Control Line: Aerobatics

Control Line: Aerobatics

Wynn Paul

Bob Hunt — World Champion (Precision Aerobatics)

Bob Hunt is the new World Champion in Precision Aerobatics, using a combination of proven components and a couple of new items. Below are the key details of his airplane, engine, propeller, and supporting gear.

Airplane (Genesis)

• Wing: 60 in. foam wing, about 720 sq. in.
• Airfoil: 18% at the root, 20% at the tips
• Equal panels with 2 in. leading-edge sweep
• 1 oz. tip weight
• Equal-span partial flaps, each 23.75 in. long
• Stabilizer and elevator: 30 in. span
• Root chord: 3.5 in. (both stab and elevator)
• Tip chord: 2.50 in. (both)
• Moment arms (measured relative to the 10.50 in. root wing chord):
• 10 in. on the front
• 16 in. on the rear
• (Clarification: this means 10 in. from the rear of the spinner to the leading edge of the wing measured at the fuselage side; 16 in. is the distance from the trailing edge of the wing to the trailing edge of the stabilizer.)

Other airframe/equipment details

• Fox 1.5-volt idle bar plug
• 5.75-oz. uniflow tank (Bob's own), using muffler pressure from his custom muffler
• Solid .015-in. lines, 6.15 ft long
• C.S.C. Tru-Just handle
• Finish: epoxy-based glue with Sig topcoat paint

Engine and Propeller

Engine

• New component: Max 40 FSR (Bob switched to this two days before the World Champs)
• Bob fitted a replacement venturi for the RC carburetor and flew immediately
• He reports the Max has more horsepower than the ST 46 and is docile enough for stunt flying while having plenty of power
• Many eastern stunt fliers are using Max 40 FSRs and Max 45s

Propeller — homemade three-blade

• Prototype users include Bob Hunt, Keith Trostle, Frank McMillan, and other New Jersey stunt fliers
• Construction:
• Uses three blades from Rev-up 12-6 props, spliced together with epoxy
• Joined with nine flat-head machine screws and two hubs
• Blades trimmed to about 11.5 or 12.5 in.; some blades trimmed narrower
• Performance: provides substantial line tension in critical places
• Safety note: this modification is not for the novice — blades operate at 8,000–10,000 rpm

Venturis, needles, and recommended props

• Both Max 40 FSR and Max 45 come with RC carbs; stunt venturis must be substituted
• Venturis available from:
• Control Specialties Company (Bob Hunt)
• Custom Master Products (Gene Martine)
• Old Max Stunt 40 venturi can be used if available; World Engines reportedly has these in stock
• Needle valve: Supertigre B-19/2/5 (from the ST 60) can be adapted with minor fitting
• Recommended props: Rev-up 11-6EW, Zinger 11-6, any 12-6, or even a 13-5

Max 45 notes

• The same venturi from the old Max 40 stunt can be fitted; venturi size about .295 in.
• Bill Simons (perennial Nats qualifier) is using the Max 45 with a Rev-up 13-6 prop
• Engine weighs about 10 oz. and appears promising

Tank Height Experiment (mixture sensitivity)

• While breaking in a pair of .049 engines for Half-A stunt, Lexington, KY stunt fliers discovered tank height has a pronounced effect on mixture:
• Moving the tank down 1 in. leaned the mixture significantly
• Moving the tank up 1 in. richened the mixture
• .049 engines are especially sensitive, but the principle applies more broadly: tank height relative to the spray bar/engine affects mixture and engine behavior
• Example: Bill Werwage’s 1977 Juno has a tank compartment that allows tank height adjustment up or down
• Common issue: engine runs richer inverted than upright
• Cure: place shims under the engine or position the tank between the engine bearers (as in Werwage’s layout) so the engine runs at the same rpm inverted and upright

Custom Master Products, Inc. (Gene Martine)

• Address: Gene Martine, 5424 Oliver St. South, Jacksonville, FL 32211
• Brochure available; products outlined below:

Custom Master muffler

• Machined from bar aluminum stock; available for Fox 35, Max 35, K&B 40, HP 40, Como 40, and ST 46
• Cost: $15.00 plus $0.75 postage/handling
• Pressure fitting available for an additional $0.75

Custom Master flight handle

• Completely adjustable with handgrip options: Delrin, PTMT, or Lexan
• Features 10-24 adjusting screws with knurled adjusting nuts
• Adjustable brass insert for flying wires to reduce fraying
• Flying cable: .047-in., 7x7 stainless steel
• Cost: $15.00 plus $1.00 postage

Other services and items

• Venturis for Max, HP, K&B, Como, and Supertigre
• Southern distributor for HP 40 engines; pricing example: $77.56 without muffler, plus $2.70 mailing
• Heli-coil installation on ST 46 engines for muffler bolt-up
• Needle relocation and Custom Master venturi installation on ST 46 and Como engines
• Gene has prepared for production to reduce availability disappointments; write for a brochure

PAMPA notes

• A Contest Directors' Handbook (draft) is now available to outline administration of a stunt meet (A, AA, AAA, or AAAA — excluding National Championships)
• Purpose: assist Contest Directors and Event Directors to organize an efficient, enjoyable meet

Contents of the Handbook

• Introduction
• Types of Competition
• Event Directors (duties and selection)
• Advance Preparation and Publicity for the Event
• Judge Selection and Training
• Scoring of Maneuvers
• Personnel Required
• Field Layout and Equipment
• Contest Procedures
• After the Competition

Types of Precision Aerobatics events (five distinct types)

• Classic (Regular) stunt event — can utilize up to four PAMPA categories
• AMA Novice Aerobatics
• Profile Precision Aerobatics
• Half-A Precision Aerobatics
• Old Time Stunt

• With a wider selection of events, more "Stunt Only" contests are possible. With proper scheduling, two circles at an "All Stunt Meet" can operate all day and provide plenty of action for competitors and spectators.

For further information on stunt or PAMPA, contact:

• Wynn Paul, 1640 Maywick Drive, Lexington, KY 40504

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