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Old 03 November 2012, 14:16   #51
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so anybody here really good on aluminum? One of the problem with the Zodiac bracket is they spec 5086 aluminum. The 1/2" plate of that is $1100. Curious if anybody can give me a reasonable answer if I can substitute 5052 for that? I know it's "less" strong but is it strong enough? I can guess that the Zodiac design is the strongest thing in the world but can I live with a little less?
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Old 03 November 2012, 21:51   #52
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Why

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Originally Posted by Bigtalljv View Post
so anybody here really good on aluminum? One of the problem with the Zodiac bracket is they spec 5086 aluminum. The 1/2" plate of that is $1100. Curious if anybody can give me a reasonable answer if I can substitute 5052 for that? I know it's "less" strong but is it strong enough? I can guess that the Zodiac design is the strongest thing in the world but can I live with a little less?
You need to think long and hard when you try to save money on a build and determine if the money is for form, function or structure. I would say Structure should never be skimped. you can do with less but then you are working on borrowed time. What you save now will cost you 2-3x in the long run.
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Old 04 November 2012, 00:50   #53
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The point I was trying to make is just how overbuilt is the bracket? If it's reasonable to assume that the bracket needs to be strong enough to take force X and the bracket is built to withstand 20X then is 15X enough? I don't want to skimp but I also don't want to pay for extra capacity that will never come into play.

We can make hulls with 1/2" of glass instead of a 1/4" and it would be stronger but we don't. At some point the extra strength is just wasted money. I don't know how we can determine what that point is. that's what marine engineering people do (I assume) and I don't know any.

If my bracket fails and my engine falls in the deep it's going to cost a bit more than 3x :-) so I do realize what I am asking.
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Old 04 November 2012, 03:09   #54
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Originally Posted by Bigtalljv
Anybody got some spare 1/2" 5086 aluminum plate laying around?
1/2"??? What are you going to hang on it, a space shuttle booster?

1/4" plate will do fine, if you design it right; rigid box section with a couple of ribs should be enough for any single outboard out right now.Twins as well with a bit more bracing.

jky

Edit:I'll see if I can get some pics of mine tomorrow.
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Old 04 November 2012, 10:38   #55
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It's the zodiac bracket plans. I think it was 5/16" mounting plate, 3/8 sides and top, 1/2" engine mounting plate, and 1/4" side gusset plates. It's a monster hence my questions. I see most commercial ones are 1/4 all around with an extra 1/4 where the engine bolts go. What I don't know is what grade they use though.
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Old 05 November 2012, 11:56   #56
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5200 series (5052 to be specific) is "normal" marine stuff. 6061 is fairly commonly used; less corrosion resistance, but may be OK with a decent surface treatment.

Aluminium alloy - Wikipedia, the free encyclopedia
Guide to Buying Aluminum Online | Online Metals Guide to Selecting Metals for Your Project

Personally, I'd go for 5052; make sure you can weld the stuff (thickish aluminum apparently takes a pretty hefty welder to get adequate penetration.)

Sorry, forgot to take pics yesterday.

jky
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Old 06 November 2012, 15:40   #57
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yeah, I've been doing a lot of reading too. I have mostly come to realize that this question cannot or should not be asked. It' can't be answered appropriately.

5052 is the standard in the bracket industry and a lot of the marine industry. 5068 is "new" in the last 20-30 years and is a stronger version. 25% stronger, "better" corrosion resistance. It's the go to material for larger and higher end aluminum hulls. It's very rare and very expensive.

Jason
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Old 07 November 2012, 12:00   #58
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You need to think about cost vs performance. Just because there's a material that is "better" doesn't make the material that is adequate any less adequate.

Unobtanium has been in use on race motorcycles for years, and off the shelf street bikes still work just fine...

jky
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Old 07 November 2012, 12:12   #59
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Just because there's a material that is "better" doesn't make the material that is adequate any less adequate.
jky
You said it perfectly. I will be stealing your line.

Jason
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Old 09 November 2012, 11:10   #60
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You said it perfectly. I will be stealing your line.
There's a licensing fee...
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