prop. numbers/ sizes
10-19-2003, 06:01 PM
#2
Senior Member
Join Date: Oct 2002
Location: Philadelphia,
PA
Posts: 2,065
Likes: 0
Received 0 Likes
on
0 Posts
RE: prop. numbers/ sizes
The first number is the diameter of the prop and the second number is the pitch of the blades. Your example would probably be in inches.
10-19-2003, 09:12 PM
#4
Senior Member
My Feedback: (16)
Join Date: Apr 2002
Location: Locust Grove,
GA
Posts: 12,942
Likes: 0
Received 0 Likes
on
0 Posts
RE: prop. numbers/ sizes
Most propellers in the US are in inches.
11x7 propeller is 280mm diameter (length of the propeller) and 178mm pitch. The distance that the propeller will travel in one revolution if everything is perfect.
11x7 propeller is 280mm diameter (length of the propeller) and 178mm pitch. The distance that the propeller will travel in one revolution if everything is perfect.
ORIGINAL: Homster
Can someone tell me what the numbers on a propellar means. exampel 11 x 7.
thanks for your help!
Can someone tell me what the numbers on a propellar means. exampel 11 x 7.
thanks for your help!
10-20-2003, 12:06 AM
#5
Senior Member
My Feedback: (5)
Join Date: Jul 2003
Location: Tacoma, WA
Posts: 2,668
Likes: 0
Received 0 Likes
on
0 Posts
RE: prop. numbers/ sizes
But, of course, everything is NOT perfect 
On the other hand, if things were perfect and planes really did go forward at the rate their pitch says they should, there would be no 3D as we know it
On the other hand, if things were perfect and planes really did go forward at the rate their pitch says they should, there would be no 3D as we know it
10-23-2003, 06:01 AM
#6
Senior Member
Join Date: Jul 2003
Location: Meadow Lake,
SK, CANADA
Posts: 199
Likes: 0
Received 0 Likes
on
0 Posts
RE: prop. numbers/ sizes
These numbers are fictional but the general Idea is here. Plz use a prop chart to keep you in the right size category recommended for your engine.
Just to expand a bit on this! an 11 x 7 prop would pull you 7 inches forward for every
revolution of the prop. where as an 11 x 4 prop would pull you only 4 inches forward per revolution. thus giving you a lower gear ratio. better for takeoff but less top speed.
Now the engine is designed to run best at a certain RPM. so we have to make sure we load it hard enough so that it doesn't overrev and self destruct. or load it to hard that it overheats the engine and self destructs.
If your engine runs an 11x7 prop and flies ok. but you want more top speed then go to, say an 11x8 or if you want more takeoff power but less top speed then go to a 12x4 prop. it is 1 inch larger to still load the engine, but the lower pitch still lets it rev up to desired RPM. and you give up high speed for low speed high thrust. say for hovering.
An 11x7 2 Blade prop is (albeit somewhat) similar to a 10x8 3 Blade prop. minus 1 inch diameter and add 1 inch pitch. three blades are relatively ineficient (sp?) compared to a 2 Blade but help with low clearance problems.
Clear as mud?
Smoky.
Just to expand a bit on this! an 11 x 7 prop would pull you 7 inches forward for every
revolution of the prop. where as an 11 x 4 prop would pull you only 4 inches forward per revolution. thus giving you a lower gear ratio. better for takeoff but less top speed.
Now the engine is designed to run best at a certain RPM. so we have to make sure we load it hard enough so that it doesn't overrev and self destruct. or load it to hard that it overheats the engine and self destructs.
If your engine runs an 11x7 prop and flies ok. but you want more top speed then go to, say an 11x8 or if you want more takeoff power but less top speed then go to a 12x4 prop. it is 1 inch larger to still load the engine, but the lower pitch still lets it rev up to desired RPM. and you give up high speed for low speed high thrust. say for hovering.
An 11x7 2 Blade prop is (albeit somewhat) similar to a 10x8 3 Blade prop. minus 1 inch diameter and add 1 inch pitch. three blades are relatively ineficient (sp?) compared to a 2 Blade but help with low clearance problems.
Clear as mud?
Smoky.
