Props?

If I picked Jabiru 3300 to power my aircraft, which prop should I used? (two
bladed or three bladed?)
Pros and Cons on two bladed and three bladed propeller?

Toks Desalu
PP-SEL
Dying to fly!

Generally speaking, 3 blades tend to be quieter and have better climb.
2 blades are better for top speed, if you have the prop clearance for
a longer prop.

IIRC the Jabiru likes to run high RPMs, so a shorter 3 blade might be
required to keep the tips subsonic.


On Sun, 09 Nov 2003 21:03:26 GMT, "Toks Desalu"
wrote:

:If I picked Jabiru 3300 to power my aircraft, which prop should I used? (two
:bladed or three bladed?)
:Pros and Cons on two bladed and three bladed propeller?
:
:Toks Desalu
:PP-SEL
ying to fly!
:

Dear Toks,

About Propellers:

How many blades that are best is more a question of how many blades you
need? What will make the decision a HP's, Prop-speed, Tip-speed,
structural limits, blade thickness and forward speed.

When the optimal Diameter is calculated it might be to big, for some reason,
and a smaller diameter is necessarily, that led to wider blades or more
blades. It is shown that 3 blades instead of 2 not effect the efficiency, 4
blades is about 2% less effective then 2 blades, if everything else is kept
the same! (It takes 50% more power to run 3 blades with the same diameter
and pitch as 2 blades with same single blade width, at the same rotation
speed)

And it is better with 3 normal blade then 2 extra wide blades with the same
total blade area.

Some say that a bigger diameter is always better! That's right if you want
high static thrust, but most aircraft fly fast forward (more or less) and
when it goes faster it is necessarily to concentrate the power into a
smaller disk area, giving the air a higher speed through the propeller disk.
Then is it a choice of what you want your propeller to do for you, good
take-off and climb? High speed or something in between? If the aircraft have
an extended speed range it might be necessarily with an adjustable propeller
(but the diameter will still be a compromise)

Jan Carlsson

www.jcpropellerdesign.com


"Toks Desalu" skrev i meddelandet
news:yYxrb.112222$mZ5.744874@attbi_s54...
If I picked Jabiru 3300 to power my aircraft, which prop should I used?
(two
bladed or three bladed?)
Pros and Cons on two bladed and three bladed propeller?

Toks Desalu
PP-SEL
Dying to fly!