Spray booth and priming test

I did quite a bit of reading on the contentious subject of priming, and looked into some of the chemistry. Without further justification, my decision was to prime using an aerospace grade two part epoxy primer. As a result of this decision, I would need to set up some sort of spray booth. Spraying outside is not an option, weather is too variable and this is after all a sheep farm – at times it is hard to tell the difference between the hordes of enormous Calliphora stygia and low flying helicopters. Just doesn’t seem right to be prising insects off parts after they landed on wet primer and got stuck.

I have a reasonable amount of room, so I built a spray booth capable of holding enough parts to make up any of the assemblies. I built it out of structural pine, covered it in builder’s plastic, and installed a mesh table, lighting, an exhaust fan and an intake filter. I put the whole thing on 4 inch castors so I can just roll it into a corner when not in use.

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    sp1

    sp1

    Start building spray booth
  • sp2
    sp2

    sp2

    The usual helpers
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    sp3

    sp3

    Fitting spray table mesh
  • sp4
    sp4

    sp4

    Starting to cover. On wheels - spray booth on the move
  • sp5
    sp5

    sp5

    Finished, ready for work
  • sp6
    sp6

    sp6

    Air regulator and dryers for spraying
  • sp7
    sp7

    sp7

    Ready for priming process test on practise kit
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    sp8

    sp8

    Practise kit parts cleaned and etched, ready for adhesion promoter
  • sp9
    sp9

    sp9

    PPG EAP-12 adhesion promoter
  • sp10
    sp10

    sp10

    Finally ... ready to spray epoxy primer
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    sp11

    sp11

    Practise kit parts after priming

 

I decided to use the Van’s practise kit parts as a means to test the entire process. This meant the practise kit stayed in pieces while I got the booth finished and waited on some of the sundry items I needed. The process I’m using is:

  • Clean and degrease with PPG Deso-clean 110
  • Etch with a 5:1 solution of Alumiprep 33
  • Spray on an adhesion promoter, PPG EAP-12
  • Spray on PPG CA7700 epoxy primer

I’m using the EAP-12 in preference to Alodine because I have no way of dealing with toxic rinse water here, anything that wound up on the ground around the workshop would eventually wash off into the main dam, and then get pumped to all of the stock troughs that the sheep (and a lot of local wildlife) drink from. I didn’t want to be responsible for causing some sort of zombie sheep apocalypse in the area.

The practise kit trial went OK. The booth could use some back lighting which I will add one day. Cleaning and etching went off without a hitch. I didn’t mix up enough EAP-12, so the application was a bit thin for one of the skins. I decided to let this go, since it was just a practise piece. I tried a few different air pressure and spray gun settings during the primer application. As it turns out the settings I started with were perfect, and each alternative I tried degraded the result – which is OK, that’s what a trial is for. There was some paint spitting when I dropped the air pressure too low. I also got so pre-occupied evaluating various gun settings I coated the skins too heavily.

Now I get to do it all over again with the Vertical Stabilizer parts.

Assembly of VS [8.0 hours]

I decided to conveniently forget about all the farm jobs today and put in some work on the vertical stab.

I de-burred all the ribs, assembled the ribs and spars, and match drilled. Based on numerous Internet posts about nose rib skin bulge, I thought I would check the fit of the nose ribs into the VS skin as a separate operation. I started with the lowest (widest) nose rib, and sure enough, it was simply not possible to cleco the two inner most holes without causing a bulge in the skin. The general advice seemed to be that material needs to be removed from the front of the nose rib in order to allow it to fit. Some individuals have reported taking as much as 3/8 inch off the front of the ribs, but I didn’t want to jump in that deep. So I sawed around 1/8 inch off the front, cleaned it all up, and tried the fit again. This made zero difference, which makes sense since taking this material off made no difference to the shape and distance between the forward most rivet holes. Further research on the forums brought the solution to light – flute the nose of the rib. I thought about this for quite a while since it seemed like a one-way street, and decided it was either bulges, remove a lot of material from the front, or fluting, so I went ahead with the flutes and this completely solved the problem – no bulges.

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    vs10

    vs10

    1: Trimming a small amount from front of VS bottom nose rib
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    vs11

    vs11

    2: Shortened VS bottom nose rib after file and debur
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    vs12

    vs12

    3: Trimming VS nose rib doesn't solve the "bulge" problem
  • vs13
    vs13

    vs13

    4: Fluting to solve the VS nose rib fit problem
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    vs14

    vs14

    5: Nose rib fits OK now
  • vs15
    vs15

    vs15

    All nose ribs needed fluting

 

For the middle and upper ribs, I didn’t remove any material, I fluted them. There’s only really room for a single flute on the narrow top rib. I assembled the VS this way and it all went together well, with no bulges. I match drilled all the #40 holes, moved every cleco over one position, and match drilled the rest. For the nose ribs, I put a cleco in every hole, and removed them one at a time, match drilled, and replaced.

 

VS skin clecko'd ready for match drilling

VS skin cleco’d ready for match drilling

 

More drilling [4.0 hours]

Continued on today, match drilling #30 the entire VS rear spar assembly, including the rudder hinge brackets. With a clecko in every second hole, there was plenty of support there to rest the entire assembly on the cleckos.

Match drill #30 VS rear spar assembly

Match drill #30 VS rear spar assembly.

With the assembly still together I did the countersink for the #30 holes on the VS-1008 rear spar doubler.

Countersink VS-1008 rear spar doubler

Countersink VS-1008 rear spar doubler

 

Time for Step #2 [4.0 hours]

Today I match drilled the VS-1003 spar and VS-1014 spar flanges, in accordance with step #2. Tossed up whether to use the hand drill or the drill press, but the plans specifically state to keep the drill as square as possible, so I opted for the drill press. I made up a platform for the spar, using a recovered side panel from the empennage crate.

Setup for VS-1003/VS-1014 match drilling

Setup for VS-1003/VS-1014 match drilling

Setup for VS-1003/VS-1014 match drilling

Setup for VS-1003/VS-1014 match drilling

Definitely overkill, but I figure I would use the platform many more times for items that are best done with the drill press.

The setup worked just fine.

I also de-burred the VS-1008 rear spar doubler today

 

 

 

 

 

 

The first hole drilled in the project

The first hole drilled in the project

Match drilling VS-1003 to VS-1014 flanges

Match drilling VS-1003 to VS-1014 flanges.

 

First build entry [2.0 hours]

Still waiting for some tooling to arrive, and to finish various workshop items. I’ve been in no hurry to officially “start”, but for want of something else to do, today turned out to be the random date that I did the first work on actual parts of the aircraft. The place where everyone starts – cutting the VS-1014 flanges. So, I marked them out, used my awesome bandsaw to do the rough cuts, and took these down to dimension with a Vixen file. I also de-burred the flanges, as well as the VS-1003 rear spar that they fit into.

Filing the diagonal cuts on the VS-1014 flanges

Filing the diagonal cuts on the VS-1014 flanges

That’s it. Section 6 step 1 completed without incident.

Empennage arrival and inventory [5.0 hours]

The empennage kit arrived today. Well before I have enough tooling in place, and the workshop adequately organized. Inventory took 5 hours, and everything was present and accounted for. Clinging to the bottom of the Earth down here, I’m used to seeing all sorts of transport disasters. In this case, despite the best efforts of the freight companies, Van’s did such an excellent job of crating the kit arrived here unharmed.

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Workshop space

People have successfully built RV-10’s in absurdly small spaces. I’m fortunate to have an 11 x 7 metre workshop space available – all I had to do was remove the floor to ceiling junk pile it contained. As it turned out that process took months, and included extending a farm shed to provide extra space for vehicles and tractor attachments that were previously in the space that is now the RV-10 workshop.

I built a fixed, narrow workbench area in one corner, with plenty of pegboard to hang tools I don’t yet have. The old farm compressor was too small for this job, and so worn out it can be heard across most of the state while running. I decided to leave it where it belongs – in the farm shed – and install a new quiet compressor in the garage.

workshop1 workshop2

I built two full size and two half size workbenches. Not the exact dimensions as standard EAA workbenches, but a little larger just because of the common sheet size of MDF available. I also included lips around the outside for clamping, and put the two full size benches on 4 inch brake-able castors. These benches never carry heavy weights, nor are they ever heavily bashed on, and being able to wheel them around and position them according to different tasks seemed like a good idea. All benches, moveable and fixed, are the same height and can be abutted if necessary.

The drill press is overkill for the RV-10 project, but is there longer term for farm use.

I also built a large wide/deep shelf for storage of skins and assemblies, and installed some tray drawers for storage/organization of smaller parts. Of which there are a lot.

 

 

 

 

The little band saw that could

I looked at a lot of metal-cutting band saws, but the cheap ones were junk and for such occasional use the not-so-cheap ones were hard to justify. I did have my late father’s old wood working band saw in the shed, and wondered whether it might be pressed into service. I was probably the last person to use this machine, 40+ years ago. It has precious few guards over the moving parts, and NO SWITCH – just turned on and off at the power point! In this day and age it’s hard to imagine letting a young pre-teenage boy use such a dangerous piece of equipment, unsupervised and alone, in a workshop – but back then things were different.

The old rubber power cord was perished beyond belief, and basically fell off. The old electric motor looked OK though, and after testing the insulation I wired up a new power cord, stood back, and turned it on. It worked! So I measured the length required, and ordered some 14 tpi blades from www.bandsawsupplies.com.au. Once these arrived I fitted one and made the usual adjustments to make it run true. The band saw cut through some sample pieces of Aluminium like butter. The only problem is, the Aluminium chips showered down all over the old electric motor, and also onto the rubber lining on the lower wheel. I’ll make a shield to keep the chips from falling through vents on the old motor, and just have to keep brushing them out of the old rubber wheel linings.

Engine patented in 1936, which makes me comfortable given that we all happily fly around using Lycoming aircraft engines

Engine patented in 1936, which makes me comfortable given that we all happily fly around using Lycoming aircraft engines

Modest guards on the front

Modest guards on the front

No guards on the back in those days!

No guards on the back in those days!