3 and 4 bladed props

[renrich]

I have a question and perhaps some of you informed technical types can answer it. Why was it that the P47 always used a 4 bladed prop when the Hellcat and Corsair, almost the same size and with roughly the same engine carried 3 bladed props until close to the end of the war? Also , the Jug started to use the paddle bladed prop I believe in 1944 to enhance it's climb performance while I don't believe the Hellcat or Corsair ever used the paddle bladed prop.

[Wurger]

There is somewhere the similar thread at the forum about props.Try to find this,please.

regards,

BTW. I've found this topic, the link is :
http://www.ww2aircraft.net/forum/avi...rops-8135.html (3 Blade vs 4 Blade props)

[renrich]

Thanks Wurger, for the referral. I went back and reviewed that thread and in fact I posted in it. I still don't understand technically speaking, why the difference in props in the three similar AC except it must have something to do with the difference in altitude capabilities and requirements.

[Dashthree]

The Spitfire, Mustang,Corsair and P-47 started out with three blade props.As more powerful engines were developed there needed to be more prop surface to efficiently utilize the increased power.One can either lengthen the blades or add more blades. To lengthen the blades requires longer gear legs with all of the engineering and other penalties that this implies.The Corsair already had a gull wing for just this reason;prop clearance.Another good example is the five blade prop on a Spitfire Mk XIV.

[Crumpp]

As more powerful engines were developed there needed to be more prop surface to efficiently utilize the increased power.One can either lengthen the blades or add more blades.

Propellers are the most complicated piece of engineering on the aircraft IMHO.

Adding blades increase the power absorbtion but reduces the efficiency of the propeller. It also adds weight.

None of the engines in WWII were so powerful that adding extra blades was a requirement. It was all about small gains in specific portions of the envelope that the designers wanted to achieve.

All the best,

Crumpp

[renrich]

Not to belabor the point but the question is (1) the Corsair and Hellcat had 2100 hp engines(in the early models) with 3 blade props and the P47 also had 2100 HP and used a 4 blade prop. Why? (2) Later the P47 went to a paddle blade prop but the Corsair went to 4 blade prop in the 4-model while the Hellcat stuck with a 3 blade prop in the 5-model and neither used the paddle blade prop. Why?

[Jank]

Wasn't the P-47 up to 2,535hp when the paddle blades were installed? Did they retrofit earlier versions with the 2,300hp engine? (I'm not sure) At some point in 1944, the P-47D was cleared for 2,600hp with the new fuel.

It may just be that since the P-47 was such a dog in a climb that it alone was the subject of efforts to bring the climb rate up to a respectable level. Francis Gabreski commented that after the paddle blades were introduced, the German's could no longer just climb away to escape before getting blasted.

[Crumpp]

ASK DJ Aerotech Question

[mad_max]

From how I understand the P-47's with the "needle" blades provided slightly better
high speed, but lower climb rate and the "paddle" blade Jugs had slighter lower speed, but
a better climb rate (300-400 ft/min supposedly).

The 56th FG did have some Jugs retrofitted with the "paddle" blade prop. What mark I
don't recollect right now. I do know they weren't used on non-water engines and D-5 or older
couldn't be retrofitted with water.

[renrich]

My reference shows that paddle blade props begin to be fitted in Dec 1943 along with water injection on one squadron at a time. I believe the water injection brought the combat power up to 2300hp. Military power was 2000 hp. It also said that those mods enabled the P47 to outclimb 190s below 15000 ft.