Any Real Case Against Alum Frame?

[WizardOfOdds]

Anyone know of a valid reason not to build your foam (or other trailer) on this frame lighter weight alternative to the HF frames?
http://www.tnttt.com/viewtopic.php?f=35&t=66101

[GPW]

No reason at all not to ... as long as you don’t exceed load and stress limits ... And it’s in the budget ... The ultimate ideas is ... The weight you save , is the extras you get to carry along ...

[Shadow Catcher]

Well actually there is a reason, and there are advantages as well. The disadvantage is aluminum has a finite modulus of elasticity, it cracks and brakes if that is exceeded.
Ours is all aluminum and the advantages are it is lighter weight ad it will not rust. The first tear we owned by this company had a catastrophic failure of the tongue with the folks who got it from us. This is a design flaw wheels too far back and not a heavy enough aluminum, too much flex and it fractured. I have had ours reinforced.
One concern is also dissimilar metals, we have nothing grounded to the frame, copper lugs attached with steel screws, quick corrosion problem. Fortunately all fixtures lights etc. have ground wires and I ditched grounding to the frame altogether. bolts and screws are no stainless steel and I used PTFE paste to minimize corrosion. Having said all that I would go for it.

[WizardOfOdds]

Thanks for the comments (in both Chassis & Foamie blogs), all very useful.

I was expecting a lot of "nay-say" on the aluminum due to corrosion at joints with steel parts. Here is a page from a trailer manufacturer ?(Great Dane Trailers) with tips to minimize the problem.

http://trailer-bodybuilders.com/fabrication/how-deal-dissimilar-metals

Wikipedia has a good page on Galvanic corrosion too

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0ahUKEwi52N3nvdzMAhWEPz4KHfuvBb8QFgg5MAQ&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FGalvanic_corrosion&usg=AFQjCNG2PU0Jpb-1kHTX5AplrylhkZGQvw

Looks like a challenge but then again, all-steel trailers have rust issues. I have some vinyl flashing I hope is ok for surface isolation. It would be nice to get some nylon shoulder washers for the hole through the Al to isolate it from the bolt threads. I am not familiar with PTFE paste, is it some Teflon product?

I had heard about aluminum problems with regard to fatigue and cracks (hard to forget what happened to the first commercial jet airliner, the British Comet)! I just didn't think it was a problem with trailers until Shadow Catcher's comments (Foamie Blog). I'm hopeful it will not be a problem if I stay light.

Still undecided which way to choose, it’s hard to give up on saving a hundred pounds! I am not sure if a bolt-together aluminum trailer is a wise thing or not. While most (if not all) aluminum trailers deal with different metal for the axle & suspension, the ones I've seen are welded witch avoids a lot of joints I will have to deal with in these designs.

[Shadow Catcher]

There are 80 year old Douglas DC3's still flying so with the right design... The tongue at the point where it went under the trailer was what failed on Mega Mini #1 and I was always concerned about the amount of bounce/flex. I have had Mega Mini #7 reinforced and may find some 4140 steel to insert to further reinforce further.

[KCStudly]

PTFE (Polytetrafluoroethylene) is the generic chemical name for the Dupont registered brand trade name Teflon. It's like saying facial tissue instead of Kleenex.