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Old 05-10-2020, 07:22 PM
brunolund brunolund is offline
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Default taking dent out of 080 aluminum boat hull

got a few smaller dents in the side of me lund. will a regular body hammer and dolly work on 080” aluminum? or too light?
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Old 05-10-2020, 11:48 PM
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Kerry Pinkerton Kerry Pinkerton is offline
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Regular hammer and dolly work is effective with 80 the DEPENDING on the alloy. Some alloys are hateful to work. The aircraft guys know more than I about working other than 3000 and 1100 series.

If the manufacturer is still.in business, see if you can find out the alloy.
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Old 05-11-2020, 11:33 AM
brunolund brunolund is offline
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it is 52xx. i can’t remember the last two numbers, but i’ll find out.
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Old 05-11-2020, 01:00 PM
crystallographic crystallographic is offline
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Default Straightening .080" Marine-grade aluminum alloy 5052

Quote:
Originally Posted by brunolund View Post
it is 52xx. i can’t remember the last two numbers, but i’ll find out.

Hi Rob,
Maybe I can help ....
I've been doing 5052 since 1978.
5052 is the most common aluminum alloy for marine usage down here in the USA - from Coast Guard cutters to fish boats. (Canoes are 6153 and 6061.)

Using a straightedge across the hollow part of the dent measures the deflection. "Small" = 2in. Medium = 4in and then it goes up, up, up.

(For those readers out there used to 1100 alloy, 5052 is 3X the strength. For 3003, 5052 is 2X the strength.)
.080" is an "adult thickness" - as on the old 300gal firefighting droptanks I have straightened .... 10lb hammer w/ screw/scissor jacks.

Tools needed:
6lb flat-faced steel "brick" with some 3/4in ply bonded to it. (use good adhesive that will take some repeated impact and the ply surface will NOT stretch the aluminum when all three parts contact with the sharp "whaang!") "Brick" should span the dent, fully supporting hammer blows from the back side.
3lb hammer
Sticky gloves.

Method:
You can go some ways with the aluminum hard and cold. But you will see a limit - like when you are swinging so hard you cannot stay on target? -When aluminum alloys are too hard to work they can be softened, and this process is called annealing.

Annealing 5052
The process varies with different aluminum alloys. This process described below is for alloy 5052.

(Note: 5052 is known as "marine-grade aluminum" and is designated as such by the Aluminum Association. It is also used in aircraft and auto construction, and sees wide usage for electronic chassis and also for kitchen surfaces.
When you see any bare/unpainted aluminum boats spending years in seawater they will be a dark gray color, and not the familiar shiny silver.)

Annealing Procedure for alloy 5052:

You will need to heat the alloy 5052 to 650F - ACCURATELY. This alloy is very heat-sensitive and can be permanently damaged by temps of 900F and above, so do not overheat. Use an accurate heat measuring device - TempilStik "heat crayon" which melts at 650-675F, or a temp gun - BUT these IR "infra-red" guns do not like reading reflective surfaces with good accuracy.

(I have personally used a machinist spray called "Dykem" on thin delicate sections, with good success, repeatedly, accurately --- a light blue-purple mist-coat will show applied 650temps as going to a distinct goldish-greeney-gray.)

Quenchant- Spray with water/slosh over with sloppy-wet rag to quench. And then let the hammering commence.

Technique to straighten: 2 person job.
"Anvil person" supports the hollow side with wood-faced heavy steel brick, Firmly leaning on it.
"Hammer operator" clambers aboard and positions himself to accurately smack one blow at a time, on each dent.
Communication is same as two aviation guys riveting wings and fuselages ...: "Ready with anvil"...."ready with hammer" ... "okay - GO!"

*** Good idea to black-mark the dents numerically, on both sides.
**** Alloy 5052 does NOT like to be worked hot, as it goes "hot-short" and fractures into little pieces, like glass.


Good luck!
-end-

(ps. I've been a Boeing-approved metal consultant/educator for over 10 years.
I've also attended a number of Aluminum Association national conferences and while there had a lot of in-depth conversations with most/all their guys who write their top-notch technical manuals.)
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Last edited by crystallographic; 05-11-2020 at 01:06 PM.
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Old 05-11-2020, 08:35 PM
Chris_Hamilton Chris_Hamilton is online now
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Thank you Kent for taking the time to post this good info.
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Old 05-12-2020, 05:59 AM
RockHillWill RockHillWill is offline
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You can't expect a better tutorial than that. Thanks Kent!
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Old 05-12-2020, 08:38 AM
brunolund brunolund is offline
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thank you very much!!

these dents are less than 1/2” probably closer to 1/8”, but i tried the regular body hammer and dolly, and hit it pretty hard. the dents didn’t move at all. guess i’ll try the bigger stuff, i have a smalll section of rail i could glue some plywood too, but definitely going to take two people. it’s heavy!! i was worried about stretching the metal by using a bigger hammer, but i’ll give it a shot.
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Old 05-13-2020, 11:54 AM
crystallographic crystallographic is offline
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Quote:
Originally Posted by brunolund View Post
thank you very much!!

these dents are less than 1/2” probably closer to 1/8”, but i tried the regular body hammer and dolly, and hit it pretty hard. the dents didn’t move at all. guess i’ll try the bigger stuff, i have a smalll section of rail i could glue some plywood too, but definitely going to take two people. it’s heavy!! i was worried about stretching the metal by using a bigger hammer, but i’ll give it a shot.

Chris, Will and Rob, you are all very welcome.

(I had been intending to write this 5052 process out some time ago and then "pressing" obligations superseded..... And then .... this effort evolved into a mini "core dump." )
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Old 05-13-2020, 01:38 PM
norson norson is offline
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Quote:
Originally Posted by crystallographic View Post
Chris, Will and Rob, you are all very welcome.

(I had been intending to write this 5052 process out some time ago and then "pressing" obligations superseded..... And then .... this effort evolved into a mini "core dump." )
I'd like to have a book of your "core dumps". Always a wealth of information.
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