Sonex B Model 019
Posted: Wed Apr 06, 2022 1:37 pmI flew my Sonex B Model for the first time on 11th March 2022. Subsequent flights have opened up the flight envelop but I have yet to perform quantitative measurements of performance. However, initial impressions are all favorable.
Power is from a ULPower 350i (118hp at 3300rpm) driving a Sensenich, ground adjustable, 2 bladed prop.
The left wing is marginally heavier than the right. Is this due to no passenger? I’ve tried leaning to the right side of the airplane but it was inconclusive. I installed a conventional pitch trim tab which works OK, but it will not hold the nose up with full flap, so I intend to make a bigger tab.
In cruise I have to hold a little right rudder, so I made the rudder return spring a tiny bit shorter. I’ve flown like this once, but it was too bumpy to really assess any improvement.
Some of my other modifications:
I designed a swing back canopy; opening is assisted by 2 gas struts and once the back is lifted a couple of inches the canopy opens on its own…cool (well I think so). Taxing with the canopy open is a breeze!
The Sonex fuel tank was replaced with an aluminum tank because the Sonex tank buckled and I did not think that the initial Sonex solution would work. Their second and third solutions sound OK, but before they were issued I had committed to an aluminum tank. The main benefit is that I made the filler cap fit flush on the external fuselage skin.
The inlets on the B Model universal cowl do not align with the cylinder heads of the ULPower engine, so I moved the inlets outboard and upward. I also reduced the area to that recommended by ULPower. The Sonex side outlets are installed per drawing, but I increased the exit area with the installation of a pair of louvers (about 3.5 by 7 inches each, the pair were $12 from Amazon). They are mounted on the bottom, rear surface of the lower cowl. CHT and OilT climb quite rapidly on the ground, and a hundred degree F difference develops in the CHTs during high power ground runs. However, once airborne the CHTs quickly even out and everything so far has been nicely in the green.
Rate of climb at 100 mph is about 1000 fpm and IAS at 8000 ft is over 150 mph at 2800 rpm, but again, I have not performed PE measurements, and these numbers are probably optimistic.
Handling is pleasant, pitch sensitivity seems great---light and responsive. Roll sensitivity is not as good (my opinion), the roll stick forces are heavier and the roll rate is not as fast as I expected. That is not to say it is heavy or slow in roll, just not as light/responsive as the pitch control.
Initial flights utilized a single center stick. It was comfortable but I found it awkward to write on my knee pad when holding the center stick with my left hand. Today I flew with a Y stick (not the Sonex supplied one, their angles are all wrong), it too seems comfortable and I found it easier to fly with the left hand.
Duncan
Power is from a ULPower 350i (118hp at 3300rpm) driving a Sensenich, ground adjustable, 2 bladed prop.
The left wing is marginally heavier than the right. Is this due to no passenger? I’ve tried leaning to the right side of the airplane but it was inconclusive. I installed a conventional pitch trim tab which works OK, but it will not hold the nose up with full flap, so I intend to make a bigger tab.
In cruise I have to hold a little right rudder, so I made the rudder return spring a tiny bit shorter. I’ve flown like this once, but it was too bumpy to really assess any improvement.
Some of my other modifications:
I designed a swing back canopy; opening is assisted by 2 gas struts and once the back is lifted a couple of inches the canopy opens on its own…cool (well I think so). Taxing with the canopy open is a breeze!
The Sonex fuel tank was replaced with an aluminum tank because the Sonex tank buckled and I did not think that the initial Sonex solution would work. Their second and third solutions sound OK, but before they were issued I had committed to an aluminum tank. The main benefit is that I made the filler cap fit flush on the external fuselage skin.
The inlets on the B Model universal cowl do not align with the cylinder heads of the ULPower engine, so I moved the inlets outboard and upward. I also reduced the area to that recommended by ULPower. The Sonex side outlets are installed per drawing, but I increased the exit area with the installation of a pair of louvers (about 3.5 by 7 inches each, the pair were $12 from Amazon). They are mounted on the bottom, rear surface of the lower cowl. CHT and OilT climb quite rapidly on the ground, and a hundred degree F difference develops in the CHTs during high power ground runs. However, once airborne the CHTs quickly even out and everything so far has been nicely in the green.
Rate of climb at 100 mph is about 1000 fpm and IAS at 8000 ft is over 150 mph at 2800 rpm, but again, I have not performed PE measurements, and these numbers are probably optimistic.
Handling is pleasant, pitch sensitivity seems great---light and responsive. Roll sensitivity is not as good (my opinion), the roll stick forces are heavier and the roll rate is not as fast as I expected. That is not to say it is heavy or slow in roll, just not as light/responsive as the pitch control.
Initial flights utilized a single center stick. It was comfortable but I found it awkward to write on my knee pad when holding the center stick with my left hand. Today I flew with a Y stick (not the Sonex supplied one, their angles are all wrong), it too seems comfortable and I found it easier to fly with the left hand.
Duncan