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Removable Wing Tanks on a Mustang II

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DLrocket89

Well-Known Member
Joined
Aug 10, 2009
Messages
249
Location
Janesville, Wi
Hi all,

This is based on a thread on the Mustang II Yahoo group, wanted to open it up for broader consideration.

Background on the Mustang II:

The "standard" fuel tank is a 25 gallon header tank between the instrument panel and the firewall (mine will most likely only be 20 gallons to increase leg room). Given that many (if not most) MIIs fly on O-360s, that's good for a couple of hours of flight. Most people add extra tanks in some way, shape, or form.

The most common option is wet wings, which yields 18 gallons per wing, bringing the total past 50 gallons (usable). The MII has a folding wing provision that I intend on using...the wing tanks are in the section that folds up, so it can lead to issues as the tanks needs to be close to dry to fold properly. I'm trying to stay away from wet wings because of this.

Another option is a pair of 6 gallon tanks under the cockpit in the wing carrythrough structure (MII is a low-wing plane). Gives you 12 more gallons. You can also install a 10 gallon tank under the seat, which bothers me from a safety standpoint, so I'm not intending on doing that.

The last common option is wing tip tanks, which add about 8 gallons, but at a cost of over $2K. Ouch.

The plane will be dual mission for me. 1) Local, "around the patch" flying. Obviously not a cub, that's OK. Mild acrobatics too, which is only possible if the weight is kept low. 2) Long distance cross country

My requirements are 20 gallons for mission 1, 50 gallons for mission 2. Will not build an underseat tank, center section tank OK, strong preference away from wet wings, don't want wing tip tanks.

Given all of that, I started thinking about ways to increase capacity. I was watching a history channel episode about the P-51, and they mentioned the drop tanks. My question is, can removable (NOT drop tanks) be implimented on the Mustang II?

What I invision is an "attachment" fitting on the underside of the wing. When the tank is not installed, it is covered with a fiberglass shell that keeps it clean aerodynamically. When the tank is installed, it provides a track (or rail) that the tank will slide into place on. The track would mount primarily to the main spar, with the rear spear being involved to help keep it steady. Next to that, fuel and vent lines would run out and mount to the tank.

The idea is that when I want to do aerobatics/around the patch flying, I am minus the weight of tanks, any excess fuel they might be carrying, and perhaps the transfer pump if I planned things correctly. When I want long duration capability, put the tanks on, plumb them up, and fuel capacity goes up by 250%.

Regarding fuel tank oscillation/severe structural failure, I was thinking back to my high power rocketry days, and remembered the Barrowman equations: Barrowman Equations
Basically, they let you figure out the Center of Pressure of a rocket shaped-body. I figure, use this method to determine CP of the tanks and design them so that you can never get CG behind CP, and the tanks should be stable (coupled with a stiff mounting system).

I know there are probably easier ways of doing something like this...I'm a couple of years away (at the soonest) from getting to the part of the plane where I'll be working on this part, so this is something of a thought experiment. If it gets thought out clearly enough, I'd strongly consider implimenting it though.

Comments anyone?
 
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