Lojik
70cc twin V2
Hi all,
I want to document the ARF build of my 91 Yak, This is my first Yak, first large 3DHS model and first DA engine so kinda excited for this build.
Some details below taken from the manufactures website about the model:
Specifications:
Winspan: 91"
Length: 86.5" prop to tail
Wing Area: 1425 Sq. Inches
Weight 17-20 lbs.
The 91" Yak is great-looking model of the dramatic Yak-55M, a world-champion aerobatic aircraft.
The 91" Yak has all of the features you have come to expect from a 3DHS 50-60CC ARF - Carbon wing and stab tubes, genuine Ultracote/Oracover material, premium-grade balsa and ply, molded carbon landing gear, aluminum-center lightweight wheels, spring tail-wheel, composite and aluminum reinforced landing gear mount, composite control horns with HD ball links, aluminum-reinforced motor box, pre-hinged surfaces, and wing and stab bags.
The Yak adds some new features, including differential-drag wing tips. You can select the type of wingtip arrangement you want, for more or less yaw stability, as suits your style of flying.
The Yak 55M has the ability to rotate in yaw with authority, giving high rotation rate to gyroscopic maneuvers - this equal wild stunts like insane pop-tops. The specially-developed fuselage profile gives excellent post-stall stability for easy harrier. The reduced girth of the fuselage and low-drag airfoil profile give the Yak a very wide speed range, making an excellent dual purpose precision and 3D hucking machine.
Because of its large control surfaces and wide speed range, we recommend only the best servos for the Yak 55. Minimally, you will need a digital metal gear servo with at least 250 oz-inches of torque for each of the 5 servo locations. For best performance, 290 or more oz-inches of torque is recommended. The 333 oz-in Hitec 7955-TG or 7954SH are excellent choices. For the best possible performance, consider the Hitec HSB-9370TH Brushless servo.
For this build I will putting the below into the aircraft:
Engine: DA70 - Jtec Mufflers
Servos: PilotRC Servos on all surfaces - I know its a little lower than recommended but I'm not a high energy guy, prefer slow and smooth so I think they will be ok
Throttle Servo: HS5565MH or Savox alternative depends what I have on shelf
Power Distribution: BoomaRC Power Bus 824 from AR
Power: 2 x 2600mah BoomaRC LifePO4 Packs
Ignition Power: Tech Aero Ultra Ibec
Tank: Fourtitude 32oz Tank - yer i know i can go 16 but I prefer the 32 for convenience of longer flights and not to worry on fuel.
Epoxy: Selleys Araldite for general epoxy work, Loctite Hysol 9462 for High stress areas
Plan is to have this beast in the air in 2-3 weeks, I work long hours and can only work a little at a time, plus its winter here so not much opportunity to fly just yet
Some Vids of the plane:
I want to document the ARF build of my 91 Yak, This is my first Yak, first large 3DHS model and first DA engine so kinda excited for this build.
Some details below taken from the manufactures website about the model:
Specifications:
Winspan: 91"
Length: 86.5" prop to tail
Wing Area: 1425 Sq. Inches
Weight 17-20 lbs.
The 91" Yak is great-looking model of the dramatic Yak-55M, a world-champion aerobatic aircraft.
The 91" Yak has all of the features you have come to expect from a 3DHS 50-60CC ARF - Carbon wing and stab tubes, genuine Ultracote/Oracover material, premium-grade balsa and ply, molded carbon landing gear, aluminum-center lightweight wheels, spring tail-wheel, composite and aluminum reinforced landing gear mount, composite control horns with HD ball links, aluminum-reinforced motor box, pre-hinged surfaces, and wing and stab bags.
The Yak adds some new features, including differential-drag wing tips. You can select the type of wingtip arrangement you want, for more or less yaw stability, as suits your style of flying.
The Yak 55M has the ability to rotate in yaw with authority, giving high rotation rate to gyroscopic maneuvers - this equal wild stunts like insane pop-tops. The specially-developed fuselage profile gives excellent post-stall stability for easy harrier. The reduced girth of the fuselage and low-drag airfoil profile give the Yak a very wide speed range, making an excellent dual purpose precision and 3D hucking machine.
Because of its large control surfaces and wide speed range, we recommend only the best servos for the Yak 55. Minimally, you will need a digital metal gear servo with at least 250 oz-inches of torque for each of the 5 servo locations. For best performance, 290 or more oz-inches of torque is recommended. The 333 oz-in Hitec 7955-TG or 7954SH are excellent choices. For the best possible performance, consider the Hitec HSB-9370TH Brushless servo.
For this build I will putting the below into the aircraft:
Engine: DA70 - Jtec Mufflers
Servos: PilotRC Servos on all surfaces - I know its a little lower than recommended but I'm not a high energy guy, prefer slow and smooth so I think they will be ok
Throttle Servo: HS5565MH or Savox alternative depends what I have on shelf
Power Distribution: BoomaRC Power Bus 824 from AR
Power: 2 x 2600mah BoomaRC LifePO4 Packs
Ignition Power: Tech Aero Ultra Ibec
Tank: Fourtitude 32oz Tank - yer i know i can go 16 but I prefer the 32 for convenience of longer flights and not to worry on fuel.
Epoxy: Selleys Araldite for general epoxy work, Loctite Hysol 9462 for High stress areas
Plan is to have this beast in the air in 2-3 weeks, I work long hours and can only work a little at a time, plus its winter here so not much opportunity to fly just yet
Some Vids of the plane:
This guy says you don't need it but 
this guy says do it.