Bending longerons, fitting gear brackets [28.5 hours]

Sections 28 and 29 of the RV-10 build manual are quite long and involved. There’s a lot of bending and manipulation involved to assemble the fuselage to the point where it resembles a large bathtub. I’ve decided to forge ahead and assemble / match drill everything through to include the side skins, tear it all apart for one large priming session, followed by a large amount of riveting to take me through to the end of section 29. I’m doing this rather than the piecemeal steps in the build manual order because I’m using a spray gun and 2 part epoxy primer – it takes me a while to get set up to spray but once setup I can paint a very large number of parts fairly quickly and this is the way I prefer to work.

To bend the longerons, the instructions say to clamp them in a vice and hit them with a hammer. I’ve done this in the past for the empennage longerons – successfully – but some time ago I bought a longeron bending die set to use for the fuselage longerons. It’s just as easy to mess up the bends with the die set compared with a hammer, the trick is to take it slowly and never over-do a curve so that you don’t get into a situation where you are un-bending, i.e. going backwards. All four longerons turned out well and slotted into the fuselage just fine.

I also fitted the gear brackets, and match drilled the forward legs into the forward fuselage assembly. The plans call out for a 0.063″ spacer, WD-1021P, to be fitted and match drilled between the side of the brackets and the side rib. Many builders have run into trouble in this area, it is just not possible for Van’s suppliers to bend the steel brackets accurately enough. Van’s have in the past told people to just go without the spacers, but I didn’t want to do this. The gap in my case was tapered, the right side worse than the left, so I filed the WD-1021P spacers into a wedge shape in order to fit them to their respective slots. This worked out OK, and I’m not worried about punching through the Aluminium layer of the Alclad because I’m priming them.

Next step is to bed the skins, and I can’t do this until I build a fuselage stand, to get my work benches back.

  • f10a
    f10a
    Marking longeron prior to bending
  • f10b
    f10b
    Longeron prior to bending
  • f10c
    f10c
    Longeron bending die
  • f10d
    f10d
    Bend by applying pressure every 1"
  • f10e
    f10e
    Checking shape against bend template
  • f10f
    f10f
    Longerons in place
  • f10g
    f10g
    Left side longeron in place
  • f10h
    f10h
    Drilling forward gear bracket
  • f10j
    f10j
    Uneven gap between gear bracket and side rib
  • f10i
    f10i
    Tapering WD-1021P spacer
  • f10k
    f10k
    Tapered WD-1021P spacer

 

Forward fuselage progress [11.5 hours]

I’ve been thinking a lot about the firewall insulation. Best practise in the RV community seems to be the use of Fibrefrax on the outside of the firewall, held in place with stainless steel foil. To that end, after a US trip last year I brought back some 1/8″ Fibrefrax and a roll of 0.002″ stainless steel foil. A secondary but no less important issue is what to do about the floor in the area immediately behind the firewall. In the event of an engine fire, temperatures could reach 2000 degrees F in the engine bay, and cowling airflow will direct hot gases / flames out the bottom and under the front seat floor. While I’m trying to get the aircraft on the ground, the floor could literally melt out from under my feet, since the melting temperature of Alclad is 500F. It is interesting to note that the Cessna 172’s and 206’s I’ve trained in have basically nothing in terms of insulation/protection on the firewall forward floor area.

Commonly used ‘flameproof’ floor insulation materials such as Soundex are a non starter as far as I’m concerned, since they will in fact catch fire and expel all sorts of noxious fumes in the event of an engine fire. Again, best practise in the RV community seems to be external ceramic insulation. In the case of the RV-10 with a Showplanes cowl, the cooling air outlet spans the entire width of the lower forward fuselage skin (see picture). I obtained a roll of 18″ wide, 0.005″ thick Titanium and some 1/16″ Fiberfrax ceramic insulation to do this external insulation. The Titanium is secured in place with a combination of Monel pulled rivets, which will not melt at fire temperatures, and regular AN426 rivets on the outside edges, which will melt at fire temperatures. The rivets on the sides and rear will not be exposed to these extreme temperatures, so only the rivets along the firewall bottom flange would be an issue. The monel rivets will hold the Titanium in place, and I’m applying a layer of 3M fire barrier 2000 sealant to this forward edge as well, the combination of these should be adequate to keep the front edge of the insulation in place long enough to effect a forced landing. Or at least give me a fighting chance.

I sandwiched the Titanium foil between the F-1072 bottom skin and a piece of MDF, and drilled through the assembly for Monel rivet lines, match drilled AN426AD3 rivet holes, and platenut positions for the Showplanes cowl mount points. After that, I was able to de-burr and dimple the skin and the Titanium foil, which I put aside for later assembly. I primed the skin and then reverted back to the regular plan assembly steps. This is a long section of the build, and I’m currently at the point where I have mated the mid fuselage and forward fuselage assemblies. Now I have to prepare spacers to go between the two main spars and a set of bolts to hold the spars together. The skin overlaps and a few other parts are then match drilled, I pull the assemblies apart to de-burr and dimple, and will then mate them together for the final time.

The combination of the forward and mid fuselage assembly is quite long, to which gets added the empennage. I’m going to have to build a roll-around stand for the assembly so that I can get my workbenches back.

  • f9cowl
    f9cowl
    Underneath the Showplanes Cowl
  • f9a
    f9a
    Figuring out platenut positions for the Showplanes cowl AFT fairing
  • f9b
    f9b
    Match drilling through Titanium foil
  • f9c
    f9c
    Titanium foil match drilling complete
  • f9d
    f9d
    Match drilled #19 holes through Titanium foil for Showplanes Cowl mount
  • f9e
    f9e
    Dimpling Titanium foil
  • f9f
    f9f
    Match drilling #19 through Showplanes Cowl AFT centre section
  • f9g
    f9g
    Primed F-1076 centre section skin where overlap occurs
  • f9h
    f9h
    Preparing to back rivet stiffeners to F-1072 forward skin
  • f9i
    f9i
    Outside of F-1072 bottom skin, ready for back riveting, area to be insulated has been lightly primed
  • f9j
    f9j
    Back riveting assemblies to F-1072 forward fuselage bottom skin
  • f9k
    f9k
    Mated forward fuselage bottom skin assembly to firewall subassembly
  • f9l
    f9l
    Addition of forward bulkhead to forward fuselage subassembly
  • f9m
    f9m
    Forward and mid fuselage subassemblies placed together for the first time!
  • f9n
    f9n
    Forward and mid fuselage subassemblies placed together for the first time!
  • f9o
    f9o
    Forward and mid fuselage subassemblies placed together for the first time!
  • f9p
    f9p
    Forward and mid fuselage subassemblies placed together for the first time!

Control Approach Rudder Pedals [4.5 hours]

I’m held up a bit waiting for a delivery from the USA so it’s time to tidy up the workshop and do a few other work items. I spied a box on the shelf that’s been sitting there for the past 18 months, and once I remembered what it was I just had to go ahead and play with it. The box contained a Control Approach┬áRV-10 rudder kit. As far as I know this was one of the last kits Paul ever sent out and they are no longer available.

I never liked the look of the Van’s rudder pedal assembly. Hated the brake cylinders and hoses being on the front of the pedals. Without really researching it well at the time, I took a punt and ordered this kit back then because it was going out of production, and now I’ve assembled the kit I’m glad I did. The parts are high quality and the design and construction is first rate. The brake master cylinders and associated hoses are relocated under the pedals where they belong. The rudder cables stay in the tunnel and don’t have to come out the sides into the cabin.

There was some evidence this was Paul’s last kit, a few of the longer AN3 bolts were obviously “pre-owned”. I set these aside and used new ones I had on hand (because there’s no way of knowing if a bolt someone else used has been over-torqued). The assembly instructions leave a lot to be desired, but there’s only really one way the parts can all go together and it doesn’t take too much head scratching to figure the assembly out.

One of the stainless steel pins was a problem. The thread stripped, and it’s hard to know how that happened since I was using my usual miniature torque wrench to do up the AN365-1032 nut at the time. It’s a very simple piece and I have access to a facility that can turn up a replacement so I’m not too bothered about that.

  • f8a
    f8a
    Control approach rudder pedal kit
  • f8b
    f8b
    Drilling rudder pedal assembly
  • f8c
    f8c
    Rudder pedal assembly complete (almost)
  • f8d
    f8d
    Brake master cylinders not installed yet
  • f8e
    f8e
    Faulty part - thread stripped

 

Riveting mid fuselage skin, forward fuselage parts [18.5 hours]

After quite a few riveting sessions, the mid fuselage assembly is finally complete. There are more rivets than normally the case due to various doubler plates for the A/C condenser mounting points and two COM antennas. I’ve also riveted the forward fuselage ribs to the firewall, and installed platenuts on various forward fuselage parts and sub-assemblies.

I’m held up now waiting for the nose gear mount pieces of the showplanes cowl. I want to install platenuts on the forward fuselage skin to mount the aft moulding and that is best done before assembly.

  • f7a
    f7a
    Riveting forward fuselage rib subassembly
  • f7b
    f7b
    Riveting forward fuselage rib subassembly
  • f7c
    f7c
    Forward fuse main ribs riveted to firewall
  • f7d
    f7d
    Forward fuse main ribs riveted to firewall
  • f7e
    f7e
    Mid fuselage antenna doubler
  • f7f
    f7f
    Mid fuselage A/C condenser mounting doubler
  • f7g
    f7g
    COM antenna mount point, mid fuselage
  • f7h
    f7h
    Trial mount of CI-122 antenna
  • f7i
    f7i
    Mid fuselage bottom skin, riveting complete