Fisher XP-75 outer wings Q


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19 May 2006
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I've always admired both the XP-75 & the P-75A, maybe because it's a combo of airplanes & my favorite movie monster being Frankenstein. :) I had read that the original outer wings were from a P-51 but later changed to the P-40 wing. It used an F4U main gear, which would work well with the P-40 wing. However, if or when the P-51 wing was used or intended, does anyone know if it would have used a standard P-51 main gear or would the wing have been modifed to use the F4U/P-40 gear. I guess too, if they wanted a heavier gear, maybe used a P-47 gear or maybe modified the F4U gear to fold inward without rotating. If they stayed with the inward retracting P-51 gear, the SBD/A-24 wing center section would have had to be modded then. I just got Valom's kits of these a/c & was thinking of getting another & put P-51 wings on it.
Maybe this could be helpfull..

XP-75 ; a Donovan Berlin design at the end of his career.

tail : Douglas A-24
landing gear : Vought F4U
wings :p-40E
after inspection of the mock-up ,3 May 1943, the change to
the P-51 wing was ordered.
After considerable shortcomings manifested themselves some redisign
was introduced.Modified tail-new cockpit-V-3420-23 engine.
This plane became the XP-75A

source : P-51 Mustang.The development of the Long Range Fighter.
Paul A. Ludwig. Classic Publications 2003
The XP-75 wing definitely appears to be a straight steal from the P-40 Warhawk. While there's a lot of sources which state the wing was changed to a P-51 wing, I see no evidence to support that. The P-75A retains the same landing gear fairings as the XP-75's P-40-derived wing.

It appears that the P-75A wing was also a P-40 wing, but with clipped wingtips. A change to the airfoil would be a major change in terms of the plane's flying qualities.

A good source for answers would be the Incomplete Guide to Airfoil Usage ( Unfortunately, while it shows the XP-75 with the same airfoil as the P-40, it has nothing for the P-75A. The smart money says that it still used the same airfoil cross sections as the P-40, though.
I have always thought the Fisher XP-75 to have been both a waist of time and resources!

I read somewhere that Fisher used the ad hock XP-75 design as an excuse to not have to build under license other company’s aircraft for the US War Effort, so as to have minimal impact on its civil manufacturing capacity, with the wars end in sight.

Agreed, Pioneer. It's hard to think of any good reason why you'd want to build a spare-parts fighter. You generally want to build an aircraft that's optimized for the mission, not for the parts that are already in production.

I think that the use of the P-40 wing has much to due with the fact that both were Don Berlin designs. Dr. Berlin was confident in the flying qualities of the P-40 airfoil, so he kept it for his new fighter. I assume that the rest of the design process went something like this:
--We need a bigger fuselage that can accommodate the V-3420 engine
--The P-75 is going to be bigger than the P-40, so we can't reuse the P-40 tail unit. What do we have in the way of a bigger tail unit? The Dauntless? That will do the job.
--The P-75 is heavier than the P-40, so we need new landing gear. What can we use? Corsair landing gear should d the trick!

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