The final bit of work was to cut and weld some 45 degree down-turns at the aft end of each pipe where the exhaust exits the bottom of the engine cowl. The down-turns at the aft end of the pipes are designed to direct the exhaust down and away from the bottom of the fuselage. There is a trade off between using long turn down tubes, which do a better job of directing the exhaust away from the bottom of the fuselage but create more drag, and using shorter tubes which create less drag but if too short will allow the bottom of your fuselage to get black.
I started with a couple of 90 degree elbows and cut them exactly in half:
All of the exhaust pipes were then cut to be the same exact distance from
the firewall (about 1 1/2"). The elbows were then positioned on the
exhaust pipe to point downward and were tack welded:
After tack welding they were checked for fit and that they were all even
and parallel with each other. After a little trimming here and there,
they were final welded. Here is one of the complete exhaust pipes
at this point:
The cabin heat muff will be eventually mounted within the long straight area
away from any welds.
Here is the bottom cowl outlet with all four exhaust pipes exiting the bottom
cowl:
|Like I said, it took a little trimming and re-positioning to get them all
nice and even but it looks good now. I like the nice, smooth rounded
flow of these pipes. They are totally unrestricted and should help
the engine produce some good horsepower.
The exhaust pipes were all removed and sanded, wire brushed and de-greased,
in preparation for paint. They were hung from the rafters with some
wire and some high temp black paint was applied. Here are three of
the four all painted and drying:
That's it for the exhaust. After drying for a couple of days, these
were mounted to the engine using the "blow proof" gaskets, lock washers and
nuts. Note, the high heat paint is still a bit soft until the engine
is run for the first time and the heat up.
Exhaust System
Completed: July 27, 2007
Total Time: 26 hours