Wednesday, October 30, 2013

F-1206A Bulkhead Riveted In Place

Yesterday, not too very much was accomplished on the RV-12 construction … but progress was made. The weather was accommodating for a small JetFlex spray session. Looking forward in the plans reveled a portion of the longerons aft of the canopy deck would be visible from inside the cockpit, so decided to spray that portion of the longerons with JetFlex. Also did the narrow strip on the instrument panel base where the front panels attach. Not sure if it will be visible, but just in case there are any gaps the primer will not show.  It took far far longer to cleanup the spray gun than it did to spray the paint.

Some progress was made on the fuselage construction and the F-1206A bulkhead that was previously Clecoed in place was riveted onto the F-1222 and F-1223 baggage ribs using mostly solid AN470AD4-4.5 rivets.

Riveting the F-1206A bulkhead onto the baggage ribs with the pneumatic squeezer using AN470AD4-4 rivets in place of LP4-3 pop rivets.
F-1206A bulkhead riveted in place onto the F-1222 & F-1223 baggage ribs … only two pop rivets were used where the squeezer could not reach.

The short F-1206G-L&R ribs were also riveted in place unfortunately access was not good for squeezing solid rivets into them so they were riveted in place using LP4-3 pop rivets. The clearances were tight, so here again the rivet mandrels were slightly bent and the AEX wedge was used to set the rivets.
Riveting one of the F-1206G ribs in place using the AEX wedge and a hand rivet puller.
F-1206G ribs riveted in place with LP4-3 pop rivets.

I’m almost embarrassed to admit just how much time was wasted trying to figure out a way to rivet the F-1206D bearing bracket assemblies onto the F-1206G ribs using solid rivets. I tried every yoke and squeezer combination and I just did not feel comfortable attempting the task. One or two of the seven rivets could probably have been done with ease but the others all offered unique challenges and the rivets would have been long and for those especially the squeezer needs to be on them as straight as possible. In the end, I felt the risk reward was too great because access to drill out one of the rivets should something go wrong was not good ... so ultimately used LP4-5 pop rivets per the plans to attach the assemblies.
F-1206D bearing bracket assembly attached onto the F-1206-G rib.

Because of all the wasted time previously mentioned, only had time to rivet one bearing bracket assembly in place … so when work resumes in a few days, the remaining bearing bracket assembly will be riveted in place along with the F-1206H ribs that are now Clecoed in place.

Sunday, October 27, 2013

Baggage Ribs Riveted In Place

Getting the baggage ribs riveted to the F-1204F aft bulkhead presented yet another challenge. The plans instruct the builder to place the manufactured head of the LP4-3 rivets securing the six baggage ribs on the F-1204F aft bulkhead which creates a small issue with clearance. The close quarters rivet puller will not work at all … when working between the bulkheads there is not enough room to open the handles far enough to grip the rivet for the second pull it typically takes to pop the rivets. Fortunately, the DOG Aviation procurement department had also purchased a Stanley rivet puller with a swivel head. There was just barely enough room for the Stanley rivet puller with the head swiveled 90 degrees … and the lower three rivets still required the trick of bending the mandrel of the rivet and using an AEX wedge to allow the rivet gun access so the handles would clear the forward bulkhead.

Using the Stanley rivet puller with the AEX wedge to get enough clearance for the rivet puller … the blue aluminum piece is leftover scrap used to prevent scratches.
 Even the upper rivets are a tight fit for the rivet puller.

After the W-1221,22 and 23 baggage ribs are riveted onto the F-1204F center section's aft bulkhead, the baggage floors were riveted in place and nutplates were riveted onto on the W-1221-L&R ribs. The nutplates are for the removable inspection plate which will cover the tunnel.
 Riveting the baggage floors onto the F-1222-L baggage rib … blue tape is used to protect the paint.
 Using the pneumatic rivet puller to set the last rivet into the F-1224 baggage floor to F-1223-R baggage rib.
                                                               Installing the nutplates onto the W-1221-L baggage rib.

Moving forward, the next task was to prepare the F1206A baggage bulkhead by installing the rear spar receptacles onto the bulkhead. The rear spar receptacle is comprised of the F-1206B rear spar supports and the thick F-1206C rear spar receptacle. The two pieces are typically riveted onto the F-1206A bulkhead with LP4-5 pop rivets … but access was good for the squeezer so AN470AD4-7 solid rivets were used in place of the pop rivets. This part of the aircraft receives the tab sticking out from the rear spar of each wing … the tab secures the aft most portion of the wing, so feel it is a good place to use solid rivets. The W-1206A bulkhead then received two nutplates and was ready to be installed.
Riveting the F-1206B and F-1206C parts onto the F-1206A bulkhead with AN470AD4-7 rivets to make the rear spar receptacle.

F-1206A baggage bulkhead assembly with both rear spar receptacles riveted in place with solid rivets as opposed to pop rivets.

The F-1206G-L&R ribs were also prepared for installation by riveting three nutplates onto each rib. These two ribs will be installed onto the F-1206A bulkhead assembly and will support a bearing bracket assemblies. The bearing bracket assembly is made up by sandwiching a Com-3-5 bearing between two F-1206D brackets and riveting the brackets together securing the bearing. Did not get to riveting the F-1206A bulkhead in place, but did get it secured with Clecos so it will be ready for riveting during the next work session in the shop .
Riveting nutplates onto the F-1206G ribs.
Two F-1206D bearing brackets with the Com-3-5 bearing in place ready to be sandwiched for all eternity.
Completed bearing bracket assemblies ready to be riveted onto the F-1206G ribs.
Setting the F-1206A baggage bulkhead in place for riveting.
                                                        F-1206A bulkhead Clecoed in place and ready for riveting.

Baggage Floors Riveted To Aft Bulkhead

Friday’s task was riveting the F1224-L&R baggage floors onto the F-1204D center section aft bulkhead. One row of solid rivets and two pop rivets … sounds easy enough right? But not so. Fellow RV-12 builders will want to make sure you have a helper and place tape or some sort of protective material on the baggage floors. Because my baggage floors have already been painted, I placed double layers of painters tape over the baggage floors. Even if you don’t prime or paint you will want to protect the baggage floors because they WILL get scratched otherwise.

So what is the big problem you ask? Well it is because the angle of the flange on the baggage floor where it meets the F-1204D aft bulkhead .… it is more than 90 degrees. This means even the Clecos are hard to get into the rivet holes … and when they do, both Clecos and Cloco pliers scrape against the F-1224 baggage floors going in and coming out. The baggage floors are always pushing on the Clecos.
One can clearly see the angle of the F-1224 baggage floor … this makes the floor push tight onto the Clecos.

Now for the fun part … the plans instruct the builder to set AN470AD4-9 rivets. OK what is the big deal? WELLLLLLLL because of the angle of the baggage floor’s flange the riveter (be it hand or pneumatic) needs to be outfitted with two flat rivet sets instead of the customary cupped set for the domed rivet head of a 470 rivet and a flat set to form the shop head. The reason for this is because there is NO WAY to get the riveter straight on the rivets.

Oh … it gets better. You really can’t even get close to being square with the rivet unless a second person is flexing the baggage floor backwards which then allows the hand riveter to ALMOST be in the proper position. I would not even consider using a pneumatic squeezer for doing this …think trying to control its position with all that weight would make the tough chore even tougher. Not to scare off future builders ... I'm making it sound harder than it was but it was challenging to be sure.
Jan lending assistance by holding the center section in place while flexing the F-1224-R baggage floor backwards which barely creates enough room for the hand rivet squeezer outfitted with two flat sets to get onto the AN470AD4-9 rivets.

The two outer most rivets on both F-1224 baggage floors are AN470AD4-10 rivets and are even more challenging … with the corner rivet being the toughest of the bunch to get onto square enough to squeeze. The domed 470 rivets now have flat spots on them from where the flat set was compressing the rivets … the flat spots can easily be seen in the upper row of rivets in the following photo. Note the plans have the builder install a LP4-3 pop rivet at the fifth rivet in from the right on both sides … the center channel has a recess at this location for the landing gear attachment, so the rivet is not going through the thick center channel material and there was no room in the recess to squeeze a rivet.
Upper row of AN470 rivets were squeezed with two flat sets bottom row squeezed with the customary cupped rivet set. The resulting flat spots can be seen on the top row compared to the bottom row.
Completed riveting of the F-1224-L&R baggage floors onto the F-1204D center section aft bulkhead.

If I had it to do over again, think partially setting the entire row of rivets without flexing the baggage floors back would be the way to go. The flexing tended to pull the flange off the center section so the riveter had to be pushed down to keep the flange flat. Even though the riveter would not be square on the rivets, partially setting the rivets to the point the flange is held down would be a good thing. The second pass could be done by pulling the baggage floors back so the riveter could get onto the rivet better without the tendency for the baggage flange to lift off the center section.

After the baggage floors were riveted in place, the F-1221-L&R, F-1222-L&R and F-1223-L&R baggage floor ribs were all Clecoed in place.
Securing the F-1221-L baggage rib onto the F-1204F center section aft bulkhead.
All the baggage ribs Clecoed in position and ready for riveting.

Friday, October 25, 2013

Section 20 Of The RV-12 Plans Completed

The construction of the RV-12's center section was completed yesterday, marking the completion of Section 20 of the RV-12 building instructions. Quite a few rivets of varying sizes go into the center section, so it takes a little while to complete the whole assembly.

The aft side of the F-1204 center section gets the F-1204D center section aft bulkhead and F-1204F-L&R aft side bulkheads riveted onto it. The instructions call for the builder to use various rivets depending on location … however, noticed the AN470AD4-4 rivets called out for the F-1204F aft side bulkheads were a tad short … had the necessary half size in stock, so they were substituted with AN470AD4-4.5 rivets that were on hand making for the perfect length. The plans have the builder placing four LP4-3 rivets in the lower four rivet holes on each F-1204F aft side bulkheads … I was able to get solid rivets into all but two rivet holes on each of the F-1204F-L&R aft side bulkheads ... the remaining two rivet holes were so close to the center channel the rivet squeezer could not get close enough to be square on the rivets.
Setting the F-1204D center section aft bulkhead in place to be secured with Clecos.
About to Cleco the F-1204F-L aft side bulkhead onto the F-1204 center section assembly.
Riveting the F-1204F-R aft side bulkhead onto the F-1204D aft bulkhead with slightly longer AN470AD-4-4.5 rivets which provided for a good shop head.

While attempting to squeeze rivets at the locations where there were three layers of metal, a small issue with the pneumatic squeezer came to life. It did not have enough power to squeeze the quite long AN470AD4-9 rivets. The issue is no fault of the pneumatic squeezer … it’s the way I have it configured. First, I like having an adjustable swivel/air valve on the end of the air hose. It can be used to slow the speed of the air drill for countersinking and deburring with the Scotch-Brite wheel or as a safety device for cutting off the air to a tool while changing drill bits, countersink cages, rivet sets, dimple dies, etc. While setting solid rivets with the pneumatic squeezer into the wing’s ribs, I found it necessary to add a second swivel to gain more clearance for the hose … but did not have a swivel only attachment, so a second air valve/swivel was attached onto the squeezer. Each of the air valve/swivels (even with the air valves full open) drop the pressure to the squeezer. This has not been an issue since the vast majority of the rivets so far have been a size 5 or less. But when squeezing rivets the lengths of 9 or 10, the reduced pressure won’t let the pneumatic squeezer develop enough power to set the longer rivets … with the current configuration a length of 8 appears to be the upper range. Not wanting to take the time to reconfigure the air hose or squeezer, the dust was blown off the hand rivet squeezer which ultimately did a great job of setting the longer rivets.
Using the hand rivet squeezer for the first time on the RV-12 project to set AN470AD4-9 rivets into the center section. It did a fine job!

After the F-1204F-L&R riveting was completed, the row of rivets securing the F-1204D aft bulkhead onto the F-1204 center section channel were riveted with AN470AD4-8 rivets on the left side and AN426AD4-8 flush rivets on the right side (think the flush rivets are for fuel tank clearances). Both of these rivets are also somewhat shorter than optimum for the location, so the shop head is smaller than ideal. Extra care was taken to not mar the paint while setting the flush rivets by using riveting tape to protect the paint.
Riveters tape placed over the AN426AD4-8 flush rivet to protect the JetFlex paint while setting the rivet.

The riveters tape did a marvelous job of protecting the JetFlex paint. Riveters tape has no adhesive in the center but has adhesive on the outer edges. Its true purpose is to allow  for back riveting of flush rivets. Flush rivets are placed into dimpled or countersunk rivet holes on a part. The part is then turned upside down and placed on a back riveting plate and the ends of the rivets sticking out of the backside of the part are pounded with a rivet gun from behind to form the rivet shop head, hence the name, back riveting. The tape has a two fold purpose … it prevents the rivets from falling out when the part is turned upside down and because there is no adhesive in the center of the tape, there is no adhesive to get mashed into the rivet joint. Riveters tape can also be used to protect a painted finish while setting a rivet with a pneumatic squeezer with flat sets ... which is why I used it to protect the JetFlex paint on the F-1204D center section aft bulkhead.
Riveters tape - available at Avery Tools and other fine aircraft supply businesses.
Using the pneumatic squeezer to set an AD426AD4-8 flush rivet into the F-1204D aft bulkhead making it one with the F-1204 center section channel. Riveters tape is being used to protect the JetFlex interior paint.

The last parts to complete the center section assembly are skin stiffeners, which are components of Service Bulletin 12-11-09. This service bulletin addressed two issues … it beefed up the landing gear mounting and also improved load distribution to the airframe. The four parts added onto the center channel during the work session are part of the load distribution component. The F-1204T-L&R and F-1204U-L&R stiffeners are added above and below the center channel with strong CherryMAX rivets which, in theory, are slightly stronger than a solid rivet. Of course, my center channel came with the mounting holes predrilled on the outer edges for the stiffeners, but my hat goes off to those builders that added this retrofit after the aircraft was built, I can tell that feat was not an easy task to be sure.
F-1204T&U stiffeners … part of the Service Bulletin 12-11-09. The stiffeners are to be installed above and below the outer edge of the center section channel.
Riveting the F-1204T-R and F-1204U-R stiffeners onto the F-1204 center section channel using CherryMAX rivets … a portion of Service Bulletin 12-11-09.

After completing the riveting of the F-1204T-L&R and F-1204U-L&R stiffeners onto both sides of the F-1204 center section channel, the center section assembly was completed and with that, Section 20 of the plans as well.
Completed Section 20 center channel assembly.

Wednesday, October 23, 2013

RV-12 Fuselage Assembly Begins

Now that it is time to begin assembly of the RV-12’s fuselage, thought it would best to first cleanup the shop a little and make room on the benches for the prints and tools. Got a late afternoon start in the shop and after a small amount of cleaning up along with a trip to have the propane tanks refilled, assembly of the RV-12 fuselage has begun.

Assembly of the fuselage begins by attaching four nutplates onto the F-1204 center section. Care must be taken because the two nutplates near the middle of the center section are a different thread size than the two placed along the outer edges of the F-1204 center section. The center two nutplates are attached with flush pop rivets while the two nutplates on the outer edges of the center section are attached with solid rivets. Next the F-1204R retainer blocks were bolted onto the F-1204CL-R forward bulkhead side assembly and the F-1204 center section. A reminder to builders, when setting the torque value of the torque wrench make sure to add the resistance of the elastic stop nut or nutplate onto the desired torque setting to prevent under torquing the hardware. As an example, AN3 bolts are to be torqued between 20 and 25 inch pounds … if the stop nut offers 5 inch pounds of drag, then add 5 inch pounds to the torque wrench setting. So to get a true 25 inch pounds of torque, the wrench would need to be set to 30 inch pounds.
Using the pneumatic squeezer to rivet a nutplate onto the F-1204 center section.
Using a torque wrench to tighten the F-1204R retainer block bolts on the F-1204CL-R forward bulkhead side assembly.
Mounting the F-1204R retainer block on the F-1204 center section with a torque wrench.

The F-1204P-L&R skin attach flanges are normally riveted onto the F-1204 center section with LP4-3 pop rivets. The clearance for the pneumatic was good, so the F-1204P skin attach flanges were riveted onto the F-1204 center channel with AN470AD4-4 solid rivets as opposed to LP4-3 pop rivets.
Using the pneumatic squeezer to rivet the F-1204P-R skin attach flange onto the F-1204 center section with AN470AD4-4 solid rivets as opposed to LP4-3 pop rivets.

Tuesday, October 22, 2013

Last Of The Fuselage Parts Priming

Early this morning the longerons were deburred, cleaned, scuffed with Scotch-Brite, and cleaned again with Acetone in preparation for priming. The baggage area aft bulkhead that was recently discovered along with a small handful of remaining miscellaneous parts were also cleaned and prepped for primer. At this point there are no more parts to prime with the exception of the hinges that will make up the seat position adjustments. They need to be match-drilled to the seats and at this point there is no rush to finish seats. When the time comes a small batch of primer can be mixed and used in the airbrush or wait until parts from the finishing kit are primed.

Even though the outside temperatures were below 50, a batch of Akzo primer was mixed and sprayed onto the remaining bulkhead, longerons and the last of the miscellaneous parts. Mike’s heater has been keeping the temperatures in the shop plenty warm for the proper curing of the Akzo primer so it will dry without issues.
The F1207B bulkhead and accompanying miscellaneous primed parts hanging to dry in the warmth created by Mike’s propane heater.
Both longerons primed and hung from bungee cords to dry in the warm shop.

Fortunately, there were not enough flammable vapors given off by the primed parts to blow the shop off the foundation from having the propane heater on. Now that the fuselage parts prep and priming/painting is complete, the long overdue assembly of the fuselage can begin in earnest … time to take all the small parts and create one big part. Perfect timing because the temperatures are dropping rapidly here and there is even a forecast for the possibility of a little snow tonight and tomorrow.

Monday, October 21, 2013

Longeron Match Drilling Completed

While at Bernie’s house we did not have the time to complete all the tweaking the longerons still require. The first thing accomplished back at the DOG Aviation production facility was to cut the longerons to the proper length. While at Bernie’s house we did not want to take the time to actually cut the longerons so a hacksaw was used to make starter groves at the proper locations for the cuts so the cuts could be finished later. After the longerons were cut to the proper length, the plans have the builder make a 4 degree inward bend for the last 6 inches of the longeron. The plans also give the builder the option to make a weight reducing wedge cut along the last 6 inches as well. I elected to make the weight saving cut so marked the longerons and ran them through the band saw.
Longeron on the left has the weight saving wedge cutout completed - the longeron on the right is marked and ready to be fed into a hungry band saw.

The optional weight saving cut was made prior to making the 4 degree bend so don’t know if it would work better doing it the other way … suspect not. The longeron was clamped in a vice and whacked with a soft faced mallet until it was beat into submission. Of course, the other face of the longeron got twisted … so it was yet another game of two steps forward, one step back as the longeron was bent on one side and straightened on the other until the 4 degree angle was set. This process takes a considerable amount of time to complete so patience is a virtue. I used a digital level to confirm the 4 degree bends.
Using the digital level to confirm the aft 6 inches of the longeron is bent inward at a 4 degree angle.

Because the weight saving angle cut confuses the eye, it does not look as thought the aft ends of the longerons are bent inward 4 degrees. However, if straight edges are placed along the longerons as a reference, the inward bend is clearly noticeable.
Straight edges placed along side the longerons so the 4 degree inward band can be easily seen.

Once the cutting, bending, flexing and beating of both longerons was complete, the last bit of work to be done to them prior to priming is match drilling. The plans call for match drilling the longerons to the F-1234-L&R canopy decks. Wanted to get this accomplished now because all the alignment marks will be lost during priming. The canopy deck is placed on the longeron but it IS NOT aligned to the edge of the longeron. The F-1234 canopy decks are to overlap the longeron by the thickness of the fuselage side skin. The fuselage side skins are .025 … a couple of strips of .025 were saved from when the spar cutouts were made from both fuselage side skins awhile back ,so they will be used to simulate the fuselage skin. The F-1234 canopy decks were clamped onto the longerons and adjusted so the canopy decks overlapped the .025 strips but no further. When happy with the fit, the match drilling began. Fortunately, there were no slipups and the JetFlex paint on the canopy decks survived the process unscathed.
Placing a .025 scrap of aluminum on the outer face of the longeron to use as a gauge for adjusting the overlap of the F-1234 canopy deck prior to match drilling.
Match drilling a longeron using the appropriate F-1234 canopy deck as a drill guide.
One longeron completed … one to go.
Both longerons match drilled to the F-1234 canopy deck.

Now that both longerons are to final shape and matched drilled, they are ready for deburring, cleaning, scuffing and primer. One good thing about the match drilling is there will now be holes available for hang the longerons during priming and while drying. A cold front that looks like it will bring winter temperatures with it is about to hit … so will have to prime tomorrow outside in the cold … but keep the shop warm so the Akzo epoxy primer cures properly.

RV-12 Longerons Successfully Bent

Because of the discovery of the bulkhead that needs to be primed, decided to round up the remaining miscellaneous parts that need primer and just polish it all off since another batch of primer will need to be mixed up. There are just a few remaining small items left to prime and the large longerons.

Figured at this point, may as well knock out the longerons and get then primed along with the bulkhead and the four other small items yet to receive primer. However, before primer, the longerons will require quite a bit of attention. They need to be cut to length, flaired, bent, formed, twisted and beat into submission when necessary.

The plans give the builder dimensions for the placement markings used for determining the locations of flared ends & twists, the template positioning for the curves and placement of bends and cuts on the aft end of the longerons. The F-1234-L&R canopy decks are used as the templates for making the curve in the longerons. Normally the longerons would be placed in a vice, tensioned and whacked with a mallet to put a small curve into the angle … move another inch and repeat.  While bending the longerons for Pete’s RV9A using this method, we discovered it places a huge twist in the angle which then requires more bending on the opposite side of the angle to straighten out the twist … which also relaxes the curve. So it is a continuous two steps forward one step backwards time consuming process.

Wanting to try another method other than beating the longerons into submission, decided to buy a pair of longeron bending dies. The dies are sold by a guy who owns a machine shop and built a RV years back. He realized there had to be a better way and designed a pair of dies that are placed into a vice and when the jaws are closed it compressed the aluminum and forces it into a controlled bend. One half of the die is convex and the other is concave. The convex die also has a slot which holds the aluminum angle and helps eliminate the vast majority of the twisting.
RV longeron bending dies … top die is convex with a slot for holding the angle which greatly minimizes the twisting ... bottom die is concave. The dies are placed in a vice sandwiching the aluminum angle and the bend forms as the vice’s jaws apply pressure.

I was not sure if my vice would be up to the task, so Saturday evening the longerons were taken to Bernie’s house and we used his much more industrial vice to do the work. The ends of the longeron’s were first opened per the plans but instead of beating the longerons, a ¾” pipe coupling was compressed in a vice which had the effect of flaring the angle of the aluminum. The pipe worked great. After the longerons were flared, the end of the longeron is twisted a few degrees with a “metric crescent wrench”.
Example of using a pipe coupler in a vice to open the bend of the aluminum angle.

Now for the fun, the longeron bending dies were lubed with grease, longeron placed in the dies and then the dies were squeezed in a vice until the metal moved … the die was then moved a couple of inches and the process repeated.
Longeron in the bending dies ready for the vice’s jaws to compress the dies to form a bit of a curve in the longeron.
Compressing the bending dies with the vice to form the curve while Bernie is holding the aft portion of the longeron.

Once the curve was formed, the appropriate F-1234 template was aligned with locating marks previously marked on the longerons and the curve checked. The longerons were fine tuned by being beat into submission with small love taps. Of course, the hand pounding and fine tuning did put some twist into the metal, so it was still necessary to go back and forth as was done for Pete’s longerons … but the twisting was truly minimal in comparison. Have to say the dies made a very nice curve and did a great job … would recommend them to other RV builders of all models.
Bernie and myself holding the F-1234 canopy deck/template and comparing the curve of the longeron to the template.

With Bernies help, the longerons came out very nice and follow the template almost perfectly … doubt the curve is off by more than a 1/32” at any one point.
The two left and right longerons placed back to back after bending - yep they sure look even.

The longerons still require some more work before primer. There is a 4 degree bend that needs to be made at a point 6 inches from the aft end of the longeron along with a weight saving tapered cut. After all the cutting and bending is finished, the F-1234-L&R canopy decks are clamped onto the longerons and holes in the F-1234-L&R canopy decks are used to match drill the longerons. So there will still be quite a bit to do before primer.