Round cowl vs. Fast cowl

[shortfielder]

I am assuming that builders get the round cowl because of the nostalgic look. And the fast cowl to get a little better aerodynamics.
How much difference does the fast cowl make over the round cowl in max. cruise speed?
Are there other pros and cons for each of the cowls, say on a model 4 and/or Model 5 using Rotax 912ULS.
I tried searching this, but didn't find anything.

Thanks Gary

[SkyPirate]

aside from putting a barn door behind the prop ,..I don't think their would be much difference at all ,..the initial nose section of any sub sonic design with a prop stuck in the middle of it basically smooth's out the prop washed turbulant air,..as for the cowl , that's a different story..just think ventury effect,
the difference between the round nose and the smooth nose besides nostalgia,..the inlets on the smooth cowl direct the incoming air dirrectly at the cylinder heads,..the round cowl just catches air and if your using an aircooled engine you would have to make plenums to direct the air to go around the cylinders,..being that most of the round cowled aircraft are using the rotax water cooled engines a plenum isn't really needed as much as for an engine that is air cooled only,..
but ,..I could be wrong in my thinking too

Chase

[shortfielder]

Personally, at this point, I prefer the looks of the fast cowl. Most of these planes seem to have the round one.

What would it cost you to convert, roughly.

Is it a direct bolt on replacement.

I can do the painting.

Could it be a simple as buying the cowl, fitting it, painting, putting it on.???

What would a used round cowl in good shape be worth?

Thanks again Gary, Seems like I got a lot of questions, I appreciate
your help/patience.

[DesertFox4]

Gary, Personally I've not seen much if any difference between either at cruise. I've had both and find no real cons between the two. More a personal preference or mandated by choice of engine. I love the looks of both styles. It's called a smooth cowl and round or bump cowl to help in your searchs.

[jdmcbean]

Guess I wasn't communicating well. Not much difference between them.. not sure one would be a speed advantage over the other mever really tested them.
I will say that the installation of the smooth cowling is much simpler.

[shortfielder]

Thanks John
I got the point.
If one has the round cowl, how big of a deal is it to change it to the smooth cowl?
Gary

[shortfielder]

What plane is this? http://www.kitfoxaircraft.com/images/Gallery/KA%20Gallery%2000017.JPG

[jdmcbean]

Sorry.. I did not differentiate the models.. The Model 4 is very different than the Series 5, 6 and 7 models.

To answer.... it is a different firewall forward not just different cowlings. There are different mounts and firewalls as well.

[jdmcbean]

Kitfox Series 7