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Al Gietzen wrote:
The most detailed, sophisticated analysis of radiators for our application
that I have seem was done by Fred Moreno back in 99; but unfortunately it
also was done for a specific case of 220 KTAS and 10 fins/in. What it
suggests is there is an optimum thickness (minimum drag), and that is
roughly 3. Thats for 10 fins/in.; I concluded that my 16 fins/in rad
should be thinner, and went with 2.5 thckness. It works exceptionally
well. The 2.5 to 3 thickness seems common for rads made by Ron Davis and
Griffin for racing applications. That seems consistent.
Was that straight, waved, or lanced fins? I just don't want anyone make generalities from a single data point 8*)
On a serious note, this makes a BIG difference. Straight fins offer the least resistance to the air, but the waved fins will transfer more heat per unit volume. The lanced fins (fins with lots of holes) are as efficient as the wave, but has no more backpressure than the straight.
My main radiator is about 3.5". I'm not flying it yet, but I had room to make a textbook streamlined duct. I reasoned that with more efficient pressure recovery, I should be able to use a thick core, and I made sure that it had lanced fins.
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