Tuesday, October 30, 2012

RV-12’s Rear Wing Spars Completed

Today work continued on the RV-12’s rear spars after taking a three day hiatus to fully recuperate from the marathon work sessions of last week along with preparing for possible storm related power outages. Fortunately, the worst of storm Sandy’s havoc in our area passed to the north of us, so there were no power interruptions or damage here at DOG Aviation ... just a few days of seemingly endless rain and cold stiff winds thus far, with a couple of more days of rain in the forecast.

There are a few components that need to be attached to the left and right W-1207A rear spars before the spars are ready to become part of the wing skeleton. Work began with riveting the previously assembled left & right W-1212 hinge assemblies onto the W-1207B doubler plates. There are two rows of holes on the hinge assemblies and only the inboard row of holes are riveted at this time … the outboard row of holes will be riveted later when a rib is attached onto the rear spar assembly. There are also two other rows of holes on the spar/doubler assembly which need to be left open as well for ribs which will be attached later during assembly of the wing 's skeleton.
Attaching blue tape to identify the three rows of holes on each W-1207A rear spar assembly that will be riveted later.
                                              W-1212 hinge assemblies and W-1207B doubler plates clecoed
                                              onto the left & right W-1207A rear spars and ready for riveting.

The plans call for riveting the inboard row of rivets on the hinge bracket using AN470AD4-6 solid rivets but call for using LP4-3 pop rivets for all the doubler to rear spar rivets. All those rivets were easy to assess with the pneumatic squeezer so I elected to use AN470AD4-6 rivets on the entire assembly … stronger, lighter.
Using a pneumatic squeezer to set the last rivet attaching the doubler/hinge assembly onto the right W-1207A rear spar.
                                   Front and back views of the RV-12’s W-1207A rear wing spars with the hinge
                                   assemblies and doubler plates riveted in place with AN470AD4-6 rivets.

The finishing touches to both rear wing spars come in the form of riveting the W-1207C tip attach angles onto the outboard end of both spars. Once again the plans called for using LP4-3 pop rivets to rivet the W-1207C tip attach angles onto the rear spars … but there was good access for a pneumatic squeezer, so AN470AD4-4 solid rivets were used in place of the LP4-3 pop rivets.
                             The W-1207C left tip attach angle clecoed onto the left rear spar and ready for riveting.
                                    Riveting the left W-1207C tip attach angle onto the left W-1207A rear spar.
                   Front and back views of the outboard end of both completed W-1207A rear spar assemblies.

The W-1207A spar assemblies are now both completed and ready to become part of the RV-12’s wing skeleton when the wing assembly begins in the near future.

Friday, October 26, 2012

Airbrushing - Priming Finished Before The Storm

About four ounces of Akzo primer was left over from yesterday’s marathon priming session and was placed in the freezer to slow down the curing process. There was just not enough time left yesterday to finish up the priming of all the miscellaneous wing components so finished that up early today.

Used the Harbor Freight airbrush that gave me some trouble the first time I used it, but happy to report this time it worked great throughout almost three hours of priming. There were still plenty of small parts that needed priming … all twenty four ribs for the flaperons, the rib clips that were factory installed onto the wing main spar and a hand full of miscellaneous small parts. The airbrush did a great job of priming all the small parts … took a little time because of the small spray pattern but have to say, overall it worked great! As a result, with the exception of the flaperon spars and the wing skins, all the parts for both wings are primed and ready for assembly of the wing skeleton. The good news is everything was primed and dried before the temperatures began plummeting.

                                 Primed RV-12 wing parts everywhere at DOG Aviation … ready for assembly.

Advancing Artic Chill Spawns Sense Of Urgency At DOG Aviation

The first advancing arctic cold front of the season is bearing down on northeast Ohio as I type which means cold weather … not good for epoxy primer. The advancing cold front created a sense of urgency at DOG Aviation because the epoxy primer being used requires minimum temperatures of 59 degrees to cure properly and the forecasted highs for the next seven days are in the 40’s with rain every day. This created an all hands on deck call for action to have all wing ribs dimpled prepped and primed before the first throws of winter sets in.

                     All hands on deck at DOG Aviation ready for the necessary long work hours to beat the storm.

The whirlwind of activity and long hours began with the continuation of cutting off flanges from wing ribs. This time it was the W-1210 ribs under the saw having the forward flanges removed from all thirteen of the W-1210-R ribs and a six of the W-1210-L ribs.
                                  Using the band saw to cut off the forward flange of one of the W-1210 wing ribs.

Once the cuts were made and smoothed using the Scotch-brite wheel, it was time to begin a very long dimpling session. Dimpling all of the RV-12’s fifty four wing ribs is a time consuming chore which resulted in almost 2,500 dimples being made in the ribs – thank goodness for pneumatic squeezers!

                   Using the pneumatic squeezer clamped to the workbench to dimple one of the RV-12’s wing ribs.
                                           All 54 of the RV-12’s wing ribs dimpled and ready for primer prep.

Once dimpling of the wing ribs was completed, I turned my attention to the flaperon components. There are twenty four flaperon ribs which needed deburred, plus a few miscellaneous ribs for the leading edge and counter balance assembly. There were also a few miscellaneous brackets and parts that would require primer, so those parts were deburred as well.
                                             Deburring one of the flaperon ribs with the 1” Scotch-brite wheel.

Knowing Thursday was my last full day of 80 degree weather, I found myself confronted with two days of work ... but only one day to do it. Quite a dilemma. Typically, prior to painting I would wash down the parts with either denatured alcohol or acetone to remove oils then scrub with a Scotch-brite pad, followed by wiping the part again with acetone until the rag or towel looks clean then moving on to the next part. There was just not enough time to do all this … I needed to streamline the scrubbing of parts prior to primer.

A quick water test revealed some interesting results. I washed down a rib with solvents (tried both acetone and denatured alcohol) and ran water over it. The water beaded up … not good. Tried the above with the addition of rubbing the part with a Scotch-brite pad .. result, the water still beaded up just not quite as much.

Better living through chemistry! I decided to try using some Alumiprep 33 to see if I could get a break free surface on the ribs without scrubbing with a Scotch-brite pad. I had purchased the Alumiprep 33 (basically a phosphoric acid solution with cleaners) a while back to see if it would help streamline the Sanchem process, but never took the time to test it. Unfortunately, I knew there was just not enough time to Sanchem the parts so that was out of the question … however, thought perhaps the Alumiprep 33 cleaning agent may be useful. YOU BET IT IS!!! Mixed a 1 part Alumiprep to 4 parts of distilled water to make up a solution for testing. Cleaned a rib with Acetone as usual then dropped it into the Alumiprep 33 and watched it bubble and fizz for a minute or so then rinsed it using two water baths. Guess what… the water sheeted off the entire rib!!! Fast and easy, just what I was looking for!
                                  Alumiprep 33 concentrate does a great job of prepping aluminum for priming.

So yesterday morning/early afternoon was spent prepping and washing ribs in Alumiprep 33 and letting them air dry in the 80 degree air followed by primer spraying in the late afternoon/evening. The only places that truly really need primer is where the skins will lay on the rib flanges and where the ribs attach to the spar … the rest is icing on the cake. So to insure as good as possible primer adhesion in those areas, a Scotch-brite pad was used to lightly scuff those areas prior to Acetone cleaning and the Alumiprep dip. I erected a couple drying racks using  a saw horse and broom sticks to hang the ribs on to dry. I would Acetone and Scotch-brite a small batch of 6 to 8 ribs, run them through the Alumiprep 33 acid wash two at a time for a minute or so, place them into a water rinse … plop another two into the Alumiprep, move the rinsed ribs into the second water rinse tub, hang to dry. While those ribs were hanging out drying, I would Scotch-brite and acetone another batch of six or eight ribs and repeat the process. All and all it went far faster than the way I was doing it before. Although, had it not been for a nice breeze and 80 degree temperatures, the drying process may have taken far longer.

Sadly, I did not take the time to photo any of this because it was a full press boogie and I was a man on a mission who lost all sense of time ... and took no breaks until very late afternoon. But at least all the wing ribs, rear spars and miscellaneous parts were painted. There was a little primer left over and some small parts left to prime so I placed the Akzo primer in the freezer for use Friday morning before the cold front hits.

Tuesday, October 23, 2012

Fluting of RV-12 Wing Ribs Completed

Fluting continued today on the remaining twenty eight W-1208 ribs ... fourteen left and fourteen right. Compared to the W-1210 ribs, they were a little trickier to flute because of the tighter curve at the forward end of the rib and the J stiffener cutout. I continued using Allan Gilmore’s method of fluting which quickly got the ribs in the ballpark. Discovered that to really get the ribs totally flat, it required a little extra work by placing shallow flutes between all the flanges towards the forward end of the rib where the curve is more pronounced.
      Example of a W-1208-R rib prior to fluting … note the bow in the rib allows the pen to be slid under the rib.

After all the ribs for both wings are fluted, the plans call for removing the rear flange on all of the W-1208-L ribs, except one, and about half of the W-1208-R ribs. In addition, the plans call for removing the first upper and lower flange nearest the forward edge from some of the W-1208 L&R ribs.
                                       Using the band saw to trim off the aft flange of one of the W-1208-L ribs.
                        W-1208 rib aft flange on the left is uncut … aft flange of the rib on the right is removed.

I decided the easiest way to remove upper and lower flanges as called for in the plans was to just use a pair of pliers to flatten out the flange, followed by using a soft hammer to totally flatten the flange and then removing the flattened flanges with metal snips. After the flanges were removed, a Scotch-brite wheel was used to smooth the edges.
                         Flattened upper and lower forward flanges on one of the F-1208 ribs … ready for removal.
                          Cutting off the flattened upper and lower forward flanges from one of the F-1208 ribs.
W-1208 rib uncut upper and lower forward flanges on the left … removed upper and lower flanges forward flanges on the right.

Sunday, October 21, 2012

Wing Ribs Deburred – On To Fluting

Three 1”Scotch-brite wheels later and after spending far more time deburring than it would seem it should take to accomplish the task, all the wing ribs are finally deburred. Admittedly, I probably spent far more time than necessary … after all, when you really get down to it, the only places on the ribs that really need to be perfectly smooth are the edges where the skins touch the ribs and where the ribs attach to the spars. Hands will not be going into the lightening holes to rivet as is necessary in with other RV models, so they don’t really need to be perfectly smooth either. All that said, I just couldn’t make myself ignore a rough surface so deburring the ribs turned into a time sucking abyss while I was in overkill mode.

The last batch of ribs deburred were W-1210 L&R. At first glance, they appeared much smoother than the W-1208 L&R ribs that had the numerous jagged edges mentioned in a previous post … so I was hopeful of finishing them quickly. However that was not to be because they had their own unique problem. Although they did not have nearly as many jagged edges as the W-1208 L&R ribs, there were sharp raised edges where the metal was sheared, particularly where there were tabs on the ribs. As such, they required a lot of hand filing with the diamond needle files to remove all the raised edges.

Because the W-1210 L&R ribs were the last ribs to be deburred, the fluting process began with them. Interestingly, they are not nearly as warped as the W-1208 ribs which is making the fluting process go quickly … after spending a minute or two squaring all the flanges on each rib, the fluting is taking around 10 minutes per rib so there will be a few more hours of fluting left after today.
                                                              The typical bow of a W-1210 rib prior to fluting.

I’m fluting using a method I saw in a YouTube video made by Allan Gilmore and it is working rather well thus far. Basically, the rib is marked at 2” intervals which equates to every other rivet hole. A mark is made on the bench 2” from the edge.
                               One of the RV-12's W-1210 ribs marked every 2” for fluting. Note the blue tape
                               on the bench with the line on it … the line is 2” from the edge of the bench.

Allan Gilmore’s fluting process begins with placing the rib’s first 2” spacing mark on top of the 2” mark on the bench. The rib is pressed down flat to the bench between the edge of the work bench and the 2” mark which means it is being pressed flat BEHIND the 2” mark on the rib. The rib is then squeezed with the fluting pliers at the location where the mark is until the edge of the rib begins lifting off the bench. Relaxing the pressure on the fluting pliers should result in the rib’s edge laying flat on the bench. If the edge remains raised off the bench, use a pair of flat pliers to flatten the flute a little until the edge lays flat on the bench again. The flute is close to perfect when the slightest pressure applied to the fluting pliers begins to lift the rib’s edge off the bench and when the pressure is relaxed, the rib lies flat again …. once that is accomplished, slide the next 2” mark on the rib over the mark on the tape and press down on the rib BEHIND the 2” mark and repeat the process. Once all locations with marks on the ribs have been fluted, the rib should be flat on that side with all the flange holes in alignment. Repeat the process for the other side.
                         Fluting the rib at the first 2” mark on the rib while watching the end of the rib begin too rise.

After both sides were fluted, some ribs have required a slight tweaking. On some I made shallow flutes between the marks to bring things into better alignment.
                                               The edge of a W-1210 rib after fluting … almost perfectly flat.

It will be interesting to see how well this fluting method will work on the W-1208 ribs because they have quite a bit more curve in them because of their shape. Guess I’ll find out tomorrow.