Gear Leg Fairing alignment

findane · #1 06-04-2020, 08:02 PM

I've fabricated the gear leg fairings and they fit nice and snug. In Van's directions it details a somewhat complicated procedure for aligning the fairings on the gear legs. Is it really necessary or can one just eyeball? I have no problem lifting the gear off the ground as suggested in the directions but is there a better way to align them than what Van's suggests?

DTARM1 · #2 06-04-2020, 08:16 PM

Findane the gear leg fairings are designed to reduce drag in flight (DIF). It's important to do it right and this is the reason why. When you fly your airplane at 160 kts for 3 hours in a straight line, any non-symmetrical drag will result in frustration to say the least, cause drag, and reduce airspeed and fuel efficiency. Drilling holes in something should only be done once - (and that is correctly). If you put the leg fairings on and then your airplane needs left or right, up or down trim while in cruise flight, you'll likely not be happy and you'll get mad at yourself for having to repair the holes you've drilled and make new. Van's uses aeronautical engineers with PE (Professional Engineer) licenses to design and write the instructions for building your airplane. They certainly know much more than I. I'm just a school trained A&P, IA with a 4 year degree from a Div I school and 27 years 5 months and 25 days in the Army. And I'm building an RV-8. I've not heard anyone who followed the instructions comment their airplane didn't fly straight. You've invested a lot of your time that you could have spent with your family or friends. You owe it to yourself to do what you think is best.

A PE is no joke. I went to NC State with a guy named Robert Medura and he was my room mate, to say the least, he's the smartest human being I've ever met in my 53 years of life. Robert's dad had a manufacturing plant and made Nuclear Grade vacuum systems. Robert worked for his dad, was majoring in Electrical and Aerospace Engineering at the same time and was the Captain of NC State's NASA research funded walking machine program, the development of NASA's Mars rovers Spirit and Curiosity programs. Robert graduated Suma Cum Laude and 1st in the entire NC State graduating class. The week after graduation, Robert sat for his two PE exams and was awarded his PE.

PE's are the smartest people walking the face of the earth and should get respect especially for something that flys.

cfiidon · #3 06-05-2020, 06:48 AM

I would recommend you follow the instructions and be as precise as possible. I was very happy that after building my -8 that it flew very straight and true with no rudder trim. In cruise the ball was perhaps slightly slewed to the right, but not much.

I had to replace my left wheel fairing and perhaps got a little sloppy. When I next flew, the ball was slewed 1/3 ball outside the line to the right.

After a recheck I discovered that the trailing edge of the fairing was almost 5/8 of an inch towards the center line. That was enough to add asymmetrical drag and require more right rudder in cruise. I corrected the issue and now all is well again.

Use high tech (laser) or low tech (strings and plumb bobs), but take your time and be as precise as possible.

Good luck.

Discus2b · #4 06-05-2020, 07:18 AM

Quote:

Originally Posted by DTARM1

Findane the gear leg fairings are designed to reduce drag in flight (DIF). It's important to do it right and this is the reason why. When you fly your airplane at 160 kts for 3 hours in a straight line, any non-symmetrical drag will result in frustration to say the least, cause drag, and reduce airspeed and fuel efficiency. Drilling holes in something should only be done once - (and that is correctly). If you put the leg fairings on and then your airplane needs left or right, up or down trim while in cruise flight, you'll likely not be happy and you'll get mad at yourself for having to repair the holes you've drilled and make new. Van's uses aeronautical engineers with PE (Professional Engineer) licenses to design and write the instructions for building your airplane. They certainly know much more than I. I'm just a school trained A&P, IA with a 4 year degree from a Div I school and 27 years 5 months and 25 days in the Army. And I'm building an RV-8. I've not heard anyone who followed the instructions comment their airplane didn't fly straight. You've invested a lot of your time that you could have spent with your family or friends. You owe it to yourself to do what you think is best.

A PE is no joke. I went to NC State with a guy named Robert Medura and he was my room mate, to say the least, he's the smartest human being I've ever met in my 53 years of life. Robert's dad had a manufacturing plant and made Nuclear Grade vacuum systems. Robert worked for his dad, was majoring in Electrical and Aerospace Engineering at the same time and was the Captain of NC State's NASA research funded walking machine program, the development of NASA's Mars rovers Spirit and Curiosity programs. Robert graduated Suma Cum Laude and 1st in the entire NC State graduating class. The week after graduation, Robert sat for his two PE exams and was awarded his PE.

PE's are the smartest people walking the face of the earth and should get respect especially for something that flys.

:cool :

R

findane · #5 06-05-2020, 07:55 AM

Looks like strings and plumb bobs. Thanks for the kick in the rear.

Discus2b · #6 06-05-2020, 10:04 AM

And you thought you were in the ?Air Force?.

R

Steve Barnes · #7 06-05-2020, 12:47 PM

If you purchased the upper gear leg fairing from one of the vendors, I believe the top gear leg fairing indexes the gear leg in the proper orientation.

Steve

Scott Hersha · #8 06-05-2020, 02:33 PM

I can vouch for that (above). I bought my intersection fairings from Fairings, Etc (Bob .....). He said that I wouldn?t need to do the plumb bob/string exercise, they would index the leg fairings precisely. I did the plumb bob thing anyway - takes some time to do right. They lined up perfectly with the upper intersection fairings. I?ve used those fairings 3 other times since then, including my current RV4, and didn?t do the plumb bob procedure, and I?ve had excellent results. Ball stays in the middle, I?m as fast (or faster) as anyone I fly with, and on my RV4, I don?t even have a rudder trim tab to stay neutral in cruise. I can?t take credit since I didn?t build this one. I did install new upper gear fairings and ?fixed? the tail fairing though. My builder was a machinist, and spent 20+ years building this RV4. I wish I could say I built it. It flies as if on rails.

SeanB · #9 06-05-2020, 03:26 PM

Anyone know if the ones from RV Bits / Cleaveland self-align?
https://www.cleavelandtool.com/colle...18378230890558

David Paule · #10 06-07-2020, 09:36 AM

Quote:

Originally Posted by DTARM1

....PE's are the smartest people walking the face of the earth....

Well... not all of them. And I ought to know, since I've worked with some of them over the years.

That said, if you're an engineer, it's worth having that license. It does being professional respect roughly like a PhD would, and it's a lot easier to get. Note that, and this might vary state to state, the license is specific to a particular field. For example, you wouldn't want an aerospace P.E. to sign off on a bridge or other civil engineering design any more than you'd want the civil P.E. to approve your airplane design. Also one state's P.E. license might not be transferable to another state.

Dave, P.E. retired
And yes, I'm including myself in the list of P.E.s who are not the smartest people around.