F-1202N-L&R Forward Skin Stiffeners Remade

Those readers following the DOG Aviation RV-12 know that it is being built utilizing flush blind rivets as opposed to low profile dome blind rivets. There have not really been any issues with dimpling the parts especially when the need for a smaller diameter 120 degree male dies was discovered very early on in the project. All of the parts have been successfully dimpled thus far with great results with the exception of the F-1202N-L&R forward skin stiffeners. Many months ago both F-1202N stiffeners were dimpled for flush rivets … they took on quite a bow which I was able to eliminate by fluting. The reason for this was the factory drilled holes in the stiffeners were close to the web to flange transition … this caused the small male dimple die to ride into the transition region of bend. The process of dimpling caused the angle to open a bit and also created a bow in the two stiffeners.

This is an interior part and the fluting will show. This has bothered me somewhat, so when making the angles for the baggage bulkhead modification, decided to fabricate a couple of additional angles so new F-1202N forward skin stiffeners can be fabricated.

The fluting necessary to straighten the F-1202N stiffeners can easily be seen on the left of this photo … the new yet to be drilled replacement angles are on the right.

The newly fabricated angles in the above photo have a 1/2" flange and the rivet holes will be centered at 1/4" in from the outer edge. This will allow just enough room so the male dimple die will clear the transition area and not bow the metal as the dimples are created. New F-1202N pieces were purchased to use as a template for the hole spacing when drilling the new angles.

Match drilling the replacement stiffener using a new F-1202N as a template.

Ran out of time so did not get the new stiffeners dimples but I do not expect any issues. If there are any dimpling issues, it will be duly noted here for those builders utilizing flush rivets in their RV-12.

Baggage Bulkhead Modification Completed

Today the finishing touches were put on the vertical and horizontal angle pieces for the baggage bulkhead modification. The #19 holes drilled into the F-1207F bulkhead adjacent to the horizontal and vertical cuts were dimpled for #8 Screws and the mounting holes in the horizontal angle for the K1100-8 nutplates were also dimpled … along with all the nutplates.

The last part of the baggage bulkhead modification consists of an optional stiffener. I’m installing the stiffener which will sit above the horizontal cut made in the corrugated F-1207F bulkhead cover. The stiffener is angle aluminum that has a slight taper for weight savings. Enlarging the photo below, the taper can be easily seen. Hole positions were marked and the stiffener was drilled to #40 first … then the stiffener was positioned on the F-1207F bulkhead cover and match drilled onto the F-1207F bulkhead cover, followed by final drilling to #30.

Match drilling #40 the optional baggage bulkhead stiffener to the corrugated F-1207F bulkhead cover.

Today’s work session completed the fabricating, cutting, deburring, drilling and dimpling of parts for the baggage bulkhead modification. By the time the finishing touches were made to the parts, it was a little to late to prime parts today. Hopefully, I can get at it early tomorrow and get some primer sprayed before heading to Oshkosh for AirVenture.

Modification Cuts To F-1207F Bulkhead Completed

Bernie came by yesterday and it was perfect timing ... in that he was able to hold the newly fabricated horizontal angle for the baggage bulkhead modification in place while I match drilled it into the F-1207F baggage bulkhead cover. All but the two holes adjacent to the right bulkhead frame were match drilled while the angle was in position on the bulkhead cover. The F-1207F bulkhead cover was then removed from the bulkhead frame so the last two holes could be match drilled.

Match drilling the remaining two predrilled holes in the angle into the F-1207F bulkhead cover.

After all the holes for the horizontal angle were drilled, the three screw holes were enlarged to #19. Decided it would be OK to use the jig saw outfitted with a 24 teeth per inch metal blade to make the horizontal cut in the F-1207F corrugated cover. The cut was made on the peak of the ridge on the F-1207F cover. The horizontal cut was done first followed by making the vertical cut on the band saw.

Using the jig saw outfitted with a 24 tpi blade to make the horizontal cut in the F-1207F bulkhead cover.

As mentioned in a previous post, the cut line at the bottom of the F-1207F cover needed to be offset to allow for proper edge clearances for the existing mounting screw hole. I started the cut at the midway point between the existing nutplate hole and the newly added nutplate. The necessary offset can clearly be seen in the photo below.

Finished horizontal and vertical cuts in the F-1207F baggage bulkhead cover for the modification. My finger is pointing to where the small offset is located.

Now that the bulkhead parts are cut, hoping the weather cooperates so a coat of primer can be sprayed on all the parts. Leaving for the AirVenture show in Oshkosh in just a few day, so would like to have the parts primed and coated with JetFlex.

Modifying F-1207F Corrugated Bulkhead Cover

Today work began on modifying the F-1207F corrugated baggage bulkhead cover. There are a few ways to go about this, but felt it best to first mark the cut lines on both sides of the F-1207F cover and drill all the necessary holes first, then make the horizontal and vertical cuts last … this should insure all the pieces fit together nicely when finished.  Because of the size of the F-1207F baggage bulkhead cover the band saw can only be used for the vertical cut. The small 45 degree transition between the vertical and horizontal cuts will require a small cutting wheel on the Dremel and the horizontal cut will be done either by hand or using a jig saw … still thinking about that.

Before drilling the newly fabricated vertical angle the part was painstakingly marked, checked and rechecked. Four lines were drawn down the length of the angle … two lines for the two rows of rivets that are slightly offset from one another, a line to mark where the dimpled holes will be for the #8 screws and a fourth line to denote where the cut line will be so the angle can be properly positioned over the cut line on the F-1207F baggage bulkhead cover prior to drilling. Once all the lines were drawn, the rivet and screw holes were marked, center punched and small lead holes were drilled then enlarged to #30.

Drilling lead holes in the newly created angle for the F-1207F’s vertical cut necessary for the modification. Zooming in on the photo one can see three red lines used to place rivet and screw holes correctly and a green line which denotes where the cut line will be. The green line will offer a visual aid for positioning the angle over the cut line marked on the F-1207F baggage cover… then the parts can be match drilled to each other.

The vertical cut will be made 8 ¼" in from the passenger side of the F-1207F baggage bulkhead. The horizontal cut will be made along the peak of the third corrugation up from the bottom. A 45 degree transition will be incorporated between the vertical and horizontal cuts.  As with the previously completed baggage floor, a small offset will be necessary around the existing screw hole on the bottom of the cover. The third photo below shows the issue clearly … the vertical cut line almost catches the edge of the bottom screw hole. As with the baggage floor, a small offset will be made to the right side of the aircraft.

Marking the location where the vertical cut in the F-1207F will begin.

Laying out the cut lines on the F-1207F baggage bulkhead cover.

The vertical cut (red line) will be made 8 ¼" in from the passenger side of the bulkhead. The necessity for the yet to be drawn offset can be clearly seen where the cut line meets the base of the F-1207F.

After taking a lot of time to measure & check … measure & check, seemingly ad infinitum, the angle for the modification was match drilled into the F-1207F baggage bulkhead cover. The #40 holes drilled and Clecoed first, then the holes were enlarged to #30 and the nutplate screw holes were drilled to #19 for a later dimpling for #8 flush screws.

Match drilling the holes in the new angle into the F-1207F baggage bulkhead cover.

I was hoping to get to cutting the F-1207F cover today but there were “honey do’s” and company at one point, so lost quite a bit of shop time … plus, I was working at a snail’s pace trying to be very careful and get it right the first time.

Baggage Bulkhead Modification Work Continues

Forgot to mention in the last post that the F-1206G-R rib that the newly made angle will attach to has a slight skew from vertical. When over at Steffon’s fabrication shop bending the angle, I remembered that the baggage rib has a slight angle but did not remember which way it went so I purposely under bent the angle in the brake. As it turns out it actually needed to be bent slightly past 90 degrees … so quite a bit of time was spent putzing around tweaking the angle with seeming tools and a mallet to get it in the ball park. So builders inclined to do this mod should bend the angle to a little past 90 degrees.

After the angle was in the ball park it was then positioned onto the F-1206G-R baggage rib and drilled in place. The rivet holes really can’t be evenly spaced because there is a large flanged lightening hole and a tooling hole on the F-1206G-R baggage rib that infringe on the minimum edge clearances suggested for rivets … plus I did not want to drill into the flange the lightening hole has ridge around it. Long story short, care needs to be exercised when drilling the four rivet holes into the F-1206G-R baggage rib. Pilot holes were drilled into the angle and then it was clamped onto the F-1206G-R baggage rib and match drilled.

Drilling small pilot holes into the modification angle that will be used to match drill into the F-1206G-R baggage rib.

With the new modification angle clamped in position, the angle was match drilled into the F-1206G-R baggage rib.

New modification angle drilled and held in position on the F-1206G-R baggage rib with Clecos. The aforementioned flanges around the lightening holes can be clearly seen here

The F-1206E baggage floor was cut 3/8" towards the right side of the airplane from the center line of the existing mounting holes for the F-1206G-R baggage rib. Caution: Measure and make cut marks from the centerline of ALL THREE screw holes then draw a straight cut line connecting the three marks. The holes in my F-1206E have a small offset from front to rear … so measuring from the centerline of each hole and drawing a line will keep the cut parallel to the edge of the existing baggage rib. The idea here is to make the cut directly over the point where the new angle meets the F-1206G-R baggage rib.

Because the cut will get close to the existing mounting hole on the aft flange of what will become the left half of the F-1206E baggage floor, a small 5/16" offset was marked to the right side of the aircraft. Next the back edge or flange of the F-1206E was cut through on the band saw. Then the small offset line (approximately 3/8" long) was  scored using a Stanley razor blade knife to weaken the aluminum. Next the band saw was used to make the long cut up to the scored area. A slight amount of light bending caused the aluminum to separate at the score line.  After the F-1206E baggage floor was cut in two and deburred, the small piece that will reside under the fuel tank was set in place and screwed in position so it could be match drilled into the new mounting angle.

Drilling pilot holes through the F-1206E into the new angle for the three mounting holes. Looking closely at the left panel one can see the offset mentioned above.

Final drilling the three mounting holes to #19.

After the mounting holes for the right half of the F-1206E baggage floor were drilled, the #19 holes were dimpled for #8 flush screws ... plus holes were drilled and dimpled for K1100-8 nutplates. An additional nutplate was installed just to the right of the offset to offer support for the edge of the right F-1206E near the offset cut.

Using the pneumatic squeezer to install the new K1000-8 nutplate in the F-1207B bulkhead which will support the right half of the F-1206E baggage floor and the yet to be cut portion of the corrugated baggage bulkhead cover.

Dimpling the three new #19 mounting holes in the right half of the F-1206E for #8 screws.

After all the cutting drilling and dimpling the newly created left and right F-1206E baggage floors fit nicely. Next work session will focus on the baggage bulkhead cutout.

The newly separated left and right F-1206E baggage floors fit nicely together. My finger is pointing to the newly installed nutplate/mounting hole … the offset mentioned above can be clearly seen to the right of my finger after expanding the photo to full size.

Baggage Bulkhead Modification Underway

Working around all the rain storms, was finally able to get all the parts that were recently prepped covered in primer … and those parts that are interior components, covered with JetFlex water reducible paint. Painted all the interior panels with JetFlex WR except for the corrugated F-1207F baggage bulkhead cover and the F-1206E baggage floor cover. These two parts were not painted because they will be cut as part of the bulkhead modification being incorporated by DOG Aviation so will spray them after cutting.

An interesting situation with JetFlex. As is typical, I did not take any photos of the spray session … (like to keep the camera far away from spray painting activities) so I don’t have any photos to share, but I did have an experience I will share.  While painting with the JetFlex WR paint I accidentally dragged the air hose across a wet panel and slopped up the paint.  I finished painting another panel which took about a minute or two tops and grabbed the messed up panel, quickly soaked a towel in the ammonia & water cleaning solution used for cleanup and began wiping the panel down to the primer. This went well except when the paint turned into a very thin film it seemed to instantly dry in place. No amount of scrubbing with the solution would cut through the thin film so I just dried the part off and re-sprayed the panel … turned out nice.

Then a few minutes later, while spraying a second coat on another part, the paper part number label was blown onto the paint by the HVLP spray gun. Oh Great! Another screw up! So I grabbed another towel, soaked it in the ammonia and water solution and began trying to wipe off the paint … but to no avail. The JetFlex would not come off with a towel to smooth out the area where the part label stuck to. Ended up using 320 grit wet-or-dry sand paper with the ammonia solution to successfully feather out the bad spot and then re-sprayed. Have to say, JetFlex keeps amazing me at how tenacious the paint is for being a water reducible paint.

The baggage bulkhead modification: History, … builders of the RV-12 have come to realize that when the fuel tank is installed, it covers the mounting screw holes for a portion of the corrugated F-1207F baggage bulkhead cover and also the F-1206E baggage floor cover. During annual inspections, fuel tank removal is required to gain access to the screws so both panels can be removed to allow access to areas that require inspection during the annual. As such, quite a few builders have been making modifications that allow removal of the panels without the need to remove the fuel tank. At DOG Aviation we embrace modifications that make good sense and this is one of those modifications that makes good sense to me. Because the DOG Aviation RV-12 is being built under E-AB rules, this modification will be incorporated into the build now as opposed to later. The two photos below are of another builder’s modification to show what the modification will look like when finished.

RV-12 baggage bulkhead modification made by Rob from Perth Australia. The piece sitting on top of the bulkhead will be permanently covered by the fuel tank. The rest of the bulkhead cover will unscrew from the new nutplates attached to it.

Back view of the aft side of Rob's baggage bulkhead showing the modifications Rob made to his RV-12 baggage bulkhead cover.

There have been several methods used by builders to complete the bulkhead modification, but Rob’s modification caught my eye and sensibilities … so I contacted Rob to ask for measurements for the cuts. I did this because the fuel tank is not built yet, so did not know exactly where it will be positioned. Most builders just use flat aluminum, however Rob's design uses aluminum angle to add strength to the area of the cutout and finishes off by using countersunk screws for even more strength. As it turns out, Rob is an engineer (no wonder I liked his modification method) from Perth Australia. Rob was more than happy to pass along the measurements for the cuts and as an added bonus, the dimensions for the angle doublers as well … many thanks Rob! That was an unexpected nice surprise.

Today work began on making the components necessary for the baggage bulkhead modification. Sheet aluminum .040 thick was cut for the doublers, deburred and a taken to a fabrication shop to bend on a brake.

About to begin cutting a long strip of aluminum from a .040 sheet which will make the three doublers for the F-1207F and F-1206E panels.

Using the band saw to separate the three doubler pieces that will be made into angles on a brake.

Rob used .025 aluminum to make a stiffener for above the horizontal cut in the baggage bulkhead … unfortunately, the closest size the DOG Aviation stock room had was .032 so that is what was used to make the bulkhead stiffener a little overkill here. After all the parts were cut out on the band saw, Mike came by and the two of us went over to his friend Steffon’s fabrication company to use his metal brake for bending the pieces  into angles … thank you Steffon for the use of your brake to bend the parts ... could not have made them that precise or as easily at the DOG Aviation shop.

The three .040 doublers and one .032 stiffener that will comprise the parts necessary to make the modification to the corrugated F-1207F baggage bulkhead and F-1206E baggage floor cover.

The photos of Rob’s modification clearly show what will be done to the F-1207F bulkhead panel but do not show the modification for the F-1206E baggage floor. Basically, a piece of angle is attached onto the existing baggage floor rib to create a point to screw down the yet to be cut portion of the F-1206E baggage floor which will remain under the fuel tank. The photo below shows how the newly made angle will attach onto the existing rib and my finger is pointing to where the cut will be made in the F-1206E baggage floor … basically on the line where the angle will attach onto the existing baggage floor rib.

Holding the newly made angle in position and pointing to where the F-1206E baggage floor (shown in the foreground) will be cut.

Still need to drill holes and dimple where necessary plus make the cuts on the F-1207F and F-1206E panels … so there is still a few hours of work needed before the modification is completed and the cut panels can be painted with JetFlex.

Readying Parts For A Primer Session

Although not having updated the Blog for quite a while, progress has been made … in that most all the loose parts have been separated (if necessary), deburred, and in a few cases dimpled or machine countersunk as necessary. Most of the work sessions leading up to the Holiday weekend were small and did not merit a daily entry into the Blog.

The weather earlier this week has not been good for painting but tomorrow promises to be a good day for blowing the dust off the HVLP spray gun and laying down some Akzo primer. I actually was hoping to do that today but while going through some paper parts bags discovered more items that needed to be prepped for primer in addition to the previously mentioned trim servo mounting components shown in some of the following photos.

Deburring the edges of one of the trim servo’s F-1287B doublers with a file.

Deburring the edges of the F-1287A servo tray with the 1" ScotchBrite wheel.

Separating the F-1258 rudder cable links with a hand hacksaw.

After deburring all of the parts that need priming during the upcoming primer session, went through the plans and identified those parts which require dimples or machine countersinking … since it is best to dimple or countersink prior to priming, those parts were processed accordingly based on their requirements.

Dimpling the nutplate rivet holes on the F-1228 seat floor cover with the pneumatic squeezer.

Machine countersinking the nutplate rivet holes on the F-1294C tabs used for mounting the tail cone faring.

With the exception of the baggage bulkhead cover slated for a modification prior to priming and a couple of miscellaneous small parts that can be easily primed with an air brush, everything should be primed by tomorrows end. Hope it is not really hot tomorrow, because it looks like the paint suit and respirator will be my attire for the day.

Everything on the workbench is deburred, dimpled or machine countersunk if necessary and now ready for an Acetone cleaning, scuffing with a maroon ScotchBrite pad, another cleaning with Acetone and on to primer.

Will post a detailed description of the baggage bulkhead cover modification in an upcoming post after some parts are cut from raw aluminum stock and bent to shape on a metal brake.

Part Search Reveals More To Deburr & Prime

Thought all the deburring of parts was out of the way and now just waiting for a couple of rain free back to back days to prime and paint. Then I remembered there were some small tabs stored in a plastic storage tray that will attach to the fiberglass tail cone which will also require priming. Upon opening the storage tray discovered there was much more – all of the parts that attach the electric trim motor and linkage onto the tail cone. Those parts had been forgotten about because they were in the storage tray along with the trim motor.

Discovered empennage parts for the electric trim system that need separated on the band saw. Metal strip on the right will become the mounting tabs for the fiberglass tail cone after cutting.

Separating the F-1287D clevis plates on the band saw.

Sure glad I remembered about the tabs for the fiberglass tail cone because had I not opened that plastic storage tray looking for them, would have totally missed priming quite a few small parts that will be needed in the near future.

ADAHRS Stiffener Modification

As mentioned last week ,Van’s has finally begun shipping the long awaited for ADAHRS stiffener modification. The modification was developed because some builders were getting some jittery screens on the SkyView and in particular the “ball” on the slip indicator. The issue was isolated to the tail cone skin being quite flexible in the area of the mounting brackets for the ADAHRS unit. Apparently, prop wash is causing that area to flex and vibrate a bit … which is affecting the quite sensitive magnetometer within the ADAHRS unit. The Van’s fix is to add a small stiffener bulkhead just forward of the ADAHRS mounting brackets to remove the flexing of the tail cone’s skin in that area.

The part number for the kit is 12SVAHRS Rib Kit. The kit consists of one F-00062 stiffener bulkhead, 13 rivets, and an instruction sheet to go into the construction manual.

ADAHRS stiffener kit - basically it is only one stiffener bulkhead which is riveted onto the top skin on the tail cone.

Instillation of the kit is simple if the stiffener bulkhead is installed prior to mating the tail cone onto the fuselage. Those who already have the tail cone mated to the fuselage will have more of a challenge installing the stiffener. Because the tail cone has already been constructed, one rivet had to be removed so the F-00062 stiffener bulkhead could be attached to the tail cone’s upper skin. After removing the rivet and securing the stiffener to the tail cone’s upper skin with a Cleco, the remaining rivet holes in the stiffener were used to match drill the tail cones upper skin.

I asked Mike to come over and give me a hand which made things easier. Because the stiffener is quite flexible, I clamped a piece of 90 degree bent aluminum behind the web of the stiffener to keep it straight. After the center Cleco was installed a measurement was made from the center of the stiffener to the forward edge of the tail cone skin. With Mike’s help taking measurements, we worked out from the center keeping the rib in position while match drilling the rivet holes in the rib into the tail cone’s upper skin.

Match drilling the F-00062 ADAHRS stiffener bulkhead into the tail cone’s upper skin.

The F-00062 drilled and secured in position with Clecos. For what it is worth, the stiffener removed all flex in the area of the ADAHRS mounting brackets … so it looks like job well done Van’s.

After the match drilling was completed, the ADAHRS stiffener bulkhead was removed so all the holes could be deburred. Those building their RV-12’s as E-LSA are ready to prime and rivet the stiffener bulkhead onto the tail cone at this point.  However, because the DOG Aviation RV-12 is being built with flush rivets, one additional step is required … dimpling the newly drilled holes in the tail cone along with dimpling the rivet holes on the flanges of the F-00062 stiffener bulkhead for flush rivets. For dimpling the holes in the tail cone’s upper skin, the 120 degree dimple dies that have a hole in them for a nail were used with a hand rivet puller to hand squeeze the dimples into the upper skin. The stiffener bulkhead was dimpled with the pneumatic squeezer outfitted with 120 degree dimple dies.

Mike holding the nail and female die in position as I pull on the nail with a hand rivet puller which compress the male die into the female die to create the dimple.

Dimpling the rivet holes in the F-00062 ADAHRS stiffener bulkhead for 120 degree flush rivets.

Now that the rivet holes in the flanges of the ADAHRS stiffener are dimpled, the stiffener is ready to be included in the upcoming primer session and will get added to the pile of parts. The last few days have been spent deburring the pile of parts that were retrieved from the hangar. All the parts are deburred now, but a few require some dimples where nut plates will attach … so will try to do get all that out of the way prior to priming.