Forum for aerodynamics, physics, engineering?

[sarpilot]

Subscribed…
This should be an interesting forum…

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[rdlohr]

Originally Posted by WillJames

Looks like a forum is going to be created. Thank you for your input guys.

Excellent! Love it!

Rick

[joel0407]

I have been searching for the most efficient setup on my 450pro for about 18 months now. I started by getting a Castle ESC so I could log every flight. I have over 120 logs now.

Next was to get a lower Kv motor and step up the voltage of the battery 3s – 4s. Voltage is more efficient than current as higher current creates more heat which is lost energy.

I didn’t want to go to 6s as the batteries gain weight and size for the extra division of cells and I didn’t need that much power.

I set the head speed as low as I could without losing stability. That being said, I now think I should go lower. The problem I have with going lower is I need a lower Kv motor to keep it in the most efficient operating range.

I have flown various blades and this is about where I am at now. I had flown all of the Align variants and the last set were Spin Blades Asymmetrical. I was under the opinion that the asymmetrical blades would be more efficient but this was not what I found and this is where I need to go further. The Spin Blades are a much wider cord and I believe they create more drag.

Providing a symmetrical blade is not causing turbulence by being at too steep of and attack angle then Asymmetrical blade will be of no benefit. At the speed of our small heli rotors there is little chance of too much pitch and not enough air speed.

I am wondering if I can slow the rotor enough to get the benefit of the Asymmetrical blades without losing too much stability causing the heli to no longer be flyable.

Today I learn a little about the limit of forward flight speed of the heli. Obviously the advancing blade is travelling faster than the heli itself and the retreating heli is travelling slower than the heli. Today I have learnt that it is bad for the advancing blade to exceed Mach 1. Also the retreating blade needs to maintain a forward speed fast enough not to stall. From this we can deduce that the rotor has to fit in a small window of head speed to achieve maximum forward speed. This is where I believe the Asymmetrical blades will be of an advantage.

I thought that Asymmetrical blades only worked with a bigger heli. In theory they work better with a smaller heli due to blade speed being slower.

Where my first test went wrong was I was testing with static hovering and not attempting continuous forward flight. It’s during forward flight with the slowest possible head speed that the benefit of Asymmetrical blades will come into play.

Thoughts please?

[npomeroy]

Originally Posted by joel0407

I have been searching for the most efficient setup on my 450pro for about 18 months now. ...

By "efficient" to you mean to get the longest flight time? I.e. the least battery power output? I am sure others will be quick to tell you that there are trade-offs involved. What kind of flying do you do?

This could be a new thread.

Edit - It would be good, and in keeping with the intent of this sub-forum, if you could post some actual data you have so far: HS-Watts-flying weight-blade type. And I repeat, this thread was started to see if such an aerodynamics subforum could be created at all, and you post could get buried. A new thread on efficiency may draw more responses.

[sarpilot]

OK everyone seems to be awaiting a question to analyze. Here ya go, gravitational time dilation. I have spent close to 2 years of my life 24 hours a day going 300-500 mph. I look much younger than my friends of the same age. Was Einstein right and how can it be proven?

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[desertstalker]

Originally Posted by sarpilot

OK everyone seems to be awaiting a question to analyze. Here ya go, gravitational time dilation. I have spent close to 2 years of my life 24 hours a day going 300-500 mph. I look much younger than my friends of the same age. Was Einstein right and how can it be proven?

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Einstein was right, it has been proven.

Your example is not going to help. http://en.wikipedia.org/wiki/Time_di...ative_velocity see here for the simplest equations, your not going anywhere near fast enough for time dilation to have a significant effect. The delta is a function of 1 minus your velocity squared over the speed of light squared. Which to any reasonable number of significant figures is 1.

[Slyster]

Even space station astronauts going 15000 MPH for 6 months differ by like only .0001 seconds or some crazy small number. You need to be going pretty close to the speed of light for the effect to really be noticeable... like 500,000,000 MPH or more.

[sarpilot]

Originally Posted by Slyster

Even space station astronauts going 15000 MPH for 6 months differ by like only .0001 seconds or some crazy small number. You need to be going pretty close to the speed of light for the effect to really be noticeable... like 500,000,000 MPH or more.

Hey Sly…
Wow I would have thought it would be more than that at that speed. Guess you really gotta be trucking…


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[Slyster]

I looked it up and an astronaut aboard the space station for 6 months going 18000MPH will be 0.007 seconds younger than the people below.

At least it's measurable!

[TowPilot]

Originally Posted by sarpilot

Hey Sly…
Wow I would have thought it would be more than that at that speed. Guess you really gotta be trucking…


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Your risks are skin cancer and cataracts due to the higher UV allowed through at the altitudes you are sitting at

Loss of hearing also, due to the environment you are working in and around.

[sarpilot]

Originally Posted by TowPilot

Your risks are skin cancer and cataracts due to the higher UV allowed through at the altitudes you are sitting at

Loss of hearing also, due to the environment you are working in and around.

Hey Mike how ya been doin! You make it back from deployment ok I am guessing…

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[rdlohr]

Originally Posted by Slyster

I looked it up and an astronaut aboard the space station for 6 months going 18000MPH will be 0.007 seconds younger than the people below.

At least it's measurable!

I thought those astronauts were getting younger and younger ...

[Slyster]

Just for fun... calculator out... If two identical twins were born... and lived to 100 years old... and one lived all 100 years on the space station... when he landed.. and on their deathbeds... the astronaut twin would be 1.4 seconds younger than the other twin!

HAHA!

[sarpilot]

Originally Posted by Slyster

Just for fun... calculator out... If two identical twins were born... and lived to 100 years old... and one lived all 100 years on the space station... when he landed.. and on their deathbeds... the astronaut twin would be 1.4 seconds younger than the other twin!

HAHA!

Now that is funny

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[TowPilot]

Originally Posted by sarpilot

Hey Mike how ya been doin! You make it back from deployment ok I am guessing…

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Yes, sure did and doing fine

The laundry point was named after Gen Hal Moore with the history posted inside. Thought you would appreciate that.

Mike

[Azhar]

Good Day

I am conducting a trade-off study regarding the tailrotor position - the objective is to detrmine the most optimum position from a noise standpoint. In particular, I need to know the relative merits of placing the tail rotor within the plane of the main rotor (if any) and the gains associated with the conventional placement below the main rotor plane.

Could anyone kindly advise as to the various advantages/disadvantages of tail rotor position - with respect to the plane of the main rotor. Alternatively, if anyone has suggestions to suitable references that would be greatly apprciated.

Thank you in advance

[npomeroy]

Originally Posted by Azhar

Good Day

I am conducting a trade-off study regarding the tailrotor position - the objective is to detrmine the most optimum position from a noise standpoint. In particular, I need to know the relative merits of placing the tail rotor within the plane of the main rotor (if any) and the gains associated with the conventional placement below the main rotor plane.

Could anyone kindly advise as to the various advantages/disadvantages of tail rotor position - with respect to the plane of the main rotor. Alternatively, if anyone has suggestions to suitable references that would be greatly apprciated.

Thank you in advance

you may be better to start a new thread on this.

[extrapilot]

Azhar,

I don’t think you will find a lot of literature that applies well enough to draw conclusions for a small model. All published data I have seen applies to full scale machines, where a whole lot changes. For example, compare a UH60 with a TREX450. The TR tip speed on the UH60 is 2x higher, and the Re is about 30x higher. The downwash velocity for the UH60 is approx 6x higher in hover.

You would be far better off just buying a scale conversion kit, and doing acoustic tests that meet whatever criteria you are after (i.e. hover, or FFF, or inverted, etc).