Inlet size differnece

[RVG8tor]

I have fit my cowling and the last set of hinges are curing with the epoxy. I had the plane outside last weekend since it was so nice, and this is the first time I had the room to stand back and take a look at the cowl, I have been working in the garage. I have what up to now I think is a good cowl fit.

But it seems in my fitting, my left inlet is slightly smaller than the right inlet. From what I can see from other pictures I have from various airshows I have attended they should be the same size (RV-8A).

So the big question: is the size of the inlets at a tolerance level that I will have cooling and or cooling drag issues? The vertical measurement of the center of the inlet is just under a 1/4" smaller on the left than the right. the smaller opening unfortunately is also the side the oil cooler will sit!

Thanks for any inputs.

Cheers

[Bob Axsom]

Reducing the inlet size will increase the CHT. I started out with 1/4" thick slices added to the inboard side of the opening on our RV-6A looking for speed. The inside of my stock Van's cowl is made into a one of a kind configuration with a lot of baffling in the lower cowl and the engine is a O-360-A1A with a Hartzell BA C/S prop so there will be differences. I took the inlet plugs all the way up to 1.5" blocking the inboard side of each inlet. There was no speed increase (just the opposite as I recall) but there was an incremental increase in CHT as I stepped up through the width of the plugs. With a slight difference in size I don't believe you will experience a performance difference.

The difference in size may be due to the thrust line offset controlled by the engine mount inside a cowl that is designed to follow the fuselage mold line rather than cocked to point precisely along the thrust line. If this is true, it will be the left inlet that is larger.

Bob Axsom

[DanH]

Mike, my notes regarding stock inlet area suggest the difference between the two inlets is now about 6.5%. We don't have any way of knowing if your small inlet is normal and the big one is oversize, or the opposite. Even if the small one is undersize I doubt 6% (3% overall) will make much difference in cooling.

That said, now is the time to fix it if you don't like it.

[Kevin Horton]

This size difference should have minimal effect, as the area above the engine will allow the pressures to equalize on the left and right sides. This is a cosmetic issue only, in my opinion. If you see anyone with a ruler in front of your cowling, distract them with a hard left-wing political comment. That'll get them so fired up that they'll forget all about measuring your inlets.

[RV8RIVETER]

As been said before, your difference is only a cosmetic issue. With the stock set-up you will pushing some air out one of the inlets anyway.

[RVG8tor]

Kevin I really like your idea. Maybe some mirrored inlet covers will be enough of a distraction. It was sort of a let down to get the fit that I have then to see the difference. Oh well, I guess this will give my plane some character!

Last set of hinges get riveted in a couple days.

[Veetail88]

Just paint it orange with white stripes and name it Nemo!

Seriously though, I noticed a pretty big heigh opening in mine and corrected that early in the fitting process. Just wished I'd left a larger gap at the prop spinner. I have to cut off 3/8" at my firewall and completely refit there. I guess the process just takes quite a bit of massaging.

And Kevin, I'm a right wing nut job and I'd never measure someone's inlet's! I'd likely notice it though!

[rv7boy]

Just tell 'em you designed it that way. And if they ask why, tell 'em "It's proprietary." then just stare at 'em with a Clint Eastwood squint.