Belly pan; Aluminum VS Galvanized Steel

[BB 55 Bubble]

It is my understanding that there is no "risk" of dissimilar metal corrosion with the use of galvanized steel up on aluminum. Am I wrong? I just purchased a galvanized reproduction roof vent from vintage trailer supply and he was sure that I would have no problems with corrosion. I want to replace my belly pan, after 51 years of use and abuse the thing is just shot. So I did some research, It would appear that 5052 at the thickness of 0.025 is the cheapest and best alternate to the original 2024 T3 at the same thickness. The price for a 4X10 sheet varies between $80-$120, the killer is the shipping since no one around me carries the stuff in stock. Here is my thought; What about painted galvanized steel sheets that is used for making roofing panels. There are several local shops that sell the sheets 4X10 at 0.025 thickness for $36. OH YEA what a difference that is in price. Another plus is when I secure the pan to the frame no issue with using any multitude of fasteners directly to the frame. Since I was going to apply a bed liner to the pan exposed surface to add strength and keep it looking good no one would know the difference. In my trailer there is a sheet of what looks like galvanized steel that attaches to the skin directly and there has been no corrosion, and it would appear that the wheel wells are also galvanized steel. Could that be correct?
So help me out what could go wrong? What should I do to prevent the possibility of the dissimilar corrosion from occurring? Is using a flexible calking like Vulcum going to be enough to separate the to metals or should I use some sort of buffer material? I could really use some input on this before I dive right on in.
Thanks BB 55 Bubble

[malconium]

Except possibly for the issue of the extra weight this sounds like a plan that could work. I would suggest that you get some high quality electrical tape and put a strip of it around where the belly pan would attach to the aluminum.

Malcolm

[A-Merry-Can]

just use mill finish aluminum. i can't remember the exact number... but 2024 is expensive stuff. i only used it on the sides and top. my belly's the cheap aluminum, in .025 thickness... no worries about corrosion, either! i think i paid about $35 a sheet for it? 8X10...


...WEAR GLOVES, btw! i got pretty sliced up by it. it's much worse than .040, because of the thickness... or should i say LACK of...

jp

[BB 55 Bubble]

I think that the 5052 is mill finish, I was told that cannot be polished and is what I was quoted for at the price of $80-$100 for the 4X10 sheet. The price of aluminum has gone up so much it is ridiculous to pay that much for something I or any one else will ever see. So if the galvanized will work why not? I'm all for paying for the 2024 T3 on the exposed skin, but there has to be an alternative. I’ve seen posts here pondering the possibility of an alternative product for the belly pan but no mention of galvanized steel. The only point of contact should be minimal and even then might not be an issue.

Here is another thought, what about no belly pan at all. Seal the heck out of it with sealant and use some sort of rigid corrugated plastic over the that foil insulation I keep reading about and plan to use. I think that is what manufactures use on trailers today? I would paint the hell out of the frame and protect it from the elements. I would get great accesses to the bottom if a problem occurs. Even with the belly pan I would never be able to keep all of the dust and critters out of the belly area because of the gap that is created around the area the frame exits the pan to form up the bumper. Its an idea but I love the look of that sealed belly its part of the trailer character.
What do you all think?

[dwightdi]

Original Shell aluminum on the really old trailers was 2024 Alclad. It was a sandwich laminate with 2024 high strength on the inside and pure aluminum on the outside. The 2024 really does not have good corrosion resistance but the outer skins are excellant and take an excellant polish. Really big bucks for this stuff which was originally used for airplanes. Belly skins were just soft alloy aluminum. Not too bad for corrosion. Galvanize is zinc coated steel. The zinc is higher on the galvanic scale than aluminum and will actually sacrifice itself to protect the aluminum in wet enviroments. Since it will be electrically connected to the steel frame it should also protect that as well. If left unpainted it will deplete itself in a number of years and then the steel sheets will start to rust. If you prime it with a galvanize primer and then paint it with a good gloss enamel it should last for years and not be as easily dented by rocks. It will weigh three times as much as comparable aluminum.

[BB 55 Bubble]

I wanted to place a post on this thread so that it would be placed up in the front. I could really use some more information on this idea and get some more opinions. So far it looks like if I take the time to protect the aluminum from the galvanized steel there should be no problem. Let me know what you all think!

[BB 55 Bubble]

I did some serious thinking about this possibility, and made a bunch of calls to some local welders and fabrication shops. I think that there will be more problems than it would be worth. Yea I will have saved a few dollars but if I am going to make the trailer better than new, better stick with the aluminum. My biggest revelation was when I was thinking about attaching the belly pan to the rest of the trailer aluminum. I can protect the major surfaces with all sorts of protective barriers but when I use the buck rivets there will be direct contact between the aluminum rivet and the exposed steel in side the drilled hole of the galvanized steel sheet. So unless there is such a thing as stainless steel rivets that has a shear strength of a standard buck rivet, this idea is DEAD! I would still like to find an alternative but it might be that I will have to stick to the aluminum. Why mess with a good thing.

On a side note I do still think that there is still merit in the idea of using a roll on truck bed liner on the exposed surfaces of the belly pan. Adds strength and durability to a thin sheet of metal. Less chances of a rock or over zealous do-it-self guy like me from making a hole in the skin. Another plus is I will have fewer problems with the chemicals that the road district in Oregon uses to de-ice the roads.
Thanks to all of you for your input on my half cocked idea.

[A-Merry-Can]

hey man, i just bought a 4X8 sheet of aluminum at a shop here in atlanta for $30. i can't remember the grade right off hand, but it was really cheap. i got .032 this time, to make the trunk bottom for my trade wind. i used .024 for the belly on my 18 footer, since it's a lot easier to bend. shipping might kill ya, though. you never know. i just bought 6 sheets of wood veneer, and the shipping cost was only $20.

PM me if you want the contact info for this place.

jp

[BB 55 Bubble]

I did find stainless steel rivets. That makes me a fiber, I think boy don’t I feel dumb. I was reading a post and found a different online source for rivets by chance. Has any one used them before, will they work? I found them here http://www.mcmaster.com/ page #3148. So... hum back to a maybe?

[CaddyGrn]

Bubble,

There is a interesting metal "salvage" yard in Medford where we picked up some nice aluminum (left over from some huge type job, who knows where...) and it was brand new material... I don't think it cost us more than $200 to do the whole belly pan and had leftovers. If you are interested in ever going to this place or want more info. I suggest you PM my hubby NorCal Bambi... he knows more details.

Good luck. I vote for aluminum! You will add extra weight re-doing your trailer as it is. You want to keep that in mind unless you beef up your frame and axle.

Mrs. NorCal Bambi (traveling in S Tardis)

[A-Merry-Can]

Originally Posted by BB 55 Bubble

I did find stainless steel rivets. That makes me a fiber, I think boy don’t I feel dumb. I was reading a post and found a different online source for rivets by chance. Has any one used them before, will they work? I found them here http://www.mcmaster.com/ page #3148. So... hum back to a maybe?

oh, i'm a frequent McMaster-er! just got a shipment friday, in fact... locks for the access hatches, new grommets, wide belly rivets, stainless fasteners, and some aluminum channel. great guys. they have EVERYTHING in their catalog!

[Frank S]

Hi--Anybody ever use fiberglass sheets for an A/S belly pan?--Frank S

[uwe]

Originally Posted by BB 55 Bubble

The price for a 4X10 sheet varies between $80-$120, the killer is the shipping since no one around me carries the stuff in stock.

The aluminum can be rolled up into very handy small cylinders for shipping.
It would not be cost prohibitive to ship a few sheets.
I just can't see galvanized roofing sheets under something as cool as a 55 bubble.

[raebaker06]

I used aluminum sheeting I got free from my roofing contractor. he uses it for vallys on the roof.
I did how ever use larger pop rivets and put a rubber washer under the rivet to prevent the rivet from cutting through the aluminum, which did happen on some repairs I had done in the past. with the rubber washer 5 years and no cutting through.