I am looking for advice in cutting cowl flaps into a Top Flite F4U Corsair .60. I have seen this done but haven't figured out how to do it just yet. Marking and cutting the flaps in the base cowl ring isn't the big problem. The problem comes with opening the vents. What is the best way to bend them out, so that they are "open"? I am hoping to gain enough exit venting to avoid cutting a hole in the bottom of the forward cowl. (I know the rule of thumb is twice the exit volume as the intake volume). If anyone has done this or has a good idea as how to do it, I would appreciate some help.

JAGMI
AMA 710081

Here's what I did; At the front of the fuse, where the base cowl ring mounts, I cut about a 5/16"- 3/8" smaller diameter circle from the fire wall. Leave the fire wall original size where the four screw mounts are located. Notch out the sheeting in these undercut areas towards the rear of the fuse about 2 1/8- 2 1/4". Resheet the fuse in these areas. You'll end up with slots that taper and when finished aren't that bad looking. Seal off completely front of cowl. Cut a 1" slot from crankshaft, in front of carb, to edge of cowling in the front sealing material. Should give you 3 to 1 ratio. Worked in mine with a OS61 FS. You might have to fine tune for your application. Hope this didn't confuse you.

GPaloz,

Thanks for the suggestion on opening up the cowl on the Corsair. Unfortunately I have already built and covered the nose of the plane. I am thinking that a plan B will be necessary. I have seen the cowl ring with vents cut in and bent outward forming an open flap. I suspect that heat was somehow involved. I am just uncertain as to the best way to go about it.

JAG

I used an aftermarket fiberglass cowl that already had the open cowl flaps formed. The only modification was to build up blocks on the firewall to mount the cowl to.
Precision Fiberglass
Louisville, TN
423-984-0828

Just take a torch and indirectly warm the area of the ring you want to bend. Slight heat and patience with each of the 8 to 10 flaps should give you a nice looking cowl ring.
Just warm it, gently pull it open to a realistic angle and repeat from flap to flap.
It's a great system, just don't melt the plastic so much that you lose too much material to keep it attached to the ring.

good luck.
jw

What is the best way to cut the cowl base ring to make the individual cowl flaps?

I used a dremel cutting wheel and followed a straight edge working from the top of the ring out...(toward the fuse end of the ring).
It's easier than trying a knife to get through the plastic and it's not too difficult to control.

Just go slowly and wear eye protection, that cutting wheel will break at least 2 or 3 times before you have them all done.

Another way is to use an xacto saw fitted to a large handle.