Subject: [FlyRotary] Re: New Scoop

 

Al,

I don't know exactly how to phrase this question but I'll take a stab at it.

When you decided to place the heat exchangers in the wings how did you estimate

the effect(if any) due to impact on the designed airfoil(s)? I think this is a

great place for them in the canard designs. I am thinking about the spaces in

the rear of the strakes for mine.

Dean Head

Cozy MK4

BKV FL

 

Dean;

 

You probably phrased the question better than I can phrase the answer.

 

Actually; I wasn’t very concerned about airfoil effects because on the canards the strake is not a very effective lifting surface because of the very high Reynold’s number.  It is designed for neutral angle of attack at cruise, with essentially all the lift provided by the canard and wings.  There is some pressure differential between upper and lower surface (based on aerodynamic analysis) in the wing rot behind the strake which can help the flow through the coolers, and the difference is greater at higher angles of attack, when you need the flow the most. I pushed my strake tops up a bit during installation increase the effect, as well as give me a bit more fuel capacity.  I guessed – no; ah-h, applied my engineering judgement – that the amount of flow through the cooler would not significantly impact the lift.

 

I designed the exit faring like the upper half of an airfoil to retain attached flow to minimize the turbulence generated behind the faring.

 

I really don’t know yet how well it is going to work.  Is that why they call these “experimental aircraft”?  The only data point we have is Alan Shaw’s oil cooler installation, which apparently worked well even though his approach to the airflow was not as; let’s say, “sophisticated” as mine.

 

Al