chassis moounted roof racks

Hi OziExplorer,
thanks for that info, especially about the stability of the punt.Does the problem occur when you are under way, into a chop or cross swell, or is it from getting the weight all on one side and over she goes?
You mentioned the chassis mounts in front. Do you mean the very front of the chassis, or the rear cross beam that supports the gearbox? It is conveniently located towards the front of the front doors, so a bracket could be fitted to allow the pipe to go in front of the doors and then follow the windscreen pillars
Grade 350 extra light gal; what is the recommended wall thickness and pipe diameter you would have used? Would it be any different for black pipe?
I neglected to mention that I have a chieftan canopy which is 100 mm higher than the cabin roof. I am considering suspending a basket over the cabin of the car, and so the ring frames would be perfect to support it; and the 100 mm depth probably becomes 150 mm by the time the rear bar is in place, which gives enough space for the basket.
Now its time to draw up some plans. Do you know any one in the Sydney region that does this kind of work professionally?
Once again, many thanks for the info. It is much appreciated.
Sails

Yes, I meant the very front of the chassis. Once you put a bend in to come off the side of the chassis, it takes substantial bracing to take the side flex out of the unit. You are basically forced to use roof attachments to take out the side flex. The other issue today is that cabs are 'more' rubber mounted/flexible than previously, and that would need to be taken into account. No problem with the canopy, but you are going to be forced to drill some mounting holes in the rear. If you put hard sheet rubber underneath the mountings, when you remvoe it, the holes can be easily masked. Every mounting hole/plate needs to have a backing plate.
40NB Extra Light Gr350 pipe is from memory 2.3mm wall thickness. 40NB Extra LIght Gr350 is equivelent to a heavy wall in a Gr250. We used to bend a front and back bow in a large radius bend (6 pipe dia) and then proceed from there with lighter pipe for bracing and ancillary mounts. RHS cracks with flexing on vehicles, and pipe is far superior. I would highly recomend you make the basket to go under the tinnie. This means you can lock the tinnie on, and it will also keep the stuff in your basket safe. You can make the tinnie hinge up easily, so if you need to get into the basket, it will be quick. Having a basket out in the free air on its own will cost you a *fortune* in fuel consumption. If you keep the tinnie with nose down close to the top of the windscreen if possible, your fuel consumption hit will be minimal. A poor roof rack can cost you up to 3km per litre extra fuel consumption - amazing, but true.

Sails

I have to say that the extra light GR350 40NB is not equivalent to the heavy wall in GR250. The heavy wall is 73% stiffer, 26% stronger in bending and 76% stronger in axial loads. Even the normal wall GR250 pipe is still 46% stiffer than the extral light GR350 for only a little extra weight, and still has better load carrying than the extra light. Given that your going to be no where near the load capacities of the section, the more stiffness you can achieve from the section the better the rack will be.

Hi OziExplorer,
thanks forthe reply, your cautions re the punt and info on the rack are much appreciated, and Its great to see the differing opinions that are coming out about the steel. I'll be taking the punt down to my local lake and doing some stability tests to determine if it is a risk that I want to carry, or maybe sell it and get a "V" bottom.
I'll take the details you gave to my local Steel Store and price it up and see what I can come up with in design.You dont have any plans sitting around for a '98 Rodeo roof rack ,do you??
Just an aside, while on the forum I came across an item relating to Rodeos cracking their chassis' which was a bit of a concern. I found another web site from a Subaru car club that did the Simpson with a rodeo dual cab in company.They called the rodeo the Pie truck,due to the ute load set up. there is a photo on the web site of the Rodeo with the rear end sitting on the ground at 45 degrees to the cabin; chassis broken clean in two.
So the weight that goes onto the vehicles really does have to be taken into account.
GM of course put it all down to vehicle abuse!!
cheers,
sails

And oziexplorer, we all just love the know it all. As I said, the additional stiffness of GR250 far outweighs its extra weight. And at only 1.7 kg/m, I do only call it little. If this additional weight causes GR250 to self destruct, than its not worth building a rack out of either grade cause what load could you put on it.

The opposition racks probably work caused they copied your layout and how it all fits together. Have a look at any item that fails. Its never the member, its always the connections and layout that lead to its failure.

I've probably been making things longer than you been around, so why don't you let everyone have their opinon and let the truth come out.