Fun, Learning, Friendship and Mutual Respect START  HERE


Unregistered
Go Back   HeliFreak > R/C Helicopters > Main Forum - Helicopter Talk


Main Forum - Helicopter Talk R/C Helicopters and the people who fly them. VENDOR TOPICS DO NOT GO HERE. Full Scale Heli threads go in OT please


Like Tree35Likes
Reply
 
LinkBack Thread Tools Display Modes
Old 09-24-2021, 06:40 PM   #21 (permalink)
Registered Users
 
Posts: 1,655
 
My HF Map location
Join Date: Apr 2004
Location: Mississippi
Default

Quote:
Originally Posted by Thickfog View Post
Main difference is an extra blade.

Sent from my moto g power using Tapatalk
Two parts… I’m pretty sure there is another blade.

Second part… I can’t confirm it was sent from a moto g power using Tapatalk. That part will remain open for group discussion.
__________________
"Well, nothing bad can happen now."
wjvail is offline        Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 09-24-2021, 07:34 PM   #22 (permalink)
Registered Users
 

Join Date: Mar 2020
Location: Central WA
Default

Extrapilot
I would be interested in understanding the relationship between phase lag and gyroscopic precession. In my experience 70-90 degrees is typical in full scale aircraft. In my mind precession is the "rule" and specific aerodynamic situations alter it to create a given phase lag. Please correct me if i am wrong.
Av8hi is online now        Reply With Quote Quick reply to this message
Old 09-24-2021, 09:34 PM   #23 (permalink)
Registered Users
 
Posts: 13,903
 

Join Date: Dec 2011
Default

Quote:
Originally Posted by Av8hi View Post
Extrapilot
I would be interested in understanding the relationship between phase lag and gyroscopic precession.

There isn't one they are two different things. Phase lag is not gyroscopic precession, it's a lie they tell lay people because it "makes it easier to understand" but all it really does is create confusion like how in grade school they tell you all these "rules" about math such as "you can't subtract a larger number from a smaller number" that they then have to unteach the students later when it would make more sense to just teach them about negative numbers in the first place.
Atomic Skull is offline        Reply With Quote Quick reply to this message
Old 09-24-2021, 10:10 PM   #24 (permalink)
Registered Users
 
Posts: 20,238
 

Join Date: Jan 2006
Default

I have flown two different three-bladed machines, and their two-bladed counterparts:

The Compass Chronos and the JR Forza 450.

In both cases, the two-bladed versions flew extremely well.

The three-bladed versions were slightly more stable, had better hang time in flips and other collective maneuvers, and felt more positive on cyclic (sort of a power steering feel).
trillian and nightflyr like this.
__________________
KBDD-Team Captain, JR DFA Team Pilot. Forza 450, Forza 600N, Forza 700,
Compass 6HV-U, Warp, 7HV,Knight Pro,Knight 3D, Atom, Odin II, 6HV, 3D Plus, Knight 50, Chronos, Velos, Steam 550 and 600, OMP M2 (and anything else I can get my hands on...).
Ah Clem is offline        Reply With Quote Quick reply to this message
Old 09-25-2021, 03:33 AM   #25 (permalink)
Registered Users
 
Posts: 3,458
 

Join Date: Apr 2007
Location: UK, Kent coast
Default

Quote:
Originally Posted by Av8hi View Post
Extrapilot
I would be interested in understanding the relationship between phase lag and gyroscopic precession. In my experience 70-90 degrees is typical in full scale aircraft. In my mind precession is the "rule" and specific aerodynamic situations alter it to create a given phase lag. Please correct me if i am wrong.
Pure gyroscopic precession would require a control input that is applied more or less instantaneously at one single point - the reaction then occurs 90 degrees later. Like in the examples where they are applying the deflection directly to the axle.

With heli swash plates, cyclic input is not a square wave, it's a sine wave that begins before, and continues after the apex point of the control input. Then you have the fact that moving the swash is merely altering the blade pitch. It is then the aerodynamic forces that actually deflect the blade.
__________________
2009 TDR, TDSF, Kasama Dune and Faifa, Minicopter Triabolo 700, RMJ Raptor gasser, Beam E4 and Avantgarde, JR E8 leggero, Suzi Laos, Shape S8, 'TDRex' 800, Rave 450, Trex 500.
trillian is offline        Reply With Quote Quick reply to this message
Old 09-26-2021, 02:54 AM   #26 (permalink)
Registered Users
 

Join Date: Feb 2014
Location: Centurion, South Africa
Default

I only have one 3 bladed heli (goblin havok 700). I run it at a lower headspeed than my 2 bladed 700. Honestly it just feels pretty similar, there's nothing "OMG this is so different I'm going to change all my helis to 3 blade" about it. I don't regret buying it, I love the look of 3 blades (on the ground, you can't see the difference in the air) and, well, I just really wanted a 3 bladed heli for no particular reason.

If you want 3 blades, just get 3 blades, it won't (imho) be better to fly, but that's not always the point, it's about flying what you want to fly. Also, I get less flight time on my 3 blade than my 2 blade, but they are completely different helis: manufacturer, setup, electronics, so that doesn't tell me much by itself.
trillian and torpicaltrail like this.
1am7h30n3 is offline        Reply With Quote Quick reply to this message
Old 09-30-2021, 07:17 PM   #27 (permalink)
Registered Users
 

Join Date: Sep 2011
Default

3 blade = not worth it

Ya cyclic is faster but this can be increase on FBL.
the extra weight offset all benefits plus it will a lipo killer if u fly hard.
__________________
700s and 800s .....
ah_liang is offline        Reply With Quote Quick reply to this message
Old 10-04-2021, 12:56 PM   #28 (permalink)
Registered Users
 

Join Date: Jun 2006
Default

Alright, as a proponent of 3 blade machines (I have a kraken 3 700, trioblin 700, and even a fusion 180 3-blade (it's cute!)).

There IS a different feel. It's very distinct. I will say that my 3 blade machines follow my control inputs much more precisely than my 2 blade machines. The main drawback is the increased weight (which you can feel) and despite the extra mass, doesn't seem to hold inertia as well in autos.

The off center feel is unlike anything I've flown. And the flip and roll rates can be turned up without much issue. Yes, you can turn up the rates on a 2 blade machine, but you can hear and feel the helicopter working hard to get the higher rates.

A 3 blade will take a higher rate and maintain it like it's eating a light lunch.

And the sound... it sounds so clean doing it! Everything sounds cleaner on the 3 blade and I'm guessing this is due to it not needing as much pitch to get the same movement.

I practice on my 2 blades.

I perform on my 3 blades.

Oh and I can fly for almost 6 minutes on my Kraken 3 with a low headspeed and still do full 3D (just much more gracefully). It's a joy, just gotta be careful on the collective cause it's heavy! LOL
Ah Clem, trillian and rickdawg73 like this.
__________________
Team Horizon
Team Amain
My YouTube Channel
MikelG is offline        Reply With Quote Quick reply to this message
Old 10-04-2021, 02:06 PM   #29 (permalink)
Registered Users
 
Posts: 20,238
 

Join Date: Jan 2006
Default

MikelG,

Very nicely stated sir.

I concur!
trillian and MikelG like this.
__________________
KBDD-Team Captain, JR DFA Team Pilot. Forza 450, Forza 600N, Forza 700,
Compass 6HV-U, Warp, 7HV,Knight Pro,Knight 3D, Atom, Odin II, 6HV, 3D Plus, Knight 50, Chronos, Velos, Steam 550 and 600, OMP M2 (and anything else I can get my hands on...).
Ah Clem is offline        Reply With Quote Quick reply to this message
Old 10-05-2021, 11:24 AM   #30 (permalink)
Registered Users
 

Join Date: Aug 2010
Default

A problem with anecdotes like this is- they imply these perceived changes are the result of the single change, when that isnt correct. Doesn’t make the feedback inaccurate- it is just attribution that is inaccurate.

For one- a 3-bladed head by definition cannot have a simple spindle connecting opposing blades. It is a non-teetering setup, generally with grips pivoting on fixed spindles. This yields a much stiffer head, relative to a 2-bladed spindle setup with dampers that have any compliance.

For two- when you add a 3rd blade, you are generally not removing width (chord) from the other 2. That is, you generally are running 50% more blade area in the head. This hits on the concept of solidity- or how much of the rotor area is ‘solid’ as a function of blade area. If you were to add more chord to an otherwise-equivalent 2-bladed machine, you would find that many of the characteristics exist you would have thought were a function of 3-blades. Blades working at lower AOA. Higher blade drag for a given thrust level. Ability to do 3D acro at lower headspeeds.


Point being- most of the talking points associated with 3-bladed machines have more to do with the head and the blade area than an additional blade. If you reduced the blade area of the 3-bladed head to that of the 2-bladed head, it would be a very different experience. If you ran a rigid 2-bladed head vs teetering, same deal.

There are significant downsides to 3-blades in the example given. Most of the blade drag we see in normal flight is ‘profile’ drag- which a function of blade area and RPM. So, for the same RPM, you end up with 50% more drag for any given thrust level. And you don’t get 50% more thrust potential. You get about 30% more. So, you are paying a heavy price in thrust to drag, especially since most pilots cannot stall a 2-bladed head turning 3D RRPM. All you have to do is watch any pro pilot flying a stock 2-blade MSH500 or Trex500 or whatever- and they will outfly 99.9% of those here- running $10K 3 bladed 12hp machines. The standard 2-bladed setup isnt the limitation in the equation except for edge conditions- speed flying or guys going after absolute max performance walls and stuff like that.
rdlohr, trillian, sutty and 5 others like this.
__________________
"The problem with quotes found on the internet is you have no way of confirming their authenticity." - Abraham Lincoln
extrapilot is offline        Reply With Quote Quick reply to this message
Old 10-06-2021, 04:50 PM   #31 (permalink)
Registered Users
 

Join Date: Jul 2015
Default

I have seen many posts about a 3 blade head wobble issues. I dealt with it on my goblin 380 kse but not on my triabolo 800. The triabolo 800 has nhp blades that are supposed to be more flexible to compensate for the rigid head. The goblin has rt 380. Is it possible that these 3 blade head wobbles with cyclic input are due to the the blades being out of phase? I remember reading many threads/posts about how to tune out the head wobble when dealing with it on my 380. I don't recall any of them talking about phase angle tho. Just curious if anyone has tried reducing the phase angle of a fully rigid 3 blade heli to fix a head wobble
emilgoddard is offline        Reply With Quote Quick reply to this message
Old 10-08-2021, 08:10 PM   #32 (permalink)
Registered Users
 
Posts: 13,903
 

Join Date: Dec 2011
Default

Quote:
Originally Posted by ah_liang View Post
3 blade = not worth it

Ya cyclic is faster but this can be increase on FBL.
the extra weight offset all benefits plus it will a lipo killer if u fly hard.

I disagree for tails at least, less vibes and the tail is the largest source of vibration on a helicopter. It also seems easier to dial in a clean left/right piro stop probably because less tail pitch is required for the same amount of thrust so there's less blade stall during a hard stop.


With 2 blade machines I have found I need 110mm blades minimum to keep the tail from moving during hard collective. Go less than that and there will always be some tail drift during a hard collective climb that cannot be dialed out (this was true for both the Vbar and 3DIGI anyway) This has been true for every 700 machine I own regardless of tail ratio or setup (I run all my 700 machines at 1900 RPM). With a three bladed tail the minimum seems to be 106mm.
Atomic Skull is offline        Reply With Quote Quick reply to this message
Old 10-09-2021, 11:04 AM   #33 (permalink)
Registered Users
 
Posts: 3,458
 

Join Date: Apr 2007
Location: UK, Kent coast
Default

Quote:
Originally Posted by emilgoddard View Post
I have seen many posts about a 3 blade head wobble issues. I dealt with it on my goblin 380 kse but not on my triabolo 800. The triabolo 800 has nhp blades that are supposed to be more flexible to compensate for the rigid head. The goblin has rt 380. Is it possible that these 3 blade head wobbles with cyclic input are due to the the blades being out of phase? I remember reading many threads/posts about how to tune out the head wobble when dealing with it on my 380. I don't recall any of them talking about phase angle tho. Just curious if anyone has tried reducing the phase angle of a fully rigid 3 blade heli to fix a head wobble

I have had two 3-blade helis, both with totally rigid heads (original version Triabolo 700 and JR E8) and I've never had a wobble. And, actually, this is the first time I've heard about a general 3 blade wobble issue (perhaps I just lead a sheltered life :-)
__________________
2009 TDR, TDSF, Kasama Dune and Faifa, Minicopter Triabolo 700, RMJ Raptor gasser, Beam E4 and Avantgarde, JR E8 leggero, Suzi Laos, Shape S8, 'TDRex' 800, Rave 450, Trex 500.
trillian is offline        Reply With Quote Quick reply to this message
Reply




Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the HeliFreak forums, you must first register.
Please enter your desired user name, your REAL and WORKING email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself. Use a real email address or you will not be granted access to the site. Thank you.
Email Address:
Location
Where do you live? ie: Country, State, City or General Geographic Location please.
Name and Lastname
Enter name and last name here. (This information is not shown to the general public. Optional)
Helicopter #1
Enter Helicopter #1 type and equipment.
Helicopter #2
Enter Helicopter #2 type and equipment.
Helicopter #3
Enter Helicopter #3 type and equipment.
Helicopter #4
Enter Helicopter #4 type and equipment.

Log-in


Thread Tools
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On




Copyright © Website Acquisitions Inc. All rights reserved.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.

SEO by vBSEO 3.6.1