DIY: 4G6 Crash Proofing and Performance Enhancing mods! Updated 27July2010

[timewerx]

Originally Posted by Intact

Ahh! I understand! To achieve something, you have to sacrifice other things. Its just a matter of getting enough of what we need and the most of whats better!

Highly efficient non-3d blades sounds like the recipe for trainers tho! I I just imagine them to be like real helicopters that cant sustain inverted flight for too long or not at all!

What your working on sounds like they're gonna be good! Even better on your lightweight model with the longer blades, huh? Disc loading was it? I think i wanna do weight reducts soon.

If I'm very lucky, performance will be better than stock blades. Otherwise, just forget my blade mods and use them only as trainer blades.

My current paper blade ended up only very slightly longer than stock so any performance differences in that matter is almost negligible. The blade however is slightly wider and thicker. From the lessons I've learned, I'm trying to increase the Reynold's number of the blade(by making the blade wider or you can also increase headspeed...) to try to improve performance.

It's quite interesting working with Xfoil airfoil designer. I've seen for myself that the Walkera airfoil simulated in the software churned out some really good numbers consistent with real life performance. So hopefully, the airfoil I designed with it performs as in real life! Anyway, if the airfoil is Walkera's original design, then kudos to them It's well optimized for the Reynolds number it's running!

[timewerx]

Getting close!

Less efficient than stock blades, still got 6:48 mins flight time though. Little bogging and stability was better than stock Felt like flying a different heli like the trex 250 I fly in the sim.

Too draggy probably due to higher thickness than stock. I thought higher thickness would result to higher lift as predicted by Xfoil. I think we need a compromise again... The rotor experiences different airspeeds, thus different Reynold's number. A thinner airfoil would be more effective at low Reynolds near the root so I'm reducing thickness now...

Notice the canopy, I copied the livery from N5 Synergy. I realized the shape of the canopy of the N5 looks similar to my paper canopy

[hjns]

you may want to experiment with different thicknesses along the cf rod. I.e., thin near the root and thick near the tip.

[timewerx]

Thought of it before but would be complicated to give the graphite core varying thickness.

There's a simpler way I found of achieving the same effect without varying the thickness. A certain manufacturer (forgot the name) puts a turbulator near the root of their blades. The turbulator will help alleviate the poor aerodynamic performance at low Reynolds number. The turbulator can simply be a clear tape placed near the leading edge and near the blade root.

[Intact]

Oh, they look much fuller and set forwaward now. What is walkera's airfoil like, why is it special?

The most attractive part of your blades are that you can produce them yourself and they will take abuse! I'd sacrifice performance for that already. But ofcourse i would prefer not to.




Your canopy looks awesome! Orange and blue contrast very well. Thats why i use an orange color scheme. You can see it against the sky's blue.

I thought it was a bottle of elmer's glue from the corner of my eye at first haha. It has the same colors as the logo.



I have a random question about some aerodynamics... I was at the beach and was observing sail boats! What if part of the rotor blade were soft or softer like a sail like the trailing edge? How would that affect the airfoil? Would it have a changing effect as pitch of the blades change, like having a directional changing airfoil? Would you be able to use that to your advantage in this application?


They're applying airfoils to sails, i was just wondering what if u did it backwards.

[hjns]

Hi Intact,

I like your idea. A possible solution might be something like a tight symmetrical frame with a paper "sail" attached to that that takes the form of an airfoil to the upper side whichever side is up.

[timewerx]

Nope, flexibility not good. I tried using 120 GSM paper as blade material before, resulted to inferior throttle response and lift. 200 GSM seems to be the best blade paper... But resulted to higher crash damage

Using some flexibility to cause the blade's airfoil to curve like in a sail is not good either. The Reynold's number of the CP blades is too high for curved airfoils to be efficient.

Just crashed the my latest paper blades that is shaped like stock for the first time. Damage is worse than if I had crashed with V7. The damage on the blade itself is bad enough that repairing it may not be advisable.

Thinking of returning back to V7 blade geometry and just simply improve it! Perhaps incorporate some of the things I learned in my latest project, especially the use of turbulators and using thicker airfoil. Development may be delayed, my b/w HP laser printer broke! Have to buy a new one, it's pretty old anyway @13 years old! I'll just fly with stock blades for now

[timewerx]

I love my new canopy colors, lets me see my 4G6 way easier even in dim lighting

I'm actually using florescent orange and it will glow brightly in UV light! It's a hand painted canopy and I used felt tip pen and markers for that!

[Intact]

Originally Posted by timewerx

I love my new canopy colors, lets me see my 4G6 way easier even in dim lighting

I'm actually using florescent orange and it will glow brightly in UV light! It's a hand painted canopy and I used felt tip pen and markers for that!

Flourescent orange from highlighters ! Thats what i use too! I just color thicker so its a darker orange. It keeps its flourescence still but with a more natural orange color. I only chose the color for functionality. The inverted color of blue(sky) is yellow or orange and it grew onto me after i saw the blades spin an orange glowy disc on the tip.

I want to try to make a paper canopy so i can color it myself too. Need to somehow make if easier to differentiate the tail from the nose so i can practice nose in more.. maybe ill make a pair of fluorescent green tail blades..



oh well for the sail designed rotor blades, nature just doesnt like our micro flyers much

[timewerx]

Originally Posted by Intact

Flourescent orange from highlighters ! Thats what i use too! I just color thicker so its a darker orange. It keeps its flourescence still but with a more natural orange color. I only chose the color for functionality. The inverted color of blue(sky) is yellow or orange and it grew onto me after i saw the blades spin an orange glowy disc on the tip.

I want to try to make a paper canopy so i can color it myself too. Need to somehow make if easier to differentiate the tail from the nose so i can practice nose in more.. maybe ill make a pair of fluorescent green tail blades..

oh well for the sail designed rotor blades, nature just doesnt like our micro flyers much

Bees goes to mind Nice quote from Mary Kay Ash:

Aerodynamically, the bumble bee shouldn't be able to fly, but the bumble bee doesn't know it so it goes on flying anyway.

Bad thing with using florescent colors, you're quite limited to hand/manual painting which can be laborious so I keep the artwork simple or simply functional. There are no florescent printer inks as of yet!

[timewerx]

We're getting real close to releasing V8 blades!

I'm terminating all attempts to duplicating stock blades on paper despite having higher performance. The stock-looking blade is heavy and does not do well in crashes. However, the blade below is only 2 grams!!

I'm reverting the design back to Rev B with a turbulator. Turbulators are quite effective actually and delivers performance comparable to stock blades at the price of less blade efficiency at neutral/hovering pitch.

Anyway, V8 blades may be easier to make. I did a number of revisions to the process. For example, preparing the stock blade now no longer requires cutting off the tip and the grinding part has been removed too. Replacement will also be faster and less messy so stay tuned!

[Intact]

Its only normal that efficiency is lost for performance. How are flight characteristics VS v7 and VS stock?


is the leading edge going to be forward set like your last blades that was similar to stock?


Also, last question, what if i ran out of glue in the process of making them. Would they still be usable without the turbulator until i got glue?


I think i might need that motor upgrade soon..

[timewerx]

Vs stock, less punchy on the throttle but dramatically faster on the cyclics. Vs V7, punchier and faster on the cyclics. The new one will be forward set so you can use lighter weight paper like 160 GSM to improve crash protection. It also resulted to faster cyclics.

The one in the picture did not have a turbulator yet. I'm trying to evaluate performance without it first because turbulators add to drag. I did not use glue to make turbulator. I simply used ball point pen to make the zig zag impressions on the blade. The pattern will be on the template so the turbulator should be incredibly easy to make!

Making another blade with a turbulator this time. It failed the first time, too much drag, probably caused by too much thickness.

[timewerx]

Thinking of studying the V7 blades...:o

Getting quite disappointed of my V8 attempts. It's turning out V8 without the back slant is either less efficient or less punchy than V7.

I originally intended the V7's back slant to improve stability. Didn't realize, it may be improving performance too at these micro sizes. I may eventually just improve V7 and name it V7X.

[JossyRC]

I think your V7`s would be good if the chord length at the last thrid was not reduced less than the stock chord length and if the sweep on the end wasn`t tapered down to a point. Anything poking out past is sort of wasted....

so this is my logic (if you would call it that). The washout isn`t quite as important as we might think because IMHO there really isn`t any lift generated in the first half of the blade length so the tips will not stall before the roots - so rather then decreaseing chord length to even out lift across the span - increase the chord at the root to aid in cyclic response. Reducing the chord at the tip will reduce the lift where it is really only being generated. By not tapering the sweep the chord length across the swept portion is actually increaseing chord length (because airflow is now on an agle to the swept leading edge - like cutting a cucumber on an angle - it looks like a fishing lure). ... but I`m not sure if this is a good idea becuase this would move the center of lift or the biase backward maybe too far - any way attached is a 2 second modification I just drew up for a visual.

[timewerx]

Nice looking blade Jossy!

Those are valid points you mentioned. It will work well with a proper airfoil. Airfoils usually work better with higher Reynolds number and increasing chord will increase it too!

Pointy tips are not bad actually. If you reduce lift towards the tips and increase towards the roots, tip vortices and induced drag is reduced. While it's true that they cause drag at neutral pitch but when the rotor starts producing lift, they cause less drag overall.

[JossyRC]

Are swept tips nessesary?

[timewerx]

For some reasons unexplainable, the swept tips improves performance.

Oh and another thing, I've also verified/tested today that turbulators does not improve performance in a useful manner.

I have come up with a radical solution that works with dramatic results in static testing though. Now if it works in rotor blades, let's find out! Can't say what it is yet.

[timewerx]

The V8 blade is about done! Just awaiting the usual 7+ minutes endurance testing

It ended up looking similar to V7 but with a way smaller swept back tip. So far, flying around, draining batteries to storage charge gave higher performance than V7. But the biggest improvement in V8 is it's going to be easier to make than V7! I streamlined the process and removed some of the steps that is not really that important based on experience.

[729927852]

So how exactly does the tail clutch mod work?