RC Jets
Jim Hiller, 6090 Downs Rd., Champion OH 44481
Top Gun and event notes
I went down to Florida for the Top Gun Scale competition, and what a show! The jet competitors showed up in force, and many top places went to jet modelers. You'll probably read about this show in many magazines.
Congratulations to Terry Nitsch on another win in Expert Scale. Congratulations to Jeff Foley on his Designer Scale win and on winning Mr. Top Gun 2000.
The talk about the new AMA turbine rules has been very positive among jet modelers and those involved with the business of turbine engines and aircraft. There are plans in the industry to take full advantage of the new rules to improve the jet-modeling experience. Products to help us utilize the freedom offered by these new rules will be developed and improved in the near future.
Golden West Models update
The rumor mill is active about the future of Golden West Models (GWM), so I called Tad Krzanowski to get the scoop on what's really happening.
- Tad has assumed full ownership of the business and will continue to support all existing products.
- Service and sales of GWM FD 3/67, JetCat Hammer P-80, and JetCat P-120 turbines will continue with no changes.
- Plans include adding to the kit line to include many more aircraft than just the Hot Shot now offered.
Watch the GWM Internet site at http://goldenwestmodels.net for additional information.
Web resources for newcomers
The easy access to information on the Internet has definitely changed how we stay informed of new model products. Most of the ducted-fan and jet modeling business community have excellent web pages for online shopping.
If you're new to jet modeling and desire information, start at the Jet Pilot's Organization web page. The links to businesses from this site include most major manufacturers who support ducted-fan and jet modeling.
The JPO web page is at www.jetpilots.org.
Field and flying notes
The flying season is well underway now, and everyone has new models coming out of the workshops. I have had the pleasure of some test flights, and the quality of ducted-fan and jet models continues to improve and complicate.
Test flights were completed on Joe Lewis's new Jet Hangar F-86 Sabre. This is Joe's second ducted-fan model, and he took advantage of this project to add all the options he could to ease jet modeling.
- The airplane weighs 8½ pounds.
- It is equipped with Robart gear struts, full gear-sequencing gear doors, and no auxiliary inlet hole.
- A K&B 7.5 with a Turbok fan pushes this model around well.
Joe is still dialing this airplane in, but all systems have worked without problems so far. The landing-gear doors are actuated with air cylinders queued by an Ultra Precision U.P. 2 sequencing valve. This valve allows one to set up the gear doors to close in the up and down positions. Not only is this scale for an F-86, but it also protects the inner main gear doors and the nose-gear door from handling damage.
Ground-handling and takeoff tips
Flying with these new ducted-fan modelers means passing on many experiences we practiced fliers went through as we came up in the ducted-fan ranks.
Ground-handling issues are one area where we can help newcomers. We normally fly jet models from paved runways, and they require longer takeoff rolls at higher speeds than typical propeller-driven aircraft. This brings along special spin-up issues to improve ground handling.
Carefully aligning the main gear toe-in is necessary; it can greatly affect handling. Main gear tires should be between straight and 1° of toe-in. Too much toe-in results in excessive drag, making it hard to attain enough speed for takeoff and to rotate for takeoff. Jet models do not have the advantage of propeller blast over the elevator to rotate the model on takeoff.
One easy way to align the main gear is to run a piece of music wire through the strut axle hub of one gear, all the way across to the other gear and through its axle hub. This assures a zero-toe-in setup.
The play in the scissors links of shock-absorbing landing-gear struts will ruin all the work you put into aligning the tires. The standard Robart shock struts use tabs on the strut for the scissors link pivot pins. These tabs often get bent out of position, resulting in play in the struts. The tires naturally pull into this play, resulting in greater toe-in with greater drag, making it more difficult to rotate the model on takeoff and dramatically lengthening the takeoff distance.
A simple correction is to bend the tabs out tight to the scissors links, then carefully fit a piece of brass tubing over the pin to space the tabs tight against the scissors links.
CAI Razor construction and finish
Construction of my CAI (Crow Aviation, Inc.) Razor continues. I've finished the painting and have begun the final installation of all systems. This model is mostly complete—I just have to follow the instructions and complete the wrenching.
The finish of the fiberglass was beautiful, with only minor filling required. Fit of the hatches was good, although I did use some body filler to fit the main top hatch to get a tight quality fit similar to some of the show airplanes often seen.
CAI has its own line of hatch latches, hooks, and receiver slots for hatch fitting. These products were extremely easy to use and attached well with CyA (cyanoacrylate) glues.
I have painted the interior of the fuselage aft of the turbine with Bob Violett Models Heat Shield ceramic barrier paint to protect the fuselage and paint from heat radiating from the turbine exhaust tube. However, that was overkill in this model. CAI Razors and Raptors have proven that they have no problems in this area, but I wanted to use all available technology to protect my investment.
The can of Heat Shield looked rather thick and dried up when I opened it, leaving me a bit concerned. I followed the directions and stirred it up, and it had the consistency of a thin paste. Do not thin Heat Shield; that is the correct density. Heat Shield brushes on easy, spreads well, and only required two coats for complete coverage.
CAI retracts, valves, and sequencing
The new CAI retractable landing gears installed easily and fit perfectly. All the right parts were included with the kit, and they worked per the instructions. Gear doors fell right into place, although I had to use air cylinders on both main gear inner doors and on the nose-gear door.
I did cheat by mounting the main gear inner door cylinders directly on the main landing-gear cover plates, instead of inside the wing. This avoids the need to disconnect the pushrod from the doors when removing the cover plates for gear maintenance.
The Razor is equipped with one air valve in the wing to close the inner main gear doors and a separate air valve in the fuselage to close the nose-gear door. This reduces the number of airline connections to the wing to two lines—one for gear down and one for gear up. All sequencing of the main gear doors is contained in the wing.
- The main gear inner door valve is mounted per instructions, operating off the landing-gear strut on the left side only.
- Two airline restrictors are installed on the left retract unit to assure that it retracts slower than the right landing gear, avoiding sequencing issues.
- The nose-gear-door air valve is mounted directly on the nose-gear retract unit, actuating off the retract lever. My installation of this air valve is not exactly per plans, but it has worked out very well. This type of installation has proven reliable in most models.
Nose-gear steering and maintenance
The new CAI nose-gear-ratchet unit has pushrod-actuated steering—a feature many prefer over cable systems. Maintenance is simpler with pushrods compared with cables.
If you are flying a model with cable-actuated nose-gear steering and continually have to readjust your steering, you need to stretch those cables prior to use and try making up a new set.
- Hang a five-pound weight from the cable line for at least 24 hours, then make up your new steering cables from this pre-stretched cable.
CAI uses the heavy-duty Robart landing-gear struts. The scissors link pivot pins run through tubes welded to the struts, resulting in a tight fit with minimal play in the scissors links. Provisions are made on these landing-gear struts for attaching the gear strut doors directly to the struts with 2-56 screws. These are the types of details that jet modelers are coming to expect in all gear struts.
Wheels, brakes, and final setup
The Razor was supplied with Glennis wheels, tires, and brakes. These products have a history of quality, and they did not disappoint.
I set up the brakes by fitting a spacer between the wheel and the brake caliper. This keeps the caliper tight against the strut without binding the wheel against the brake disc when the disc is in the retracted position. This little extra time spent on setup reduces brake drag when the brakes are not applied.
Closing
Well, it's time to get back to the shop—it's flying season. Let's get out there and fly those hotrods we've spent all this time building. MA
Transcribed from original scans by AI. Minor OCR errors may remain.
