problems using speed calculator

[rude5150]

I am trying to find out how fast my Zonda setup will be. I am using 2 tp 4060 1570 kv motors with(2) swordfish 220+ on 6s with x448 props. I have put info in and got 3.93mph. Can someone, please give me help?

[10gauge]

~63mph. Years ago, I developed an empirically-derived formula for calculating speed for cats, hydros, and monos. You just plug in prop pitch, prop dia., kV brushless motor, LiPo V. I've been away from this hobby for several years, but enjoy the mathematics. Here's that thread:

http://forums.offshoreelectrics.com/...ed)&highlight=

There are variables such as prop modification, frictional losses, aerodynamics, weight, etc. However, your setup is very close to my M-1 in my signature, so you should get in the low 60s.

[tlandauer]

Thank you 10gauge!
May I ask a question? Any provision to calculate a twin drive cat?

Good grief! What did i type??

[rude5150]

Thanks for the feedback 10gauge. Is there a way to estimate speeds of my twin setup?also I plan to add the m850/3blade props for my Zonda. Does this set up seem safe. tlandauer, thanks for asking question. Also will the 850/3blade props seem safe with my setup tlandauer?

[10gauge]

Years ago, someone asked about a twin-cat formula. So I derived a hypothetical formula for that too. It's post #27 in the link from above. Here it is again:

http://forums.offshoreelectrics.com/...ed)&highlight=

[robbo1]

10gauge, that formula is magic! I punched in all the specs, it gave me a speed of 63mph, precisely the speed gps'd.

[rude5150]

Ok guys, what's the speed with m850 props and what's the voltage that I would input for the 6s twin setup? Did you calculate single 6s per motor or 2pacs per motors? What's the speeds with m850 3 blade?

[10gauge]

Ok guys, what's the speed with m850 props and what's the voltage that I would input for the 6s twin setup? Did you calculate single 6s per motor or 2pacs per motors? What's the speeds with m850 3 blade?

Formula is for 1P (single pack) per motor. LiPos are like your cell phone. 1 cell = 3.7V. So 6S: 3.7V/cell x6 = 22.2V. The rest is prop factor and pitch....

[tlandauer]

Years ago, someone asked about a twin-cat formula. So I derived a hypothetical formula for that too. It's post #27 in the link from above. Here it is again:

http://forums.offshoreelectrics.com/...ed)&highlight=

Thanks!!!

[10gauge]

I am glad guys! I've always liked RC boats as a kid, but never got into it until brushless motors were mainstay. Years later, I received good advice from experienced racers and builders here and on RRR when I joined the forums in 2007. This is a great hobby, providing hours of enjoyment in the outdoors, capturing the imagination of children, and allowing one to be creative, as well as competitive. I wanted to give back to the hobby community in a useful way, so I decided to publish these formulas back in 2008.

[rude5150]

Thanks 10gauge and tlandauer.

[rude5150]

This is knowledge is like GOLD, thanks for sharing guys.

[rude5150]

10gauge, is there a, way to figure out the biggest size props that I can run with out without blowing an esc ? And way to calculate the amps that setup will use with prop?

[10gauge]

10gauge, is there a, way to figure out the biggest size props that I can run with out without blowing an esc ? And way to calculate the amps that setup will use with prop?

That's the next logical progression, but I don't have a data logger to reliably measure amp draw, rpm, and temps. I've sadly been away from the hobby for about 5 years, and that technology was just coming into being.

Instead of getting into the electromechanical specs of each particular motor like windings, poles, resistance, weight, rpm, etc. It would be better if I could set up a comparative field study with several people with a range of setups, and common motors. I could collect the gamut of data based on hull design, LiPos, prop factor, speed, amp draw, for the most common motors. Then equate all the data into a neat equation.

My practice keeps me busy! Last time I ran a boat, I was using a Hitec 75MHz radio and 25C was the highest LiPo rating.... Our harsh N.E. weather has me excited for anything summer related this year, and that includes boats!

[rude5150]

The Zonda on youtube did 75mph with 4519 props on 6s with 2140 kv motor. By your calculations, it should have gone 109.8mph. Am I correct 10gauge?