Wooden Gear Leg Stiffeners, worth it?

RudiGreyling · #1 02-02-2007, 04:15 AM

Hi Guys,

My manuel tells me now to make wooden gear leg stiffeners...The Manual says some planes needs them and some don't...Hmmm...

Is it worth it? Have you done it before your first flight? Have you had issues without it? Have you retro fitted them afterwards?

The reason I ask, is that I don't want to add work, complexity and weight for something I might not need!

And if you have done it how did you route the brake lines around the stiffeners? It looks like it interferes with the brake line?

Thank you in advance,
Kind Regards
Rudi

pierre smith · #2 02-02-2007, 06:21 AM

Hi Rudy,
When we got to that point, I asked an A@P friend who's built six RVs and finished a dozen more about the stiffeners. He said don't put them on unless it shimmies and shakes. We didn't and the mains are fine. I have more problems with the nosewheel shaking up and down.
Regards,

mrreddick · #3 02-02-2007, 06:39 AM

I flew my 6A for a few months without the stiffeners. On more than one occasion, I had someone follow me to my hangar and tell me how bad my main gear was chattering when I applied the brakes to exit the runway. I didn't feel anything unusual but later, a video of a landing rollout showed me what they were talking about.
The stiffeners are available right here on vansairforce.net (go to the advertisers link).

Also, the chattering from the nose gear can be cured, too. Dan Urbanski, are you out there? Dan stiffened up his 6A's nose gear in the same manner as the mains. If he doesn't respond to your post, I can get his email for you if you're interested in doing the nose gear, too.

RV7ator · #4 02-02-2007, 07:12 AM

I wouldn't bother, Rudi. After operating two -7s, I find leg shimmy to be affected by gross weight, speed, tire pressure - all variables - if it's going to show up at all. Adding stiffeners, simplistically speaking, simply shifts the natural frequency, without adding dampening. The legs will vibrate under a different mix of excitations. I've seen no reports that adding leg stiffeners is a panacea. They also make brake line installation much more difficult.

John Siebold
Boise, ID

rvpilot · #5 02-02-2007, 08:54 AM

Recently, I saw the most convincing argument yet for installing the stiffeners. A friend was unfortunate enough to be involved in an off runway excursion due to brake dragging problems (another story!). One gear leg was severely bent, but did remain upright enough to support the plane and keep the wing off the ground. I believe had it not been for the the extra support the stiffeners provided, the gear leg may have completely folded under, causing the plane to recieve much more damage than it did. Stiffeners on the mains don't really add much wieght, aren't that hard to install, and can only help in most situations.
IMHO!

Rene Bubberman · #6 02-02-2007, 10:07 AM

Based on some scary stories I decided to add them. Not very hard with a power file. The brakelines go underneath. More info/pictures on: http://websites.expercraft.com/PHVII...ry&log_id=5233
and http://websites.expercraft.com/PHVII...ry&log_id=6035

all the best!

CraigH@KRPH · #7 02-02-2007, 10:37 AM

I had a lot of shimmy on my mains before adding the stiffeners. If temps are in the 30's, I still get a small amount of shimmy at times after installation. However, the improvement in warm temps is dramatic and well worth the cost/effort.

Chino Tom · #8 02-02-2007, 12:00 PM

Instead of the wood stiffners, I used 1/2 inch sch 40 (thick) PVC pipe on my RV-6. About a third of the pipe is cut off (makes a "c" shape) in a bandsaw.
I used 3M strapping tape wrapped along the entire length of the PVC (mounted to the back of the gear leg). The brake line is inside the PVC. Adds a little dampning. Going to do the same on my 8A.

Tom

gmcjetpilot · #9 02-02-2007, 12:33 PM

http://www.vansairforce.com/communit...ight=gear+wood

http://www.vansairforce.com/communit...=dampener+gear

http://www.vansairforce.com/communit...ight=gear+wood

http://www.vansairforce.com/communit...=dampener+gear

Here is some more info. I flew with out and with on my RV-4. It definitely made the taxi feel more solid and could taxi faster without shimmy. Was it bad before? No, not really. So is it needed? Yes and No. You can always start with no gear leg stiffener (save build cost, time and weight) and add later if you decide you do need it. Your main's (tires/wheel pants) will move around more without the stiffeners. Go to an airshow and watch RV's taxi and with and without stiffeners. You only really feel it if you get going and the tire shimmies.

Does it make landing easier? I don't think so. Does it feel more solid? Yes. If you use a solid piece of wood, attached well along the whole length, it lends itself to a more solid taxi feel. No doubt in my mind. My new project I am going without again. If I need it, I'll add it later. Its a pain in the back to make and install. It also makes the gear leg fairing a little thicker since you have to wrap a few plies of glass around the gear leg. (I suggest S-glass tape or carbon cloth.)

If you fly a real big airport with LONG distance wide open taxi's, than you may want to go with the stiffiner. I find at high speed taxi with out, you will likely shimmy at some point no matter how well tire pressure is adjusted. If you taxi slow than forget it. Also if you want to finish your plane, paint it and not work on it again, go ahead and consider doing it now.

Rick6a · #10 02-02-2007, 02:52 PM

Rudi,

The instructions included with my 6A's builders manual says that the shimmy phenomena is a "rather nebulous thing." Some airplanes experience it, other's don't. Now I have this theory......but it is only a theory that may account for shimmy problems in some airplanes. Many moons ago, the older kits required the builder to make measurements and gear leg adjustments accounting for toe-in before the builder himself drilled out the gear legs through the weldments. Given the large amount of steel that had to be drilled through, it is easy to imagine that some builders could be more precise than others. It doesn't take much error when drilling such holes to end up having a shimmy problem aggravated by a slight toe-in misalignment or other differences between one gear leg and the other. My kit was produced in 2000 and had the gear legs and weldments already drilled out so it took that potential builder error off the table. Anyway...that is my theory. My view at the time was to leave the wooden stiffeners off and only install them if shimmy proved to be a problem which to date, happily has not been.