Hi Guys,

A bit of progress today... The first stage of installing the smoke system was to re-rout the exhaust through the side of the fuz and out of the bottom, this involved taking out the tank (which took about 2 hours to fit nicely in the first place!) and cutting a couple of holes, for the silicon exhaust tube. I have protected the tube from the relatively sharp edges of the fuselage with cable glands (bottom one not shown).
Before I committed to cutting holes in the lovely fuselage I did some engine tests with different exhaust configurations to see the effect of the long exhaust tube on RPM, I decided if there was a significant drop in power I would abandon the project as I do not want to slow her down too much! The engine is an ASP .61 with a 'super quiet exhaust' the exhaust has a removable centre section and a baffle which can be removed or moved between the front and rear of the centre section, this gives a few possible configurations which all have effects on power vs noise. I was hoping that if I removed the baffle and the centre section I would get more power and the silicon pipe would enter the fuz towards the rear well out of the way of the fuel tank and the rear ply former. Anyway I did the engine tests and was surprised and ultimately pleased with the results...

I let the engine cool between each test and used the same APC 11X7 prop.

1) Original tried and tested configuration:
centre section in place, baffle fitted at the front of the centre section (closest to the cylinder), standard short exhaust deflector fitted....12,720 RPM

2) As above but with 300mm blue silicon tube fitted in place of the standard exhaust deflector....13,260 RPM (!)

3) Centre section in place but baffle removed, 300mm blue silicon tube fitted.... 13,530 RPM

4) Centre section in place now with the baffle fitted at the rear of the centre section (farthest from the cylinder), 300mm blue silicon tube fitted.... 13,700RPM

5) Centre section removed baffle fitted (shot exhaust configuration), 300mm blue silicon tube fitted (this setup was MUCH louder).... 13,000-13,200 RPM

I decided at this stage to run with option 4! I was getting close to a 1,000 RPM increase from my original configuration and the engine was quieter too....must admit I was not expecting that!!
it did mean however that as the exhaust wasn’t going to end up any shorter the silicon exhaust tube would clash with the fuel tank where it entered the side of the fuz resulting in an internal re-shuffle!