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  #1  
Old 09-07-2019, 03:29 PM
rongawer rongawer is offline
 
Join Date: Dec 2007
Location: Brentwood, CA
Posts: 774
Default Wheel pants and landing gear fairings

I've read many different posts on the value, or non-value, of wheel pants and gear fairings. So, I've been experimenting and collecting some data and finally have a full report now that I finally have my wheel pants on, and the also made and installed main gear fairings with RV Bits intersection fairings. Noting that Van's says about 4KT for the pants; I can confirm that.

What I've found is that without any fairings on, I cruised at about 111 KTAS at 7500 feet at economy cruise power, averaged over about 100 hours of flying.

Then I installed the wheel pants and flew to KOSH and back this summer. I found I cruised about 115 KTAS for the same power averaged over the whole trip between 7500 and 9500 MSL.

And then I installed the main gear fairings and just returned from a trip to Nashville, down to Pensacola and then back home (C83). Over that trip I found I cruised at about 118 for the same power settings.

And at FT, well, she really gets after it.

And for the pundits, no, that's not calibrated data, it's just averaged flight time over about 250 hours. But a real set of data points no less.

I'm also finally figuring out this "posting photos on VAF work-around" thing.

Left gear


Right gear


All done (ok, done with installing the gear )
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- RV10, N762G, Build in progress.
- Several others that are now just great memories for me.

Last edited by rongawer : 09-08-2019 at 09:04 AM.
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  #2  
Old 09-07-2019, 04:30 PM
E. D. Eliot E. D. Eliot is offline
 
Join Date: Dec 2005
Location: San Pedro
Posts: 1,017
Default Good info, Ron

I intend to add main gear fairings sometime after certification and a thorough test series. Until I saw your main gear fairings, I thought that I had two options - get a set of RV-8 fairings or make up a set myself. I'm very interested in where you purchased your main gear fairings or did you make them? Please advise at you convenience. Thanks, Ed
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  #3  
Old 09-07-2019, 05:20 PM
rgmwa rgmwa is offline
 
Join Date: Feb 2010
Location: Perth, Western Australia
Posts: 1,675
Default

Useful numbers, so thanks for posting. I have the same setup and thought that they probably added no more than a couple of knots, so three knots is good.
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  #4  
Old 09-07-2019, 07:00 PM
NinerBikes NinerBikes is offline
 
Join Date: Dec 2018
Location: Granada Hills
Posts: 1,193
Default

What was the total price, all in, to add those 7 kts? A cost value proposal. If you put a lot of hours on your RV, kind of wondering the payback period in efficiency?
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  #5  
Old 09-07-2019, 08:28 PM
Taltruda Taltruda is offline
 
Join Date: Oct 2017
Location: Las Vegas, NV
Posts: 918
Default Pants and legs

My buddy with an 8 reported 3 knots improvement with the wheel pants, but 6 or so from the leg fairings! The gear legs were significantly more important on his plane. Together they were only like 8 knots improvement..they didn?t quite add together.
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  #6  
Old 09-07-2019, 09:27 PM
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scottmillhouse scottmillhouse is offline
 
Join Date: Apr 2007
Location: Madison, AL
Posts: 347
Default

As another data point, on my new 7A I recently added the pants and legs and intersection fairings and gained 9 knots. On my 12 I gained 3-4 knots for just the wheel pants with only the nose leg fairing.
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  #7  
Old 09-08-2019, 08:57 AM
benfra benfra is offline
 
Join Date: May 2007
Location: ft MYERS, FL Based @KPGD
Posts: 35
Default Fairings

I used Texas Aeroplastics for the top and bottom of my gear. They are made out of plastic but they are made for the RV 12 and fit nicely on wheel pant and fuselage. Havent determined how much they add to top speed. These cuffs fit the standard gear legs with openings at rear for brake lines

Last edited by benfra : 09-08-2019 at 09:06 AM. Reason: added content
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  #8  
Old 09-08-2019, 10:04 AM
rongawer rongawer is offline
 
Join Date: Dec 2007
Location: Brentwood, CA
Posts: 774
Default

Regarding the speed gains, understanding that speed is proportional to drag squared, the faster normal cruise speed, the greater improvement in speed drag reductions make. For example, an RV10 that cruises at 175KT will likely see 10-15 knots reduction (160-165KT) without gear fairings. But an RV12 that cruises at about 2/3 the speed should see less speed change for the same drag change; so 6-7 knots total is in line with that.

For costs and setup, I bought my intersection fairings from RVbits.com, although I noted that are now sold through Cleaveland Tools as well, which will save on shipping from S. Africa. I believe the price was about $180 with shipping.

I bought the GEAR LEG FAIRING ROD from Van's for the 'A' models. You don't want the FLAT leg ones as they're too wide for the 12's legs and RV Bit fairings are formed to fit the ROD ones. I don't recall the cost, but they too were about $200.

So all in, about $400 plus some misc hardware.

For installation, RV Bits includes instructions for the intersection fairings, but it's pretty simple. You will need to cut the gear leg fairings down substantially; I recommend starting at the narrow end and measuring up about 19". Then fit them up, mark to match the fuselage and cut again. My fairings are 17.5 short side to 18" long side...YMMV...measure twice...

I used 8-32 Rivnuts on the fuselage (4 per fairing) and 8-32 nut plates on the wheel pants (also 4 per fairing). You could use sheet metal screws if so inclined or go with #6 screws as it's fairly small load.

I did not run piano hinge the whole length, but rather just the middle 10", which is very adequate; this allows for inserting or removing the pin out without having to remove the wheel, yet holds the entire trailing edge firmly shut, especially once the IS fairings are in place, which clamp the ends.

I used 1/2" foam weather stripping at two points wrapped around the gear to support the fairings. You will find the fairings fit fairly snug and no additional measures, such as wood or epoxy, are really needed, but you may decide differently. I found that installed the way I did, there is no alignment needed as the fairings are snugly aligned to the 12's flat gear legs.

As for payback from efficiency? Well, at 118 knots I'm cruising about 6% faster for the same fuel burn than I was at 111 knots. A rough ROI based on 250 hours a year, which is about my average, and use a 5% improvement with $5 for 100LL and 5 gph as a consumption (my flight planning numbers), that's about $300 a year in savings, so it pays me back in about 18 months or a couple years burning MOGAS at $3.50/gal. But frankly, I've generally stopped doing economics and ROI's on airplanes, especially after the Baron... my wife wanted me to sell the thing and fly SouthWest - missing the whole point; which is that I just did it because I wanted to and I could. And they give the little bird a nicer looking set of gams.

BTW, my wife actually flew with me the whole way to Pensacola last month and even commented that she enjoyed it. I consider that "paid in full".
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- RV10, N762G, Build in progress.
- Several others that are now just great memories for me.

Last edited by rongawer : 09-08-2019 at 10:08 AM.
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  #9  
Old 09-08-2019, 10:15 AM
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wcalvert wcalvert is offline
 
Join Date: Jan 2019
Location: Anacortes Wa
Posts: 337
Default Real lesson learned...

That last comment about your wife and ROI says it all.

Don't want your last words on earth to be something like "wish I had ..."!

Cheers
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  #10  
Old 09-08-2019, 11:06 AM
John-G John-G is offline
 
Join Date: Jan 2012
Location: Northeast Ohio
Posts: 759
Default Wheel pants .. check. Easy access to valve stem .. fail.

I too have seen speed increases after recently installing wheel pants and gear leg /intersection fairings on my RV-12. My airspeed increases appear to be in line with those previously mentioned.

But gee! What a hassle it is now to check tire pressures. I'm sure those of us that have wheel pants on our RV-12's would gladly pay for a well machined, chrome plated, heavily spring loaded trap door system that would allow easy access to the tire's valve stem. A good looking, well thought out, form fitting assembly that can be installed without trashing an existing paint job.

Perhaps a worthy project for Aircraft Specialty to add to their wonderful line of support products for the RV-12.
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