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Published on 08 October 2012

 2-Stroke Props | 4-Stroke Props | Engine Size Chart | Aircraft Trimming

Metric to Inches | Wing Loading| Color

Engine Size Starting Size Other Sizes to try
.049 6-3 5.25-4, 5.5-4, 6-3.5, 6-4, 7-3
 

 

 

 

 

 

2-Stroke Engine Prop Sizes>
Engine Size
(cu.in)
Starting SizeOther Sizes To Try
.049 6-3 5.25-4, 5.5-4, 6-3.5, 6-4, 7-3
.09 7-4 7-3, 7-4.5, 7-5
.15 8-4 8-5, 8-6, 9-4
.19 -.25 9-4 8-5, 8-6, 9-4
.29 -.30 9-6 9-7, 9.5-6, 10-6
.35 -.36 10-6 9-7, 10-5, 11-4
.40 10-6 9-8, 11-5
.45 10-7 10-6, 11-5, 11-6, 12-4
.50 11-6 10-8, 11-7, 12-4, 12-5
.60 -.61 11-7 11-7.5, 11-7.75, 11-8, 12-6
.70 12-6 11-8, 12-8, 13-6, 14-4
.78 -.80 13-6 12-8, 14-4, 14-5
.90 -.91 14-6 13-8, 15-6, 16-5
1.08 16-6 15-8, 18-5
1.2 16-8 16-10, 18-5, 18-6
1.5 18-6 18-8, 20-6
1.8 18-8 18-10, 20-6, 20-8, 22-6
2.0 20-8 18-10, 20-6, 20-10, 22-6
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4-Stroke Engine Prop Sizes
Engine Size
(cu.in)
Starting SizeOther Sizes To Try
.20 -.21 9-6 9-5, 10-5
.40 11-6 10-6, 10-7, 11-4, 11-5,
11-7, 11-7.5, 12-4, 12-5
.45 -.48 11-6 10-6, 10-7, 10-8, 11-7,
11-7.5, 12-4, 12-5, 12-6
.60 -.65 12-6 11-7.5, 11-7.75, 11-8, 12-8,
13-5, 13-6, 14-5, 14-6
.80 13-6 12-8, 13-8, 14-4, 14-6
.90 14-6 13-6, 14-8, 15-6, 16-6
1.20 16-6 14-8, 15-6, 15-8, 16-8,
17-6, 18-5,18-6
1.60 18-6 15-6, 15-8, 16-8,
18-6, 18-8, 20-6
2.40 18-10 18-12, 20-8, 20-10
2.70 20-8 18-10, 18-12, 20-10
3.00 20-10 18-12, 20-10
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Engine Size Conversion Chart (ci=cc)
Cubic InchesCubic Centimeters
.049 .8
.09 1.5
.15 2.5
.19 3.1
.21 3.5
.25 4.1
.29 4.8
.35 5.7
.40 6.5
.46 7.5
.50 8.2
.61 10.0
.80 13.0
.91 14.9
1.20 20.0
1.50 25.0
1.60 26.2
1.80 30.0
2.00 32.8
2.40 39.3
2.70 44.3
3.00 49.2
1Cubic Inch = 16.3934 Cubic Centimeters
.061 Cubic Inch = 1 Cubic Centimeter
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Aircraft Trimming Chart for aerobatic flight
To test for:Test procedure:Observations:Adjustments:
Control Neutrals Fly model straight & level Use transmitter trims to achieve hands-off straight & level flight Adjust devises to center transmitter trims
Control Throws While flying apply full deflection of each control Check response rate for each control Aileron High: 3 rolls in 4 seconds
Aileron Low: 3 rolls in 6 seconds
Elevator High: Allows smooth square corners
Elevator Low: 130' diameter loop
Rudder High: 30-35 degrees for stall turns
Elevator Low: Just enough to maintain knife edge flight
Incidence Power off vertical dive, cross wind. Release controls when aircraft is vertical A. Model continues straight down
B. Model starts to pull out
C. Model goes nose down
A. No adjustments
B. Reduce incidence
C. Increase incidence
Center of Gravity
(method 1)
Roll model inverted A. Lots of down elevator required to maintain level flight
B. No down elevator required
A. Add tail weight
B. Add nose weight
Center of Gravity
(method 2)
Roll into near vertically banked turn A. Nose drops
B. Tail drops
A. Add weight to tail
B. Add weight to nose
Tip Weight (course adjustment) Fly model straight & level upright. Check aileron trim, maintain wing level. Roll model inverted, wings level. Release aileron stick. A. Model does not drop a wing.
B. Left wing drops
C. Right wing drops
A. No adjustment needed
B. Add weight to right tip
C. Add weight to left tip
Side Thrust Fly model away from you into any wind. Pull into vertical climb watching as model slows down A. Model continues straight up
B. Model veers left
C. Model veers right
A. No adjustments needed
B. Add weight to right tip
C. Add weight to left tip
Up/Down Thrust Fly model away from you into wind. Pull into vertical climb and release elevator. A. Model continues straight up
B. Model pulls up
C. Model pulls down
A. No adjustment needed
B. Add down thrust
C. Reduce down thrust
Tip Weight Fly model away from you into wind, pull into small diameter loop A. Model comes out wings level
B. Right wing low
C. Left wing low
A. No adjustment needed
B. Add weight to left tip
C. Add weight to right tip or remove from left tip
Aileron Differential Fly model on normal pass and do 3 rolls A. Roll axis on model centerline
B. Roll axis off to the side as roll command
C. Roll axis off to opposite side of roll command
A. Differential Okay
B. Increase differential
C. Decrease differential
Dihedral Fly model on normal pass, roll into knife edge flight. Maintain with top rudder. (Test on both right and left side) A. Model does not roll out of knife edge
B. Model rolls in direction of applied rudder
C. Model rolls opposite the rudder in both tests
A. Dihedral Okay
B. Reduce dihedral
C. Increase dihedral
Elevator Alignment
(models with split elevators)
Fly model straight into wind. Pull into inside loop. Roll inverted and push into outside loop A. No rolling when elevator applied
B. Model rolls in same direction in both tests
C. Model rolls in opposite directions in both tests
A. Elevators correctly aligned
B. Elevator misaligned. raise or lower one half
C. One elevator half has more throw than the other. (Model will roll to the side with the most throw) Reduce the throw on one side, or increase on the other side
Pitching in Knife Edge Flight Same as dihedral test A. No pitch up or down
B. Model pitches up
C. Model pitches down
A. No adjustment needed
B. Alternate cures;
1. Move the CG back.
2. Increase the wing incidence.
3. Drop the ailerons
C. Reverse the above.
Although these steps will work on any aircraft, they are for experienced pilots to trim aerobatic aircraft. If you are uncomfortable with any of these manuevers, get help. Trimming must be done in calm conditions. Make multiple tests before making adjustments. Trimming chart courtesy of Russell Knetzger of Milwaukee, Wisconsin.
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Metric Conversions to Inches
Metric (MM)American (Inches)
1.0 1/32
1.5 1/16
2.5 3/32
3.0 1/8
5.0 3/16
6.0 1/4
8.0 5/16
9.5 3/8
13.0 1/2
25.4 1"
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Calculating Wing Loading
Wing loading is the key factor for good aerobatic performance! As a guideline, a Sports Aerobatic wing loading of 19 to 25 ounces per square foot would be ideal.
To calculate wing loading:
bullet Convert weight from pounds to ounces.
bullet Weight of model 5 lb. X 16 oz/lb. = 80 Ounces
bullet Wing Area in square inches.
bullet 600 sq. in. divided by 144 (sq. ft.) = 4.16 sq.ft.
bullet Divide ounces by square feet.
bullet 80 oz divided by 4.16 (sq.ft.) = 19.23 oz per square foot.

Color

While we’re in our winter building cycles, we will soon be faced with the age-old question about “What color should our new creation be?” If this is a scale representation of a full-scale airplane, then the color scheme is predetermined. If we are young and eagle-eyed, then the color is chosen more on the basis of aesthetics rather than visibility. However, if our eyes aren’t quite as good as they used to be, then the color needs to be such that we can see it better. If you can’t see it, then you can’t control it. The following chart shows the visibility index for a variety of colors;

 

Luminous Orange

100 percent
White 90 percent
Light Yellow 80 percent
Light Orange 75 percent
Dark Yellow 70 percent
Light Grey 66 percent
Light Blue 60 percent
Light Red 58 percent
Light Brown 55 percent
Light Green 51 percent
Dark Grey 51 percent
Dark Red 50 percent
Dark Blue 50 percent
Dark Brown 50 percent
Black 50 percent

What does all this mean to modelers? It says that International (luminous) Orange is the most visible under most light conditions, and that most dark colors are only about half as visible as luminous orange.

While contemplating what colors to put on that new model, consider the following

  • Avoid single-color aircraft. particularly solid silver or solid dark colors.
  • Beginners are advised to color the bottoms of aircraft wings a dark color and the tops a light color.
  • Orientation recognition can be enhanced by placing large dark circles under the wings and a starburst pattern of straight lines on the top.
  • Any series of adjacent colors on your aircraft that is intended to facilitate orientation should be gray-scale opposites—not color opposites.
  • Don’t rely on intricate patterns; they tend to blend together to form an edgeless fuzz at approximately 100 feet away.
  • A bright red or orange leading edge on your wing and horizontal will help you keep your wings level during landings.
  • Color lines parallel to and above the fuselage horizontal thrustline provide a good angular reference on the glide path prior to the final turn.
  • For better loops, make the wingtips and horizontal stabilizer red or orange, and the body background a very light color such as white or yellow. This helps you tell if the wings are flat.

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