| CHAPTER 21 - Strakes
(Fuel Tanks and "Baggage" Compartment) |
| OK, so you're not
comfortable with looking over your shoulder to see if you can tell how
much fuel you have. Well neither was I. So I decided to add capacitant
fuel probes. These are similar to what you have in your automobile. These
little units measure the level of fuel by some mysterious electrical thing
- hey I'm a computer system architect - not an electrical engineer!
When you go this route you're not supported by the
plans and it's pretty much up to you to figure out where and how to put
them in.
First, where do you get them? There are a number
of suppliers - but based on some recommendations from people on the Cozy
forum I purchased mine from PRINCETON CAPACITIVE FUEL LEVEL PROBES 1840
PEMBROKE DR SE, KENTWOOD, MI 49508 (616) 281-5193. Unfortunately they
don't have a web site but you can try this email address:
info@princeton-electronics.com.
Second, where do you put them? The answer of
course is "it depends". If you believe in the trustworthiness of
electronics and don't mind digging into foam and fiberglass to make a
repair then you can bury them in the fairing next to the turtleback. If
you want access to the head of the unit but don't think you'll ever need
to get the probe out, you can mount it inside the turtleback with the
probe going through the fairing. I wanted to be able to remove and
reinstall if I had to - call me paranoid! So I chose to mount them just
inside the baggage comparment. But hey, wait, the "baggage compartment"
isn't much bigger than some women's purses - do I really want that probe
head sticking out an inch into the opening? No. So I decided the only
alternative was to recess it into the wall of the baggage bulkhead so that
the head would be just slightly recessed and can be afixed with a
cover. |
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How do you recess something that is
and inch thick into a wall that is only a little more than 3/8" thick, you
ask? By making the wall thicker, obviously! Here I've made a 3" disk as a
template and I am cutting out a frame that will be fixed to the inside of
the fuel tank wall. |
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Here is the assembly that I will flox to the
inside wall. The frame is on the left - that is what will be
permanent. |
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Here is the location in the fuel
tank wall where the probe head will be mounted. This view is the left tank
from the aft looking forward. The black circle is where the hole
will be cut. |
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Heres the frame assembly ready to
go against the fuel tank wall. The peel-ply and plastic are
stretched and wedged by the disk - it also insures a flat surface for the
probe head to sit on. Nails are angled out all around the disk to
hold it in place. |
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The hole is cut and we're ready to
go. |
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The assembly has been floxed and
glassed in place. |
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The disk has been removed - note
the nails that go straight - they are what held the disk in position
during glassing. |
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With disk and peel-ply removed you
can see the light! |
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Then we need to glass the baggage
comparment side. In order to make sure that we get a perfectly flat base
for the fuel probes to sit on I've made a round plug out of
scrap 3/4" partical board. I then covered it in electrical tape
- WITHOUT overlapping joints on the inside so it is flat. |
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Here's a view from inside the
fuselage looking back from the passengers seat. Notice Vance's fuel sight
gage to the left of the baggage opening. |
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Trial fitting of the fuel probe
into the recess. It fit perfectly - so now it's time to figure out how to
get the wires down to the electrical conduit beneath the arm rest. To do
this I took my 12" long 1/4" drill and drilled down through the top of the
baggage bulkhead, through the top of the recess and then through the
bottom of the recess where the wires will be when the probe is in place.
Then I continued drilling at an angle until I came out the strake bottom
right where it joins the fuselage. (See pictures below for were it comes
out). |
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Inside the tank the probe is way to
long and needs to be bent first up and then down. Unfortunately I didn't
get a picture of how it is bent, but the idea is to get the top of the
measuring portion of the probe (about 5" from the head) as close to the
top of the tank as possible and the bottom of the probe as close to the
bottom of the tank as possible (without obstructing the flow of gas into
the bottom of the probe). So think of a stock market plot - its
flat briefly and then the price goes up (that's where I buy) - and then it
turns around and crashes (that's where I usually sell). |
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It might be a little tough to see -
but this is the bottom of the strake - yep the plane is upside down - and
the little orange tube that is floxed in the joint between the strake and
the fuselage is where the wires come out from the baggage bulkhead and go
into the fuselage. I used the insulation off a piece of extension
cord as a conduit from the bulkhead hole to the inside of the fuselage.
That way I can easily pull the wires out and get them back in later. |
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Here is where the wires come out on the inside - just below my armrest
flange (I have made removeable armrests). The second set of wires is
coming out of Vance Atkins' lighted fuel sight gages.
Now all that remains is to run a set of wires down the electical
conduit (bottom of picture) to the instrument panel. |
| Top - Back to Strakes |