.

Is aluminum a viable product to use the this application?
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Old 07-05-2012, 14:17   #2
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Re: Radar Arch - Aluminum vs SST?

If properly designed, sure, Aluminium is fine. Some friends built one and had it powder coated and it looked pretty flash. They then took off on a circumnavigation so I don't know how the powder coat held up... many disparage the stuff on boats.

Actually, I am rather surprised at the difference in costs that you quote. Were the scantlings of the alloy arch actually suitable for the material, or was it a simple substitution, size for size?

Obviously, just an opinion...

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Old 07-05-2012, 14:35   #3
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Re: Radar Arch - Aluminum vs SST?

Marine grade aluminium would be fine. It will be lighter, which is helpfull for weight so high, but the costs should not be half the price which suggests the aluminium may not be marine grade or the sections do not have equivalent strength.
The quote for SS is high, so the aluminium may be good quality.
Leaving it raw is fine, as is painting, but I would not powder coat aluminium in a marine environment.

What grade aluminium is quoted ? What thickness and design?
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Old 07-05-2012, 14:41   #4
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Re: Radar Arch - Aluminum vs SST?

Dont know the grade of the aluminum... the quote was a round off from the guy who was looking at doing it.

I just wasn't sure if :

1. Would it be strong enough to hold up a dink?
2. What kinda rust factor would there be in marine?
3. And has any one EVER done a radar arch in aluminum?
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Old 07-05-2012, 14:44   #5
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Re: Radar Arch - Aluminum vs SST?

I built just what you described, went with food grade dairy stainless. It's not polished, but it only cost $1000 including wire and argon/mix. "Chrome won't get ya home" isn't that the biker saying. It all depends if you really want/need to look like the rest of the white hull, blue cover, polished yacht crew. I'm a weirdo though and think a nice clean gray tug is way sexier that the masses of carbon copy white sloops the seem to prevail. It's like one guy set the rule "this is how a proper boat looks" and most people spend whatever it takes to remain in this yachtie confromist box. Hey if you go different, the other 99 guys at the dock will talk and snicker. Not a shot at you, just stating your options are limited. Unless your a radical.
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Old 07-05-2012, 14:49   #6
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Re: Radar Arch - Aluminum vs SST?

A guy a couple of boats away from us has an aluminium arch. It's white, so coated but I don't know what with, though he was touching it up a couple of weeks ago with something out of a can.

I don't think he has a dink attached but he certainly has solar panels.
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Old 07-05-2012, 14:51   #7
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Re: Radar Arch - Aluminum vs SST?

Quote:
Originally Posted by riversandbar View Post
Dont know the grade of the aluminum... the quote was a round off from the guy who was looking at doing it.

I just wasn't sure if :

1. Would it be strong enough to hold up a dink?
2. What kinda rust factor would there be in marine?
3. And has any one EVER done a radar arch in aluminum?
1. Yes
2. Aluminium will not rust, but you do have to careful with dissimilar metals like SS, but this is no different to most masts. In fact masts are usually constructed from a more corrosion prone aluminium.
3. Yes virtually all aluminium boats have davits/ radar arch constructed from aluminim. Have a look at the Ovni production boats that include one as standard.
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Old 07-05-2012, 14:53   #8
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Re: Radar Arch - Aluminum vs SST?

The ali frame on my rib cost about £1000 to have made after another boat ran into the back of her and trashed it. Since I wasn't paying the bill it didn't bother me. What was very interesting was the whole thing was so light, easily picked up by one person, so probably 10 kgs. One reason for the cost was having to match the existing design and therefore the bolt holes on the boat, the other, they used a special ali which was resistant to corrosion in a salt water environment. After a couple of years the surface was dull but no more.

That is a 6 man liferaft being supported on the A frame, and it also made quite a good seat in calmer waters, so able to take my weight. The frame I think was about 2" tube.



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Old 07-05-2012, 14:53   #9
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Re: Radar Arch - Aluminum vs SST?

$10k??

You may want to ask around for a better bid. I had an SS arch built and installed for a fraction of that. But one yard quoted me twice as much as another for the exact same job.
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Old 07-05-2012, 14:55   #10
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Re: Radar Arch - Aluminum vs SST?

Quote:
1. Would it be strong enough to hold up a dink?
Impossible to answer unless you tell us the grade of aluminum and scantlings.
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Old 07-05-2012, 17:06   #11
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Re: Radar Arch - Aluminum vs SST?

I had my local welder custom design one that is a Radar arch, dingy lift and worked into the rear pulpit. All for about six grand in 316 Stainless. Looks very sharp. I think I would look around....
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Old 08-05-2012, 05:21   #12
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Re: Radar Arch - Aluminum vs SST?

Thanks for the info guys! I will definitely look around and see if I can get it done cheaper. I would prefer it be SST and dont really want to compromise.

Can anyone recommend someone in the Houston, Texas area?
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Old 08-05-2012, 07:44   #13
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Re: Radar Arch - Aluminum vs SST?

Last year I had a major canopey built on my cat out of SS & yes its nice but its also work to keep looking nice- Aluminum on the other hand looks good and is no work at all- Do you want to polish SS or go sailing- Wish I went Aluminum now!
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Old 08-05-2012, 09:55   #14
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Re: Radar Arch - Aluminum vs SST?

Funny Ram I have had my arch for over a year now without one spot of rust or discolorment. I wonder if it was made differently. My joints are all welded then ground down smooth so it looks like all one piece of metal. I will look closer once back on board- but I haven't seen anything, and only minor discolorations from my pushpit and pulpit that are also SS and over 35 years old.
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Old 08-05-2012, 10:29   #15
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Re: Radar Arch - Aluminum vs SST?

Quote:
Originally Posted by s/v Beth View Post
Funny Ram I have had my arch for over a year now without one spot of rust or discolorment. I wonder if it was made differently. My joints are all welded then ground down smooth so it looks like all one piece of metal. I will look closer once back on board- but I haven't seen anything, and only minor discolorations from my pushpit and pulpit that are also SS and over 35 years old.
There are defiantly different grades of stainless- when I picked up the boat at the factory in 06 not a stain or discolor the first 3-4 years then slowly they turn spot & stain if not polished at least one a year- this could be due to the Med with its higher salt content- My new g-4 anchor chain rusted out in 4 years!-The new stainless was made in Turkey and is not as good as what came from the factory, but there was no way of telling until now- The good thing is its 10 hours once a year for me, I m going to have to live with it__
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