Aluminum Trailer Questions

On Sun, 7 Aug 2016 10:20:50 -0700 (PDT), snipped-for-privacy@gmail.com wrote:


Hi James. You may have a different Ed in mind. I don't remember ever having been on a Yahoo group, but maybe a long time ago. I've heard that some of my stuff was re-posted there. So, maybe there is a connection.

The aluminum tube will deflect about 50% more than the steel one, but that "springiness" may not be the big issue. In any kind of structure with aluminum, the big questions are what kind of joints you're using in your design and what will be the strength of those joints.
If your alternative is stainless, realize that it's about 10% less stiff than carbon steel, and, as you know, it's harder to join.
--
Ed Huntress





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7075 is very strong, and pretty darn corrossion resistant as aluminum alloys go. 5052 and 5086 are more corrosion resistant, and are the most common marine grade alloys. 5086 is also quite strong.
Remember that most MC hitches are only rated for about 300lbs GROSS towing capacity, and you need to have just the right amount of weight on the hitch.

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wrote:

6061T6?
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I ran across a blog by a guy building a submarine out of 6061, but I never did follow up to see how he did. The thing that got my attention in thiws thread was "Sea" kayaks. I don't know how well 6061 holds up to saltwater. Otherwise 6061 is really nice to work with. Cuts well (compared to 5052) and is pretty easy to weld.
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wrote:

6061 has pretty good corrosion resistance, even when scratches. Generally not used below the waterline (immersed) in large boats, but used extensively in aircraft pontoons and a lot of aluminum pleasurecraft
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Well, I've only worked on a few small boats, but they all "felt" (cut/welded) more like 5052.
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wrote:

Which is also used.

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wrote:

Weren't those riveted?
http://test2.fiddlersgreen.net/aircraft/Grumman-Duck/IMAGES/Grumman-Duck-taking-off.jpg
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wrote:

I can tell from the reply that you didn't look at the link I posted. It was for an amphibian bi-plane, silly duck, er, goose.

Why not glue up some wood and carve 'em down in your spare time? Flap discs and grinding discs work well, but I'm pretty sure you have a couple of draw knives down there.
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On Wed, 10 Aug 2016 21:31:38 -0700, Larry Jaques

Yes the grumman was rivetted. So was my big Springbok - but it was also welded in numerous places due to some EXTREME abuse. (it was a former Algonquin Outfitters canoe that had seen many beaver dams, and rocky portages at the hands of less than proficient canoists.) Not sure which alloy it was - but it was HARD!!!! Welded like 6061.
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wrote: >>>Grumman canoes are made from 5052 aluminum

5xxx series of aluminum are work hardening. The more they are abused the better and stronger they get. Many years ago I repaired a canoe that was hit by a snowplow. The chunk I had to cut out acted like stainless steel !
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wrote:

I don't know about submarines but 6061 is fairly commonly used on masts and spars on sail boats.
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I'd begin by closely examining the usual aluminum trailers, then try to reverse engineer the design details.
http://www.wakefield-vette.com/resource-center/downloads/brochures/Standard%20Aluminum%20Shapes%20Wakefield%2001052011.pdf
--jsw
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On Thu, 4 Aug 2016 11:49:32 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Though aluminum is tempting I would lean toward mild steel instead. By weight the steel and aluminum are virtually the same stiffness. Of course aluminum will have better corrosion resistance but the steel can be painted easily. When in comes to joining though the steel has the advantage. Especially when you have towed your kayaks to some remote area, bent something on your trailer, and the only person close by that can weld it just has a 115 volt wire feed welder loaded with flux core wire. Eric
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http://www.boatdesign.net/forums/metal-boat-building/rivets-welds-aluminum-20541.html Jimbo1490: "Welding is often not a choice since not all alloys of Al are weldable. Even among the weldable alloys, the welds and immeditaely adjacent areas will be weaker than the unwelded parts if the stock was heat treated.
Aircraft are extensively riveted together. Until the latest generation of large aircraft, riveting was used exclusively to join aluminum panels together. This is still true of wings, which always serve as fuel tanks. Leaks are a very minimal problem even though kero is much slipperier than water. In aircraft, adhesive bonding is slowly replacing riveting. For the most part it is not being replaced by welding."
http://aviation.stackexchange.com/questions/16995/why-are-planes-using-rivets-not-welded-construction The Comet he mentioned was an early British aluminum airliner that broke apart in flight from unexpected metal fatigue.
https://en.wikipedia.org/wiki/Fatigue_limit
--jsw
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On Mon, 8 Aug 2016 18:37:29 -0400, "Jim Wilkins"

It is a bit more complex, at least for the Comet. In those days 2024, which is an unweldable copper-aluminum alloy was the most commonly used "aluminum" used for airplane construction (I think that may be true today).
2024-T4 has an ultimate tensile strength of 68,000 psi and 6061-T6 an ultimate tensile strength of 45,000 psi.
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wrote:

All of the aluminum on my plane is 6061T6 - rivetted. All flight surfaces and flight structures.
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What's the difference? --jsw
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On Tue, 9 Aug 2016 06:37:42 -0400, "Jim Wilkins"

The stuff on the plane is .016 to .030" thick. The trailer is minimum 3/16 inch - mostly 1/4 inch wall.
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On Tue, 09 Aug 2016 16:11:45 -0400, snipped-for-privacy@snyder.on.ca wrote:

It's very difficult to weld any aluminum alloy above the 5000 series without creating a crack-sensitive joint. And 5000 series and below are not very strong. Besides that, 5052, which is used a lot in boats, has a "cracking peak" at 2.5% magnesium, so you need to use filler that will supply plenty of extra magnesium to be sure your weld doesn't hit the cracking peak after welding.
6061 is very crack sensitive if you use insufficient filler metal. Welds in 6061 are tricky because welding exceeds the artificial ageing temperature; your heat-affected zone will be a mess of varying hardness and ductility, and it will change over time.
It is almost impossible to produce a weld in aluminum that is as strong as the base metal. In contrast, mild-steel welds generally are close in strength and ductility to the base metal.
Thus, they don't weld aluminum on aircraft. They aren't welding the new aluminum car chassis, either.
--
Ed Huntress

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