compatability of different marine grade alloys.

longranger · #1

I am interested in both the general compatability of marine alloys when welded and specificly interested in 5052 to 5086. The specific interest is because of a boat I looked at today. Very nicely designed 28' x 9'6" monohull with 5/16th" 5086 hull bottom and 3/16th" 5052 sides. Workmanship to my inexperienced eyes looked very good. This boat has a single 2003 KAD 300 with duoprop outdrive, only 400 hrs and 300 gallons fuel capacity. Came with some nice extras. Not all the items on a theoretical wish list but very reasonable price if all checks out. Will seatest ASAP and let you know what I think. Just need to hear that these two alloys do okay in the same hull.

Thanks,

Mike B

#2

Hopefully Jay (www.blacklabmarine.com) will be able to offer some input on this subject. My initial thoughts are that they are in the same "5000" class it should not be a problem.

I'm having some rails added to my boat now which are 6063 aluminum pipe as it bends a little easier with less fracture than the 5000 series pipe. They are welding these direct to the hull.

#3

The 5XXX series of alloys have magnesium (Mg) added in order to increase their strength and ability to work-harden. They are generally very corrosion resistant and have the highest strengths of any of the non-heat-treatable alloys. Increasing magnesium content in these alloys results in increasing strength levels. These alloys are commonly available in the form of sheet, plate and strip, and are the most common structural aluminum alloys. They are generally not available as extruded sections, because they are expensive to extrude. They are readily weldable, in most cases, with or without filler metal. However, there is an Al-Mg cracking peak at approximately 2.5% Mg, so care must be used in welding alloys such as 5052. It should not be welded autogenously (i.e., without adding filler metal). Weld filler metal with a high Mg content, such as 5356, should be used to reduce the crack sensitivity

Hope this helps. Yes they are compatable as long as the right welding process was used .

Bullshipper · #4

5052 is sure a lot cheaper than 5086.

#5

Bull , you nailed that one .

But 5086 is about 25% to 30% stronger.

Where one could use 5052 one could up the thickness from like .190 to .250 for the same money as the .190 5086 would cost .

longranger · #6

The lower cost of 5052 explains why the builder went with this alloy for less critical areas. If all checks out with the sea trial will need a good person for a survey. BlackLab Marine can you help with that?? Yikes hijacked my own thread :lol:

http://www.youtube.com/user/BLM26CC · #7

Hopefully he'll surf thru here.

Welder where did ya copy your info from... :lol:

It sounded really formal, useless you had a Tux on when you typed that :roll:

#8

Yea Welder, Very informative

I'm learning things left and right over here...

or would that be right and left for you Rightcoasters??? :lol:

#9

Capt. Dave ,
It's knowing where to find it :D

I'll help ya this time.
http://www.lincolnelectric.com/knowledg ... stakes.asp

#10

There are no problems with joinging these very similar alloys.

Our boats (BLM/Pacific) actually have 5052 for the console, hardtop, WA cabin all joined to the 5086 hull. Further the 5086 hull plates are joined by 6061 extrusions!

I would venture that almost all plate alloy builders do the same.

Both 5086 and 5083 (preferred hull alloys) don't like to be bent tightly. Those 90 degree bends in the console, etc would/could crack if done in such a small raduis in 5086/5083.

As mentioned - the much greater strength of 5086/5083 is best put to use in the hull - a 5052 hull is a biy of a sketchy thing...

Bullshipper · #11

[quote="welder"]Bull , you nailed that one .

But 5086 is about 25% to 30% stronger.

Where one could use 5052 one could up the thickness from like .190 to .250 for the same money as the .190 5086 would cost .[/quote]

I think it depends Lester. Lots of times, bends in materials to form angles strengthens materials and 5052 lends itself to that. I was also kind of surprised to see that 5052 is all they use in pontoon manufacture, and depending on diameters these are typically only .08-0.125" thick. So while 5086 may be stronger, it is also more brittle in that tradeoff too.

The Pacific uses a bowed curved panel for its side wall to do away with a lot of posts and stringers that would look unslightly and raise their cost, so here a more rigid panel to make the slow curve with 5086 is the way to go on larger spans.

But on a catamaran, the closely spaced inner frames on 30" centers and stringers on 10" centers porvide a lot more inner support. Curving 4 mm (.157") plate over these stringers already requres using porta powers, so bending a thicker and stiffer 3/16"- 1/4" (.188-.25") 5086 plate in large panels would be more of a pain to work with and put undo strain on the superstructure before it even hits the water, IMO.

Fyi surplus 5086 is running over $4 per lb and I have seen 5052 being offered for as low as $1 from the same vendor.

#12

IN2DEEP wrote:Yea Welder, Very informative

I'm learning things left and right over here...

or would that be right and left for you Rightcoasters??? :lol:

Dude , I'm in Texas , so I guess I'll just use both hands. :lol:

#13

Jay, Bull, great post guys.

Info , thats what were looking for. :D