Today's Message Index:
----------------------
1. 09:24 PM - Re: Tank Shape/Support (taildrags)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Tank Shape/Support |
My guess is that there are dozens of Air Campers that have the same nose tank as
Mike Cuy's sketch depicts. It's almost exactly what is on the nose of my airplane,
and you can get the gist of how it fits in the fuselage here:
http://flysquirrel.net/piets/repairs/Image-10.JPG
Although the tank on 41CC holds a few ounces one side or the other of 16 gallons,
I consider the last couple of gallons in the tank to be unusable because below
that level, the fuel will not flow reliably to the carburetor by gravity.
In fact, in the 3-point attitude (ground ops or slow flight) I can guarantee
you that it is unusable. Ask me how I know ;o)
Now back to the question at hand, which is the Corvair-Piet combination. Here
you have more options, such as constructing the tank in the same style as the
usual nose tank but a bit deeper. Since the Corvair requires an electrical system
and can thus use an electric fuel pump, gravity flow to the carb is not a
requirement. However, and as Terry pointed out, do some W&B studies because
even though standard Air Campers tend to be tail-heavy, with a Corvair on the
nose plus more fuel, plus electrical system, starter, and battery- you may need
to look at what 18 gallons of fuel up there will do. You'll definitely need
to placard it 'Rear Seat Solo Only' unless you really work some magic with where
you put the weight.
I just ran the W&B spreadsheet for my airplane with another 2 gallons in the tank
and although it doesn't change much in the solo configuration (raises the minimum
pilot weight at maximum forward CG with full fuel to 112 lbs), it makes
the loading configurations with a passenger a bit fussier. For example, my airplane
(empty weight 633) is 5 lbs under max gross of 1088 lbs with 18 gallons
in the tank if I have a standard 170 lb pilot and 170 lb passenger and the CG
stays nicely within the envelope all the way down to 3 gallons remaining in
the tank. However, if I have a 210 lb pilot and a 135 lb passenger, I'm at gross
and within CG but when I burn it down to only 3 gallons left in the tank,
the airplane is 1.1" out of aft end of the CG range and if I get to a short field
in the afternoon when it's a bit bumpy and I've been in the air for a couple
of hours... low fuel... aft CG... twitchy airplane in the bumpy air... it's
going to be light on the stick and easier to stall.
If you want to get more fuel capacity, as some have wanted to, there are other
options. The deHavilland Moth-style 'hump' centersection wing tank has a pleasing
appearance to some eyes, and it moves the fuel to a spot where fuel burn
doesn't shift the CG appreciably like it does in the nose tank. By all means,
play with a W&B spreadsheet to see what effect all these things will have on
your operating envelope. Build it light to give you the most leeway in payload,
build it so the wing and landing gear geometry give the airplane the best attitude
in the 3-point configuration, and work out CG loadings on paper before
you set things permanently. It's much easier with paper and pencil than doing
it with the welding torch, wrenches, shims, weights, and other kludges after
it's built.
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=447859#447859
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|