Cooling issues Rotary vs. Radial

[hank jarrett]

I think you should be able to get away without the cowl gap if you can create two plenum's, one in front of the engine, and one between the engine and the firewall. You need to get all the air you can into the front plenum and NOT allow it to spill out the bottom (air will take the easiest route to low pressure and if the cowl bottom is open almost none will go through the fins). The plenum behind the engine and in front of the firewall needs to be sealed as well as possible with an exit to a low pressure area to draw the air from the front plenum, through the fins to the aft plenum and out the exit to the low pressure area. This is going to be much harder on a cowl like the DR-I and much easier on a cowl like on a Nieuport 28. If I was doing a Nie 28 I would probably "box plug" the holes in the bottom of the cowl (on a rotary they are used to prime the cylinders for starting so they aren't functional on a radial anyway) to keep the air from escaping there. I don't know how i would address the problems on an open bottom cowl, but then, I like the Nie 17 and it has a full cowl. ;-)
Hank

[Joe Perkel]

Originally Posted by Machinbird

cowl to ensure air exchange or otherwise, you will have cooling problems.
Sid

I had come to this conclusion some time ago myself. However, as Hank suggests, uneven cooling is not healthy either.

One potential option that I am considering, is a display cowl in addition to a flight cowl if this proves necessary.

As Johm M points out, seems to be something to figure out early in testing.