The P-47 wing, or What am I looking at?

[Voyager]

The P-51, Tempest, and P-63 were all mid-war laminar flow designs. One of the P-47B's was fitted with a laminar flow wing in early 1942, but it did not show any performance improvement over the S-3 airfoil, so it wasn't just a matter of tooling or cost.

Tapered and elliptical wings have other drawbacks beyond cost. Because the lift drops as you get to the end of the wing, it tends to stall there first, robbing you of aileron control.

[JtD]

There's a difference between having a wing with a laminar flow design and having laminar flow over the wing. Surface quality in WW2 for the most part was not good enough to allow laminar flow airfoils to develop laminar flow to a larger extend than conventional airfoils do.

There's also a difference between building one prototype and building 15000 planes.

[Voyager]

While generally productivity would be a major consideration, the Spiteful added 20-40mph to the top speed of the Spitfire, but wasn't produced after all, in the case of the XP-47F I more curious as to why it lost 7-10mph with the laminar wing installed, given that that was pretty much the opposite of what happened to every other design that had a laminar wing tested on it.

That's what I'm really wondering.

[JtD]

The Spiteful wasn't just a Spitfire with a laminar flow wing, it was a completely new plane. Maybe they were as similar as the 109E and the 109F. That's not a reference for relative performance, and neither will be Typhoon/Tempest nor P-39/P-63 nor P-40/P-51.

Try looking at size, weight, surface quality and plane particulars instead of the airfoil for the XP-47F.