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Posted by cloud-9 | Jul 10, 2008 @ 02:05 PM | 12,587 Views
Why flaperons increase the tendency to tip stalling. Comments and corrections most welcome.

Full length flaperons:

The angle of attack at the root is usually greater than at the tip, thanks to washout, even when flying level. Thus, in level flight, stall starts at the (trailing edge of the) wing root. When banked and turning, the inside wing tip travels slower than the root, the outside wingtip travels faster than the root. The inside wingtip generates less lift, since it is traveling slower. So when turning, there is a tendency for the inside wing to drop, and a tendency for the outside tip to lift, relative to flying level. This can lead to tip stall.

When flaperons are dropped, the overall angle of attack is increased, and stall tendency is increased (stall speed is decreased). The whole wing is more likely to stall. This magnifies effects of turning on lift and stall behavior of the wings tips and tip stall likelihood is increased.

Flaperons on outer wing:

When the flaperons are only on the outer part of the wing, the angle of attack of the outer part of the wing is increased (stall speed decreased) but the inner part of the wing is unaffected. Thus, when turning, the effect of this difference in stall characteristics of the inner and outer wing are added to the above-described effects, and tip stall probability is increased further.

The larger the aileron, the greater the impact on angle of attack and resulting tip stall influences, and the greater the aspect ratio of the wing (length to chord), the greater the difference in flight characteristics between the center and tip of the wing, so the greater these tip stall tendencies will be. So, for example, flaperon effects on tip stall should be bad on a Super Cub with barndoor ailerons on the outer parts of the wings only. However, it could be worse, since tapered wings have more tip stall characteristics than non-tapered wings as on the Super Cub.
Posted by cloud-9 | Jun 24, 2008 @ 02:20 PM | 12,374 Views
Graph of zip charging A123 cells, using Dan Baldwin's Terminator II. At the right, voltage reaches cutoff level, connection is terminated (presumable causing voltage spike), amperage drops, final voltage at full charge.
Posted by cloud-9 | Jun 11, 2008 @ 01:43 AM | 12,287 Views

These guys usually fly 2-meter wingspan composite (carbon fiber and fiberglass sandwiched with balsa, aluminum, etc.) planes with gas engines costing thousands of dollars. Lithuanian RC pilot Donatas Pauzuolis won the competition with this $200 Extreme Flight Vanquish, 50" wingspan, with a little electric motor.

What grace.
Posted by cloud-9 | Jun 08, 2008 @ 05:40 PM | 14,606 Views
A diagram of how CCCV charging works. If anybody knows of a diagram of CCCV discharging, would be happy to add it.

Posted by cloud-9 | Jun 05, 2008 @ 12:52 PM | 12,804 Views
Testing by NoFlyZone (Chuck):

Stock SC motor and stock 10x8 prop:
Using a stock 7 cell NiMh through my wattmeter, on the stock 10x8 prop
1/2 throttle... 3150 rpm... 8.1v... 4.5 amps... 36 watts
Full throttle... 3750 rpm... 6.9v... 7.9 amps... 54 watts

Stock motor with 3S lipo and 10x6 prop:
Using a ThunderPower 3s 1320mAH Li-Po:
Castle Creations Pixie 20P ESC
GWS 10x6 DD prop

Full throttle = 6700 rpm
Volts = 10.9
Amps = 8.4
Watts = 91.3

Slow cruising speed is 4 clicks under half throttle = 3750 rpm
Volts = 10.5 (This was at the end of the flight)
Amps = 2.1
Watts = 22


Here are some numbers posted using a largish brushless by Bill B.:
Motor BL 480
Battery- 1250 3cell lipo
prop- TF 10x6 wood
1/2 throttle- 8230 rpm-3.9 amps-38.4 watts
full throttle- 9345 rpm-16.3 amps-153 watts
Bill B
Posted by cloud-9 | Jun 02, 2008 @ 06:01 AM | 12,295 Views
From Everydayflier:

4.2 100%
4.1 90%
4.0 80%
3.9 70%
3.8 60%
3.7 50%
3.6 40%
3.5 30%
3.4 20%
3.3 10%
3.2 0%

From NoFlyZone's blog:

It also seems that we will maximize our Li-Po life by taking them down to no lower than 20% of their capacity. Here is the latest and greatest information I have managed to gather from extensive reading on this subject.
"Resting" Voltage per cell
4.20v = 100% of our battery's amp capacity remains.
4.03v = 76% of our battery's amp capacity remains.
3.86v = 52% of our battery's amp capacity remains. (A good voltage to store our Li-Pos at)
3.83v = 42% of our battery's amp capacity remains.
3.79v = 30% of our battery's capacity remains.
3.75v = 20% of our battery's amp capacity remains. (Where we want to take our Li-Pos to for long life)
3.70v = 11% of our battery's amp capacity remains. (Detrimental 'battery voltage dump' begins)
3.6?v = 0%
In line with the above, we do NOT want our Li-Po's resting voltage to be less than 3.75v per cell, which would mean we had used about 80% of their capacity.

Store them at about 3.85 volts per cell (about 50%)
Fully charged: 4.20v/cell x 3S = 12.6 volts
Storage voltage: 3.85v/cell x 3S = 11.55 volts
20% left: 3.75v/cell x 3S = 11.25 volts
Posted by cloud-9 | Jun 01, 2008 @ 04:27 PM | 13,188 Views
Here is my power system testing station. I will be using it with a Medusa Power Analyzer Pro, and the scale on the test stand is the Medusa Thrust Meter so I will be able to plot thrust along with power measurements. When testing the stand will be aligned with the front edge of the table top and secured with a C-clamp to the table, and a cage (pics when completed) will be placed around the spinning prop.

The test stand was very generously built for me by Dr. Kiwi, who is well known in RCGroups for his extensive and trustworthy motor testing. He has built a small number of these stands for himself and others, perfecting them along the way. I am very proud to own this beautifully grained wood and brass work of art. It will be a foundation for very much enjoyable and educational research on electric motors. You can see the thread on construction of his stands here:
Toward the end of the thread the construction of this actual stand is depicted.

The power supply is a Mastech 3010E-3, which will allow testing motors with variable voltage supplied. It has two independent 30volt, 10amp variable voltage and variable amperage power supplies, so that it can be run at continuous controlled voltage or continuous controlled amperage. The two power supplies can be linked in parallel or series, producing 30 volts/20 amps, or 60 volts/10 amps. In addition, there is a third power supply that supplies a constant 5v. All three power supplies can be used simultaneously to charge batteries, as long as the PS limits are observed. I'll run an extension to the nearby window and charge lipos in a steel bucket outside. It's light and can be taken to the field to charge batteries either through a charger, or directly with A123 packs, from either a deep cycle battery (or batteries) and inverter, or a generator/inverter combo like a Honda EU1000i.
Posted by cloud-9 | Mar 23, 2008 @ 11:25 AM | 12,761 Views
About my third Cub. Strapping tape on leading edge of wing and along fuselage, reinforced wing edges at saddle, 3S1P 2150 lipo battery and GWS 10x6, and added Great Planes Dural landing gear. This plane took a dive into the cement roof of a gym, pulling up at the last second before impact, which flattened the gear but the plane was fine. It eventually succumbed to the death of a thousand crashes though.

I got sick of straightening the wire gear so went to great lengths to design and make a solid mount for this gear. The gear and the aluminum mount for it that is CA'd into the fuse weighed over 40 grams causing the plane to fly pretty heavy, so I've abandoned it for the stock wire gear on the next cub which is still flying and getting the brushless above.

The pics were taken at sunup. The last pic shows my close to home and work flying field, soccer fields on campus.
Posted by cloud-9 | Mar 22, 2008 @ 02:26 PM | 30,731 Views
Here is the brushless motor and mount for my Super Cub brushless upgrade. This is modeled after Chuck's (NoFlyZone) mod here:

The stock black motor/gearbox housing was used as a base, to retain correct thrust angle. A Dremel was used to remove the shaft housing and motor mounting sections. Two sheets of 1/16 basswood were CA'd together with grain at right angles, and painted yellow with artist's acrylic and brush, to form a mounting plate for spacers, X-mount, and motor.

I'm using a larger diameter motor and thus a larger X mount, and the bottom mount bolts were more widely spaced and intersected the walls of the mount, so I cut that area of wall away. This made the mount weaker and prevented these two bolts from holding the housing and yellow mount plate together as with Chucks, so I CA'd the mount plate to the housing. It's essentially one solid piece now.

The entire assembly is 16 grams lighter than the stock assembly (the third pic shows the two systems as weighed side by side). The motor is this one:
and I am using the X motor mount and the prop mount shown there.

The aluminum spacers are 3/4" long, with 4-40 cap screws. These were selected to put the propeller position in the same place as the stock setup. I ground a corner off the two top nuts in the back to clear the housing.

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