A friend started to build a small recreational helicopter with a Coanda effect tail.  The craft was about half built when he stopped two years ago and went on to another rotorcraft project.  He says that he may go back and finish the project in the future, but he is having doubts about the efficiency of using Coanda, particularly in a very small and lightly powered helicopter.

Hope this is of help.

This helicopter is going to be small too.  Single seat.  To provide yaw control there will be a nozzle to direct air in the required direction.  What I was wondering is if it would be more efficient to direct the airflow at right angle to the tail boom at the end or to use the airflow, exiting through slots, to cause the coanda effect.  The individual configuration obviously has an effect but I am having difficults finding information on calculating the coanda effect.

cheers
Gyronaut

Just a suggestion, but why not just use a large swivelling aerofoil section? Isn't this all the coanda effect really does anyway? I notice the original VS300 had a tail boom aerofoil. Interested to know if this would provide enough force...

Mart

The problem with a large swiveling aerofoil is mainly a structural one as to mount it, like a canterlevered beam and make it swivel with out to much friction is difficult. A fixed aerofoil with a flap/aileron type control surface has potential.  Another consideration is the effect of a cross wind.  This is the advantage of the coanda effect, less side area and simple structure.  

Gyronaut

Thanks Gyronaut, sounds like you have thought this through very carefully. I can see that the coanda effect would allow a very light solution. Maybe incorperate the flap aileron control at an angle, so that it also doubles up as a "rudder" for fast forward flight - might get round the crosswind problem...

If you wanted to try out a number of alternatives maybe talk to the aerodynamics boys at MIRA Ltd. I don't work there anymore, but they did some pretty varied an interesting work - all with the strictest of security, for a number of global clients. Based in Warwickshire England, tel: +44 (0)24 7635 5000.

I wish you luck with your project - sounds interesting. Is it anything that can be openly discussed?

Mart

Hi Gyronaut,
There is another interesting aplication of Coanda effect studied for a long time by NASA:
 Circulation control airfoil
You can check the "SPORT AVIATION" magazine from 28 March 1988 for DOUG GARNER's article; it seems to have the formulas you need!
I hope this is of help.
Regards

if you need details about the Coanda effect, try to access the Aircraft Faculty of the Technical University in Bucharest. Professor Constantinescu might help you find answers to your questions.