Docstoc

WattAge F 86 Sabre - DOC

Document Sample
WattAge F 86 Sabre - DOC Powered By Docstoc
					                                     WattAge F-86 Sabre


                                                       Specifications

                                                              Wingspan: 29.5 in.
                                                              Wing Area: 162.75 sq. in.
                                                              Length: 26 in.
                                                              Weight: 19.25 to 21 oz.
                                                             (advertised), 20.8 oz (actual)
                                                              Wing Loading: 17 oz./ft^2 to
                                                             18.6 oz./ft^2
                                                              Motor: Modified 380 Motor
                                                             (Speed 400)
                                                              Prop: 6 Blade Power Fan 400
                                                              Speed Control: Wattage IC-
                                                             30A, 6-10 cell, 30 Amp ESC
                                                              Battery: 10 cell 500AR and 10
                                                             cell 1100mAhr NiMH




   Introduction

The F-86 Sabre was the USAF's first swept-wing jet fighter. It made its initial flight on October 1, 1947.
The Sabre was originally designed as a high-altitude day-fighter. Subsequent models were designed as
all-weather interceptors (D model) and fighter-bombers (H model). The day fighter first saw combat
service in Korea where it engaged the Russian-built MiG-15. During this conflict, the kill ratio of the Sabre
was better than 10 to 1, with 792 MiGs shot down at a loss of only 76 Sabres.
The Wattage F-86 Sabre Electric Ducted Fan (EDF) is a sport-scale model of the Korean War era jet
fighter. Constructed of foam and plastic, it offers a short build time coupled with entry-level EDF
performance. When Dave Lilley asked me to do this review, I downloaded the assembly manual from the
Hobby People web site (http://www.hobbypeople.net). This allowed me to go over the manual a few
times enabling me to be ready to build as soon as the kit arrived. I have been flying R/C for 17 years and
I have never built an ARF or an EDF airplane, so this would be a new experience for me.


   What you get




                                                   It's here!
The shipping box had taken a beating, but the full-color display box inside was intact. The photo on the
box is an actual picture of a completed model. To me, this is better than a drawing because you can see
exactly what you are going to get. The F-86 is molded from foam, and the foam beads can be seen in the
finish. Not that there is anything wrong with this, but if you were expecting a super scale model with a
glass smooth finish, the box picture will dispel that thought.




                                    The parts come neatly packaged.
Upon opening the box, I found all of the components neatly packed and bagged. A cardboard divider
securely holds the fan and motor box. Under the divider were the fuselage halves, the vacuum-formed
parts, and two push rod wires, not much to put together. One of the fuselage's sides shifted during
shipping and was slightly damaged by the vacuum-formed parts. The surface where the two halves are to
be joined were dented, but not enough to order a replacement. The customer service address, phone
numbers, and email address are listed several times through out the manual. I'm used to having to hunt
for this information in other manuals. It appears that Wattage is serious about providing and supporting a
quality product. The fuselage is molded of light foam and is easily dented, so use care when handling it.
The wings have a light foam core and a tough outer skin to handle the flight loads. All of the foam and
vacuum-formed parts are pre-painted gray/silver and all of the flight surfaces are hinged and pre-cut.
The quality of the parts was good enough to where I didn't see any reason to substitute any of the
hardware.




                                         There aren't a lot of parts!
The 40-page manual is very detailed and provides information on selecting radio components, ESC, and
batteries. There are over 60 photographs to guide you in the assembly process. Wattage even includes a
list complete with part numbers of the extra equipment that they recommend for use in their F-86.
Newcomers to electric flight should find this information helpful.
The only additional equipment that you need to provide is a receiver, two micro servos, ESC, battery,
connectors, and about four feet of 14-gauge wire. All of the assembly procedures require the use of 5-
minute epoxy, so assembly should not take too long.


   Assembly

Since the assembly manual is very detailed, I'll just touch on the basic assembly sequence and add some
comments and hints.
Fuselage
The Power Fan 400 is a nice piece of equipment. There was very little mold flashing, but I found that with
just a few scrapes with my hobby knife cleaned it all up. The fan blade is delicate, so use care when
handling it. There is a detailed break in procedure in the manual that I followed to seat the motor
brushes. The included Speed 400 motor even comes with noise suppression caps. Double check that the
fan spins freely and that the motor wires are attached securely, as once the fan is installed you'll have to
cut the bottom out of the fuselage to work on it.
Once the fan is assembled, it is fitted to the fuselage halves and glued in place. It's been a while since
I've worked with 5-minute epoxy, and I quickly re-learned a few things. One to five minutes is an
estimate, two to five minutes elapses faster than you think when you are trying to get two parts lined up,
and three to five minutes elapses slower than you think when you are trying to keep two parts lined up.
Before you start mixing, I would suggest that you look at a clock and note the time. It pays to take a few
minutes to plan how you're going to apply the epoxy and get the pieces lines up. The manual tells you to
use rubbing alcohol and a paper towel to wipe up any excess epoxy. I soak the paper towel in alcohol
before I start mixing so I'm not fumbling around holding two pieces together while feebly trying to get
the top off the rubbing alcohol. I used several rubber bands to hold the fuselage halves in alignment
while the epoxy set up.




                      Rubber bands hold the fuselage halves while the epoxy sets up.
The motor wires run in a channel that you cut along the top of the inlet duct. For a cleaner intake, I
chose to fully tape the wires in place. I used a scrap stick of balsa with low tack tape wrapped around it,
adhesive side out. I then cut a piece of clear packing tape to length and stuck it to the balsa. I was then
able to insert the tape in the inlet duct and position it perfectly over the wires.
                         A simple jig helps position the tape for the motor wires.




                     There is limited access to the motor through the "cheater hole".
Wings
The wing assembly consists of cutting the end of the ailerons free (mine were already cut) and gluing on
the vacuum formed tips. When gluing on the wing tips, position the trailing edge corner of the wing inside
the corner of the tip. I found that pinching the wing tip at the trailing edge and applying span-wise
pressure near the leading edge of the tip is the best way to hold it in place. This way, it stretches the tip
and holds it in contact with the wing. Otherwise, you'll be trying to hold down multiple puckers and end
up squeezing epoxy all over the place.




                              I'm holding the wing tips while the epoxy cures.
Next, the wings are glued to the fuselage. The paint on the fuselage is carefully sanded away and the
wings are epoxied in place. I didn't trust myself not to distort the wing mounts on the fuselage.
Therefore, after gluing one wing in place, I placed a level across the cockpit and blocked up the wing tip.
I then glued the second wing on, keeping the fuselage level and the wing tips at the same height, so that
the dihedral would be equal on each side.




                                   It quickly starts to look like an airplane!
Tail Feathers
The tail feathers are glued in place next. The horizontal stabilizer has some dihedral, and there is a jig
outline included in the manual to aid in positioning them. I glued the jig to a piece of cardboard cut from
the display box and used some pins to hold it to the fuselage. Read the manual carefully here on proper
positioning of the jig. The photograph in the manual is from the top, and does not show the placement of
the jig, so I've included one below.




                            The supplied gauge is used to position the stabilizer.
The top skin of the stabilizer is used as the hinge for the elevators. While handling the model during
assembly, the hinge began to tear. I ended up reinforced the both hinges with some clear "Book Binding"
tape just to be safe.
Radio Installation
The servos are glued into holes cut into the bottom of the wings. I was supplied with CS-21 micro servos,
but they are taller than the thickness of the wing. If you use these larger servos, I would recommend
that they be laid down in the wing so they are not so exposed. The manual recommends CS-10 servos,
which should sit flush with the wing surface. The servo leads are routed through the foam to the fuselage
where they lay in a channel molded in the side. The channel and servo wires are covered with a piece of
silver tape that matches the fuselage paint exactly, which is pretty clever!




                                     The servos are simply glued in place.
The F-86 uses elevon mixing for control, so you'll need either a computer radio or a separate electronic
mixer. The elevators are mechanically connected to the ailerons via external push rods. It's not the
prettiest installation, but functional and accessible.




                                It uses simple but effective control linkages.
The ESC and receiver are installed next. If you solder the motor wires directly to the ESC, protect the
fuselage with some heavy cardboard. A 40W soldering iron will make quick work of the foam and plastic
parts. There is ample room in the radio tray for a small receiver and the ESC. The manual recommends
that you remove the case from the receiver and cover it with heat-shrink tubing. I used a Hitec 555
receiver, which has two circuit boards in it, and I did not want to stress the solder joints between the two
boards with heat-shrink tubing. After a little trimming of the radio tray and the surrounding foam, the
555 in the case was snuggled in the cockpit.
                                 There is ample room in radio compartment.
At this point, the manual tells you to let the battery wires hang loose until you install the battery tray,
but the manual never picks up where it left off to instruct on routing the wires. Rather than let them hang
in the middle of the inlet duct, I chose to route a channel on each side of the duct and tape the wires in
place. This should help clean up the airflow a little. From the battery tray hole in the bottom of the
fuselage, you can access the inlet duct. Use a modeling knife to cut a channel from the radio tray to the
battery tray on each side of the duct. Use clear packing tape or some of the clear scrap from the decal
sheets to secure the battery wires in place.




                                     Route the battery wires in the duct.
Final Assembly
I was impressed with how well the canopy fit. I followed the molded cut line with some scissors and it
dropped right in place with absolutely no trimming. I masked off the canopy with some electrical tape as
suggested, and then used chrome paint to add the canopy frame. Being an ARF, I would have expected
some decals for the canopy frame, but it only took me about 15 minutes to mask off and paint the
canopy.
The nose ring and battery tray are installed next. The nose ring fit is good, but I am not very impressed
with the battery tray. It required a lot of manual dexterity to keep the battery tray in place while the
epoxy cured. I used some foam rubber blocks stuffed in the tray to help keep the sides from puckering.
The battery tray cover is vacuum formed and very light. We'll have to see how it stands up to a few belly
landings. The battery pack is held in place with a twist-tie, and the cover is held on with a single screw.
This should make for quick and easy battery changes.




                                  The battery is accessed by a single screw.
The last major assembly step is to glue on the fin. The fin is just butt glued to the top of the fuselage. I
would like to see a channel molded in the top of the fuselage, so that it's not so vulnerable to getting
knocked off in flight. The glue joint was still weak after the epoxy cured, so I added a bead of aliphatic
glue to each side of the joint. There are three wing skids supplied with the kit in case you fly from a
paved strip or a rough field. Two sets of decals are included, and the kit illustrates many other possible
color schemes for those of you who want a customized finish.
                                         It's ready for paint or decals.
With the 10-cell 500 mAh NiCad pack, or with the 10-cell 1100 mAh NiMH pack centered in the battery
tray, the balance of the little Sabre was right on. There is plenty of room in the battery tray to move it
fore and aft, eliminating the need to add nose weight. To make sure I get the battery in the same
location every time, I marked the tray with a permanent marker. All up, the weight for my Sabre is 20.5
ounces with the 500 mAh NiCad pack, and 20.8 ounces with the 1100 mAh NiMH pack. This is near the
high end of the recommended weight range. Shedding the receiver case, using smaller servos, and
judiciously using epoxy should allow you to come in at the minimum weight of 19.25 ounces.
I figured that I spent a total of about five hours on assembly. I received the kit on a Tuesday and was
testing the power system on Sunday. My two-year-old and my two-month-old limited my building time,
so I ended up squeezing it in whenever I could find time. This worked out pretty well with this kit. I
would glue a wing on before going to work and then glue the other one on before going to bed at night.
This would allow the epoxy to cure fully, so I didn't have to worry about deforming a soft glue joint while
working on the next step. One should be able to complete this kit in two evenings without too much
trouble.




                                         It's ready for MiG Alley!




                                            Beware of jet blast!


   "Time to kick the tires and light the fires!"

Weather and a receiver problem kept me grounded for a few days. In the meantime, I cycled the battery
packs twice and double-checked the assembly manual. I was impressed with the static thrust of the
Power Fan 400 unit. I could definitely feel a decrease in thrust if the cheater hole was covered. Static
current draw was 10.4A with both the 500 mAh NiCad pack and the 1100 mAh NiMH pack, providing
approximately 100 Watts.
The first flight attempt was made on a calm evening. After a range check, with the motor on and off, my
assistant gave the Sabre a running throw. The result was a short, power on glide resulting in a bent nose
ring and a ripped out servo. Back at my shop, the servo was glued back in. While I waited for another
opportunity to fly, I talked with the support people at Wattage. They stressed the need to use a freshly
peaked battery, a properly broken in and oiled motor, and suggested to hold approximately 30% up
elevator until the Sabre gets on step. I ended up setting the control surfaces so that the elevators were
about 1/8" up with the ailerons neutral.




                                       The Sabre is very stable in flight.
For the next flight attempt, there was a slight breeze. My assistant gave the Sabre a solid heave up into
the wind while I held up elevator. The Sabre peaked at about 15 feet and started to descend. I continued
to hold up elevator as the Sabre accelerated and leveled out. Once on step, I was treated to a four-
minute plus flight of strafing the field and some victory rolls. I didn't attempt any loops, but I think you
would need a small dive before entering one. The Sabre was very stable with the recommend control
throws. After four minutes, I set up for a landing. I reduced power on the downwind leg and cut power
after clearing the end of the field. Holding a little up elevator made the Sabre settle down to a perfect
belly landing.




                                          Coming down MiG Alley!
The third flight attempt was a repeat of the first one. I forgot to hold up elevator on launch and was
unable to build up enough speed to pull out. One of the wings popped off and the battery cover needed
some work. The repairs only took a few minutes and the Sabre was ready to go again.


   Conclusion

The Wattage F-86 Sabre EDF is an easy to assemble ARF. Anyone with a kit or two under their belt
should have no problem with assembly. I would emphasize the need for a good strong hand or a bungee
on launch. Once in the air, the flight performance is stable and predictable.
There have been numerous posts on the discussion forums on improving the efficiency and performance
of the F-86. There are several possibilities for motor and fan upgrades and some simple modifications to
the duct that will improve performance. Modifications that I plan to try are reshaping the "cheater hole"
on the bottom of the fuselage, filling the space between the nose ring and the inlet duct, and reshaping
the battery tray to clean up the inlet duct. If you plan to upgrade the power system, you may want to
add a spar to the joint where the wing meets the fuselage. To me, these joints are the weakest point of
the model, and can be easily strengthened by inserting one or two spars a few inches into the wing and
fuselage.
                                      Here is a reshaped cheater hole.
On the box top, there is a picture of a Sabre shooting down a MiG-15. I hope that Wattage is considering
a MiG companion to the Sabre, so we can re-enact some early jet age dogfights.

				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:110
posted:3/3/2010
language:English
pages:8
Description: WattAge-F-86-Sabre