The 450Logbook

 

Installing a Beech Staggerwing Exhaust on the 450 Stearman

More text coming as the project nears completion.

I built the airplane with a Broussard (French version of a Beaver) exhaust which had twin exits at roughly 4:00 and 8:00 positions. I constructed fairings on each side to smooth airflow over the outlets. I felt this was a better option than the usual single outlet, modified BT-13 exhaust, or modified Beech 18 exhaust. It was also a.) available, and b.) not too expensive. Two desireable traits in building a 450 Stearman.

Further complicating the exhaust installation was the choice to use a Beech 18 cowling and intake. This required considerable engineering to make the Broussard carburetor heat system work with the Beech 18 intake system. There were also space considerations where the Beech 18 intake had to be modified to allow space for the Broussard exhaust.

If Beech 17 (Staggerwing) exhaust systems were plentiful, I would have used this from the beginning. But, they're not. I should also note that the Broussard system actually worked quite well. It performed well in all regards, and was less obtrusive than the BT-13 type.

The expected advantages of the Staggerwing system would be:

    1. No need to modify the Beech intake system for space considerations.
    2. Compatibility between the Beech 18 and Staggerwing carburetor heat system.
    3. No extensive fairing for the exhaust outlets.
    4. Exhaust outlets that don't blow against the gear legs.
    5. Neater look, and less obtrusive with the Beech 18 cowling.

The disadvantages:

    1. Need to get another field approval.
    2. Need to patch the Broussard outlets.
    3. Cost of the Staggerwing exhaust and heat muffs.
    4. Need to fabricate the interface between the Beech 18 intake and the Staggerwing heat muffs.
    5. Downtime required for fabrication and repaint.

After finding a source for the Staggerwing exhaust, I decided to move ahead on the project hoping to finish before spring of 2008. I now expect to finish before Summer of 2008.

Some of the problems that came up that needed to be solved: