Posted 29 May 2005 - 06:58 PM
Posted 29 May 2005 - 10:31 PM
What is it you hope to achieve?
Anyone ever considered experimenting with a 3, 4, 5, or 6 bladed scimatar prop?.... If you read this post please post a reply and let me know what you think, even if its not long thanks...
Posted 30 May 2005 - 12:03 PM
Posted 31 May 2005 - 06:35 AM
( the Air Force ) switched from the 4 bladed C-130 props to the six bladed curved props being used on the J models. "The propeller has a swept blade design, which provides rapid take off and climb performance
This is true, but the blades where much longer, larger, and engine put out a lot more HP. If I’m not mistaken, the Hell Cat put out about 1600+ HP. I don't know if a 200hp engine will do. I do know that length of the blades will determine the number of blades you can put on a prop with out losing efficiency. Some one with an engineering degree should probably chime in here.
Posted 31 May 2005 - 04:52 PM
Posted 02 June 2005 - 06:02 PM
Posted 10 June 2005 - 05:43 PM
Posted 13 June 2005 - 08:45 AM
Just a question, How about 2 , 2 bladed props counter rotating, using a gear box to do this.???
I don't know of anyone who has done this, but this guy http://www.infortel.com/cozy/ put in two Suzuki 1600cc water cooled 100HP each. With TWO 3-blade coaxial counter-rotating (independent) pusher.
Posted 10 December 2016 - 01:12 AM
Scimatar blades increases parasitic drag over a strait blade. Reason: When an airfoil is producing lift the air not only flow chordwise, it also starts to move outboard. This causes the air to increase it's travel from LE to TE. A swept forward blade is more efficient than strait or sweep back. I have only seen the Germans experiment with this technology. Their Hanza jet had forward sweep wings. one of our X planes has forward sweep wings, I think it was the X-35, don't remember now. I saw a German ultralight with a forward swept prop blades, fixed pitch. This makes sense because it makes the air flowing over the foil pass across in the shortest path, less parasitic drag. Also as you all know, high aspect ratio wings (lifting foils) are more efficient than mattress wings. That is why sailplanes have high aspect ration wings.
Same with propeller blades but that gets to be a problem with prop blades because of mechanical reasons. And for the prop blade the airspeed is different for every station along the blade. Consequently of course, the twist in the blade has to be different for every station along the blade.
It would be nice if the twist could be made variable like the pitch (Bata) can be. But that is not practical. Of the three parameters that a prop has to acomodate, Bata or pitch, RPM and AofA (Angle of Attack) only two of the three can be made variable. Twist is fixed.
The reason I bring up twist is because when you crunch the numbers the numbers say that for all the variable rpms, the variable airspeeds, the variable angles of attack, it would be nice of you had control over the twist of each blade. But so far we can't do that.
If we could train the termites, in wood blades, to hold hands and sway to the right tune then we could make a prop blade a little more efficient.
If anyone wants to crunch some numbers, write me an e-mail and I will give you some math formulas that will put a twist in your brain.
BTW as some of you know, we took the C-90 powered V-EZ to Kanab for the fly in. We didn't wind any race. We don't run our engine up in the 3K+ rpm zone. But did anyone notice how short the takeoff run was?
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