Cutting a perfectly good cowl

With the Skybolts and horizontal split line with hinges complete.. I moved on to fitting the two fairing pieces that come with the showplanes cowl. I trimmed the aft fairing to have 3/4″ flanges and then marked the center point. Additional trimming was needed to clear the front gear leg to get the aft fairing into position. 3 holes were drilled into the bottom of the fuselage for now to hold this in place. Later I will install rivets for screws to hold this into position.

Once you’re happy with this you place the lower cowl back on and drill a couple of holes on each side to lock in the position of the aft fairing to the cowling.

Aft fairing in place and cleco’ed to the lower cowling

Side view of the aft fairing.

Then with the aft fairing and lower cowling back on the bench. The forward faring was placed into position and trimmed as needed to get a good fit with the forward fairing. Once satisfied, 3 holes were drilled on each side to hold the forward and aft fairing together.

The aft fairing was put back into place on the fuse, and the forward fairing was trimmed to clear the engine mount tubes until the drill holes on each side lined up.

Front and Aft Fairing.
Front fairing fitting around the tube just below the donuts.

Once that was done, the lower cowl was put back into place to verify and adjust fit. The forward fairing needs to lay flat across the area of the cowling that has no honeycombed and be as centered as possible.

A decent fit to cowl.

I then had to add some fiberglass back to the slot that I had cut to get the lower cowl into position. I was careful to not cut too much when I did this originally, but I still cut a little too much. I sanded the edges at an angle to create a scarf joint with a fiberglass layup over the small area that needed to be added back. I put some peel ply on and let it cure overnight.

Adding material back to the nose gear slot.

The end result was pretty good.. There was a small gap in the rounded edge, which I later filled in with epoxy and let cure and sanded down.

I then sanded the inside of the cowl at the scarf joint that I added. You can see that below just about done.

Sanding the scarf joint.

I then put the lower cowl onto some cinder blocks so I could level it as needed. I used the laser level to make sure the intakes were level horizontally, which the vertical was aligned to the center line of the lower cowl.

The center line was marked with a sharpie as well as some blue painters tape. I also marked out the locations of 8 holes to drill into the forward fairing that will hold the cowl to that fairing with screws. I also mapped out 8 additional holes that mostly go through the aft fairing into the cowling.

The lower cowling was placed back on and the hole locations were match drilled to the forward fairing

Then the big moment came.. Using a diamond cutting wheel on a dremel tool to cut the lower cowling in half!

For whatever reason, despite having a plan… it seemed scary to me to cut this perfectly good cowling like this…

The cut will later be rejoined with another hinge pin like the horizontal sides. Skybolts could also be used here, but I opted for a hinge for a better look.

To prep for that hinge.. I marked out a 1.5″ wide rectangular area at the split point. I again used the diamond wheel on the dremel tool to just cut through the inner layer of fiberglass as shown below.

Cutting the inner fiberglass only. prepping for a flange buildup.

I then used a flat blade on a Dremel multi max oscillating tool to separate the honeycomb material from the inner layer of fiberglass. Below you can see me mostly done separating the fiberglass layer from the honeycomb.

Inner layer of Fiberglass removed.

I then used a chisel to carefully remove the honeycomb material. You have to use caution as the remaining fiberglass outer layer is very thin.

Using a chisel to remove honeycomb material.
Done removing honeycomb. Some additional sanding to be done still.

I then cut some strips of 9 oz. fiberglass to build up a flange where the structural material was just removed. I decided to use 6 layers of cloth for this. The end result was a thickness consistent with the other areas of the cowl that don’t have honeycomb.

6 layers of cloth in place
peel ply added.

Then after curing overnight you can see the results of the flange.

Next up will be re-combining what was just cut in half…

Cowling part 2

Indirect lighting from inside the cowl when drilling the skybolts can really misalign you. I started to also trace the inside of the hole with a fine point sharpie to get an even better view of exactly where the hole is and also use that to gauge walking the step bit in one direction or the other.

Even with that I’m ever so slightly off, although not by enough to matter.

Below is a look down the left side at the firewall with some skybolts installed. Here you can see my small light that I used taped in place to more directly illuminate the hole.

I then used a laser level to mark and trim the top cowling first. the 12″ Permagrit sanding block was used after getting close with a diamond cutoff wheel on the dremel tool.

I then used the top cut to mark out the bottom cowl cut location.

I trimmed close with the dremel tool and then used the sanding block to get it as close to perfect as possible.

Once that was done, I marked the location of the hinge pin covers from Aerosport. Location was based on the plans.

With the hinge pin covers located, I then got to installing the side hinges. I shifted the hinge downward so the eyelids won’t show. I used a AN257-P3 length hinge on the bottom cowl and a -P4 length hinge on the top cowl to get enough flange to maintain edge distances on both the hinge and the fiberglass.

Left side bottom drilled

The same was done on the right side.

Use of the laser level to get the rivets all aligned down the hinge.

One thing I did was to drill a couple of turns with a hand drill in each marked rivet location prior to using a higher speed air drill. This created a slight dimple so the high speed drill wouldn’t wander once I was drilling through. Very little pressure was used and just let the drill bit do the work.

A view of the right side done and hinge pin in place (not yet cut to length)

I then cut out the spot where the aerosport hinge pin cover template was to be placed. I got close and then used a file to get it to fit tightly in the cut hole.

I then followed the Aerosport directions and added tape and wax to the template along with putting a micro slurry on the inside of the area. I also wetted out 4 layers of 9 Oz fiberglass and placed it on the inside. Once cured overnight, I used a thin woodworking saw I had from a previous task of cutting casings to cut through the Aerosport template and separate the cowl halves. I will say that the very front part where the 2 cowl halves overlap gave me a lot of trouble as I bonded them together and it took a relatively long time to get them apart and left me very frustrated. There is not a lot of room to work either to try to use small files etc.. to chip away at the bond. So use caution when doing this with a Showplanes cowl.. It’s pretty easy to waste 3-4 hours hacking away to get them apart again..

The end result of the recessed area I built up in order to install nut plates for the cover.

The center area of the added fiberglass was cut out to allow the pin insertion into the hinge.

Finally the hinge pin cover was test fit into place. This is at such an angle that if the hinge pin were to start to wander forward with vibration, it would stop the pin from working its way further out as the pin would hit this metal cover. From all accounts that I’ve seen.. the pin doesn’t typically do that anyways, but it would only be allowed to move approx. 1″ forward worst case.

Cowling and skybolts

The Showplanes cowl is one of the last major fiberglass pieces to be worked on. The instructions basically tell you to follow Van’s instructions with a couple of exceptions. So I got to putting the upper and lower halves together and marking the upper cowling for trimming to meet the ratios needed to make a perfect circle for the spinner/prop as well as the air inlets on either side. Here you can see the mark made using a straightedge.

Staightedge used to mark uniformly across the top cowl.

Double checking that the radius is 7.5″ (15″ diameter)

Getting close now with some trimming

Using the prop tool to double check the prop area circle.

You then clamp things in place and drill holes in the flanges to hold this position.

I chose to just do a single cleco on either side of the inlets as well as one in the flange between the inlets and the prop area.

I then used a laser level to mark the center of the bottom cowling to create a cutout for the nose wheel gear leg.

Marking either side of the centerline based on Van’s dimensions for width.

I then used a dremel tool to cut the slot. I estimated the length to cut and then slowly increased 1″ deeper at a time until I was at the bare minimum to get the lower cowling into position. Below is the initial length cut.. I cut a few more inches deeper. My plan is to split this lower cowl into 2 halves to accommodate the 3 bladed prop and I’d like to keep as much original material in this area as possible.

I put the top cowling into position and used a laser level to get it level (after leveling the aircraft) The cowl tool has 3/32″ holes all along the surface to facilitate holding the cowling into place in a fixed location so it doesn’t move during trimming.

Lining up the center line both fore and aft.

With this “extended” hub prop, the cowling sits far enough forward that there is minimal trimming required at the firewall.

Both top and bottom in place

Then starts the task of trimming to the firewall. I used a light on the inside to mark the location of the skin. You then trim 15″ on either side of the center line along the top only. I used a cut off wheel on the dremel tool and left it 2-3mm short.. The 12″ Permagrit sanding block was used for the remainder.. Once this center section is trimmed, the cowl falls down and aft allowing you to get a more accurate trim line for the sides.

Trimming the top center section.
All trimmed

I utilized a couple of clecos in the rivet holes of the skybolts to hold the upper cowling in place so it won’t move. I’ll fill these holes in later.

Then starts the task of installing the skybolts and drilling holes in the cowling. I started with a method that I saw Mark use. Using cardboard to drill a hole, I used a small scrap of fiberglass trimmed from the cowl to mock its thickness, and the cleco adapters that came with the kit to mark where the center of the hole was. The cardboard was taped into place so it can be flipped up, the cowl put into place, and flipped back down to drill an accurate hole.

The cowl was then put into place and the hole was drilled.. However, It didn’t really seem to work that well for me. Probably the tolerance of the hole in the cardboard not being perfect.

The first Skybolt installed.

What I found was that the light inside the cowling wasn’t direct enough and caused some incorrect alignments when marking the hole and drilling. So I taped a small light into the bottom of the cleco adapter to shine directly on the cowl while it was in position. This was used to drill the remaining holes which were more accurate.

2 or 3 skybolts in place

I then worked one hole at a time from top center downwards towards the sides. Mark and drill the hole to 15/32″, insert the grommet and stud, rivet the receptacle in place, place the cowl back on and test fit the new Skybolt.

More to come..

Prop Woes

Some time back, prior to really needing to order a prop.. I had done a bunch of research on the options.. There’s the stock Hartzell 2 blade metal prop, and various other 2 and 3 bladed props from the likes of Hartzell, MT, and Whirlwind. I put together the following table based on the options I found.

BrandModelCostNumber bladesBlade lengthSpinner sizeWeight with spinnerMakeupTBO
MTPROP MTV12B/193-531385037643Composite6 yrs/1800hrs
MTMTV915900376or7854.9Composite6 yrs/2400hrs
HartzellPROP C2YR-1BFP/F8068D902528055.6metal6 yr/2400 hr
HartzellPROP C3Y1R-1N/N7605C SPINNER C-4582-P2035537867.5composite
Whirl Wind77HRT1210027743Composite6 yr/800 hr
Whirl Wind375HRT1435537555Composite6 yr/800 hr
Whirl Wind300-771250037742Composite6yr/800hr
RV-10 Prop options

While the stock 2 blade is widely regarded as the fastest prop, I felt the 3 blade was a better look for the Showplanes cowling I had already chosen. It also is much smoother and has a shorter blade length giving more clearance there.. Of course that doesn’t go without consequences largely in removing the lower cowling. The plan there is to split the lower cowl into two halves like several others have done. Just more fiberglass work.. 🙂

I saw several of the recent builders go with the Whirlwind 375HRT prop. I had spoken with them and was also planning on going in that direction. The main downside is the lower TBO times, but at about 100 hours per year.. I’d likely hit the same time limit prior to the hours limit, which is the same as the MT and Hartzell.

Fast forward to prop order time, which I had delayed a bit due to the 4-6 week lead times I was consistently given by Whirlwind. Guess what.. They no longer are selling that prop (support only) in favor of their newest 300-77 prop. Which is all fine and everything, but the weight reduction (of all things) was concerning.

Why concerning, you ask? Well weight and balance concerning.. The RV-10’s CG moves aft as you burn gas.. Ideally, you’d like to have your empty weight as close to the forward CG limit as possible so as to allow for max carrying capability and gas burn as you go longer distances, even if that means throwing in some ballast when solo. Having a prop that is over 10 lbs lighter out front combined with my Air Conditioning (mostly CG neutral, but ever so slightly aft), an O2 bottle, and a standard technology battery (read heavy) behind the baggage bulkhead, I was concerned.

It’s difficult to know exactly what my empty weight will be, but I grabbed 2-3 samples of what I could find and was provided by other builders. I did a bunch of playing with W&B by estimating the arm of the prop (approx at the hub) at 32.7″ from this picture:

I did that by measuring the scale with a ruler between 25″ and 50″ and then calculating the number of inches per 1/32″ and figuring out the distance to add to 25″ to get to a line drawn through the prop location.. I felt that was good enough for my comparison purposes..

I then found an example W&B spreadsheet online that had lots of weight scenarios listed for that given plane. I modified the spreadsheet to subtract out the weight of the prop that plane had on it and added back in the WhirlWind Prop weight. Here is the stock aircraft examples of empty and gross weight.

   AIRCRAFT EMPTY  
       
Location  ARMWEIGHT (LB)WEIGHT (KG)MOMENT
Left Main Wheel  124.31621282.2777197
Right Main Wheel  124.44608276.3675660
Nose Wheel  50.44328149.0916544
Main Fuel Tanks0gallons108.9  0
Pilot  114.58  0
Copilot  114.58  0
Passenger  151.26  0
Passenger  151.26  0
Baggage  173.5  0
Survival Gear  173.5  0
Remove stock prop  32.70 0
Add WW Prop  32.70 0
       
  Totals 1557708169400
       
  C of G Location 108.799  
  Forward Limit 107.80  
  Aft Limit 116.24  
       
   AIRCRAFT AT GROSS  
       
Location  ARMWEIGHT (LB)WEIGHT (KG)MOMENT
Left Main Wheel  124.31621282.2777197
Right Main Wheel  124.44608276.3675660
Nose Wheel  50.44328149.0916544
Main Fuel Tanks60gallons108.9360 39204
Pilot  114.5818680.0021312
Copilot  114.5817680.0020166
Passenger  151.2617680.0026622
Passenger  151.2617680.0026622
Baggage  173.559 10237
Survival Gear  173.510 1735
Remove stock prop  32.70 0
Add WW Prop  32.70 0
       
  Totals 27001028315297
       
  C of G Location 116.777  
  Forward Limit 107.80  
  Aft Limit 116.24  

So about 1″ aft of forward limit empty and slightly out of CG aft loaded up with full fuel and passenger weight somewhat equally spread around.

Now comes the effect of doing the prop swap:

   AIRCRAFT EMPTY  
       
Location  ARMWEIGHT (LB)WEIGHT (KG)MOMENT
Left Main Wheel  124.31621282.2777197
Right Main Wheel  124.44608276.3675660
Nose Wheel  50.44328149.0916544
Main Fuel Tanks0gallons108.9  0
Pilot  114.58  0
Copilot  114.58  0
Passenger  151.26  0
Passenger  151.26  0
Baggage  173.5  0
Survival Gear  173.5  0
Remove stock prop  32.7-55.6 -1818
Add WW Prop  32.742 1373
       
  Totals 1543708168956
       
  C of G Location 109.470  
  Forward Limit 107.80  
  Aft Limit 116.24  
       
   AIRCRAFT AT GROSS  
       
Location  ARMWEIGHT (LB)WEIGHT (KG)MOMENT
Left Main Wheel  124.31621282.2777197
Right Main Wheel  124.44608276.3675660
Nose Wheel  50.44328149.0916544
Main Fuel Tanks60gallons108.9360 39204
Pilot  114.5818680.0021312
Copilot  114.5817680.0020166
Passenger  151.2617680.0026622
Passenger  151.2617680.0026622
Baggage  173.559 10237
Survival Gear  173.510 1735
Remove stock prop  32.7-55.6 -1818
Add WW Prop  32.742 1373
       
  Totals 26861028314853
       
  C of G Location 117.202  
  Forward Limit 107.80  
  Aft Limit 116.24  

Note that empty, it moved the CG aft by 0.671″ and by 0.426″ in the gross case.

I, of course, ran a bunch of other configs including our Family profile (Assuming Declan fully grown) and it would all be okay.. but low on fuel you can actually get slightly aft of the limit with lighter prop. All would be fine with the weight of the standard prop. I won’t bore you with several tabs of spreadsheet data I played with here.. 🙂

All of this further reinforced the need to find a prop that was close to the stock 2 bladed prop for piece of mind. That left me with 2 choices.. Hartzell 3 blade (super expensive) or the MT MTV-9 prop..

There were a couple of other builders that have used this prop. Van’s typically recommends the MTV-12. One of the main reasons they used it was the max HP rating of the MTV-12 is around 300HP, and they had similar engines to me.. meaning cylinders ported and polished, cold air induction, and higher compression ratios.. MT suggests the MTV-9 for these applications as it can handle significantly more HP (thus the extra weight). In addition MT says that there is no issue using electronic ignition with this prop at my approx HP. (they didn’t support doing that with the MTV-12, even though I know others have done it). So all of that plus the weight that is very close to the Stock 2-blade and I decided to go with it. I placed an order for the MTV-9-B/198/52 with nickel leading edges in a matte black with white tips configuration. They also suggested this spinner, which I passed by Bryan at Showplanes, and he thought it would work fine.

P-810-5 Spinner.

The issue came with the 148mm prop flange to aft spinner dimension, which I was asked about and didn’t think it would be an issue. Especially seeing Bryan said it would be okay and I know other RV-10 builders that have used this prop.

Until it was an issue..

I bought the cowl installation tool from Flyboy accessories to place the cowl ahead of getting the prop. It is well designed and provides an adjustable 15″ wheel that serves to set the cowl back from the spinner assembly.

I set the spacing to 148mm minus about a 1/4″ gap. Placed the upper cowl in position.

And DoH! the cowling is so far forward it doesn’t even reach the firewall.

I contacted my MT guy and described the issue and to see if they might have any other spinner/hub setups that might work better for me. In the meantime I mulled over what to do.. I had heard of another builder using the Hartzell 3 bladed prop with an I-hub config which pushes the spacing out enough to fit the AC compressor without having to cut and bump out the cowling. I got some info on that as an option.. I also contemplated what would happen if I cancelled my MT order.. Either lose some/all deposit money or continue with the purchase and try to sell it..

MT got back to me with a spinner specification sheet. I used the info I got about the Hartzell I hub spacing and did some mock ups and measuring.. I ended up getting a range of prop flange to aft spinner measurements that matched the Hartzell I hub design at the minimum side and a measurement as far forward as possible with almost no cowling overlap onto the firewall at the max side. I filled out their form and asked if there was anything off the shelf that would work.. I came up with somewhere between 69.3mm and 82mm would work for me.

A couple of days later engineering came back with this .. A P-810-3 spinner with 75mm spacing. It’ll work!!! What a relief..

P-810-3 Spinner

I mocked this distance up and checked the spacing of the AC compressor up front with the lower cowl roughly in place.. There is plenty of room to not have to do any lower cowl modifications for the compressor. Win win!

I told MT that it would work. A change order was put in with no anticipated delays seeing I’m still far enough out in production. I’ve been able to continue forward with the cowling install now that the spacing is known.

I will say that I’ve encountered a bunch of negativity about MT and using their props along my research. While I agree that might become true with months of delays in the case of something catastrophic that needs to go back to Germany to get fixed. For most run of the mill things it shouldn’t ever be an issue (at least I hope not). The local guys are easy to work with and bend over backwards to make things right. I also have a certified MT service shop relatively nearby in CT that I could drive to if need be. Thus far, I’m impressed with MT.

Sorry for the long post… it’s been a few months in the making.

Engine is Hung!

Prior to hanging the engine a few odds and ends needed to be completed which are just easier to do beforehand.

One of those things was adding an angle to the top of the oil cooler mount for the oversized oil cooler. The oil cooler itself needed to have some of its flanges cut to fit around the engine mounts.. Then the angle was cut to length and riveted to the the oil cooler mount. I bolted the bottom bolts into place and drilled holes into the angle for the top 3 bolts.

The end result after ordering long bolts and making some compression tubes to the right length with washers.

I also needed to safety wire the coil pack mounts to the mag cover plates.

Then came time to install the engine. I used the bucket forks and my tractor to lift the pallet up high enough to get the hoists legs under it.

Then with the hoist connected, I unbolted the engine ears and flywheel from the pallet and lifted the engine up.

The first 2 bolts (top) are the easy ones..

Then it’s a matter of getting the 3rd bolt in, which was a little trickier, but not bad.. The 4th bolt took a bit to get lined up… after a bunch of playing I was able to get the bolt started through the hole and a socket to keep threading it in. Then the engine hoist was removed..

A couple of pics of me with the engine..

Nose wheel and leg fairing

This section is very similar to the main gear fairings in that you find the center point of the aft point of the fairing, extend this centerline to the front of the rear pant, then put the 2 halves together and drill #40 holes along the flange at the specified distances. I used a piece of tape with the distances marked out and taped it along the fairings to mark the drill locations. You then use the same “V” wedge that was used on the main gear to help prop the fairing up so the height of the aft center point is a specific distance above the table. This measurement was then transfered to the front using a laser level and double checking with a square.

It’s then time to start working on fitting the faring to the nosewheel. One thing that I did that wasn’t outlined in the plans was to mark the location of the nose fork on both sides and extend those line rearward.. As you can tell by the tape and multiple lines, this did take a couple of iterations to get right. I ended up using a laser level to mark them after aligning the beam with the forks. A wooden spacer is also taped to the top of the tire.

I then marked the center point between the 2 extended nose fork lines and used that location, along with my laser level to make sure that the fairing was always inline with the tire. I’ve still got the plane up on jacks and there is no weight on the front tire, but it’s on the ground enough to not allow it to swivel.. So this mark shouldn’t change as I proceed.

Aligning the faring to the centerline of the nose wheel.

I reused the “V” wedge that I had made and repurposed it to hold the center point of the fairing at the proper height from the floor. Very similar to the jig I used for the main gear. Later, I will cut the V wedge in half and use it on both the front and aft holes of the fairing.

I then followed the plans to drill a 1.5″ hole into the front fairing and trim the tangent lines to allow clearance for the nose gear leg. Once that was done, I was able to file a little bit more along the edges and get the front re-cleco’ed to the rear.

Front fairing mated up with rear fairing

Then after making sure the front and aft locations of the fairing were at the proper height from the floor, you move on to drilling the screw holes into the fairings for the fairing brackets. These ones seemed to be more of a pain compared to the main gear as I had a hard time getting a light from the inside to cast a shadow that I could see on the opaque fairing.

Fairing bracket holes drilled (on left side)

Once again you repeat the main gear procedures for squirting a flox/cabo mixture around the fairing brackets and screws to build up the area inside. I, once again, drilled small holes around the perimeter of the screw hole and used a syringe to squirt in the mixture. Below is a shot of the fairing bracket screwed into place and the hole drilled for a nose-wheel tug to connect onto the bolt location.

Fairing bracket screwed into place.
Outside look at the fairing.

The 2 halves are then joined using screws after final drilling, countersinking, and installing nutplates.

Nosewheel in place all screwed together
Closeup of the tug access hole to the nosewheel bolt.

I also decided to use these metal tug guards https://www.flyboyaccessories.com/product-p/73301.htm I recently saw come up for sale. This will help protect the fiberglass fairing and the paint job from getting all dinged up when trying to connect and disconnect a tug/towbar. Might as well install them now while I’m working on these fairings. These were matched drilled to the supplied backing plate. All that’s left now is to countersink, spread some flox/cabo on the backing plate and rivet them in place.

I then set out to get the nosewheel gear fairing going. These are also similar to the main gear leg fairings. A template is used to cut the fore and aft edges and also the U shaped cutout . Here you see me cutting away a slot for a hose clamp by first drilling 2 holes and then removing the material between the holes on the tangent lines.

Start by drilling holes at the ends.
Then remove the material between the holes.

The fairing was then put into position. Some additional trimming was needed at the interface to the nosewheel fairing, and some more still needs to be done, but this is close enough to start on the hinge along the aft edge.

Test fit of leg fairing.
Pretty close trim.. still needs some more trimming/sanding to allow nosewheel to caster around it.

I’ll need to final trim this after I take the plane off of the jacks, as I’m not able to swivel the nosewheel just yet without worrying about the plane falling off the jacks.

Intersection Fairings

As I previously mentioned, a result of splitting the lower intersection fairings and bonding them to the wheel pants has some implications. It’s important to not allow airflow to get underneath the rear fairing half. If that were to happen, it would rip it right off the airplane. So I took some scrap material from cutting the gear leg fairings to use as a flange for the rear half. I cut about a 1″ piece and let approx. 3/8″ of a flange protrude. On a couple of the curved areas, I used a heat gun to contour it to the intersection fairing.

Flange in place

Below you can see both flanges in place and taped up so that no epoxy sticks to them.

I then laid up several layers of fiberglass cloth over the flange and attaching to the forward intersection fairing. This essentially will create a :”tab” for the flange to mate to and keep both the forward and aft sections together.

Another angle of the fiberglass layup.
Curing.

Once that was cured, I separated the two halves and permanently bonded the flanges in place with flox and cabo.

Flanges bonded in place.

A couple of shots of the resultant tab that the flange sits in (prior to any trimming.)

This should provide a solid interface between the forward and aft intersection fairings at the split.

Leg and Intersection Fairings

I didn’t take any pictures of the start of this process, but you basically cut a paper template out of the plans and tape it to the fairings as instructed to mark and make the top and bottom cuts that align to the bottom of the fuselage and the wheel pant. I then placed them on the gear legs to test the fit.

Pretty good initial cut against the wheel pant.

You then cut the piano hinge to length and start marking where it will go to hold the trailing edge together. One slight deviation from the plans was to mark out the drill holes on the hinge and actually drill them with a 3/32″ drill ahead of time. The plans want you to drill through from the outside, but that goes back to the times when these fairings weren’t gel coated and were transparent. I then used the undersized holes in the hinge to match drill #40 into the fairing from the inside with a right angle drill.

First hinge mostly match drilled
Right angle drill used from the inside to match drill the hinge
Countersinking for flush rivets

You then re-install the leg fairings and insert the hinge pin, which is sort of a PITA. Once that task was over, the plans walk you through how to align the fairings properly. Getting this wrong can cause yaw, so you want them as perfectly aligned as you can. The plans have you wrap a string around the leg faring and clamp it to the step. I also feel that that plans walk you through placing a displaced centerline mark at a random location.. I basically reused the string I already had on the floor from the wheel pant install. The issue I ran into was my location.. and just some random location, as mentioned in the plans, isn’t the correct location when the string is perfectly level. So my advice would be to level the string, then use a plumb bob to mark the forward location of the string on the floor. Then duplicate the measurement from the airplane center line behind the step. Place the string that is the displaced centerline of the aircraft and use a plum bob to transfer the location to the step. You then move the aft part of the string to this mark on the step so the string ends up both level and parallel to the aircraft centerline.

Getting the string in place
Using a laser level to verify the string is perfectly level.
End result of the string level and parallel to the Center Line

You then adjust the rotation of the fairing until there is an equal distance between the trailing edge of the fairing and each side of the string.

Proper alignment.

To lock this positioning in place, you move on to install the intersection fairings. I used the intersection fairings from RVBits instead of the stock ones, which need lots more work. The lower left fairing was slid on using care to not change the alignment, which of course was re-checked multiple times.

Lower intersection fairing in place.
Front view.

I’ve decided to bond the lower intersection fairings directly to the wheel pant instead of using more screws to hold them in place. Doing this will require cutting these intersection fairings where the wheel pants separate from each other. It will also require me to add a flange onto the rear pieces so they stay locked in place under the front pieces with no way to get airflow under them.

I drilled a bunch of holes in prep to bond the 2 surfaces together.

The below picture was taken after I started taking clecos out, but I used a laser level to mark the fairing at the wheel pant split. I also decided to add a couple of additional clecos up at the top of the intersection fairing on either side of the cut. I did the same thing for the inside line as well (not visible here).

Cut line marked.

I then took things apart, cut the intersection fairing taped up the leg fairing so things wouldn’t stick together, and mixed up an epoxy/flox/cabo mixture putting things back together and letting them cure overnight.

All put back together and curing overnight.

The next morning I took the wheel pants off and the separation of the intersection fairings worked out well as shown below..

Rear fairing.
Front fairing.

A couple of pictures of the wheel pant put back together.

I then placed and drilled a small hole for clecos (for now) and placed the upper intersection fairing into position. This will later also attach to the wing root area.

Wheel Pants Part 2

With the jig leveled off and touching the bottom of the tire, the rear of the gear pant was put into place to trim a small amount to accommodate the gear leg. You continue trimming until the gear fairing extension hole is coincident with the aft “step” of the flange on the pant. then just make sure that you have some small gap all the way around the gear leg.

Rear pant in place

Then the same thing is done with the front pant. Trimming until you can fit it on the rear and have a small gap around the gear leg itself. One thing I did a little different on the right side (the 2nd one I worked on) was to mark out the extended centerline sooner and have the alignment of the pant at least close to where it needs to end up. On the left, I was slightly off and ended up trimming more than I should have. Nothing that the intersection fairing won’t cover up, but still a little too much. The plans don’t really have you aligning things to the centerline until after the trimming is done..

Front joined to rear to start the alignment.

I then dropped a plumb bob on the centerline of the plane and marked it with a string.

Aircraft centerline

I then took a square and measured a random distance over that would provide a good displaced centerline reference closer to the pant/jig itself. I also used a string to mark this on the floor.

Displaced centerline reference

The jig and pant combo was then aligned to the centerline by marking the centerline of the pant in the jig and making sure the measurements from the displaced centerline to the jig centerline matched as perfectly as possible front to back. It’s then that you drill the holes through the pants lining up with the holes in the fairing brackets. This is done by shining a light on the inside so you can see the outline of the hole against the gel-coated fiberglass surface. Once those holes are done and oblonged as needed to align things perfectly.. The area on the inside of the pant, where the screw goes through and mates with the fairing bracket needs to be beefed up with flox. This was done by drilling several small holes around the screw and squirting the epoxy/flox/cabo mixture into them with a syringe.

Closeup of rear screw locations while flox was curing
Closeup of front locations of the screws into the wheel fairing brackets.
Everything all aligned.

You then also beef up the area where the gear extension is with a flox/cabo mixture. After that cures, you take the pants apart and place nut plates for #6 screws where the cleco holes were.

Most of the screws are in place here.

All of the same things were repeated on the right side. Below are some better pics of the trimming reliefs for the gear leg.

Right pant all aligned.
Right pant done too.
Both main wheel pants done!