Assembly and Flight Review of the 

Zenith F3J- Carbon

By Mark Taylor

If you'd like to see the sales specs on a Zenith go here.

 

Flight Review

 

7/30/2001- Flying review- All I can say is WOW!!!   I originally bought two of these planes after Tom Copp saw it fly for the first time and got a little stick time on it himself he started bargaining to get the second kit back for himself (fat chance).  

Launches-  It's a big plane and it pulls hard on launch.  All launches have been pretty boring where the plane tracks straight up on tow with little input required.  After flying for a while I have slowly moved the tow hook back so it is right on the CG (102mm from LE).  The plane is going very vertical on tow, but never bobbles.  Since the airfoil is high camber, I switch to reflex mode at the top of tow before the zoom.  This allow the plane to achieve very high launches and prevents it from pulling up on zoom.  I am very confident that for F3J the Zenith will out launch most everything that is out there (big airplane, pulls well, not very heavy).

Control Authority-  Here was the big surprise.  I set this thing up similar to other big airplanes, where you want almost as much aileron throw as possible. I WAS WRONG.  This plane has about as crisp of controls as most 120" planes.  I ended up reducing throws on ailerons, they weren't needed and induced more drag.  Many big planes (i.e.- Agat, Sharon) you feel like you are along for the ride and the air controls your plane more than you do.  With the Zenith, you don't get pushed out of thermals and the control you have over the plane will make you very confident circling down low.

Thermaling-  This plane indicates air well, and climbs even better.  Hmmm.... Maybe those funny tiplets do something.. The plane feels rock solid circling real slow and trying to squeeze some altitude out of the lightest air. A standard 120" AMA plane just can't touch the Zenith in it's ability to climb.

Covering Ground-  Having the best climbing airplane in the world doesn't do you any good if it doesn't have the penetration to get to the good air.  The Zenith has amazing "cruising" ability. Actually, not so amazing when you remember it's size and the thin airfoil (8%). Just put the plane in reflex and scoot to the other side of the sky with little altitude loss. With 3% camber, this airplane should be flown in reflex mode more of the time than most other planes. I accidentally left the plane in reflex mode as I entered a thermal already occupied by about 5 120" TD planes.  The Zenith was climbing at the same rate they were, but flying about twice their speed. When I finally switched to thermal mode, the Zenith immediately started out-climbing the pack and ended up about 300 feet above the group, yeehaww.

Stability-  This plane is hands-off stable.  With a generous amount of polyhedral the plane is extremely stable.  This is an important trait for F3J which often times is a contest seeing who can fly their plane the furthest away. When banked and circling it is neutral and requires little input to continue to circling. 

Landing-  This was the surprise category.  For such a big plane it lands really well.  I can hit a frisbee with this plane as often as I could with my smaller AMA TD plane.  The landing performance comes from the very large flaps,  crisp aileron control (as mentioned above), and low wing loading. 

Learning Curve- Some planes take a while getting used to and you have to fly them for a long time before becoming confident and becoming skillfull in flying them.  I became confident flying this plane in a time that would be measured in minutes, not hours or weeks.  Within a couple flying sessions on the plane, I decided I liked flying this plane more than any other TD airplane I own (more than 10). With only about 4 flying sessions on the plane I decided to fly it at Pasadena Rose Bowl contest.  It held true to form and I got 7th place.   As US F3J team selection approaches, I am confident that the plane will fly well for me. 

Mark@f3x.com  7/30/2001

 

 Assembly Process

6/15/2001- As I examine my kit I am very impressed. The quality is very high. The plane only requires radio installation and surface control horn installation.  This plane is going to make a GREAT F3J ship for team selection.  At 135 inch span and aprox 77oz (in Carbon!) it should launch great regardless of the hand towing rules they decide to use.

Click on pictures below for larger picture.
6/24/2001:  I like to start cutting on a new plane as quickly as possible. It makes me less scared of building it.  I typically start by cutting out the servo pockets. I make round corners to lessen the stress in the corners.
After testing all the new servos, I attack them with the dremel.  I cut off the lugs and then use a cutoff wheel to scrape up the case. This allows the glue to hold the servo better.
Tip Panel-

I make a measurement from the wingrod (3/4") and cut a hole at the root of the tip panels that the servo wire will exit.  The plan is to permanently glue the connectors in the ends of the center panel and have the connectors in the tip panels floating.

Tip panel-

Dohh..  The servo lead is not long enough without cutting and splicing.

Tip Panel-

These Tip panels are thin! These are thin servos and they just barely fit, thickness wise.

Servo wires have been spliced. Radio turned on and servo centered (make sure moving in right direction). Note: When servo is centered the servo arm leans toward the leading edge about 15 degrees.

Tip Panel-

Top view of Aileron servo install.  Note: Servo is oriented so that arm is towards trailing edge, if not, the servo cover will not fit.

I used 5 minute epoxy to glue the servo in place.

Tip Panel-

I used the Dremel to route out a hole in the bottom of the aileron for the control horn.  I was very careful to go all the way to the top skin, but not through it.  I cut the control horns so that when they are in the center of the clevis hole will stand 7mm above the bottom surface.  The arm I am using on the servo is also about 7mm from center to hole.  This should give me aprox the correct amount of throw.

Tip Panel-

A sneak peak at the aileron control horn with the aileron bent away 90 degrees.  Note: I used a healthy dose of epoxy to secure the control horn.

Building Session 6/27/01
FLAP- Control Horn

Next I'm going to tackle the flaps.  The control horn for the flaps will be located on top of the flap rather than on the bottom.

FLAP- Control Horn

Here's a pic of the top of the wing with my fingers bending back the flap The opening is where the pushrod will attach to the flap control horn.  In the pic is the aluminum horn I'm planning on imbedding in the flap. It's dark, but you can just barely see the oversized hole I drilled in the flap.

FLAP- Control Horn

Okay, now to figure how far out this thing should stick.  I took measurements on similar planes I own and decided that the center of the hole on the control horn should be 11mm from the hinge line. I marked 11mm on a rod and pushed it down to the hinge line to get a feel for where the control horn is going. 

FLAP- Control Horn

What the heck?  I've used a couple of little sticks and music wire to hold the control horn in place while I try to get everything set. Remember,  this process has to be repeatable so I can do the second flap exactly like the first.  I moved things around and check with my little measuring stick to verify I'm 11mm from hinge line. Notice the control horn is angled upward at aprox 30 degrees and when the flap is in nuetral position that the clevis hole is aprox 2mm above top skin of wing.

FLAP- Control Horn

Here is another angle on the flap controls. Notice the clevis hole is also 2-3 mm in front of trailing edge of the top skin of wing. 

FLAP- Control Horn

I mixed resin with microballoons to get a mixture that would pretty much stay in place. PS- in hindsight,  It would have been stronger if I had chopped fiberglass and mixed it in.

FUSE- Radio Gear in Nose

This is after cutting on the fuse making holes for radio install.

FUSE- Radio Gear in nose

This is with all the gear in the "test fit"

 

FUSE- Radio Gear in nose

Notice the 2 servos are installed in line, but each are slightly off from center. Since the fuse is very narrow, this is done to center the highest part of the servo (the servo arm) in the fuse so that they don't hit the top of the nosecone. Notice the black line is the center line of the fuse.  After lots of calculation, I figured that to offset the servo properly, the black drawn centerline on the fuse will be directly under the "servo mounting screw hole". This of course only applies if your using the same servos.

Tail- Control Horns

The tail is a dandy 2 piece removable job. This should come in handy when I travel to F3J team selection to kick everybody's butt with my new Zenith.... Ooops, back to building.

Note- tail was set with gaps for photo!

Tail- Control Horns

This is the bottom of tail. Notice the control horns are driven from the outside.

Tail- Control Horns

You will need to drill a small hole on the flat spot of the surface and glue in place the supplied control horns.  Note: Make sure you place it as far away from the fuse as possible of you may run into problems with it rubbing against the fuse.

Tail- Control Horns

Another angle of tail controls.