Timber framed caravans - thoughts please?

Submitted: Saturday, Sep 27, 2014 at 14:54
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Been looking at buying a van around the 16' mark. Thought we had what we were after but then told it uses a Meranti timber wall frame construction. So just wondering about this?
Is it still common construction? I must admit I thought they'd all be metal / composite now.
My main worry is water ingress and /or condensation causing rot.
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Reply By: Allfour4x4 - Saturday, Sep 27, 2014 at 15:08

Saturday, Sep 27, 2014 at 15:08
Forgot you can't edit.
I should have added the van we're looking at is a new one
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Follow Up By: Member - DW Lennox Head(NSW) - Saturday, Sep 27, 2014 at 15:33

Saturday, Sep 27, 2014 at 15:33
I have the same feeling about Meranti. It is cheap to make a caravan from but once water gets to it then the fun begins.

I am impressed by the construction of the Avida Sapphire or Topaz. All composite with aluminium extrusions to join up. Another advantage is ever it gets damaged it is fairly easy to repair. There are 3 types of suspension to choose from.

Just my thoughts

DW
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Reply By: bluefella - Saturday, Sep 27, 2014 at 15:31

Saturday, Sep 27, 2014 at 15:31
Meranti is a problem if you get a leak you don't know about, it can rot out, maybe they still use it because it is a cheaper alternative to other framing materials? I don't know the cost difference say between aluminium & meranti?
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Follow Up By: bluefella - Saturday, Sep 27, 2014 at 15:33

Saturday, Sep 27, 2014 at 15:33
Should add there has been many discussions on new vans leaking on this and other forums.
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Follow Up By: TomH - Saturday, Sep 27, 2014 at 16:24

Saturday, Sep 27, 2014 at 16:24
Wood is Ok if the van is built properly and alloy will get corrosion as well.

It all depends on the quality control which industry wise has proved to be a lottery.
Read this thread for horror stories on any type of construction

http://www.caravanersforum.com/viewtopic.php?f=2&t=12286
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Follow Up By: Member - DW Lennox Head(NSW) - Saturday, Sep 27, 2014 at 16:50

Saturday, Sep 27, 2014 at 16:50
The horror stories on that forum confirm my thoughts about Meranti as a construction medium.

I note the composite one was clad with aluminum sheeting not fibreglass.

DW
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Reply By: Ron N - Saturday, Sep 27, 2014 at 17:33

Saturday, Sep 27, 2014 at 17:33
If there's one thing that stuns me about all those horror pics of the caravan damage and repairs - it's the constant use of timber joins, that involve butting one piece of meranti to another at 90 deg - then "securing" that join with 3 or 4, 10 or 12mm wide, air-driven staples!
Talk about crap construction methods!! There's no sign of any glue even, to back up the staple-tacking!
It's little wonder entire sides or ends are often blown out of vans by passing semi's doing 100kmh!
AnswerID: 539593

Reply By: Allfour4x4 - Saturday, Sep 27, 2014 at 17:56

Saturday, Sep 27, 2014 at 17:56
I wish I hadn't looked at construction now :-)
Guess I'd better pretend I never saw it as all three makes we've thought about use it! New Age, Goldstream and Retreat vans. Hopefully as above, if it's done right it should be OK.
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Follow Up By: TomH - Saturday, Sep 27, 2014 at 18:52

Saturday, Sep 27, 2014 at 18:52
I have owned two vans The first with Moranti and the second with Alloy.

The first van was by far the better one and more solid than the second.

I did have to get an inner wall sheet repaired when the sealant around the toilet cassette let go and water got inside the wall.
Not the Moranti's fault.

Caravans are like kitset garages The wall sheeting is the strength rather than the frame. Also notice how almost all vans have a small cross wall near the centre of the van. Without that there is little rigidity in just the outside walls, Like a cardboard box it would wobble but put the crosspiece in and it becomes more rigid

I think only Bushtracker weld the alloy frame to give it strength.
Coromal use a very light alloy angle which on its own has little strength.
You can bend it with your fingers and they use light rivets at joins and not a lot of them.
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Reply By: Member - DOZER - Saturday, Sep 27, 2014 at 19:01

Saturday, Sep 27, 2014 at 19:01
Ants ate my wood framed overlander away,not sure if i got them from NT or the gum trees inmy front yard, but they had a nice feed...
b4 you bag me out, walk a mile in my shoes, then your a mile away and have my shoes :)

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Reply By: wholehog - Saturday, Sep 27, 2014 at 19:40

Saturday, Sep 27, 2014 at 19:40
As mentioned above, many of the cheap end caravans are meranti timber framed. The strength is in the outside sheeting.

Aluminium is not without its problems. Is the aluminium just extruded angle or RHS box section, how is it joined, rivets which stretch or welded.

Bushtracker is the only manufacturer I believe that uses RHS aluminium box section and is welded.

In the end, its caveat emptor....let the buyer beware: the principle that the seller of a product cannot be held responsible for its quality unless it is guaranteed in a warranty.

...then the argument starts about the implied "warrenty".
AnswerID: 539599

Follow Up By: TomH - Sunday, Sep 28, 2014 at 08:34

Sunday, Sep 28, 2014 at 08:34
Not only cheap vans use Moranti Mine was a Roadstar and certainly wasnt cheap.

The Coromal which is a cheap mass produced model uses alloy.
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Follow Up By: wholehog - Sunday, Sep 28, 2014 at 20:10

Sunday, Sep 28, 2014 at 20:10
Coromal Alloy in what form..and guage, and how was it held together ?
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Follow Up By: TomH - Sunday, Sep 28, 2014 at 20:37

Sunday, Sep 28, 2014 at 20:37
Very light box with rivets at the joins but very small ones Box was very thin section as well
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Reply By: Ron N - Sunday, Sep 28, 2014 at 13:04

Sunday, Sep 28, 2014 at 13:04
The greatest single feature in any van that you need to examine is how well it is designed to resist leakage, and how well it's sealed to resist leakage.

I've owned more than a dozen vans that were all used for contracting work and all were built from the mid 1950's to the mid-1980's.
I had several "Modern" vans that were built like brick dunnies - but they used wood for the frame.
All the vans I owned ended up suffering from leaks and wood rot. Silastic was unknown when those vans were built, they used mastic (Bostik) that dried out and became hard.
Modern designs have progressed substantially as compared to older vans, with far superior materials - but the problems of poor workmanship, and poor design, are still with us.

I personally think the old vans were better built, as weight was less of a concern and blokes were still tradesmen then with a 5 yr apprenticeship behind them.
Nowadays, the manufacturers hire any dole-bludger off the street who can hold a staple-gun, and put him to work on van construction.

I worked with an old body builder for a while (now long-dead) who built van bodies. He showed me a lot of clever thought that went into his van bodies - which suffer from problems identical to 'vans.
One of his tricks was folding a lip on the top sheeting so that the lip went over the top edge of the body.
This prevented water ingress into the body as compared to the poorer body designs, where the sheet was just laid flat on top with sealant under it and then pop-rivetted into place.

The simple fact remains that steel and aluminium are stronger and longer lasting than wood in nearly every application.
The only reasons wood is still used, is for weight saving - and for better resistance to vibration and impact.
Wood won't fracture like steel and aluminum will on constant rough roads, it has "give" in it. However wood performs very poorly in any exposure to weather or high temperatures.

If you use wood, no matter what you're building, it has to be totally covered and protected totally from moisture ingress, and extremes of temperatures.

If a caravan design doesn't show excellent attention to water-shedding in its design, along with 100% waterproof sealing - and it has a wooden frame - then you're going to have trouble and expensive repairs within a few short years - unless you spend all your time in a dry area, and keep the van totally covered any time it's not being used.
AnswerID: 539624

Follow Up By: Allfour4x4 - Sunday, Sep 28, 2014 at 14:10

Sunday, Sep 28, 2014 at 14:10
Yes, agree with all of that!
Ive looked at quite a few van builders lately in the course of deciding what to buy as our first van, and the majority are timber based.
I think your bang on in saying they need to be stored under cover when not in use, which for us realistically means maybe 90% of it's life. Biggest concern for me is more the condensation factor within the wall structure with temperature differences...some modern house designs are suffering with the same problems.
Only seen one so far that says it uses treated timber frame, and that probably doesn't extend to the ply etc.
It's a bit of a dilemma when these things are costing 50k and up, I'd hope to keep it for a while not be concerned with trading it in every few years.
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Follow Up By: Shaker - Sunday, Sep 28, 2014 at 21:09

Sunday, Sep 28, 2014 at 21:09
How do high temperatures affect timber construction?

I have seen timber framed houses that have had a section burnt down & then repaired & rebuilt, whereas a steel framed house with similar damage had to demolished due to the heat of the fire buckling the whole frame!

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Follow Up By: Allfour4x4 - Sunday, Sep 28, 2014 at 21:40

Sunday, Sep 28, 2014 at 21:40
Not high temps, temperature differences. If your in cold conditions with heaters inside or cold nights and hot days, you'll get condensation forming.
An example in housing is the use of Polystyrene rendered cladding, particularly with the modern trend for flat roof construction. If there is no ventilation between or through walls and roof, moisture forms in the walls causing all sorts of problems.
Been going on for yonks, but recently for that example, there are new installation methods / regulation being adopted such as fixing the cladding onto channel or perforated strips to allow air flow.
Can't se any reason why vans wouldn't do exactly the same thing.

Not trying to scare monger or start a war, just asking questions for my own sake.
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Follow Up By: Ron N - Sunday, Sep 28, 2014 at 22:12

Sunday, Sep 28, 2014 at 22:12
Shaker - Constant high temperatures (high 30's/low 40's) dry the all the moisture out of the wood, until it starts to split and fall apart, and it then loses its strength.

Kiln dried timber (seasoned timber) is dried until the optimum moisture level is reached - usually around 15-20%.
As this drying process takes place, the wood cell structure changes and the wood actually toughens up and increases in strength.

Any further removal of moisture from the timber results in the timber strength decreasing rapidly, and severe splitting then starts to take place, thus severely weakening the structural strength of the timber.

This type of failure is particularly noticeable with timber that isn't grown in Australia, but in semi-tropical and tropical forests.

You might have seen some Indonesian furniture that has fallen apart when the high-moisture content Indonesian wood, has suffered a severe decrease in moisture content in our hot dry climate.

This is a common event, I've seen quite a bit of Indonesian furniture thrown out, when this happens fairly regularly.

Allfour4x4 has also mentioned a good point about the condensation buildup which can penetrate any exposed timber and this causes fungi and moulds to grow - and in the worst cases, causes "dry rot".

"Dry rot" of course, has nothing to do with dryness, it's actually timber cell structure collapse caused by the fungi digesting the timber.
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Follow Up By: Ron N - Sunday, Sep 28, 2014 at 22:32

Sunday, Sep 28, 2014 at 22:32
The timber in the timber house would have survived admirably because the temperature spike was shortlived, and any timber damage would have been confined to smoke damage on the outside of the timber, or possibly even involved some modest charring.

A shortlived high temperature event like that has little effect on the moisture content of the wood. It takes weeks of elevated temperatures to dry out the entire thickness of the wood.

Some European companies are making huge panels from kiln dried softwood beams that are then cross-laminated and glued together with highly durable adhesives.

They use thick finger-jointed spruce beams that are laid crossways in at least 3 layers, and the panels are then subjected to hydraulic pressure to bond the whole lot together.
Panels can be produced up to about 3M wide and 16M long, and they're usually a minimum of 75mm thick.

These heavy timber panels have been proven to be very fire resistant due to their heavy cross-section and density, and they merely char on the exterior in a fire, with the panel strength relatively unaffected.

Google "cross-laminated timber" and you'll get a lot of additional info.
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Follow Up By: Shaker - Sunday, Sep 28, 2014 at 22:49

Sunday, Sep 28, 2014 at 22:49
Ron, with all due respect, I was probably laminating timber before you were born!
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Follow Up By: Ron N - Monday, Sep 29, 2014 at 00:43

Monday, Sep 29, 2014 at 00:43
Good-oh! Then you shouldn't have needed to ask the question!
You were laminating timber in the 1940's?? Geez, you must be an old fart, then! Join the club! LOL
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Follow Up By: Shaker - Monday, Sep 29, 2014 at 13:11

Monday, Sep 29, 2014 at 13:11
Ha ha Ron , you got me!
Actually it was in the 60s when I was building moulded timber boats where almost everything was laminated, hulls, deck beams, stems, coamings, thwarts etc.
Regarding the posts about the timber losing its moisture content, I must inform all the timber boat owners of this problem, & certainly must check that the North-West wall of my house hasn't crumbled & fallen off!

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Follow Up By: Ron N - Monday, Sep 29, 2014 at 15:24

Monday, Sep 29, 2014 at 15:24
Not much fear of timber boats losing their moisture content when they're in the water, eh? [;-)

But ... I've seen an awful lot of bondwood ski-boats in farm sheds that crumbled and fell apart - because the ski lakes only filled once every 5 years!! [:-)
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Reply By: Grumblebum and the Dragon - Monday, Sep 29, 2014 at 12:59

Monday, Sep 29, 2014 at 12:59
Both timber and aluminium framing can be crap. It all depends on the quality of the materials, design and fitness of purpose for the job. El cheapo aluminium angle iron secured with a few pop rivits is just as bad as small Meranti joins just butted together with a few staples.

Of the two choices I prefer aluminium framing. Bushtracker do it very well.

John
AnswerID: 539682

Follow Up By: Member - DW Lennox Head(NSW) - Monday, Sep 29, 2014 at 14:18

Monday, Sep 29, 2014 at 14:18
Has anyone had anything to do with the Avida Caravans? Either the Sapphire or Topaz with any of the 3 suspensions.

DW
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Follow Up By: TomH - Monday, Sep 29, 2014 at 16:26

Monday, Sep 29, 2014 at 16:26
Yes but Bushtracker weld them and build them as off road vans and charge accordingly.

Big difference to a 16' normal van built to a price to compete with heaps of other equally dodgy models.
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Follow Up By: Allfour4x4 - Monday, Sep 29, 2014 at 18:56

Monday, Sep 29, 2014 at 18:56
I was wondering about Avida myself...sound good.
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Reply By: MEMBER - Darian, SA - Wednesday, Oct 01, 2014 at 16:17

Wednesday, Oct 01, 2014 at 16:17
Well....my van is built in a 'near traditional' manner with a timber frame.....the arrangement being....ply inner / timber frame / ply outer / metal outer. Over 5 years and plenty of outback travel, because we've had no issues with the build I've formed the view that this method is quite ok, but only if done by professionals taking all due care. Through monitoring our van club's forum, I don't recall other members having any significant issues with the frame quality or durability.
AnswerID: 539766

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