50cc planes on 23x8 props can't fly aerobatics!

[BR289]

I know my Extreme Flight 88" Yak does everything. I am running a 3W-55 on a can with a Beila 23 x 8 prop. I have a 23 x 8 3W wood prop on my EF Extra 300, same motor and can.

[Flyfalcons]

I think your theoretical stall speed is way off.

[as722]

	Quote: Originally Posted by Mike Anderson
	I've been doing some number crunching on 50cc class planes and I can't see how a 50cc motor turning a 23x8 prop will ever get the plane flying aerobatics. I'm feeling like the engineers who studied bees and determined they can't fly. Here's my line of thinking: Typical plane: 87"ws, 1450 sq in wing area, 17 lb auw, 12% to 14% thick zero camber, symmetrical airfoil (Clmax between .85 & .95) Theoretical stall speed is ~27 mph. Ideal flight envelope is 2.5 to 3 times the stall speed which is 68 to 81 mph. A typical 50cc motor will turn a typical 23x8 prop between 6500 & 7000 rpm and generate a pitch speed between 49 & 53 mph! The only way to fly this plane at around 50 mph is to raise the angle of attack and operate at a higher Cl. I can see the 23x8 as a good hovering / 3d prop, but for IMAC-style aerobatics, at very high AoA's the flight symmetry between inverted & upright flight would be terrible wouldn't it? I'm finding that for a desireable 3° AoA, to get the flight envelope back into the 2.5 to 3 times stall speed range, we need a 23x11 or 23x12 prop. Most people will say that a 50cc engine won't handle 23" props above 10" pitch, but could probably handle 22" props above 10" pitches. I haven't seen a lot of postings by people flying IMAC on 22"x12" props. So how do the IMAC guys do it????

The 23 x 8 prop is the most common 50 cc prop for a reason, It works !!
Stop trying to split atoms in half, go fly and have some fun.


Albert

[SpgBob]

This is stupid, put it together and go fly the dang thing. If you dont like something about it then change it. Must be really bored.

[Craven]

I can't believe I actually read your stupid thread.

[66stang]

I just bought a Vess 23a in support of this thread!

[Al Lewis]

Hell, if it weren't for my videos I'd think I was hallucinating!!! I'm sure they fly.

[Spaz]

	Quote: Originally Posted by wildhare
	Assuming your numbers are all accurate, I think the flaw here is that you are not accounting for the airfoil of the prop blades, which are the primary method of developing thrust. Forward thrust does not drop to zero when the plane is moving forward as fast as the calculated pitch x rpm velocity. TF

that is true, when Dave Gierke was doing Real Performance Measurement in model airplane news he was getting greater airspeed than pitch speed every time, if i remember right it was 5-10% more.. that is with measure onboard RPM and airspeed vs measured prop pitch calculation

[Altavillan]

We all know or should know that at rpm's above 5500 on a 23x8 prop, Einsteins theory starts to kick in. The faster you go the slower time crawls. So the prop thinks it's running sometime tomorrow but we mortals are stuck with the crawling thing go-in on. Then factor in the tendency for the blades to flex forward and well memorial day is a history lesson already to your prop. Futaba is working on a reciever with 4096 res to help us catch up a bit and some who are testing the things as we speak claim a tremendously more responsive feel to control response.

[mikedannielle]

	Quote: Originally Posted by 66stang
	I just bought a Vess 23a in support of this thread!

That made two of us.

[Craven]

2 words

Boost Tabs

[mikedannielle]

Variable pitch prop!