Opus MC3
Flap linkage
The flap control horn.
The aileron control horn.
Photo taken just before maiden.
This plane is just awesome! It flew straight right from launch and was a dream to fly.
The following is a summary of the modifications mentioned in the “Opus MC3 & MCT Builds & Mod's” thread on RCGroups.com. These improvements will allow you to potentially DS your MC3 towards the 300mph barrier. The post numbers in red refer to the posts describing the modification in this thread. A link to the thread is below.
http://www.rcgroups.com/forums/showthread.php?t=581867
MATERIALS REQUIRED
2 x 6mm OD carbon tubes
2 x 6mm ID aluminium tubes
2 x 5mm OD aluminium tubes (aileron mod)
1 x 4/40 thread
12 x 4/40 clevices
1 x Gary Leggerton servo tray (optional)
Approx. 500 grams of lead
Goop
Epoxy
Carbon fibre
RECOMMENDED RADIO GEAR
6 x JR DS362/368 servos (servo choices (Post 516)
1 x 7Ch FM Receiver (PCM) using External Antenna (see text)
1 x 2000mah+ 5 cell 6V NiMH Battery (Post 554)
RADIO GEAR INSTALLATION
Fuselage
The radio gear can be installed in several ways depending on the individuals preference. One way is to use a Gary Leggerton Kit (or make something similar) which uses the ‘tray’ method for securing the radio gear in place. (Post 1203)
Alternatively, it is possible to install the servos below the wing saddle, laying them flat but on an about a 45 degree angle looking at it from the front of the fuse. (Post 228). This provides ample room in the nose for balancing lead, the battery and receiver.
Another alternative is to use only one servo for elevator, and not worry about rudder. If you choose this option, it would be wise to use a stronger servo.
Antenna Installation
This could be the single most important part of your radio gear installation! When using airframes made of or heavily reinforced with carbon fibre, radio reception can become a major issue, especially if using 36 Mhz.
Under no circumstances should the antenna be ran down the centre of the fuselage (even with some extending out the rear of the fuse), as this will dangerously reduce reception. Running the antenna down the outside of the fuselage using tape to hold it there is probably the best alternative, and allow at least 300mm of overhang dangling from the rear. Some experimentation may be required here to obtain the optimum reception. I used a PCM receiver and did the above and had no problems.
A RANGE CHECK IS AN ABSOLUTE MUST PRIOR TO FLYING!
Wing
The servos for the ailerons and flaps should be installed using masking tape and epoxy. After removing the lugs from the servo casing, wrap the servo with a good quality masking tape. Ensure the servo is completely covered leaving the servo arm to move freely. A slight ‘rough-up’ off the masking tape should be done with some sandpaper. Then use some slow epoxy (not fast as it may heat up & distort the wing skin) to mate them to the wing skin in the appropriate position.
AIRFRAME CONSTRUCTION
V-tail attachment
The v-tail needs to be attached to the fuselage as strongly as possible. In addition to the 2 bolts securing the v-tail, the paint on the mating surfaces can be sanded off and gooped together to ensure the strongest bond. This is only optional however.
Elevator/Rudder Linkages
6mm OD carbon tubes are used for the push rods, using the 6mm ID aluminium tubes as guides inside the fuse. The aluminium tubes are gooped or epoxied in place. 4/40 thread and clevices attach the rods to the servos and control horns. Carbon triangles should be used to improve the strength of the V-tail control horns (Post 265).
Flap Drive Mechanism
For top driven flaps, the control horns should be extended slightly to increase the leverage on the flap. The holes in the wing surface for the clevice may need to be increased slightly to cater.(Post 618 & 623).
For bottom driven flaps, much larger horns are required to improve the mechanical advantage due to the bottom hinge. (Post 615).
In both cases, the servo arm should be set up so it runs in-line with the pushrod whilst the flap is in neutral position. This effectively ‘locks’ the flap in position, preventing it from fluttering. In the case of a top driven setup, the servo arm will point in the opposite direction to the pushrod when ‘locked’. With a bottom driven setup, the servo arm will point towards and along the pushrod. Tape may be required on the inboard gap of the flap at high speed to prevent flutter.
Aileron Control Horns
When you do the control horns, the position of them in relation to the hinge line should be carefully considered. The ‘connection’ between the horn and the clevice should be as close as possible to vertically above the hinge line to prevent flutter. (Post 316)
Aileron Tube Reinforcement
An option to stiffen ailerons to prevent flutter is to insert aluminium tubes under the wipers. However, there is a weight penalty. The tubes should stop about 25mm from both ends of the aileron to allow for flex along the hinge line. (Post 500) It should be noted that the MC3 has done 305mph without this mod.
SPECS & SETUP
Wingspan = 1900mm (74.8”)
Wing Area = 36 dm2 /558 “2
Airfoil = RG14
Length = 1080mm (42.5”)
Flying Weight = 2.4-2.8 Kg (85-100oz) plus ballast
Wing Loading = 22-26oz/square foot plus ballast
COG = 2 5/8” (66-67mm)
Elevator throws (MCV) = 6mm up/6mm down
Aileron throws = 12mm up/6mm down,
*100% Expo, 50% Dual Rate
Rudder throws (MCV) = 6mm down on left/6mm up for right etc
Crow settings = 8mm up Aileron/Full down flap
Crow Elevator Comp = 2-3mm down elevator
Thermal Flap = 2-3mm down flap
* These settings come down to personal preference.
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