Control Line: Aerobatics

Control Line: Aerobatics

Ted Fancher May 1986

Introduction

Engines make our Stunters go. One large engine that has steadily gained popularity with serious competitors is the Supertigre .60 (ST .60). I don't use this engine myself, so I called on the East Coast (New Jersey) contingent—Glenn Meador and Lou Dudkowski—to put together practical, real-world advice for the modeler who wants a reliable .60 for day‑to‑day practice rather than an ultimate contest motor.

A few cautions up front:

• We don't claim to know everything; we're passing on what works for us.
• Many expensive modifications (machining heads, angling ports, etc.) are unnecessary and can even be detrimental. The exceptions are correct ring gap and ring fit—these are important.
• This article is aimed at the regular flier who needs a dependable engine, not the top‑ten contest specialist.

Why use a Supertigre .60?

• Reliability is the main reason. The ST .60 changes less from day to day than most other powerplants.
• It provides smooth, consistent performance in relatively light airplanes (52–57 oz.), and nothing beats cubic inches for staying at the top of the performance envelope.
• If you currently run Schnuerle-ported engines or an ST .46, you may get more consistent practice time with the ST .60.

Which ST .60 to use

• There are at least six versions of the ST .60 R/C. Avoid the oldest, non–Perry‑port version.
• How to check for Perry ports: rotate the crank so the piston is at bottom dead center and look through the exhaust port at the inner bore of the liner. In the forward and rear positions you should see two vertical slots (about 1/8" × 1/8")—these are the directional/Perry ports. Removing the head makes them easier to see.
• There is no factory Control Line version; all come with R/C carbs and large mufflers.
• Once you have a Perry‑ported ST .60, you needn’t worry about which later version you have.

Basic preparation and checks

• You can retrofit a ST .60 into a plane set up for an OS Max .40/.45 FSR with only a little filing and grinding of mounting lugs and holes. Retrofit works but tank location may not be ideal.
• Consider sending the engine to a qualified shop (Tom Dixon or Karl Siefert were recommended by the authors) if you want a thorough conversion. If not, do the minimum yourself:

1. Remove the R/C carb (sell it if you like).
2. Disassemble and clean the engine only if you are familiar with engine teardown.
3. Check ring gap and fit—this is critical. A good ring gap is about .003–.004 in. Many ST .60s come with excessive gap (.010–.012 in.) or sometimes almost no gap. If the engine runs progressively lean and you have ruled out other causes, a too-tight ring gap may be the reason and professional work will be required.

Needle valve hole (case drilling)

• The next task is to drill a 3/32" hole in the case for the needle valve assembly. This is delicate—if done badly you can ruin the crankcase.
• Procedure:
• With the carb removed, locate the elongated boss on the case where the carb bolt went.
• Drill a 3/32" hole in the center of the other end of that boss on either side of the case.
• It’s best to drill from both sides separately, then run a 5/32" drill through both holes together to help align and remove binding/square errors.
• Stuff facial tissue into the case before drilling to keep metal chips out of the interior.
• Aim to be as accurate as possible, though the authors have seen engines run with slight tilt to the needle and still be fine.

Venturi and needle valve

• You need a venturi to replace the R/C carb. Options:
• Contact Bob and Rollie McDonald for venturis (set of five for about $20).
• Reuse venturis from Max .40/.45 FSRs (common and serviceable). Because the ST case is ~1 mm larger, use a slightly thicker O‑ring from an auto parts store to seal any gap.
• Recommended venturi sizes:
• Starting bore: .302 in. (N drill). Good for most setups.
• For smaller/lighter planes (under ~650 sq. in. wing area and ~50 oz. weight), consider .295–.296 in. (M drill).
• Needle valve assembly:
• You can rob the needle and venturi from your Max .40/.45 FSR.
• Preferred spray bar: Supertrio spray bar (part no. A2031222) from Hubschmidt’s Hobby Center—gives fine (continuous) adjustment.
• If using the ST spray bar, use the ST gland nut and needle to complete the assembly.
• Position the spray bar port on the axis of the venturi. Absolute squareness to the crankshaft is not critical in the authors’ experience.

Fuel tank, mounting, and fuel pickup

• Recommended tank dimensions: 1¼" × 2" × 6½" — about 15½ cubic inches (~8½ fl. oz.). This gives flexibility for prop/fuel/venturi combinations.
• Tank setup:
• Use a uniflow setup and run muffler pressure to the tank.
• The tank must be mounted higher than with Schnuerle engines: start with ¾" engine mounts and undercut to ½" in the tank compartment area so the tank can sit higher (assumes inverted engine).
• With the plane on its landing gear the fuel pickup should be about ½" above the needle valve.
• Tank height will vary with weather: lower the tank for colder conditions, raise for warmer.
• If retrofitting a .60 into an older airframe and the engine runs uneven on inside vs outside maneuvers, try moving the fuel pickup and uniflow lines up and slightly off‑center at the rear of the tank. This can help even fuel flow although it's not a perfect solution.
• Desired engine behavior: a slight "break" at the tops of Square Eight and top verticals—authors prefer the engine to break into a two‑cycle slightly more on outside than on inside maneuvers. Tank shapes used: wedge‑shaped (Veco/Fox style) or rectangular—both work well.

Glow plugs, fuel, and mufflers

• Glow plugs:
• Fox two‑volt RC glow plugs (with idle bar) have worked well. You may need to try several to find a "good one." Fox 1½‑volt RC plugs also perform satisfactorily.
• Fuel and oil:
• Use fuel with 10–12% nitro.
• Synthetic lubricants gave slightly better economy and an easier break into two‑cycle than straight castor in the authors’ experience.
• Mufflers:
• Tongue‑type mufflers by Karl Siefert (about $20) are recommended. Have Karl install the pressure fitting for muffler pressure to the tank.
• These mufflers give very little back pressure and help keep the engine steady across wind conditions.

Propellers and trimming

• Recommended starting prop: Rev‑Up 13 × 6 — a good all‑around starting point.
• Alternatives and notes:
• Try 12½" or 12" diameter for lighter planes.
• In stronger winds try a 13 × 5 Rev‑Up and lean the needle ~¼ turn.
• 13 × 5 Zinger has more pitch than the Rev‑Up and can help wind penetration.
• 13 × 6 Zinger holds the plane tightly and is very strong handling.
• AHM (English) 13 × 6 was tested with limited success; experimentation is worthwhile.
• Bigger props can introduce turning and yaw problems; several fliers (including Tom Dixon) have addressed these issues with prop/airframe adjustments.

Airframe size and recommended planes

• What’s the smallest plane for a .60? Opinions vary:
• Bob Gieseke flies a 650‑sq.‑in. Nobler successfully.
• The authors have built planes from 650–750 sq. in., and typically use about 710 sq. in.
• You can put a .60 on a 660‑sq.‑in. Stiletto and get good performance—reliability is the primary benefit.
• Plans and construction:
• Hand‑lettered Matrix‑Eagle plans (foam construction) for the authors’ planes, with notes, are available from the Garden State Circle Burners (c/o John Miske). These are good bread‑and‑butter 60‑size references.

Control system and hardware

• Use strong control systems; they are as important as the engine.
• 3/8" flap and elevator horns are available from Karl Siefert.

Troubleshooting checklist for lean runs

Before assuming ring gap is the cause, check:

1. Excessive vibration.
2. Leaky fuel tank, fuel line, or fuel filter.
3. Loose needle valve or venturi.
4. Loose crankcase backplate or head screws.
5. Any other obvious mechanical or fuel delivery issues.

If you have ruled out the above and the engine runs lean and keeps getting leaner, a too‑tight piston‑ring gap is a likely culprit and will require professional work.

Contacts and addresses

• John Miske (Garden State Circle Burners), 415 Clifton Blvd., Clifton, NJ 07013. (Plans)
• Karl Siefert, 2804 Gilham St., Philadelphia, PA 19149. (Mufflers, horns, engine work)
• Bob McDonald, 28746 Westfield, Livonia, MI 48150. (Venturis)
• Hubschmidt’s Hobby Center, Box 318, Glassboro, NJ 08028. (Supertrio spray bar A2031222)

Acknowledgments

Thanks to Glenn Meador and Lou Dudkowski for their help.

Ted Fancher 158 Flying Cloud Isle, Foster City, CA 94404

Transcribed from original scans by AI. Minor OCR errors may remain.