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Bob Axsom

Well Known Member
I was surprised by the speed gain when I added a sub-fairing to the nose gear - the speed went up to 184.4 kts. The sub-fairing is two piece (fore & aft) with the forward part having a flange that extends over rear part by ~1/4". I had a aluminum clamp strip riveted to both sides of the the forward part so that they went inside the aft part. Thus the flange and clamp strip forced a tight closure of the gap between the two halfs.

After the 2008 Airventure Cup I made a rough short approach at Jefferson City, MO and caught one of the clamp strips with the nose tire sidewall. I removed the strips and refinished the sub-fairings and have flown with a small trailing gap which I thought would not be significant. Well I have been flying around 182 kts since then. It dawned on me that the small trailing gap may be a problem. I'm going to add some fiberglass extensions that will allow me to add a piece of aluminum inside the aft part of the sub-fairing on both sides and tap them for #8 screws. This will allow me to pull the gaps closed and see if that speed comes back.

Bob Axsom
 
Link

Bob Axsom said:
They are in a thread with this title:

Subfairing for Oldstyle RV-6A Nosegear

Bob Axsom
Click to expand...

Thread link http://www.vansairforce.com/communi...&highlight=Subfairing+Oldstyle+RV-6A+Nosegear

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8-15-10 status

The three layer fiberglass tabs have been added at the lower rear end of the fwd part of the subfairing. They have been shaped and sanded to a smooth low profile extension over the aft part of the subfairing. Small plates have been made from 0.090" 2024T3 aluminum, tapped for 8-32 screws, filed to a smooth tapered edge all around and double flush riveted inside the aft part of the subfairing. I decided to use dimpled washers with flat head stainless steel screws to fasten the fwd and aft parts of the subfairing together near the bottom but on the side. There is a concern that the tire may come in contact with the custom tapped plates and that is the reason for the smoothing and rounding of the edges. The screws will be very short and will not extend beyond the innermost surface of the tapped fastener plates. There is no room for plate nuts which would have been the easy solution. Since the tapped plate fasteners have no mechanical locking device I will have to use non-permanent loctite upon installation of the screws. After the installations were complete I drilled out the mounting holes in the new tabs of the overlaying fwd part of the subfairing to 3/8" for the dimpled washers. Unfortunately, one of then caught and ripped out at one edge. I have added three more layers of fiberglass to the tabs and I am monitoring and working with them through the 24 hour cure cycle. When they are semi-hard I will cut the holes with an xacto knife and avoid the drill snag risk.

As I worked through this modification it became apparent that when the two attach points are fully implemented I do not need the overlapped fwd and aft part of the subfairing tabs at the top of the assembly. I removed the tab at this location on the forward part. This is a definite improvement though small.

Bob Axsom
 
The Tab Repair Went Well

I just cut the 3/8" holes and trimmed the excess material. All that's left is a little sanding, trial assembly and paint after the epoxy cures.

Bob Axsom
 
It looks fast even off your nose wheel...

Bob, have you try the same sub-fairing concept on main wheel pants, and the result? If not, why not?
 
Yes I did

The results are in this forum somewhere I think if you search under subfairings you will find the photos and test results. They are the newer design pressure recovery eggs and there was no measurably improvement. My nose gear fairing is the older flat sided fairing and the difference with the subfairing was remarkable.

Bob Axsom

Try this:

http://www.vansairforce.com/community/showthread.php?t=29326&highlight=MLG
 
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Field Report

I flew in the Grace Flight air race at Sherman, TX and both the speed dash and the cross country race at Courtland, Alabama on 10-30-10 and I have some information to report from the experience. After the Texas race I found that the right screw and dimple washer were missing after the race. I applied removable grade Loctite to prevent recurrence. That seemed to work well until the Courtland races. When I took off for the speed dash I did not pull back the stick as I usually do before releasing the brakes and I hit something that caused some vibration during the takeoff roll. After landing I saw that both of the aft tabs were loose, there was a crack on the right side of the front part of the subfairing and there was a large area of paint scraped off of the lower surface of the front part of the subfairing in front of the tire a little off center to the left. I screwed the aft screws back into the holes tapped in the aluminum plates and I decided to apply a mod that I have thought about for some time. I had brought along a roll of the blue gaffers tape with the idea of taping seams in mind. I did it but only to the nose gear fairing/subfairing interface. I flew the race and it performed excellently for this application. I will have all of the landing gear fairing seams taped for the Rocket 100 in Taylor Texas on 11-20-10.

From the above experience it is obvious that the design for holding down the rear of the front part of the NLG subfairing is no good. I will have to extend the tabs back to where I have enough room to install steel self locking platenuts. It is also obvious that the fairings are vulnerable to FOD on rolling surfaces like ramps, taxiways and runways but they are strong enough to take it and keep on functioning with only paint scrapes and minor cracks in severe cases. Part of the operational sacrifice for reducing drag in this area.

Bob Axsom
 
January 2011 mod

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I found that there is a location on the overlapping subfairings where I can drill a hole through both parts and into the main fairing on each side that can be used to force good closure and allow me to install steel self locking platenuts for a reliable low drag assembly that is clear of the tire. You can see it in the photo where the clecoes are installed. I have cut off the tabs from the previous approach, and removed the homemade tapped 0.090" aluminum anchor nuts. The photo shows the crack in the fwd part of the subfairing that has been sanded to start the repair (the first layer in on and sanded now). The new mounting holes have been enlarged to 3/8" in the fwd part of the subfairing for flathead #8 screws and dimple washers. The holes in the aft subfairing will be 3/16" and floating platenuts will be installed on the inside of the main fairing. Most of the remaining work is in the fiberglass area followed by painting.

Bob Axsom
 
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Progress on the tail end secured by platenut mod

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The fwd subfairing has a 2" wide fiberglass "patch" over it and the entire fwd subfairing sanded and another layer of fiberglass applied. I will add another layer of fiberglass and a strip inside over the lower part of the crack and another layer over the entire fwd subfairing before final sanding and painting.

Bob Axsom
 
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