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SAB Goblin 630/700/770 SAB Heli Division 630/700/770 - Goblin Helicopters Factory Support


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Old 03-29-2021, 04:36 PM   #41 (permalink)
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Originally Posted by OnTheSnap View Post
They give a really awesome rigid direct response. While also running low head speed or doing autos absolutely like glass without resonance or weird behavior.

Normally there is quite some compromise and ugly break in periods with the stock dampening.

I have them on a Kraken, K580N, and bought a set for the Raw I'm building.
How is your RAW doing and how are you liking the XG dampers in yours?
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Old 03-29-2021, 04:54 PM   #42 (permalink)
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I had a horrible tail bounce in my RAW with stock dampers. Rigidcore dampers cured the problem.

Also, tried them on the Kraken which didn't have any noticeable problems. Stops and direction changes are even better now.

I run my RAW at 1750/1850/1950

Kraken is 1600/1750/1900

No noticeable side effects at any of my headspeeds. If your flying 3D I would skip the stock dampers.
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Old 03-29-2021, 11:56 PM   #43 (permalink)
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I had a horrible tail bounce in my RAW with stock dampers. Rigidcore dampers cured the problem.

Also, tried them on the Kraken which didn't have any noticeable problems. Stops and direction changes are even better now.

I run my RAW at 1750/1850/1950

Kraken is 1600/1750/1900

No noticeable side effects at any of my headspeeds. If your flying 3D I would skip the stock dampers.

What FBL setup are you running?
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Old 03-30-2021, 09:46 AM   #44 (permalink)
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What FBL setup are you running?
Brain

No FBL settings can cure a tail bounce that is separate from the blades (there are no forces available to correct the issue)
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Old 03-30-2021, 10:05 AM   #45 (permalink)
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I guess it would come down to what you mean by tail bounce. If it is an elevator bounce, also called porpoising and maybe one or two other ways to describe it, there definitely IS an adjustment that can cure it. Last weekend I was getting it for my Specter 700 on full collective loops at 2100 headspeed when I would settle out at the bottom of the loop. Would do it for forward or backward loops. A simple drop in elevator D-gain fixed it. Tried like hell to get it to do it after the adjustment - never came back.
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Old 03-30-2021, 10:16 AM   #46 (permalink)
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The bounce I'm describing is the tail dropping separately from the blades during hard stops and transitions. No FBL setting will fix that.
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Old 03-30-2021, 11:57 AM   #47 (permalink)
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So it is an elevator shift? Tail bobbing up and down?
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Old 03-30-2021, 12:03 PM   #48 (permalink)
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So it is an elevator shift? Tail bobbing up and down?
The tail bobs in the elevator axis on hard stops, but the problem is only in the tail, not the blades.

Not my first time encounter this. Its always a damper problem (despite trying to some really extreme FBL settings in an attempt to cure it)
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Old 03-30-2021, 12:17 PM   #49 (permalink)
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I was just trying to make sure I understood. In that case I'd have to disagree, it is tunable. And adjusting elevator D-gain or any of the cyclic gains is not something extreme. Especially, if you know exactly where the issue sits. If you are fumbling around messing with all the gains, I would agree that would be an extreme measure. If a harder dampener can correct the problem as well, great.

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Old 03-30-2021, 12:36 PM   #50 (permalink)
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I was just trying to make sure I understood. In that case I'd have to disagree, it is tunable. And adjusting elevator D-gain or any of the cyclic gains is not something extreme. Especially, if you know exactly where the issue sits. If you are fumbling around messing with all the gains, I would agree that would be an extreme measure. If a harder dampener can correct the problem as well, great.

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What force would the FBL controller use to fix the problem? The symptom only appears in the tail, not the blades.

Just for kicks I went to both extremes on Elevator D gain (and numerous other settings). Nothing changed the behavior

Dampers fixed it on the first try as I has with numerous other airframes. Only difference in this run was using rigid dampers instead of adjusting the stock dampers with shims.
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Old 03-30-2021, 12:48 PM   #51 (permalink)
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This issue always appears in the tail, never blades. At least never had a blade issue. You said yourself it was in the Elevator axis, right? What you are trying to say is that the ONLY way to fix this issue is with a hw change, right? I'm telling you, that it's not likely the heli had inherent hw issues that your only recourse was to change dampeners. Your assertion that this cannot be fixed with tuning is likely wrong.

It's okay if the dampeners worked for you. An easy fix if that is the case. I know for a fact however, that the stock dampeners have no problem, as many others can likely attest to.

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Old 03-30-2021, 01:11 PM   #52 (permalink)
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Originally Posted by jrman83 View Post
This issue always appears in the tail, never blades. At least never had a blade issue. You said yourself it was in the Elevator axis, right? What you are trying to say is that the ONLY way to fix this issue is with a hw change, right? I'm telling you, that it's not likely the heli had inherent hw issues that your only recourse was to change dampeners. Your assertion that this cannot be fixed with tuning is likely wrong.

It's okay if the dampeners worked for you. An easy fix if that is the case. I know for a fact however, that the stock dampeners have no problem, as many others can likely attest to.

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The tail is bouncing in the dampers. You can see it visually.

There is no force available to counteract this behavior. You might be able to mitigate it slightly through FBL settings but any change to this will also affect the head which is working to my liking.

I hate to go this far off-track. These dampers fixed my problems. I could have fixed this in the stock dampers as well.
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Old 03-30-2021, 01:35 PM   #53 (permalink)
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The tail is bouncing in the dampers. You can see it visually.

There is no force available to counteract this behavior. You might be able to mitigate it slightly through FBL settings but any change to this will also affect the head which is working to my liking.

I hate to go this far off-track. These dampers fixed my problems. I could have fixed this in the stock dampers as well.
I have no doubt you can see it and maybe even hear it in some cases. Mine you could hear with a 2100 headspeed on a hard maneuver.

Not sure why you say there are no force or adjustment to counteract this behavior. You said previously that the movement or issue occurs in the elevator axis. Are there not adjustments available in that axis to counteract any unwanted forces?

As I said, if this is the route you took and it corrected your problem, great. Problem solved. I have no doubt that what you say is true. I have had the issue in two systems previous to this most recent adjustment I made on my Specter 700, and simple reduction in elevator D gain fixed it. And reductions of 5-10% have no noticeable changes in the way your system flies, unless your were dropping to 0. In my case ele-D was at 55 and I dropped to 45.

My only issue is with you saying "No FBL settings can cure a tail bounce". Seen it and done it. I have 16 flights on my RAW and the stock dampeners for me at 1700/1900/2200 have been working great. I'm sure however, I may chose a harder one in the near future, but maybe not these.

I also think that if there really was no tuning cure for your issue or for anyone else having the same problem, then likely many more would have it and SAB would be having to work on correcting them. Personally, I wouldn't be happy for a brand new system operating like that and having to buy something more to get it working right, but that's just me.
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Old 03-30-2021, 01:55 PM   #54 (permalink)
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Tail is seeing a pendulum effect on hard stops. Tail blades only offer yaw correction so how could FBL settings fix the problem without also affecting the head?

You can visually see the pendulum in head and neither the rotor or the tail has any force available to counteract this.

No coincidence that stiffer dampers fixed this problem.
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Old 03-30-2021, 03:33 PM   #55 (permalink)
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Tail is seeing a pendulum effect on hard stops. Tail blades only offer yaw correction so how could FBL settings fix the problem without also affecting the head?

You can visually see the pendulum in head and neither the rotor or the tail has any force available to counteract this.

No coincidence that stiffer dampers fixed this problem.
Your head is showing the pendulum effect. Easy to see how FBL settings can solve it - to me. If you had no luck reaching that point, then I understand your belief. Again, glad these fixed your issues. I personally don't believe SAB ruined the RAW by giving me poor dampeners and having to go out and buy new ones just to get rid of my issues - not that I personally had any.

Happy to see your points and that your issues were corrected. I'm okay that you don't agree with me. I should also be able to disagree with you.
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Old 03-30-2021, 03:48 PM   #56 (permalink)
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I agree with jrman.

I don't get how you can say that there's no force that could counteract the bobble. Of course there is. The force that can eliminate that wobble (and also creates it in the first place) is the pitch axis. The tail is attached to the airframe. The airframe is attached to the rotor head. Any effect on the pitch axis will affect the entire tail. Any bobble in the tail will be detected by the FBL unit. And can be corrected for.

The rigid dampers may have fixed the issue, but that's more just because it changed the interaction between the head and changed how the gains affect everything. Maybe whatever setting was wrong and causing it to bobble was the wrong setting for the stock dampers but the right one for the rigid ones.

In fact, that's almost certainly the case - with poor settings, the FBL is constantly sending back and forth commands to the servos in the pitch axis trying to correct the error. The dampers, being slightly soft and compressible, make it so that there is a delay between when the blades move and when the entire rest of the airframe (including the tail and FBL uint) moves, so it's constantly chasing the axis to try to control it. But when you put the rigid dampers on there, it became much more rigid (obviously), and so the commands that the FBL unit was sending to the pitch axis suddenly were correct, and the bobble was gone.

I fully believe you in that changing to these dampers made the bobbles go away, but it could also have been eliminated electrically with some effort in figuring out what to change.
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Old 03-30-2021, 04:44 PM   #57 (permalink)
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You guys are funny.

I might entertain this stuff if there were another set of rotor blades on the tail in the elevator axis. This one of the primary reasons for having hard dampers in the first place.

I enjoy playing with FBL settings and I've pushed every Brain settings from min to max over the years. There is no setting that will either introduce or fix this behavior.

Could also be I'm not explaining the behavior accurately. Should have taken video prior to changing the dampers (I didn't because it was obviously caused by the dampening system)
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Old 03-30-2021, 04:52 PM   #58 (permalink)
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Should have taken video prior to changing the dampers (I didn't because it was obviously caused by the dampening system)
Maybe SAB should do some re-designing then. If I had that problem and couldn't tune it out, I'd be trying to return it. I'm not one to drop a $1k on a heli just to find out I need to spend more because something isn't right.
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Old 03-30-2021, 05:01 PM   #59 (permalink)
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Maybe SAB should do some re-designing then. If I had that problem and couldn't tune it out, I'd be trying to return it. I'm not one to drop a $1k on a heli just to find out I need to spend more because something isn't right.
Again, I could have tuned this out in the stock dampers.

Based on your statement I have to assume you expect stock dampening to work out of the box with all setups and flight styles.
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Old 03-30-2021, 05:41 PM   #60 (permalink)
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Again, I could have tuned this out in the stock dampers.

Based on your statement I have to assume you expect stock dampening to work out of the box with all setups and flight styles.
Your original statement was that no FBL adjustment would tune that out unless I misread your previous.

To work? Absolutely, without issues. If the OEM puts up several dozen videos of their pros doing all kinds of crazy shit with it in stock form, I should reasonably expect the same, if I was capable, and definitely in a lower state as you mentioned your headspeeds are relatively low (some are going as high as 2400). Obviously "working" and "liking" are two different things.

So think about if you had gone onto the SAB site and complained that their brand new heli had the issues you're having and their response was you needed to buy X to correct it. I know how that would make me feel about my purchase. You?
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