Caravan build 18ft

Submitted: Saturday, Dec 25, 2021 at 12:56
ThreadID: 143018 Views:3673 Replies:4 FollowUps:5
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I’m starting my second build (first was just an enclosed trailer with 3mm composite cladding)
This time around will be a caravan, would like to hear from others that have self built on what frame method they used and how they found it?

I have access to the below
aluminium channel, tube, etc - but can’t alloy weld
Steel rhs, shs - good supply, reasonable price - can weld this well.
Timber meranti - I work for a supplier of timber and should be able to get in quantity for reasonable price.

My thoughts at the moment is SHS/RHS frame in 20x20 1.6 or a mix of 25x50 and 25x25 in 1.6. With 500mm centres, 4mm composite cladding with foam insulation. 3.7mm caravan ply internal.

I’ve considered the weight and steel will be more but still under my target TARE

Done right, steel should have less impact if water leaked?

Should I seriously be considering timber frame over steel? Or aluminium given I can only rivet together?

I’m not considering the full composite panels as I am too far away from suppliers, they won’t ship? And I may make internal changes on the fly.. and cost would be about triple?

Any general thoughts on caravan frame?

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Reply By: Peter_n_Margaret - Saturday, Dec 25, 2021 at 19:10

Saturday, Dec 25, 2021 at 19:10
I have recently started my second OKA motorhome build. The first is now 16 years on the road and has and is giving stunning service.
It will be fibreglass sandwich panel, just like the first, but will be lighter. No other choice gives superior strength with low weight and quality insulation IMO.
The panel is typically 23mm thick. Roof is thicker and there is a special floor panel.
This method of construction contains no timber and has no frame.
OKA196 motorhome
AnswerID: 638914

Follow Up By: Gerard S - Sunday, Dec 26, 2021 at 11:43

Sunday, Dec 26, 2021 at 11:43
Peter...what's the work around for running wiring with the foam panel? Conduits from floor level or can you do internal runs?
FollowupID: 917753

Follow Up By: Peter_n_Margaret - Sunday, Dec 26, 2021 at 15:14

Sunday, Dec 26, 2021 at 15:14
This is part of a power point I prepared 10 years ago for some of these questions.
In general terms, all electrical wiring is above the floor and plumbing and gas is below the floor (where possible)

OKA196 motorhome
FollowupID: 917755

Reply By: Kazza055 - Sunday, Dec 26, 2021 at 12:14

Sunday, Dec 26, 2021 at 12:14
I would suggest that you also post this onto the Caravaners Forum where you will find a lot more members that have done what you want to do so should get more answers.

Just a question, why can't you weld Aluminum?

My father was a panel beater and built a steel framed van for the family back in 1968. It ended up weighing so much he was struggling to tow it with the family car.
AnswerID: 638920

Reply By: Bob Y. - Qld - Sunday, Dec 26, 2021 at 15:39

Sunday, Dec 26, 2021 at 15:39

Check out “Diy Caravan Build”, on Facebook. Few blokes are building, or have built, vans & you make pick up some helpful advice.

From my experience, I’d keep the inclusion of steel to an absolute minimum………..except for the chassis, running gear etc.

Good luck,

Seen it all, Done it all.
Can't remember most of it.

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AnswerID: 638921

Follow Up By: RMD - Sunday, Dec 26, 2021 at 17:52

Sunday, Dec 26, 2021 at 17:52
G'day Bob.
That is a good task to try, making your own van! I will look at the site to get ideas.
Just an observation and I have often seen it, is on the picture too, is, the solar panel on the front, so it gets hit by flying stones or bird strike to break the glass and the orientation is probably fairly useless to get charge into a battery. Very puzzling. Unless driving into the sun it would produce very little most of the time.
FollowupID: 917756

Follow Up By: Bob Y. - Qld - Wednesday, Dec 29, 2021 at 19:20

Wednesday, Dec 29, 2021 at 19:20
Yeah, noticed that too, Ross. He might be lacking in real estate for extra panels, hence the panels position? During the tourist season, we see plenty of vehicles, both towing & not, that have panels in a similar position, albeit at a more acute angle. Have never seen a damaged panel, but no doubt it happens, especially on one lane bitumen, or stony gravel roads.

As for solar output, if they park with panel in a northerly aspect, then performance should equal, if not exceed that of panels mounted flat on roof of van or canopy.


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Can't remember most of it.

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Reply By: Keith B2 - Sunday, Dec 26, 2021 at 22:15

Sunday, Dec 26, 2021 at 22:15
Hi Jason,
Can I put my hand up for the Epoxy Composite brigade?

You can see caravan manufacturers claiming to have a one-piece floor or a one-piece roof and maybe even a once piece wall. I built my van from honeycomb epoxy composite (about $100 and 4.4Kg per sq m) and finished up with a one piece caravan.

Everything in glassed in including the composite furniture and composite water tanks. It's dustproof, leakproof and vibration-proof. And it's quite light.

The downside is that it's expensive (particularly the paints, fillers, resins and adhesives), very very very labour intensive and needs to be planned out in detail well in advance. It took a lot of planning as well as ages to build. So don't go this way if you need it in a year or expect it to cost less than twice what you originally planned.

My chassis is steel with very few cross members and no stringers or outriggers, on a soft air bag suspension.

We have just done a 12 month lap in ours, down the Gibb River Road and up to Lorella Springs without any structural problems.

If you are interested, you can see my build on camper trailer build/Worlds Slowest Build. But you might have to register first.

AnswerID: 638924

Follow Up By: Dixie61 - Thursday, Dec 30, 2021 at 08:56

Thursday, Dec 30, 2021 at 08:56
Nice DIY job mate !
FollowupID: 917781

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