Propeller Cuffs…P-51 & B-29

Excellent Responses & Many Thanks

Thanks to all for your responses to my question.
The improvements they provided are understandable. I can see that the propeller blades would produce more thrust & give more cooling at the hub with them than without.
But than again if the manufactures knew this why did some a/c have them and others not. Such as the Grummen Wildcat versus the Grummen Hellcat. Or why didn’t such types as the P-39 & P-40 use them. These two needed any improvement in performance that one could find! Perhaps their mission altitude didn’t require them. Such as the P-51 warbirds now, who needs altitude performance when the mission is at lower altitudes.
During the war perhaps the production of aircraft numbers was more important than the advantage that the cuffs gave.
Thanks also for the update on the company which provides them now for installation on Mustangs. Looking forward to seeing them on Mustangs wherever possible. I like the looks!!

http://www.rswproducts.com/index.php/p-51-blade-cuffs

Blade cuffs

I have an old Thunderbolt blade from a scrapyard, complete with cuff.
The cuffs were engineered affairs, not just black sponge.
The base of the cuff, next to the hub, was a small alloy or mag casting, the cuff proper is a wrap-around sheet alloy forming and there are are fasteners to allow the whole assembly to be broken down and removed from the blade when it is overhauled.
The particular cuff just described was fitted to a Curtiss Electric (hollow steel) blade and a B-50 prop hub and single-stub blade and cuff we have is of the same constuction.
The Hamilton-Standard cuffs were similar and would be removed when the blade was overhauled to allow a blade inspection to take place.
This is one of the reasons why they aren’t used any more as they are expensive to produce and fit and, at the low altitudes vintage warbirds operate at these days, are not required – that is unless you are prepared to pay the extra to have them fitted for authenticity – which many aren’t – the costs of operating the aircraft already being high enough.
Post war, the Americans used them a lot to improve blade efficiencies and engine cooling though hardly any British aircraft had them, two exceptions being the Beverley and the Twin Pioneer. These aircraft often operated hot & high and required the extra cooling for the radial engines at high ambient temperatures as well as the slight increase in thrust in the thinner air.
The Twin-Pin cuffs were made of Micarta (a phenolic resin-bonded material similar to paxolin) and were foam filled and bonded to the blade roots so were destroyed and then replaced after the blade was overhauled.
The cuff is now in widespread use for high-power turboprop engines due to the quest for ever higher efficiencies from propeller blades without increasing the diameter. It’s cheaper to fit a cuff than produce a wider and heavier blade. It also allows the circular-section root of the blade to produce useful thrust and less drag though with large diameter spinners and wide blade root-ends (a la Belfast) they were not always necessary.

Anon.

made of a black aerated rubbery sponge

It’s the distictly broader blade root found on a number of american props such as Thunderbolts,Wildcats,etc. I looks as though it’s been bandaged round. 🙂

John

Hello All,
I am about to expose my ignorance of some of the finer details of aviation hardware and I hope you will forgive me, and give me a simple answer!
Just what the hell is a propellor cuff?
TIA
Resmoroh

On the Mustang the cuffs were devised to improve air flow in to the carb intake duct. I believe much later they were found to be not actually that effective. California Propeller can fit them these days for the full period look.

I believe the cuffs on B-29s were just one of the (many) attempted fixes to improve the cooling on the engines – very prone to catastrophic overheating.

G-BIXL/ ‘Miss Helen’ has a cuffed prop, but AFAIK, all other UK P-51D Mustangs have not. I believe the inspection regime is more onerous with cuffs, but Yak11 Fan would know the full details.