Greetings everyone from the Southern Hemisphere!

I am trying to locate a set of 1/2A Proto Speed Rules from around 1970: Before they evolved into the current 1/2A Profile Proto Speed (I assume that's what happened).

Back in the day, the event was flown in South Africa according to AMA Rules of the era. Unfortunately the archives here have not revealed a set, so I am hoping that the birthplace of the event reveals a set.

Thank you in advance
Peter

Quote from: Peter Lott on August 13, 2026, 08:10:10 AMGreetings everyone from the Southern Hemisphere!

I am trying to locate a set of 1/2A Proto Speed Rules from around 1970: Before they evolved into the current 1/2A Profile Proto Speed (I assume that's what happened).

Thank you in advance
Peter

I do not have a 1970 AMA rulebook.  However, I do have the 1972 rule book.  This provides the rules for the two proto speed events including 1/2A Proto.  This shows that 1/2A proto still required a full fuselage with a fully cowled-in engine except Junior 1/2A Proto Speed  I will copy what I think are the pertinent rules from that 1972 rule book:

"6.16  DESIGN OF MODEL  (PROTO),  Proto speed model airplanes need not be scale models.  However, the design must resemble that of a full scale airplane.  The model must have a full fuselage and rudder or butterfly tail.(A model with a small fuselage and helmet cowl, as is now common with most speed models, will not be acceptable.)  Model must have a cockpit or cabin in proportion to the total model.  No pod and boom fuselages, flush or prone position cockpits or flying wing designs will be acceptable unless they are actual scale models of original full scale aircraft. The engine must be completely cowled except in cases of a scale model.  If the builder wishes, the spark plug, or equivalent and head fins may be exposed.  Wing area enclosed in a fuselage shall be considered, but area of fillets shall not be counted.  The model must be colorfully painted and must have the AMA license numbers permanently affixed to the upper right-hand wing surface.

"6.16.1  CLASS 1/2A
a.  Minimum wingspan 14", 12"for a bi-plane.
b.  Minimum wing area 45 square inches.
c.  Minimum fuselage length 12".
d.  Must have clear canopy.
e.  Must have fixed landing gear, with minimum of two (2) wheels permanently attached.
f.  Profile models permitted, but only by Junior contestants, in either Junior-Only or combined age events.
g.  When 1/2A Proto is conducted as a Junior-only Profile event, then only two line control systems shall be allowed. 

**  CLCB CHAIRMAN INTERPRETATION:  The above categories in 1/2A Profile Proto now establish a record category for Junior 1/2A Profile Proto on 2 lines only and an unrestricted 1/2A Proto record for Junior-profile or not, 2 lines or 1 line.  The profile-only record can be established when a Junior is flying a 1/2A Profile Proto model in either a Profile Proto or the B Proto event, regardless of the age groupings of the contest."

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In Paragraph 6.2:  "Class 1/2A:  .000 - .050 cu. in. piston displacement of engine(s).
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1/2A Proto:  .000 - .050 cu. in. piston displacement of engine(s).

6.3  LENGTH OF CONTROL LINES .....  Class 1/2A models, 42 feet. 

6.4 SIZE AND CONSTRUCTION OF CONTROL LINES.  .... Class 1/2A  Minimum Diameter if two or more lines are used:  .008":  If one line, the minimum diameter is .014".

I hope this helps.

Comments:  Based on published designs and the Speed columns in the magazines, the 1/2A proto speed rules first appeared around 1964.  The minimum wing span requirement was 18", unless it was a scale model of a full size aircraft, then the minimum span was 14".  The minimum span requirement of 14" was changed sometime before the 1972 rules shown above.  I flew a 14" span "scale model" of the Spitfire Mk 22 at the 1970 Air Force Championships and at the 1970 Nats.

I Hope this helps.

Keith

Dale Kirn designed a number of 1/2A proto ships, I think he is the one who introduced the event. I check Outerzone but they only have the profile ones, maybe someone has one of the early mags that had his full cowled ship in it.

Best,   DennisT

Quote from: Dennis Toth on August 13, 2026, 02:41:06 PMDale Kirn designed a number of 1/2A proto ships, I think he is the one who introduced the event. I check Outerzone but they only have the profile ones, maybe someone has one of the early mags that had his full cowled ship in it.

Best,   DennisT

I think it is a safe thing to say that Dale Kirn generated the initial rules for 1/2 A Proto. His "Lil Pronto" was published in the Sep/Oct 64 issue of American modeler.  His article mentions that the AMA had been "studying the proposed 1/2A proto rules."  His Lil Pronto was built to those rules.  Really clean design.  Inverted engine, cowled in Cox TD, front of nose blended in with the standard Cox 1/2A prop nut of about 1/2" diameter. 20 inch span.

Keith

And lets not forget, fuel was unlimited.


MM

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