P51 Prop. 'Cuffs'.

[Airframes]

This is purely for my own interest. Can anybody tell me the reason, or function, of the root 'cuffs' on the Hamilton Standard prop on Mustangs, and, for example, the Curtiss Electric props on Marauders?
I vaguely recall they were something to do with coping with 'dead' or 'dirty' air close to the fuselage/nacelle. A former R.A.F. Mustang pilot told me that the 'Aeroproduct' prop on the P51K (cuffless), was a little problematical compared to the H.S. prop on the 'D', and didn't give as much 'oomph'(!).

[Geedee]

Bump !

Likewise, I'm after drawings of the Hamilton Standard Prop cuffs fitted to the 51...if any-one has these drawings / blueprints, I will be in your debt !

From what i've found so far, the original cuffs fitted to radials was to increase the cooling air flow directly into the front row of cyclindres . Not so sure about this working on a close-cowled in-line like the Merlin, but hey ho, I could be wrong.

[Capt. Vick]

Yeah I heard the same as you Gary and also wondered why they were on liquid cooled aircraft, but I guess in those cases it was just to get the extra "umpf". Like most (if not all) P-47's had cuffed props but when they engined a couple with the first Chrysler Hemi (a liquid cooled engine) they went with cuffless Curtiss Electric props.

Regards, Jim

[Colin1]

I've got this NACA report from March 1944, it may be of some technical interest:

Effect in Flight of the Propeller Cuffs and Spinner on Pressure Recovery in Front of a Double-Row Radial Aircraft Engine in a Twin-Engine Airplane

By Carl Ellisman
Aircraft Engine Research Laboratory
Cleveland Ohio

[gumbyk]

Interesting report, Colin.

From reading it, it appears that the spinner and cuffs had a detrimental effect on the cooling of the engine. The opposite of what I would have expected.

My thoughts are that the cuffs on the P-51 were to try and make as much of the length of the blade an aerofoil shape, and hence thrust-producing, as possible. As they are outside the profile of the cowling, they are availble to provide thrust.

[Colin1]

Originally Posted by gumbyk

From reading it, it appears that the spinner and cuffs had a detrimental effect on the cooling of the engine. The opposite of what I would have expected

Indeed
me too, I'd have thought all that cross-sectional area provided by the cuffs would have been absolutely shovelling cold air into the nacelle

[gumbyk]

But, thinking about it further, I guess if the limiting factor is how fast the air can escape, then it doesn't really matter how much you push in. Especially in flight, where you have the ram-air effect pushing it in anyway

[Colin1]

Originally Posted by gumbyk

But, thinking about it further, I guess if the limiting factor is how fast the air can escape, then it doesn't really matter how much you push in. Especially in flight, where you have the ram-air effect pushing it in anyway

There is that
but that would apply equally to non-cuffed configs and temps seem to run higher for cuffed configs, assuming the same airstream exit capacity for both configs.