Aluminium sheet exterior?

[dolphin73campervan]

Hello all. While my Dolphin campervan is post-1970 by a few years, its construction is very much pre-1970 (and distinctly English with its 'inverted boat hull' roof).

The walls are solid plywood which were originally covered with CP10 profile cladding. However, I wish to clad the body in solid (probably 1mm) aluminium sheeting, along the lines of the older aluminium-over-bondwood vans. The fact that the body has solid ply walls means the use of a profiled cladding is unnecessary, and I want to get away from an easily-dented surface.

The question is this - what modern adhesive will enable an aluminium skin to be successfully bonded to a solid plywood substrate? The aluminium would expand and contract substantially more than the plywood with temperature changes, so it would need to be flexible as well as strong.

How do restorers of early aluminium-over-bondwood vans bond their aluminium skins to the substrate?

Advice and suggestions will be much appreciated!

[Roehm3108]

Hi Dolphin

I think you will find that people who covered their ply with aluminium merely screwed it on wherever they could track the framing, which made the contraction problem a non-event. For example, check out the cladding on this van

vintagecaravans.proboards.com/index.cgi?board=forsale2&action=display&thread=10078

What you're planning is uncharted territory and you may find that the best idea is to remove the ply completely, insulate the cavity and add the 1mm ally. With a flat ally like you are talking about, I would worry about any moisture getting between the ally and old wall may eventually rot the bondwood, unless you really seal it completely.

Some of the ally stoneguards you often see on vintage vans have been known to have rotten ply underneath because of what I mentioned.

[dolphin73campervan]

Thanks Roehm,

Yes, I think the problems in the past from aluminium over bondwood (ply) all stem from the issue of moisture getting in between the two materials. This would happen either at the edges, or where there is a screw or a nail which provides a path for water.

Even if old-fashioned caulking was used at the edges, the daily expansion and contraction of the aluminium with temp changes would eventually break the seal down.

I thought that condensation may be an issue, but the only areas where my Dolphin plywood (and some framework) were adversely affected by moisture after 40 years was either on leading edges (where the profile of the cladding prevented a perfect seal - one reason I want to go to flat cladding) or areas where trim was screwed on, with water entering along the screws once the caulking had lost its effectiveness.

I'm hoping that something like a Sikaflex product will both seal the panels perfectly and bond the aluminium to the plywood, virtually for ever, and still have enough flex to allow for differing expansion rates.

Uncharted territory indeed (it seems), but there must be an answer which could possibly suit many future restorers as well.

The plywood on the Dolphin is actually a structural part, with the 20mm deep 'framework' essentially there to allow the interior lining to be attached. The body is incredibly well insulated, with full 20mm custom-fitted polystyrene right through the walls (filling every space not taken up with framing), while the curved roof sections are fully insulated with fibreglass.

Dolphin in Dandenong were certainly not cheapskate builders! I continue to be impressed with the quality of the workmanship, and would love to know who 'Ray' was who signed the plywood exterior before the aluminium profiled cladding went on 40 years ago!

Neil

PS, for those who haven't seen the Dolphin, it can be seen at www.grouseguitars.com.au/dolph/

[cobber]

G'day Neil,

What you have in mind to do has been done in the days of vintage caravans, back in 1955 there was a product called "Alply" that was used on gypsy caravans as far as we know it didn't last beyond 1959, so maybe the problems you mentioned were too hard to overcome .....the aluminum was apparently "hot bonded" to the ply.
But who knows, maybe there is a modern glue that could do the job.

Sounds like a big job to me.

Cobber.

[dolphin73campervan]

OK, lots of research, telephone calls, visits to Bunnings (where I managed to tear the test sample by twisting) etc later, I have finally decided on a plan of action.

I have also in the interim completely restored the Bedford CF cabin, with a full strip and inside/outside respray, new full wiring loom with all additions (gauges, ancillary lights, sensor wipers, automatic battery isolators etc etc etc) wired in.

The Dolphin will definitely wear a polished aluminium outer skin over its plywood body. Today I just completed the curliest bit, the very intricate cabin/camper body interface, and it's coming up a treat. By the end of November the rest of the job should be finished, photographed, and out on the road doing some long-overdue travelling.

I eventually decided that I wouldn't rely totally on modern materials (read Sika), but a combination of tried-and-true and the new. The 1mm panels will be essentially screwed onto the plywood body with stainless button-head square-drive screws with nylon washers. The centre of each panel will be drilled to accept the screws exactly (no movement), but all other holes will be over-drilled by 2mm (the screws have a 10mm head) to allow for expansion and contraction of the aluminium skin, which will be around 1.1mm at the extremity of each 2.4 metre sheet over a range of 80 degrees C. The nylon washers I am using will allow slippage when necessary, where if I had relied on a modern Sikaflex bond I would have had to have the aluminium a few mm proud of the plywood substrate which introduces all sorts of problems (and costs). Sikaflex 252 (and some 221) will be used at strategic points to ensure water never gets in, but overall the final solution is relatively low-tech.

I'm quite sure the whole thing will work well, both visually and from an engineering point of view, and will try to take photos (generally just with my mobile phone, as it's in my pocket as I work) as I go. I generally add any interesting new photos to www.grouseguitars.com.au/dolph, so feel free to view and comment as you desire!

By the way, can anyone tell me of any negative health effects of aluminium? With all the cutting, dry-sanding, wet-sanding, and hand-polishing I've been doing to date (a lot more to go) I can't believe how much aluminium sticks to me...and that's just externally.

Cheers!

[seeshell]

Hi Dolphin73Campervan

I've been following this with interest, since we're about to re-lid our van. Would something that skins but stays soft and pliable like butyl tape be easier to apply, particularly in vertical situations?

Let us know how you go - I'm hoping you're slightly ahead of me, so I can gather some further tips!

Cheers
Seeshell

[dolphin73campervan]

Thanks for the comments to date. I will reply in detail when I get sufficient facts and details to do so.

To update progress, the new skin is now on! I was starting to wonder if I'd ever get to this stage, and there have been many sleepless nights researching technical aspects and fine-tuning more artistic aspects, but I am relieved that the 1mm aluminium skin is now actually attached. The very scary curved roof panels were attached with the help of a very skilful pair of additional hands attached to my son, David. He's the hairier one, and I'm the fatter/older one in the photos in the below link.

There will be many days of polishing with 1200, 1500 and 2000 grit wet-and-dry then buffing compound (painfully long, boring, messy process), and a week or so of fitting all trims, windows, doors and many hundreds of stainless-steel marine-grade screws with nylon washers, but I can see the end.

After the initial polish comes the rest. I have come to a decision about how to trim the edges of the panels and roof, using materials and techniques which I have never yet seen used in this way, so I will stay silent on those until I've finished! Suffice to say, the big, ugly Truline/Millard edging I had long ago ordered to faithfully replace the original edge between the white, profiled walls and the white 0.6mm roofing panels will not be used. I have many metres of it for sale!

All attaching screws will be proudly visible (no dubious workmanship to hide underneath the plastic filler trim!), and I am confident my blend of traditional bonding methods (nails and screws) with the addition of modern - and expensive - bonding and sealing methods (Sikaflex 252 and 221) will give me my desired result of a great-looking, great-performing (reliable) outer skin. On my campervan, I mean. I've never achieved one for myself!

Check the bottom photos in this link to keep up with the progress (slow as it is!) of this project.

Comments (negative as well as positive) are welcome.

Cheers!

[DC3Td]

Hi Dolphin.Great job you`re doing. But 1200,1500,2000 wet & dry then buffing compound? Make it easier on yourself - Purple (brand name) from auto outlets followed by a sealant.
If you can track down the Willyn/Airstream story in Down History Lane.Pages 22,24,25 & 27 should give you a treat for your eyes. gordon

[dolphin73campervan]

Thanks Gordon. I couldn't find the story you referred to, but will look again later.

However, there ain't no shortcuts in polishing! Even though I have been super careful in selecting, handling, cutting and fixing the 1mm sheets, and the 'mill' finish looks superb in its own way, simply polishing the surface as-is (even with Purple) will simply polish the surface. The mill finish is actually surprisingly free from being a flat surface, and requires a lot of sanding to bring back to a uniform, flat surface ready for polishing.

The bullbar on the front of the vehicle is a great example. It looked great. No real scratches, just 'dull'. You wouldn't believe how many days of dry sanding with a random air sander, then wet-and-dry, then final polishing it took to get it looking right.

For the body I won't have the same finish in mind, and the initial surface is a much better starting point, so hopefully the time taken won't be any more ridiculous than what I'm planning.

The upside with such polishing is that it actually is pretty easy to maintain once the finish is achieved. Many years of classic motorcycle ownership, with uncoated aluminium castings and wheel rims to be kept pristine, have given me a respect for aluminium and its maintenance!

Cheers,

Neil

[firefighter]

Nov 12, 2012 21:57:37 GMT 10 DC3Td said:

Hi Dolphin.Great job you`re doing. But 1200,1500,2000 wet & dry then buffing compound? Make it easier on yourself - Purple (brand name) from auto outlets followed by a sealant.
If you can track down the Willyn/Airstream story in Down History Lane.Pages 22,24,25 & 27 should give you a treat for your eyes. gordon

G'day D73C

Gordon gave your the wrong section .........Willyns Airstream
is in Members photo album

First thread page 22
vintagecaravans.proboards.com/index.cgi?board=photo&action=display&thread=3688&page=1

Your might be better off over on our sister forum

ditzygypsy.proboards.com/

As we only go up to dec 1969....as your camper is 1973

cheers
f/f ;D ;D ;D

[dolphin73campervan]

Thanks for that firefighter - I found the Airstream straight away when pointed to the right area! They are stunning things...

And yes, I post all other things to do with my Dolphin camper in the classic caravans board. Just, as the introduction to the topic says, "While my Dolphin campervan is post-1970 by a few years, its construction is very much pre-1970 (and distinctly English with its 'inverted boat hull' roof)." Also, the exterior use of plain aluminium sheeting over a plywood base is almost exclusively pre-1970, so I figured that I'd get most help (and be of most help to others) on this board for this topic.

Cheers!

[DC3Td]

Thanks for the correction F/F.


Hello Neil. No shortcut re polishing but figured an easier method might reduce the muscle spasms! Still a big job either way & better you than me.Its certainly a very different/better look now than when she was cladded.Hope you`re going to hand out sunnies when you`re through polishing her. gordon

[dolphin73campervan]

On the road again.

Many thanks for all the helpful comments and suggestions along the way. We'll see you on the road!







You can see some photos of the re-cladding here, and photos of the completed vehicle here

[barkpaint]

Sure looks like Pyramid Hill in the background. Maybe you were in Bendigo, Kangaroo Flat area last week?
Went shopping in Aldi? Hahahahaha, missed you by that much....you just took off as I came to say hello, unmistakable vehicle, you have there. cheers, Heather

[dolphin73campervan]

Hello Heather,

Yes, yes and yes! The run to Bendigo last Thursday was its first 'test' run. Sorry I missed you!

Cheers,

Neil

[dusty]

Fantastic job - very inspiring!