Due to other commitments, I’ve had to take a few months off from building, from April through June, but as of July I’m back at it again. Apart from doing the MPC course there was one notable event during this time, with the arrival of the finish kit, propeller and spinner from Van’s, the cowling from Showplanes, and the engine from Barrett Precision Engines. Finish kit inventory didn’t take long. Now I’ve really got to get on with it…
In order to maintain an experimental aircraft, a builder has to complete the SAAA’s Maintenance Procedures Course. I attended the MPC course, held in Gawler SA, on May 20/21 and subsequently completed the take-home exam in June. If I pass the exam (80% required), I will get issued with a certificate, which gives me authority under CASA Instrument 15/16 to maintain this aircraft and issue new maintenance releases. The course was well run and it was good to get away and hang out with other people building their own aircraft.
In Australia, you need at least 3 SAAA Technical Counselor (TC) visits during construction in order to check off a box with the insurance company. In my case I have to fly a TC down from the mainland, so we did a combined visit between myself and an RV-9A builder in my local area. We all had a good day going over the two projects, it was good to spend some workshop time just chatting about the build(s). My TC is a wealth of information and we were able to spend some time at the end of the day going over the paperwork requirements for having a C of A issued in Australia.
Step installation was straightforward. I started by thinking about whether I needed a drill guide (yes) and how to make one, then realized the easiest way by far would be to 3D print it. The design took 20 minutes and one print iteration. I made up guides for #30 and #12 drills. I also made up a 1/4″ guide but didn’t use it, when I decided to use the AN-3 bolt per the plans rather than the larger AN-4 bolt. The drill guides worked a treat.
Step “wobbling” has been a common problem in RV-10’s. To combat this I installed a doubler plate to provide extra support for the step support block, and I used TCW Tech’s step bushings as well as carefully reaming the final hole in the step and support.
I installed the front floor pans and gear mounts, and have now finally completed the infamous and tediously long Section 29 of the RV-10 manual. It was a relief to have both gear mounts bolt in without any drama, there have been some horror stories about this step in the plans. The tapered shims I made up for the gear mounts worked a treat and I all bolts were snug in their holes with no need to ream anything.
The empennage has been shoved in a back corner for the past year. I wanted to work out a few things prior to attaching the tailcone to the fuselage, so I swapped the empennage and spray booth around. There isn’t much priming left to do, so the spray booth (which is on wheels) can stay in the corner for the time being, before I retire it completely. This move has opened up the workshop a bit.
Over the past few weeks, with some periods of non-work, I’ve de-burred, dimpled, primed and riveted on the fuselage side skins. With the exception of a few rivets I need to make up a special bucking bar for, the fuselage side skin riveting is now complete. Almost all of the riveting was a two-person operation, and “Rosie” did her usual terrific job on the rivet gun. I got well and truly tired of lying inside the fuselage twisting into all sorts of odd shapes in order to buck rivets.
I almost made a big mistake. I was all set to start riveting the right rear fuse skin, when at the last minute I noticed some holes that were not dimpled. This after having checked all the dimpling on at least three separate occasions before priming. I don’t know how I missed them, and I was lucky to notice the problem because there is no way I could have dimpled them in-place cleanly. It was a simple matter to take the skin off, dimple the offending holes, and cleco it back on.
I used a new, full sized, spray gun to prime the skins, which made me wonder why I didn’t get one sooner. Hard to believe I primed the wing skins with a mini-gun.
Side note – my son made me a replacement stainless steel shaft for the rudder pedals, after we found one of the four supplied with the kit was faulty. The new shaft fitted perfectly, so now I have rudder pedals ready to install.
Under the front seats, there are four “systems brackets”, F-1084A/B, which have slots for a fuel line, brake line, and electrical wiring. In my case, there are two fuel lines, so one issue is how to deal with the return line. Another issue is the fact that s/s braided teflon lines are different in diameter than the Aluminium tubing lines that the system brackets were designed for. There is apparently enough scope to squash them in with a sliced apart grommet.
None of this sat well with me, and it was a simple matter to design a replacement upper bracket section and 3D print it in Nylon. There are two right-hand and two left-hand brackets, which have snap-in rings for two fuel lines, one brake line, and electrical wiring. Each ring has a slot for anchoring a cable tie, or waxed string tie, if needed. Each part takes about two hours to print, and bolts straight onto the standard lower systems bracket F-1084A. If in the future I need to make a change, I can simply print up new brackets and bolt them in place.
The brackets weigh 7 grams each. This replaces the metal upper section (F-1084B) and three snap bushings, which weigh a total of 9 grams, so there is no weight penalty in this change.
Although I’ve in general followed the Van’s plans, like the wings I’ve tended to do things less incrementally. In the case of the fuselage sections 28, 29 and 31, this has resulted in a large tear down, de-burring. countersinking and dimpling activity which has occupied the last few weeks. The list of jobs to do seemed endless at times, but I finally got through it. Not a lot of pictures across this time, my bad. There was a very large pile of parts to be primed at the end of this exercise. I primed everything except the five skins (aft/forward fuse, upper forward fuse) in one marathon priming session. I then went ahead with riveting those parts I could in the fuselage structure, as well as riveting sub-assemblies together. This reduced the huge pile of parts to a manageable size.
Next job is to prime the five skins, and rivet these to the fuselage.
I decided to go ahead and assemble the upper forward fuselage, since I had enough cleco’s, I needed a larger priming batch, and it gets a bunch of drilling / countersinking out of the way. It turns out there is a problem with two of the ribs in this assembly, as noted in this VAF posting, and I have the same problem. Either the holes in the front of the F-1045 ribs are incorrectly punched, or the corresponding holes in the firewall are wrong. During assembly, the ribs are first riveted to the top skin. If this is done, then the holes in the front flange will not line up with the firewall.
If the front flange holes are cleco’d to the firewall, there is a 1/8″ gap between the top flange and the top edge of the firewall. I can’t adjust the firewall flange – then the cowl would not fit. I tried cleco’ing down the top skin, and it sortof goes down OK, but the forward most cleco doesn’t actually close the gap between the flange and the top skin. The rest of the skin is “pulled down” to the flange, resulting in the skin curving inward. The front flange holes can’t be re-drilled, the correct position would overlap (just) with the existing holes.
The fix recommended by Van’s is to put a new flange on the front of the F-1045 left and right ribs. I bent up some 0.032″ Alclad to use as replacement front flanges. The pictures show the modification to the F-1045L (left side) rib. I removed the rib and made up a simple frame on the bench that the rib fitted into snugly. This allows installing and match drilling the new flange in the exact same forward position on the rib. I carefully cut the old front flange off, de-burred the resulting edge, and using the bench frame match drilled the new flange into place, finally trimming the bottom of the flange to match the front of the rib.
The rib with replacement flange can then be cleco’d back in place, with a reference line drawn on the flange so it can be sighted through the firewall holes and lined up properly. The front flange is a bit tight because the holes in the firewall are already dimpled. There are seven holes that now have to be carefully match drilled. The rib was removed again, all holes were de-burred, and the front flange holes were dimpled.
Finally, the rib was re-installed, and with the front flange holes now in the right place, the top skin sits flat on the top flange of the rib, and a straight edge held on the skin shows no gap.
With the two F-1045 ribs fixed up, the entire upper forward fuselage assembly can now be match drilled.
The next step in section 29 of the build manual was to bend the four side skins, hit them with a mallet, twist several other structures, and fit everything together onto the fuselage. Sounds simple enough … not.
To bend the skins I made up a clamping block per the plans, finding out in the process that the blade on my ancient radial arm saw was blunt – hence all the burn marks in the pictures. It turns out you really need to apply a lot of grunt to the skins in order to produce the required conical bends. Once I stopped being timid things went better, and the aft skins went on really well. The aft skin match drilling didn’t take long either.
To bend the front skins, I bought a new saw blade and modified the clamping block in accordance with the plans. The front skins seemed a bit more difficult than the aft skins, and I wound up finishing the bends with larger pieces of clamping Aluminium than the plans called for. Both of the front skins went on well. There’s now a fairly long list of match drilling to do associated with the front skins and firewall, before I tear it all apart for de-burring, dimpling and priming.