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Gravel deflectors

Greg Arehart

Well Known Member
Welllll.... I'm in the end stages of modifying my RV-9 to take bigger wheels for landing on some less-than-optimal strips. The new wheels (8.00 x 6) will obviously be too big for normal fairings, so I am designing (or thinking of designing) some gravel deflectors in an attempt to save my paint. Thus far, I've found a couple designs out there, but not much. Here are a couple photos of some Cessna deflectors:





So, I'm polling the collective wisdom here to see if anyone has

1) links to other photos/designs out there; or
2) thoughts on optimal design (like, how low the bottom of the deflector should be above the ground to keep gravel off the tail); or
3) any other words of wisdom on building these.

Thanks,
greg
 
Greg! Bob showed me your steed, looks good!

Ever seen that show "Flying Wild Alaska?" All their planes have gravel deflectors like your second picture.
 
Gravel delectors.

Hey Greg,
I work for Hageland Aviation, the Flying Wild Alaska guys. The lower photo you have is the Aero Twin deflector. It is made from square stock, about 3/4" with 1/8" or 3/16" plate where it mounts, and fiber reinforced 1/4" rubber. The deflector mounts on the inboard side of the axle,and shares the same bolt as the axle. The STC puts longer bolt there. The rubber is longer than it needs to be so it can be redrilled after it wears out, and attaches with 3/16" hardware. The rubber is trimmed so it just touches the tire, the tire wearing the rubber to fit. The vertical piece of rubber is about 3" above the ground. We don'tget 207's through our shop very often, that would be the Bethel guys. I can get you 208 Caravan photos if you like.
 
Andrew,

Thanks for the info - truly amazing the expertise on this forum! So, a couple other questions/thoughts.

Do you have any sense how much lateral gravel spray occurs? Obviously the second design doesn't really cover much laterally, at least on the outboard side of the wheel.

Right now I'm thinking a single flat plate at about 45 degrees angle (down and back from the wheel), rather than the two different pieces at 90 degrees in the photo. This would be simpler to build and would store flat for travel (I don't plan on having the big wheels on all the time). With the RV, I could probably build it from less beefy material, as I can attach the bracket on both sides of the wheel.

I probably don't need photos of the 208 unless the design is significantly different. I'm mostly thinking about aerodynamics (minimizing any excess drag) and the gravel spray angle/direction.

cheers,
greg
 
Big Tires

Greg:

I put 8:00 X 6 tires on an RV-10 and used the 10 wheel pants by opening them up to fit the larger tires. You will have a lot of tire exposed at the bottom, but will still not see too much speed reduction. I have landed on a lot of gravel and some rock, but have had no damage. Just a thought.

Tim James
 
Mud spray

Greg
These deflectors act as much as a tire scraper as a deflector. Even so, the wing bottpms still come home with a mud stripe after flying on a rainy day. Leading edges of horiontal stabilizers, bottoms of flaps and elevators take a beating as well. What really kick up the rocks is being hard on the brakes, espessially when you first touch down. Once those rocks are in motion, the deflector helps, but they do bounce. I'm not sure what 45 degrees will do. Using a "plate" as apposed to something that will dissipate some of the rock enery is another question. Please let me know what you come up with as I am on a gravel strip and have hundreds of gravel places to go.
 
Andrew,

I'll keep you posted. Maybe even fly over and show you what I ended up with later in the summer! I definitely will use some rubber and contour to the tires, as well as popriveting or somehow attaching some rubber to the plate to dissipate the energy.

Tim,

Interesting idea. Probably not enough time to do that this summer, but may be a winter's project. What kind of speed change did you see?

cheers,
greg
 
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Bill,

I never ended up using the deflectors last year - seemed that I didn't really need them as long as I was careful on the brakes. Mind you, I didn't land on any gravel bars etc, but did go to some pretty gravelly strips. I did get a few paint chips, but nothing really significant. I'm currently in northern BC working on my cabin (without the RV unfortunately) but if you'll remind me in early October, I'll send you some additional photos.

Cheers,
Greg
 
....snip...


I'm currently in northern BC working on my cabin (without the RV unfortunately)

...snip...

Cheers,
Greg


Greg you got quite a location for your cabin. Fantastic view of the lake and mountains! I am following your project via your Picasa album. What the state of gravel at Atlin airstrip? Can little wheelies handle it? Your camp is a quick hop from PAJN with picturesque landscape on the way.
 
Vlad,

Airstrip at Atlin is in very good shape. Not a problem for any RV to land, and numerous ones have done so (including me of course). They just regraded the northern third of the runway this June. On a day like today (100% clear blue sky and 65 degrees, little wind) it is a short half hour hop over the icefield to PAJN, with fantastic scenery the entire way.

Cabin building continues and hopefully will be in the RV hotel pages sometime next summer. We'll be here from mid-May through mid-August next year, and its about 10 miles to the runway from our place. We see most of the air traffic between Atlin and Juneau (not that there's much) going by the cabin.

Airport webcam:
http://www.metcam.navcanada.ca/hb/player.jsp?id=92&cam=204&lang=e


Greg
 
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gravel damege

High altude strips are the places to worry about gravel damege. Your take off roll will be longer, more gravel to roll over!
 
HS protection

I wonder about putting a rubber band along the leading edge of the horizontal stabilizer. I'm thinking specifically of what you find on some Cessna 180s and 185s. It's just a thin piece of rubber glued to the leading edge that helps keep the rocks from denting stabilizer. Find a thin piece and make it tapper to the edges, I'm sure you wouldn't even notice it's there.

Here's the best picture I could find with a short search http://i40.photobucket.com/albums/e226/ckeat/IMG_1025-1.jpg
 
lots of good ideas to.....borrow!

Hey Greg, love the bushwheel idea!
I googled a few things, and have seen some others in old magazines....seems there are numerous approaches.
1. the mud flap design - with obvious pros & cons
2. the fender - can be an airfoil shape well above the tire, and still protect the wing, but not the HS.
3. the fairing - like half a wheel pant in a teardrop behind the wheel. Best aerodynamics, and better HS protection, but can still throw mud forward.

funny how the best looking stuff is from the 1930's. ( probably hand made formed aluminum etc. Now we can whip up foam & fibreglas or carbon in hours, instead of days of work!)

perhaps a video facing rearward will answer the gravel spray pattern question, without much risk! :)
 
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