Basically, I want to retain good looks and get good cooling at the same time. See photos. I want to know if I cut on the marked lines, is there a way to "soften up" the fiberglass enough on the fourth imaginary line to get it to bend out and form cooling slats? Is this even possible??? Thanks in advance.[sm=confused.gif]

It is possible, but it won't last. Better bet is to make the cooling slats up and then fit to the cowl.

Cheers.

Do you mean fabricate separate pieces and then attach them?

If you have no exit air on the bottom of the cowl then those slats are no where near adaquate and you are going to over heat. You need roughly twice the exit area as the inlet.

I do have a decent opening on the bottom of the cowl, but it doesn't look like its twice that of the intake. Just trying to get something functional and good-looking.

Good just wanted to point that out. If you think the outlet area is a little small then it would be more effective cooling wise to just open the bottom up some and not vent the sides of the cowl. This way you have what is called a pressure cowl but venting the sides would tend to slow down the flow through. This has the added advantage of by just opening the bottom a bit is far more attractive than the vents.

Doing vents the way you described is likely to come out looking real ugly and even hinder the cooling, let the air out at the bottom rear if needed.

John

Sounds good. I guess its a compromise, but I'd rather have a larger hole on the bottom that to take a chance with my *ahem* fiberglass skills- this RV-6 is too nice of a plane. Thanks![sm=RAINFRO.gif]

I have been told rule of thumb is inlet area = W x H of your fin area on the head. Outlet area = W x H x 140%.

Consideration should be given to ducting of air inside the cowl for smooth passage of air around the head and out the outlet.

The inlet holes on the front of the cowl are probably adequate, just make the exit on the bottom a little larger than the combined area of the inlets. There are some allowances that have to be made, even in fine scale. The bottom opening is not readily apparent, but it's expected to be there, and the airflow will be across the engine that way. The side vents might look good, but the thin fiberglass of these cowls will only crack between the vents in a fairly short time from vibration and handling.

I think It could be pointed out that most of the time the inlet holes are much larger than nessessary and therefore the outlet holes can be smaller[ Twice the size of what is needed for the inlet] rather than twice the size of the inlets ussually cut in the front of the cowl.If you had to have twice the size of the inlet for outlet holes you would be cutting the whole bottom of the cowl out. I notice in many construction pics the holes in the bulkhead behind the cowl is much smaller than the holes in the cowl itself

The outlet(s) should always be bigger than the inlet(s) the airflow will tend to get trapped otherwise and will not pull the heated air out.

Do you have any baffles in the cowl?