How I did my ram-air intake, results

[scsmith]

Originally Posted by Cumulo

Well, a bellmouth, a funnel, whatever, may give you more rain, more bugs, more dirt, but not a bit more pressure. Not fair is it? Not intuitive either.

BTW, I am a Free Diffusion advocate. It is ~100% efficient. This translates into large, well faired intakes.

I meant a bell mouth for testing on the flow bench. Certainly not on the airplane.

[F1Boss]

I might be seeing things wrong, but the inlets I have (THANKS DAN!) sure look like the LE of a Cub or Champ airfoil, like nose 1. Nose B and C resemble the LE of the RV wing...fairly simple to fab up a mold for any of those.

Of course our inlets will NOT have the afterbody like the round engine cowls do...a lot more expanding on our setups except on the upper sfc.

Dan: why is your air inlet for the engine so different from the cooling inlets? Seem you'd want the same recovery value for both? I must be missing something...

[scsmith]

Originally Posted by Larry DeCamp

1/8” radius ? 1/4” ? More? I am ready to act with sandpaper in hand !

Hi Larry,

Mine is about 5/16 radius, and I think it is definitely overkill.

In Dan's picture, it looks like a bit under 1/8" but hard to say with the lighting.

I guess I would recommend at least 3/16" radius, with continued thickening so that if you go back 1/2" from the lip, it is at least 1/2" "thick" (distance through duct from inner wall to outer wall. As if it was a 1/4" radius, but not circular, more elliptical.

Hope that helps.

[cajunwings]

This is so timely, I?m working on the inlet lip now. So far I?ve used a short piece of 1/2? pvc (cut in half lengthways) with sandpaper cupped on the inside to create that half round shape. By more ?elliptical shape? do you mean instead of a perfect 1/2 circle it would be just a little pointed at the apex? A simple sketch of the cross section would be great.

Don Broussard
RV9 Rebuild in Progress
57 Pacer

[DanH]

Originally Posted by F1Boss

Dan: why is your air inlet for the engine so different from the cooling inlets? Seem you'd want the same recovery value for both? I must be missing something...

In terms of pressure recovery, it works just fine. It is a low Vi/Vo type, like the cooling inlets....a 4" ring

I built that inlet many moons ago, with an eye on style. It may be separating externally, aft of the lip when spillage is at max, causing some external drag. Some tufts and a GoPro could be in my future

[DanH]

Originally Posted by Larry DeCamp

1/8” radius ? 1/4” ? More? I am ready to act with sandpaper in hand !

I forgot about the profiles in CR3405, identified as Kuchemann A-series. They are much as Steve describes in post 23. Start at page 38.

The reference is Aerodynamics of Propulsion, Kuchemann and Weber. Out of print and not cheap as a used book. Anyone have a copy? Worth having?

[tcone1]

Originally Posted by DanH

Airbox #1 was lovely, but in retrospect was dumb as a bag of hammers.

Help me understand why your first airbox was dumb? Just not enough filter area? Not enough divergence in the box?

Use small words, I'm just a dumb pilot.

[DanH]

Originally Posted by tcone1

Help me understand why your first airbox was dumb? Just not enough filter area? Not enough divergence in the box?

Use small words, I'm just a dumb pilot.

Not enough filter area.

[Onewinglo]

Originally Posted by DanH

Not enough filter area.

Now that's just funny!