Posts: 4380
Joined: 5/24/2003 From: Rochester,
NY, USA Status: offline
My finished Skylark needed only the decals added. After the photos were taken, I easily applied the pre-cut, sticky-back decals to the wing, fuselage, and dash.
Here are some scenarios for battery power on the Skylark. For reference, the stock glow powered plane is RTF at 86oz (5.4 lbs).
Scenario 1
16-cells of CP2400 weigh 35.5oz (2.2 lbs). This makes the plane balance at 210mm from the trailing edge instead of the recommended 170mm. It is severely noseheavy. To balance the plane, you need 3oz added to the rudder. This makes the plane Ready-To-Fly (RTF) at 107oz (6.7 lbs). The power system with the APC 14x7 e-prop delivers 105 w/lb drawing a measured 46amps (700w).
The advantage here is longer flights at the cost of higher wingloading and hotter landings.
Scenario 2
16-cells of CP1700 weigh 27oz (1.7lbs). This makes the plane almost properly balanced...very slightly noseheavy. I suspect a very small weight (0.5oz) added to the rudder will balance the plane but I will fly the maiden voyage without it using CP1700 cells. This makes the plane RTF at 96oz (6.0 lbs). The power system provides 117 w/lb.
The advantage here is lighter wingloading but shorter flights. Alternatively, 1950FAUP cells would provide slightly longer flights and likely balance the plane perfectly.
Scenario 3
Once again, Lithium comes to the rescue. By using a 4s3p configuration of Kokam 1500HC cells, the entire pack weighs only 16oz yet almost triples (2.6 times) the duration over the CP1700 cells at 4500mAh. The packs can be moved forward in the fuselage to balance the plane. The plane is RTF at 85oz (5.3 lbs) which is equal to the glow powered flying weight. The power system provides 132 w/lb.
The advantage here is a light flying weight and long flights. The disadvantage is higher cost.
Summary
I will test fly my Skylark using 16-cells of CP1700 and report on its performance. I will likely switch to Lithium cells in the future to provide longer, lighter flights. The nice part about electric power systems is that you can upgrade portions at a time.
Posts: 4380
Joined: 5/24/2003 From: Rochester,
NY, USA Status: offline
We flew the maiden voyage of the Skylark today and it was a perfect flight!
On take-off, the plane climbed out at a steep angle and flew like a true pattern ship without any trim changes.
As expected, the Skylark looked great in the air and was easy to track. At only half throttle, the plane moves along nicely. The Skylark landed like a dream after we performed many aerobatic stunts. We did not attempt to knife edge it for very long due to the heavy cross winds but the sleek, trim design performed very well when we did.
This plane had my flying team very excited and we look forward to our next voyage when the weather permits. I'll post some flying photos later this week.
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Joined: 5/24/2003 From: Rochester,
NY, USA Status: offline
Our pre-flight check on the Skylark revealed that when applying down pressure to the elevator, the control rod would bend a bit. This may produce a mushy feel on the elevator during certain maneuvers.
I cut a popsickle stick to proper length and then cut a slot in the side to keep the metal rod from bending to the inside of the fuselage when the servo is pushing the elevator. The wooden stick was epoxied in place.
I tested the elevator under some holding pressure from my hand and it works great!
Posts: 4380
Joined: 5/24/2003 From: Rochester,
NY, USA Status: offline
I have a real passion for pattern planes. Perhaps it is because they make my flying look better. A true pattern ship almost flies itself and the Skylark did not disapoint!
The power of the AXI 4120 in this ship really surprised us on takeoff!
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Joined: 6/20/2002 From: rowlett,
TX, USA Status: offline
Nice looking bird Greg;
How would you rate its flying characteristics to your Razor?
I am using the AXI in another plane and am curious about the advertised power vs what it actually can do. The plane will be aroun 7# on 12 cells. Is this the motor you will stick with in this pattern plane or are you looking for more power?
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Joined: 5/24/2003 From: Rochester,
NY, USA Status: offline
Hi Kirby,
You ask some good questions that I cannot fully answer until I've had more stick time on both planes. The flying season will start here in a few more months and I can't wait to fly the heck out of both planes!
I can make a few generalizations though. In most cases, size is better. A .60-size beats a .40-size beats a .30-size and so on.
The Skylark is a true .40-size, pattern flyer and the Razor 3D is a .30-size, cross-functional pattern/3D flyer. Both planes look great and fly great!
The AXI 4120 had plenty of power to fly the Skylark. It will only get better when I replace them with the new Kokam 2AH (16C) cells to triple my flight duration.
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Joined: 5/24/2003 From: Rochester,
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My 16-cell CP1700 pack on the AXI 4120 power system with the APC 14x7 e-prop measured 46amps. I expect the 4s Kokam setup to be close because the voltage drop is much less and on my Monocoupe, which also has a 4120/14, the 4s5p Kokam 1500 pack was stronger in RPMs than the 14-cell 2600mAh FAUP NiMH pack that it replaced.
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Joined: 5/24/2003 From: Rochester,
NY, USA Status: offline
Kirby,
Keep in mind that the cell types were different. The 14-cell pack was higher current delivery 2600mAh FAUP NiMH cells and the 16-cell pack was only CP1700 or CP2400 NiCd cells. The FAUP NiMH cells hold their voltage better under a 40+ amp load.
Additionally, cell age plays a part. You always want to make your own measurements as a sanity check. The main goal here is a ballpark figure since you get about 10-15% unloading in the air and throttle maintenance can provide additional performance when used by a skilled pilot.
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RE: Hobby Lobby Skylark e-Conversion - 
