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Caravan construction


Ukzero
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When we turned our attention back to caravanning four years ago after a 17yr break we weren't sure what to expect in terms of evolution of the basic construction methods.

At first glance, on our first visit to the NEC show after many years away, caravans appeared to have more modern styling, more modern and more equipment overall, but were still the same boxes with plastic end mouldings that we would recognise from the turn of the millenium.

 

Initial selection of potential models to choose was based on things like layout, perceived solidity of interior construction and (oh how shallow, exterior styling).

At this stage we weren't considering such details as construction methods/marerials. This came later.

 

I have long been familiar with the limitations of large unreinforced plastic mouldings. I get that they are quicker and easier to produce, but reinforced panels will always be much stronger, so if we found two 'vans neck and neck in our wish list that would be a factor. So I am very much in the GRP is good ABS is bad camp.

When I began to look deeper into the actual construction and did research (including looking at CT) other major differences became apparent.

 

We eventually chose a Swift Elegance and its lack of wood was certainly a factor.

This was for aesthetic as well as "water ingress resilience" reasons. There were none of the taped joints covering the edges of the ply sheets for example.

However, this was not an overwhelming endorsement of Swift - opting for a structure with "water ingress resilience" suggests that water ingress is foreseen at some point.

 

The UK has composite panel manufacturers which could mean that all brands conceivably could go "woodless" if they chose to do so.

However, such panels do cost more and so like most things, I guess it's very much a commercial decision.

 

The buying public still buy caravans built the "old way" and as long as they sell the incentive to change is less than the incentive to wow us with new interiors and layouts.

 

I find the contrast between two of the smallest manufacturers fascinating.

Both Vanmaster and The Fifth Wheel Co offer caravans which can cost £70k+, but are poles apart.

Vanmaster appears to celebrate traditional craftmanship, traditional interiors and very traditional construction.

The Fifth Wheel Inos caravan has the latest woodless** construction, giant slideout, etc.

We are having an Inos built as I type. Given its huge cost I confess to being reassured by the built in "water ingress resilience"!

 

If your caravan never leaks and is properly weather sealed (including the underneath), then the presence or absence of wood is neither here nor there.

I'm sure many caravans don't leak, but if they do, the construction method then determines if the problem is a nuisance or a major problem.

Would I chose a woodless caravan I didn't like over a wooden framed one I loved? Thankfully not a choice we've had to make.

 

** It turns out that the Inos floor does have a thin plywood layer, but the floor is GRP lower skin, foam core, aluminium sheet (much thicker than used on some caravan sides) then thin ply top (to allow better bonding to vinyl flooring). Consequently, even if the ply became sodden the floor integrity would be unaffected.

 

 

 

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As you say no wood no rot but I've seen reports of leaks in all makes and old vans still going strong. Buy what suits .

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I enquired if Bailey a couple of years ago as to why they still insist on using a plywood floor when everything else is totally wood free. Their response was that a composite floor would be a lot heavier to obtain the same strength (really??) and cost considerably more.  I was even more surprised when I asked what treatment was given to the underside of the plywood floor.  See below ! 

 

 

Good Afternoon,

I have checked with Bailey customer services on this as we do not sell panel treatment.

Bailey customer services have advised that “we only paint them with a black emulsion”

Apologies however, this is not something that we supply.

Kind Regards,

Becky Tidd

Customer Service Advisor

Dear Mr Xxxxx

I understand that you believe our floor panels are treated during the manufacturing process and I can clarify that this is not the case.

I trust this clarification has been helpful.

Regards

Darryl Wandless
Customer Services Co-ordinator

Experience is something you acquire after you have an urgent need for it.

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Wood free construction is not the deciding point for us, but it would make Swift models more attractive to us other things being equal. At the end of the day you have to live with the caravan and so layout and live ability must come high up and Swift do have a model for most of us. Customer service also is a consideration, and on that I think most makes fail.  A far better service might change many peoples choice, but no firm has produced that.

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38 minutes ago, Mr Plodd said:

"a composite floor would be a lot heavier to obtain the same strength (really??) and cost considerably more"

 

Plywood is indeed very strong and light (and yes I am a fan of the Mosquito) and can be said to be the original carbon (based) fibre composite.  In caravans with GRP floor skins the skin is very thin (about 2mm in our Swift) to keep weight and cost under control and will have a lot less torsional strength on its own. This is less of an issue once part of a suitably designed laminated floor panel, but this will be at a cost.

 

47 minutes ago, Mr Plodd said:

I understand that you believe our floor panels are treated during the manufacturing process and I can clarify that this is not the case.

 

An untreated plywood bottom skin exposed to road spray et al doesn't inspire confidence. I guess the theory is that being exposed to the air it will dry out between "wettings" and so limit degradation. The problem here will be if there are areas that get wet round the edges whenever it rains. 

 

1 hour ago, Jezzerb said:

As you say no wood no rot but I've seen reports of leaks in all makes and old vans still going strong. Buy what suits .

 

Which is why it's not clearcut. Most people do "buy what suits". Far better to live with a 'van that you like and meets your requirements than one you don't like but might be better off if it leaks :)

 

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13 minutes ago, Wildwood said:

Ukzero, The problem seems to be with leaks rather than road spray which as you say will dry out fairly quickly. 

 

That was the argument Bailey put forward, which does seem to be reasonably true. I am still feeling inclined to get underneath mine and apply some form of treatment, be that decking type oil or a paint on fence treatment but, as others have said, it tends to be corners=edges that suffer and they are areas it’s difficult to apply any treatment to. 

 

Thoughts? 

Experience is something you acquire after you have an urgent need for it.

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24 minutes ago, Wildwood said:

Ukzero, The problem seems to be with leaks rather than road spray which as you say will dry out fairly quickly. 

Good Post

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11 minutes ago, Mr Plodd said:

 

That was the argument Bailey put forward, which does seem to be reasonably true. I am still feeling inclined to get underneath mine and apply some form of treatment, be that decking type oil or a paint on fence treatment but, as others have said, it tends to be corners=edges that suffer and they are areas it’s difficult to apply any treatment to. 

 

Thoughts? 

 

As it happens, yes.

I built a wood cabin for my wife, along with custom fencing and a couple of sheds.

Although the wood is tanalised I wanted to protect it but allow it to breath.

Last Summer I used this stuff: https://www.toolstation.com/wood-protective-treatment-5l/p68513

It has super low viscosity and soaks rapidly along the grain into places you can't reach. It also soaks right into the wood substrate giving excellent protection. Being clear also helps reduce staining - but I would keep it off white plastics - should be easy enough under the 'van. I had some doubts, but the stuff is brilliant - and not that expensive. As it is so runny I would consider spraying it, or you'll end up with a waterproof arm where it runs down the brush!

Edited by Ukzero
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There is a problem with deeply penetrating wood preservatives.  It is possible they will attack the bonding agent in the ply itself.  Please make sure they are warranted for use on Exterior ply.  

 

 

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My local Woodyard used to give a 25 year guarantee on their own tantalised timber. Due to so called environmental legislation they can now only guarantee for 10 years and you cannot buy the good ole green liquid anymore. So instead of your fence lasting 25 years it will now only last less than half that….. 

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The Knaus water ingress warranty on my van requires an underseal product to be applied at each annual service - using a special spray can obtained from Knaus and each application is recorded with them. However the application is only required on the edges and joints of the underfloor construction to seal the panel edges. I guess this amply illustrates where the manufacturer believes any potential vulnerability is. As suggested in previous posts the main flat surfaces are pretty water resistant and will readily repel water and dry out.

Life is not a rehearsal . . .:)

Porsche Cayenne S Diesel & Knaus StarClass 695. Previously Audi S4 Avant & Elddis Super Sirocco

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2 hours ago, Mr Plodd said:

 

That was the argument Bailey put forward, which does seem to be reasonably true. I am still feeling inclined to get underneath mine and apply some form of treatment, be that decking type oil or a paint on fence treatment but, as others have said, it tends to be corners=edges that suffer and they are areas it’s difficult to apply any treatment to. 

 

Thoughts? 

I had Bailey pegasus with the dreaded damp o/s rear corner  i repaired that  (or so i thought ) and decided to paint the whole underside of the floor with a bitumastic paint fortunately i never got round to it because i found out the Bailey use emulsion paint  purely because it allow the surface to breath and dry out , not sure if bitumastic paint would have been counter productive because if applied correctly the floor wouldn't need to dry out ?  

I never was successful with the corner repair when i part exchanged it the corner had a damp reading of 56% ! and they knocked off £500.00  .

Edited by lazydaze
missed word
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2 hours ago, Flatcoat888 said:

My local Woodyard used to give a 25 year guarantee on their own tantalised timber. 

 

.????? :rolleyes: :rolleyes::rolleyes:

 

Autocorrect/spell strikes again ;)

Experience is something you acquire after you have an urgent need for it.

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1 hour ago, Lagerorwine said:

Also. would anything that penetrates deeply, also affect the bond between the ply and foam?

If anyone had a core from, say drilling a hole for an extra vent, they could do a test.

I kept one or two cores from our Swift, but it's got no wood in it....

One point I would make is that if the preservative soaks right in in some places, so will water in time.

I could certainly soak some ply in the stuff if anyone is serious about considering using it.

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27 minutes ago, Mr Plodd said:

 

.????? :rolleyes: :rolleyes::rolleyes:

 

Autocorrect/spell strikes again ;)

😂😂

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Hi,

We have a Coachman & on a factory visit some years ago i asked about covering the underside of the floor . The answer was an emphatic DONT !

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17 hours ago, david 1220 said:

Hi,

We have a Coachman & on a factory visit some years ago i asked about covering the underside of the floor . The answer was an emphatic DONT !

I certainly would not advocate any impervious covering as this could indeed trap water in doing more harm than good.

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