VTX Rotorblades - Aero Engineering

[prototype3a]

Now I want to meet both of you.

I remember when Ryan was working on possibly making a 25mm version of the Logo SX counterbearing. I had just assumed he was a guy with some CAD skills and connections at a machine shop. I guess I was wrong.

[cbrkhan]

Welcome Bill… It’s awesome to see you here on HF

I am one of the fools who just bought a few VTX’ s and never bothered to go to VTX trials at IRCHA. So, I missed the chance to meet you in person. Hopefully next year

This thread is a amazing read and I am loving the insight that you are providing that go into blade design and build …. WOW that is a lot of work ..

Couple of questions

2200 max speed: New Logo 700 recommends 2200 so I am good there .. But I also planned to use VTX on my other birds where the planned head speed was 2250 and 2300. Should I just try and see how the +100 ish head speed work out or is it a big no no?


Tail Blades: My second question is without much knowledge of aerodynamics, mechanics or physics. Just a question out of pure curiosity. Any plans to make VTX tail blades asymmetrical? Even if the planned blades are not asymmetrical, was it ever a consideration? ….. If yes, what are the Pros and Cons of Symmetrical vs Asymmetrical blades in a RC heli application?

Thanks

[VTX Designs]

Originally Posted by zosek

Hey bill,



do you currently have plans for other size blades? Im especially interested in 600s and 630s.



Also, where can i find your distributors for eu?

Our planned sizes are 477 / 557 / 607 / 697 / 717

There most likely will be others to follow but I'm not in that decision making loop.

Prototype3a

You were one of our early adopters and have taken the time & effort to report back here on the forum. We can talk all we want about our own products but in the end it's unsolicited honest feedback such as yours that matters the most. Thank you for that!

[prototype3a]

I got burned several years back when I early adopted something in this hobby and so now I'm more cautious. But I got to see and hear Kyle Dahl fly the VTX in Fredericksburg and I immediately knew I had to have some. Also, everything about your design made sense based on what the aerospace engineering PHD students I work with were telling me.

For me, the next things on my list are a 3Digi, new batteries, VTX 557s and maybe a Logo700.

At work, I really want a Minicopter Diabolo or Triabolo to turn into a heavy lift/high endurance "drone" for extremely high resolution aerial imaging. I'm just on the fence if I should go with 3x 717 VTX or 2x 767 VTX... or maybe 3x 767.

[gator79]

Great thread Bill!

I can attest to what Ryan said about Bill and him being meticulous and very thorough. I too have known Bill for many, many years.

I don't really understand all the technical talk about the aerodynamics and design about the VTX blades, but I was amazed after my first flight on my Trex 700. The cyclic response was very fast. In fact, I lowered my cyclic agility on my vbar from 102 down to 96 and it was still fast. I also lowered my headspeed and I still get the same performance as before. I'm consistently landing with 10 to 20% more battery than before.

In high speed hurricanes, the blades track very predictably and I know right where I'm at with the machine.

I'm surprised with the extra lift during auto rotations. I live in Albuquerque at an elevation of 5,200' and I can notice a big difference in autos. In fact, my friends noticed it too. The blades just don't give up!

Bill, you and Ryan did an outstanding job with the blades!

Ryan, I hope to meet you sometime. Bill thinks very highly of you.

Scott

[mverhorst]

Hi Bill,

First of all let me say that I admire the work you put in these blades, a piece of art combined with top of the line function.

I was wondering if you where concidering the flap frequency of the blades, with all the heli's having a 90 degree fasing offset but non of them have a free tettering head.

Did you somehow incorperate the flap frequency and fasing issues in your designs?

Sorry for my English, not a native speaker...

Regards,

Menno

[RCpropo]

Hi there,
How do works VTX´s blades on autorotations?

[Johnny31297]

Originally Posted by RCpropo

Hi there,
How do works VTX´s blades on autorotations?

Excellent From my experience, they gain rpm quickly, hold it for a long time and the airflow stays attached at way higher angles of attack. In my case that means that I can float down at around +3-4° collective (depends on weight, airspeed, ambient temperature, air pressure etc..) where other blades would lose rpm and stall rather quickly

[VTX Designs]

Nice to see all this interest! Before I get in to composing answers to your questions, y'all might like to know that both myself and Ryan will be at the Abilene Chopper Madness event next week, along with the rest of the whole Mikado crew! This will be a rare opportunity to speak with both of us in person, and we'd be happy to talk about what ever you like there!

Originally Posted by cbrkhan

Welcome Bill… It’s awesome to see you here on HF

I am one of the fools who just bought a few VTX’ s and never bothered to go to VTX trials at IRCHA. So, I missed the chance to meet you in person. Hopefully next year

This thread is a amazing read and I am loving the insight that you are providing that go into blade design and build …. WOW that is a lot of work ..

Couple of questions

2200 max speed: New Logo 700 recommends 2200 so I am good there .. But I also planned to use VTX on my other birds where the planned head speed was 2250 and 2300. Should I just try and see how the +100 ish head speed work out or is it a big no no?

Tail Blades: My second question is without much knowledge of aerodynamics, mechanics or physics. Just a question out of pure curiosity. Any plans to make VTX tail blades asymmetrical? Even if the planned blades are not asymmetrical, was it ever a consideration? ….. If yes, what are the Pros and Cons of Symmetrical vs Asymmetrical blades in a RC heli application? ...

First off, thank you for supporting our product with your purchase. Very kind of you to offer such gracious remarks. Its perfectly fine to run VTX blades faster than our recommended speeds. Dynamic pressure will increase with the square of the head speed ratio which by itself is great. Just be aware that pushing into less efficient regions of the flight envelope isn't a free lunch. More head speed also causes your rotor disc to become a more rigid gyroscope. Gyroscopic angular precession rates are inversely tied to rotation speed - so double the rpm and for a given force on the disc it will precess at 1/2 of the original speed. Those are just basic physics. Pressing well past 0.45M or so also will exponentially reduce maximum operating AOA of the airfoil (running 2400 rpm will shave off 28% of that important parameter compared to what the airfoil will do in incompressible flow), and cause maximum sectional lift coefficient to also degrade in an approximate linear fashion with Mach (its non-linear if we hold Reynolds number fixed). Aerodynamic blade drag - composed of pressure drag and skin friction drag - will increase with the square of the velocity. Rotor blades make most of their drag on the outer 15% of the planform, which unfortunately also gives that drag the greatest physical couple to the center of the disc... so your ESC amps will jump up exponentially also. But, no, even given all this I still wouldn't call it a "big deal". Go ahead and experiment... have fun and please do report back here!

Tail blades: still in the design phase. Everything is on the table here. I don't carry any preconceived notions into this design effort and trust me we don't copy and paste anything. Its all open for discussion, but "in-house" at this time only. Cheers...

Menno - Howdy from the USA! Thank you for the kind words. Your English is much better than my Dutch!! To answer your question, no we did not consider flapping dynamics on these blades due to our completely rigid rotor system. We did stiffness testing in a static test jig, and measured deflection across the blade span. VTX blades are extremely stiff - we measured a 35% decrease in tip deflection compared with a baseline blade - the Edge693SE. This added stiffness is due to our blades having such a high cross sectional moment of inertia. The inboard blade section on VTX blades incorporate what I call "structural" airfoils because they're chosen in large measure for their inherently high MOI.

- Bill

[VTX Designs]

Originally Posted by prototype3a

(snip) ... Also, everything about your design made sense based on what the aerospace engineering PHD students I work with were telling me. (snip) ...

Yes sir!!

(emphasis in quotation mine)

- Bill

[mverhorst]

Originally Posted by VTX Designs

Menno - Howdy from the USA! Thank you for the kind words. Your English is much better than my Dutch!! To answer your question, no we did not consider flapping dynamics on these blades due to our completely rigid rotor system. We did stiffness testing in a static test jig, and measured deflection across the blade span. VTX blades are extremely stiff - we measured a 35% decrease in tip deflection compared with a baseline blade - the Edge693SE. This added stiffness is due to our blades having such a high cross sectional moment of inertia. The inboard blade section on VTX blades incorporate what I call "structural" airfoils because they're chosen in large measure for their inherently high MOI.

- Bill

Hi Bill,

Thanks for that... As you mentioned, our rotorsystems are rigid more or less, hingeless. (There is a lead/lag hinge at the bolt but that is mosly cranked down quite hard).

With the rotorsystem being rigid it are the blades doing all the flapping during cyclic input. Being the blades that incorperate the flap hinge, this hinge is offset from the center of the disc causing a different fase lag then the 90 degrees that we have mechanically on our heads.

But anyway, thanks for clearing that up, from the picture i've seen it looked like there was a part of the inboard section which is quite narrow and I thought it might have samething to do with getting the flap frequency closer to 1 (90 degrees).

Regards,

Menno

[VTX Designs]

Menno - you are 100% correct. I should not have said "completely rigid" - in fact there is deflection in the blades and the head dampers allow for a degree of motion in the spindle shaft. Therefore blade flap does happen (hinge due to blade flex) and can lag in the blade grip bolt. To date, we have not done any real world testing to measure blade flap (deflection) or the effect it has on phase angle on VTX blades. I know its there, but we've not considered those second-order effects in our analyses. I also think the FBL is doing enough of the "driving" that the pilot never even knows there are phase lag issues on the heli - they're not tuned out mechanically in the head anywhere like they probably would be on full size machines.

In our blade design process, the primary aim of the effort was to vastly improve blade aerodynamics. That's my forte' as an aerodynamicist... I'm not a rotary wing engineer (but I'm getting a good feel for it )

Thanks!

[lucasouthoffrance]

Originally Posted by VTX Designs

Our planned sizes are 477 / 557 / 607 / 697 / 717

There most likely will be others to follow but I'm not in that decision making loop.

Hi, and thanks for this interesting thread.
Any chance to see shortly a 500 size blade (500...520) for the "best seller" Goblin 500 ? Since the heli is very popular...releasing the corresponding VTX blades sounds like obvious, right?
Cheers, Luca

[RyanW]

I figure I will add part II of the history.

I left off mentioning how things got started.

In addition to finding the best person for the task, you also need to know your own expertise and know how far you can stretch yourself and those around you. If you happen to be in a situation where you have the right ingredients, sometimes you need to just sit back, shut up and listen. Thank the Lord I had the awareness to do this!

I have learned so much during the development of these blades. I have learned how intuition can be 180 degrees out of phase to reality when it comes to aerodynamics. I have learned that you can push the boundaries, but in a very controlled manner. Thank you Bill for showing me where to push

I am very proud that we ended up with an elegant blade despite the fact that one of our unwavering pillars of development is form truly follows function. The design must be aero-data driven. No exceptions.
This definitely stretched me!

I am also very thankful to the VTX principals for allowing us the flexibility to develop it they way it needed to be. I really appreciated the approach they took to market. No hype, let the blades speak for themselves. To borrow one of my favorite lines from Audi- "Truth in engineering"

Hope everyone enjoys!

[mverhorst]

Originally Posted by VTX Designs

Menno - you are 100% correct. I should not have said "completely rigid" - in fact there is deflection in the blades and the head dampers allow for a degree of motion in the spindle shaft. Therefore blade flap does happen (hinge due to blade flex) and can lag in the blade grip bolt. To date, we have not done any real world testing to measure blade flap (deflection) or the effect it has on phase angle on VTX blades. I know its there, but we've not considered those second-order effects in our analyses. I also think the FBL is doing enough of the "driving" that the pilot never even knows there are phase lag issues on the heli - they're not tuned out mechanically in the head anywhere like they probably would be on full size machines.

In our blade design process, the primary aim of the effort was to vastly improve blade aerodynamics. That's my forte' as an aerodynamicist... I'm not a rotary wing engineer (but I'm getting a good feel for it )

Thanks!

Nice wright-up sir... Great to see someone with these skills and knowlage take effort in our hobby...

I am an engineer myself and love the technical side of the hobby to. Still trying to understand how these amazing machines really work and doing as much reading as I can handle, and lets not forget Extrapilot... He has some great knowlage in rotor dynamics and I sure hope he finds this thread and gives some extra insights.

Thank you again for taking your time to talk to us and showing us why your blades are the way the are...

Keep it up!

[RGorham]

Bill,

Thank you for putting so much time and effort into designing this revolutionary airfoil for the hobby industry.

Three questions;

•What is the maximum allowable head speed that these blades are designed to withstand?

•Are you using lead at the outer tip of the rotor blade and if so are you using a safety wire that connects to the root?

Thanks,

Rg

[apper001]

Why did it take so long for a Manufacturer to start advancing in rotor blade design?

[Johnny31297]

Originally Posted by RGorham

•What is the maximum allowable head speed that these blades are designed to withstand?

•Are you using lead at the outer tip of the rotor blade and if so are you using a safety wire that connects to the root?

Both questions should be answered with this: https://www.helifreak.com/showpost.p...1&postcount=22 and following posts.

Yes, the blades contain lead to get weight and CG to match the required values. Furthermore, Fun-Key won't even build blades without a wire retaining the lead, you can see it being anchored in the root with a zig-zag pattern in the picture i posted in the post linked above.

[RGorham]

Excellent, thank you. I had to try a set on my X7.

I'll do my best to promote these rotor blades, excellent design, quality & flight performance.




Have a great day!

[MS60]

Excellent, thank you.

I'll do my best to promote these rotor blades, excellent design, quality & flight performance.


If this guy likes them ^^ I'm in!