I had a boomstrike on my fury extreme

[TommyS]

I had a boomstrike yesterday and can't figure out why this happend. It happends in a fast piroflip while upside down 20 meters up in the air. When I got to the crach-site, both blades had a little crack on them, and one blade-holder had both links on the bell-mixer poped off. Apart from the boom was chopped off, this was the only damage. And the blades was realy tight on the blade-holders.

So I don't know whether the links on the bell-mixer popped off, and then caused the boom strike. Or if the boomstrike happend first and then the links popped off. I tryed to pop the links on again, and it was not loose on the ball. The links are amost new.

The engine was not bogging, but I had a very fast pirorate(left stick), so the engine had some extra torque because of that. I have aprox. 10.5 - 11 degree collectice and 7 - 7.5 degree cyclic. It is posible that I used full collective and cyclic at the same time(I use a cyclic ring, so I did not corner the stick).

The last change I did was this http://www.helifreak.com/about8320.html recomended by Eric Larson. I have done piroflips like this for at least 100 flights without any problem, but I have used 6.5 cyclic and 10 collective. I wanted more pitch and got a boomstrike just after this change.

So my question is: Is this to much pitch for the extreme, or was there any other problem that caused my boomstrike???

My heli:
Extreme SAB710 + SAB105
YS at 8.18 and MPII
Orginal white paddles


/Tommy

[DavidH]

Sounds like the dampeners in the rotor head were probably worn and soft.
The extra cyclic deflection you added may also have caused the problem.

100 flights and if you have not replaced the dampeners in that time. I would say that is what caused the problem. Also it would depend on which dampeners and shim combo your using.

David

[TommyS]

I'm using the 2X90 durometer and one thick shim as recomended by Eric Larson. The dampeners was replaced last week, and they do not feel soft after the crash. So this was not the problem.

And I'm flying at 1830 headspeed

/Tommy

[DavidH]

http://www.helifreak.com/about8320.html

Eric Larson wrote:
Keep in mind this is the setup for a more aggressive 3D setup. The new flybar carrier allows for a very fast setup, yet very controllable and stable.


The setup Eric is using consists of the NEW one piece dampeners, plus the new fly bar carrier. So his setup will fly different and react different than what you have.
IF the oring style dampeners were fairly new. Then I would think the additional cyclic you added lead to the boom strike. Also adding to much cyclic to some setups can cause links to pop off in flight.

David

[rappyfly]

Tommys
Pls close your eyes and you have pm. :D

[TommyS]

So if I understand you correctly DavidH

10.5 - 11 degree collectice and 7 - 7.5 degree cyclic is too much on the Fury Extreme with a high headspeed and 90 durometer in the head.

I find this a little wird, since I have never heard this before, and can't find any info in this on helifreak, RunRyder or MA homepage.

When I rebuild my fury, I will use the new flybar carrier and use a litte less pitch, and hope this is good enough for me.

/Tommy

[DavidH]

I had a boomstrike yesterday and can't figure out why this happend

Tommy,
I am just trying to help you figure out why you had a problem.

I wanted more pitch and got a boomstrike just after this change.
So my question is: Is this to much pitch for the extreme, or was there any other problem that caused my boomstrike???

With the information you provided, the only change you stated you made was you increased the cyclic deflection. That change could have caused the links to pop off, or it was enough to deflect the blades into the boom.

I run as much cyclic deflection as I can get on my Tempest. I have never measured it, but I would think it is pushing 8 degs on left/right cyclic. I fly F3C, so I am not moving the sticks like it would require to do a piro flip.

Sorry for your crash and that I couldn't help you find your problem.

David

[TommyS]

I really appriciate your effort to help me David. Maybe I expressed myself incorrect. English is not my nativ language since I'm from Norway, So I'm sorry if I offended you.

I'm just a little frustrated since I'm not able to find out excactly why I crashed. I know the crash is becaus the change I did the day before the crash, but I did more than one change.

* I turned the bell-mixer around to get more pitch-range
* I did increase both collective and cyclig pitch.
* I went from MA0113 to the MA0109 on the left side of the bell-mixer
* I replaced some the links in the head with the HD-links MA121-0(execpt the shortest one on the right side of the bell-mixer)

Since I can feel that the poped-out-link on the head is still NOT loose, the only reason I can see, is that I that the extra pitch caused the crash.

I think that the extra pitch was a good thing(both cyclic and collective), so if I can keep ether the collecive or the cyclic, I want to do that. But since I'm not sure what was the reason, I have to go back to the setup I used before.

/Tommy

[DavidH]

Tommy,
No you didn't offend me. Yes I know unexplained crashes are frustrating.

I have had links pop off a ball from trying to get the most travel out of them. Luckily it was only one blade link and the blade feathered and I was able to land.
I had that heli set up for max travel on the bench. Everything was just at the point of binding. But I would guess in flight that the extra load of the blades caused the link to pop off. Maybe that is the same that happened to you. I don't know if that is the answer, but that is about all I can think of.
Also another scenario is you used full collective which you stated is 10.5-11 degs.
Then you also was using full cyclic at the same time which you stated was 7-7.5 degs. Then with both of them combined, that is 17.5 - 18.5 degs of pitch on the blades. Blades pretty much stall at 16 degs of deflection. So that may have been the problem also.

Just trying to cover all aspects of the problem.

David

[EricLarson]

Hi, well I am at work so this will be shorter than normal and I will answer more at home tomorrow.

There are many possible reasons but more cyclic and more pitch by them selves can result in a boom strike. I for one can boom strike any machine if I want to as I know the combination that will do it most any time. David is right on the money with the combination of the pitches leading up to possible problems. With the more power we have the more pitch we can pull. The problem comes in when we pull so much pitch that the blades stall and impact air takes over. The motor will continue to pull and may even unload and the impact air will cause the blades to flex enough to get into the boom.

We are looking at stiffening up the blade grips to help with this issue but that may cause other problems. I will say that collective management is necessary on these machines. With a good setup I frankly can not break the stratus which is something I can not say about most any other machine. I can however boom strike the model when running large pitch and cyclic that I normally fly with.

It could be other issues also such as a popped link or some binding? Or just a part failure.

More likely it may have been lots of pitch and cyclic and a bit too aggressive negative move. I assume it happened when you where in negative pitch and a lot of cyclic. Best recommendation is don't bury the negative 11+ and add full cyclic, as that is a sure recipe for disaster. Add a bit of wind and boom, you have a boom strike.

I will look over this post tomorrow and see what I wrote. Need to get going now.

[EricLarson]

ok, just got home. Read what I wrote in a hurry and it mostly made sense.

I generally have mixed feelings about giving out my exact setups and try to put some caution into the wording. I generally describe my setup as aggressive.

With the motors we have now we are really able to push these flying machines to the limits. We continue to improve them, but as we do the power gets better. The flying style we are involved in now also puts extreme stress on the models and increased the odds of failure due to maintenance, part failure, or limitation of the model.

To give another example was the flybars. I know several very well known pilots that break many flybars every year. A couple change flybars every week. I was changing mine every 2 weeks or so and replacing dampeners every 2 gallons. We have solved that issue with the new 1 piece dampener and flybar carrier. MA was the 1st to really solve the flybar breaking issue and I am very happy about that.

Back to the boom strike. In my opinion it is a limitation of our equipment right now. With 710 blades and the power we have we are running very extreme pitch and cyclic deflections. When negative pitch and a lot of cyclic are done at the same time, there is an increased risk of boom strike. This is also compounded by large aggressive light paddles, and different blades. Tommy I see you are running SAB blades. They are very high quality but also flex quite a lot. That can also lead to an issue though I have seen and had boom strikes with V-Blades also.

Simple answer, be cautious and use some collective management with negative pitch when using large amounts of cyclic pitch.

Hope that helps some. And I am sorry to hear about the crash. Good luck with your flying!

[TommyS]

Thank you for your clarifying Eric and David.

I am working on my collective management, but sometimes my brain locks up, and I do full collective and cyclic deflection. So I have to set up my mashine, so this wont kill it. The boomstrike happends after flying 5 min. I was practicing piroflip for 5 min, and it all went good. Then sudden, I over-corrected while inverted. I guess that the blade over the boom got full deflection of cyclic and collective. That led to my boomstrike.

I liked the 7 - 7.5 cyclic pitch, so maybe I just turn the collective down to 9-10. You describ you setup as aggresive. I like a very aggresive setup too, but since I'm not a profesional pilot, the setup has to be forgiving, if I do some errors.

Now that I have to replace some parts, I will go for the V-Blades and the new flybar carrier. Maybe the new one-pice dampers. Are they available Eric?

And do any of you know where I can get the V-Blades? I have send an e-mail to eastCoastEctremeHelis, but they have not responded. I know they had a funfly this weekend, but now it is Tuesday.

/Tommy

[DavidH]

Tommy
Ricks RC or Rays Heli Resources that advertise here on the front page of Helifreak should have everything you ask for .
I know Rays has the new fly bar carrier, one piece dampeners and V blades.

0844-12 one piece dampeners
126-105 New flybar carrier for the Extreme Head

http://www.raysheliresource.com/
http://www.ronlund.com/

Either one of the above should have what you need.
Ray had all the items at an event few days ago.

David

[EricLarson]

As David said Ray is a good guy.

yes I agree that reducing the pitch range will fix the possibility of the boom strike. It is not as powerful of a pitch setup but it is safer.

I will say I have gone up to around 9 degrees of cyclic without problems in the past. But again, collective management and just being aware of what is going on will help too. I know Alan Szabo runs a ton of cyclic and I have seen him boom strike like most all of us, so this is a common issue as we gain more power.

later,

[TommyS]

Just a theoretical question:
If you increase the height between the head-block and boom, can you get away with more pitch? Ether lowering the boom or lift the head-block higher from the frame. Or do this bring up other problems?

/Tommy

[EricLarson]

Yes to an extent though the stock Freya is VERY tall and I can boom strike that machine no problem.

Also when you extend the main mast you also cause the roll tendencies of the machine to change.

With both blades extended grab one blade and flex it down until it hits the boom. It may surprise you to see how much force and flex you need to do that. Again stiffer span wise blades also help as the blade flex is the problem.

The issue is the blades are stalled and the impact air is flexing the blade that much. To try keep that from happening we would probably need nearly and inch more main mast and that may not solve 100% of it. I for one don't want the head to be that tall. FYI I have boom struck 3 inches from the tip of the blade before :shock:

These machines are very powerful and are capable of breaking themselves if put into the right conditions. With that in mind I have flown many gallons of fuel testing items TRYING my damnedest to break them and have not had any failures of normal components. I still do not do things that will more than likely result in a boom strike as I know what will probably happen.

[TommyS]

I tryed to flex the blades down, but it need so much force, that I did not dare to flex it all down to the boom. Afraid to break something.

We are looking at stiffening up the blade grips to help with this issue but that may cause other problems.
MA sells a metall-grip. Is it this you are talking about? I have heard that Jason did not use the metal grips when he was in MA, because it wear the thrustbearings realy fast.

I have hear that the V-Blades are much stiffer then the SAB's. But how it the new radix blades and the new NHP Cam blades compare. I have heard much positive about the NHP blades, and I don't see that Curtis move to a poorer blade, when he went from V-Blades to his new radix blade.

/Tommy

[EricLarson]

Yep I agree on the blade flex, it it did it in the air :shock:

That Radix blades are the latest and greatest at the moment. They do look very nice. V-Blades have been out for a while but are a very solid and good flying blade. NHP also makes nice stuff though they tend to not be quite as durable. Again NHP is nice stuff.

The metal blade grips are not for use on this head. I do have a tempest 3D head and have not had a boom strike on it. I have not had any bearing problems with it. It is much less aggressive than the 3D head on the extreme and Stratus though.

[rappyfly]

Yes to an extent though the stock Freya is VERY tall and I can boom strike that machine no problem.

Also when you extend the main mast you also cause the roll tendencies of the machine to change.

Just get a Avant or Synergy, their boom are further apart.

Me for example with ex-aggressive setting, I threw or broke a lot of things out of my fury (too much to list) :mrgreen: but never boom strike them.

So conclusion might be like watch TV commerical how much money or how good the product is but the fine prints always be:personal experience may vary. :mrgreen:

[EricLarson]

Rappyfly, I am sure you can break any helicopter. I will be very interested to hear your report on the Avant or Synergy after flying one for a year.

[TommyS]

Just a queston Eric:
Do you think that the bell mixer options I used, had any affect on my boomstrike. I switched from the double ball to the 0109 ball on the on the arm/rod down to the swashplate. Or was it only the extra pitch I set up on the mashine?

I used the orginal extreme plastic bell mixer. Is there any difference beween that and the MA123-13 ALUMINUM BELL MIXER?

/Tommy

[EricLarson]

The mixer setting you have did not affect it. It is just a case of too much cyclic and too much negetive at a bad time. As long as a model has a strong running motor, I can do the same thing on any model.

In fact I am running some custom stuff for testing now and I am getting some very extreme thows with no issue. But I do realize the limitations of the blades and total pitch available. I definately do not apply tons of negetive with full cyclic. It is a sure way to a boom strike. I can back flip full aft cyclic and use lots of negetive, but if I use ail and ele cyclic and lots of negetive it will probably boom strike.

take it easy,