For those who are interested in another alternative, I have just completed
replacing all my hoses aft of the firewall with stainless ribbed tubing and
JIC fittings. I have also completed an update on my parallel fuel system
which now dispenses with the mechanical pump. The reason for this was to
eliminate the hoses that cross the engine twice greatly reducing the vapour
lock risk. This allows most of the senders to be aft of the firewall which
also reduces heat transfer. To prevent total electrical power loss to the
pumps, the two pumps have a total of three busbars available for power
source and a crowbar unit prevents the regulator from bringing the whole
system down. To enable the tubing to start from the tank outlets replacement
threaded outlets were supplied by Graham Singleton.
The stainless tube has the following advantages:
1. It should never need replacing. Rubber hoses should be replaced every 5
years.
2. It is much lighter than any other hose or tube.
3. It is easily cut with a tube cutter leaving no swarf.
4. In conjunction with the JIC fittings it is designed to take up to 14bar
pressure which is way above what we need.
5. Unlike rigid steel tube it can be bent easily by hand and is impossible
to kink. This eases initial installation and enables removal of a section of
the system. It also avoids the critical length problems associated with
rigid tube.
The one disadvantage is the JIC fittings cost about 8($12) each so it pays
to design the system with the minimum number of joints.
My parallel system has now been greatly simplified having gone all electric
and with the reduced amount of hoses/tubing I have saved about 4lb in weight
some of which is due to changing to the stainless tube. I estimate that my
system went from being about 3lb heavier than the standard system to 1lb
lighter. The only remaining hose is the short length from the firewall to
the carburettors as this needs to be a little more flexible.
I am just about to test fly the new set-up but don't anticipate any
problems. If there are any I will report back.
Nigel Charles
|