Building the
Great Planes 33% Pitts
by Bob Pastorello
This is my feeble effort to document the construction of a truly excellent ARF. Opinions expressed herein are mine alone...
Construction begins by sorting out all the bags/parts for identification and evaluation. As this exploded view shows, the parts are easy to identify, and don't require marking. Everything is extremely well-protected from shipping harm, and all hardware parts are bagged, some double-bagged.
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| Boxed Parts | Exploded Parts |
Review of the manual reveals a very well thought out step by step process that leaves NOTHING overlooked. It begins with some very clear warnings; "This airplane is a high performance aerobatic airplane that mimics many characteristics of the full scale airplane and operates identical to the full scale."
Included with the instructions is an "improvement sheet" which highlights some items that needed correcting. One, likely the most important, pertains to improving the control point anchor areas in the ailerons. They provide hardware to use backup plates for the horns, or, instructions about how to inset ply plates into the ailerons. I chose the latter to improve the appearance.
One begins by hinging all the ailerons, and installing all the control arms. Of course, that meant I had to do the hard point mods and let that cure before moving on. The hinge slots on mine were all PERFECTLY cut. Dead center of the surfaces, deep enough, and tight enough to let me trust the fit of the included CA hinges. GP provides plenty of material to cut into the hinges you like. The instructions even explain why it's valuable to cut away the monokote around the hinge slots, and shows you how to do it. Lots and LOTS of photos in this manual.
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| Aileron servo install | Wing Saddle fit!!! |
After the hinging, comes the joining of the panels. To make it easier, they include pull strings for the extensions. Every panel, and the top wing center section, has it's own pull string so you can't miss routing the servo extensions. Nice touch.
The laminated joiners for the bottom wing aligned perfectly, were not oversize, and there was only what I'd call "epoxy clearance" in the holes. When joining the bottom wing panels, you insert the hardwood dowels into holes that are pre-drilled, and pre-aligned in the center section. Can't miss. Of course, these match the fuse former perfectly. As does the pre-assembled, pre-drilled, and pre-covered belly pan that you glue down onto the wing. It provides the airfoil section under the fuse, and hardwood mounts for the nylon wing bolts. BY the way, the mounting bar in the fuse already has the blind nuts installed, and it is well-glued. Again, no measuring, drilling, or fuss. Just trim monokote off of holes, screw it together. Fits perfect.
Top wing was a bit of a two-person, 7 hand operation because of the center section. But it is built flat, is symmetrical, and align perfectly. I chose to go with 4 servos, so I didn't have to worry about takeoff points for inter-wing aileron rods.
Next step is to screw all the metal fittings to the wings for the interplane struts (made of fiberglas, very light, prepainted, and fit perfectly), installing the cabane struts on the fuse, then installing everything. At this point, it is looking a LOT like the Pitts we all love.
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| Cabane area |
A minor irritation was the measurement for the rear of the interplane strut on the top wing. [There is now dimensional information in the Addendum, included] The manual references 3", and that is not possible at all...mine worked out, without any 'persuasion' to be exactly 3 1/2" from the aileron TE to the rear most point of the interplane strut when mounted to the wing. That configuration worked out. Everything is nice and square, well aligned, and incidence-set properly.
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| Interplane Strut Attachments |
After the wings are attached, then comes the stab. Here I disagree with the sequence of steps, but it's just my preference. They recommend removing the monokote around the hinge slots AFTER installation of the stab into the fuse; I've found that to be a difficult method, so I did this before inserting.
The slot in the fuse for the stab is such a close fit, that I had problems figuring out how to get adequate epoxy in there. A few messages to the IMAC list, and I had some great suggestions. I used 90 minute laminating epoxy, with lots of punch pricks in the wood to give the epoxy someplace to set up "rivets"....it must have worked....the stab is VERY solid.
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| Tail Servos- note fit of stab to fuse joint |
By the way - it also aligned PERFECTLY to the firewall, and both wings. Quite a feat, considering how tricky bipes can be to get aligned.
That done, the vert fin was inserted and similarly glued, then I hinged and installed the elevators and the rudder. ALL of these steps are very carefully illustrated, and written out....you just cannot do this plane incorrectly.
Next were the pushrods. Everything is in the kit. 4-40 solid pushrods, with steel clevises, even locknuts for the adjustable clevis end. You need to be able to solder the other clevis on each of the pushrods, but by the time you've done the 7 in this airplane, you get a little better at that.
A sidebar about the tailwheel steering. GP photos on the web site show a tiller bar with springs. They have replaced that with an ingenious attachment method of a solid rod from the rudder pushrod to one side of the tiller. Even provides for no metal to metal contact, and has shock absorbing fuel tubing on the rod to dampen vibrations and shocks. After I worked through it, I was really impressed with the thought that went into the design. Again, all the parts for ALL of this is in the kit.
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| Tail Steering Linkage | Tail Steering CLOSE |
With all the radio parts mounted, it became time to tackle the firewall. My ZDZ 50 required 1 1/8" standoff. To do this, I used some hardwood square pinethat I center-drilled and made 1 1/8" long. Drilled the firewall with my ZDZ mounting template, mounted the motor into 10-32 "T"nuts in the firewall. The standoffs have 1/8" ply plates glued around them on three sides, and glued to the face of the firewall to reduce any extra shake up there. A very easy way to build a box.
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| ZDZ Mounted | Hardwood Standoffs |
Contact me - rcaerobob@cox.net