Vertical Stabiliser Design

[dghob]

Have been trying to establish the reasons designers opted for single vertical stabilisers on aircraft such as the Boeing B17, whereas other designs notably Avro Lancaster and B24 Liberator had twin fin arrangements.

It seems to be the case that both configurations provided stability around the horizontal plane needed for accurate bombing results as well as general handling. Would it be the case that a twin fin design was able to absorb more battle damage ie, one fin damaged, the other remaining functional?

I'd look forward to any information on the subject.

dghob

[dixi188]

I've always thought that the British love of the twin tail was due to the height of the hangars and what would fit in them.

[KriVa]

Whether it's true or not, I haven't got a clue.... But I was always told the configuration was dependant on the hangars they were stored in. Just like dixi says.

[Lumps]

Tails more directly in prop slipstream?

[Tinstaafl]

Probably a combination of the things mentioned: A possible desire to reduce the overall height, improve fin/rudder effectiveness by using prop slipstream, redundancy, and maybe improve space for a tail gunner.

Drawbacks would probably include more complicated control runs and two structures to be included in non-firing areas for waist & dorsal guns.

[Chu Chu]

The Lockheed Electra (and a number of civilian aircraft) had double fins, so the reasons can't be exclusively military.

[etudiant]

Afaik, in the Lockheed case, twin tails were a fallback to address inadequate fin area.
There are some claims that the military liked twin tails because it gave a clear view behind the aircraft, so hostiles had no place to hide. The B25 might be an example of that, no tail gun but an upper turret that could fire straight back. However, I've not seen any designer memoirs that mention that.

[grounded27]

DRAG, the bottom line.

[Brian Abraham]

On the money etudiant. The to be famous Kelly Johnson did the majority of the wind tunnel work on the Lockheed 10. It initially had a single fin and proved to be inadequate, so he suggested twin fins. What drove that decision rather than just making the single fin larger I've not seen recorded. The Beech 18 in some conversions has had its twin fins removed and replaced with a single.

Edited to add a very good insight into the 1941 thinking behind twin V single tail

1941 | 1585 | Flight Archive