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Old 10-02-2017, 08:07 AM
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Mr Cox
 
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This is were the fine tuning begins, so it is very hard to give precis answers.
I have used both the regular and the hotter Nelson plugs, and I think the hotter ones throttle a little better but not as quite as well as a hot turbo plug (OS P4 as an example). For full throttle, and all out power, the regular Nelsons are fine and pretty hard to beat.

The optimum number of head shims depends on the fuel (oil and nitro content), prop size and the individual engine. I prefer to start from an extra head shim or two and then work down from there, remove a shim and compare needle setting and rpm numbers and overall handling. This is safer than starting with too few head shims which can overheat the engine. Remember also that an engine that is less sensitive to the needle setting will often perform better in the air, compared to an engine that you can just about tweak the needle for on the ground for a few extra rpm.

If you are serious about 1/2A flying you will soon acquire a respectable collection of engines, heads and heads shims, plus a number of suitable props. It is just a natural part of the hobby.