Forums: Skydiving Disciplines: Swooping and Canopy Control:
Tail flutter during high speed dive

 


stayhigh  (F 111)

Apr 11, 2011, 7:14 AM
Post #1 of 22 (2492 views)
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Tail flutter during high speed dive Can't Post

How many of you have seen this or felt this????

I did the search and seems like this can happen on any x-braced canopy in a high speed dive. And im not talking about breakline being too short, not a bucking feel but more or less quick pulsating vibration.


Any feedback would be nice.


davelepka  (D 21448)

Apr 11, 2011, 7:39 AM
Post #2 of 22 (2445 views)
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Re: [stayhigh] Tail flutter during high speed dive [In reply to] Can't Post

 
A couple of years ago, I think this was commonly seen on the Xaos canopies in competition. I don't know if it has been resolved, or if it needed to be resolved, but it did come up on DZ.com.

About the same time I was getting a reline on my Velo, and seeing as PD bartacks the loop for the toggle, I asked for an extra inch or two of length, and was surprised when they refused.

This lead to an e-mail exchange with John Leblanc where he explained the the length of the brake line was such that it 'held' the tail in place during high speed dives, and that if you made it longer, it would lead to flutter.

However, very recently, like within the last month, I have read here that people have been letting the steering lines out on their Velos, and that one guy even claimed that the factory built him a line set with longer brake lines. I don't know if the longer lines have resulted tail flutter, or if the guy claiming the factory did his is full of shit, but that's what I read.

Overall, I think it's just a function of loose steering lines and super-high airspeeds in a dive. From what I recall back when it was discussed here about the Xaos guys, it was no big deal and it just goes away when you slow down or apply a little control pressure.


wildcard451  (D License)

Apr 11, 2011, 10:45 AM
Post #3 of 22 (2383 views)
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Re: [davelepka] Tail flutter during high speed dive [In reply to] Can't Post

Dave, I just had my ve103 relined - it was relined factory - I felt enough tail flutter on front riser input (24" risers) to be concerned, and confirmed to be moderate flutter by other HP pilots on the ground.. Letting 3" out has resolved this issue, and back to where I prefer my brake settings on my canopy.

/no flutter
//no "over" control issues with mild input on transition to toggles


LetsGoOutside  (D License)

Apr 11, 2011, 6:48 PM
Post #4 of 22 (2309 views)
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Re: [stayhigh] Tail flutter during high speed dive [In reply to] Can't Post

Echoing/simplifying what's been said here. Have seen this when brake lines been the wrong length in either direction.


mchamp  (D 32129)

Apr 11, 2011, 8:07 PM
Post #5 of 22 (2287 views)
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Re: [stayhigh] Tail flutter during high speed dive [In reply to] Can't Post

Something similar to this at 2:13?
http://www.youtube.com/...=VxDw4RnBd2M#t=2m13s


davelepka  (D 21448)

Apr 12, 2011, 5:01 AM
Post #6 of 22 (2219 views)
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Re: [wildcard451] Tail flutter during high speed dive [In reply to] Can't Post

Quote:
Dave, I just had my ve103 relined - it was relined factory - I felt enough tail flutter on front riser input (24" risers) to be concerned, and confirmed to be moderate flutter by other HP pilots on the ground.. Letting 3" out has resolved this issue,

So short steering lines caused tail flutter? Is this during front riser dives, or is it present when you use only harness?

I ask because short lines have traditionally caused more of a 'bucking' than a flutter, and it comes from pulling the riser with the toggle in your hand, so in essence your diving and braking the canopy at the same time. Traditionally, this has been a problem for 'newbie' swoopers who don't know any better, but who also don't use harness only for any part of their turn. It would be interesting to see if this phenomenon would go away when you release the front riser, but continue the dive with the harness.

Either way, I also have a 103, and it currently has a brand new factory line set. Between the original line set and the first reline a couple years ago, I haven't had any problems with flutter or bucking of any kind. I'll jump this thing in the next couple of days and see how it all shakes out.


phoenixlpr  (D 3049)

Apr 12, 2011, 6:58 AM
Post #7 of 22 (2187 views)
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Re: [davelepka] Tail flutter during high speed dive [In reply to] Can't Post

In reply to:
So short steering lines caused tail flutter? Is this during front riser dives, or is it present when you use only harness?
No. Too loose break lines can cause tail flutter.


stayhigh  (F 111)

Apr 12, 2011, 7:00 AM
Post #8 of 22 (2187 views)
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Re: [mchamp] Tail flutter during high speed dive [In reply to] Can't Post

i guess it is something similar to that, but i never looked up.

it feels similar to what the video shows.

the flutter starts after around 630 rotation up high, when im facing the ground with high g's, as soon as I slow the turn it goes away.


davelepka  (D 21448)

Apr 12, 2011, 7:06 AM
Post #9 of 22 (2182 views)
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Re: [phoenixlpr] Tail flutter during high speed dive [In reply to] Can't Post

Quote:
So short steering lines caused tail flutter? Is this during front riser dives, or is it present when you use only harness?

--------------------------------------------------------------------------------

No. Too loose break lines can cause tail flutter.

Thanks genius. Did you read my entire post, or the post it was referring to? How about my first post on the thread?

The guy claimed tail flutter, and that it was solved by lengthening his steering line by 3 inches. The rest of my post was tyring to find out if it was actual flutter, or the bucking you typically see with short lines.

Quite the contributor, you are.


d100965  (D 100965)

Apr 12, 2011, 8:13 AM
Post #10 of 22 (2157 views)
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Re: [davelepka] Tail flutter during high speed dive [In reply to] Can't Post

I sent my standard Velo 90 back to PD for a reline last year around early 2010.
(I originally purchased that Velo with +3 on the brakelines a few years before after having downsized from a Velo 96 that also had extended brake lines).
I changed the brakelines (due to wear) to Vectran a while later after a few swoop comps and kept them at +3.

So back to the PD reline, after extensive talks with PD directly and with a PD Factory Team Pilot I had a new line set fitted again, HMA 500 with +3 on the brakelines.

I ordered a Comp Velo 84 last month and spoke with PD again regarding brakeline length.

PD said to me that they make their Comp Velo with +3 (over the stock Velo) as standard.
And I was also told by PD and confirmed by a PD Factory Team Pilot that the PDFT currently run +6 on their Comp Velos. I assumed they meant +6 over a standard Velo.
So a Comp Velo which is +3 over a standard Velo and +3 again. Get it?

I don't think I've posted this info before but if davelepka is referring to me then I'm definitely not full of shit.

tagline:-
Everytime I log onto dropzone.com I seem to get automatically redirected to davelepka.com instead.......


(This post was edited by d100965 on Apr 12, 2011, 9:09 AM)


Premier ianmdrennan  (D 25821)
Moderator
Apr 12, 2011, 9:38 AM
Post #11 of 22 (2125 views)
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Re: [d100965] Tail flutter during high speed dive [In reply to] Can't Post

Quote:
PD said to me that they make their Comp Velo with +3 (over the stock Velo) as standard.

Correct.

Quote:
....that the PDFT currently run +6 on their Comp Velos. I assumed they meant +6 over a standard Velo.

Not all of us. It's preference. I like the 'stock' settings for the VC and have my 90, 84, and 79 all 'stock'. Some of the taller folks do have longer settings, it's to accomodate their knuckle dragging arms....Smile

Quote:
tagline:-
Everytime I log onto dropzone.com I seem to get automatically redirected to davelepka.com instead.......

Be nice, and don't stir the pot please Smile

Blues,
Ian


Premier ianmdrennan  (D 25821)
Moderator
Apr 12, 2011, 9:41 AM
Post #12 of 22 (2121 views)
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Re: [stayhigh] Tail flutter during high speed dive [In reply to] Can't Post

In reply to:
i guess it is something similar to that, but i never looked up.

it feels similar to what the video shows.

the flutter starts after around 630 rotation up high, when im facing the ground with high g's, as soon as I slow the turn it goes away.

Probably is. I've seen VX's do this a lot. The ZP JVX's as well but not nearly as frequently as the VX (I have never seen an all sail one flutter though).

I have noticed, though, that canopies seem more susceptible to this at high altitudes. What elevation do you jump at?


(This post was edited by ianmdrennan on Apr 12, 2011, 9:42 AM)


DocPop  (C License)

Apr 12, 2011, 10:42 AM
Post #13 of 22 (2099 views)
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Re: [ianmdrennan] Tail flutter during high speed dive [In reply to] Can't Post

In reply to:
I have noticed, though, that canopies seem more susceptible to this at high altitudes.

Is that purely a function of canopy terminal velocity?


stayhigh  (F 111)

Apr 12, 2011, 11:03 AM
Post #14 of 22 (2093 views)
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Re: [ianmdrennan] Tail flutter during high speed dive [In reply to] Can't Post

i jump at 1100 ft. not too high.

i guess it is the wing design issue.
Are 9 cell design proned to have flutter issue more than 7 cell design????

has anyone died or got seriously injured due to tail flutter issue???


(This post was edited by stayhigh on Apr 12, 2011, 11:05 AM)


Premier ianmdrennan  (D 25821)
Moderator
Apr 12, 2011, 11:59 AM
Post #15 of 22 (2071 views)
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Re: [stayhigh] Tail flutter during high speed dive [In reply to] Can't Post

Quote:
Are 9 cell design proned to have flutter issue more than 7 cell design????

Nah, I don't think it's a 9 vs. 7 cell thing. I've seen both do them given certain circumstances. I don't have the appropriate aeronautical/design knowledge to offer anything other than an opinion on it though.

Quote:
has anyone died or got seriously injured due to tail flutter issue???

No. That said, it's annoying as all hell, and just about drove Loud Dan at the SA 2009 WC to insanity when it sounded like a MAC truck engine brake going off each time he landed.

It is, however, incredibly inefficient to have your wing flapping about like that.

Blues,
Ian


stayhigh  (F 111)

Apr 12, 2011, 12:39 PM
Post #16 of 22 (2062 views)
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Re: [ianmdrennan] Tail flutter during high speed dive [In reply to] Can't Post

thx for the reply.

so the flutter tail is the sign of canopy about to become a whore at the dz and go from one instructor to another????


Empadinha  (D 32431)

Apr 12, 2011, 3:51 PM
Post #17 of 22 (2038 views)
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Re: [stayhigh] Tail flutter during high speed dive [In reply to] Can't Post

I recently started to fly a VX and this is the type of vibration I feel on my turns (fronts + harness). I don't know if it's normal or not but I noticed some slack on the D lines and that allows them to flap around as you can see on the video (and what I believe is causing this slight vibration). Any thoughts?

http://www.youtube.com/watch?v=Sy9BPPT-a64


(This post was edited by Empadinha on Apr 12, 2011, 4:56 PM)


AggieDave  (D License)

Apr 12, 2011, 4:53 PM
Post #18 of 22 (2027 views)
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Re: [ianmdrennan] Tail flutter during high speed dive [In reply to] Can't Post

In reply to:
In reply to:
i guess it is something similar to that, but i never looked up.

it feels similar to what the video shows.

the flutter starts after around 630 rotation up high, when im facing the ground with high g's, as soon as I slow the turn it goes away.

Probably is. I've seen VX's do this a lot. The ZP JVX's as well but not nearly as frequently as the VX (I have never seen an all sail one flutter though).

I have noticed, though, that canopies seem more susceptible to this at high altitudes. What elevation do you jump at?

Modified VX's with the "Jim's comp lineset" seem to do that more than a stock VX, that I have noticed at least. I don't think there are too many VXs modified like that still getting jumped a whole lot out there, I think most of those pilots have just purchased JVXs.


wildcard451  (D License)

Apr 12, 2011, 8:22 PM
Post #19 of 22 (1986 views)
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Re: [davelepka] Tail flutter during high speed dive [In reply to] Can't Post

In reply to:
Quote:
So short steering lines caused tail flutter? Is this during front riser dives, or is it present when you use only harness?

--------------------------------------------------------------------------------

No. Too loose break lines can cause tail flutter.

Thanks genius. Did you read my entire post, or the post it was referring to? How about my first post on the thread?

The guy claimed tail flutter, and that it was solved by lengthening his steering line by 3 inches. The rest of my post was tyring to find out if it was actual flutter, or the bucking you typically see with short lines.

Quite the contributor, you are.

Dave, it wasn't that flutter. It was the bucking. In the initial double front to first 90 of the dive, while still deep in the fronts.
Sorry for the confusion.


chuckakers  (D 10855)

Apr 13, 2011, 6:23 PM
Post #20 of 22 (1894 views)
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Re: [phoenixlpr] Tail flutter during high speed dive [In reply to] Can't Post

In reply to:
In reply to:
So short steering lines caused tail flutter? Is this during front riser dives, or is it present when you use only harness?
No. Too loose break lines can cause tail flutter.

Really. Care to explain that?


rem

Apr 15, 2011, 5:34 PM
Post #21 of 22 (1817 views)
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Re: [stayhigh] Tail flutter during high speed dive [In reply to] Can't Post

soory for my bad language and understanding, but, can you explain in depth your "Tail flutter"?
is it a "stall-start"?
on some JVX, on hard dive, i heard a caracteristics "Flap-flap-flap-flap-flap..." by the "stabilribs"? or external ribs? not the tail.
the tail stay strong as you do not exaggeratedly hang your rears.


skyshimas  (D 29263)

Apr 28, 2011, 11:42 AM
Post #22 of 22 (1670 views)
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Re: [stayhigh] Tail flutter during high speed dive [In reply to] Can't Post

I have experienced flutter on standard velo line set. I like mine 7inches over standard and never had any issues. However, PD doesn't do custom brake settings and only go by 3" increments so after reline I'm jumping 6" over standard and haven't had any problems. Normal velo brake line is way too short for my liking so I basically disagree that long steering lines will cause fluttering its quite opposite by my experience. BTW I'm not tall nor have long arms either.



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