Aluminum roof coil siding/skinning

[kpatchen]

Has anyone skinned a bus using .040 x 102" x 35' aluminum roof coil siding and what were the results?  The metal is available locally and one could do the whole side of a bus in one piece.

[bevans6]

My initial thought is that .040 is quite thin, and roofing aluminium is maybe very soft.  If it has to be structural I would probably look at .080 or therabouts.  I would probably use 6061-T6 if I didn't have to put bends in it.  If this is just covering window holes, then it would probably be fine, but watch out for the softness factor.

Brian

[Nick Badame Refrig/ACC]

Hi kpatchen,

Welcome to posting!

I second Brians claim that .040 is too thin! I think it would be a wrinkely mess even if you used 8' sheets..

.080 is a good choice but at 35' long, you will have a major challange on your hands trying to not only hang

it but hang it without ripples. We usually preheat the material before securing it to the surface then when

it cools, it will be tight and straight..

Good Luck
Nick-

[robertglines1]

Welcome.I agree with others to thin. will wrinkle and that ocassional  limb scrape we all do will leave a crease..I use 18 guage cold roll sheet alot. not that much differance in weight and I feel more comfortable myself working with it..covering window etc...What kind of bus you working on???   Bob

[Ericbsc]

Been there done that. Not strong enough, and if you foam it watch out. It will look like a turd in the punch bowel!! I used .055 and got a redo out of it. The coil is probably 3036 or softer and expands big timewith tep. cycling!!! Find 6061 if possible.

[kpatchen]

Thanks for all the replys.  I am currently raising the roof on an 1984 Eagle model 10.  The roof is raised 8" and welded up.  I am fitting the rear cap currently and the siding looks like it come next due to shingling effect I see.  I was thinking about doing this coil stuff as I could side it in one go, instead of 4 x 10 or 4 x 8 pieces.  I think I have changed my mind and will go with the pieces as it will be more easily managed.  Now...... if I go steel, as someone suggested, should I get galvanized, galvaneal (easily painted).  The cold rolled suggested by Bob, is just plain steel right?  I note from the searches most people use 18 guage.  Apparently that works well.  Something I would get from Ryerson (I think I can get this in town).  If I go aluminum sheets, I see the 6061 type and I assume, from reading the searches in this forum, I should go at least .080 for the long running sides.  Again thanks.. I will continue to sort this out.

[robertglines1]

18 GA cold roll was selected by me for paint adhesion proprieties.just ruff surface with 250 grit disc and prime with good auto primer  Clean Oil off first.  resist scratching and denting better than mild steel..can be formed to minor radius..more heat tolerant than alum . paint both sides.. I have both on present coach Alum and steel and the alum does flex more in sun..Galvanize presents paint adhesion problems.  other properties come into effect like mixing two differant metals but simple thin neophrene stripp can fix that..stainless to steel would be no problem..I don't know what your Eagle used above the stainless sides...Bob

[bevans6]

Frankly, if it is non-structural think about fiberglass.  No corrosion, stable in sunlight, takes paint extremely well, light, and can be bonded on with no fasteners.  It can be had in 35' lengths.

Brian

[rusty]

Think very hard about fibreglass. I have an Eagle that has fiberglass on it. I glued it to plywood that was added between the side tubing. It looks fine untill the glue gives way. If you can get a good glue that will not let lose it works well. When the sun hits it it bulges out. I will not be using fibreglass on the next bus.

Good Luck Wayne

[Jeremy]

Whilst some adhesives (Sikaflex for example) could be used to glue fibreglass, you would only need them if you were attaching the fibreglass to metal or glass for example. Wood should of course be the perfect thing to fasten fibreglass to, as by using fibreglass itself as the glue you can in theory create a perfect bond.

I'd never really heard mention of fibreglass expanding in the heat, so I've just googled it for my own interest - apparently a 100' length of fibreglass pipe will expand by 1" (ie. about 0.08%) with a 100' increase in temperature.

Jeremy

[mcidave]

I used one peice fiberglass to skin with, I think it looks great.  I had to support the middle of each window frame with a lateral angle iron support [welded] in which the fiberglass sheet was riveted to.  I bought a 40 foot peice on a apllet and cut it into two 20's.  Not cheap though [on palet trucked in]!!!  I think I got it from R&M.

[rusty]

Jeremy, I usd sikaflex. I must have not done it right or did not use the right stuff. If it stuck right it would make a nice side, but I will not take the chance again.

Wayne

[bevans6]

I did a little googling and the thermal expansion coefficient of fiberglass constructs is apparently one third that of aluminium.  Doesn't mean you don't have to glue it on right, mind you.  Gluing fiberglass is actually very tricky.  There are two ways to bond fiberglass pieces together, chemically and mechanically.  The only time you get to do a great chemical bond is with new layups, it's very difficult to get a chemical bond between a piece of fiberglass and something else (even other fiberglass).  So you need to do a mechanical bond.

When a piece of fiberglass comes out of the mold, the "good" side is covered with wax of some sort as a mold release.  It usually also has a gel coat of some sort, and is shiny.  If you want to bond something to the good side of fiberglass, you need to chemically remove the wax, then grind away the gel coat, then prepare the fiberglass surface by cleaning and grinding with 80 grit or coarser paper.  Then you can glue or bond  to the fiberglass and get a mechanical bond.

If you want to glue or bond to the "rough" side of fiberglass, you actually have to follow the same steps except for grinding off the gel coat.  That's because the resins used to create the fiberglass usually leave a trace coat of wax as part of their curing process, and that will kill the bond.  Also, even though the fiberglass surface looks and feels rough, microscopically it is very smooth.  You need to clean the surface to remove the wax and then grind to 80 grit to prepare the surface, then you can bond to it.  

You also need to prepare the surface that you are bonding the fiberglass to.  It needs the same 80 grit surface and cleaning.  In the case of aluminium, you need to remove the surface oxide by grinding minutes before you bond, since aluminium oxide forms very quickly in atmosphere.  You can do this with a new stainless steel wire brush or wheel that has never been used on any other surface but aluminium.  Finally, if you are bonding to fiberglass the best system to use for all types of fiberglass is an epoxy based resin.  It has far more mechanical strength than polyester.  

I spent far too much time learning about fiberglass at one point...  pic below is my 1972 NTM Mk4 sports racer, 100% fiberglass monocoque tub car, 1,000 lbs with a 200hp BMW engine...  Hoo Rah  

Brian

[luvrbus]

On a Eagle I would not use anything but steel, aluminum and fiberglass expand about the same rate and makes for a wavy side, Like Rusty said he has a good looking coach till the sunlight and heat come into play check the Eagles on www.eaglesinternationl.net the ones that used any product other than steel have not been happy with the results.If you choose to go with the R&M glass pm me I give you a number for a guy that has 2 rolls cheap



good luck

[Marcus]

I used a 35 ft piece of fiberglass on an mc9 . Used pl urethane glue with some rivets under moldings . It's been on for 7 years with no issues and no waves or bubbles. paints extremely nice. Would do it again.