I’m making another departure from the plans… this time with the design of the bottom of the cowl. The plans call for a set of fixed louvers along the lowest part of the cowl to give exit air flow. This helps with cooling, both of the cylinder heads and the oil (as the cooler’s air dumps into this area as well). Most people say these work “OK”, but there are also a lot of reports of people having the level out their climbs to let the engine cool off during hot weather. Also, since the stock louvers are fixed, that cooling air is being sucked out whether you need it to or not. And all of that extra air is drag.
If you look at pretty much any high performance piston plane out there, they have cowl flaps. These do the same thing as the louvers, but they have the ability or being closed when they’re not needed… like when you’re in cruise. They also drop down into the airstream when they’re open, so they should also provide MORE cooling than the fixed louvers when they are needed.
The drawback is complexity, cost, and weight.
I’m going to give it a try anyways. I’m using a cowl flap kit from AntiSplat Aero. It takes a little fabrication to get things to fit, but I’m hoping it’ll be worth it!
After working on the cowl flaps for a bit, I decided to tackle the service bulletin for the 10’s nose gear. Basically, to strengthen things up, Van’s recommends builders to install a steel plate in the nose gear mount. It’s a quick install. I just had jack up the nose of the plane, pull the nose gear bolt, slide in the plate, and bolt it back up.