Building came to a halt through most of May while I travelled overseas. This wasn’t all downside, since the trip was to the USA. Needless to say, I came back with a couple of suitcases bursting at the seams with aircraft parts!
Looking around the workshop while still jet-lagged, I decided to go ahead and tear down the left flap assembly, because it was in the way. I want to do a bit of priming around a few areas of the fuel tanks, and adding all the parts from one flap to the tank bits makes up a reasonable amount of material for a priming job. There’s actually a lot of work in disassembling and de-burring a flap, because there are a lot of small parts. The hours added up on this job and I was glad to not be doing both flaps at the one time.
Since I had great success with the trailing edge method I used for the empennage control surfaces, I’m going to use the same technique for the flaps and ailerons. I bought a piece of angle aluminium, 50mm x 50mm x 6mm thick, 3 metres in length, and match drilled the trailing edge wedges in place, right through into this section of aluminium angle. This provides a straight edge to cleco the flap to during assembly, and I’ll enlarge the holes in sequence and use a pneumatic squeezer to set the rivets, as described previously for the rudder.
Dimpling the skins was easy, as was countersinking the trailing edge wedges using the jig I previously built for the rudder and elevator trailing edge parts. After all this work I no longer had a flap lying on the floor, but instead had a spray booth full of parts for the left flap. I’ve got a few things left to do with the left fuel tank and left outer leading edge auxiliary tank, then I’ll get set up to prime the whole lot.
The fuel tanks, mains and outboard leading edge aux tanks – which I outsourced – have needed a fair bit of work. Both aux tanks had leaks, which was disappointing. To help fix the leaks, I bought a cheap hand cranked vacuum pump on E-Bay. Having marked the leak points with the tank under pressure (using soapy water), I cleaned and prepared each leak point for pro-seal. I then had an assistant crank on the vacuum pump, while I applied pro-seal over the leaks. The vacuum pulled the pro-seal into the voids really well. After curing, I once again pressure tested the tanks, using a water manometer to set up around 1 psi of pressure. The water level went up and down a few inches, with changes in temperature and barometric pressure, but across a number of days it was evident that there were no more leaks.
I made up fuel lines for the aux to main tank connections, and vent lines for the aux tanks. The main tanks are vented through the aux tanks. The “usual” vent fitting is present in the mains, in case I ever have a problem with an aux tank and want to revert the plumbing back to normal. This fitting will simply be plugged, and in normal operations the main tanks vent to the auxiliaries. I have provision for transfer pumps, which are only there as a backup in case an air leak (e.g. a leaking fuel cap) on the main tanks prevents the normal syphoning of fuel from the aux tanks into the mains. There is a float type fuel level sensor in each tank.
I tested the level senders in each tank, measuring the resistance of the sender with the tank normal (empty) and inverted (simulating full). All senders are working fine, which is just as well since they are pro-sealed in place.
Each outboard aux tank holds approximately 65 litres, so full fuel for the aircraft is around 357 litres providing a no-reserve endurance running LOP of around 9 hours. Most RV-10’s in Australia have extra fuel tanks, not in order to stay aloft for such long durations, but because fuel can be a problem across large distances in the outback. Most of the time I don’t expect to use the auxiliary tanks, but on occasion they’ll be invaluable.
I still have a fair bit of cleanup to do (clearing away pro-seal spills and touching up some riveting) and some priming, before mounting all of the tank assemblies onto the wing spars. That won’t happen until later on in the month because I have a few weeks of build hiatus coming up.