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Old 06-02-2010, 17:36   #1
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Making Aluminum Oar Round Again?

Over the christmas holidays we were hit with 40 kt sustained winds while on a bow-and-stern mooring and with the inflatable tied at the stern. In some gusts the inflatable became airborne which looked pretty funny but I didn't think too much of it and it was too late to try to get it back aboard.

After the wind event I found out that the dinghy had apparently gotten under the stern line a few times and the result is that there are a few dents in the aluminum tube oars. I doubt the dents weaken the oars appreciably but the out of round is bad enough to make it almost impossible to slide the round oarlocks up and down as needed to balance the oars while rowing (yes, we row the dinghy everywhere :-)

My question is if there is some tool like a pipe cutter without the cutting wheel that can be used to get the aluminum tube back into a true round ?

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Old 06-02-2010, 17:48   #2
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They do make a tool for expanding exhaust tail pipes maybe you could take it to an exhaust shop and see if they could help. Another thought would be filling that section with water and freezing. But given your location that might be tricky lol.

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Old 06-02-2010, 17:51   #3
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With the propper swaging dies it can be done. Probably not going to find them, so, being aluminum, if you can find something resembling a half round bottom die (perhaps a groove in the dock between two boards) to support the underside and hammer the tall of the oval with a wooden mallet or the likes, you should be able to forge it back into shape. Aluminum will work harden and become more brittle so don't over do it. But freehanding it and rolling as required should get you at least a facetted round that will slide through the oarlocks.
Cheers to you for rowing! And an inflateable at that!
Good luck!
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Old 06-02-2010, 18:00   #4
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Recently repaired some construction staging with this problem. Took the end cap off and used a close fitting, rounded end, wooden dowel to expand out the tube from the inside.
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Old 06-02-2010, 18:08   #5
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IF you have a table saw...

you could run a 2x4 across the blade at an angle (up about 3/8" above the table) and make a nice rounded grove. Pinching the tube between 2 of these might do well.
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Old 06-02-2010, 18:58   #6
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Excellent suggestions !

Thanks for all of them.

Ingenious solutions ... now I just have to decide which to try first



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Old 08-02-2010, 10:44   #7
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I have not done it my self but I am told that to fix a collapsed pipe you can block one end, fill it with sand, gently heat the area to be repaired and apply pressure to the sand with a ram-rod, essentially pushing out the dent from the inside. This sand technique also works to put a smooth bend in a pipe or tube that would otherwise kink when you tried to bend it.
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Old 08-02-2010, 11:14   #8
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All above good suggestions. We only row our dingy as well...
have kept a set of back up oars on board over the years...just
in case, just a thought.
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Old 08-02-2010, 13:29   #9
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Heating aluminum would probably not be a good idea. Steel yes, but the point at which aluminum becomes maliable from heat is very close to the point at which it will become a pudle on the floor. Also the aloys get their strength from controlled cooling, esentially tempering, the reason that the 'effected weld zone' in welded aluminum is 80% of the strength of the parent material. Filling with sand before pounding to shape will 'back it up' from the inside and help keep it round, but I'd just go for it freehand, carefully. Get'rdone...
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Old 08-02-2010, 13:45   #10
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indentations can be taken out of a tube from the outside with a block having the outside diameter of the tube being the bore of the inside of the block.. the block cut in half and clamped around the tube.. greese the tube and the block and as you increse the preasure on the block with a clamp, rotate the block around the tube..
At one time, I was was a partner in an upper-end bicycle shop (Corsa-Cycles) and every now and then we'd repair a bicycle frame where someone dropped it against something or it was involved in an accident durring a race and put a dent in the frame.. we would take the dent out with a wodden block..
As I said, when clamping the block around the tube, roll the block around the tube as you put preasure on tightining the block..
The idea is that if the dent pushes in in one part, it pushes out on another.. if you slowly roll the outer area in, you're also rolling the interpart out..
You might even go to a bike shop.. they might have the blocks in the back to fit the diameter of the tube you have..
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