14-06 & 07: Riveting Ribs to Main Spars

Flap Brackets

Ribs #3 and #8 on each wing have a very hefty bracket for the flaps to hinge from. The plans asked to press fit in a bronze bushing for the flap hinge bolt to run in. This was an easy task using a C Clamp and an appropriately sized socket.  

These were then riveted to their respective ribs using the pneumatic squeezer and the longeron yoke. The doubler bracket and the rib were the same thickness, so i elected to put the shop head on the rib side. 

Aileron Torque Tube Brackets

Next up was the aileron torque tube bracket. This was put together with the squeezer. The plans ask for this to be riveted to the #1 rib before the rib is installed on the spar. If i did this, it would mean there was no room for the gun on the rib side of the spar, and these rivets would need to have the shop heads on the rib side of the spar (the thinner material). Given that these would need 70psi, i didn't think this was a good idea. So i did not rivet these brackets to the rib, but installed them once the rib was riveted to the spar. 

On the left bracket, i inadvertently installed the rivets for the bearing the wrong way around. No reason to drill them out. 

Installing the ribs on the Spar

Next up was to actually install the ribs on the spar. All the ribs were clecod to the spar except #1 and #2 - these are left off so you can get access to #3 for riveting. Once #3 is done, you do #2, then #1 in order. Where the 'step bar' is very thick on the top and bottom of the spar web, a bolt is used to fasten the ribs to the spars and the plans call for these to be installed first. Most of the bolts are installed with the heads of the bolts on the rib side, however at the root end, the top 4 and bottom 2 bolts are installed with the heads on the step bar side, and the nuts on the rib side. 

The plans state "DO NOT INSTALL NUTS AND WASHERS ON THE 3 MOST INBOARD WING RIBS AT THIS TIME" and "it will be necessary to push the bolts out of the way to set the rivets". These statements are a little confusing; do they mean the 3 most inboard ones that are currently clecod to the spar? OR ribs #1-#3? In any case, i got what they were talking about once it was all put together. Basically on every bolt that has the nut on the rib side, the bolt would get in the way of the rivet which joins the forward most tab of the rib to the wing spar flange (not the rivets which join the rib to the spar web). So i just left the nuts off these bolts but put the bolts in the holes to ensure alignment. 

Each bolt was installed with some TefGel on the shank to prevent corrosion, and each nut was torqued to 38 in/lbs and marked with some paint. The cardboard bolt keeper was used to make sure the correct bolt went in the correct hole, and was crosschecked with the plans and a bolt gauge. However, despite this, i still found a few of the bolts had a tiny but of shoulder showing through the hole - in these ones i used 2 x thick washers. 

When setting the rivets, I tried to used the offset cupped set on the rivets but that thing is a nightmare! It would rotate while the gun was firing and half way through the first wing and i had to drill out 3 rivets due to smilies on the rivet heads. Not an easy task on -7 rivet lengths.

Better to be lucky than good

In the end i found that the short straight cupped set was the best one to use - the rib was able to be pushed out of the way and so long as i kept pressure on the gun, the rib flange stayed pushed down tightly against the spar web. I ground own one side of the set as much as i could, then wrapped it in tape (and put tape on the gun as well). 

Shop heads on one of the ribs

Shop heads on the front of the spar web.

Manufactured heads on the rib.

The aileron torque tube brackets were installed on the #1 ribs on each wing. I tried using the squeezer but was not able to each many of the rivets. So in the end used the offset cupped set and the small tungsten bucking bar.

I could only reach one or two rivets like this (the pneumatic squeezer didn't fit at all).

14-02: Wing Rib Preparation

Once all the ribs were primed, each rib was fluted then the flanges were straightened.

Fluting

I find the best way to flute is to place the rib down on a flat board on the table (i ended up putting some paper down to protect the rib) and press down in the centre of the rib. You will see where the rib is bowed from the forming process. 

These are all the tools needed for the task

You can see the bow in the rib from the forming process

I start fluting in the area where the most bow is located; the depth of the flutes is proportional to the bow off the table. Eventually the rib lowers and begins to touch the table and you can see the very ends of the rib starts to lift off the table. The whole time i am holding the rib down in the centre with my free hand. Once the ends start to lift, i stop fluting and check the straightness using a long ruler along the rivet holes. This method seems to work perfectly, and removes the frustrating process where you over flute, then flatten it out, but go too far, so flute again etc.

Straightening Flanges

To make sure all the flanges are at 90 degrees, i use the wooden tool that is screwed to the bench in the photos above. This tool allows me to push the flange at every rivet hole 11 degrees past 90, which after spring back, leaves the flanges perfect. I check using a small square in a few locations (especially at the ends, or on small tabs) to make sure they are indeed 90 degrees. 

Here is a link to how the tool is built, and here is a link to how i used it on the HS ribs

Dimpling

Page 14-02 Step 3 asks me to dimple all the BOTTOM flanges of each wing rib (except the tabs under the spar flanges). 

Further on, in the Top Wing Skins section page 16-02, Step 7, it asks you to dimple all the TOP flanges of all the wing ribs, but not the ones under the wing walk doubler. 

As it turns out, these holes will remain undimpled because the wing skin holes will be countersunk at all locations which are common to the wing walk doublers. 

Knowing this, i saw no reason why i couldn't dimple all the TOP flanges at this stage (surely it is easier with them on the bench, not riveted to the spar?), however i would NOT dimple those holes on ribs 1-4 (common with the wing walk doublers). 

EXCEPT! On one rib (the inboard most wing rib on the left side) i had a massive brain fart, and dimpled the TOP flanges of this rib... DOH! 

A solution?

From reading on the forums, it seems that on other Van's designs the wing walk doublers and skins are dimpled, so i decided to do a little test. At the inboard skin / wing walk doubler locations the 'stack up' of materials would be as follows:

The skin stack up at the 4 inboard ribs is:

0.032" Inboard Wing Skin

0.025" Wing Walk Doublers

0.032" Wing Rib (or 0.025" wing rib for ribs 2-4).

So i thought i would do a little test with some scrap as above, and compare what a countersunk versus a dimpled connection would look like:

This left me with 2 options:

• Undimple all the holes on the TOP flange of the one rib where i made the mistake, or
• Dimple all the other ribs and just go with a dimpled connection for all locations!

Before making the decision, i decided to ask the mothership and got the following reply:

Must consider the nutplates

Having been given the go ahead from the mothership to dimple instead of countersink, it got me thinking about the nutplates for the wing root fairing. This part is fitted much much later in the build, however the nutplates are fitted in the top and bottom wing skin chapters. 

If you follow the plans:

• The lower flanges of the ribs are just the inboard wing skin and the rib flange (no doubler) and both these are dimpled. The #19 screw holes are dimpled at the skin and the rib, and a dimpled nutplate (K1100) is used. 
• The upper flanges of the ribs are skin / doubler / rib so are a bit thick to dimple for a #8 screw - these are therefore dimpled at the nutplate attach rivets, but not at the screw locations (a K1000 nutplate is used). Once everything is riveted in place, the #19 holes are countersunk through the wing skin and doublers to accept the dimple of a #8 screw in the wing root fairing. 

So what would happen if i dimpled the TOP flange of the inboard wing rib? 

The answer is basically as follows:

• There is no issue from Van's for the dimpling of the parts, however i can't dimple for a #8 screw dimple (the part stack is too thick where there is skin / doubler / rib), so
• All rivet locations are fine to be dimpled, but the holes where the root fairing screws go, will need to be flattened. 
• Eventually, i will match drill the nutplate rivet holes from the wing skins to the ribs. These holes in the ribs will all then be dimpled. 
• The flattened holes will be updrilled to #19, and countersunk for for a #8 screw dimple in the root fairing - if any of these crack slightly when i flatten them, there should be no issue as i am updrilling and countersinking these holes. 
• For these holes, a normal K1000 nutplate will be used, but i will need to dimple the attach holes in this nutplate to go over the dimples.

I think this plan is a sound one and will hopefully mitigate the risk of a cracked dimple, if i were to try to flatten a whole wing rib worth of dimples. 

As a side note for anyone following me with regard to the bottom flanges on the inboard wing ribs - Van's asks you to dimple these on page 14-02. However, there are a number of these holes which end up being screw holes - and will eventually be updrilled and dimpled for a #8 screw dimple in the wing root fairing. It's interesting they didn't ask you to skip these holes - now i have some that are dimpled for a #40 dimple, but will need to be updrilled and dimpled larger later. No biggie i guess. 

The Priming Process explained (Priming Wing Ribs)

I split the wing ribs into 4 batches of 7 - which allowed me to keep the smaller items (the aileron torque tube brackets & flap brackets etc) apart from each other so they didn't get mixed up - this saved having to label them with tokens. The wing ribs themselves were labelled with the wing rib number (i.e. L12, or R3) on a stamped token so the number would hold up through the priming process.

Here a rib label has been transferred from the token back to the part flange, before dimpling and fluting etc.

The Preparation Process

Prior to priming, the parts are cleaned with EkoClean, which is mixed 10:1 with normal tap water in a spray bottle and sprayed on. This gets off any oils from my hands etc, and also takes off most of the red ink that is left on the parts. I do not rinse this off, but go straight into using EkoEtch, which is mixed 2:1 with normal tap water, also in a spray bottle. This is sprayed on and i find i need a dust mask if doing this inside, as the smell gets you in the throat. The whole part then receives a scrubbing using 3M Scothbrite 8447 pads, which are a bit coarser than the normal 7447 pads and make the job go a bit quicker. I cut the pads into little squares and wet them down with the etch. I am looking for a uniform level of dullness on the part. Once this is done, i used a normal hose and rinse off all the cleaning and etch. If you have done it right, the water will lay on the surface in a uniform sheen, and not ball up into water droplets.

I wear gloves throughout this whole process to avoid oils from my skin getting on the parts. The parts are then left to dry naturally - i do not use compressed air to dry them, as this can spray minute oil droplets on the parts, however i do sometimes steal the bosses hairdryer!

These parts are drying - you can see the "uniform dullness" i look for. 

The Priming Process

I had made a previous post which can be seen here, where i had some issues at the start with the Stewart Systems paint seeming too thick to spray. I was thinning it quite a bit at the start, however now i have the process down pat i felt the need to clarify my comments on the paint.

As a reminder, the primer being used here is Stewart Systems EkoPoxy, in Smoke Grey color.

Firstly, this paint is not like other paints which i have used. It seems to be a very high solids paint, which settles fairly quickly over time. If you try and mix it together with a stick (as i did originally) you have almost zero chance of getting it thin enough to spray (or even get out of the can). To combat this, on the advice of Stewart Systems, i found a couple of things that worked:

• The paint doesn't like being cold: I was keeping the paint can in my shed, and it was just too cold in winter for get it mixed together properly. Once i started keeping it in the house i found it a lot easier to mix and use. 
• The paint needs to be mechanically agitated: A stirring stick is not going to cut it - on the advice of Stewart's, i purchased one of the mixers shown below and it works a treat. About 30-60 seconds of mixing (ensuring i get the stuff off the bottom) is like magic - not only does the paint mix together into a uniform consistency, but it thins but a significant amount, perhaps like cream. 
• It can't be mixed easily in the can: I found it almost impossible to mix the paint in the can using the mechanical mixer shown below as the paint just flies out everywhere - so when i get an order of paint (say 2 quarts), i decant it into a container shown below. This allows it to be mixed much more easily. 

I use a pail like this to decant the primer into

This is the type of mixer that is used to mix the paint before thinning etc. 

Once the paint is mixed up to a uniform consistency, I used a 60ml horse syringe to take out the required amount into a paint mixing up on scales. I then thin it with 13% of denatured water and 18% of the Part B hardener by weight. This is mixed up with a stick and poured through a paint strainer into the HVLP gun. After thinning, it turns to the consistency of milk. 

I set the gun as per the instructions that came with it - about 35PSI at the regulator (maybe 25-30 PSI at the tip). The paint sprays very easily and goes on in one coat, and very very rarely runs (unless i put it on too thick). I can spray one side of the parts and after around 5-10 minutes, the parts can be flipped and the other side sprayed. 

Wing Ribs before and after priming

Check out those guns!

So far i am very very happy with the paint - easy to spray by an absolute novice, dries fast and stands up to dimpling after the priming very well. The best part is that it is non-toxic, has almost no over-spray (what is there just falls as dust) and can be cleaned up in normal tap water. 

14-04: Wing Systems Holes / Wing Electrical Planning

Wings: Electrical Decision Making

Of course the plan with my build is to leave the avionics decisions (and actual purchases) until as late as i can in the process - for the obvious reasons. However, as with the empennage, it is a lot easier to run wires for items before the area is closed up. In the case of the wings, this means drilling the 'systems holes' for the plastic grommets in each rib. I had initially thought i would just drill every hole to the maximum size (1/2") however since i had begun to draw up the electrical items for the empennage, i thought i would continue with the wire book and KiCAD drawings of the system and begin to populate the wings (virtually anyway).

In making up the wiring diagrams, i principally relied on the Garmin G3X install manual, while referencing both the Van's master wiring diagrams and also the Dynon Skyview manual, just to make sure i was not boxing myself into a corner with my decision making. Each wire was drawn in KiCAD, then added to the wire book. The main reason for the wire book is so i can add the wire lengths gleaned from the Van's wiring diagrams, in order to order the required quantity of wire. These lengths will be cross checked against the wool i will use below. 

Wire Book entries for the Left and Right wings

Equipment Locations

Time for some rough decision making (cue the forums!) - In the RV-14 this was fairly simple as there were some locations which were not disputable - for instance: 

• Roll Trim must go in the right wing (at the innermost inspection panel)
• Roll Servo (Autopilot) must go in the right wing at the aileron bellcrank
• There is a nice ADAHRS bracket in the left wing, so this is the obvious choice for the magnetometer.
• Landing Lights (in leading edge cutouts)
• Nav / Strobe Lights (in wingtips)
• Fuel Sender wires (both wings)

The other items to be considered were:

• Heated Pitot Tube
• Pitot and AoA air lines
• OAT (Temperature Probe)
• COAX for a Wingtip Nav antenna (in the left wing)

Pitot Tube

The first decision related to the Pitot Tube was Left wing or Right wing. The Van's stock location for the Pitot is in the LEFT wing, one bay inboard of the left aileron bellcrank. This is fine for the Van's aluminium tube pitot, however I will be going for a heated pitot tube (brand TBA). Given the magnetometer will be in the left wing, i decided to place the pitot in the right wing. 

This left 2 possible locations - one would be in the stock location (one bay inboard of the aileron bellcrank, accessed with an inspection panel on each side of the pitot), and the other is one bay outboard of the aileron bellcrank (accessed through the bellcrank access panel only). 

Each place has it's own issues, with people on the forums with mixed opinions on the best path. Primarily it is a choice between the inboard location, with the possibility of the pitot tubes interfering with the aileron pushrod, and the outboard location where a tiedown rope could potentially interfere with the pitot tube. Who knows which opinion is correct - so at this early stage i will keep my options open, and plan for the pitot to be in either of the 2 locations. 

OAT Temp Probe

Since there is a lot of items in the right wing already, the easy location for this is in the left wing. I will not be installing the stall warning vane in my aircraft (since i will have an AoA), so the inspection panel on the left hand outboard leading edge will be a good location i think (and the wires will fit through the existing hole in the spar). 

EDIT: After looking on a number of forums, especially this recent discussion I found out there is actually already a hole punched in the left hand wing for an OAT probe - designed around the Dynon AHRS system, the OAT probe is adjacent to the first under wing inspection panel, where the ADAHRS mount is located - so this is the obvious choice for the OAT probe location. 

This is the left wing looking at the bottom - you can see the referenced hole adjacent to the inspection panel (circled in red).

In summary, items will be located (probably!) as follows:

Left Wing:

• Landing Lights
• Nav/Strobe Lights
• OAT probe
• Magnetometer
• Fuel Sender, &
• Wingtip Archer Nav Antenna

Right Wing:

• Landing Lights
• Nav/Strobe Lights
• Autopilot Roll Servo
• Aileron Trim Servo
• Heated Pitot Tube
• Pitot / AoA Air Lines
• Fuel Sender

Connector Planning

For planning of the connectors in the wing root, the design goals were that i wanted to keep the wires from one component on the same connector if possible, rather than splitting a bundle between 2 connectors and also needed to observe the current limitations on the pins for each style of connector. This basically ruled out DSub connectors and i've never really been a fan of the molex connectors (especially the miniature ones). Deutsch connectors were another good option, with the DTM series (size 20 contacts) being good for signal, and the DT series (size 16 contacts) good for power (up to 13 amps). However, these come in a maximum of 12 contacts per connector, so would necessitate 3 connectors were wing. 

Having considered all the of the above, I really like the CPC style connectors for the wing roots - these can be setup as a flange mounted on the fuselage side (meaning female sockets on the 'live side') and a male pinned plug connector on the wing side (aka 'reverse sex' connectors). The CPC connectors come in 2 series:

• Series 1 uses molex style pins, and these are available in both small gauge (20-24AWG) and large gauge (14-18AWG), both up to 13 amps - meaning these will be perfect for higher power devices / large gauge wires. Series 1 connectors come in 4,9,16,24 & 37 contacts normal sex, and 4,14 & 37 reverse sex). A 14 contact Series 1 should be sufficient for the higher power devices.
• Series 2 uses standard DSub pins (which i have plenty of) and are therefore suitable for 20-24AWG wires and circa 5 amps. Series 2 come in 8,9,28 & 63 contacts normal sex, and 8, 28 & 57 reverse sex). A 28 contact Series 2 should be well sufficient for the lower power devices (i could potentially use a smaller connector in the left wing). 

When deciding what wires should be bundled together, the basic decision making process was that:

1. Higher Power items should be grouped together
2. Data Wires should be kept away from higher power wires due to noise.

In keeping with this idea, the following wire groups seemed to make sense:

Right Wing

- Autopilot Roll Servo, Trim Motor and Fuel Sender wires

- Landing Lights, Nav/Strobe Lights & Pitot Heat Wires

- In addition, there will be Pitot and AoA 'air lines' needed to come back to the panel

Left Wing

- Magnetometer and Fuel Sender Wires

- Landing Lights, Nav/Strobe Lights & Temperature (OAT) probe.

- In addition, there will be a RG400 Coax for a wingtip Archer Nav Antenna to come back to the panel.

EDIT: A note on the OAT probe - it seems that this is designed to be run without breaking the cable - i.e. run the probe all the way to the panel with no connector. Since i will be likely to have all the avionics installed and wiring done at home before the wings are put on, i think i will not include any wiring for the OAT probe at this time - leaving it until later. I will however plan for the probe to go through a connector just in case. This way i can simply install the probe in the wing before the wings are attached, and at that time make a decision on whether i wanted to run the probe wire through the connector or not - there will be room in a connector if required.

Below are 2 screenshots showing the current configuration for with wing connectors - the upper is the Series 2 (DSub pin) 28 position connector, and the lower is the Series 1 (13 Amp pin) 14 Position connector, which carries all the larger current items. 

Right Wing Connectors - from top to bottom groupings:

Series 2 Connector (top) - 13 free positions:

1. Roll Servo Can-Bus Wiring (2 Core, 22 AWG Shielded)
2. Roll Servo Power & Ground (both 20 AWG) and 'Control Wheel Steering' (22 AWG)
3. Roll Servo RS232 Data wiring (2 core, 22 AWG shielded)
4. Trim Motor Wires (5 Core, 24 Jacketed)
5. Fuel Sender (22 AWG)

Series 1 Connector (bottom) - 5 free positions:

1. Landing Light Power & Ground (14 AWG twisted)
2. Wingtip Nav / Strobe Lights (3 core, 20 AWG Shielded)
3. Pitot Power and Ground (14 AWG twisted)
4. Pitot State wire (22 AWG)

Right Wing connectors. 

Left Wing Connectors - from top to bottom groupings:

Series 2 Connector (top) - 21 free positions:

1. Magnetometer Can-Bus Wiring (2 Core, 22 AWG Shielded)
2. Magnetometer Primary, Secondary power & Ground (3 x 20 AWG)
3. Fuel Sender (22 AWG)

Series 1 Connector (bottom) - 4 free positions:

1. Landing Light Power & Ground (14 AWG twisted)
2. Wingtip Nav / Strobe Lights (3 core, 20 AWG Shielded)
3. Temperature Probe (3 core 22 AWG Shielded) EDIT: Perhaps! See note above

Left Wing Connectors

Routing of Wire Groups

Having worked out the wiring bundles, the design goal for the routing of these bundles was:

1. Keep them as straight as possible to help with maintenance later on. 
2. Keep 'noisy' wires away as far as possible from data wires.
3. Don't fill up the grommets too much to allow for future expansion. 

Once all this was decided, i took to the shed with a bunch of coloured wool (don't tell the minister for war and finance) and worked out the wire runs. While a little hard to describe online i will give it a go! 

Basically, there are 3 choices for holes in each rib - of course i can drill holes wherever i want, but i wanted to keep as close to Van's 'approved' locations as possible. 

Having looked at the physical wing, i think the following is a good plan for wire routing:

Right Wing

- Autopilot Roll Servo, Trim Motor and Fuel Sender wires - Lower Forward holes out as far as the bay prior to the aileron bell crank rib, then up through an additional hole in the top of rib #9, then over the top of the top aileron bellcrank bracket straight to the roll servo. The trim wires would branch off this route after rib #4 to the trim motor (and if going Garmin, then the trim motor to roll servo interconnect wires could go back along the same route as above to the roll servo). 

- Landing Lights, Nav/Strobe Lights & Pitot Heat Wires - Lower Aft holes, all the way from the root to the tip. The landing lights branch off through the grommet in the spar web to the landing lights. 

-  Pitot and AoA 'air lines' - Since there are no Upper Aft systems holes drilled, this will allow for 2 small holes to be drilled to carry the pitot line and the AoA line separately. 

Right Wing Root - the orange wool is the Roll Servo / Trim wire in the lower forward holes. The blue wool is the Landing / Strobe lights, and the green wool is the Pitot heat wires. The wool the the upper forward holes (brown) represents the 2 Pitot and AoA 'Air lines'.

Here the orange wool represents the Roll Servo and Trim wires, branching up through a hole in the #9 rib, over the top of the aileron bellcrank bracket to the roll servo.

Also here you can see the green wool representing the pitot wires - there are 2 options - the bay left of the bellcrank, where the green tape is (alleviating the interference issue with the tie down rope) - this is the stock location, or the bay on the right of the image where the green wool is (alleviating the issue with the pitot lines interfering with the aileron pushrod). The left most position would mean 2 access panels (one on each side) to gain access to the probe which in the end may override any issues with pitot tube interference with the aileron pushrod. I.e. a one time problem to route the pitot lines, versus harder maintenance in the future / tie down issues with the aeroplane.

The blue wool represents the landing / Nav / strobe wires. The Landing lights branch off after rib #13 through the spar to the landing lights. On the right of the image is the left spar, where the bundle runs in the Lower Forward holes, and one the left of the image is the right wing, where the bundle runs in the Lower Aft holes.

Left Wing

- Magnetometer and Fuel Sender Wires - Lower Aft holes from the root until after rib #4 where the the Magnetometer will be located. This way they do not cross, nor go near the landing / Nav strobe wiring. 

- Landing Lights, Nav/Strobe Lights & Temperature (OAT) probe - Lower Forward Systems Holes all the way from the root to the tip. The landing lights branch off through the grommet in the spar web to the landing lights. 
EDIT: The OAT probe will now be located in the same bay as the magnetometer (between ribs #4 and #5). Therefore the best location for this wire will still be through the lower forward holes, however instead of branching off at the bay prior to the aileron bellcrank, this wire will branch off at the magnetometer bay. I should be able to use an ADEL clamp on one of the fuel tank Z attach bracket bolts to hold this wire when it branches off.

-  RG400 Coax for a wingtip Archer Nav Antenna - There are no upper aft systems holes, so I can drill a 3/8" hole for a grommet to carry some RG400 coax all the way from the root to the tip - i will crimp a connector on this after the wire has been run to keep the holes as small as possible. 

The orange wool represents the magnetometer wiring running in the Lower Aft systems holes. This keeps it well away from the Landing / Nav / Strobe wiring.

The Landing / Nav / Strobe lights in the left wing run in the lower forward holes - meaning they run right past the aileron bellcrank. This is not possible in the right wing, as they would have interfered with the roll servo actuator arm. In the left wing this is not an issue. I will likely add an ADEL clamp on one of the bellcrank bolts to hold the wire bundle.

Here the blue wool represents the Landing / Nav / Strobe wires and the green is the OAT probe wires - which branch out of the bundle through the hole meant for the Stall Warning Vane and into the leading edge. The inspection panel in that location seems like a good spot for the OAT probe. EDIT: The OAT probe will now branch off at the Magnetometer bay as described above.

Grommet Sizing

The plans give callouts for the various grommet sizes but these largely don't make sense and are also designed for the Van's wire routing. Since i was doing something different, i needed to decide what size grommets i needed for each of the bundles above. I decided to measure each wire, then draw it in Word, placing the little circles inside a larger circle representing the grommet internal diameter. I then tested these using groups of wire off-cuts i had on hand to make sure they were right. You can see the grommets i have chosen in the images below, with a green square around them. In all other locations where I will not be running a wire at this point, i will drill to 3/8" for a SB-375-4 grommet. While this seems like the smallest grommet size, it in fact has almost the same ID as the SB-437-4 grommet, but has a smaller hole in the rib (so i think that is a good idea).

In the above the trim wires run as a 5 core 24 AWG out to the trim motor, then 2 pairs of 22 AWG twisted wires run to the roll servo (this is the Garmin setup). If not using Garmin, then the trim wires would just terminate at the trim motor location (but at this stage, at least the grommets are big enough for both options). 

While the SB500-6 grommet for ribs 1-10 (top green box above) seems a tight fit in the above image, on testing the 2 x twisted pairs of 14AWG wires (the brown circles) fit fine in the actual grommet with the other stated wires. 

Doing some actual work

Now that all this planning has been done, each hole has been marked up on the rib as per the above plan, then once the ribs are removed from the wing, i will up-drill all of the holes as per this plan!