Welcome to The FlyingGiants! - please login or click this bar to join our community...

 

Welcome to The FlyingGiants Community! We're all about fun, and inside you'll find the greatest, friendliest, and most helpful group of people around! If this is your first time visiting, please check out site, and click here to sign up! We hope to see you soon!!

Go Back   FlyingGiants > Technology > Aerodynamics
Forgot your password? Create a new account


Reply
 
Thread Tools
Old 05-22-2008, 05:13 AM   #1
Mike Anderson
ago involo ergo sum
 
Mike Anderson's Avatar
 
Join Date: Jun 2007
Location: Ottawa Ontario Canada
Posts: 211
Default 50cc planes on 23x8 props can't fly aerobatics!

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????
Mike Anderson is offline   Reply With Quote
Old 05-22-2008, 06:30 AM   #2
Scott Gerber
Closed Account
 
Scott Gerber's Avatar
 
Join Date: Jun 2007
Age: 56
Posts: 3,108
Default Re: 50cc planes on 23x8 props can't fly aerobatics!

Mike, you must be as bored as I am waiting for that plane to show up...


Scott
Scott Gerber is offline   Reply With Quote
Old 05-22-2008, 06:48 AM   #3
flying skunks
I got a BIG BLOCK now ......
 
flying skunks's Avatar
 
Join Date: May 2006
Location: Flying with the Best of Friends
Posts: 16,133
Default Re: 50cc planes on 23x8 props can't fly aerobatics!

Mike , the best way to understand a 50cc airplane is to put together a 50ccer with a Vess 23a and put it through its paces,with that combo you can go compete in IMAC if you so desire.my $.02
__________________
Donnie
Chief Aircraft ........Godfrey Designs
Florida Freestyle Aerobatics Association
Triple Tree Youth Masters , July 27-28
Torch Engines ..........Bunny Up
flying skunks is offline   Reply With Quote
Old 05-22-2008, 07:00 AM   #4
brandonduley
Let's go flying!!
 
brandonduley's Avatar
 
Join Date: Mar 2007
Location: Lebanon, OH
Age: 30
Posts: 27,055
Default Re: 50cc planes on 23x8 props can't fly aerobatics!

i am flying with a mejlick 23x8 on a da-50 and it flies imac style aerobatics just fine
__________________
brandonduley is offline   Reply With Quote
Old 05-22-2008, 07:53 AM   #5
Mike Anderson
ago involo ergo sum
 
Mike Anderson's Avatar
 
Join Date: Jun 2007
Location: Ottawa Ontario Canada
Posts: 211
Default Re: 50cc planes on 23x8 props can't fly aerobatics!

Oh yeah! I know they fly aerobatics. It's just that the pitch speed is so freakin low! I'm surprised by the numbers that's all.
Mike Anderson is offline   Reply With Quote
Old 05-22-2008, 07:56 AM   #6
Ih82crash
Team Japaleno hard man brand
 
Ih82crash's Avatar
 
Join Date: Jan 2007
Location: Elko, NV
Posts: 633
Default Re: 50cc planes on 23x8 props can't fly aerobatics!

You need to look at thrust not top end speed. During 3D the plane might be traveling 0 or 1 miles per hour. It is the thrust from the prop that keeps the plane aloft
Ih82crash is offline   Reply With Quote
Old 05-22-2008, 08:05 AM   #7
WangoTango
Bad-ass Super Contributor!
 
WangoTango's Avatar
 
Join Date: Feb 2007
Location: Conroe, Texas U.S.A.
Posts: 4,110
Default Re: 50cc planes on 23x8 props can't fly aerobatics!

Quote: Originally Posted by Scott Gerber
View Post
Mike, you must be as bored as I am waiting for that plane to show up...


Scott
Scott,
I was reading all of Mike's numbers and trying to absorb all the info to see where he was coming from.... I'm thinking to myself: Man, this guy needs to get his mind off things...... I wish that stinkin' Yak would get here!! Then I scroll down and there's your post about him being bored and wanting that plane to show up! Great minds think alike! LOL!
WT
WangoTango is offline   Reply With Quote
Old 05-22-2008, 08:09 AM   #8
Scott Gerber
Closed Account
 
Scott Gerber's Avatar
 
Join Date: Jun 2007
Age: 56
Posts: 3,108
Default Re: 50cc planes on 23x8 props can't fly aerobatics!





Scott
Scott Gerber is offline   Reply With Quote
Old 05-22-2008, 08:20 AM   #9
Mike Anderson
ago involo ergo sum
 
Mike Anderson's Avatar
 
Join Date: Jun 2007
Location: Ottawa Ontario Canada
Posts: 211
Default Re: 50cc planes on 23x8 props can fly aerobatics!

Actually, I was doing some research for an article I'm drafting on competing in IMAC with electric planes. Hence the number crunching and the apparent boredom. I was hoping someone with an aerodynamics background might comment.

While thinking this issue over, I realised that most IMAC figures are either up or down and most have a vertical up or down component, so modelling level flight for power plant performance calcs is pretty much useless. (Relates to the thrust comment above too) It actually makes it easier to write the article.

Back to waiting for the Yak . . . . . .
Mike Anderson is offline   Reply With Quote
Old 05-22-2008, 08:30 AM   #10
WangoTango
Bad-ass Super Contributor!
 
WangoTango's Avatar
 
Join Date: Feb 2007
Location: Conroe, Texas U.S.A.
Posts: 4,110
Default Re: 50cc planes on 23x8 props can fly aerobatics!

Quote: Originally Posted by Mike Anderson
View Post
Actually, I was doing some research for an article I'm drafting on competing in IMAC with electric planes. Hence the number crunching and the apparent boredom. I was hoping someone with an aerodynamics background might comment.

While thinking this issue over, I realised that most IMAC figures are either up or down and most have a vertical up or down component, so modelling level flight for power plant performance calcs is pretty much useless. (Relates to the thrust comment above too) It actually makes it easier to write the article.

Back to waiting for the Yak . . . . . .
Mike,
I couldn't agree with you more....... You want to check the YAK status today or is it Scott's turn!!?? LOL!
WT
WangoTango is offline   Reply With Quote
Old 05-22-2008, 08:33 AM   #11
Scott Gerber
Closed Account
 
Scott Gerber's Avatar
 
Join Date: Jun 2007
Age: 56
Posts: 3,108
Default Re: 50cc planes on 23x8 props can't fly aerobatics!

Already did.... nothing's changed yet.....



Scott
Scott Gerber is offline   Reply With Quote
Old 05-22-2008, 08:49 AM   #12
wildhare
on a vacation
 
wildhare's Avatar
 
Join Date: Jul 2006
Location: Texas
Posts: 1,487
Default Re: 50cc planes on 23x8 props can't fly aerobatics!

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
wildhare is offline   Reply With Quote
Old 05-22-2008, 09:02 AM   #13
BR289
Pro Pit Biotch
 
BR289's Avatar
 
Join Date: Jan 2006
Age: 48
Posts: 4,060
Default Re: 50cc planes on 23x8 props can't fly aerobatics!

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.
__________________
Extreme Flight RC
www.extremeflightrc.com
Aircraft International
www.aircraftinternational.com
Stansphotos.com
BR289 is offline   Reply With Quote
Old 05-23-2008, 04:06 PM   #14
Flyfalcons
Hero to the masses
 
Flyfalcons's Avatar
 
Join Date: Sep 2006
Location: United States, WA, Enumclaw
Age: 34
Posts: 4,159
Default Re: 50cc planes on 23x8 props can't fly aerobatics!

I think your theoretical stall speed is way off.
__________________
Ryan Winslow
www.flypau.com
Flyfalcons is offline   Reply With Quote
Old 05-23-2008, 04:11 PM   #15
as722
Bad-ass Super Contributor!
 
as722's Avatar
 
Join Date: Jan 2006
Location: Pennsyvania
Age: 41
Posts: 1,252
Default Re: 50cc planes on 23x8 props can't fly aerobatics!

Quote: Originally Posted by Mike Anderson
View Post
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
__________________
Team Jr
http://www.jramericas.com/
as722 is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
IDIOTS SmoothFlying General Discussion 27 05-27-2008 03:05 PM
FlyingGiants Keyboard Deathmatch!! madmax General Discussion 282 11-22-2007 08:01 AM
Do bigger planes fly better? niccolo98 General Discussion 107 05-16-2007 11:44 AM
nitro planes fly swallow harv Nitro Power 7 01-04-2007 11:34 PM
Great Planes, Flat Outs 3d?????? Lizano Foamies 18 02-05-2006 09:43 PM


All times are GMT -5. The time now is 04:24 AM.

All Flyinggiants.com content copyright 2006-2014 by RCGroups.com, LLC except where otherwise indicated. The Flyinggiants.com logo is a trademark of RCGroups.com, LLC.
Please report any misuse of our trademarks or copyright violations using the contact form.
RCGroups Network :: RCGroups :: Crackroll :: RC Cars

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.