RCcalc - Simple software to calculate pitch speed, thrust, stall speed, etc.

[alexcmag]

My friends always ask me how will fly a aircraft model, if it can fly slow, the best propeller, and so on.

So I build a small software in Delphi, it uses wing span, wing chord, weight, airfoil, polar, propeller type/size and rpm and do some estimation of stall speed, best soar speed, pitch speed, thrust, etc.

It also do some suggestions of how the thrust ans pitch speed will work based on my experience with electric model airplanes.

This software is free, and the source code (for Delphi 4 and newer versions) is provided son anyone is who wants knows Delphi or Pascal can make modifications.

It is provided "as is", and I make no warranty of the results.

It can import airfoil if you have a bitmap and can call Mark Drela's XFOIL to calculate Polars.

The thrust is calculated using propeller data from ThrustXL (sorry, I forgot the name of the author).

To download please righ-click on this link: Right-click here and choose "save as" (http://planeta.terra.com.br/lazer/AeroMag/rccalc_1.zip)

[Aio_1]

Thanks,

I'll be interested to play with this when I get time.

Aidan

[hul]

To download please righ-click on this link: Right-click here and choose "save as" (http://planeta.terra.com.br/lazer/AeroMag/rccalc_1.zip)
looks nice but download doesn't work for me, tried Internet Explorer and Firefox

Hans

[alexcmag]

looks nice but download doesn't work for me, tried Internet Explorer and Firefox

Hans

Sorry, free ISP :(

To download must right-click and choose "save as".

Left click goes to an error screen.

Sometimes the server is busy and goes to an error screen too...

[hul]

must right-click and choose "save as".
did that but it saves something called rccalc_1.html (the error creen). Try later?

[sheerLuck]

Worked for me just now - saved a zip file...

Note that in the RCCalc program, English language may be selected, and it will retain your preference.

I know nothing about airfoils - except that several of my planes are flat foam. Is there an equivalent in the dropdown list of airfoils ?

Larry

[alexcmag]

Worked for me just now - saved a zip file...

Note that in the RCCalc program, English language may be selected, and it will retain your preference.

I know nothing about airfoils - except that several of my planes are flat foam. Is there an equivalent in the dropdown list of airfoils ?

Larry

Thanks for remember that, I make it bilingual but forgot to explain how to select language...

I will try calc the polars of flat panel and add it to the software.

[andyg]

can you use it to find the thrust needed for a certain plane?

[alexcmag]

can you use it to find the thrust needed for a certain plane?

It can do a reasonable prediction.

The exact thrust needed for a plane is very hard to calculate, because depends mostly of the fuselage, but if you select your wing airfoil, polar, span and chord, weight and RPM it can tell you the stall speed, best soaring speed, safe speed, and the aproximate drag at these speeds.

It was designed mostly for park flyers, so safe speed is calculated to be 20% or 5m/s greater then stall speed, in my personal tests it is enough to avoid stalling when gets some tail wind or when loose speed at turns.

Then it calculates the static thrust (based on RPM and prop model) and the percentage of static thrust per weight.

If the static thrust is below 33% of the weigh it shows a red alert (33% is the minimum static thrust I can fly with an e-glider).

If static thrust is below 50% it shows a yellow alert (a few low-drag models can have a good flight with static thrust lower then 50% of the weight).

If static thrust is over 60% it shows a green message (most aircraft models fly well with static thrust over 60% of its weight).

Over 80% a blue message tells that it is enough for a lot of fun.

Over 100% a blue message tells even a flat plate can fly.

Over 130% a blue message tells even a rock can fly.

And so on...

After that it takes the pitch speed and compares with safe speed. If the pitch speed isn't enough to achieve safe speed it shows a red alert on the right side of the pitch speed (I had a C-115 with almost 100% of static thrust that has a bad flyers, because pitch-speed is lower then stall speed).

[ATARI-2600]

Great program ... ;)

[adam_one]

Hi, alexcmag

It seems to be a very useful tool.
May I ask you which formula is used to calculate thrust as a function of rpm?
Thanks for sharing your work with us.

[alexcmag]

Hi, alexcmag

It seems to be a very useful tool.
May I ask you which formula is used to calculate thrust as a function of rpm?
Thanks for sharing your work with us.

The thrust is calculated using propeller data from ThrustXL (sorry, I forgot the name of the author).

I used pro data from ThrustXL: http://www.badcock.net/ThrustXL/ and inside the RCcalc interpolates the points to calc thrust to any RPM.

[CptanPanic]

Can you include a flat wing type?

[bekaflight]

What is "speed"?

[alexcmag]

Can you include a flat wing type?

I am trying to get some free time to include a flat wing and a undercambered airfoil like the SlowStick's wing.

There will be a new release soon.

[alexcmag]

What is "speed"?

Sorry, I don't understand the question.

Speed is generally measured in miles/hour, meters/second or kilometers/hour and determines how much you move in space on that time.

In a car, boat you can ride at any speed because the surface has enough density to prevent it from sinking.

But an airplane needs to be moving to keep airborne.

The slowest speed an airplane can fly is the "stall speed". Slower then this and it will fall.

But fly at stall speed is too dangerous and is not efficient, there is a lot of drag and any error can make it fall.

In this software I calc stall speed and a safe speed that is greater than stall speed to keep it flying even when it does turns or try to ascend.

The propeller of an airplane is sometimes compared to a screw. The pitch speed is the measure of how much this "screw" would move in the air when turning at a such rotation speed (measured in rotations per minute in this software).

The pitch speed must never be lower then the safe speed, or the airplane will fly too close of the stall speed, making it hard and dangerous to pilot.