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Airflow under a cowling

What is the downside to using butyl tape to seal the baffles against the engine?

Forever learning
EGTB

I have just read in KITPLANES Sep 2016 (a homebuilder mag) that “cooling drag can be 20-30% of overall drag on a certified aircraft” which is astonishing.

At cruise speed that is worth tens of HP.

I am surprised there isn’t a nice business in STCd cowling kits which do a better job in getting the air via smaller holes and channeling it to the engine better.

Administrator
Shoreham EGKA, United Kingdom

I remember reading about a guy called Art Mattson in the US. He modded his Cherokee -140 to fly at 173 mph. I am not sure if he is still around and it seems to be hard to find any good info on what he did but I recall that I saw a picture of a very non-standard cowling that I guess contributed a lot.

Sweden, Sweden

In the homebuilt world this is a huge topic. There are a number of 3rd party cowlings available for RVs – for example the James cowl

Also, since flying the first RV-14 prototype, Van’s aircraft have publicly said that the cooling works so well they may reduce the area and associated drag in future models.

In the certified world, Mooneys have had all sorts of cowl mods for years and Cessna and Piper mods are available as well – eg here.

EGEO

Peter wrote:

I am surprised there isn’t a nice business in STCd cowling kits which do a better job in getting the air via smaller holes and channeling it to the engine better.

There is, it is called LoPresti Aviation.

I have seen these firms but never seen anybody with the product.

Administrator
Shoreham EGKA, United Kingdom

Lo Presti are very big. Fairings etc. Not sure they do cowlings. There was word a few years ago about someone planning a new cowling for the Meridian to give 10-15 knots.

EGTK Oxford

LoPresti do cowlings, too. I know about Mooney, Piper Arrow and Grumman Tiger, maybe more.

LKBU (near Prague), Czech Republic

What I don’t understand is that if a cowling makes so much difference, there would be a huge value in an STCd improved one.

So maybe it is not as simple. One needs to have adequate cooling during climb, for example.

Administrator
Shoreham EGKA, United Kingdom

Well, Piper must have thought the LoPresti cowlings for the PA28 series were good, as they made them the factory standard fit items for the Archer and Arrow from 1994, I believe.

EGTT, The London FIR
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