The 30 Mile Dimples

There are six F-1212 step ribs, three left and three right. The six F-1212 ribs required deburring and some dimpling. Per the plans, the two F-1212 ribs that will become the centermost two ribs receive 120 degree dimples along the entire top flange of both ribs … because they will become a portion the tunnel and a removable cover plate will sit on top of them. The bottom most rivet hole in the forward flanges of the outer most rib on each side also received a 120 degree dimple. In addition, all of the F-1212 L&R ribs received 120 degree dimples in all the rivet holes of the bottom flange to accommodate the flush rivets being used on the RV-12 project.

                Using the Scotch-Brite wheel to remove burrs and smooth edges on one of the six F-1212 step ribs.

                                                 Dimpling one of the F-1212 ribs with the pneumatic squeezer.

                    Bottom flange of all F-1212-L&R ribs were dimpled for flush rivets being used on the RV-12 project.

And now for the 30 mile dimples … overall the DOG Aviation procurement department has done a great job amassing the necessary tools and specialty items required to bring the RV-12 to fruition. One tool which was overlooked was a set of #40 dimple dies for 3/32” rivets that are the type with the holes in them used with a hand rivet puller … or the type that has the dimple dies welded onto the end of a vice grip. The shop is outfitted nicely with various dimple die sets for #30 rivets but only has one set for making #40 dimples using a typical rivet squeezer with a yoke.

As luck would have it, the W-1226-L&R floor pans required quite a few dimples … however, there were two dimples on the front edge for a nutplate that the tools in the shop just could not reach. The edge on this piece of metal is bent way more than 90 degrees so there is not enough clearance for the squeezer yoke to get low enough to allow the dimple die to align with the hole.

This photo shows how the tight bend interferes with the squeezer yoke preventing the dimple die from getting low enough.

Tom to the rescue …. I contacted a fellow RV builder who is building a Van’s RV-10 (a beautiful four place aircraft). Tom lives around 15 miles away and had two types of #40 dimple dies that would do the job … so the two F-1226 floors were packed up and carted over to Tom’s house and dimpled there. The tool that was used to make the dimples resembles a vice grip which has a set of dimple dies welded onto the end of the jaws. Fortunately, there was just enough room for the tool to fit and the rivet holes for the nutplate on both floors were successfully dimpled. Sadly, I forgot to take my camera to Tom’s so don’t have photos of the tool used to form the dimples or of his project to share. Thanks Tom!!!.

                              Dimples in the F-1226-L&R floors made at Tom’s house are circled in red.

The last item to be worked on before the next primer session is the W-1202F bulkhead. The edges were deburred and Smoothed on a Scotch-Brite wheel then the nutplate rivet holes on the top flange were dimpled. In addition, the bottom flange and the side flanges were dimpled for the 120 degree flush rivets being used on the RV-12 project.

                               Making 120 degree dimples in the bottom flange of the F-1202F bulkhead for flush rivets.

                                  Pile of parts ready for cleaning, scuffing with a Scotch-Brite pad and priming.

F-1203A Bulkhead Prepared

The pile of parts that were prepared over the weekend were cleaned, scuffed up with a Scotch-Brite pad, wiped down with Acetone and primed Monday … it was a productive day and all hanging locations in the shop had painted pieces hanging from them.

To make the most of more upcoming good spray painting weather, decided to continue preparing parts for primer and top coating as necessary. Next up was the F-1203A Bulkhead which required quite a bit of attention. There are three side by side holes at the center bottom of the bulkhead that require being enlarged to 7/16” and two adjacent holes that required being enlarged to 3/4". Step drills are a great choice in this situation, so the drill press was outfitted accordingly and the drilling commenced.

Using the drill press outfitted with a step drill to enlarge one of the holes in the F-1203A bulkhead to 3/4".

The plans call for lots of machine countersinking on the forward side of the F-1203A bulkhead … a total of 46 rivet holes for AN426AD3 rivets to secure nutplates and 6 #30 holes along the top edge for 120 degree flush pop rivets.  In the photo bellow, the areas that require work are outlined in red … the 46 #40 rivet holes are circled in red and the 6 #30 holes requiring 120 degree machine countersinking are marked in green.

Holes in the F-1203A bulkhead requiring machine countersinking marked & ready to meet the machine countersink cage.

                              Machine countersinking one of the fifty two holes in the F-1203A bulkhead per the plans.

The F-1203A bulkhead is made from .040 aluminum … this is near the upper suggested limit for dimpling. Thicker materials are usually machine countersunk but the decision has been made to dimple the bottom of the bulkhead for the flush rivets that are being used on the RV-12 project. The bottom flange of the bulkhead is not quite 90 degrees so knowing thicker material tends to flatten out a little when dimpled, an angle gage was used to measure the angle before dimpling so that angle can be reset after dimpling.

Dimpling the bottom flange of the F-1203A bulkhead for the 120 degree flush rivets being used on the RV-12 project.

The dimpling process relaxed the bend of the flange only a few degrees so it was tapped back into place with a soft hammer. Next the flange angle was checked to verify it is now at the same angle as it was prior to dimpling.

Checking the angle of the F-1203A bulkhead flange after dimpling and subsequent adjustment to verify the angle is the same as prior to dimpling.

Even though the autopilot will not be installed until much later, the RV-12 forum consensus is to install the autopilot mounting brackets now while building the fuselage as opposed to installing the brackets afterwards. The autopilot bag was opened and the brackets were removed, deburred and prepped for primer.

            Almost done smoothing the edges of one of the autopilot servo mounting brackets … four down one to go.

Preparing More Fuselage Parts For Primer

While waiting for the JetFlex paint to fully cure decided to move on by preparing more fuselage components for primer. Looking ahead in the plans, decided to prep a pile of parts that most will only require primer and basically go under the seat and baggage floors or are part of the lower fuselage. Think I may have gotten a little carried away because there is now a large pile of parts to prime tomorrow.

There are quite a few parts which required being separated on the band saw, then dressed on the large Scotch-Brite wheel followed by hand massaging with small files and abrasives.

Using the band saw to separate F-1253-L&R side pieces the seat pan edges will mount onto.

Separating the pile of seat belt mounting strips which will attach to the seat pan ribs.

 

Many various pieces were run through the band saw creating numerous piles of parts which required dressing on the Scotch-Brite wheel followed by hand massaging.

 

Using the Scotch-Brite wheel to smooth the edges of the freshly cut metal parts.

 

Reading ahead in the plans reveled many of the small parts required dimpling and/or machine countersinking. All of the small parts which attach to the side skins or bottom skin were dimpled for the 120 degree flush rivets being used on the RV-12 project. In addition, many of the small parts required dimpling and/or machine countersinking which ended up being a bigger task than originally anticipated.

 

Due to the angle of the flange in this piece, it required using the 120 degree dimple dies which have holes through the center. A nail is placed through the dimple dies and pulled by the hand rivet puller … thus squeezing the dies together to form the dimple.

 

Using the pneumatic squeezer to place dimples in the bottom of one of the aft baggage floor ribs.

 

Because the decision was made not to install flush rivets in the area where the side skin doubler plates will be installed, (it will be hidden by the wing) when dimpling the F-1253-L&R pieces for flush rivets the aft most 8 holes were not dimpled … this is because they reside within the area of the side skin doubler plate.

 

F-1253-L&R pieces dimpled for flush rivets except for the aft most 8 holes.

 

Dimpling the bottom of the F-1206 bulkhead for the flush rivets being used on the RV-12 project.

Machine countersinking one of the four the F-1233B-L&R pieces.

 

 

The fruits of the last few days of labor can be seen below. All the parts are now fully deburred, dimpled and/or machine countersunk if necessary and are ready for a cleaning with Acetone and roughing up with a Scotch-Brite pad followed by more Acetone and on to the paint department for a shot of primer.

Pile of parts ready for a Scotch-Brite pad attack , Acetone cleaning and off to the paint department for primer.



Sherwin-Williams JetFlex – First Impressions

The last couple of times the paint box was used I noticed debris landing on the freshly primed surface. At first, thought the debris was coming from a neighbor’s messy tree, but towards the end of the primer session I actually saw debris being kicked up from inside the spray box as the spray gun passed beyond the edge of the material being painted.

The spray box required a good cleaning … hind sight being 20/20, the spray box should have been built with a hinged top to make this task easier. Amazingly, the over spray on the bottom and sides of the box came off quite easily with a wire brush. It was just a bunch of powder and had not really stuck to the wood.

Bottom of spray box before cleaning the built up primer can easily be seen.

 Spray box after cleaning with a wire brush … almost looks like the day it was built.

 

Yesterday marked the first big primer session for the RV-12’s fuselage components. Once again Akzo primer was used on the parts for the center channel, fuselage ribs, along with the seat and baggage floors. The current plan is to top coat the interior parts prior to riveting so today was spent spraying Sherwin-Williams JetFlex which is a polyurethane interior spray paint made to Boeing specifications. A lot of good things have been said about JetFlex on the forums, so decided to give it a try.

 

JetFlex is available in two versions ... solvent based and water reducible. Because the solvent based JetFlex has isocyanates (which respirators do not filter out) decided to go with the water reducible JetFlex.

 

Sherwin-Williams JetFlex – First Impressions …. Boy this stuff is thick! The consistency of a thick, creamy smooth, pancake batter comes to mind. The JetFlex can says to thin 10-20 % with distilled water, so I opted to go for 15% which ultimately worked out well.  I have never sprayed a water reducible polyurethane paint before so have been hoping my spray equipment would handle it. My spray gun has a 1.4mm spray tip which I feared would be too small. For individual smaller parts, such as the ones I’m working on, the 1.4 mm tip seemingly worked OK … but I feel if one were to spray paint very large surfaces, it may be hard to keep a wet edge unless a larger spray tip is used. I purposely adjusted the gun to spray a smaller pattern than usual and opened the material valve a little more than usual and was able to get a good spray pattern going.

 

The paint laid down nice and smooth … the parts look nice so far. The instructions say to spray approximately 3-4 mils thick (using two coats sprayed at 15 minute intervals) and after drying, the dry film is 1.2 – 1.6 mills thick. I hope I got it thick enough. The paint dries to the touch in 20-30 minutes, HOWEVER, full cure will be 2 weeks or more unless force cured at 140 degrees. Reports have been the paint is durable enough to rivet after three days or so. I only sprayed one coat to save weight but noticed one piece will need touching up because I got it a little too thin. Next time around will spray two thin coats.

 

Some parts a couple of hours after spraying with Sherwin-Williams JetFlex sandy beige water reducible interior paint.

 

Sherwin-Williams JetFlex – Second Impression … Boy this stuff is hard to clean up. If cleanup is any indication of durability, this paint will be rugged tough. A ladle was used to scoop 10 ounces out of the can to make the thinning math easy. The ladle had the thick paint wiped off with fingers and was left out in the air for no more than 4 or 5 minutes as a bucket of water was filled, then the ladle was dropped into the water and left for cleanup later. After the spray job, the ladle was removed from the water and the paint was not phased by the water … it would NOT rub off. Acetone softened it a little and small pieces would finally flake off. Colman lantern fluid (Naphtha based) would not cut it, nor would Denatured Alcohol. Lacquer thinner seemingly worked the best and many small pieces came off with rubbing until the ladle was clean.

 

Immediately after spraying, plenty of water was run through the spray gun which only washed the thick stuff out the chambers but there was still a thick film left in the gun the water would not budge. (This may be because air got inside the gun during paint refilling so next time will not run the gun totally dry before refilling). The spray gun was then cleaned with Lacquer thinner which removed the paint in small clumps … and it took FOREVER to totally remove all the film and flakes from inside the gun. And here I thought cleaning up Akzo primer was a tough (but doable with Acetone before full cure) cleanup … JetFlex takes that to a whole new level.

 

Admittedly, I may have brought some of the hassle on myself … after the cleanup I got on the computer and looked at the application data sheet which says if dried, use water and ammonia for cleanup as soon as possible. Wouldn’t have mattered much, had no ammonia on hand. But to be fair, I did not follow the cleanup directions per the data sheet, so will give the ammonia a try during the next JetFlex session before complaining more about the hassle of cleanup. Suspect it will still result in a clumpy mess, but I’m not a chemist so we’ll see next time around. Either way, JetFlex appears to have good fluid resistance and makes a good choice for aircraft paint. Once it totally cures after a week or so it is going to be a very durable paint.

 

Return from the future – Using a 50/50 solution of water and ammonia makes a HUGE difference in the ease of cleanup. Try not to let the gun run dry and when finished with the spray gun, immediately run the ammonia solution through the gun. Disassemble the gun and soak the parts in the ammonia solution and clean parts with brushes as usual.

DOG Aviation Acquires On-Airport Facility

Today marked a momentous occasion at DOG Aviation … the procurement department secured a roomy on-airport production facility which will become the new home of DOG Aviation to finish assembly and flight testing of the RV-12.

Mike and I at hangar 45, DOG Aviation’s on-airport assembly facility.

 Back story follows:

About this time last year, during a conversation with a representative for the FAA, it was mentioned I was planning to base the airplane at the local regional airport. I was told at that time phase one flight testing would not be approved from that location and I should look for another airport. This did not come as a big shock because I knew, based on my friend Pete’s RV9A project, quite a few southern California airports were off limits to him for his phase one initial flight testing. Knowing that, I never questioned his statement ... blind faith in authority I guess.

Move forward a year- in June I attended a pancake breakfast at what I felt would be my backup airport 30 miles or so away. The local EAA chapter had built a new hangar and had plenty of space available to build the RV-12 there … but after the airplane was built, it would need to me moved. However, the airport had absolutely no hangar space available and the prospects were slim to none. Needless to say, after hearing that bad news, I have been a little depressed lately and progress on the RV-12 has suffered somewhat.

Mike, a long time friend from the old neighborhood, hangars his airplane at our local regional airport and said he knew of a hangar that became available at the airport. Conveyed to Mike what I had been told about not being allowed to conduct phase one testing from there and therefore not interested in the hangar. Fortunately for me, during a session of hangar talk with a couple of RV owners, Mike asked them if they completed phase one testing at the airport … one of the two said he had indeed completed his phase one testing from the airport, all be it a few years ago, but he was not aware of any policy changes.

Hearing that great news, I immediately placed two phone calls to the FAA’s Cleveland FSDO and spoke to a gentleman in operations and also a field inspector who issues airworthiness certificates. Both gentlemen said that because the airport has many miles of open area to the south, there would not be any issues with conducting phase one flight testing from the airport. However, because it is class C airspace, the RV-12 would be required to have a radio and transponder … no problem, it will. I was also told it is possible, but unlikely, that the airport authority may have restrictions of their own … so it was suggested I should verify with them as well. Mike and I paid a visit to the airport authority and after an employee there made a few phone calls up the chain of command, the result was a green light for the RV-12 project.

Upon hearing the good news of no phase one flight testing barriers at the airport, hangar 45 was immediately secured and will soon become the new DOG Aviation facility for RV-12 assembly and ongoing flight operations. Many thanks to Mike for all his help in making this happen.

Newly acquired key to Hanger 45, the future on-airport home of DOG Aviation.

Plenty of room here for the RV-12 to stretch her feathers.

Countersinking Bulkhead Side Assembly

While waiting for two back to back days of good spray painting weather and in an effort to make breaking out the spray gun worthwhile, many parts have been deburred and prepared for paint. Hoping the coming few days will pan out as forecasted so priming and top coating can FINALLY get accomplished.

In the mean while, to accommodate the flush rivets being used on the RV-12 project, the rivet holes in the flange on the F-1204CL L&R forward bulkhead side assemblies required machine countersinking where the side skins attach.

                                   Machine countersinking the flange of one of the F-1204CL forward bulkhead
                                   assemblies using the countersink cage outfitted with a #30-120 degree bit.

The seat floors will be top coated and since there are seat back hinges which attach to them,  decided to fabricate the hinges at this point in time so they can be top coated as well. The plans call for a 20 inch piece of AN257-P3 hinge … however, other builders suggest cutting 20 1/2 inches to have a ½ inch as an insurance policy. Both halves of the hinge are then cut to 10 inch lengths resulting in 4 hinge pieces. Unfortunately, the 20 1/2” piece of hinge was too big for the band saw and needed to be cut by hand.

                                   Cutting the AN257-P3 hinge pieces with a hacksaw to 10” lengths.

Once the four hinge pieces are cut to size, a line is drawn on the back side 1/4” in from the edge and one end of each hinge is marked for a #30 hole a 1/4” in from the edges.

                       Backside of hinge pieces marked for #30 hole and centerline drawn for match drilling.

                           After center punching and drilling a small pilot hole the #30 holes were drilled.

The number #30 hole that was drilled is then used to attach the hinge piece to the F-1225 seat floors. The line drawn on the back of the hinge is then centered to the holes on the seat floor, taped in place, match drilled and secured with Clecos.

One hinge done one to go … centering line drawn on back of hinge is centered in seat floor holes and match drilled.