De Bolt Pylon Racer. Radio conrol pylon racer model for K&B .15R engine.
Quote: "Pylon Racer, by H deBolt.
Every article about a model design should be able to start out by saying Hey fellas! Here is a championship record holding design which will just suit you fine! I am sorry but I can not truthfully say that this time, not all of it at least. I can offer you a neat little simple multi design that meets the Pylon rules and does fly like a dream, interested?
This design was developed after watching many a Pylon race and having the resulting itch to try that one time. It is also an attempt to improve upon the performance of what appears to be the 'average' Pylon Racer seen to date. In watching many of the races it appeared to me that much time was being lost by the antics most of these models go through as they flew the course. Most of them seem to seem to hop and jump around the pylons like a fish out of water, it's hard to conceive that these models are truning in anywhere near their maximum speed. Like I said to begin with, this one which we have here has yet to set any records, perhaps no fault of its own as I have yet to get a clocking on it with a peaked engine and what would be the correct prop, etc. However, it does fly a very smooth pylon course and has the stability to keep it in the groove, matter of fact it is fun to fly rather than a chore!
The Racer has a few design features which should be of interest. Obiviously a fully cowled engine is used to lower drag. This comes from former control line experience and the fact that cowls used on some recent stunt models did show an increase of speed. It is planned to eventually go to a full pressure type cowl just as the C/L boys use, however on the first one we used a simple helmet type made from fiberglass. The reason for this was that we wished to play with several different types of engines, which is rather difficult to do if the cowl is tailored to one particular type. Actually after using these inverted cowled engines on several models now. I have come to like them. They seem to be the best possible way to hide an engine and do look neat of course. However, In addition they add utility as once the cowl is unbuttoned your engine compartment is really out in the open making things real easy to service.
Inverted engines usually scare people away because of the added troubles starting then. In this case the racing engine with its usual 'hot', plug has shown no problems along these lines. Another thought in this respect is to use the starting 'cradle' which we have been using with our stunt jobs. When this is used the model is laid into it upside down and then the engine is upright for starting; once running the model is simply turned over and set on its wheels. You might like this idea also if you happen to fly from a dirty field, it keeps your model up out of the grime most of the time.
To get the stability required for smooth flight we used a force arrangement similiar to what we have been using for stunt these days. This requires incidence in both the wing and the tail but fortunately the drag does not go up with the airfoil used until you go beyond the angles used here. It is felt that this arrangement should pay off. The airfoil used is a bit thicker than most of them which have been used in Pylon. The reason for this is apparent when you look at the airfoil charts..."
Quote: "My scan of the De Bolt Pylon Racer is also attached. This was a challenge as all was crumbly old newsprint. My technique is to use strips of doculam as bandages (also a great lightweight covering material) to hold the crumbly pieces together for scanning. The doculam can be moved around precisely before applying heat with an iron. Ordinary adhesive tape only allows one chance to get things correct, often with disastrous results."
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