Practise kits

The primer on the practise kit parts dried to a nice tough finish. Flexing the skins had no side effects, to that end rolling the leading edge of the practise kit was no problem for the primer. It was also quite resistant to scratching.

With the primer test now out of the way, I assembled the practise kit. I accidentally used -4 rather than -3.5 rivets in two positions on the spar flanges, and had to drill one out. The last rivet closest to the trailing edge on each side was a pain to buck. Otherwise, the practise kit went together easily.

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    pk1

    pk1

    Practise kits
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    pk2

    pk2

    Practise kits

After finishing the rolled edge closeout, I wiped the completed kit off with some acetone, and then dropped it by accident, denting one end of the rolled leading edge. Moral of the story: an assembly is not finished until it is wrapped up and protected from accidental damage.

Finally, after many months, the workshop is now ready, the practise kits are done, and I can get back to finishing the vertical stab and moving on with the rest of the empennage.

 

 

 

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

    Start building spray booth
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    sp2

    The usual helpers
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    sp3

    sp3

    Fitting spray table mesh
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    sp4

    sp4

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

    sp5

    Finished, ready for work
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    sp6

    sp6

    Air regulator and dryers for spraying
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    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
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    sp9

    sp9

    PPG EAP-12 adhesion promoter
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    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.

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!