Thinking of building a touring trailer: looking for parts

Hi all,

I've been thinking about building a decent cargo trailer for the purpose
of long-distance touring.

By long distance: well right now I've got the idea of a trip down the
Barry Way from Jindabyne through to the Great Ocean Road. That idea is
just "pipe dream" status right now.

There's also the trips I do to assist in emergency communications for
Brisbane Area WICEN, e.g. each year we go up to Imbil to run checkpoints
for the International Rally of Queensland car rally as well as numerous
horse endurance ride events, and one or two Bicycle Queensland events.
So being able to do those without relying on someone else for transport
would be good too.

Intended terrain would be mostly "on-road", where "road" can vary from
good quality bitumen through to state forest fire trails, etc.

I have a Croozer cargo trailer which is mostly okay, but I'm concerned
about a few things:

- the wheels are a small less-common size and so getting tubes and tyres
will be a pain.
- it has a 30kg load limit: I'll want to carry water and food along with
some camping gear.
- my particular trailer is showing signs of wear and tear.

I have a couple of bikes, but the one I have in mind to go touring with
is a Giant Talon 29ER 0. I've upgraded the wheels on it and have the
original stock 29" wheels it came with.

I figured it would be a good idea if the new trailer I built, used
compatible wheels, so that should disaster strike, I can swap things
around and it saves on the number of spare tyres/tubes I need to carry.
The 29" tyres should be easier to source too.

Problem being: most of these type wheels are sold as a front/rear set.
I know I can get them overseas individually (Wiggle were advertising a
Shimano front wheel for around the $140 mark).

Does anyone know places in Australia that sell 29" front-wheels at a
reasonable price? Any places sell used wheels?

On the actual trailer design, I've been fiddling around in OpenSCAD
modelling various aspects. At the moment I'm thinking of doing it with
box-section aluminium, as 20-25mm section is pretty common and seems to
have quite a bit of strength.

Joining the sections will be the challenge though: a good design here
would be one that is reasonably robust, but can be fixed with a minimum
of tools if things break. For this reason I'm looking at bolting the
sections together.

I note places like Bunnings sell 25mm section and a range of plastic
joiners (QubeLock/Connect-IT brands): does anyone know how strong these
are or know of where one can get aluminium equivalents? Anyone tried
building something with this stuff for a mobile situation?