Solved The right prop for my scratch built Rc plane

[Dawson]

Every plane is different and has different needs, so I can't tell you what prop to use without finding answers to those questions and running the numbers myself. So, how about we go through the list of things you don't know and/or don't know how to find and come up with the answers together?

https://store.flitetest.com/ft-radial-4030-510kv-monster-brushless-motor/

Battery- https://www.amazon.com/dp/B07JP8K1WK/?tag=lstir-20

Esc- https://store.flitetest.com/flite-test-80a-esc-w-xt90-connector/

Sorry didn’t realize I pasted the Same link 3 times here are the correct links

 

[Tench745]

What can you tell me about the plane?
Do you have any pictures?
I saw that it has a 7.5 foot wingspan with an estimated weight of 10-12lbs.
How much wing area does it have?
What kind of flying do you want to do with it? Do you want it to fly relatively scale, or be fast? Do you want STOL characteristics? Do you want to do some mild aerobatics or go 3D?

 

[Dawson]

What can you tell me about the plane?
Do you have any pictures?
I saw that it has a 7.5 foot wingspan with an estimated weight of 10-12lbs.
How much wing area does it have?
What kind of flying do you want to do with it? Do you want it to fly relatively scale, or be fast? Do you want STOL characteristics? Do you want to do some mild aerobatics or go 3D?

I would probably just like to have enough thrust to fly good. I don’t need to do huge aerobatics or insane speed. It’s supposed to be like a huge cub so just want it to fly good.

 

[Tench745]

I can't find anywhere that says what amperage or wattage the FT Monster Radial is rated to, but the one review in the FT store said they ran an 18x8 prop on 6S and were drawing 90 amps. That means the motor can handle at least 22.2V x 90A =1998 Watts and you'll burn out the ESC before you have to worry about frying the motor.

According to eCalc, the 14x8 mentioned before should give you around 11lbs of thrust, so you might be able to hover depending on what your final weight is. That will be more than enough thrust to fly and will accelerate the plane to flying speed pretty quickly.
Estimated speed is 65 MPH.
That should draw around 64 amps, so if you flew full throttle the whole time on your 6000mah battery pack you would get about five and a half minutes of flight time.
6 amp hours/64 amps= .094 hrs
.094 hr x 60 minutes= 5.64 minutes
I suspect that plane will fly at about 3/4 throttle and get more like 10 minute flights.

What is the chord length of your wing? That's the measurement from the leading edge to the trailing edge.
If you multiply the chord length by the wingspan it will give you the wing area.

 

[Dawson]

I can't find anywhere that says what amperage or wattage the FT Monster Radial is rated to, but the one review in the FT store said they ran an 18x8 prop on 6S and were drawing 90 amps. That means the motor can handle at least 22.2V x 90A =1998 Watts and you'll burn out the ESC before you have to worry about frying the motor.

According to eCalc, the 14x8 mentioned before should give you around 11lbs of thrust, so you might be able to hover depending on what your final weight is. That will be more than enough thrust to fly and will accelerate the plane to flying speed pretty quickly.
Estimated speed is 65 MPH.
That should draw around 64 amps, so if you flew full throttle the whole time on your 6000mah battery pack you would get about five and a half minutes of flight time.
6 amp hours/64 amps= .094 hrs
.094 hr x 60 minutes= 5.64 minutes
I suspect that plane will fly at about 3/4 throttle and get more like 10 minute flights.

What is the chord length of your wing? That's the measurement from the leading edge to the trailing edge.
If you multiply the chord length by the wingspan it will give you the wing area.

Wow. Thank you so much for that. That sounds perfect for how I want this plane to fly. The chord length is 13 inches.

 

[Tench745]

Cool, so a wing area of about 1170 in². Plugging that into the stall speed calculator, and assuming the plane comes out on the heavy side at 12 lbs, the estimated stall speed is 24 MPH.
If the plane comes in closer to 10 lbs that drops to 22mph.

 

[FlyingTyger]

The reason I suggested a 14x8 and not anything larger, was to keep the amps within the safe range of the ESC. The motor I think is capable of more.
Thanks @Tench745 for helping explain all this a little better.

 

[Dawson]

Cool, so a wing area of about 1170 in². Plugging that into the stall speed calculator, and assuming the plane comes out on the heavy side at 12 lbs, the estimated stall speed is 24 MPH.
If the plane comes in closer to 10 lbs that drops to 22mph.

Alright, thanks

 

[Dawson]

The reason I suggested a 14x8 and not anything larger, was to keep the amps within the safe range of the ESC. The motor I think is capable of more.
Thanks @Tench745 for helping explain all this a little better.

Alright, thanks

 

[Dawson]

The reason I suggested a 14x8 and not anything larger, was to keep the amps within the safe range of the ESC. The motor I think is capable of more.
Thanks @Tench745 for helping explain all this a little better.

So my wheels and reamer came today and just finished up the landing gear. Weight scale wasn’t working but not it is and it says about 5 lbs. I estimate it to be about 8 lbs with battery and rudder wheel. I was looking at the reamer and was wondering how do you use it? Does it attach to an electric drill? Do you use something to crank it by hand?
Thanks.

 

[FlyingTyger]

So my wheels and reamer came today and just finished up the landing gear. Weight scale wasn’t working but not it is and it says about 5 lbs. I estimate it to be about 8 lbs with battery and rudder wheel. I was looking at the reamer and was wondering how do you use it? Does it attach to an electric drill? Do you use something to crank it by hand?
Thanks.

Drill. They work similar to a drill bit. But since they only cut on the sides so you aren't as likely to get the hole off center or crooked.

 

[Dawson]

Drill. They work similar to a drill bit. But since they only cut on the sides so you aren't as likely to get the hole off center or crooked.

Alright. Thank you.

 

[Tench745]

If you have a handle for a tap from a tap and die set, they can work too.

 

[Dawson]

If you have a handle for a tap from a tap and die set, they can work too.

Ok