RV7 Gear Leg Fairings - Securing Them Now That I've Removed the Original Foam Fill...

[donmtt]

Hi All -

So I've been reading plenty about the gear leg fairings on the RV7. My bird (which I didn't build) had spray-foam filled fairings. I've removed all the foam and cleaned things up (after installing TS Flightlines brake lines). Now I'm trying to figure the best way to secure the leg fairings going forward.

I have the Van's plans and the original idea appears to be to notch the fiberglass and use a hose clamp on the upper part - to keep the fairing in place. Seems reasonable, but I wonder about longevity? I thought about building an aluminum strip, attaching/aligning IT with a clamp, and then bolting the fairing to that piece of aluminum?

I also installed new tires, tubes and balanced everything. The gear leg shimmy that I occasionally had prior isn't there now. From reading the forums I understand that the shimmy free landings may not last. I like the shimmy dampers that involve adel clamps and a 2" strip of aluminum. I mention this because it seems that solution may be an aid to the fairing mounting if I go that route? Maybe I should just build the anti-shimmy and then mount the fairings?

And what about the bottom of the fairing? Does that need some support? My fairings have the piano hinge per the plans, and they do seem pretty strong torsionally. So maybe they can float the the bottom? (There is no support/interface to the wheel pant. I do have the upper fairing which I'm hoping will help me with the fairing alignment - since I understand that's important too...)

Lots of details here, I acknowledge.

I'd love to see some pictures of others who have addressed the fairing mount issue, if possible. For me, a picture is worth a thousand words...I'm inclined to wait on the shimmy fix since it's gone for now...

Thanks!

 

[D-Dubya]

You should get the Van's drawings (and the manual if possible) that show how all of this should be done. It makes so much more sense than just trying to explain it. If you don't get them from Van's, there are some drawings out there that people have posted for reference. But in summary, the top of the gear leg fairing should be held in place with the worm gear clamp on a notched tab at the top of the gear leg fairing. Some builders have reinforced the fiberglass tabs with additional fiberglass or carbon fiber layups; some have also used an aluminum "T" as reinforcement.

The upper intersection fairing will also help to hold the gear leg fairing in place and prevent twisting in flight. At the wheel pants end, the lower intersection fairing is typically molded into the wheel pants, so that will hold the lower end of the gear leg fairing in place and help prevent twisting as well. All of this needs to be aligned with strings, levels, squares, and whatever else it takes to ensure that everything is aligned to the proper FLIGHT attitude (not on the ground). This not only lowers drag, but it prevents imparting an unwanted yaw. If you're having to make or install new fairings, it's unlikely that you'll figure out the proper way to do this on your own. I had to read Van's instructions multiple times, and Van's includes a bunch of pics in their build manual. There may be a video on this, but I'm not positive. It's been a long time since I looked at builder's webpages, but there are likely some good step-by-step descriptions with photos to be found.

The shimmy dampers with adel clamps and a strip of aluminum are for the nosegear--or at least those are the ones I've seen. I found one pic when I was mounting the prop that shows both the upper worm gear clamp end and the lower intersection fairings epoxied to the wheel pants. There are myriad ways to do this, though.

 

[DrillBit]

On my RV-9A, hose clamps on the tabs up top and the bottoms captured by the lower intersection fairings (split and bonded to the fore and aft parts of the main wheel pants) firmly secure the gear leg fairings. The trick was aligning the wheel pants and gear leg fairings first, then bonding the lower intersection fairings to lock in the alignment. The upper intersection fairings were then put in place, so in the end the clamped tabs constrain movement up or down the gear legs, while the intersection fairings guarantee consistent alignment of the gear leg fairings when everything comes off and goes back on for the condition inspection each year. Clear as mud?

 

[Desert Rat]

Lots of guys have used the Vans method of a tab cut into the upper end. I went that way and if it ever cracks, I'll deal with it then.

A more robust alternative is an upside down T out of thin aluminum with the cross bar of the T riveted/bonded to the fairing and the band clamp capturing the vertical leg against the gear leg.

I recall from your other thread that this is rework on an existing plane. Assuming that it already has upper and lower intersection fairings and that it flew straight before you took the foam out you don't have to mess around with strings and lasers and all that stuff to get them straight with the airflow. The mounting holes in the intersection fairings won't line up unless you have the gear leg fairings clocked right.

No attachment necessary on the bottom end of the gear leg fairings. The intersection faring coming off the wheel pant will keep it where it's supposed to be fore/aft and the clamp up top will keep it secure vertically.

 

[uk_figs]

Just went through this exercise during my recent condition inspection, made up some connection brackets for the top per some earlier threads on VAF but ended up following the Vans instructions and cutting the slots for the hose clip at the top, simple and seems to work OK (did this on the original fairings that I filled with foam back in 2008). I also installed the shimmy dampers with the aluminum strip and adel clamps along the lines of a Paul Dye thread on his Rocket earlier this year, so far I am pleased with the damping performance and no shimmy to speak of.
Figs

 

[wirejock]

I fabricated two fairing clamps. They work well. Photo of the drawing below.
Round off corners as needed. Nutplates are staggered so screws from inboard or outboard don't hit the opposite side. The bracket is held to the leg with a simple worm drive clamp. Once adjusted, it stays put.
I also fabricated the stiffeners and clamps.
Leg fairings float inside the pant.