Kyleb wrote:
A longer (taller) fin would gain efficiency through a higher aspect ratio, so you could net out to less vertical surface for the same stability and/or control authority. In theory, that would save some weight, although there are some structural advantages to the twin fin design (lower bending moment, being one of them).
I had always worked with the understanding that 2 x twin = 1 x single because surface area would be the same. Thanks for the clarification.
Matt Gunsch wrote:
The Ercoupe does not have 2 rudders to make them "less" effective, it has 2 rudders that are outside of the influence of the prop slipstream. On a single tail plane, there is more air pushing on one side than the other because of the prop, if the rudders are further out than the prop diameter, there is no influence from the air.
It took me a couple read-throughs to understand, as the first few times I thought you were saying the same thing I was. You're saying that the Ercoupe
does have twin tails to put them outside of the propwash,
but this is to eliminate differential effect on the rudder(s), not to reduce their effectiveness.
Matt Gunsch wrote:
I do know a little about Ercoupes, this one is mine. It is a 1950 model 415G, one of 8 left flying, It was built by Erco, which is the same company that made the nose and waist turrets on the PB4Y-2, and nose turrets on the PB4Y-1.
I never thought about that connection. Nice plane, by the way!
wolf wrote:
What Consolidated and the USN found however, that the twin tails made the B-24 unstable, had to maintain formation and difficult to get on the step. The single tail B-24N (and a retro kit) would have eliminated a vast majority of the handing issues of the B-24.
Why would twin tails made the B-24 unstable? As you suggested, a quick search of XB-24K provided mentions of the change being for stability (as well as a
suggestion that field of fire was improved), but none went any further as to explaining why it had an effect.
EDIT: Nevermind, I'm an idiot that did not put two and two together with Kyleb's explanation above.
wolf wrote:
Bombers in Blue: PB4Y-2 Privateers and PB4Y-1 Liberators by Frederick Johnsen I believe has photos of the wind test models for the PB4Y-2 showing the original XPB4Y-2 developed with twin tails vs single tail.
Thanks for providing a reference. I can always appreciate that!