Stimie,
as Dr.G said it was a lot of mock ups that got us to where we are.
I am pretty good at thinking in 3D but the shape of the belly tank really is a trick. No matter which way you draw it there is always some plane disappearing in a way that is hard to conceptualise.
Having a 3d CAD model certainly helped but at the end of the day it was as every other car builder has done, placing pieces in roughly the right position and sitting in it with your helmet on and making engine noises.
We made a 1:10 model with a vac formed shell which we could quickly chop change and reweld some rod steel to sort out a cage that was reasonably efficient. This like the Cad model helped try out some options prior to commiting to big stuff but it was hard to get your head around the scale of the thing.
The cardboard and rough 1" steel 1:1 phase was probably the most educational. You could get in it. We could place the bits we had on it in roughly the right position. We painted the outline of the tank on the floor. Most importantly we wanted it to comply with the safety rules and maximise our driver space and engine space at the same time.
Below are some photos of it in this stage. One side is a bit different from the other. As this was always going to be a throwaway thing, we could jump in and try differet ideas. Just chop and weld / tape without worrying about strength etc. A quick and ultimately time saving way to do it, although we did get frustrated with the lack of progress at actually building the real thing, it has paid off in spades at the end.
With that said, as Go said, the design of these things is a living process. It grows and changes as you build. Sure there a few elements like an appendix in the car that were designed and built for a previous idea and now been superceded... if we were building another one we would be so much faster and different again.
That is what we are looking at this year, now that it is complete, looking at it and asking how can we do this or that better.
That is indeed the question to ask other builders. We are only happy for you to go one better and not make the same mistakes that we did.
The advantage you have Stimie is all the other cool tanks already built on your P-38. We are the first to build on a Canberra Bomber (please correct me if I'm wrong and send photos immediately!) and we didn't want to cut it up unduly. This meant working blind for a long time as we didn't have a top and bottom shell to build in. In hindsight we should have made a quick fibreglass copy which we could have used as a guide. You have this option as I presume your tank is divided down the middle already? (Is it from the Kelly heritage?)
Not having a real world test up our sleeves hurts this process and so we can only comment on our build process at present.
Thanks all for your comments. Latest development is we have just bought the bits for a trailer. We are going to build an enclosed unit with some ramps that the car can sit on so we can work on it at a reasonable height at the salt.
(Editor: we have started a thread on the trailer and all things trailer elsewhere in the build diaries section).
Rev.H+