Twisted: Week 142 - Fuel system

Hours to date: 1251.25

I felt like I made some good progress over Easter. (despite my 'disabilities' of a broken rib and sprained wrists - from a bicycle accident the week before).

As you can see below the flop tubes have arrived from Vans in the USA. They are half the price of the ones on Aircraft Spruce and seem to be less bulky as well.

I think I've figured out a solution for how to install these - but I'm still waiting on some fittings to arrive before I can get going on this job.

Plenty to do in the meantime. I've committed myself to the position of the fuel pumps (and pre-filters - all mounted on one tray). As you'll see below I wrapped the lot in packing tape (as a release) and used 8x 5mm composite screws to secure it. As I stated before I was worried about the weight of the pumps on this tray while doing aeros - it should be okay now as I've added 2 of the screws to the centre of the tray where the pumps are.

I'll finish this off later with a layer of glass over the flock. I couldn't do this at the same time as I felt it more important to get the screws all at the correct depth and angle so the tray can be removed afterwards. I learnt my lesson the hard way from the battery box cover. The screws must be level and to the right depth - I did this as a dry run first with the screws in place and tightened down the nuts until they were all in the right place. Hopefully it works!

My solution for the quick fuel disconnects is shown below. The return line goes straight onto it's fitting on the tank - a standard bulkhead fitting. The feed line has a 90 degree fitting and then goes to the front end of the tank (so that the flop tube ends up with the brass end at the spar end of the tank - as per Vans setup).

I only need about 60mm of movement from the hoses for this to work and I've tested this and it will work out fine - just by building a curve into the fuel lines on the inside of the fuse - that will become clear later on when I install the hoses.

It should be known that I have not followed the factory instructions here with the tank position in the wing - on Pete's advice I put them slightly further in - to allow for these fittings. Mine are 55mm in and just as well too as my connection at the front for the feed line will stick out by 50mm.

As you can see I am using a nylon covered hose (which is steel braided underneath the nylon) this is a much more flexible hose than the traditional outer braided type. Cutting is done with a Dremel tool with a cutting wheel. Use masking tape on the hose and mark your line - then don't force it - let the wheel do the work and the weight of the Dremel slowly cut through. The heat of the cutting wheel slightly melts the nylon and makes for a neat cut.

On Saturday I went to visit Pete and finally (!) picked up the parts needed for the canopy release. Only 7 months of waiting for that!

Pete talked me through the job and it doesn't seem that bad after all. I took copious notes and will share all when I do this job - this will be next up after I've finished the fuel system.