Monday, 28 April 2014

Helpful hose fitting video

Week 143 - Fuel system cont.

Hours to date 1259.0

I had a good weekend of progress with the fuel system.

The fuel pump mounting released okay - I then cut down the threads of the composite screws so they're a bit neater.

I still need to go back and add some more flock in the holes and maybe put a layer of glass over that lot.

In the meantime I got on with fitting hoses.

All the fuel system up to the firewall (bar the high pressure feed line) is done. I'm going to use steel braided hose for the high pressure part and also for the small piece of hose that goes on the outside of the fuse before the feed line goes into the tank (as it's stiffer and less prone to wear).

As you can see from the photo below I've got a rather complicated solution to the flop tube arrangement. I have to do this as I want the maximum amount of hose length for the flop tube and cannot go right up the front of the leading edge part of the tank with a straight fitting because the front wing pin bearing will go their.

So we have to go back to go forwards - as it were.

I'm happy to report that after testing on the bench it should work fine - plenty of movement in the hose at that length - I only ended up taking 25mm from the full length of the Vans supplied hose.

The other good thing about this arrangement is it puts the flop tube further into the tank - away from the drain and overflow valves and also the capacitance probe for the fuel gauges - no bad thing.

I went ahead and drilled out the hole for the feed line into the tank. I can see why Pete doesn't think it necessary to reinforce this area - the tank is very thick at the root end. I will use epoxy (probably a runny flock) to secure these fittings when I do it finally. Pete says he uses 5 min epoxy - I've had mixed results with 5 min epoxy so prefer to use the 'good stuff' for this.

I'm also pleased to say that the other hoses all seem to fit well and have plenty of movement on the inside of the fuse. The movement is to allow for the quick disconnects to be drawn outside of the fuse when the wings are taken off (or put on).

I've got a couple of parts coming from Mark at Galaxy Microlights to finish off the Fine Filter section. And I've ordered a fuel pressure sender (Dynon type) to go on top of the Banjo bolt that exits the Fine Filter.

My plan is to get all the fuel (and oil cooler) hoses done all the way up to the firewall, this is to get as much work done related to the engine before actually ordering it. (it's bad for the engine to sit for any length of time without running as corrosion can set in internally).

I've also got to fit the fuel overflow hose and valve plus the drain valve to the fuel tanks.

The only thing I won't be able to do at the moment is fit the return line bulkhead fitting into the tank - I want to do that when I put the wings on to get it in exactly the right place.

I'll post a link to a very helpful video in another post - it's all about how to fit hoses. I found it very helpful and used all their techniques bar one - I used masking tape on the hose rather than a marker pen to make sure it did not move when fitting - the marker would not show up on black hose anyway.

The must haves are: a Dremel with a cut off wheel, Aluminium jaws (for holding the fittings without damaging them) and ali spanners (again so you don't damage your fittings - they are soft anodised ali and mark easy).

Will hopefully have one tank done by next week. After that I will add some composite screws (with P clips) for retaining the hoses.

Flop tube arrangement - piece of hose between the two red fittings at the bottom still to come.

Fuel pumps mount - after releasing - some more work to be done here.

Time to fit some hoses!

Composite Screws shortened

Ali jaws for your vice - must have for hose fittings

Ali spanners and Dremel with cut off wheel - also essential tools

Masking tape on hose to monitor movement when fitting

Port side view of hoses in place

Starboard view

Outboard view

Feed line fitting in tank

Flop tube fittings inside view of tank

Flop tube shortened and fitted

With flop tube in place - works okay

Inside view with hose in place

Wednesday, 23 April 2014

Visitor from Oz

Say Hi to Krishna from Australia - a fellow Twister builder who visited me last night.

I think he is filled with renewed motivation now to get back working on his kit.

Tuesday, 22 April 2014

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.

Flop tubes from Vans

Fuel selector - partly done - still waiting on one fitting here.

Fuel pump and fine filter layout - ignore fitting this will be replaced soon.

Holes for fuel connectors in fuse wing root.

How the quick disconnects will work

Canopy parts - yay!

How to cut hose - use masking tape and Dremel with cut off wheel

Fuel pumps and pre filters on the tray and all wrapped up in packing tape

Flock laid out ready for the tray
Tray in place

Tuesday, 8 April 2014

Week 140 - Throttle/Brake, Gear knees and Fuel setup

Hours to date: 1239.25

First up the Throttle/brake assembly - which has been rebuilt so that the levers are both on the left hand side - the throttle is much less likely to be moved by the pilots leg in this setup.

From the close ups you'll see the standoff made by my engineering friend from New Zealand. This plane is truly an international affair. German kit, Belgian engine, US instrumentation, Italian prop? and a Kiwi builder living in the UK.

I've also put a fat fibre washer in between the throttle and brake - it gives a much nicer feel to the throttle action.

I may end up putting a sheet of thick rubber (with slots for the levers) bonded over the top of the hole currently covered at the bottom by the (draft stopper) brushes. I saw this on the Twister that had the tailplane failure when it was in Pete's workshop. Seems like a good idea to stop FOD.

Onto the fix up jobs. The gear leg knees were reinforced with roving but as you can see below this left a very uneven surface. Not good as this surface will take all the weight onto it's mount and sits on only a very thin piece of rubber (1mm). So I've used the Dremel to smooth out the surface then used flock to fill in the gaps and finally wrapped the lot again in carbon. The surface is now nice and smooth and should transfer the load evenly onto the gear mounts. The extra layer of carbon will not affect the gear alignment as it is a forwards and backwards movement of the inboard end that sets that up - the dihedral of the gear will be ever so slightly affected - but we are only talking about 1 mm or less here.

The other two little jobs are the seat back extension (on the fuse) and repairing the hex for the elevator that I screwed up.

A heavy box arrived the other day and it was full of fuel parts from the UL Power agent here in the UK (Mark at Galaxy Microlights - who is a friendly and helpful chap.)

As you will see below I have the initial layout sorted out.

Next steps will be to sort out the fuel pumps mount - probably best to do this with Micro methinks. I have some doubts as to the capability of the mount - the two fuel pumps are very heavy - 1.6kg - and they will be 6 times that weight pulling down on this mount when doing aeros. I'm thinking of using 6 composite mounting bolts on the outer holes and maybe bonding it to the micro & cell underneath, I may even add some more composite mounting bolts in the centre - we'll see. I'll certainly be using 2 hose clamps for each pump to hold it in place.

The pre filters are very light - as is the fine filter.

All the fittings and hose that I ordered should arrive this week - so hopefully we'll see some real progress this weekend. 

Throttle & Brake assembly (again)

Fat Fibre washer added

Ali standoff

Brake hose routing
With brushes

Gear knees after first lot of roving - note uneven surface

After flattening off with Dremel

With new layer of carbon
Repair to elevator hex - built up the thin part first

Then wrapped the lot in carbon again

Seat back extension finished
Fuel pump and filter parts

First thoughts

2nd thought - fine filter inline now - should be less fittings & hose used this way

Thursday, 3 April 2014

Week 139 - Bits and bobs

Hours to date: 1234.0

No pics this post as I've only been doing small fix up jobs of late.

Fixing the hex that I damaged getting out of one of the elevators

I'm also tidying up the 'knees' of the undercarriage - where they were reinforced with Carbon roving - I didn't make a very neat job of these so will post some pics when they are all done and describe what I did.

After that will be the fuel system.

I've ordered a load of fittings and hose, £600 worth! £300 of that is just for the quick release fittings - 4 are needed - 1 feed line and 1 return line per tank.

Hopefully these parts will be delivered soon and I can get going.

Also Pete has finally started on my canopy parts - yay!

He says they should be ready in 2 weeks time.

I'm kind of dreading the canopy as most people struggle working with perspex.

Oh - and I LOVE working in my new workshop - it is great having all that extra space.