I’ll now explain about “Angle of attack” and Blade twist.
Like any aerofoil the blade needs to meet the relative airflow at an angle to produce thrust. The “Angle of Attack” is the angle between the Chord line and the relative airflow. (Don’t confuse this with “Blade Angle” which is the angle between the plane of rotation and the chord line). On a prop the most efficient angle is 4 degrees, this is called the “Optimum Angle of Attack”. Diagram 1 should explain this.
A question I’m often asked is why is a prop blade “Twisted” from root to tip. The simple answer is that different parts of the blade are moving at different speeds- Diagram 2 should explain this.
Finally I’ve attached 2 pics of a target prop, to which I’ve attached markers to show blade twist from root to tip.
KeithMac
Attachments:
By: geedee - 17th October 2002 at 13:14
RE: Propellers Pt.2
[updated:LAST EDITED ON 17-10-02 AT 01:15 PM (GMT)]Keith
I asked a mate of mine in the UK and he’s replied with the following :-
The prop will come off a two cylinder ,horizontally opposed engine,the name of which escapes me.
The drones which that engine would go on are called:
Banshee (a delta wing) and SKEET which used to be called MATS “A” ,(MATS “B” was the 10cc Merco glowplug engine powered aircraft I used to fly when I learned to fly radio-controlled aircraft).
I shall look for some pictures for you.
As soon as he delivers, I’ll update this thread
Cheers
Gary
By: keithmac - 15th October 2002 at 18:37
RE: Propellers Pt.2
Hi Gary.
To be honest, I haven’t the faintest idea! It was on the windowsill in the office of the Stores Warrant Officer at RAF Mount Pleasant when I saw it. On one knew what is was or what it came from. As it was not on anyone’s charge, I was given it as a leaving present when I finished my tour in the Falklands. It anyone knows what it’s off, I’ll be as interested as you in finding out!
KeithMac
By: geedee - 14th October 2002 at 18:06
RE: Propellers Pt.2
Thanks for that Keith
By the way, do you know what target drone the prop fits in your piccies ?.
I have one and would love to know what it was destined for before decorating my bookshelves.
Cheers
Gary
Attachments:
By: neilly - 6th October 2002 at 16:37
RE: Propellers Pt.2
Hi Keith,
Excellent, keep it coming.
Neilly
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October 6, 2002 at 4:20 pm