Well this fuel system seems to be taking longer than I thought. I don't mind spending lots of time on it though as it has to be right.
I bought some fuel flow transducers (£170 each!) as I really do want to know the fuel flow rate. Two are required as the UL power is fuel injected so has a feed line and a return line. The system pumps through a lot more fuel than is actually used by the engine (up to 100 litres an hour) so the Dynon uses the data from both transducers to determine actual fuel usage.
I've already fitted the return line one as you'll see below.
The feed one is not fitted yet as I'm still waiting on my steel braided hose to arrive.
Before I fit the adapters to the transducers finally I will apply some thread sealant. I've just ordered this so will get that done next weekend.
Below you will see my solution for guiding the hoses close to their exit point in the fuselage to wing root.
The flared tube is made of anodised aluminium and weights nothing - also it is the perfect surface for the nylon hose to smoothly run through with no wear (not that the hose will move much in there once the wings are on).
The flared tube is then held in place by a P-clip (which is attached to the spar tunnel via a composite screw - again this part is still to arrive).
The flared tube part in case you're wondering is actually called - wait for it - a Flesh Tunnel. What some people think is a good idea is putting these things in their ear lobes! Don't think I'll be doing that any time soon.
Little did the jewellery people selling me these tubes know that they would end up in an aircraft...
As you'll see below I tried to do both tubes/hoses with one composite screw - but this was too much of a compromise for both hoses need to be in just the right place - so I'll use two composite screws here.
I've applied some 'Cool-it' tape to the cell and fuse where the oil cooler will sit. I don't want the heat from that coming into the cockpit too much.
The new 'Cool-it' tubes arrived too so I was able to fit those to the oil cooler hoses and figure out where everything is going to go. After a bit of research it looks like I will be okay to get the fittings for these through the firewall after all, but I won't do any of this until the engine and other components on the firewall are in place.
Onto a real fiddle of a job. Bonding in the fuel overflow/vent line. Access is quite limited through the fuel tank access hole plus the flop tube is now in there and gets in the way a bit. Anyway I got the area roughed up and bonded it in with flock and one layer of glass. I built a special block of wood to hold the hose in place while it sets and wrapped the flop tube in a plastic bag so it didn't get any flock on it.
I'm going to bond in the other end - up by the fuel filler hole - next.
Finally, I'm now reading up on how to install the fuel probes that will go in each tank. I previously bought some pipe bending tools so that will come in handy - you only get one go at bending this tube so lots of thought has to be done beforehand.
More on that next week...
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| 'Red cubes' fuel flow transducers |
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| With adapters and fittings on. |
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| Position of feed line transducer |
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| 'Flesh Tunnel' flared tube for guiding the hoses. |
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| Return line transducer in place. |
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| Front view - composite screws to mount the transducers still to come. |
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| Hose guides - first attempt. Not successful using only one composite screw |
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| Hose guide on other side. Getting position sorted. |
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| 'Cool-it' tape applied to oil cooler area |
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| Oil Cooler with 'Cool-it' tube on the hoses. |
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| Roughing up the area for the vent line bonding |
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| Wood block I made for holding down the vent line while it bonds |
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| Wood block doing it's job. 12" Spanner is for weighting it down while it sets |
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| Fuel probe and bending tool. |
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