STI Farm Fox Build Log

[efwd]

Wow, the fiberglass looks like it is improved since I built. Brandon said they would. On my 912iS I am having to cover up stuff to keep the temps high enough. Wonder if you enlarge the holes, will you need to cover up stuff as well? I still have 1/2 of my oil cooler covered with aluminum tape and its 90 degrees outside. I never see oil temps over 250.

[Shadowrider]

Superfill works great for working the cowling smooth. Lots of on and off and a sharpie does wonders to help mark where you need to sand.

[yocum137]

Thanks Dustin and Jim.
If I went with the cut line it was going to deform the rest more I thought so having to rebuild the front anyway I opted for slightly larger air holes in the front. More air for a 915 I thought would me better??

Larger isn't necessarily better - you want to remove heat from the engine. A larger opening will slow the air down and won't transfer heat out of the engine into the air that's passing over the fins. The Tony Bingelis books talk about building cowls and lots of research has been done since the '30's. Of course, there are tons of resources at the EAA. This looks like a good starting point: https://www.eaa.org/eaa/aircraft-bui...allation-notes

[Shadowrider]

I agree. Most of the problems with the cooling on the 915 cowls or a Intercoolered turbo engine is all the vents put on the cowls over pressuring the cowl. Adding larger and more vents, nacas for intake and a Intercooler is is just dividing the amount of air the cowl can take amongst intake openings/vents in essence lower the amount of air the through the radiator and oil cooler naca. Opening up the exit air will allow more air through the cowl. I dropped the back of the cowl creating a larger cowl flap and increasing exit air volume capacity.

[yocum137]

But, didn't you end up running too cool and had to close off parts of the exit vent to get the temps up?

[Shadowrider]

Ha! Yes but too cool is better than to hot! Moving as much air through the cowl was my goal to help lower intake temps. The by product is it’s cooling the oil and water more than needed. Building again I may go smaller oil cooler? Kitfox solution of extended the bottom lip is a good solution to those I have talked to. I made a louver to control oil temps and just installed a thermostat to control water temps. Winter flying the water temps are too cool to keep me warm.

[Kitfox Pilot]

Wow, the fiberglass looks like it is improved since I built. Brandon said they would. On my 912iS I am having to cover up stuff to keep the temps high enough. Wonder if you enlarge the holes, will you need to cover up stuff as well? I still have 1/2 of my oil cooler covered with aluminum tape and its 90 degrees outside. I never see oil temps over 250.

I hope thats a problem but I hear the 915s are warm blooded....

[Kitfox Pilot]

Larger isn't necessarily better - you want to remove heat from the engine. A larger opening will slow the air down and won't transfer heat out of the engine into the air that's passing over the fins. The Tony Bingelis books talk about building cowls and lots of research has been done since the '30's. Of course, there are tons of resources at the EAA. This looks like a good starting point: https://www.eaa.org/eaa/aircraft-bui...allation-notes

I won't have any problems closing the holes back down if need be. I'm only gaining 1/2 to 3/4 inch in length.

[Kitfox Pilot]

I Used a med gloss black on the lift struts and glad I didn't use the high gloss. Got them back on the plane hopefully for good!

When I flew with Steve last winter out in Arizona, his lift strut fairings are the best I've ever seen. I tried Steve but they are not as nice as yours. haha

[efwd]

Looking great Harlan. I visited Steve and even helped hold his fiberglass fairings while he sanded the trailing edges smooth and straight during his build. He has a lot of time and effort invested in those.