So, for the last couple of weeks I’ve been building the basic frame of my new shell for the sim. This bears some brief description before I launch off into the actual build experience.
Sim shells (aka enclosures) are many and varied in type. They range from simple DIY efforts right up to faultless replicas of the nose section of the aircraft being simulated. Some adventurous builders with cash to spare even buy the cockpit from a real, scrapped aircraft and remodel this. While this is obviously the most accurate way to do it, it’s also costly and requires lots of space and metalworking skills; none of which I have. Furthermore, having thought about it, I wasn’t concerned about the way the shell looks from outside. It’s what it looks like inside that counts. So no need to create a near-perfect replica of an aircraft shell, skin and paint it etc.
That decision made, I decided to go with a simple construction based upon the principle of the tent – a lightweight covering hanging from a stiffened frame. While my covering will be thin plywood rather than canvas, and my rigid frame will be softwood rather than guy ropes, the principle is the same. This avoids the need to create a complex load-bearing interlocking framework like Ron Rollo’s fantastic LearJet shell which you can see here. While Ron’s shell is a work of art, it also requires the ability to accurate cut complex curves that I don’t really have space or equipment to do.
A-frames, Take 1
The basic shell frame is an a-frame, made out of planed pine softwood at 96x44mm, which is more than strong enough to hold the weight of the interior. I went with a simple block-joint technique which suits my building capabilities. As the exterior part of the shell will not be visible from inside, it’s OK for it to be a bit rough and ready, and indeed it has turned out so. One lesson I’ve learned very well is that a jigsaw is not ideal for cutting thick pine beams. I really needed a mitre saw, but it was one expense too many at the moment, and while my circular saw would probably have done a better job the setup for doing mitre joints would be complex. The jigsaw was the easiest to use, but the main problem is that the blade bends – as it’s intended to, so you can cut curves – and so the joint surfaces were rarely flat. This, together with a general lack of accuracy in the cut, led to some less-than-perfect joints. They are all very secure, though. For the side beams, which have an angled and a straight part, I used a simple dowel-and-glue joint approach, together with metal plates to help spread the load along the beam.
Inaccurate joints require shims
Metal supports are used to keep the frame in place
Re-done A-frame bases
At first, I made the second frame a bit shorter than the first, giving me a 20 degree down-angle, but I quickly realised that this would not provide enough headroom to get into the sim without crouching too low for comfort. The angle was too steep and the cockit would be foreshortened. I re-did both frames to a comfortable standing height for most people, just under 2m, and then put in a sloping beam section to bring down the height before meeting the final front beam which marks the window slope.
A-frames, Take 2
It takes a little imagination to see exactly where this is going, but the progress so far looks like this:
A-frames and front pillar in place
Two more pillars will go in between the side pillars and the front pillar, which will mark the dividing point between the front and side windows. They will also act as the anchor point for the MIP framework inside.
Once the frame is complete, the process of skinning it begins. A full interior skin made of 6mm ply is envisaged, with more complex angles than the a-frame, to give a more rounded, cockpit-like look from the inside. The projector will be mounted on top of the main frame towards the rear of the shell, on an assembly which will take it up to about 2.6m above floor level, which will let it project on a down-angle to the wall opposite, where a first-surface mirror will be mounted that will direct the image onto back-projection screens mounted in front of the front windows. But these are subjects for future posts.
Tomorrow, taking advantage of the Bank Holiday Monday, I will attempt to finish the remaining pillars and put in the intial framing for the windows. More pictures then, hopefully…
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