My source of cabin heat is via flexible tubes (about 2" diameter) from a box
around the exhaust. It produces lots of hot air very quickly, and was much
appreciated when flying last Saturday when it was very cold outside (-1deg C
is very cold for the Isle of Wight).
It is controlled by a butterfly valve operated by a choke type cable. Both
this cable and the choke cable terminate in pull-on type knobs on a separate
plate attached to the instrument panel, just on top of the tunnel (ie below
radio stack). This means they can be left in place if/when the instrument
panel is removed. It sounds like your carb heat system will operate in a
very similar way to what I was thinking about.
Incidentally, I also had a temperature prope stuck to the throat of one of
the carbs on the engine side, and on Saturday it varied between 25 and
40degC once the ngine was warmed up, I guess through heat from the exhaust
nearby. Maybe this is why ice seems to be quite rare on the Mk1 aircraft?
Any more thoughts?
David
GBWJH
-----Original Message-----
From: owner-europa@aztec.houxou.com
Subject: Re: Lower cost carb heat solution?
writes:
<< We have installed a large NACA scoop in the top of the cowling, operated
by
a choke cable. This enables us to introduce cold air (or at least luke
warm)
into the area the carb intakes are located. We figured this was a much
cheaper alternative to a plenum chamber and also keeps the regulator box
and
electrics cool at the same time.
>>
It is possible and inexpensive to build a plenum chamber from fiberglass. I
built one to accept the air from the Europa NACA inlet added on the top of
the Classic cowl. Two stubs of 2" dia aluminum tube were glassed into the
plenum sides to allow connecting to the carbs via SKEET tube.
A third stub was added to the bottom of the plenum to eventually allow carb
heat using air from under the cowl or connecting to the muff if needed.
Fittings were placed inside the plenum to allow installing a plate fitted
with a butterfly valve for control of carb heat -- the carb heat option
hasn't been installed or tried yet, however.
A small pocket inside the plenum connects to the carb float bowl tubes to
ensure the pressure matches the carb intake pressure as specified by Rotax;
a
drain tube connects this pocket to the slipstream so should fuel come out
the
float bowl tubes it is handled properly. Brass 1/8 tubing stubs were
glassed
into the plenum to connect the float bowls to the pocket.
Building the plenum wasn't too difficult but there were a lot of steps
needed
to handle all the little details. Probably 8-10 hours scattered over 2
weeks.
In its non-carb heat mode the plenum seems to work fine. The carb heat
option should get added and tested this spring if the snow ever melts and
flying weather returns.
One point I haven't seen mentioned is the mounting arrangement for auxiliary
controls like carb heat and cabin air. To allow easy removal of the
instrument panel I added a "sub-panel" which is simply an "L" shaped
bracket
about 10 inches long made from fiberglass with a core of 1/8" ply. This
sub-panel is secured to the bottom of the panel in the pilot's footwell so
it
is a bit forward of the panel face using Southco fasteners. This simplifies
instrument panel removal by allowing all the controls actuated by cables to
be disconnected via two 1/4 turn fasteners; the sub-panel just dangles in
the
footwell when the instrument panel isn't in place.
John N44EU
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