RCU Forums - View Single Post - Flight controls efforts simulation for the FEJ F-18F

06-07-2009 | 07:28 PM

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olnico

Joined: May 2007

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From: Houston, Texas.

Flight controls efforts simulation for the FEJ F-18F

Hello guys,

I have made a simulation on flight controls setup with Craig's woksheet.

Some specific points:

I have entered a max speed of 200 mph ( 100 mph for the flaps ).
All control surfaces dimensions have been meticulously measured.
The elevator surface have been computed as followed. The surface forward of the control axis has been substracted from the surface aft of the axis.

The results:

Optimized aileron setup:

Note that the optimum servo arm length is 0.9 cm. The maximum torque required at 20 degress of aileron deflection is 97 oz/in

I have simulated a non optimized setup that reqires 220 oz/in at 20 degrees of deflection ( JR8611 ).

A servo arm length of 1,4 cm is the maximum allowable for the JR 8611

Optimized flaps setup:

Servo arm length: 1 cm. Maximum required torque at 35° deflection and 100 mph: 195 oz/in.

Non optimized setup:

Note that the maximum allowable servo arm for the JR 8611 with a 35° flap deflection at 100 mph is 1,1 cm

RudderOptimized setup:

The optimum servo arm length is 1,4 cm. Max torque required at 200 mph and 25° deflection: 142 oz/in

Rudder non optimized ( pull-pull connection with 2,5 cm servo arm as recommended by FEJ)

The JR 8411 stall limit si reached at 10° of deflection at 200 mph !!!

Elevator optimized setup ( non mechanical pull-pull setup as explained in the F-18F thread )

The JR 8711 limit is reached at full deflection at 200 mph. At 50% stick deflection ( more realistic ) at this speed, the torque required is 312 oz/in. Within JR DS8711 specifications.

Non optimized setup ( 3,6 cm pull-pull setup as recommended by FEJ ):

The 8711 maximum capacity is reached at 29% stick deflection at 170 mph. This is not satisfactory.

I strongly recommend to all 1/7th scale F-18F the following:

Fully balance your elevators.
Use the JR DS8711 as a minimum.
DO NOTUSE THE FEJ RECOMMENDED PULL-PULL SETUP.
Use instead the setup that I have recommended in the F-18F thread ( servo arm length 1,5 cm or smaller in the pull-pull configuration with attachement points offset ).

For the other controls, set your servo arm attachement point as close as possible to the servo axis ( check the maximum values above )

Guys, please check the original file and play with it. All suggestions are welcome...

http://www.geohei.lu/olin/data/model...20controls.xls

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