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

[timewerx]

Sent you the mod now Henk. Hope you get better results with it than simply cutting foamies.

Regarding the main shaft, I won't be developing the case hardening mod anymore. I discovered the new main shaft I'm using was slightly off spec. It had very slightly less thickness and a deeper notch than the factory stock - both which made the shaft bend easily in my first major crash with the new main shaft installed(My first major crash after one month flying actually!). Case hardening won't solve the problem, because the problem was being off spec in the first place.

After the first major crash of the season, I'm back to using the old factory stock main shaft which I've repaired so many times... I'm also happy to report the mods held like it always had. The only replaced item was the main shaft and the paper shear pin. The paper blades were repaired with glue and everything was back to vibration free performance in no time. It's also interesting to note that the new stock CNC head block remained undamaged after the crash, no twisting nor any deformation of any kind. Apparently, with the lightweight V7 blades, paper shear pin, and lightweight paper paddles, it will reliably escape damage! I am currently using a stock CNC head block because I found it to distort less during flight so giving less vibration and generally higher precision compared to the plastic head block.

What caused the crash was I flew too late in the afternoon in the garage and didn't bother to turn on the lights! Does anyone know when you're flying in dimly-lit place and without night lights, things seem to happen a lot faster?? I hit the sharp corner of the concrete wall buttress. It's no different than hitting a solid metal pole if you know what I'm talking about Would cause major damage to a bone stock 4G6!

[hjns]

Thanks Mark,

I will start working on it in 2 weeks, due to an international congress.

[Intact]

Originally Posted by timewerx

Sent you the mod now Henk. Hope you get better results with it than simply cutting foamies.

Regarding the main shaft, I won't be developing the case hardening mod anymore. I discovered the new main shaft I'm using was slightly off spec. It had very slightly less thickness and a deeper notch than the factory stock - both which made the shaft bend easily in my first major crash with the new main shaft installed(My first major crash after one month flying actually!). Case hardening won't solve the problem, because the problem was being off spec in the first place.

After the first major crash of the season, I'm back to using the old factory stock main shaft which I've repaired so many times... I'm also happy to report the mods held like it always had. The only replaced item was the main shaft and the paper shear pin. The paper blades were repaired with glue and everything was back to vibration free performance in no time. It's also interesting to note that the new stock CNC head block remained undamaged after the crash, no twisting nor any deformation of any kind. Apparently, with the lightweight V7 blades, paper shear pin, and lightweight paper paddles, it will reliably escape damage! I am currently using a stock CNC head block because I found it to distort less during flight so giving less vibration and generally higher precision compared to the plastic head block.

What caused the crash was I flew too late in the afternoon in the garage and didn't bother to turn on the lights! Does anyone know when you're flying in dimly-lit place and without night lights, things seem to happen a lot faster?? I hit the sharp corner of the concrete wall buttress. It's no different than hitting a solid metal pole if you know what I'm talking about Would cause major damage to a bone stock 4G6!

I thought I just had a defective main shaft last night and apparently theres more than just mine! I was observing a very slight vibration at low rpms and was wondering what was up. everything was straight and balanced. When i checked the head, it wiggled on the main shaft even with the pin in place, you could also twist it about 1 degree back and forth. It was like the mainshaft shrunk?? I have 2 shafts like this. I replaced it with one of my many stock shafts that i bend back too for now... Im waiting on the new procrasher shafts.

[timewerx]

The factory stock main shaft on a bone stock 4G6 lasted me good 10 major crashes involving a full blown blade strike before bending eventually.

I've also noticed the factory main shaft wore better. Looks like Walkera parts can be great if done with adequate quality control. Btw, that was 6 months ago!

[timewerx]

I'll be having a bit of time this weekend and I may have an opportunity to try to improve the V7 blades.

If successful, the new blade will be called the 'V7 HLE3D' blades (HL stands for 'High Lift' and E3D for 'Extreme 3D' and may give you a clue at what I'm trying to achieve) and should result in significantly increased sustained thrust output both in positive and negative pitch.

The design may slightly reduce hovering and FFF efficiency but will improve efficiency, performance, and stability in any aggressive flying. Hopefully, will give the most spectacular throttle punch you've ever seen in the 1S 4G6!

[timewerx]

I was able to retrofit the V7 blades into V7 HLE3D today and tested. I basically put micro vortex generators of my own design(classified! ) and aerodynamic fences in the V7 blades. Same equipment you'll find in STOL aircraft...

The good news is, it made the V7 blades COMPLETELY stall proof, thus making it a lot easier to throw in aggressive maneuvers. Bad news is the high lift equipment created a lot of drag that took a significant amount of power from the motor. So the change is not good for now.

Another good news is we have a new blade! I had just enough time left to develop the Mark VIII (V8) blades. It took two trials with two different blades. The first test blade looked quite similar to the V7 blades and produced less lift. The second one is a surprise, the new naming standard is the clue to what it looks like! It outperformed the V7 blades by a good margin and is also way more silent.

[Intact]

Originally Posted by timewerx

I was able to retrofit the V7 blades into V7 HLE3D today and tested. I basically put micro vortex generators of my own design(classified! ) and aerodynamic fences in the V7 blades. Same equipment you'll find in STOL aircraft...

The good news is, it made the V7 blades COMPLETELY stall proof, thus making it a lot easier to throw in aggressive maneuvers. Bad news is the high lift equipment created a lot of drag that took a significant amount of power from the motor. So the change is not good for now.

Another good news is we have a new blade! I had just enough time left to develop the Mark VIII (V8) blades. It took two trials with two different blades. The first test blade looked quite similar to the V7 blades and produced less lift. The second one is a surprise, the new naming standard is the clue to what it looks like! It outperformed the V7 blades by a good margin and is also way more silent.

Glad to hear great news! LOL at VG for this scale! Maybe they'll work better with stock blades if you can apply it to them? haha !


Are the graphite shafts still the same for the new blades? Im excited to see and try them.



I have a pair of slightly broken novus cp blades (orange) that im excited to mod cause they match my color scheme really nicely !


Teasers please

[timewerx]

The Mark VIII naming is due to the blade's similarity in the Supermarine Spitfire wing Spitfire versions are identified through Mark #'s. The higher the marks, the higher the version and is typically more advanced. May release the blade next weekend after few more modifications to the design I'm anxious to try next weekend too.

The new blade is constructed in the same manner as the V7 blades so no need to worry re learning the procedure again. You can use the V7 manual to make the new blade as I'll be releasing only the template

[edit] Upon release of this blade, the V7 will still remain available. The V8 is slated to become a performance oriented, crash proofing blade but still giving 7+ mins flight times. It will be dramatically punchier than V7 blades for the same pitch setting. So if you can't handle the performance yet, you can always go back to V7.

[Intact]

Originally Posted by timewerx

The Mark VIII naming is due to the blade's similarity in the Supermarine Spitfire wing Spitfire versions are identified through Mark #'s. The higher the marks, the higher the version and is typically more advanced. May release the blade next weekend after few more modifications to the design I'm anxious to try next weekend too.

The new blade is constructed in the same manner as the V7 blades so no need to worry re learning the procedure again. You can use the V7 manual to make the new blade as I'll be releasing only the template

[edit] Upon release of this blade, the V7 will still remain available. The V8 is slated to become a performance oriented, crash proofing blade but still giving 7+ mins flight times. It will be dramatically punchier than V7 blades for the same pitch setting. So if you can't handle the performance yet, you can always go back to V7.

Great! They remind me of tapered blades. I'm imagining a more eliptical shape when its working on the rotor with the displaced cog?


Can the stock in-runner run it?

[timewerx]

Yes, the stock inrunner should run it. My rule of thumb is if I could fly it 7+ minutes with the HP08-2, the stock inrunner will be able to run it. But I usually back off some pitch when using the inrunner. The current pitch I use +15 -15 degrees is too high for the stock inrunner even if you're using the stock blades.

I used a semi-circle taper. Revision B looks very similar with less taper.

Theoretically, my current V8 blades should deliver the highest performance compared to all my other blade mods. I've known the principle very early in my blade modding(my V1 blade is quite similar to V8 blade) but did not proceed further with the design due to severe fluttering issues. Fluttering issues was only completely solved in my V7 blades so I decided to try the 'old' design again.

Look how similar my early V1 blade is to the V8. On the other hand the V2 is closer to V7 and had the swept back tip to reduce fluttering. The V8 blade did not have the fluttering issue even without the swept back tip.

[timewerx]

This is the V8 Rev C.

Featured thicker airfoil and a turbulator. The turbulator is the zig zag feature near the leading edge to improve lift at high pitch/reduce Laminar Separation Bubble.

New design resulted to very good stability at high alpha maneuvers (makes it excellent for 3D flying) and excellent performance/stability at high pitch. Unfortunately, I may have overdone the turbulator or the airfoil thickness. Created too much drag at low pitch so headspeed is reduced and flight time reduced as well from 7:10 minutes of Rev B.

Rev D should have slightly thinner airfoil with less protruding turbulator and possibly limiting the turbulators to the outer half of the blade only.

[JossyRC]

Originally Posted by timewerx

The Mark VIII naming is due to the blade's similarity in the Supermarine Spitfire wing Spitfire versions are identified through Mark #'s. The higher the marks, the higher the version and is typically more advanced. May release the blade next weekend after few more modifications to the design I'm anxious to try next weekend too.

The new blade is constructed in the same manner as the V7 blades so no need to worry re learning the procedure again. You can use the V7 manual to make the new blade as I'll be releasing only the template

[edit] Upon release of this blade, the V7 will still remain available. The V8 is slated to become a performance oriented, crash proofing blade but still giving 7+ mins flight times. It will be dramatically punchier than V7 blades for the same pitch setting. So if you can't handle the performance yet, you can always go back to V7.

Looks allot like the fixed pitch blade shape.

[timewerx]

Yes it does! I'm trying to emulate FP lift distribution because FP blades are generally more efficient than CP blades. In our case, we have to emulate the lift distribution in inverted flying too!

V8 Rev D is done and spent a short time flying with it (to discharge the LiPos to storage capacity). Rev D outperformed V7 in high performance flying in all respects! Even bogging was less for the same lift generated. Tomorrow it will be tested further for endurance and against the stock blades as well. If it surpasses lift of stock blades and have at least 7 minutes endurance, Rev D will be declared final!

Had a crash too, flying in dim lights in the garage, recovered too late from a negative pitch to the ground. My 4G6 bounced from the ground into the faucet at full throttle. Damage was only dented blade tips which was easily fixed and had to replace the shear pin. Apparently, V8 blades seemed to offer better crash protection too. No bent shafts and no popped links!

[timewerx]

Having no luck yet. And I'm ending up studying the stock blade airfoil.

Surprisingly, the stock airfoil gave a maximum lift coefficient @ 8 degrees pitch(software analysis using Xfoil). Not really a sign of bad design. In fact, it's very good! The bad in fact is it maybe pointless to use high pitch setting. Real life testing revealed that backing off the pitch range to lower values from 15 degrees did not reduce instantaneous acceleration. So you get similar high performance but without bogging and losing tail hold!

Might test stock blades at lower pitch ranges later. I've also managed to design a new airfoil that's driven mainly by ease of fabrication and surprisingly yeilded higher lift coefficient and a lower drag penalty and also at 8 degrees - virtually speaking. Testing soon.

[hjns]

Originally Posted by timewerx

Having no luck yet. And I'm ending up studying the stock blade airfoil.

Surprisingly, the stock airfoil gave a maximum lift coefficient @ 8 degrees pitch(software analysis using Xfoil). Not really a sign of bad design. In fact, it's very good! The bad in fact is it maybe pointless to use high pitch setting. Real life testing revealed that backing off the pitch range to lower values from 15 degrees did not reduce instantaneous acceleration. So you get similar high performance but without bogging and losing tail hold!

Might test stock blades at lower pitch ranges later. I've also managed to design a new airfoil that's driven mainly by ease of fabrication and surprisingly yeilded higher lift coefficient and a lower drag penalty and also at 8 degrees - virtually speaking. Testing soon.

Hi Mark,

I am not so surprised, because with my 95 mm "stock" foamies I still have some nice flying results..... Am still looking forwards to your new creations, though!!!

[timewerx]

Honestly, the stock blade lift is hard to beat!! I may have beaten the efficiency previously - only by a slim margin. But if we're talking of 3D, and don't mind trashing the one-use stock blades, you might as well use the stock blades over my blade mods!

The only thing I have gained a comfortable lead over Walkera is the tail blade. The stock blade btw, + 70 gram 4G6 is quite an insane combo! I kept loosing sight of my 4G6 because it's accelerating so fast! I just can't fly with it all the time, too scared of trashing the stock blades so I'm still trying my best to to acquire stock blade performance on the paper blades!

I may grab a video of my 4G6 flying with the stock blades for the kicks, it's insane!

[Intact]

Originally Posted by timewerx

Honestly, the stock blade lift is hard to beat!! I may have beaten the efficiency previously - only by a slim margin. But if we're talking of 3D, and don't mind trashing the one-use stock blades, you might as well use the stock blades over my blade mods!

The only thing I have gained a comfortable lead over Walkera is the tail blade. The stock blade btw, + 70 gram 4G6 is quite an insane combo! I kept loosing sight of my 4G6 because it's accelerating so fast! I just can't fly with it all the time, too scared of trashing the stock blades so I'm still trying my best to to acquire stock blade performance on the paper blades!

I may grab a video of my 4G6 flying with the stock blades for the kicks, it's insane!

I was gonna say that i like the aggressive lift response i got from the stock blades now.

They dont have the stability of the v7 which was what i was looking for before. The v7 seemed to direct airflow under it at an angle outward at lower pitch which made it correct itself? I think this is what made it feel sluggish, but it gave me time to react and save!

Is that because the leading edge is displaced back on the graphite core compared to stock or is it the v7's shape? or both?


I could tell the difference between the stock and v7 better when the packs were getting lower. I could drain the batteries till the voltage cutoff while still hovering with stock blades, that put my batterries way low at 3.45 when the rx cutoff. The v7 would lose power to hover past ground effect when my packs were at 3.75-3.8v. Which explains my floating down when the packs were getting lower. I find this as a good failsafe tho for beginners.

And they do prevent overdraining my batteries.



I was beginning to feel like my in-runner motor didnt have enough torque with the V7, but the stock didnt have this issue. I was gonna ask for stock blade performance but more efficient (lighter, cheaper etc) as i dont mind the stability anymore. I like the ease of using paper. Its just awesome. Kind of feel like 1st grade when making em! And foam esplodes.

I use the v7 indoor and stock outdoor ! No furniture to explode your stock blades outdoors just the ground! And the v7 made it tame enough for roaming inside the house and under tables.



And i agree, the tail blades most definitely outperform stock. I havent had a problem with tail hold since. I found that the wagging i got with the tail blades without the airfoil was actually from a servo. The LR airfoil did fix it tho even with the servo issue and allows me to use a wider tail pitch range without the wagging.. Faster piros!




Oh yeah, i have a question. If i put holes in the paper and coverd them with tape, would that make the v7 blades lighter? And when are we gonna see dogtooth or fence designs?!

[timewerx]

Now you're talking! Yes, you can treat the V7 blades as trainer blades so I won't be removing it from my mods page Let's just say I have demoted it to trainer level! for the upcoming higher performance variant that's taking too long to develop!

I've tried fence before but too much drag. Improved handling though. Dogtooth is too complicated and may cause too much drag as I've experienced with turbulators.

Eventually, I may duplicate the stock blades on paper using an airfoil with higher max lift coefficient. I'll have to ditch the taper so we can have high performance without getting too complicated. Just be prepared for a more complicated process to build it! But if I manage to beat the stock blade's performance, it will be well worth it, as you'll get a high performance blade that can be repaired.

I'm also starting to conclude that the foam blades has been optimized for the original Walkera 4G3 which weighs only 68.4 grams AUW. As I was studyng the blades, it only takes very little to take the carefully engineered blades beyond its design parameters. True enough trying it on my 4G6 which weighs almost like a 4G3 (71 grams AUW with stock blades). Performance was dramatically better than bone stock even if running at a slightly lower head speed than bone stock!

A bit of something good, plankers at rcgroups seem to be having good results with Xfoil freeware. Hope it would do the same for heli rotor blades!

[timewerx]

Good news, I'm getting close to figuring out a method to create a proper airfoil shape with paper and the graphite core.

Eventually, the V8 blade will look exactly like the stock blades, perhaps, a little bit longer... Not sure if it's still worthy of being called 'V8'. Let's just call it 'High Performance Crash-friendly Blades'!

I've learned a lot from this project. I've realized my tail blades project worked wonderfully in the low Reynolds number conditions (narrow width and lower speed). But the main blades run in a high enough Reynolds number that made many of the design principles I used with tail blades not the best to use with main blades.

The best method to actually improve efficiency in a CP blade is use blade twist and use asymmetric airfoil. Unfortunately, both would render the heli incapable of hard 3D moves so typical CP Blade designs are actually a compromise. We really can't make highly efficient CP blades unless you don't plan on flying 3D.

[Intact]

Originally Posted by timewerx

Good news, I'm getting close to figuring out a method to create a proper airfoil shape with paper and the graphite core.

Eventually, the V8 blade will look exactly like the stock blades, perhaps, a little bit longer... Not sure if it's still worthy of being called 'V8'. Let's just call it 'High Performance Crash-friendly Blades'!

I've learned a lot from this project. I've realized my tail blades project worked wonderfully in the low Reynolds number conditions (narrow width and lower speed). But the main blades run in a high enough Reynolds number that made many of the design principles I used with tail blades not the best to use with main blades.

The best method to actually improve efficiency in a CP blade is use blade twist and use asymmetric airfoil. Unfortunately, both would render the heli incapable of hard 3D moves so typical CP Blade designs are actually a compromise. We really can't make highly efficient CP blades unless you don't plan on flying 3D.

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.