Q & A about Aircraft, Armor, Weapons , Transport and Ships

[McColm]

As I said before, I came across the A.W. Apolo which was fitted with both 3 and four propellers. As no other aircraft has been fitted out this way, I can assume that there's no advantage gained in performance or endurance otherwise there would be more than one example listed.

[PR19_Kit]

Yes there was.

Consolidated Coronados were fitted with 4 bladers on the inboard engines and 3 bladers on the outboards after they found some resonance problems in the fuselage when using 3 bladers on all four engines.

[Gondor]

Yes there was.

Consolidated Coronados were fitted with 4 bladers on the inboard engines and 3 bladers on the outboards after they found some resonance problems in the fuselage when using 3 bladers on all four engines.

I believe that the same kind of problem was found with some versions of Halifax, but I could be getting mixed up as I am writing this off the top of my head.

Gondor

[McColm]

Thanks Kit, 

[McColm]

Question 13)
Convair had the trademark twin tail fins on most of their aircraft in the flying prototype stage changing over to the single vertical tail fin  on such models as the PB4Y Privateer, B-36 and XC-99.
Is there a big difference in stability between a single and twin or multiple tail fins?

I know deck space on an aircraft carrier or the height of the hanger roof does play a part in the selection but I'm not too sure why Convair changed designs?

[wuzak]

Question 13)
Convair had the trademark twin tail fins on most of their aircraft in the flying prototype stage changing over to the single vertical tail fin  on such models as the PB4Y Privateer, B-36 and XC-99.
Is there a big difference in stability between a single and twin or multiple tail fins?

I know deck space on an aircraft carrier or the height of the hanger roof does play a part in the selection but I'm not too sure why Convair changed designs?

The PB4Y was the interesting one, being based on the twin fin B-24.

The initial drawings of the B-36 and XC-99 showed twin fins, while the initial B-36 win dtunnel models had twin fins. It may have been because of stability issues that it was changed.

[PR19_Kit]

Or strength and weight?

I can't help but think that a couple of fins perched on the ends of the tailplane would need extra strengthening of the tailplane to react the yaw loads. If there's only one fin on the centreline the taillplane only has to react to its own self-generated pitch loads and can be lighter as a result.

[wuzak]

Or strength and weight?

I can't help but think that a couple of fins perched on the ends of the tailplane would need extra strengthening of the tailplane to react the yaw loads. If there's only one fin on the centreline the taillplane only has to react to its own self-generated pitch loads and can be lighter as a result.

Excellent point.

Just found this in Magnesium Overcast by Dennis R. Jenkins:

When the Model 36 mockup had been approved in September 1942, it used vertical stabilizers mounted on the ends of each horizontal stabilizer, much like the B-24. There were initial concerns that the vertical stabilizers could shear of during a heavy landing or under severe flight conditions - continued evaluation led to the twin tail being deleted in favour of a single 47-foot high vertical stabilizer. This change would decrease structural weight by 3,850 pounds, provide additional directional stability, and lower the base drag.