Thorp Air Command - T18.net

What type of cowl do I have? It has two cheek cowl that are removable. It requires complete removal of the right side to check the oil. Seems to me, my cowl would produce more drag than others I have seen. Any suggestions on where to purchase the most common cowl for the T18. Aircraft Spruce has one for the S18 but that won't fit mine.

Robb777,

So far you have described the most common (& the best, in my opinion) cowl. I'm talking about the one designed by John Thorp, and it is actually very efficient aerodynamically. Can you post a picture so that we can tell for sure?

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

I face the same dilemma;
I have the same removable side cheeks. I don't mind having them, and they are easy enough to remove to check the oil prior to flight. But my ancient fiberglass is getting kind of rubbery, and has lost a few bits around the fasteners. I've had to do some repair work, now I'm considering replacement parts. That means upgrades are possible at reasonable cost.
There is a 'Comanche' style nose bowl that looks attractive. It does not use the separate side cheeks. I 'think' it would have less drag, based on the idea that any 90 degree element (the cheeks) sticking out of the main body is a drag. Hopefully the side panels can be lifted like an old car hood to access the engine for preflight inspection.
Maybe one of the more experienced hands could give us some detailed help on cowls.
I also have the hook shaped air inlet scoop.
That thing is Bu** ugly, and is mounted crooked on my ship to boot! I'm told that VANs Filtered Air Box for and RV-6 is a very good upgrade, and pictures of these on a T-18 do look good.
OOPS! I see jrevens says we have a very good cowl!

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Scott Emery
EAA Chapter 326
T-18 N18TE

For me, it is the best of what was available commercially for the T-18 when I started building mine in the '70s, & that is still the case today. Is it the very best that could be designed? Of course not, but it's a pretty good one. I do like to be able to expose a whole side of the engine in less than a minute... It makes for a much more thorough pre-flight than the average aircraft engine gets, & servicing the engine is easy. The way that Rich Brazell made his sides so that they hinge up is very cool. You can always add an oil dipstick access door if you want to, but I've never had a desire or need for that.
I wonder if Cubes has the Thorp cowls for sale?

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

The JT cowl has some clever characteristics that many folks miss on first glance. The inlet/exit ratio is critcle to good cooling; JT was a cooling guru in his time. The front face of a properly built side cheek is not 90 degres, but slopes from top to bottom. In a climb, the face opens up due angle of attack for more ram air. In cruise, it effectively shuts down a bit. Automtic cowl flaps, if you will. Of course, the side vents are great because they energize the air over the fuselage that is disturbed in the propwash. All in all, IMHO, the Thorp designed cowl is best for this plane.

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Bob Highley
N711SH
SN 835
KLAL

Here is the cowl with an oil access door included...works excellent and I'm very happy with the easy access to the engine.

All the above parts are for sale on the Thorp Central website. Just had a complete cowl made for Terry Hagel. It is strong and well built. I also have three different intakes available....the original, one that is close to the original, but not offset down, and a small round fuel injection one. I'll get pics done as soon as I can.
Cubes

Cowl pieces can be fiber glassed together then cur in half so that the top can be removed easily, and an oil door can be cut in. Looks good and works well

Can you still get to your bottom plugs for servicing without pulling the bottom half?

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Thank you for the information. I think I will stay with what I have and maybe do a few repairs. The cowl is cracking a bit here and there so maybe after repair and repaint it will look good as new.


Rob

No john, but, I have delt with both the cowl cheeks and my half cowl set up, its easier to take my top off and only slightly more time consuming to take it all off. And how many times are the plugs serviced in a year, and it's looks much cleaner and over all a little stiffer .

Lance
38DT

Thanks, Lance. It's an interesting idea... I don't think I've ever seen it done like that with the Thorp cowl before.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE