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Forum LockedAluminium or Timber framed caravans?

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Barry View Drop Down
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Direct Link To This Post Topic: Aluminium or Timber framed caravans?
    Posted: 03 July 2008 at 2:53pm

Hi evryone,

Am in the market for a new full sized caravan. Looking at Coromal Princeton or a Roma Elegance. Just wondering what experienced caravaners think of the aluminium framed vans as opposed to the timber framed ones.
Thanks.
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Wahroonga Farm View Drop Down
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Direct Link To This Post Posted: 15 February 2009 at 2:52pm
This is a big and interesting topic. There must be some more opinions out there. :)

One problem you see time and time again with timber is that if there is any moisture ingress, it will rot and the van will collapse in that area. Repair will be very expensive. It happens all to often. And some times you won't even be aware.

I suspect timber construction remains popular as it is cheap, very flexible and easy in manufacture.

My 1978 York 18' aluminium frame and gal chassis, remains totally waterproof and structurally sound, despite spending most of it's life in the weather.

However I'm sure there's many other issues, and maybe issues with aluminium frames coming apart?
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Direct Link To This Post Posted: 15 February 2009 at 8:55pm
Those with an informed opinion generally leave this one alone. You get the same biased replies that you get in a thread on whether Holden Vs Falcon is the better vehicle.

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Direct Link To This Post Posted: 15 February 2009 at 10:14pm
Now that's a cop out Smile

Clearly there's pros and cons between the two:

1. In production. What are they?

2. In end use. What are they?

Is there a difference in strength, cost, flexibility of design (design profile restrictions), reliability, longevity, resale etc ?

Manufacturers seem to rarely promote their frame technology?

Why?

IMHO I think it's the most critical component that a prospective buyer should understand?

Unfortunately recreational vehicles are about the gloss and glitz, not about the substance ... or is that heresy?

It's certainly not Fords and Holdens.
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Direct Link To This Post Posted: 15 February 2009 at 10:15pm
Perhaps only those with informed opinions need reply. Smile
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Direct Link To This Post Posted: 19 February 2009 at 11:09pm
The points you made above are quite valid Wahoonga and are what I was hoping would be covered when I posted the same question on another board.
Unfortunately, as Peter said it descended into a Ford v Holden like debate not relevant to the original question.Ouch
I think it best to rely on our better judgement.

David L
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Direct Link To This Post Posted: 19 February 2009 at 11:30pm
Perhaps this advert is telling. :)

You don't see them for timber vans.




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Direct Link To This Post Posted: 20 February 2009 at 9:35am
Of course today there is a third player. The foam sandwich construction method that more and more manufacturers are adopting. This method uses aluminum, polystyrene foam vacuum bonded to the internal linings and exterior lining that is generally a ply/fiberglass/gelcoat material.

However to date this is used mainly in the walls with roof sections still framed with either aluminum or timber. Of course it all comes down to what one is willing to pay. For me the Bushtracker frame pictured above would be my first preference if money was no object, then the mass produced foam sandwich method  and finally timber frame.

As an aside IMO I think you will see many manufacturers that build in timber exit the industry in the coming years if they don't move to the foam sandwich method due to labor costs. Are we already starting to see this?
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Direct Link To This Post Posted: 20 February 2009 at 10:40am
Yes that's an excellent point Supertramp.

Foam sandwich is both light AND strong providing an excellent caravan building resource.

Perhaps this NRMA link provides a sound synopsis of the various construction methods?

https://www.mynrma.com.au/cps/rde/xchg/mynrma/hs.xsl/caravan_structures.htm

And let's not forget the very considerable advantages of a hot dipped galvanised chassis.

Caravan structures

Caravans come in range of materials and structures. There are however, just two chassis types: the 'A'-frame chassis where rails taper out from the front to the axles and onto the rear corners. This frame supports a platform and body shell. The second type is the Rectangular Hollow Section (RHS) steel chassis which provides a complete frame for the body shell.

Aluminium frame


A most satisfactory caravan body. Aluminium tubing or extrusions are used for the framework, which is either riveted and/or welded together to form a skeletal frame for external aluminium cladding. This can be glued and/or riveted to the framework with styrene insulation, and a plywood lining is attached to the interior. This type of construction is light, strong, flexible and durable and it lasts for a long time.

Things to look out for: unsuitable grades of aluminium and/or incorrect welding techniques can cause frame cracking while the caravan is in use.

Timber frame

Timber frames are popular because they are easy to manufacture. This method can be either very good or very poor in relation to durability. Its success or otherwise depends on the type of timber chosen and the method of fastening timbers.

This type of body is usually made up of a timber framework with aluminium exterior sheeting, foam insulation and an interior lining of plywood.

Things to look out for: many timber-framed bodies have deteriorated due to the choice of timbers, glues and fasteners, eg staples. Water leaks in this type of caravan cause major damage and timber-work around doorways, windows, vents may rot and require extensive repairs.

When this type of van is incorrectly assembled it will not last, even with the best quality materials, particularly under rough road conditions. It is important to inspect exterior door, window and panel sealing regularly to ensure you find water leaks soon after they first happen.

Sandwich construction

With this type of construction a panel of exterior aluminium and interior timber ply sheet sandwich foam insulation material. The panel is bonded and is usually 20 to 25 mm thick.

Sandwich panels are used for caravan walls and windows, doors and other openings are cut out of the panel. This type of construction is considerably lighter than most and is quite durable when combined with a substantial chassis.

Fibreglass

With this construction, a timber or metal framework provides the basis for a fibreglass shell. Interior lining made from plywood or other suitable materials is attached to the basic body structure to form the interior walls and ceilings etc.

Things to look out for: while this type of body structure is quite durable, these bodies can be quite heavy and are subject to cracking when considerable body movement is experienced, eg on rough road surfaces.

Steel frame

This is where light Rectangular Hollow Section (RHS) steel tubing is welded to form a framework onto which an aluminium exterior cladding is fastened with foam or styrene insulation. The body interior walls are made of plywood.

This type of construction is usually very sturdy as long as the right materials are used with correct welding procedures. With adequate corrosion protection, this kind of van will give durable service.

Things to look out for: the major problems with this type of construction are excessive weight and corrosion over longer periods.

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Direct Link To This Post Posted: 20 February 2009 at 10:41am
And then there's .... suspension!
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Direct Link To This Post Posted: 20 February 2009 at 10:47am
And one more link on foam sandwich

http://www.nakedrv.com.au/Way%20of%20the%20Future.htm
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Direct Link To This Post Posted: 22 February 2009 at 12:21pm
I am a firm believer in the advantages of foam panel construction. It represents the highest strength for weight of any construction method. I have lived in a foam sandwich panel house for 34 years. It provides high impact strength & massive racking strength.
 
Don't ever get the idea that there are no disadvantages. Fixing fittings and furniture to the wall is a problem as there are very few firm anchor points. If aluminium is bonded directly to the foam on the external face the foam may fail in extremely hot conditions.
 
These matters aside I believe that within a few years this will be the overwhelming construction method for Vans.
 
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Direct Link To This Post Posted: 22 February 2009 at 3:41pm
Some valid points here
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Direct Link To This Post Posted: 22 February 2009 at 4:08pm
This thread has wandered a lot from the original question - timber Vs aluminium frame.

Getting back onto the original subject, I don't see any advantage of aluminium over timber. If you read the NRMA link given above you will see that you should be taking more notice of the constructors methods than the material. I think there "Things to look out for:" that were mentioned in the timber frame section that apply equally to aluminium frames, especially the second Paragraph.

The big omission in that link was the need for maintenance aspect of timber and aluminium frames. If you let the sealing deteriorate you get water ingress. The biggest problem with water ingress is the interior ply. A serious leak will damage the ply in either van. When this happens it will wreck either type van. As the furniture is generally attached from the outside before the skin is applied the replacement of the interior ply is equally difficult. The result with either style of frame is equal, water damage that will wreck a timber frame will write off either van due to interior damage.

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Direct Link To This Post Posted: 22 February 2009 at 4:21pm
Unfortunately any water ingress, even the tiniest amount, 'takes out the frame' in a timber van.

If there is continued water ingress, yes it will begin to show on the interior lining.

However in a timber van ... when it does show ... the damage is already done. Guaranteed! :(

Once dry rot has set in, you can kiss the van goodbye. And most of the time, you don't see it, until the van starts collapsing.

There's a lot of time bombs out there as this van restorer found. It started as a window leak and a floor repair, but quickly led to a complete rebuild.


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Direct Link To This Post Posted: 22 February 2009 at 7:00pm
I guess the real point is, as several folk have already suggested; that new timber framed vans, are fast disappearing.

Some my say good riddance, some may say for sound ecological reasons and others may be aghast. For some odd reason, timber framing has always been the backbone of Victorian van manufacture.

The more progressive manufacturers are moving or have moved to vacuum-bonded layers comprising welded aluminium tube, fibreglass, ply and polystyrene foam and are proud to display it on their websites.

Jayco

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So in some ways the choice for new van buyers is already made. It appears that in the not too distant future (amongst the big guys), there will only be:

1. traditional aluminium framed and clad vans or

2. bonded aluminium foam sandwich with an external fibreglass skin.

We know from very long experience that a well built 'type one' tends to just keep on keeping on.

It's probably a little too early to judge the longevity of 'type two'?

If you're in the market for an older van, I guess all the previous comments and opinion applies. Have it inspected by an expert. If there's any signs of leaks in a timber framed van, then run a proverbial country mile.

If you in the market for a new van; then I'd get some very pointed questions ready for the up and coming caravan shows. Embarrassed
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Direct Link To This Post Posted: 23 February 2009 at 11:40pm
Originally posted by Wahroonga Farm

ISome my say good riddance, some may say for sound ecological reasons and others may be aghast. For some odd reason, timber framing has always been the backbone of Victorian van manufacture.

 
I don't quite understand the comment about sound ecological reasons. If the ecology was to be the deciding factor then the only sustainable choice is timber. This is the only building material that can be replaced within a life time or less. I doesn't matter what else you select be it aluminium, fibreglass, foam, then you have moved into the realm of unsustainability.
i guess this is off topic, sorry.
 
Rod
 
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Direct Link To This Post Posted: 24 February 2009 at 6:02pm
Hi everyone
 
This is my first day on the forum and my first post.  I found this thread just getting familiar with the site.
 
By coincidence, I just finished reading an article in a mag I picked up called Caravan Tips and Techniques.  It reiterates a lot of what has been said here (especially the Holden vs Ford analogy).  Their conclusion is that it is not the material that matters but the quality and care of the construction.  A good wood frame will beat a bad aluminium one and vice a versa.
 
About the only definitive advice was that Bushtracker's welded box section aluminium can lay claim to being the best off-road frame albeit with a weight penalty.
 
Their conclusion was that Australian caravans have evolved to suit the country and our average makers are very good and our good makers above world class.  But then they could be in the pockets of the industry, who knows.
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Direct Link To This Post Posted: 23 March 2009 at 11:27am
Originally posted by miser

.... But then they could be in the pockets of the industry, who knows.
Read the article. :)

Unfortunately unbiased journalism, in a magazine which depends on the caravan industry for 110% support, is simply not possible ..... even a good journalist.

Perhaps you need to get him 'round the campfire after a few beers. :)
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Direct Link To This Post Posted: 23 March 2009 at 4:21pm
The Coromal is Aluminium and the Roma is Timber (Meranti), but that's not where it finishes.
As an ex van salesman and retired engineer I would choose the Roma over the Coromal any day of the week.  I know this will statement may start a bun fight, but that my personal opinion. Oh! And for the same price you can do even better than a Roma.
As for the argument Alum or Timber. It's a personal choice again, but timber vans are easier to repair any solid knocks as Alum frames tend to warp badly (Most are riveted NOT  welded) when hit in the corner a great many are then written off. The same knock on the corner of a timber vans can be repaired by replacing a piece of timber. I've owned both types over the years and now have another timer frame van (Galaxy).
Huge off road vans are made with both alum & timber. Vans like Explorer and Bushmaster etc are welded alum RHS.   Blue Healer (Sunland) and top of the line Phoenix uses New Zealand Long Grain Treated Pine for increased strength and flexibility. Ya can't do much better than that.
Well that's by two Bobs worth.
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