What caused this wobble in flight?

[firemanup]

Curious what i've got going on with this thing as i'm planning on putting it up on more power in a couple weekends..

I launched a Binder Design Jaguar yesterday for it's maiden flight on an I211, it's stock with the addition of a Binder Avionics bay which adds 4" to the rockets length for a total length of 84" on a 2.6" diameter.

Upon launching the rocket took off nice but right before motor burnout it it had a wobble, or corkscrewed just a bit then straightened out.. it also sounded like the motor coughed a little right at the same time..

This kits total weight is 50 oz.. and i'm wondering if it's just a freak unexplainable thing or if there's other explanations.

Again total weight is 50 oz with 16 oz being in the avionics bay which is located 29" down from the tip of the nosecone. I'm wondering if that added weight maybe made it over stable and did something..??

If that were the case a bigger motor would take care of that until it burns off most of the propellant, then i'd be right back to the same issue..?

Would like to put it up on a J350 in two weeks, but now i'm starting to wonder if i have an issue here or not.. i don't want to magnify something and have it come apart or go bad..

I checked EMRR for the CP on this rocket and they have 3 listed that are no where close to eachother so how do you tell which one is accurate..??

Thanks for any help...

 

[Missileman]

Download a free demo version of Rocsim and check the CP yourself.
Any number of things could have happened. Turbulent air at the altitude it started to wobble for example.
I did have a rocket a while back do something similar when the nosecone started to seperate do to change in atmospheric pressure.
Did you drill a vent hole?
I really don't see over stabilization as causing a wobble. Under those circumstances it would tend to arc over into any wind.
Did you get a look at the motor nozzle after flight?
Perhaps there was a failure there causing asymetrical thrust?

 

[firemanup]

Vent holes are in place in the airframe...

The CP locations listed on EMRR are figured via rocsim and barrowman.. already....

No I didn't remember to take a good look at the nozzle..but i wondered about a chunck of something coming loose and falling into the nozzle before it completely burned and maybe causing a directional thrust.....

 

[DPatell]

Funny you say that. I had a 54mm all glassed model that flew on an I211 for it's maiden flight. I forget how long it was, but it too coned on the way up. The fin profile is very similar to that of the Jaguar.

I believe it's a cumulative effect of small fin area and length put together. Mine had about 1.25 calibers of stability, and still coned like crazy. It did it on an I205 PRO38 as well.

I'm not sure why it happens either, so I will ask the same question!

 

[daveyfire]

Woo hoo! I'm not nuts!

It sounds like you're having coning, which is a serious problem I experienced at last year's BALLS. It seems to happen in long, overstable rockets which have small fins, exactly like a Jaguar. Stine describes coning as pitch-roll coupling, in which "the model has some roll that's induced by fin, nose, or motor misalignments. At some point in the flight, the frequency of the roll becomes the same as the frequency of the motion back and forth in the pitch-yaw axes [from fin correction forces]. The model will start to exhibit a "coning" motion where it spins about the roll axis at the same time that it begins to rotate in both pitch and ya about the CG."

Does that sound like it? We got into a big discussion of how to predict it using RockSim on this thread: https://www.rocketryforum.com/showthread.php?s=&threadid=4941 . Coning can be really bad at high speeds, because tubing wasn't designed to handle forces in the "crush" direction.

I've got a Jag almost complete with dual deploy setup. I'll fly on an I211W and see if it does the same thing yours does. If it does, it's probably coning. If it doesn't, I'd be inclined to go with a nozzle problem or a wind shear.

Hope this helps!

 

[firemanup]

So Davey from what you're describing my plans on moving up to a J350 for the next flight may not be such a good idea..??

I guess i'm a little surprised at that kind of problem with this one on that motor as it barely broke half of mach and was pulling 15g's at it's max..

When i'm running through the simulation on Wrasp and looking at the thrust curve of the I211 it looks to me like it occurred right about the same time that I211's thrust really drops at the end of the thrust curve, it tapers down then just drops and that's where i'm guessing is where this happened..

It was also at about it's max speed or just coming down from max speed of 426mph...

So if this is coning, is there anything I can do with the thing to still be able to fly it under J power, that was the whole intent to begin with... any ideas..?

 

[firemanup]

Read through that thread Davey thanks...

I saw a couple things.... as far as my fins they're on pretty darn straight as far as anything i can tell.

This rocket does have a bit of concentrated weight both in the fore and aft sections (altimeter 16oz up top and motor at the bottom) .

I'm starting to wonder about the flexing of the air frame but saw most of what that thread was talking about was with rockets moving quite a bit quicker..

This bird is somewhat modular in that I could remove 17" of length by taking out one section of air frame, i'm wondering if that would help with the total airframe flexing.

Lastly I'm wondering about reinforcing some of the airframe with extra couplers..Problem here is that the long 34" booster section on the inside of that narrow tube i spilled a bit of epoxy onto the inside airframe when i was coating the upper centering ring..i don't think i could get couplers but half way down it..

Another option, maybe motors with less initial thrust, longer burn..?? but again being a 38mm tube this would limit me to 3 or 4 second burn blackjacks and not get the altitude i was hoping for with a J350... hmmmmmmm back to the drawing board..

 

[daveyfire]

Like I said, I'm gonna try this configuration as well to see if it's an inherent problem with the model or if it was just a fluke in your flight due to a motor hiccup or wind shear (both of which are more possible than coning -- this is a worst case scenario ). I'm gonna be flying on the 19th of this month -- when do you plan to do your J350?

The only reason that coning may become a major problem in flight is if you are pushing Mach. At that point, if the rocket isn't flying straight up, the shock waves become somewhat... um... destructive... and that's the end of your rocket. I think you'll be fine on the J350 as long as the flight remains relatively straight. Maybe try her on an I284 to see if the same thing happens?

 

[firemanup]

J350 flight would be the same weekend you're talking about, 19th and 20th, what better thing to be doing on Father's day right... heh

The J will put me at .83 mach.. gettin a little close there.. The I284 may be an idea... puts me at .7 mach.. i'm getting whimpy in my high power days, i don't care so much about loosing a rocket but when i start adding in electronics and reloadable motors then i start to cringe...

Not sure what i'm gonna do here...

 

[daveyfire]

I guess my vote would be to say go for it, with just motor ejection. Pop the laundry at the top with the motor charge and watch it drift down. That way, if you do shred, it'll be a way cool death for your rocket (the only honorable death for a rocket is a shred, BTW ), and you'll get your case back with only the loss of the vehicle. If you don't shred, stick an altimeter in there and see how high you're getting! Besides, if we didn't push the limit, why would we get all fidgety on the flight line during the coutdown?

 

[firemanup]

Davey have video of the flight here.. Daughter was worried about it going too fast and not being able to keep it in the picture so she's panned out pretty far on it...

Even in the video it's pretty hard to see what's going on..

Here's the video link...

https://www.firemanrocketry.com/videos/jagi211.WMV

 

[daveyfire]

Oh man, you're worried about <i>that</i>? That thing flew dead straight! That little wiggle at the end was probably just it hitting a gust of wind up there, judging by how fast the smoke trail up there was moving. From how that looks, you'll be fine on the J350W methinks.

Pretty flight! I wish all mine looked like that

 

[firemanup]

I said it wobbled "just a bit" .. LOL

Ok well maybe i'm just too anal about it, just wondered that whatever it was would be magnified a bit by the J motor...

Either way maybe another I211 flight is in order to make sure..

That obviously isn't the coning you were talking about then correct..?

 

[daveyfire]

It'll be magnified, but the problem is there isn't much to be magnified!

And if you were wondering about coning, it's an extreme example, but THIS is coning (the same flight of the rocket in the thread above):

My BALLS project from last year

Subsequent destruction at Mach too! Don't blink or you'll miss it

 

[daveyfire]

BTW, it only cones for about a second before it completely shreds. You can barely tell since it happens so fast. It's the little side-to-side dancing maneuver it does before it completely comes apart. The looping and stuff afterwards is what happens when you lose your payload section at Mach. Been there, done that, got the T-shirt

 

[Donaldsrockets]

I wonder if the large body tube to small fins has anything to do with it but I have never seen a Binder Jaguar up close.

However, one of my club members has a Binder Sentinel and under power it goes up nice and straight but at motor burnout, it tends to spiral and wobble around a bit. I've seen him fly it on Pro38 3 grain I205 motors and it did it both times.

I do hope that you get that issue worked out because that thing will RRRIIIPPP on a J350 or if you'd like to go faster, go with the J420R.

I heard that AT may release a J825R for the 38/1080 case. If you really wanted to hit mach, that'd be the motor to use but I believe it's on hold due to a nozzle problem.

Good luck

 

[bsexton]

I have no opinion, advice or hypothesis about "coning". I just wanted to ask how do you find the time and the energy to build so many dang rockets?

I feel so inadequate...

 

[LMazza]

Too cool, two other people on TRF with new Binder Design Jaguars. I just ordered mine a couple days ago along with the avionics bay and an altimeter. This will be my first attempt at dual deployment (just a little intimidated). I'm also building it to take the 38/1080 casing which will require some glassing. I'm really glad I'll have your launch reports to hear from.

BTW, Firemanup what altitude did you get with an I211? Can you also tell how fast/high that setup would go on a J570?

 

[firemanup]

Davey,

Now that's a wicked flight... nope mine was nothing like that one..

Luke,

The kit and avionics bay are pretty straight forward, I had intended to go with a J570 but was advised against it by Mike at Binder as I didn't glass or reinforce the airframe with couplers, so I believe the J350 will be the biggest motor i go with, if that goes ok I may consider stripping the finish this winter and glassing the whole thing as an option.

I got 3774' per the RRC2 with the I211, that thing was out of sight for quite a while coming down before it was finally spotted again under droge about a 1,000 feet up and a couple hundred yards downrange.

Mine with the avionics bay and the way i build came in at 50 oz ready to fly, that's with electronics batteries, and my recovery systems.

Wrasp was pretty accurate when i simmed it for the I211 it predicted about 3700'. With a J350 wrasp sims it to 5348' 28.57 G's and .83 mach/629mph.

With the J570 at my weight of 50 oz I get 6800' 49.6 G's and mach 1.03/783 mph. I don't know what weight glass will add to yours but I simmed it again at 62 oz and got 7085' with 43.14 G's and mach .97/734 mph.. one of those cases where more weight carries more momentum longer for a higher altitude....

 

[daveyfire]

I'm sure it would be awesome on the J570... I flew my 54mm diameter Laser/LOC on one a while back and it got 50 gees and 12,179 feet. Sure would be a hoot in a Jag...

Oh man, now you got me thinking about it. I DID glass mine... umm... get those thoughts OUT of my head...

 

[LMazza]

Thanks Jason, that helps. I'll be sure to post reports (and pics of course!) of my progress and flights.

 

[Kcee]

I've been kind of lurking on this post as I'm about to start my LDRS project in the next couple of weeks. And you guessed it the design is based on the Binder Design Jaguar except for a few modifications the rocket is identical to the original kit.
To save typing I'll cut and paste some of my imformation and .rkt file some people have said it can be done others have told me it's insane you be the judge.


For what it's worth this I hope (unless something else comes to mind) is the
final design for a rocket I've been working on for LDRS.

Its a Binder Design Jaguar knock off the only part from the kit used is the
5:1 ogive nose cone which will be foamed and modified for adjustable nose
wieght. The rest is PML phenolic airframe sleeved with more phenolic
airframe to avoid glassing. Fins, CR,s and bulkheads are made from .125 G10
fibreglass.
Nice H to K rocket and performs very well. Have a look and please feel free
with any input.

Kevin


This was sent back to me by Len Bryan

Hi Kevin,

Nice looking rocket. My only input would be that I would glass or CF the
fins tip to tip if I was planning to go past mach with it. Fin flutter could
toast it pretty quick. That G10 stuff is pretty flexible when it comes right
down to it. BTW, an L730 gets you another 1000 feet but not much speed. You
may have to edit the motor file for the L730 if you got it from the same
place I did. I don't think it is really 7 meters long.

Anyway, I sure hope to make it to LDRS. Not sure yet. If I make it there, I
will fly 3 rockets for sure. 1) My 54mm Lunar Express on a K445. (I must CF
the fins so there is no repeat of the Lil' Lunar Express rapid disassembly)
2) My CF Big Daddy (Estes size) on a 54mm J210. Nutty! 3) A 29mm rocket not
yet built for my Rattworks I-90 motor.

Have fun and show us pics when you build it.

Len


I sent this back

Thanks
For the the reply Len
The fin span on the rocket is 7.684 the fin's themselves are very small and
will be made of .125 G10 and are through the wall to the MMT by a little
over 1/4 inch I plan on building the fincan MMT outside the airframe then
sliding the whole shmeer into the aft end of the rocket.then foaming the
cavity between the airframe and MMT. However a layer of light CF on the
fin's my not be a bad idea at all, it's still all in my mind now until I can
touch it and feel it then I'll know for sure what I'll need to do to keep
the fin's on
I really hope you get to LDRS this year it would be great to have a large
group of guys from the coast to show or support not to mention it's going to
be a very cool place to be.

Cheers Len
Kevin C

Any thoughts would be greatly apprieciated!!

Kevin Crawford

CAR L3 S569

 

[Kcee]

Sorry forgot the file. Hehe

 

[Jerry Irvine]

Originally posted by firemanup

I launched a Binder Design Jaguar yesterday for it's maiden flight on an I211, it's stock with the addition of a Binder Avionics bay which adds 4" to the rockets length for a total length of 84" on a 2.6" diameter.

Upon launching the rocket took off nice but right before motor burnout it it had a wobble, or corkscrewed just a bit then straightened out.. it also sounded like the motor coughed a little right at the same time..

Thanks for any help...

Is the I211 a C-slot? I believe it may have offset thrust by as much as 7 degrees if so.

I have not viewed the video or read in detail this thread.

Jerry

 

[daveyfire]

Originally posted by Jerry Irvine
Is the I211 a C-slot?

Nope. 4x BATES grains, 1.875" long.