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Wheelpant Woes

AviatorJ

Well Known Member
I'm struggling a bit on comprehending on how the wheel pants should be aligned. I've read a handful of build logs which have been great on talking about the procedure to align them but I'm confused on how they should be in flight.

So for alignment is the general idea that in flight they in parallel and inline with both the planes longitude and vertical axis? However in terms of lateral axis they are rolled to match the profile of the tire, so a bit toe'd in?

If thats the case then how do you determine straight and level with the plane up on jacks? I put a leveling rail under the mid cabin but that's not really exactly flat and bends just a bit. So should I do that over the top of the spar or is there another method to do this? Thanks!
 
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I leveled mine by placing a large, straight board across the middle of the door opening. I then zeroed my smart level on the floor and did one axis then the other going back and forth between axis (zeroing each time) to ensure that by leveling one I didn't mess up the other.

I get confused with the axis terminology because I think of motion around a given axis, like when flying, and not the axis plane itself in relation to a fixed object. Having said that, after jacking and leveling the airplane, the pant's vertical axis should be set parallel to the tire's vertical axis like in this pic.

35217270563_9471f047d5_m.jpg


Everything else is set in reference to the level aircraft and not the tire. You make the pants parallel to the aircraft's center line (and the air flow) by pivoting the pants left or right around the spacer sitting on the tire so that the ref marks on the very front and rear of the pants are the same lateral distance from the centerline. Similarly you insure the pants are level up and down by making sure those same ref marks are the same distance above the floor. This is hard to describe in words but is easier, at least for me as a visual learner, in practice.
 
Pants

I spent many, many hours on this! I ended up raising the aircraft per the plans then leveling the aircraft in pitch using a digital level on the door jamb per the plans. Then I leveled it roll using a digital level across the left and right door jambs.

Next, I dropped plumb bobs from the center of the firewall to the floor and from the center of the tail post to the floor.

Using a Dewwalt Laser Level, I marked a line between the two plumb bobs on the floor. Offsetting this centerline to near each main gear gave me a convenient yaw reference.

Then came the nightmare! Trying to POSITION AND HOLD a 3 dimensional teardrop (with no straight edges) with respect to pitch, roll, and yaw in 3 dimensional space...what a PITA.

I ended up building a jig to hold the pants where they needed to be, and verified all measurements with multiple carpenter squares and numerous measurements.

What I ended up with is with the aircraft level and wheels just off the ground, per the plans, the pants are level in pitch, parallel to the centerline of the aircraft in yaw, and parallel to the face of the wheel in roll. So, yes, the pants are rolled slightly when the aircraft is off the ground.

If you want to see the pictures of how I set it up, go to mykitlog.com and search for Sunman, Indiana. I am the only one here building an RV-10...:D
 
Laser Level
Those are great for jobs like that, and also checking toe-in-toe out. For those who don't know, they project a bright red line on the hangar floor (or anywhere else).

As far as holding a 3-dimensional object, I had a similar situation with the canopy of my plane. What I did was make a particle board frame that fit loosely over the part, and used bondo to temporarily hold it inside the frame. When I was done fitting, the bondo just popped off the fiberglass. I think hot glue would work also, but might be more difficult to remove. It seems like a similar technique would work on wheel pants.
 
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Bondo and small assorted sizes of wood blocks work great to hold things in position while fitting and aligning the wheel fairings .
 
The bottom of the door frame is the "In Flight Level" reference plane. That should be level to the floor, then you can use the floor as the reference plane.
 
I appreciate the feedback and glad I'm not the only one who is struggling with this. I'll measure off the door frame to get it level, I'm in the process of building a couple of those bottle jacks to lift the plane.

Also I thought about a laser level but not sure which to get. Do I need something fancy or would one of those basic $60 jobs that just get you vertical and horizontal references work?
 
I leveled mine by placing a large, straight board across the middle of the door opening. I then zeroed my smart level on the floor and did one axis then the other going back and forth between axis (zeroing each time) to ensure that by leveling one I didn't mess up the other.

I get confused with the axis terminology because I think of motion around a given axis, like when flying, and not the axis plane itself in relation to a fixed object. Having said that, after jacking and leveling the airplane, the pant's vertical axis should be set parallel to the tire's vertical axis like in this pic.

35217270563_9471f047d5_m.jpg


Everything else is set in reference to the level aircraft and not the tire. You make the pants parallel to the aircraft's center line (and the air flow) by pivoting the pants left or right around the spacer sitting on the tire so that the ref marks on the very front and rear of the pants are the same lateral distance from the centerline. Similarly you insure the pants are level up and down by making sure those same ref marks are the same distance above the floor. This is hard to describe in words but is easier, at least for me as a visual learner, in practice.

Simple and to the point.....
Excellent explanation.
 
In another thread yesterday

I read about some fellow doing his pant alignment with the gear on the ground, in squat. Said his speed increase after fairing install was fine in his opinion.

Makes one wonder how much difference it ultimately makes to go to the trouble of jacking the plane to do the pant and fairing alignment. Any speculators / data?
 
There is in my opinion no need to lift the plane. You do this part with the wings off. Just go to the tail, jerk it upwards ads see how the wheels will slide inwards ( toe in ) slightly. Then follow the plans. It should be level or or close to level as possible. Looking from the front you align it with the tire threads and the trailing edges using lines marked on the floor.
 
I appreciate the feedback and glad I'm not the only one who is struggling with this. I'll measure off the door frame to get it level, I'm in the process of building a couple of those bottle jacks to lift the plane.

Also I thought about a laser level but not sure which to get. Do I need something fancy or would one of those basic $60 jobs that just get you vertical and horizontal references work?

Cheap $60 dollar job will do - very handy. In this case, a line projected on the floor is super useful for the wheels. Easy to use. Will come in handy.
 
The laser level is a game changer!



I went back and more or less started over on redrawing all the reference marks (ie the picture above). I've also used them substantially in in getting the pants all aligned. So great tip!

Question though is I over trimmed the inside of each wheel pant there when I tighten everything down the opening for the tires on one side is 1/4 too big than the suggest 5/8ths min. My thought is to put 2 layers of clothe on the inside and make up for the area I cut out. Then just micro over and smooth it all out. Any issue with this?
 
I read about some fellow doing his pant alignment with the gear on the ground, in squat. Said his speed increase after fairing install was fine in his opinion.

Makes one wonder how much difference it ultimately makes to go to the trouble of jacking the plane to do the pant and fairing alignment. Any speculators / data?

Don't know about the 10's gear, but the round leg planes (mine's a -7) will have the gear sweep both out and back (angling the pant nose down) when loaded on the ground. If you set the pant up level while loaded on the ground, in the air, the pant will be flying at a higher than ideal AOA (and possibly yawed, as well). Now, whether you can detect the extra drag...I don't know. But if there's any pant yaw in the mix, you almost certainly will feel the effects.

I used a Harbor Freight lasar to get the 'tilt' to match the centerline of the tire tread. I set up the lasar to paint a line around the tread (looking down), then added the pant & adjusted until I got the pant's center line under the lasar. Or at least what I hope was the pant's center line. That was the biggest uncertainty of the process for me. Would have been nice if there were a witness line etched into the pant mold; would be easy enough to remove it while filling all the pinholes.

Charlie
 
FWIW

Here's a little adjustable jig I made that helped hold the back end of the pant in position:

2d9ptug.jpg


The V notched piece of wood should look familiar...Laser level and pencil marks on the floor did the rest.

==dave==
N102FM
 
Good news is my main pants are almost done, they're on the garage floor now with a few epoxy skim coats, little bit of sanding and some nut plates and I'm done.

Bad news is I'm having issues with the initial trimming of the nose pant. I've taken about "1/8 off and it doesn't seem to line up. Is there some trick to this? I read that the top won't always line up... before I butcher this anyone have any suggestions?
 
By the lack of responses I assumed there was no 'trick' to get this done right. I decided to just jump into it and see what I could do. 4 hours later this is what I ended up with...



My method was to ignore the front cap piece and see how easy it was to fit the rear and get it somewhat in place. After a few hours messing with lasers, squares, drimels and sanding blocks I had it more or less in position.

Then I took it off and put blue masking tape on the inside flange. Then I placed the top on and used a laser to get it aligned and then with the lights out and flashlight was able to see where the blue taped stoped and where I needed to sand. After an hour or so of this I then had the top cleco'd on. Then I put the rear half back on and worked the sanding for the gear leg until I got to whats in the picture.

Decided to call it a day and hit it up again fresh another time. I'll need to level the plane out, ensure the pant is horizontal and vertically aligned and then get to the drilling. Should work out fine but what a pain these wheel pants are...
 
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