Wheel Pants/Gear Leg Fairing

I’m close to making out the pants in position. So I need the pant parts ready. I did yet again an assembly on the gear and noted where my hard points are needed.

I then cut out a series of disks and glued them in place on the pants. There were 8 disks so it all took a while. I wish I’d spent longer as the hardpoint and the positions were not exact centers on those disks. In fact some of them were too far away from the pant so I made another lot of disks, some as wedges and did another glue cycle with them.

While that was curing I made up a set of pointers as you see in pic 2. These were just bolts and screws with the heads ground off and placed in the fastener fittings (nut plates and the AN4 size wheel axle). A bolt in a drill held against a big sanding disk also rotating works to make a point. I did enough for one wheel at a time. You get the pants on, lined up and give them a wack with a plastic faced hammer. Finally a fun bit. Pic 2 shows the wheel marker and the others looked pretty similar.

Pic 3 is my lining up. I used a center line in the nose and firewall and dropped a plumb bob and marked it on a bit of tape…taped to the floor. Then I measure out two feet both side and marked that. This was both nose and firewall. I used a bit of cotton stretched out and taped at both ends with some gaffer. This is what you see in pic 3. The idea is to get the nose and tail of the pants parallel with the planes center line.

Spacer disks

Marker fittings

Center lines and reference (note the cotton on the floor marking straight lines equal distance from the front and rear center line)

As the fitting is getting closer to a final placement it was time to sort out the hardware. I removed the heat shields and the pant brackets I made up and did the final smoothing of the edges. Next up was to drill a few holes for the pant screws and do the countersinking.

From here it was alodine for the four parts. Being 2024-T3 it never seems to go a nice yellow colour where as the 6061 does. I gave all the parts a while in the bath. Then I attached the 6 floating nutplates.

Pics 1-3 show them in place and bolted back with the axles. Things I’d do differently? A lot more care placing the position of the hard points on the brackets. I’m still a bit unsure how its all going to happen and that is not helping. I think I may have put one of the Y brackets around the wrong way. It doesn’t matter all that much except that I was so careful to ensure good access to the screw holes, now its not as good, and one hard point is a half inch from where I planned.

I’ve also noticed that where there is in-decision with a job, I sometimes make small mistakes no matter how careful I am and it is MUCH more fatiguing compared to a task I’m confident in.

Now I get that lesson I hope to move on from it!

Alodine and nut plates

Bracket fit

Shield fit

More checking today with the laser. I am happier than I was with the pant alignment now. I have nose and tail and the mid point very very close to where they need to sir

I have the fuselage up 1.7 degrees which I hope will be ideal for high speed cruise. The pant instructions say between 1 and 2 degrees nose up. My current EZ is around 2.4 degrees nose up at 140 knots and tends to flatten a bit as you go faster so I’m guessing at 1.7 degrees for 180 to 200 knots. Ha!

I’m getting slowly closer. Pic 3 is at a point now where I am checking the midpoints of the halves with the floor to get a zero line in cruise position. This meant that I needed to cut more off the front tire opening. Slowly I’m understanding where to herd all the cats. Once I get the right wheel at this stage I can start adding in the internal pant hard points for the fasteners.

I’m starting to see the way forward with these pants. Lots to do yet but less of a mystery now. Maybe another week? We will see. They will get done and be in the past soon enough.

Side check

1.7 degrees nose up (I have a car jack under the main wheel bow for this which you can just see in the next pic))

Getting there

While I had a 3/8″ pad on the wheel for fitting pants with a gap, I needed a smoother one that would not fall apart. This time as you see in Pic 1 I have made a smooth pad, heated it into a curve and really got it on there with a lot of duct tape. I should have done this the first time. Its a lot easier doing the multiple fitting checks with a good spacer that does not move.

Pic 2 shows that I had to solve the problem of the thin BID pants and clicos that were falling out because they had little purchase. All that was needed was some scrap glass hot glued in place and then the holes re-drilled for a stronger clico fit.

Pic 3 is rechecking the alignment of the pants as I put the new clico holes in. I was not happy with all that work I did previously trying to line these halves up. The laser and a bit of #MK1 eyeball has a much better fit now.

A careful 3/8″ pad

Hole fix so the clicos can grab better

Out with the laser!

Hang on, what about the inside bracket? I can’t use the plans one because it increases the outer clearance issues. I wanted a bracket that held the front and back halves and I did find a drawing on-line for the featherlite pants that I don’t have.

I made an approximate version of that in paper as you see in pic one. I again match drilled for the axle holes. I had made a great backing plate for the axles but that will be discarded. The 2024-T3 0.080″ stuff is good for this so that my increased width at the side is really small. If I’d gone plans bracket maybe 1/4″ or 1/2″ more which I didn’t want.

Shorted screws would work too, or would they? These are AN4-25A’s. With thin washers they show 3 threads on one side and 2 and a half threads on the other. AN4-24A’s are about a thread too short. I may cut a couple of threads off later if they are touching the pants after mounting. Its a pretty fine margin. I did not want no thread showing in the lock nuts. Not for an axle!

I was VERY careful with making these brackets so you can still get the brakes off without taking the axles off the gear leg. Thats one reason why I made them oversize, got the leg position holes in and then checked for brake screw clearances.

Pic 3 and I had a pant placed on the leg. It has a long long way to go before it is mounted correctly.

Cut outline after mounting

A reasonable fit

‘Looks OK’ but it isn’t yet

I have great axles with a AN4 size hole already tapped in the ends. They were too long however for my pants. I decided to cut them back now to help with the pant fitting.

The instructions have you make a reinforcement pad at this hole at the pant half and so I cut the axles with a bit of a space in mind. I first checked that the hole had the right tread and I used a tap to ensure I could make it a bit deeper before my cut.

You see in pic 2 that job is done. That was a careful 30 minutes and then back to fitting the pants… more hours went by but I’m getting closer. You can see a better fit in pic 3.

Original size

After the angle grinder

More fitting

I spent a crazy amount of time cutting out the first set. The second pant set was only ‘slightly’ quicker. I’m trying to make the clearances almost zero so that I can adjust it all after the pants are installed. This is a really slow job on your knees most of the time and over some days.

I’ve taped 3/8″ thick foam to the top of the wheets to get the clearance there and what happens on the sides is what happens. I’m yet to do the precision line up. I’ve also got the wheels off the ground with a car jack lifting the plane at the landing gear and a phone book for padding.

This getting the halves fitting is very challenging with my two ply ‘still floppy’ parts. I woke up this morning still running how I was going to do that in my mind. Its a problem with the clicos falling out. I might hot glue the halves together.

Doing that produces all sorts of other issues. Once it is lined up, how do I keep it there? How do I get the brackets and wheel axle in the right place, they need internal padding too. Hmmm hang on, I’d better look at that before going on.

Slowly

Slowly

Slowly

Before I went any further I though I should have the heat shields on the axles. This is in case they pushed the inside point further out and in case they produced an unseen ‘gottya’ for the pant install. They didn’t but I’m glad this step is done.

While a simple thing to protect the gear legs I went back and looked at and read every bit of info I had on these things. In the end I need to protect the legs and line of sight from the brakes is my coverage area. I also need to be careful that the shields do not interfere with brake operation.

I will later wrap the lower strut at the brake area with heat shield foil and that fiberfax stuff mentioned for the firewall. Belts and braces and all that. I do not want the gear legs getting soft on me due to heat from a hard braking episode.

I had some 0.080″ aluminium. 0.070″ would have been fine but I had none of that and a big sheet of the other. .010 is not a lot on this occasion. I first made a template out of paper adding and removing bits until I was happy. Then I match drilled the gear leg holes and then used the template to get the shape as I wanted it. It took a while.

This job is nearly done. I still have the plastic on the metal and I’ll later alodine it for good measure. Same with the brackets I’m about to make.

Paper template

2024-T3 0.08″

The second one was easier

The plans make a thing of making templates using a bit of paper or cardboard behind the wheels and noting where the tire and strut are. These get transferred to the pants to make cutting for all the fitting easier.

Well I could almost have skipped this step. When I started cutting it still took forever. We might consider these ‘guidelines’. You’d be very brave to just hack away at the pants after using these marks and expect it all to turn out well. You’d be close but we are talking small margin between pant, strut and tire.

I did it anyway (the marking, not the hacking)

Drawing it out

Marking the tire positions

More tire marking

I followed the instructions here of pre drilling the front halves for the clecos. Next up is to match these with the rear halves and drill though the clico holes.

I certainly had the tops in line. I seemed to need a bit of a twist to get the bottoms closer and they are not perfect at all. In the end I used a bit of eyeball sighting to at least make it look right. The lower bit of the rear halves seems to have a bit of a twist. Oh, I already said that.

As always I did my best and got all the cleos in. As I have only 2 ply these do not hold at all well and some of them keep falling out. I might need to put some backing pieces in later.

Pic 3 shows I have two pants! I spent a bit of time as well making up the rigging jigs according to the plans as you see in the shot. That was the only easy bit so far.

Using a ‘square bay’

Clicos in place

I made some jigs too (which I never used!)

There is quite the procedure for finding the center of the pants and drawing lines. This is needed to line the two halves up. Well I spent painful hours trying to get it right. Nothing is perfectly square. I hope I got it OK on the tops ends and points of maximum pressure at the front. The 2 ply pant parts are pretty ‘floppy’

If I have it wrong the pants will produce more drag than they could have.

Getting everything perfectly straight is not my strong point. I used Wayne Hick’s instructions and he still may have done a better job that I have. That said, I do have lines on the 4 pant halves.

Are two squares better than one?

Doing my best

This point was easier to find

Well the plans say to square off the ends. I am following Gary Hertzlers instructions. He designed the shape of the pants. I’m also using a couple of Cozy websites that have more details on pant installation, based on Garys words however. Wayne Hicks has the one I used most and I think it is excellent. What a great builder.

So I squared the things off. In retrospect this step is not needed now. My pants will not be a perfectly even fit so I’ll trim the join area underlap later. I guess you do need to square up the front halves on the pants to at least have a ‘baseline’.

One thing about these ‘James’ pants. They are designed for the RV aircraft. Our canards have the gear leg entering more at the side so that the pant is offset too near the outer edge. Which means your wheel is right up to the side of the pant with no clearance at all! There are a couple of fixes for us. One is to make the pants 2.5″ wider by cutting down the middle and adding foam and then glass and then a clean up. The pants are so big now I didn’t want to go that way.

The second method I saw on a Cozy site where you reshape the outside of the pants later to go straight down instead of curving in. I like that approach better. I’m also adding a bit of my own fix. If I minimise the hardware on the inside of the pant, the outside will not be quite as far over. This means a different attachment plan to Gary Hertzlers instructions. Gary is one of our EZ gurus, so I do this at my own risk.

Getting it level

They ‘sort of’ go together

Looks good – at a distance