OHIO MODEL Products 120CC Yak SP-55M User manual

120CC Yak SP-55M
Giant Scale Aerobatic Aircraft

Specifications:
Wing Span: 108 inches
Length: 100 inches (including spinner)
Wing Area: 2105 sq. in.
Flying Weight: 26 to 28 lbs
Engine: 100cc to 120cc Gas
Radio: 6 to 9 Channels
Servos : 180 - 330 oz required
OHIO MODEL PRODUCTS
199 Stratford Lane
Xenia, Ohio 45385
[phone]
www.ohiomodelplanes.com
email: [email protected]
All contents copyright 2012, Ohio Model Products
Version 2.0, Jan 2012
Dear OMP Customer,
Thank you for purchasing the new OMP/EG giant scale aerobatic aircraft. This manual covers the
Yak-55M aircraft. Ohio Model Products is known worldwide for the best profile aircraft designs around
and many innovative construction techniques. We’ve taken this expertise and teamed up with EG Aircraft
to bring this new model to the radio control enthusiasts. The Yak-55M is designed for the popular 100-
120 cc engines and weighs about 26 lbs to 28 lbs. Perfect for IMAC or Freestyle, this new OMP giant
offers everything you want in a giant scale aerobat including great looks! Covered in genuine Ultracote,
this ARF comes with premium hardware, composite landing gear, carbon fiber wing and stab tubes,
carbon fiber reinforced wing and fuselage spars, carbon fiber spinner and pre-hinged elevators and
ailerons. We hope you will enjoy your new OMP giant scale aircraft as much as we have.
Sincerely,
John Drake and Bradley Petty
A QUICK WORD ABOUT SAFETY AND RADIO CONTROL FLYING MODELS
With radio control aircraft, like any hobby or sport, there are certain risks. The operator of these
models is responsible for these risks. If misused or abused, you may cause serious bodily injury and/or
damage to property. With this in mind, you will want to be certain that you build your model carefully
and correctly. If you are not an experienced flier, have your work checked and ask for help in learning to
fly safely. This model aircraft is not a toy and must be operated and flown in a safe manner at all
times. Always perform a pre-flight check of the model including all control surfaces, proper function of
the radio gear, structure, radio range, and any other area relating to the safe operation of this aircraft.
Models are not insurable but operators are. You can obtain coverage through membership in the
Academy of Model Aeronautics (AMA). For an AMA information package call 1-800-435-9262, ext.
292 or visit the AMA website at "www.modelaircraft.org".

By the act of using the final assembled model, the purchaser/operator accepts
all resulting liability.
OHIO MODEL PRODUCTS WARRANTY AND RETURN POLICY
Ohio Model Planes guarantees this product to be free from defects in both material and
workmanship at the date of purchase. This does not cover any parts damaged by use, misuse or
modification. In no case shall OMP's liability exceed the original cost of this kit. Because OMP has no
control over the final assembly or equipment/components used in the final assembly, no liability shall be
assumed for any damage resulting from the use of this model by the user. By the act of using the final
assembled model, the user accepts all resulting liability. If you should find any missing or damaged
parts, or have any questions about this product, please contact OMP within 30 days of the purchase in
order to be covered by our warranty. You may contact OMP at [email protected] or call
OMP at [phone]. If you wish to return this product you must first contact OMP and a 15%
restocking fee will be assessed. The customer is responsible for all return shipping charges both ways and
any damage as a result of misuse or shipping.

Included Features:
Carbon Fiber Wing and Stab Tubes
Carbon Fiber Reinforced Wing and
Fuselage Spars
Airfoiled Composite Landing Gear
Included Servo Clips
Complete Hardware Package
Carbon Fiber Tail Wheel Assembly
4 1/2" Carbon fiber Spinner
Included
Long Aluminum Servo Arms
Included
Advanced Ball Links and Pushrods
Pre-installed Fuel Tank
Ultracote Covering
Items Required to Complete This Model:
100-120 cc gas engine with stock or
aftermarket exhaust systems
Appropriate propeller for your engine
All required engine and exhaust mounting
hardware
Ignition battery and switch
One quality throttle servo and appropriate
servo arm
Six high quality metal gear servos of 180 in-
oz or better for the ailerons and elevators
One or two high quality rudder servos
totaling at least 330 in-oz or better
Appropriate servo arms for the above
Heavy duty servo wire extensions. OMP
recommends two 42”, two 18”, three 12”,
two Y-harnesses, two 6”, two 6” extensions.
Your installation though may vary.
Two heavy duty switches with charging
jacks for the Rx
Two high quality Rx batteries of significant
capacity to power your choice of servos.
One Receiver of your choice
Shop Supplies/Tools
Covering Iron and heat gun
Assortment normal hobby tools such as
screwdrivers, hobby knife, drill and drill
bits, pliers, etc.
Thick and Thin CA adhesives
30 minute Epoxy
Isopropyl alcohol
Ruler or tape measure
Blue thread-lock or equivalent
Note: As with all kits, it’s a good idea to read all the instructions and study the parts
before you begin construction. Handle the parts of this kit with care so you do not
damage any of the structure or covering. Inspect all the parts for any shipping
damage and report any issues to OMP as soon as you can. Make sure you have a flat
and sturdy workbench and follow all safety advice for the tools and adhesives you
plan to use.

AIRCRAFT COVERING:
1. With all ARFs, varying temperatures and storage delays can cause covering material to loosen over
time and transportation. OMP recommends lightly going over all the covering with a covering iron
set at medium temperatures. Be sure to use a soft cover over your iron so you do not scratch the
covering surface. Be sure you go over all seams and edges of the covering to assure it is secure to the
airframe and other covering. Be careful not to apply too much heat or you may cause bubbles or
damage to the covering. A heat gun may also be used along with a soft cotton cloth to shrink and
adhere the covering. Again, be extremely careful when using a heat gun.
2. Be sure to seal any exposed wood with a thin coating of epoxy to prevent engine oil from soaking in.
This is especially important around the engine compartment and servo openings with exposed areas.
3. Some modelers prefer to seal the hinge gaps using strips of appropriate covering or clear trim tape.
We have found this to be helpful with models intended for higher speed flight or models with
unusually large hinge gaps. OMP aircraft utilize a very tight double beveled hinge line and do not
normally require this step. Sealing the hinge gaps is therefore left as an option for the modeler.
RUDDER INSTALLATION:
1. It is much easier to install the twin control horns before installing the rudder. Locate the fiberglass
rudder control horns, ball links, and associated bolts and nylon-insert lock nuts. Use some fine sandpaper
to roughen up the center areas of the two control horns so that the glue adheres better. Using a sharp
hobby knife cut the covering away from the slots in the rudder and trial fit the two control horns.
2. Mix up some 30 minute epoxy and coat the inside of the slots and the center of the control horns.
Hint: a scrap piece of 1/16” ply, tooth pick, or old hobby blade can be used to coat the inside of the
rudder slots. Slide the control horns in place and make sure they are centered perfectly by using a ruler to
measure between the pivot holes and the hinge line. Wipe any excess glue off with isopropyl alcohol and
paper towels. Install the ball links, bolts and nuts into the holes to help assure alignment of both control
horns while the glue cures. Set aside until cured. NOTE: There are pictures of different planes in this
manual, however, this plane’s rudder is assembled the same way.
3. The slots for the supplied flat hinges are pre cut. Locate the flat hinges and dry fit the hinges and
rudder into place and test the operation. The hinges should seat fully into the slots so that the hinge line
gap is minimal while still allowing full rudder deflection.
4. Before gluing the hinges in you must first clean the hinges of any mold release agent using isopropyl
alcohol. OMP also recommends scuffing up the plastic with light sandpaper for maximum glue adhesion.

5. Mix up some 30 minute epoxy and using a toothpick or small wooden dowel coat the inside of each
hinge slot with epoxy. Also put a thin layer of epoxy on one side of the flat hinges. Install this end into
the slots of the rudder and make sure each hinge is properly aligned at exactly 90 degrees to the hinge
line.
6. Now coat the other end of the flat hinges with epoxy and install the rudder into the trailing edge of the
vertical stabilizer. Again, make sure the hinges remain in proper alignment. Using paper towels and
some isopropyl alcohol clean off any excess epoxy from the hinges and surrounding areas.
7. Make sure the rudder is fully seated so that the hinge gap is minimal while still allowing full deflection
of the rudder. When satisfied, use some masking tape to hold the rudder in place along the bottom and
counterbalance. After the epoxy has cured, remove the masking tape and check for proper operation. If
the hinges are dry some light oil carefully placed on each hinge will help greatly.
LANDING GEAR ASSEMBLY:
1. Locate the supplied main and tail wheel landing gear parts and sort them out on your workbench.
NOTE: There are pictures of other planes in this manual, however, the Yak-55M is assembled the same
way.

2. Bolt the main gear to the bottom of the fuselage using the supplied bolts. Use a small drop of thread-
lock to secure the bolts in place.
3. Bolt the gear cover plate in place using the single bolt provided and the hole in the center of the gear.

4. Install the main wheel axles to the composite landing gear and tighten the nylon-insert lock nut. Install
one wheel collar onto the axle. Use a second wheel collar as a guide to leave a gap on the inboard of the
axle. Use a small drop of thread-lock and tighten in place. Slide the wheel onto the axle and install a
second wheel collar also using thread-lock on the set screw.

5. Fit the wheel pant in place and install using the two supplied screws. Use thread-lock to secure the
screws in place. Repeat the above steps for the other main gear.
6. Begin the tail wheel assembly by installing the shaft bushing and lock nut into the large hole at the rear
of the tail wheel bracket. Slide a wheel collar onto the pre-bent tail wheel wire and tighten in place as
shown. Now slide the wire into the bottom of the bushing and install the steering post and tighten the
screws firmly. CAUTION: Use thread lock and don’t over tighten as metal will strip. Install the wheel
using two supplied wheel collars. Again, the use of thread-lock on any metal to metal screw is advised.

7. Center the tail wheel bracket on the rear of the fuselage and screw in place using three of the supplied
wood screws. Remove the screws and harden the holes with a drop of thin CA. Allow the CA to cure
and then permanently install the tail wheel bracket.
8. Locate the ball link end for the tail wheel wire and drill a small hole a few inches from the rear of the
rudder along the bottom. Glue this in place with thick CA or epoxy. Slide the steering wire through this
guide and into the aluminum steering arm. Tighten the set screw firmly. Test the deflection of the rudder
to make sure there is no binding and that the steering wire does not slide out of the support guide.
RUDDER CONTROL INSTALLATION:
1. The YAK-55M is supplied with a high quality set of pull-pull cables and ball-links. NOTE: There are
pictures of other planes in this manual, however, the YAK-55M is assembled the same way.
2. Install your rudder servo(s) into the precut locations in the fuselage. You will need 3 inch arms on the
servo(s). Or you can mount the supplied rudder arm to your circular servo arm. If you use two rudder
servos it is best to connect them to two separate channels and mix them together in your radio. Set up
your radio accordingly and center the rudder servo(s). The geometry of your servo arms relative to each
other and the rudder horn is critical for proper rudder operation without binding or excess cable slack.
3. If you are using two rudder servos you will need to set up the servo coupling very accurately to assure
zero binding and drain on your batteries. Threaded couplers and ball links are provided for your use. If
you are new to multiple servos ganging and programming of servos, OMP highly recommends you seek
the assistance of an experienced modeler in your area. Miss programming of servos can lead to very high
drain on your batteries and possible servo failures.