D

drozovs

Member
Im curious if anyone has had any experience with open framed pressure recovery wheel pants?:

E_1_Wheel_Pant.jpg


Thanks in advance! :)
 
Last edited:
drozovs said:
Im curious if anyone has had any experience with open framed pressure recovery wheel pants?:
Click to expand...

That is not a pressure recovery shape. If it was, the original RV wheel pants would also have been called pressure recovery.

Pressure recovery will have a reversal (inside radius) in the body shape at the aft end.
 
rvbuilder2002 said:
reversal (inside radius) in the body shape at the aft end.
Click to expand...

Can you please clarify what you mean RV? Im not following what you mean by the reversal part... my understanding of the purpose of a pressure recovery device is to provide a shape/contour that mitigates the abruptness of a flat or non-aero form that would otherwise further drop the local area pressure.
 
I've seen these "spats" or whatever you call them on 180's and some old timey planes. Does anyone know if they actually do anything?
 
From everything I learned in my aero classes they should... I have a few questions on if the more progressive tear drop shape makes a "significant" difference or not. Im playing with the idea as I want something that gives me the aero performance without the negative down side of not being able to inspect my tire tread on pre and post flight... Thanks Aerhed!
 
Im less concerned about what it is called and more interested in if it works. I had a friend with an Ercoupe with pants like your photo. He said they increased his speed - but they are so slow anyway, it would take more than those pants to make much of a difference.

I like the looks of the wheels on planes but realize the pants make a huge difference in the RV designs. Drovos - thanks for the post.
 
I agree on the "what its called" vs "how it works" too :)!

I have a few feelers out to my aero-engineering buddies... Ill post anything I find out... Like Aerhed posted, Cessna tried them (briefly from what I understand), not sure if it was a effectiveness issue or the pain to structurally secure them from a single point as apposed to a "cage" design found on more traditional covers.
 
Ya...what they're called is not important. That said, having a reflex toward the rear of the pant is what "rv" was getting at.
It wouldn't be any more difficult to shape them this way and may be beneficial.
Also, it might be improved even more by installing a "bullet" in front of the tire.
 
Last edited:
spats

The spat configuration certainly offers the smallest frontal area.
IIRC, 80% of the drag is created on the downstream side of the object.
Difficult to integrate a gear leg intersection fairing...??
As a grass strip pilot, I see advantages.
Roger
 
RKellogg said:
The spat configuration certainly offers the smallest frontal area.
IIRC, 80% of the drag is created on the downstream side of the object.
Difficult to integrate a gear leg intersection fairing...??
As a grass strip pilot, I see advantages.
Roger
Click to expand...

No doubt. I've always liked the looks and simplicity, if they fall in the category; of these trailing type wheel pants. They definitely improve drag and I don't think the bulbous curvature of the leading edge of the tire is much different from a traditional wheel pant. The trailing edge/end of the tire is where the greater drag exists. Envision a rock in a river and the eddy that forms downstream on the backside of the rock. Depending on the speed of the flow, it can be quite turbulent and "hold" matter. If that same rock tapered gradually to a central point , the divided currents would return to normal with minimal disturbance.

Phew....I hope that makes sense. It's a Saturday night and I'm 4 ipa's deep right now. :D
 
I would be concerned with the gap required between the tire and the fairing to prevent mud, ice or stones from dragging on the tire.
A safe clearance would probably allow turbulent air to ruin the potential drag reduction of the fairing?
 
The difference between the original vans wheel pant and the so-called pressure recovery wheel pant is that the aft shape on the PC tailors the deceleration of the flow (and increase in static pressure, hence the term recovery) so that it occurs further forward, before the boundary layer thickens up, which will delay separation and reduce the wake, which is the big drag producer. Anything on the airplane that creates a wake, like a bubble canopy, or big gaps or wheels etc are the biggest sources of drag. The shape of the front of the wheel pant is irrelevant for the most part.

Tailoring this recovery requires a certain amount of finesse, so controlled conditions, attached flow etc. One has these conditions to some extent aft of a smooth wheel pant. I doubt they exist aft of a tire with a ridged tread and a wheel with a recessed hub and a brake disk and caliper, not to mention the gap for that fairing and its support structure. I would expect that flow to be very turbulent and any advantage of a pressure recovery design would likely be lost.

But I would expect that fairing, or spat, to have a drag reduction relative to a naked wheel, since it should reduce the wake aft of the wheel.
 
Wheel pants

Look pretty simple to make, Blue foam with glass or aluminum bent and riveted and a weekend or two.
Make a set and see what they do to your speeds .
 
Given what I've read in the archives

...I think RV-10 owners would be especially interested in trying this.

I know if I build a -10, this is one departure from the plans I might want to waste some time on, especially as she'd be based on a turf runway.

-Stormy
 
sonex293 said:
I was watching a program on Restoring a WW2 Westland Lysander STOL on a PBS program this past weekend.

http://www.ultimaterestorations.com/the-lysander/

An interesting airplane that I've never heard of before. They had an interesting Wheel Spat design.

Lysander_357.jpg~original


It's top speed was 212 MPH.

==
Michael
Click to expand...

Great pic and find Michael! I have a friend who flies the Lysander (we could start a new thread just talking about that aircraft :)! ) one thing to note is that the Lysander had a connective canvas that turned the spat into a traditional wheel pant by covering the gap. Due to the pain of having to build these by hand (they wear quickly), a "lot" of people opt to keep them off.

That said, the bow wave effect of the leading edge of the pant, or in this case for the tire itself, it may give you enough "displacement" around your critical parts so issues like clearance aren't as critical as originally though...

If I'm not mistaken, the bow wave effect is well illustrated on the Boeing 747 outer main wheel doors, if you look closely they are canted and not inline with the longitudinal access of the plane. From what I've been explained it has to do with the resultant local directional flow downstream of the other "things" (ie, nose, etc) that "push" it around.

I'm definitely going to be trying this on my -8. I have an idea to fair the disc and caliper and am thinking of a flat possible dimpled cover for the interior wheel hub. I'll make sure to post back here when I do!
 
I saw about 7 knots increase in speed for the same rpm on my fixed pitch prop by adding Van's pressure recovery wheel pants and pant intersection fairings over bare wheels. The old style non pressure recovery wheel pants reportedly yielded less improvement, maybe 3 or 4 knots. I suspect you will see something less than the 3 or 4 knot improvement with these "spats". So maybe one knot? Why not just go bare foot and forget pants altogether? The Van's series planes still perform great, even without wheel pants.
 
I agree with you Brad that it may not be a significant gain but the whole purpose of me wanting to build an RV is to answer those questions that I cant in a "Cessna" :)

I'm definitely going to research the original vans dealing though! Thank you!
 
inspection port on wheel pants???

Reading the string I was wondering if anyone have come up with a simple and easy to use access port or panel? The Lysander posts are interesting and along the line I' thinking, but doesn't look right for a VANs. I recently saw an advertisement for an a twist easy access wheel cover that allowed access to the valve stem, but it was on an otherwise uncovered tundra wheel. I hate not being able to easily check my tire pressure and wear....!

Please post your ideas.
 
You must log in or register to reply here.