Mathematical Questions regarding lift

[outfrontframes]

I am new to AP and want to know what formula to use to calculate lift.
I have a new TRex600 that will be a dedicated AP ship and would like to calculate lifting ability/capacity.
I know I read the formula on here someplace but can not seem to find it now. Any help would be appreciated. Thanks. :D

[miami6]

The fomula I came up with Carry as little as possible in case you have to auto you can have a controlled ditch and not hurt anyone else --

[outfrontframes]

Thanks thats the plan but I still would like to know how to calculate everything. Weight vs disk size vs head speed etc..

[AZ ChopperCam]

there are way too many variable for thereto be a simple cut and dry equation.

reynolds number, temperature, airfoil shape, air pressure, alitude, rotor RPM, angle of attack, chord, span, etc, etc , etc.

I suggest doing alot of research on helicopter theory and aeronautical engineering if you want an exact number. Other wise just stick with what we all know. 600 class heli, I say stay less than 12lb AUW. (3000'MSL and lower)

[outfrontframes]

Is there a chart or something that depicts approx AUW per class of heli?
BTW Thanks for the info. I'll stick with that for now, as a starting point.

[MarkD]

Use one of these

http://www.scalepeople.com/retail_products.asp?subcategoryID=93

Attach one end to the ground and the other to the skids, hover and climb slowly untill the motor starts to bog down then get someone to read the scale :D

It'll give you an instand reading on the max the heli will lift

[flyinfool]

:WOW That sounds scary. :WOW

I would rather see you attach a container to the heli at the CG and slowly add weight till the heli performance degrades to what you would consider minimum acceptable.
This will give you the best idea of the capabilities of you, your system, and setup.
No one has to risk there life trying to read a scale with a heli at full power just above.

[MarkD]

:WOW That sounds scary. :WOW

Obviously I meant from a distance using binoculars or a digital camera's zoom :)

But then again there are some peeps that would just walk under the heli, this is where the Darwin theory comes into effect :roll:

[Stuka]

Give this a try. Should give you a start. Don't forget about the tail rotor and drivetrain losses. You can use this spreadsheet for the tail rotor also. Use thrust = 1.1*weight for hover. Let me know if you have any questions. A much better version is in the works. :)

Link: Basic Rotor Spreadsheet (http://www.runryder.com/helicopter/gallery/5564/Basic_Rotor_Spreadsheet.zip)

[flyinfool]

I guess it is the Safety Officer in me coming out and my high disbelief in the existence of common sense in the human race.

[outfrontframes]

Give this a try. Should give you a start. Don't forget about the tail rotor and drivetrain losses. You can use this spreadsheet for the tail rotor also. Use thrust = 1.1*weight for hover. Let me know if you have any questions. A much better version is in the works. :)

Link: Basic Rotor Spreadsheet (http://www.runryder.com/helicopter/gallery/5564/Basic_Rotor_Spreadsheet.zip)

Very nice. I will play around with this tonight for sure. I'll let ya know what I come up with and if I have any questions!! Thanks. :mrgreen:

[qb7ops]

Well done Stuka. It looks like you put a lot of work into the formula's of the worksheet. It will be good to work out potentail lift on paper (so to speak) prior to safely testing calcuations in practice.

If you can, please keep us updated on this post regarding your updated version.

[Nitrospazzz]

Stuka thanks for that spreadsheet, I've been trying to figure out a way to calculate lift. I have a couple formulas but they don't take into account altitude, wind, blade type, etc.

[Stuka]

Thanks guys. Let me know how well this works out for you. Seemed to give reasonable results for my Evo 90 but I haven't tried other models.

I was a little brief in my last post. To find the power required for the entire hovering helicopter, use the spreadsheet for the main rotor. The thrust should be set to roughly 1.1 times the weight because of the drag of the fuselage in the rotor wash. Plug in your geometry and rpm and have it solve for the collective required. It will give you power and torque. Use that torque to solve for the tail rotor thrust required. Then use the spreadsheet to solve for the tail rotor power required to produce that thrust. Add those two power required figures together to get the total. You can also correct for drivetrain and other losses.

Chris