RV-12 Roll Bar Machine Countersinking

Following the drilling of all the #40 holes in the RV-12’s roll bar assembly to #30, the roll bar assembly was dismantled for deburring. After drilling, care must be taken to make sure the correct orientation of the F-1231B&C straps is maintained. Small loops of wire and name tags were placed in the lower aft most holes and the plans marked accordingly so during assembly later down the road after primer and paint, the parts will fit correctly. The outer holes of the F-1231A roll bar frames were easy deburred, but the standard deburring tool did not have enough clearance for proper deburring of the inside holes. For the inside holes, the angle drill attachment came in handy once again … the deburring bit was removed from the deburring tool and screwed onto the end of the angle drill. The shaft of the angle drill was then turned by hand to rotate the deburring bit a turn or two to remove the burrs. Worked quite well. A word of caution … don’t even consider attaching the angle drill attachment to a drill gun, it will spin the bit way too fast and quickly cut into the rivet hole far too deep.

Breaking down the RV-12’s roll bar assembly for deburring and machine countersinking. Note the tags placed on the bottom aft holes of the F-1231B&C straps to insure correct orientation during reassembly.

Deburring the F-1231B roll bar strap with the hand deburring tool.

                                            Deburring an inside rivet hole on a F-1231A roll bar frame by manually

                                            turning the shaft of an angle drill attachment outfitted with a deburring bit.

 

Holes on the outer flanges of all four F-1231A roll bar frames receive machine countersinking because they will lie under the rear window or canopy. The countersink cage outfitted with a #30-120 degree countersink bit was used to countersink all of the rivet holes on the outer flanges of the four F-1231A roll bar frames to accommodate flush 4-4 pop rivets … with one exception. The rivet holes at the base of each frame that are common to the roll bar mounting are NOT machine countersunk.

 

                                      Machine countersinking the outer flanges on one of the F-2131A roll bar frames

                                      using a countersink cage outfitted with a #30-120 degree countersink bit.

 

One thing I've noticed about the flush 4-4 pop rivets Van’s supplies with the RV-12 kit is the heads are slightly smaller than the Gesipa 4-3 pop rivets being used on the project. I knew this, but forgot to back off the countersink cage a few clicks … so the first hole countersunk ended up being a little deeper then optimum ... oh well, at least I noticed.  Also suggest builders stop the countersinking prematurely in the areas where the curves are on the F-1231A frames and check the countersink depth. Because of the curvature of the frames, the countersink depth can easily end up deeper than those on the flat areas … so adjust your technique accordingly.

RV-12 Roll Bar Final Drilling Completed

I’ll start today's post with a helpful hint for future builders of the RV-12 … at a minimum double the quantity (50) of #40 Clecos Van’s suggests purchasing for the project.  Trying to assemble and final drill the roll bar using only 50 Clecos was just not fun. Can you do it with only 50? Yes, I managed to get the job done, but it took far far longer than necessary. Frankly, trying to work with so few Clecos was a royal PITA.

Because the vast majority of RV-12 parts that are secured with Clecos have #30 holes, the DOG Aviation procurement department ordered far more #30 Clecos than the recommended amount … knowing they would be put to good use during assembly of the wings. Sadly, the same was not done for the seldom used #40 Cleco.

The problem became apparent early on … the roll bar components are to be secured with #40 Clecos then each #40 hole is to be final drilled using a #30 drill bit. Do the math, there is well over 200 holes in the roll bar assembly which require being final drilled … there are six components forming top, bottom, forward and aft layers of holes. Areas where the bends were formed on the W-1231B&C straps required Clecos in every hole to hold the straps in good alignment. The only thing that could be done was work in small sections and constantly move Clecos back and forth all afternoon.

                                           Drilling the first #30 hole,  all fifty #40 Clecos are in use … notice
                                           how many holes on the opposite side are missing Clecos.

                           Roll bar final #30 drilling completed … not much has changed since yesterday’s
                           photo except the color of the Clecos … copper today as opposed to silver yesterday.

What should have been a couple of hours of drilling turned out to be a time sucking abyss of moving Clecos from one section of the roll bar to another over and over and over again … not a productive afternoon. Especially considering I was also hoping to machine countersink approximately 50 holes today that are on the roll bar’s outer aft flanges which will lie under the rear window.

Preparing Section 24 Parts - Roll Bar

Moving forward, began prepping section 24 parts. The RV-12’s roll bar is the first item in section 24 to deal with. The main portion of the roll bar assembly is comprised of six parts. Each forward and aft hoop is made from two F-1231A  halves and connected together at the top and bottom by two straps of metal.

The four F-1231A roll bar halves had some sharp edges so the components will be hand filed.

Filing the sharp edges down on the four F-1231A roll bar forward and aft halves.

Using the small Scotch-Brite wheel to smooth the edges on one of the F-1231A forward roll bar halves.

 

The F-1231B&C straps require being shaped over the edge of a table to form a curve matching the curvature of the roll bar halves. The F-1231B strap forms the outside edge of the roll bar and the F-1231C strap forms the inside edge.

Creating a curve on the F-1231B strap by carefully sliding the strap over the edge of a table to form the curve.

 

                                             F-1231B strap after some forming setting inside one of the forward

                                             roll bar halves. Almost there … just needs a little more tweaking.

 

After the bend is formed on both ends of the F-1231B strap, the same process is used on the F-1231C strap to form the inside curve of the roll bar.

 

The plans instruct the builder to Cleco the roll bar components together so all the #40 holes can be final drilled to #30. Once the holes are drilled to final size, the rivet holes on the flanges of the left and right aft halves of the roll bar that lie directly underneath the rear window, are to be machine countersunk for flush rivets.

Placing one of the aft roll bar halves onto the forward roll bar/F-1231B&C assembly.

Roll bar assembly secured with Clecos and ready for final drilling.

 

Due to a late start, did not have the time to final drill and machine countersink the roll bar assembly today, so that will be the first order of business tomorrow. 

JetFlex – Third Time A Charm … Almost

Today Mother Nature provided a perfect day for spray painting and the DOG Aviation paint department took full advantage of the good weather. Temperatures were in the low 70’s and the winds were between 0 to 5 MPH so the recently primed fuselage parts were successfully sprayed with Sherwin Williams JetFlex interior paint.

For this round of spray painting, the HVLP spray gun was outfitted with the recently purchased 1.8 mm spray gun tip in the hopes the JetFlex paint could be sprayed more evenly than on previous attempts.

Third time a charm … well almost.  Happy to report, the larger tip worked well and it was much easier keeping a wet edge on the paint. The tip does lay down a heavier spray to be sure, but that is OK because I would prefer only painting one coat as opposed to two for weight savings. Think with this spray tip I will be able to get by with only one coat as long as care is taken to make sure the spray pattern is well overlapped.

I did discover one problem using the larger tip. Because JetFlex forms a film quickly when it hits air, the larger tip created more paint buildup on the tip of the spray gun which would form a film that would blow off resulting in occasional small splats of paint getting on the work. Certainly disgruntling to say the least. The smaller spray tip would do the same thing but not nearly as often.

Various methods were tried to keep the occasional splats from occurring … wiping the tip with a finger did not solve the issue but made it slightly better, keeping the air on and modulating the liquid flow also extended the time, but splats still occurred. The only thing that seemed to be effective for the longest amount of time was scrubbing the spray gun tip with a toothbrush dunked in the water and ammonia cleaning solution.

Admittedly, painting is not my forte, so it is possible the gun is not quite set up correctly for the larger tip. Will try to do a little research on the issue and see if there is a setup solution. However, that said, thin JetFlex forms a skin almost instantly … so I think it is more of an issue with the paint.

The RV-12’s fuselage skins top coated with Sherwin Williams JetFlex Sandy Beige semi-gloss interior paint.

Painted quite a few parts today … practically everything hanging from the manila name tags in the background was painted today, along with the parts covering both benches and the three panels in the shipping crate.

Thus far, all the parts have been painted from one quart of Jet-Flex which is now empty except for an ounce or two.  A second quart was purchased and that should be way more than enough to finish the remaining parts and those included with the finishing kit which is now on order.

Large Print Giveth … Small Print Taketh Away

Due to cold overnight temps and less than optimum daytime temperatures, decided to hold off until tomorrow to spray the Jet-Flex interior paint on the recently primed fuselage parts visible from inside the cockpit.

In the mean time, wanted to install a new high output, four light fluorescent light fixture DOG Aviation’s procurement department recently secured. The new light fixture has a very highly polished reflector and utilizes the new T5 high output, 4,100K fluorescent tubes. Outfitted with 4 high output fluorescent tubes, this fixture cranks out a whopping 20,000 lumens ... perfect for the hangar.

Mike was able to contact a friend who works at one of the FBO’s on the field and we were able to borrow a 16 foot step ladder to install the new overhead light fixture. The light will be centered over the T hanger’s recess for the tail section. The euphoric feeling of being jazzed about Mike being able to procure a tall ladder to allow access to the hanger’s roof beams quickly faded away when the light fixture’s box was opened. We quickly realized the two loops at either end of the light fixture used to hang the light fixture were not in the box … even though they were shown on the light fixture pictured on the outside of the box. We had some light duty chain for hanging the light, but now had no way of connecting the chain to the light fixture. Turning the box over reveled the small print stating the hangers are an optional purchase. The large print giveth … and the small print taketh away. That forced us to make yet another trip to Home Depot and Aircraft Supply to purchase four S hooks to attach to eyelets on the light fixture and the aforementioned chain.

Mike positioning the borrowed 16 foot step ladder.

 

Fortunately, Mike had some beam clamps and bridle rings, so we hung the light fixture from beam clamps that had bridle rings attached. The beam clamps and bridle rings were also used to secure the wire between the light and the hangar’s wall where the switched outlet was installed … way overkill, but the bridle rings made running the light’s power cord a piece of cake.

Up on the ladder about to install another beam clamp and bridle ring to secure the light’s power cord.

Using a nut driver to secure a beam clamp onto the overhead beam. 

 

The electrical outlets are still not totally completed because the light switch for the new overhead fixture still needs to be installed in the electrical box. However, due to other commitments, we were not able to finish the job today. There is really only about 15 minutes of work left to do and all the electrical upgrades will be finished. At some point in the future, will likely add two more lights and perhaps an outlet on the hangar’s forward right wall.

Bad Weather Spurs Hangar 45 Upgrades

Because the recent rain and cold has not been conducive for spraying Jet-Flex interior paint on the now primed RV-12’s interior components ... decided to head over to the airport and make some infrastructure improvements to DOG Aviation’s future home at hangar 45. The hangar only has two outlets ... which, given the hangar's size, is rather anemic so measurements were taken and the DOG Aviation procurement department quickly amassed conduit, plus fittings and the makings for a few new outlets. Mike lent a helping hand and the conduit, electrical boxes and wiring was installed in no time. A total of three additional outlets were installed. An additional overhead light is also being installed but at the time, we did not have a ladder tall enough to reach the overhead beams nor did we have the beam clamps necessary to hang the overhead conduit. Forgot to take the camera, so don’t have any photos to share at this time.

After the primer session last Thursday, there were a couple ounces of Akzo primer left over ... so since it seems to easily keep for a few days if frozen, decided to place the unused  portion into the freezer to extend its useful life for use in the airbrush (hopefully tomorrow)on the following two small jobs.

The F-1256-L&R fuselage stiffeners were separated on the band saw, deburred and all but the very bottom hole on both stiffeners were dimpled for the 120 degree flush rivets being used on the RV-12 project. (The very bottom hole on each of the F-1256 stiffeners resides in the no dimple zone declared in previous posts). Figured since the stiffeners don’t have much surface area, they can be airbrushed with the left over primer.

Also, each of the F-1270 fuselage skins have an area that will be overlapped by the F-1277-L&R turtle deck skins. So the F-1277 turtle deck skin was temporally secured onto the fuselage skins with Clecos and the blue protective film was melted from the overlapping area with a soldering iron. The leftover Akzo will also be airbrushed onto the overlap area on the fuselage skins as well.

More Fuselage Components Primed

Prior to priming yesterday, the last few time consuming components worked on this week were the cockpit vent doors. The F-1286 and F-1287 vent brackets and slides required being separated on the band saw and deburred. These parts have lots of nooks and crannies that needed to be deburred and smoothed ... so for a simple assembly, the vent components took up a respectable amount of time to prepare.

The left and right vent doors are comprised of four pieces … the F-1093 vent door, F-1092 vent door doubler and F- 1087-A&B vent slides … all of which needed to be match drilled to one another using a #40 drill. After match drilling, all the holes both F-1093 vent doors require machine countersinking on the outboard side using a #40-100 degree bit.

All the components that make up the RV-12’s fresh air vents.

 

A helpful builder tip: Because the F-1093 vent door metal is thin, the countersinking bit will be creating a “knife edge” so the countersink bit will tend to wander when the countersink gets close to the proper depth. This is because there is virtually no “hole” metal left to keep the countersink bit’s tip centered and therefore it will begin drifting. This causes the rivet hole to be larger than it should be. To solve this, Cleco the vent door doubler onto the door, use Boelube in the rivet hole and spin the cutting bit as slow as possible. The extra thickness of metal provided by the vent door doubler will keep the tip of the countersink bit in place with a minimum amount of rounding out of the rivet holes.

After the vent door components were drilled and countersunk, the F-1096 vent doubler and F-1086-A&B vent brackets were secured onto the F-1270 fuselage skins for match drilling to #30. After match drilling, the holes in the F-1270 fuselage skin surrounding the vent were dimpled for flush rivets being used on the RV-12 using a #30-120 degree dimple die. Also, the rivet holes in the vent doubler and brackets were dimpled as well.

Match drilling the F-1270 fuselage skin into the F-1096 vent doubler and F-1086-A&B brackets.

 

After dimpling the vent area on the F-1270 fuselage skins, I noticed the plans have the builder place dimples for nutplate rivets in the area where the electrical connector to the wing will be installed. The plans mention squeezer yoke access is bad for a couple of rivet holes that require dimpling and to manually pound the dies together. After reading that, decided it prudent to place those #40 dimples into the F-1270 skins using the C-frame while the skin was on the bench and access was not an issue.

 

Using the C-frame outfitted with #40-100 degree dimple dies to dimple the nutplate rivet holes in the area where the electrical connector for the wing will be installed. Far easier to do now than when the skin is on the airplane, plus the dimples will all be primed.

 

A pair of floor pans were almost overlooked so they were quickly deburred, edges smoothed and the outer flanges touching the F-1270 skins were dimpled for the flush rivets being used on the project.

 

                                        Dimpling the rivet holes on the outer flange of a floor pan for flush rivets

                                        using the pneumatic squeezer outfitted with #30-120 degree dimple dies.

 

As one can see in the above photo, there is a plethora of parts on the bench ready for priming including both F-1270 fuselage skins not in the photo. All of those parts were cleaned with Acetone, scuffed up with maroon Scotch-Brite pads and re-cleaned with Acetone. Yesterday, all the parts were primed with Akzo primer. The majority of those parts will be receiving a Jet-Flex top coating as well.

Fuselage Skins Dimpled For Flush Rivets

The only items worked on during this shop session were the F-1270 left and right fuselage skins. The spar cutout was completed on the F-1270-L fuselage skin using the same procedure that was used to make the cutout on the F-1270-R skin yesterday …. a nibbling tool to remove the metal and a file to smooth out the edges.

Now that the spar cutouts have been completed for both fuselage skins, each skin received a deburring along the edges with files, followed by a final smoothing with the Scotch-Brite wheel and a 3M sanding sponge.

Smoothing the edge of the F-1270-L fuselage skin with a Scotch-Brite wheel.

 

After both F-1270 fuselage skins were deburred and smoothed, they were dimpled using the #30-120 degree dimple dies in Pete’s C-frame. Three areas were purposely not dimpled at this time:
 

1. The previously mentioned NDZ (no dimple zone) where the F-1270A stiffener will be located. This area will not receive any dimples because it will be hidden by the wings.

2. The top row of holes in the F-1270 skins. These holes will be used to match drill into the longerons when the longerons are finally completed. A much more accurate match drilling will be accomplished if the holes are not dimpled when match drilling the longerons. After the longeron match drilling is completed, the top row of holes in the F-1270 skins will be dimpled, the longeron holes machine countersunk and primer sprayed with an airbrush as necessary to prime the longerons and touch up the top row of holes in the F-1270 skins.

3. The rivet holes surrounding the air vent are undersized and are to be match drilled into the vent assembly … that assembly may not be ready before priming, but hoping to complete the air vent parts tomorrow so the match drilling and dimpling can be accomplished before Tuesday … which is the target day for spraying primer.

 

                                     Dimpling the F-1270-L fuselage skin with Pete’s C-frame outfitted with

                                     #30-120 degree dimple dies for the flush rivets being used on the RV-12 project.

              Dimpled F-1270. Looking closely one can see the top row of rivet holes were not dimpled for flush

              rivets at this time, nor were the holes around the rectangular air vent port on the far right.