Low headspeed stability for scale flying

[Hank79]

Hi guys. Does anyone have any experience with flying there 500 at 1000-1300rpm? And if so how does it fly. I have sold my 500 but will buy a new one to put into the new Align Super Cobra fuselage and I don't want it reving it's guts out.
I am planning to put a scorpion 880kv engine with a 12 pinion in it to bring the rpm down with it governed for 1100-1200 rpm. I will be using a vbar stability system.
Due to the head being a rigid design with little dampening for low rpm I am worried it might get the slow head speed wobbles.
Is the head speed I'm chancing a bad idea?

[dannylightning]

Originally Posted by Hank79

Hi guys. Does anyone have any experience with flying there 500 at 1000-1300rpm? And if so how does it fly. I have sold my 500 but will buy a new one to put into the new Align Super Cobra fuselage and I don't want it reving it's guts out.
I am planning to put a scorpion 880kv engine with a 12 pinion in it to bring the rpm down with it governed for 1100-1200 rpm. I will be using a vbar stability system.
Due to the head being a rigid design with little dampening for low rpm I am worried it might get the slow head speed wobbles.
Is the head speed I'm chancing a bad idea?

1300 rpm.. i dont think it would even lift off the ground..

[Anthony440]

I agree, I don't think it would lift off. 2000 rpm would be pushing it, IMO. Maybe if it was a 90 sized you could get the rpm somewhere close but it would nod due to the low HS.

[Hank79]

I thought it would be proportional to the heli. I have seen 90 size heli fly quite well with under 1000rpm. So I thought a 500 could do the same since it is a lighter heli and the lift to weight ratio would be similar to a 700e for example.

[Anthony440]

I don't know the physics of disc loading but it's not proportional to size. I do know the smaller you go, the faster the head speed needed.

[dannylightning]

Originally Posted by Hank79

I thought it would be proportional to the heli. I have seen 90 size heli fly quite well with under 1000rpm. So I thought a 500 could do the same since it is a lighter heli and the lift to weight ratio would be similar to a 700e for example.

the longer the blades the less rpm you need to create lift, a 700 is monstrous compared to a 500 i would guess you would need at least 1800-2000 rpm might do the trick but i have my doubts. 2200 might be the bare minimum to make a 500 fly half way descent if you dont pan on doing any thing but flying around in a cew circles .

[SidewaysLS4]

I think you will be looking at 1700 as the bare minimum headspeed for a scaler T500. Below this the lift becomes very marginal on 2 blades. Here's a T500 AS350 at 1700:

YouTube

YouTube

I suspect that the AH1 fuselage will result in a heavier final product than this AS350, and normally I ran that AS350 at 1900 for better performance and reduction of mushball handling at 1700. With the Vbar I dont think you will have flybar handling/stability issues to contend with, so I think just lift will be the primary concern. So...my guess would be to target around 1900 headspeed thereabouts as a scaler goal for the AH1.

Definately make a build thread somewhere...I'm real interested in the fuselage also

[Richard F.]

That thing sounds awesome!

[Hank79]

Originally Posted by SidewaysLS4

I think you will be looking at 1700 as the bare minimum headspeed for a scaler T500. Below this the lift becomes very marginal on 2 blades. Here's a T500 AS350 at 1700:

http://www.youtube.com/watch?v=RwrYFYbk1wc

I suspect that the AH1 fuselage will result in a heavier final product than this AS350, and normally I ran that AS350 at 1900 for better performance and reduction of mushball handling at 1700. With the Vbar I dont think you will have flybar handling/stability issues to contend with, so I think just lift will be the primary concern. So...my guess would be to target around 1900 headspeed thereabouts as a scaler goal for the AH1.

Definately make a build thread somewhere...I'm real interested in the fuselage also

Will do mate, at the moment I am building a 90 size Hughes NH-500E in a T700E with a OF helitechnic five blade head. The AH-1 will be my next project. I might paint it in Marine colours

[eerie]

is the AH-1 released for sale yet?

[ElectricSheep]

@Hank79: You could definitely sport fly at 1400 RPM (yes, even with a fuselage); if you just just wanted to fly slow like in the YouTube link above you might even get away with 1200 RPM...

BUT you'll need to use asymmetrical blades. I have a pair of 710mm asymmetrical blades from Spinblades on a Logo 600SE, and I've flown that Heli at 950 RPM. Spinblades also makes a 435mm version. Here's a video of someone flying an Airwolf T-Rex 500 at 1400 RPM:

YouTube

YouTube

As you can see, he's flying that thing about 20x faster than the one in the other video (1700 RPM in the parking lot). I know that pilot skill may be the difference between the 2, but I'm just pointing out what's possible at 1400.

Contact Nick at NDHeli.com and ask if they have the 435mm asymmetrical blades in stock. Note that NDHeli.com is in Canada, and AFAIK they're the only Spinblades dealer/distributor in North America. (I have no affiliation with NDHeli; I'm just a customer).

Good luck and keep us posted on what you end up doing!

Sent via Tapatalk on iPhone

[ElectricSheep]

PS> Here's product the link to 435mm Spinblades:

http://www.spinblades.com/index.php?...&product_id=44

Just for kicks, here's a video of a Logo 600SE at 1000 RPM (it can fly 3D at this headspeed because of how light it is):

YouTube

YouTube

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[Elios000]

you could get it low with a 4 or 5 blade head and asymmetrical blades weighted blades
maybe as low as 1000rpm with a setup like that
you would HAVE to go with some kind of FBL at that low to get any roll and pitch rates out of it

[SidewaysLS4]

Originally Posted by ElectricSheep

@Hank79: You could definitely sport fly at 1400 RPM (yes, even with a fuselage); if you just just wanted to fly slow like in the YouTube link above you might even get away with 1200 RPM...

BUT you'll need to use asymmetrical blades.

Wow, 1400. Must be pretty darn light or those blades are amazing .

[ElectricSheep]

Originally Posted by SidewaysLS4

Wow, 1400. Must be pretty darn light or those blades are amazing .

It's just that the asymmetrical blades are designed to provide a lot more lift in one direction. You can still fly inverted but you need to provide more negative pitch (check out that video of the Logo 600SE -- it flies OK inverted )

In the beginning of that video there's a profile shot of the blades and you'll see that the top half of the blade has a "taller" profile than the bottom. One catch is that you probably don't want to do tic-tocs with those blades...


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[SidewaysLS4]

That does sound like an interesting project to take on . I kinda assumed the asymetrical stuff benefited the bigger helis. Maybe a AH1 will have a better chance to be in my future now, lol

Cant change to those blades on that heli...it went 3 blades. Tail hold limits the headspeed down to 1850 as the slowest rpm given enough lift, even with a 5% tail ratio increase (there was a tail blowout in this early test flights video, the tail ratio was increased afterwards to avoid this 'excitement', lol). Maybe with a faster tail it could go slower with more pitch, but very cool anyway

YouTube

YouTube