Fun, Learning, Friendship and Mutual Respect
START  HERE


Unregistered
Go Back   HeliFreak > R/C Helicopters > Aerodynamics, Physics and Engineering


Aerodynamics, Physics and Engineering Aerodynamics, Physics and Engineering Discussions


Reply
 
Thread Tools Display Modes
Old 05-26-2012, 01:06 AM   #1
Martin353
Registered Users
 
Posts: 113
 

Join Date: Mar 2011
Location: Uk
Default Blade lift

Is it possible to work out the extra lift gained (or lost) from different sized blades if running at the same hs? i.e what % extra lift would you get from changing from a 550 size to a 600 size blade.


---
I am here: http://tapatalk.com/map.php?0pdghl
I'd rather be flying than typing
Martin353 is offline        Reply With Quote
Old 05-26-2012, 01:17 PM   #2
Martin353
Registered Users
 
Posts: 113
Thread Starter Thread Starter
 

Join Date: Mar 2011
Location: Uk
Default

I'm kinda guessing that be a no then lol


---
I am here: http://tapatalk.com/map.php?lbotvo
I'd rather be flying than typing
Martin353 is offline        Reply With Quote
Old 05-26-2012, 01:50 PM   #3
TowPilot
HF Support
 
Posts: 18,632
 
My HF Map location
Join Date: Jun 2008
Location: Wisconsin
Default

You could use a small bucket with weights that you add until it can't be lifted.

Change blades, go through the process again to see the difference of vertical lift.

This doesn't account for how a blade will perform during forward flight during maneuvers though.
__________________
TowPilot is offline        Reply With Quote
Old 05-26-2012, 05:36 PM   #4
npomeroy
Registered Users
 
Posts: 1,989
 
My HF Map location
Join Date: Aug 2009
Location: Hawkes Bay, New Zealand
Default

Quote:
Originally Posted by Martin353 View Post
I'm kinda guessing that be a no then lol

---
I am here: http://tapatalk.com/map.php?lbotvo
I'd rather be flying than typing
Hang in there. I don't think many are viewing this forum yet.
There will be a simple calculation for the theoretical lift increase, and I think it will be significant as much of the lift comes from the outer end ofthe blade.
__________________
Nelson JR DSX9 II; Stretched Atom 500 in Bell 222 body , TRex550 in Funkey/Century Jet Ranger. Stretched TRex550 in 600 size AS350 - under construction. SK720 all round. Trex 450 S for sport practice. MCP-X.
npomeroy is offline        Reply With Quote
Old 05-26-2012, 06:47 PM   #5
TowPilot
HF Support
 
Posts: 18,632
 
My HF Map location
Join Date: Jun 2008
Location: Wisconsin
Default

And there is going to be a cost, and increased drag for increased lift. The calculation will also probably show, the additional power needed, to generate increased lift. Just a guess.
__________________
TowPilot is offline        Reply With Quote
Old 05-26-2012, 10:06 PM   #6
extrapilot
Registered Users
 

Join Date: Aug 2010
Location: AZ
Default

There is no simple calculation; most of the parameters that define lift are undefined here. Easiest option is to throw the machine on a scale, and run it up in negative pitch 550 vs 600 blades, and see the delta.

Just based on blade theory, by my calcs, the 53” dia rotor will generate approx 55% more thrust than the 47” dia rotor at a given non-stalled AOI/RPM. Best to measure- the calcs dont account for important variables.
__________________
"The problem with quotes found on the internet is you have no way of confirming their authenticity." - Abraham Lincoln
extrapilot is offline        Reply With Quote
Old 05-26-2012, 10:36 PM   #7
npomeroy
Registered Users
 
Posts: 1,989
 
My HF Map location
Join Date: Aug 2009
Location: Hawkes Bay, New Zealand
Default

Quote:
Originally Posted by extrapilot View Post
There is no simple calculation; most of the parameters that define lift are undefined here. Easiest option is to throw the machine on a scale, and run it up in negative pitch 550 vs 600 blades, and see the delta.

Just based on blade theory, by my calcs, the 53 dia rotor will generate approx 55% more thrust than the 47 dia rotor at a given non-stalled AOI/RPM. Best to measure- the calcs dont account for important variables.
I hoped you would contribute to this one extrapilot.
Do you not agree that in the way the OP phrased the question there is an assumption of "all other things being equal" e.g. HS and blade design; so shouldn't these cancel out and allow a genuinely useful calculation?
__________________
Nelson JR DSX9 II; Stretched Atom 500 in Bell 222 body , TRex550 in Funkey/Century Jet Ranger. Stretched TRex550 in 600 size AS350 - under construction. SK720 all round. Trex 450 S for sport practice. MCP-X.
npomeroy is offline        Reply With Quote
Old 05-27-2012, 05:13 AM   #8
Martin353
Registered Users
 
Posts: 113
Thread Starter Thread Starter
 

Join Date: Mar 2011
Location: Uk
Default

Hi all.

Thanks for the replies. The question was asked assuming everything else remained the same. I.e same pinion, motor, batts etc and just changing the blades.
Some interesting points made tho. Where do u get thus info from? I've looked on google but can't find anything.


---
I am here: http://tapatalk.com/map.php?bu2d3z
I'd rather be flying than typing
Martin353 is offline        Reply With Quote
Old 05-27-2012, 09:17 AM   #9
YoungBull
Registered Users
 
Posts: 170
 

Join Date: May 2012
Location: Australi, QLD, Nth Brisbane
Default

Bear in mind I've had a few drinks and a noob. Extrapilot sounds ontrack.

Could you (ignoring all other parameters, motor, headspeed) posibly measure by blade pitch?
eg: throttle hold at 2000rpm head speed. Set max throw at +1, then +2, then +3 ect ect, until lift has occured -place tape on skids that break at 1kg of force - test with kitchen scales

550 blade surface area(a) / 600 blade surface area (b)
Pitch req for a and b. eg: a = 3deg, b = 2deg
diff of 1 deg ( remebering head speed and motor not inc)
The increased surface area of b req 1 deg less pitch = 50% lift increase.

Almost impossible calc as any % will change through full collective range, fwd flight, ect.
Or maybe this link could help
http://www.ehow.com/how_7680704_calc...or-blades.html

__________________
450 se, 450 v2, using Jr 2610.
550e 3GX , Dx7, 1 sat. RF6, Redback LiPo's.
600efl Pro, 3GX, bec, Castle HV80, 2 sats.

Last edited by YoungBull; 05-27-2012 at 09:21 AM.. Reason: read above post again
YoungBull is offline        Reply With Quote
Old 05-29-2012, 03:47 PM   #10
jmmccain
Registered Users
 
Posts: 256
 
My HF Map location
Join Date: May 2008
Location: Birmingham, AL
Default

Simply? Yes. Accurately? Don't know.

In this thread I posted a number of equations for lift, drag, torque, and power. They are all nothing more than very simple integrals. I know the three for drag, torque, and power work quite well for both models and full scale. The one for lift probably works well too, but I don't know what range of coefficient to plug into it (lack of data).
__________________
Joseph (too many folks want to call me Jim )

Like that lucky old sun, give me nothin' to do, but roll around heaven all day.
jmmccain is offline        Reply With Quote
Reply




Unregistered
Go Back   HeliFreak > R/C Helicopters > Aerodynamics, Physics and Engineering


Aerodynamics, Physics and Engineering Aerodynamics, Physics and Engineering Discussions

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


Copyright © 2004-2015 by RCGroups.com, LLC except where otherwise indicated. The HeliFreak.com logo is a trademark of RCGroups.com, LLC.