Understanding SAM

S.A.M. The Society of Antique Modelers came into being some thirty years ago. Now with worldwide chapters, it was formed by those who had a special appreciation of the early models that paved the way to the technically advanced machines available today.

So, what is so special about Old Timers, you may ask. Speaking for myself, they fulfilled a need that current models are unable to supply. Because these early machines were nearly all freeflight models, they had flight characteristics that included stable and graceful flight. They actually FLEW on the wing, in contrast to being dragged along by brute force combined with the necessary speed required to produce the lift needed.
Quite simply, I was a little bored flying back and forth and wanted something different.

The essence of all Old Timer flying, is a soaring competition, where the last man down wins. And soaring is what these models do very well indeed. Strictly speaking, “Old Timer” refers to models designed from
1939 to 1942. Earlier models are categorized as “Antique,” and the models from 1943 to the end of 1956 are “Nostalgia” models.

Within these broad groupings lie many sub groupings which each have their own competitive
events and rules. Before one can soar, he must get the airplane to altitude. This is done by engines
limited in one of two ways:
a) The fuel is limited according to the weight of the aircraft. These are known as “Texaco” events.
b) The engine run is limited to a time. (as short as 20 seconds but antique engines - pre December 1950 - get considerably more depending on their age and size.) These are known as “Duration” events.
How long will a modern model weighing 5lbs (2.25kg) stay up on the 15ml (½ oz.) of fuel allowed that weight in Texaco? An old timer expected to stay airborne for 10 minutes on this, but if one finds lift, times can run into hours.

Alternatively, with a limited 25 second engine run, how long will a modern R/C stay in the air? Old Timers expect to reach 7 minutes in the elimination rounds, and in any fly-off, hope to stay up until every one
else is down.

“Antique” is a limited engine run for old cabin or cabane style models (no pylons). National rules permit no scaling, and engines must be antique, which limits them to diesel or spark ignition. Larger models invariably use the larger spark ignition motors while the smaller diesels are limited to smaller models.

Texaco events need to conserve fuel, and engine management is important. One wants to keep the engine running as long as possible, at the same time produce enough power to get to the highest possible altitude. Propeller choice is a trade off between large efficient low power, and smaller less efficient higher power. Engines need to be run as lean as possible, yet avoid starvation later in the run. All this makes Texaco a relatively quiet peaceful event.

Duration events are another matter. Here time is the limit, not fuel, and one needs all the power one can muster for a rocket-like vertical climb that can reach a mile high in a minute. Racing motors are common in open duration competitions. 25 seconds is the time allowed, and since it takes two seconds for sound to travel from the aircraft at height, one must shut down at 23 seconds to avoid a disqualifying over-run.
At this point the model transitions from a screaming rocket to a nearly motionless glider, and the hunt for thermals begins.

This covers the basics of SAM events, and I hope it raises some interest among modelers. One negative is that the flying field must not be height restricted, as a lot of flying is above one kilometer altitude.
I have a sample on YouTube: http://www.youtube.com/watch?v=o4JSpF7Gzdc

Arnold, Broese-van-Groenou August 2009