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closing Wheel pant gap to the tire

Bavafa

Well Known Member
Just wondering has any one tried to cover the gap between the wheel pant and tire with some material like silicon baffle or other type. Would the added weight and trouble outweigh the drag caused by the gap? Any thoughts/suggestions?

Mehrdad
RV7A - IO360M1B
 
I have been thinking about this also. Not only to reduce drag, but also to keep dirt out of the wheelpants. I would not use baffle material but do it with a brush (like used under doors, with longer hairs).

At the moment I am not considdering it because to many planes have flipped. Some of these flips may have been caused due to too small tire/wheelpant gaps and low tirepressure. Closing the gap this way, may make things worse!

Be carefull!

Regards, Tonny.
 
Van did this several years ago and wrote it up in the RVator. I don't remember the details, but they were not encouraged by the results.
 
I made subfairings

My subfairings extend down to 3/4" to 1" above the ground and come right up to the tire. I found no significant difference with the MLG pressure recovery pants but the difference with the older flatsided NLG fairing was surprising - on the order of 3 kts. I have raced with them for a couple of seasons and they are very effective - they caused no problems either. The information and photos should be in the forum files.

Bob Axsom
 
My subfairings extend down to 3/4" to 1" above the ground and come right up to the tire. I found no significant difference with the MLG pressure recovery pants but the difference with the older flatsided NLG fairing was surprising - on the order of 3 kts. I have raced with them for a couple of seasons and they are very effective - they caused no problems either. The information and photos should be in the forum files.

Bob Axsom

Here is the thread with pictures.
http://www.vansairforce.com/community/showthread.php?t=29326&highlight=subfairings
 
Here's a photo of the whole plane with the subfairings

Here's a photo of the whole plane with the subfairings installed for the race at Taylor, Texas:

IMG_3511.jpg


If you get into this kind of mod and study it, there are some interesting things you will see in the process. The swell point of the tires is above the edge of the fairings when they are brought down low so when there is weight on the wheels the tire is pushed up into the fairing cavity and the gap is increased but when the weight comes off of the wheels the tires extend downward and minimize the gap. Also all edges of the fairing do not have the same friction potential with the tires because of the direction of rotation and relative motion.

Bob Axsom
 
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Something a little more flexible?

Just wondering has any one tried to cover the gap between the wheel pant and tire with some material like silicon baffle or other type. Would the added weight and trouble outweigh the drag caused by the gap? Any thoughts/suggestions?

Mehrdad
RV7A - IO360M1B

Years ago an A&P friend of mine suggested I look for bristle brush material attached to a long flexible strip that could be formed around the inside opening of the fairing. His thought was that if trimmed to just "brush" the tire it would prevent air from burbing inside the fairing and potentially reduce drag.
 
On my old airplane, the pants were trimmed very tight and sat extra low around the wheels. That experience taught me that large gaps are preferable for normal flying. My wheels pants always took a beating in the grass and trapped snow in the winter. The wheels and brakes built up a little more heat, etc. In the end, you probably won't notice a difference in speed... but I promise you will notice if your brakes are clogged with snow or the tire blows.

For racing, I like the idea of removable lower fairings. You can get a little edge during a race... with the option to remove them for normal flying. If you are determined to seal around the tire, I recommend trying some heavy-duty felt-like materials. I've had good luck sealing other aerodynamic problems with felt. I think this will stop more airflow than brissles.

Of course... there is always the Bede-style wheel pants that Lopresti is now making.
 
Straight trim of standard fairings close to tires?

Straight trim of standard fairings close to tires? That's a bad idea. The right thing is to take a different slant so the fairing is more tangent to the tire than perpendicular and well below the point of maximum sideward deformation of the tire when weight is on the wheel. If the forward part of the fairing is made properly with sufficient layers the nose gear fairing serves as a deflection plate against nose gear dig in and flip over. Also material with higher coefficient of friction should not be stuck between the fairing and the tire.

Bob Axsom
 
Anyone remember the "close-able" wheel pants that Jim Bede designed many years ago? They had doors on each side that slid down to completely enclose the tires after take-off. Of course, you had to remember to open them for landing or be prepared for more fiberglass work.
 
Hmmm!

Anyone remember the "close-able" wheel pants that Jim Bede designed many years ago? They had doors on each side that slid down to completely enclose the tires after take-off. Of course, you had to remember to open them for landing or be prepared for more fiberglass work.

Mel! I like it...alot! It seems that one could design a simple "clamshell" type door that would open far enough to allow plenty of clearance during takeoff and landing, but would completely enclose the tire once airborne.
 
Lopresti

Google Lopresti wheel pants and look at the avweb article. A bit pricey at $1995 projected price.
 
Brakes get way too hot already

I am thinking about opening up or ventilating the main gear fairings --- my brakes get way too hot with the very gentle use and don't cool very well between TO/LDG.
 
Years ago an A&P friend of mine suggested I look for bristle brush material attached to a long flexible strip that could be formed around the inside opening of the fairing. His thought was that if trimmed to just "brush" the tire it would prevent air from burbing inside the fairing and potentially reduce drag.


Allot of airliners use this. The Boeing 737 and Bombardier CRJ, both use strips of bristle material to seal the wheel well when the gear is retracted. I don't see why it couldn't be used on wheel pants if you can fit them in there....
 
Google Lopresti wheel pants and look at the avweb article. A bit pricey at $1995 projected price.

I?m curious, does any one know why these never made it to market? Was there a flaw in the design, or were the proposed speed gains just not there?
 
How much gap are we talking. In the day before the two piece pants you had large gaps. Baffle material was common. Once we got the two piece you could make it tight. The down side is different tire profiles have broader tread shoulders or shapes and even diameters and widths.

Is it worth it? Yes if you want more speed. Is this one change going to make a measurable difference? No but every little change adds up to measurable gains, even if small. If you have less than an inch all around I'd leave it alone.

As far as air, yes brakes can get hot but only for multi touch and goes.
 
950 hours now. There is no glass bottom in the rear portion of the wheel pants; it was cut away after the mold process. The urethane rubber/glass fabric can ride over moderate rough places without damaging the pants. Clearance at the lowest point is only 3/4" inch, so I do apply a patch every few years over a worn spot which tends to form just aft of the tire. I've never had a flat, but there should be enough clearance along the sidewall to not break the pant.

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Keep the max air pressure and never have a hard landing 'cause the tires will destroy when they spread out !
 
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