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Wheel Pants or Gear Leg Fairings - which first?

IowaRV9Dreamer

Well Known Member
Since I'm sidelined waiting on getting an engine, I guess I have to work on my gear leg fairings and wheel pants.

My question is, what is the best order to work on these? The manual lists gear leg fairings first, but I'm not sure if that matters.
 
I did the nose wheel pant first, it was the easiest. The the main wheels, then the gear leg fairings. All in all it goes quick, really only a weekend job. Now, pinhole filling and final finishing is a whole other story:eek:

The wheel holes in the bottoms need to be enlarged quite a bit. The hairline scribed into the fiberglass is a good starting point as I recall.
 
I think wheelpants first. There's a lot more work to do there than leg fairings, and it helps with the latter if you know the exact location of the former. ;)
Agree fully with the advice bout wheel/tire openings. They require a ton of grinding/refitting iterations to get the clearances safe and serviceable.
 
A meticulous job would do that, since they would be symmetrical and have same drag on both sides of the airframe. It does not mean they are aligned with the airflow.
 
Since I'm sidelined waiting on getting an engine, I guess I have to work on my gear leg fairings and wheel pants.

My question is, what is the best order to work on these? The manual lists gear leg fairings first, but I'm not sure if that matters.

I am gathering funds for the big fan plant like you, Like others said, either one, BUT, you will need to put the gear leg fairings in trail alignment before installing the intersection fairings, they lock it all in. Lots of fun, and I did find that an empty fuse on the ground, has enough weight to change the wheel pant alignment ever so slightly..... I did mine in the air.
 
correct, the tires are not flying paralell with the fuse in flt, the pants and gear leg fairings are. vise versa on the ground.
 
Here's a thought...

Buy the upper fairings and take a close look at them. There are marks on the inside from the rivet line and skin joints from the plane they used to make the original fairings.

Since all of our planes are identical, thanks to Van's magic match hole process, stick the intersection fairings on the plane and use them to a line the gear leg fairings.

You may find everything comes out perfect. If not, make the minor adjustments needed.

For the lower intersection fairings, epoxy them to the wheel pants and then cut them so the front half comes off with the front section of the wheel pants.
 
Really? hum, I see 1/4" aileron deflection making the plane role, ( on a friends 6, I'm not flying yet) So I went through a lot of work with strings, jigs, tape measuring, and calipers to make sure my gear leg fairings were "0" out to the centerline of the fuse. Time will tell......
 
correct, the tires are not flying paralell with the fuse in flt, the pants and gear leg fairings are. vise versa on the ground.

So the tires in flight and upon landing are not pointed straight down the runway? By how much are they off?

This would mean that people who take the weight off the wheels to install wheelpants, do not have wheelpants that are aligned to the tire tread. I'd like to see some measurements from people as to how far the wheel pants are deviating from, for example, the centerline of the tire front to back.
 
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Good question.

I know of others that have installed their wheel pants with the plane on the gear.
How much movement is there?
Bill
 
The gear squats/spreads with 1100 pounds on it, thus inflight with no load it moves. It states this all in the build manual, also goes on to emphasize that it only takes a fraction of an inch to throw the ball off center. If you were precise you could have both pants and fairings nullifying the cumulative errors, but it's costing you knots. I would challenge you to plumb your fairings as is, then jack the plane and do it again, see if there is movement.

This is all spelled out in great detail in the manual.

This is a blurb in the 8 manual, in the 7 manual there was half a page emphasizing this.

mk7m3a.jpg
 
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Yes, I read the instructions. But you'll also note the instructions say the goal is NOT to align with a line on the ground, but with the wheel and tire.

Thus my question: If you align meticulously with the wheel and tire, how does that change with the removal of weight?

From what I can tell, the wheel/tire orientation changes in relation to the fuselage (and, of course, the ground), but it shouldn't change in relationship to a wheel pant that is aligned, attached to, and guided by the wheel in the first place.

If the wheel should tilt left, say, 1 to 2 degrees when the weight is off, theoretically, a properly installed wheel pant should also tilt 1 to 2 degrees since it is attached to the wheel -- and only the wheel -- on both sides.

It's true, of course, that the leg moves with/without weight. All you need to do is look at the marks on your leg fairings where it enters the intersection fairing to see evidence of this. That point is not in dispute.

What I question is this assertion that the alignment of a properly installed wheelpant would change in relation to the tire tread in any normal situation. If it does, then all of your wheelpants installed with weight off the gear are currently NOT aligned with the tire tread while sitting on the ground. This should be easy to prove. I'm just asking people to take the measurements to prove this fact because I believe the point of taking weight off the gear and THEN aligning the wheel pants with the tire/wheel is intended primarily to keep people from aligning the wheel pant with a line on the ground.

Anyway, the next time people have some time to spare, check to see if your wheelpants on the ground are aligned with the tire tread. If they are, then this is much ado about nothing.
 
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Yes, I read the instructions. But you'll also note the instructions say the goal is NOT to align with a line on the ground, but with the wheel and tire.

Thus my question: If you align meticulously with the wheel and tire, how does that change with the removal of weight?

From what I can tell, the wheel/tire orientation changes in relation to the fuselage (and, of course, the ground), but it shouldn't change in relationship to a wheel pant that is aligned, attached to, and guided by the wheel in the first place.

If the wheel should tilt left, say, 1 to 2 degrees when the weight is off, theoretically, a properly installed wheel pant should also tilt 1 to 2 degrees since it is attached to the wheel -- and only the wheel -- on both sides.

It's true, of course, that the leg moves with/without weight. All you need to do is look at the marks on your leg fairings where it enters the intersection fairing to see evidence of this. That point is not in dispute.

What I question is this assertion that the alignment of a properly installed wheelpant would change in relation to the tire tread in any normal situation. If it does, then all of your wheelpants installed with weight off the gear are currently NOT aligned with the tire tread while sitting on the ground. This should be easy to prove. I'm just asking people to take the measurements to prove this fact because I believe the point of taking weight off the gear and THEN aligning the wheel pants with the tire/wheel is intended primarily to keep people from aligning the wheel pant with a line on the ground.

Anyway, the next time people have some time to spare, check to see if your wheelpants on the ground are aligned with the tire tread. If they are, then this is much ado about nothing.

You're assuming that the gear legs are square and there isn't any toe in or out.

The gear is meant to roll straight on the ground with the weight of the plane, not be faired into the wind in flight with weight off.
 
Yes, I read the instructions. But you'll also note the instructions say the goal is NOT to align with a line on the ground, but with the wheel and tire.

They key point is that it says to align with the vertical axis of the tire, not the ground.
Keep in mind, everything is written in the context that you were told to lift the airplane to level flight attitude, with the tires were off the ground. If you do that, the tires are cambered outboard at the top (and they are also toed in) . That statement means to also camber the wheel pants outboard at the top (aligned with the vertical axis of the tire) not aligned perpendicular to the ground. All other axis (pitch and yaw) are to then be aligned longitudinally to the centerline of the airplane (in flight the tires are not aligned to the centerline, they are toed in). Simple terms... align them so if in straight and level flight, a bug hit the very leading edge or tip of the fairing and was able to pass straight through, that it would exit centered on the aft point of the fairing. Doing so will give you lowest drag of the fair as aligned to relative wind in cruise flight.

An airplane that flys straight with no trim issues, does not mean it has no trim drag. It could mean all of the out of trim components are counter acting to result in a neutrally trimmed airplane (but potentially not as fast as it could have been).

More simple description... attach a small parachute (both the same size) to each of your wing tips. It would not change the trim of your airplane, but you would go slower.
 
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No one is suggesting the wheel pants be aligned with anything on the ground.

If you were to take a vertical laser, and run it up the front of the tire over the top, aligned perfectly with the center line tread, and take another laser and run it from behind and up the top, neither laser is going to be level with the ground. That makes a pretty good reference in aligning the wheel pants because those should also establish a line that is lined with the wheel. In this picture, you can actually see the difference between a vertical line and the line of a wheel pant aligned with the tire/wheel.

2012-03-15_14-18-10_468.jpg


My question is: If the wheel pant is aligned with THAT line (which, again, is a reference to a wheel/tire, not the ground) , how is it that line -- specifically the relationship with the line on the wheel pant and the line on the wheel, could change, given that the wheel pant is afixed to the wheel? It seems to me that the relationship between that line for the wheel pant and that line on the tire/wheel would not change at all in any configuration.

In my case, as you point out, the vertical line of the aft end of the wheel pant is not 90 degrees to the ground; that would be foolish. But it is parallel with the vertical line of the wheel.

laser_pant.jpg


If that is accomplished on the ground, how can the relationship between the two components, change with the removal of weight?

I can certainly see where it would if you aligned it with a vertical line in relationship to the ground, but that would be stupid to do it that way.

In terms of my lack of issues w.r.t the ball. True, I could have perfectly matched the two wheel pants and fairings (I didn't have any problem without pants/fairings), but that would be the first time in 11 years of building that I would have gotten two things perfect. :*) I checked the ball w/o pants. Installed pants, checked again. Lined them to the tire using lasers and checked again. The chance of both sides turning out exactly the same to negate the improper alignment of one another seems very remote. Especially since it zips right along w/ a fixed pitch prop.

I only wish I'd been as good on wing incidence.
 
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You're assuming that the gear legs are square and there isn't any toe in or out.

The gear is meant to roll straight on the ground with the weight of the plane, not be faired into the wind in flight with weight off.

In that case, then an instruction in any weight condition to align anything with a tire tread would be improper.
 
I took a lot of pics in my build log if you care to look, I followed the manual to the letter. Set the fuse in flt level aditude, tires off the ground, make the pants fly straight, a lot easier said than done.
 
In that case, then an instruction in any weight condition to align anything with a tire tread would be improper.

What the instructions were trying to say is... with the tires clear of the ground and the airplane in level flight attitude, align the wheel pant to the center line of the tire only in roll (vertical axis). For the other two (pitch and roll axis) align them to the centerline of the airplane. In roll, as far as drag is concerned, it doesn't matter what the roll orientation of the wheel pant is, so it is aligned with the tire to give as much interior clearance as possible, and to allow for as small of a wheel pant as possible.

The reason for all of this is that a rod gear leg that has aft sweep like on the RV's, when it bends under load it bends outward, aft, and twists. All three of these actions will effect the alignment of the wheel. If the alignment of the wheel changes, the alignment of the wheel pant will also. That is why it is specified that you do the install with all weight off the gear. In flight we don't care what the yaw alignment of the tire is, only the fairing that is over it.
 
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Has anyone had experience with using Sikaflex to bond the wooden gear stiffeners to the gear leg?

Opinions?
 
I took a lot of pics in my build log if you care to look, I followed the manual to the letter. Set the fuse in flt level aditude, tires off the ground, make the pants fly straight, a lot easier said than done.
Bret - THANK YOU THANK YOU THANK YOU! The effort you took documenting your build will allow me to get unstuck. I'm a visual learner and this is just what I needed!

Especially picture 24 of 10/20/2013.. which clearly shows how the wheel pants are aligned to the airstream, not to the tire in flight. All of the discussion above hopelessly confused me until I saw your pics.

Again, Thanks! :)
 
Has anyone had experience with using Sikaflex to bond the wooden gear stiffeners to the gear leg?

Opinions?

The whole point of the wooden stiffeners is to dampen out the gear "wobbles" for lack of a better term. By using sika flex I would imagine you're allowing the gear to flex away from the stiffeners, it is rubbery. It may fail under that much flexing. By using fiberglass tape you're firmly securing it and allowing it to dampen the gear.

That said, most guys I know don't use them. If you find later after flying that you need them you can add them later.

Bret you should've been at MEV the other day, I was desperately trying to break rvmills rocket 6 in the pattern. I'm sure it was much more entertaining from the cheap seats, Bob may have aged a few years over the span of 3 hours.
 
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The whole point of the wooden stiffeners is to dampen out the gear "wobbles" for lack of a better term. By using sika flex I would imagine you're allowing the gear to flex away from the stiffeners, it is rubbery. It may fail under that much flexing. By using fiberglass tape you're firmly securing it and allowing it to dampen the gear.

That said, most guys I know don't use them. If you find later after flying that you need them you can add them later.

Bret you should've been at MEV the other day, I was desperately trying to break rvmills rocket 6 in the pattern. I'm sure it was much more entertaining from the cheap seats, Bob may have aged a few years over the span of 3 hours.

You F18 guys have all the fun, did you have your G suit on. We should get together with the local RV ers and do a Breakfast at the Taildragger!
 
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