Pics of N577MD

[MarkD 53]

So I said I would post some pictures of my just recently re-acquired Model C.  Here ya go:

The first is how I found it after 10 years, then some wing damage repair, then some beauty shots.

 

[C5Engineer 1170]

Can you post some closer shots of your muffler and cooler system??

[Av8r3400 1179]

503 power?

[MarkD 53]

Engine is a Hirth 2706-2C with free air heads and self made ducting. Saved nearly 20lbs by going Free-Air. Not absolutely sure it was the best idea but at the time I was determined to make an Avid that weighed less than 500lbs. The pay off is absolutely outstanding performance but the sacrifice is very critical tuning in jetting and prop pitch adjustments. I may have to change jetting and prop pitch multiple times as daytime temps change to control EGTs as optimal as possible. I get better than 1000FPM climbs and cruise at 85-90MPH indicated. Fuel burn is fairly steady around 5gph. Take offs are usually around 100ft and stalls are typically around 40mph or under with no flaps deployed. Fun airplane to fly and very capable in off airport applications. If I had to do it all over again I would probably keep the fan cooling or go with the 582 with oil injection. I had some mechanical problems with the Hirth initially but I hope that is all behind me now. The learning curve was very painful.

[MarkD 53]

The ducting I made was part of the steep, painful learning curve previously mentioned. The lower ducting shown in the front view picture is the ducting to the Free-Air heads. Larger outlet than inlet and uses cowl pressure to draw the air across the heads. The port side duct (upper duct inlet) shown in the front view picture is cooling duct to the exhaust side of the cylinder above the heads and below the exhaust port (inverted engine). This duct provides additional direct cooling to the exhaust side of the cylinders. Again, this is a result of long term pain on the learning curve. The typical operating temps are 350-400deg F CHT and 1100-1200deg F EGT. 500CHT and 1250EGT are absolute max allowed. I fly the EGT most of the time. RPM values are: 6800 red line, Try to prop the engine for 5500 static, cruise around 4800 to 5000 depending on EGT with a burn rate of 5gph. The electronic ignition has built in non-adjustable 7000rpm limiter.

[EDMO 1078]

Sounds like a 503 Bandit 480 ew would have been a lot simpler - This is from a NON-2 stroker!  "lol"

Nice looking plane...

EDMO

Edited 10 Jun 2015 by Ed In Missouri

[MarkD 53]

Sounds like a 503 Bandit 480 ew would have been a lot simpler - This is from a NON-2 stroker!  "lol"

Nice looking plane...

EDMO

You may be correct but at the time (1998) I found this kit and became the third owner of the partial uncompleted kit.  I had to scrounge many missing parts and make others.  Some stuff I purchased from Airdale when they were still in business.  A local flying buddy had a MK-IV that suffered an engine failure resulting in extensive damage to the fuselage so I was able to "CASREP" parts and structure from the salvage.  That is where the wheels, brakes, rudder pedals, engine mount and various additional tubing and fittings came from.  It was a real build project.

 

Thanks for the compliment, I'm actually quite proud of the plane because it represents better than two years of a challenging and difficult build. 

[saskavid 47]

Engine is a Hirth 2706-2C with free air heads and self made ducting. Saved nearly 20lbs by going Free-Air. Not absolutely sure it was the best idea but at the time I was determined to make an Avid that weighed less than 500lbs. The pay off is absolutely outstanding performance but the sacrifice is very critical tuning in jetting and prop pitch adjustments. I may have to change jetting and prop pitch multiple times as daytime temps change to control EGTs as optimal as possible. I get better than 1000FPM climbs and cruise at 85-90MPH indicated. Fuel burn is fairly steady around 5gph. Take offs are usually around 100ft and stalls are typically around 40mph or under with no flaps deployed. Fun airplane to fly and very capable in off airport applications. If I had to do it all over again I would probably keep the fan cooling or go with the 582 with oil injection. I had some mechanical problems with the Hirth initially but I hope that is all behind me now. The learning curve was very painful.

so what make of carbs does the hirth use? In terms of controlling mixture /egt you may want ot look into a hacman to help with managing your fuel to air ratio. The bing 54's on the 582 are what the hac is set up to work with but can be adapted to others most likely with some finingering. Joey has a thread dealing with the installation on a 582 posted here.

[TJay 1041]

A lot of people don't trust Hirth because of all the problems they had but in my opinion I still think the technology on them are miles ahead of Rotax, the two cycles at least.

[MarkD 53]

C5Engineer asked for some pics of the cooling shrouds and the muffler mount,  I included some of the cowl mods I made also.  I first glassed the cowl together then split it horizontally.  Then sectioned off the boot cowl and made the front top into halves.  All is attached with Cam-Lock fasteners.  Makes it easy to get into the engine house for a pre-flight inspection.

 

 

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