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700 Class Electric Helicopters 700 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar.


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Old 07-01-2017, 01:43 PM   #1 (permalink)
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Default My 760x F3C.

Painted the boom white for visibility, ( also painted the tailfins ) until the 760x F3C fuselage gets here..

Great heli, the new F3C pitch arms gives good numbers in vbar, and also calm down the collective during precision hover maneuvers in high wind.

Im using HN7024a 80 dampers from Align. And also the non-slant F3C skids ( not on this pix ).

EP Energy 740 F3C main blades ( stock Align 760 whas not heavy enough imho ).

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Old 07-01-2017, 05:39 PM   #2 (permalink)
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Looks good!


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Old 07-01-2017, 05:44 PM   #3 (permalink)
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Thanks

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Old 07-02-2017, 03:02 AM   #4 (permalink)
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Nice colour scheme. Liking the white boom, just need to get rid of the raked skids
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Old 07-02-2017, 05:22 AM   #5 (permalink)
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She looks really good. Personally i like the raked skids as they keep the tail blades out of harm's way, and I like the nose down stance... But i guess for F3C they may not be ideal?

Did you have any issues getting correct pitch range settings on the tail? There has been much discussion about the geometry of the three blade tail being less than ideal.
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Old 07-02-2017, 05:25 AM   #6 (permalink)
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Originally Posted by p1andy View Post
Nice colour scheme. Liking the white boom, just need to get rid of the raked skids
Yep. I have a set of Align straight f3c skids. These slant skids dont work well for F3C. But it looks cool
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Old 07-02-2017, 05:28 AM   #7 (permalink)
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Originally Posted by Grumpy_Old_Man View Post
She looks really good. Personally i like the raked skids as they keep the tail blades out of harm's way, and I like the nose down stance... But i guess for F3C they may not be ideal?

Did you have any issues getting correct pitch range settings on the tail? There has been much discussion about the geometry of the three blade tail being less than ideal.
Thanks!


Yes, I got some issues with the tail.
I hade to tweak the gyro alot more then im used to.
I made a reply about it in this thread:

https://www.helifreak.com/showthread...=784999&page=2

It works, but if I would have used another gyro, without all the settings vBar allow, I think it would be much worse..

//Anders
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Old 07-02-2017, 06:03 AM   #8 (permalink)
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Thanks!


Yes, I got some issues with the tail.
I hade to tweak the gyro alot more then im used to.
I made a reply about it in this thread:

https://www.helifreak.com/showthread...=784999&page=2

It works, but if I would have used another gyro, without all the settings vBar allow, I think it would be much worse..

//Anders
That's very interesting and exactly what would be expected with so much difference in pitch range one way vs the other.

Have you thought about doing Atomic's modification? It would be really good to hear a back to back comparison.
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Old 07-02-2017, 08:57 AM   #9 (permalink)
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That's very interesting and exactly what would be expected with so much difference in pitch range one way vs the other.

Have you thought about doing Atomic's modification? It would be really good to hear a back to back comparison.

Well, I always hade that fallback plan ,even before I got the 760x.
( thanks Atomic S for that )

But now It works good enough for my application.
F3C flying does not put that much demand on the tail vs 3D.

Instead, for that reason, im planing to put on the normal 2 blade tail on.
3 blade tail whas a trend in F3C for some years ago, when many tried 3 blade head. Now most are back to 2 blade heads. So the benefit of a 3 blade tail , to counter the extra momentum of a 3 blade head, is not necessary anymore..
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Old 07-02-2017, 09:23 AM   #10 (permalink)
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Still tuning.
But it sits nice in hover..


Test with vbar. Flight 8 Align 760x (1 min 18 sec)
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Old 07-04-2017, 12:11 PM   #11 (permalink)
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Yep. I have a set of Align straight f3c skids. These slant skids dont work well for F3C. But it looks cool
Yes raked skids will cost you points every time you take off and land in the hovering moves since you will have to correct the slant on takeoff
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Old 07-06-2017, 01:19 PM   #12 (permalink)
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How do you like it so far?
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Old 07-08-2017, 08:34 PM   #13 (permalink)
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Well, I always hade that fallback plan ,even before I got the 760x.
( thanks Atomic S for that )

But now It works good enough for my application.
F3C flying does not put that much demand on the tail vs 3D.

Instead, for that reason, im planing to put on the normal 2 blade tail on.
3 blade tail whas a trend in F3C for some years ago, when many tried 3 blade head. Now most are back to 2 blade heads. So the benefit of a 3 blade tail , to counter the extra momentum of a 3 blade head, is not necessary anymore..
Three blade tails produce less vibrations than a two blade tail which imo justifies it alone. Also lower angle of attack or lower RPM for a given amount of thrust can improve hard piro stops due to less tail blade stall.

With regards to tail mechanics I like how Gaui does it, just have symmetrical tail mechanics and then use a trim flight to find the neutral point electronically. This way servo resolution and mechanical gain are equal on both sides of the tail.

On helis with a mechanical pitch offset I bias the servo horn to compensate for the unequal tail pitch. I do a normal setup with the tail bellcrank and servo arm centered then bias the arm so that the endpoints of the servo arm are about equal (close to 45 degrees from center) and re adjust the pushrod so that the bellcrank is centered again after the servo arm adjustment. This makes the servo resolution more or less evenly distributed across the pitch range of the tail mechanics. The idea is that on the side of the tail slider that travels less the servo horn also travels less while on the side that travels more the servo also travels more.

Last edited by Atomic Skull; 07-08-2017 at 08:46 PM..
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Old 07-09-2017, 02:47 AM   #14 (permalink)
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Also lower angle of attack or lower RPM for a given amount of thrust can improve hard piro stops due to less tail blade stall.
But of course you can get the same thrust at same RPM from 2 blades by using larger blades, for example a 115mm 2 blade tail can give the same thrust as a 105mm 3 blade. The 2 longer blades will be more efficient so absorbs less power for a given thrust......... So there are pros and cons
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Old 07-09-2017, 05:30 AM   #15 (permalink)
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Yeah im planing to use 110-115 blades with 2 blade tail.

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Old 08-20-2017, 09:10 PM   #16 (permalink)
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I've been looking at the 760x for awhile, how are you liking it by now? Also, what size batteries are you using and what kind of flight times with f3c style flying?
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Old 08-21-2017, 02:49 AM   #17 (permalink)
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Hi

( sorry for my bad English )

I like it alot.
Please use Align HN7024T dampers instead of the hard plastic ones.
Also with the F3C pitch arms you have alot of mechanical resolution, so be prepared to adjust your cyclic ring to avoid binding at the extreme cyclic inputs.
Compared to my SAB Urukay Carbon, the 760x where a bit more sensitive on collective during hover at windy conditions, I found out that I could fix this with shorter blades.
I whent with DH 711 F3C blades, and those fit the rex head super. And I dident loose any preformance on other areas.
To me the 760x flies better ( with the fuse ) then my Urukay, its smoother, and the drivetrain is much more efficienc vs the Urukay.
With the same setup i pull about 20 less MAX-amps vs the Urukay, and I could increase my flight time alot.
With 12s 6200mah lipos my 760, with full fuse, is 6.02kg, and I can fly around 9min at 1850 rpm.
Im super happy with it, and my second 760 is on its way to me
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Old 08-21-2017, 07:39 AM   #18 (permalink)
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Sounds great! Are you using the 2 blade tail hub yet or still running the 3 blade?
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Old 08-21-2017, 08:43 AM   #19 (permalink)
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Sounds great! Are you using the 2 blade tail hub yet or still running the 3 blade?
Hi..
Im using the 3 blade tail. I whas planing to change it but it works just fine. And I can't find any reason why i should change it back to the 2 blade tail.

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Last edited by devilfish; 08-21-2017 at 11:02 AM..
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Old 08-23-2017, 12:34 PM   #20 (permalink)
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Originally Posted by devilfish View Post
Also with the F3C pitch arms you have alot of mechanical resolution, so be prepared to adjust your cyclic ring to avoid binding at the extreme cyclic inputs.
I was just thinking about this. Even with the standard short grip control arms that come with the 700X and running normal (+/- 12.5 Deg) collective range I had to do a bit of modification to prevent the aileron and pitch servo arms hitting the metal heatsink and/or the top part of the frame. This has been covered in another thread and is a 'standard' issue with the 700X.

With the much longer F3C arms you must have to severely limit collective pitch range and/or cyclic ring to avoid binding. You could of course run longer servo arms but that would compromise link geometry and would defeat the object of the longer grip arms, so would be pointless.
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