ENGINE TIPS

3) Cooling
This a tough one and it's impossible to be specific here but there are some principles to keep in mind for cowled models.
  • _Remember that where the air is travelling at a higher speed then it will have a lower pressure and that air will travel from the area of higher pressure to an area of lower pressure. If you cut scoops in the side of a cowl at the widest point hoping to scoop air in to the back of the engine then you may well be disappointed as this is a point where the air is travelling faster than elsewhere on the model and will be at a lower pressure, even if the scoops are pointing forward the air will probably be pushed out not in, you need fancy ducting from the front to introduce extra air to the back of the engine.
  • The cooling air outlet must be bigger than the inlet, I have heard figures quoted from 1.5 times to 3 times bigger, I don't know what the ideal figure is but you have to let that hot air out for the cooling to work effectively.
_
  • The air passing through the inside of the cowl contributes to the drag of the model so be just as careful to make the ducting smooth and free flowing as you do the outside of your model, in any case you will get more cooling air through. It seems that over cooling is unlikely unless you are flying at speeds over 200kph or have an integral finned AAC engine.

  • Click to view cooling system pictures