For LW expertens

[SFRT - Frenchy]

I was just wondering why the Spit started with 2 blades and went all the way to 5 blades on his later versions ... most allied had 4 blades.

Why did the LW, 109s and FW (up to TA152) always sticked with 3 blades? Is it only a question of power output?

[R4M]

assked this same question some time ago.


British went for props with more blades

Germans went for props with broader blades. A Ta152's prop is way broader than a 190A's one.

I recall understanding that broader blade prop helps more at hi altitude, more blades help more at low altitude.


This is what I know on the matter...Some of the engineer-lover guys around here will help you much more than this, tho

[fdiron]

Planes used multiple blades when they needed lots of prop area but didnt have alot of ground clearance.  However, the more blades of a propellor you have, the less effecient it is.  Therefor it is better to have two large blades than 5 small blades.  This is because the turbulent air of multiple blades is not very effecient.

[Kratzer]

Well... I'll probably screw this up... but...

If a propeller breaks the speed of sound, it quickly becomes very inefficient, so there is a maximum speed at which you can spin a propeller without it doing so that is proportional to the length of the propeller - just like a record player, or a bicyle, the outside edge is moving much faster than the inside hub.  As a result, you can't just spin the motor faster and faster to get more power.

So if you have a more powerful engine, and want more thrust, you can either make the propeller blades longer, which results in the above problem, make them wider, which also reduces efficiency, or you can make more of them, and make them shorter.  Your more powerful engine in the Spit XIV is capable of more work than the that of the Spit I, but there are limits on how fast you can make the propeller spin, so to take advantage of the extra work capability of the larger engine, they added more blades.

I think that's right...

[funkedup]

Germans had a prop blade shortage.  They whittled them out of tree bark, but they couldn't afford more than 3 per plane.

[Kratzer]

Here's an article on german vs. allied prop design (sort of).

http://home.att.net/~historyzone/Fisher.html

And another on the subject:
http://www.djaerotech.com/dj_askjd/dj_questions/fourblade.html

[hazed-]

You guys know nothing of the complex mechanics involved here do you?

you thought you'd throw in some rediculous explanation for 3 or 2 or 4 blades!!

Well the more informed among us know its all down to the huge rubber band that runs the lengh of every planes fuselage!

the thicker the rubber band the tougher the prop with big metal hook needs to be! so with thick plastic props its best to have loads of blades so it looks cool!

The germans were just die cast SHOW OFFS with their 'ladidaaa' thin but still strong technology!! dont ya just hate em for it???

I cant believe these people dont know the real technical aviation stuff !

[tofri at work]

Originally posted by hazed-

Well the more informed among us know its all down to the huge rubber band that runs the lengh of every planes fuselage!

I cant believe these people dont know the real technical aviation stuff !

Hazed got the REAL reason, why Germans were at such a bad mood at the end of the war.
They had no more latex for the real important things in life.