Coachbuilt body renovation

[Petros90]

Hello. At last, some sensible people with sensible advice and information after hours of attempted research ...

We are halfway through our third year of Coachbuilt Motorhome Ownership, and had to decided to sell it and buy an older smaller panel van conversion, probably a Ducato Mk I. And buy some toys with the change!

The van is a 1999 Swift Sundance 520 on a Ducato Mk II

I had noticed a small amount of corrosion in the rear panel and had thought my car body repair skills could tackle it. Oh dear.

Imagine our shock and horror etc when discovering that our lovely van, bought at a dealer for 12K, was now worth about 2-3K max, due to Water Ingress.

A few weeks have passed, during which I have been thinking and researching composite boards and van construction. I've gone through denial, anger, and I'm now in the acceptance phase.

I've read, digested and understood one relevant thread here, that of Paul's roof replacement on his similar van. At least he knew he'd be in for some work when he bought it!

We paid for a damp check a few days ago, the readings are all around 12-16, except for one area at the rear behind the ladder mounting which is 40-50. The corrosion is at it worst under this area. It could be coming from there, or the awning rail above, or the window seal, or the top (aftermarket) light, or the wire from said light going into the awning rail. Or somewhere else.

We were advised by the Van Damp Man that water had penetrated one of these areas, and soaked down the frame. He was able to supply a quotation for remedying this which would be by removing furniture and working from the inside removing all the affected wood, replacing the rear outer aluminium panel and removing the awning rails and resealing . This would cost 7.5K. (!)

I understand that the holes (pinpricks when we bought it) are the result of galvanic corrosion due to the dissimilar metals - steel and alu - reacting in the presence of a weak acid ie the damp/wet wood, causing the aluminium to oxidise and break down the bond.

A few days ago I decided on a course of action based on my research (but before checking out this forum). I thought to open up the corrosion holes, and screw on some hooded louvre vents in an attempt to dry the rear panel out. We'd use it for holidays and weekends and after a few months or maybe a year it would have dried out and I could attempt to remove and replace just the rear panel 'outer skin', spray it to match, and all would be nice and lovely again and we could sell it for a decent figure ...

I had assumed there was some kind of frame - I'd read of 'frames' and 'aluminium skin' and 'insulation wadding' so had assumed that there was some kind of frame on which the panels were attached.

I thought I could do this and eventually make up a new rear panel onto the frame after everything had dried out. How wrong I was, on all counts.

I multitooled a hole (about 2" square) right through the rear panel. (This will be hidden on the inside as it is below the wardrobe floor.) And, more shockhorror.

It appears that there is no frame, as such. The whole of the van, it seems, is a closed box section constructed, IKEA-like, from composite board. Composite board is actually extremely strong and light when intact. This board appears to be a sandwich of two 3-ply/3mm sheets with a core of polystyrene, the outer faced with aluminium forming the waterproof skin, and a decorative vinyl wallpaper on the inside. All these are 'bonded' together - however this bond does not withstand the assault of water, the ubiquitous solvent.

So, no frame, ALL the strength comes from the bonded composite board, which is slowly deteriorating. And how much area is affected, and which panels, is unknown.

The first stage seeems to me to be to try to seal the seams. I have bought some 'Captain Tolleys Creeping Crack Cure' (which seems to do the same thing as Comma Seek 'n' Seal now unavailable) and I'm going over the seems as directed. Also there are wires connecting the aftermarket lights which disappear into the seams and I'm sealing these -in fact any protrusion, protuberance or perforation to do with the bodywork.

If this is successful - and as I can't see what's going on underneath I just have to assume it will be - what then? I have to also assume that, due to capillary attraction, the ply sheets (inner and outer) are wet throughout the rear panel, as they're sealed by vinyl on one sheet and aluminium on the other. I was going to cut out aluminium holes on the outside and cover with louvres which can be painted to match the body. This would be stage two, and the panel wouldbe allowed to dry out over time.

But the ply is sealed by its composite sandwich partners, so I think the louvres aren't going to do much to dry it out. I could build a (removable) box on the back, put a dehumidifier in that, have it running constantly when we're not using it ...

On the inside it is more do-able - I could expose the face on the inside by stripping out wallpaper and install a dehumidifier, or just have the door & windows open, it is very warm and windy currently.

We want to be able to use this van, while it is drying out. I've 'test-fitted' a 9"x 9" panel vent using mastic/polythene sheet as a gasket and zinc-plated self-tappers - I want the panel to be removable so I can check on progress. I intended to do the same for the row of holes along the bottom using 3" deep panel vents. It didn't go too well, it's not allowing water in - yet - but it doesn't sit well on the ribbed alu despite extra fixing holes and the alu vent is still bendy. Closely spaced pop rivets could work but I need removability.

I'd be very interested in - and grateful for! - any comments or suggestions on all or any of the following courses of action and indeed anything in the preceding blurb.

Am I correct in my assesment of the van construction ie very large composite panels, with no or minimal framing?

If I remove the rear (under window) panel, I'm weakening the structure. Is it safe as long as I a) don't move the van and b) replace it with a timber frame-mounted alu sheet?

Is it possible to dry out both ply constituents of a composite panel without disassembly? eg by drilling holesfrom one panel to (but not through) the other, so that moisture has access to free air.

And just to clear up one point. When people talk about 'frames' in this context, what exactly are they talking about? The panels butt up directly to each other at the corner - the corrosion is very close there so I can see it. There must be some kind of reinforcement here, probably short lengths of under-1" timber so the screws that hold the thing together have some 'bite'. Ply doesn't take a screw too well. Is this the 'frame'?

How is it possible to know when the inner wooden component of a panel is dry?

Is there a way of safely installing removable louvres to the ribbed aluminium outer face?

Is that a waste of time as the contained moisture will not migrate to such a small exposed surface area of ply?

The interior readings are below average, but it's impossible to check the outer ply layer without invasion of the alu skin, yes? So is this why the repairers strip out from the inside

Stage Three would be the hoiking-out of the offending panel without unpicking the side awning-seams, and replacing with a strong timber frame with wadding and /or polystyrene insulation and outer panel bonded/supported/glued onto a ply sheet. Which would have to be fixed on by screwing from outside. Is this a feasible solution?

Do you agree that the secondhand van market is overpriced and we are underinformed?

Anybody got a decent older panel van conversion they wanna swap?

Should I not bother with any of this, advertise on eBay and take the hit?

If you have got this far, thank you for staying with me. I welcome your comments and advice.

[747]

I know virtually nothing about coachbuilt motorhome repair but thinking laterally, do you HAVE to repair like for like. What about the option of a plastic or fibre glass panel?

 

I have kept the details of a company in my favourites in case of body damage to my van. It will do no harm to have a word with them. I do know that Caravans and Motorhomes can be a mix of both types of construction. It will not be cheap but might be cheaper than the first option.

 

http://www.autoxtra.org/replacement.htm

[Brian Kirby]

It would help if you could attach a few pictures so that one can see what you are describing. It is difficult to comment on the construction of panels in particular vans, as although the principle is much the same across the board, the manufacturers don't do everything in exactly the same way. The frame in a composite panel is likely to run around the perimeter of the panel, and to include some larger elements at points where stresses are likely. It will usually include some additional framing around doors, hatches and windows, and possibly where furniture is attached to the inside (or possibly short lengths of timber, possibly ply sheets). Elsewhere the panel will be likely to be just the inner wallboard, the insulation, and the outer aly skin. Damaged external skins are usually repaired by re-skinning the panel over the original skin. The problem with water ingress is that the framing elements tend to rot quite fast, because the environment within a damp panel is just what the rot spores like. So, if the wallboard is already deteriorating it is likely the frames in the vicinity will have begun rotting. To expose the extent of the rot, it is easier to remove the wallboard, which can then be replaced in sections, than to start peeling off the aluminium. So, that is the approach that is frequently adopted, depending on the result of the initial, non-invasive, inspection. Attaching vents to the aluminium without properly remedying the leaks would, IMO, be likely to make matters worse. There is a lot of spray the travels up the backs of venicles on wet roads, that I would suspect would get through the grille. It think you'll have to strip out the furniture in the damp area, and carefully cut away the wallboard to see what is behind it, and decide from there what to do for the best.

[Petros90]

Thanks Brian. At the rear of the van is the shower on one side, wardrobe on the other, and the gas fire on an extended panel in-between. So a lot of work involved to remove all this, which I had been hoping not to do!

 

And I was hoping to use the van while it dried out, and also keep my options open on selling.

 

What you are saying is that the purpose of removing the wallpaper would be to assess how much water has penetrated the inner skin, and that is a good point which I'm only just assimilating.

 

I could start by peeling off the paper inside the wardrobe where it won't show and a match will be less of a problem.

 

re: your points on framing - yes, the word is misleading, I had the concept of a big van-sized frame - like a timber-framed house - whereas in this context it actually means 'panel-framing'! A completely different thing.

 

I had thought I'd come to terms with this, but the more I find out and the more I think it through, the more of a nightmare it seems. And if I want to work on a vehicle I'd much rather be restoring my MG!

 

[Guest Peter James]

Welcome to the forum Petros.

Don't be angry about it.

The dealer I visited has over 250 motorhomes but little below £30k and nothing below £20k because problems like damp in a coachbuilt is such a risk in the lower price range. I understand they have to make £4-5K mark up just to cover their costs.

£4k a year depreciation after buying from a dealer is not too bad, so whilst this is disappointing, its not a rip off.

I'm having trouble picturing it, so as Brian says, photographs would be helpful, although I appreciate there may be little of the damage visible to photograph at this stage.

[mike 202]

Sorry to hear of your plight. Have sent you a PM, (as you are new it means personal message

Mike

[Petros90]

Peter James - 2015-07-01 10:10 AMWelcome to the forum Petros. Don't be angry about it.The dealer I visited has over 250 motorhomes but little below £30k and nothing below £20k because problems like damp in a coachbuilt is such a risk in the lower price range. I understand they have to make £4-5K mark up just to cover their costs. £4k a year depreciation after buying from a dealer is not too bad, so whilst this is disappointing, its not a rip off. I'm having trouble picturing it, so as Brian says, photographs would be helpful, although I appreciate there may be little of the damage visible to photograph at this stage.

Thanks. I'm resigned now - and hey, we can use it as a spare bedroom ...

I'm having problems posting pics, have contacted admin. I'm taking pics as I go.

The process so far seems to be 1) seal everything 2) install sacrificial anodes 3) dry out the affected area.

 - sealing seams is the first priority plus taking anything that screws on, off, and sealing. It's  a long job and hot in the sun! I'm working on a way to try and dry the back panel out while using the van, think I may have a solution which I'll run past the members - it might be of use for people with similar problems although each one is going to be different. .

The idea is to be able to use it while it dries out. I'm not up for a big restoration project.

[Petros90]

Brian Kirby - 2015-06-30 6:37 PMIt would help if you could attach a few pictures so that one can see what you are describing. It is difficult to comment on the construction of panels in particular vans, as although the principle is much the same across the board, the manufacturers don't do everything in exactly the same way. The frame in a composite panel is likely to run around the perimeter of the panel, and to include some larger elements at points where stresses are likely. It will usually include some additional framing around doors, hatches and windows, and possibly where furniture is attached to the inside (or possibly short lengths of timber, possibly ply sheets). Elsewhere the panel will be likely to be just the inner wallboard, the insulation, and the outer aly skin. Damaged external skins are usually repaired by re-skinning the panel over the original skin. The problem with water ingress is that the framing elements tend to rot quite fast, because the environment within a damp panel is just what the rot spores like. So, if the wallboard is already deteriorating it is likely the frames in the vicinity will have begun rotting. To expose the extent of the rot, it is easier to remove the wallboard, which can then be replaced in sections, than to start peeling off the aluminium. So, that is the approach that is frequently adopted, depending on the result of the initial, non-invasive, inspection. Attaching vents to the aluminium without properly remedying the leaks would, IMO, be likely to make matters worse. There is a lot of spray the travels up the backs of venicles on wet roads, that I would suspect would get through the grille. It think you'll have to strip out the furniture in the damp area, and carefully cut away the wallboard to see what is behind it, and decide from there what to do for the best.

[Petros90]

Brian Kirby - 2015-06-30 6:37 PMIt would help if you could attach a few pictures so that one can see what you are describing. It is difficult to comment on the construction of panels in particular vans, as although the principle is much the same across the board, the manufacturers don't do everything in exactly the same way. The frame in a composite panel is likely to run around the perimeter of the panel, and to include some larger elements at points where stresses are likely. It will usually include some additional framing around doors, hatches and windows, and possibly where furniture is attached to the inside (or possibly short lengths of timber, possibly ply sheets). Elsewhere the panel will be likely to be just the inner wallboard, the insulation, and the outer aly skin. Damaged external skins are usually repaired by re-skinning the panel over the original skin. The problem with water ingress is that the framing elements tend to rot quite fast, because the environment within a damp panel is just what the rot spores like. So, if the wallboard is already deteriorating it is likely the frames in the vicinity will have begun rotting. To expose the extent of the rot, it is easier to remove the wallboard, which can then be replaced in sections, than to start peeling off the aluminium. So, that is the approach that is frequently adopted, depending on the result of the initial, non-invasive, inspection. Attaching vents to the aluminium without properly remedying the leaks would, IMO, be likely to make matters worse. There is a lot of spray the travels up the backs of venicles on wet roads, that I would suspect would get through the grille. It think you'll have to strip out the furniture in the damp area, and carefully cut away the wallboard to see what is behind it, and decide from there what to do for the best.

[Petros90]

Pics at last, the posting process almost as labour-intensive as the topic. I guess that the only way to include text is to write it beforehand or as a caption to the pics.

There's some holing in the side 'skirts' but I'm not hugely worried about them.

The side panels are currently unaffected.

I removed the leftmost screw from the rear upper awning rail, it's bright metal, I'm thinking that this is good news. Here's the van (I hope).

Basically the holes are confined to the middle panel, top left side and lower left three-quarters above the seam/lightboard join. Top one has now dried out and I've fitted a louvre over it.

Still raining here so no sealing today.

[Brian Kirby]

What is the black block on the rear panel, on the bottom edge of the red decal, just to the right of the larger hole? Could it be a cover over a bike rack fixing? It seems not to be OE, as I can't see similar on pictures of other 520 back panels. Possible source of ingress?

 

I had first thought the problem might be a badly sealed shower, but the corrosion is the wardrobe side where, on the face of it, there is no source of damp from inside. I don't like the look of that line of corrosion above the rear lights, have you tried probing the floor from below in that area?

 

I had in mind that you'd need to cut away the inner wallboard, not just the wallpaper. You really need to be able to see the state of those panel edge frames where the side and rear panels butt together. If the side panel isn't corroded, and if the (presumed) rotten frame/s is/are cut out and replaced with sound wood, I get the impression that re-skinning the rear wall (or substantial part thereof) would give the best repair.

 

I'd suspect that if that black block isn't the source of the ingress it will be the cover strip over the rear corner side seam that is the source. Most probably due to mastic sealant that has dried out, shrunk, and cracked to let water into the joint. Must of these strips are screwed on and stainless steel or aluminium screws are a bit of a rarity. When sheradized steel screws get wet they quite soon corrode, the screw holes open out, and the wet gets into the frame and beyond. If you have to tackle that job, you'll really need to get the van under cover. Friendly farmer's barn somewhere? Then you can take your time unaffected by weather.

 

It'll be a big job, and difficult, but not insurmountable. You'll need to eliminate everything that has corroded and replace it with sound material. I'd also be inclined to remove all the joint cover strips, clean them up, re-bed them on a decent sealant, and re-fix with s/s or aly screws (whatever you do, don't use brass!), but leaving the rear panel joint strips off. Once you've achieved that, I'd be inclined to take the van to a specialist repairer to get the rear professionally re-skinned. It is a big sheet of aluminium, too large to handle single handed, and there is a skill in pulling it tight into shape, otherwise it'll look baggy! But, if the rest is sound you should still end up with a cheap little van, albeit at some cost and after a lot of effort.