BroncBuster II (Scion->Leviathan HPR): Finished! Flown (x3)! Tree'd and Free'd!

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Thanks Tango!

Coincidentally, I'll be speeding through Dallas to stop at my sister's in Ft Worth later this week.
I may just take my motor box home with me and scout out a field to test Goldfinger II and BroncBuster II.
 
Thanks Tango!

Coincidentally, I'll be speeding through Dallas to stop at my sister's in Ft Worth later this week.
I may just take my motor box home with me and scout out a field to test Goldfinger II and BroncBuster II.

no fair you having fun and such...

Thanks Caber! I looked for Leviathan's and only found them for $56+ and usually ~$70. And I didn't think to post in he [Wanted] section, nor did I know that a club member has two of them still bagged in his storage.

Yeah he is definitely a collector; I'll wager a crap ton of $$ that he has donated more of those kits to the club than I have ever built in my entire life (and I'm well over 150+ since 1976). And they are not the junk cheapies either!

fm
 
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Very likely. When I get out of work, I'll run a model with simple rounded edges and we shall see! :cool:
Ever since I was a kid I've been asking "but why does it work?", so the investigation will likely never end.



10 more Pro Series II fins to sand into shape, so I will need to get SOMEthing. I had Secret Santa, holiday travel, and a Chute release to buy, so I figured giving manual sanding a try once wouldn't hurt (much). With the dremel, my only worry is uniformity, or accidentally carving round divots in a thinned trailing edge. I'm still really attached to the idea of a belt sander though. It's coverage allows the whole edge (or at least large portions of a really long edge) to be in contact at a time. Plus, I'm used to shaping with them (back when I had a university machine shop full of fun things to use).

Nyt,

Give this a try. If you'd like I'll bring this attachment to the next meeting in Jan 2017...

17df8e181ef12d17985ab0298c55e165.jpghqdefault.jpg

You'll need a variable speed dremel (with the flex attachment as a plus for control) so you can slow it down for balsa and bass, plus I'd recommend a fixture designed to hold either the attachment or the wood to keep it consistent and safe. I'd been looking for a solution for years and years 'cause I too have been tortured by the block and 60 grit chlorophyll based fiber grinder!

fm
 
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Nyt,

Give this a try. If you'd like I'll bring this attachment to the next meeting in Jan 2017...

View attachment 307761View attachment 307762

You'll need a variable speed dremel (with the flex attachment as a plus for control) so you can slow it down for balsa and bass, plus I'd recommend a fixture designed to hold either the attachment or the wood to keep it consistent and safe. I'd been looking for a solution for years and years 'cause I too have been tortured by the block and 60 grit chlorophyll based fiber grinder!

fm

Very cool looking attachment. What is it called?
 
no fair you having fun and such...

Just saw that its going to be mid-high 70s Christmas week in the Rio Grande Valley (old home). Beach time!

Nyt,

Give this a try. If you'd like I'll bring this attachment to the next meeting in Jan 2017...
View attachment 307761View attachment 307762
I'd been looking for a solution for years and years 'cause I too have been tortured by the block and 60 grit chlorophyll based fiber grinder!

fm

I'll gladly take a look at it if you bring it. The pictures alone aren't making the connection for me yet.

Chlorophyll based fiber grinder?
 
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Didn't get to go to the beach while I was visiting the hometown. But I did get some great 70's weather and fly rockets!
Including the first flight of the BroncBuster II!
This was launched on an old turf-farm in a floodway south of my house (and ~4 miles north of the US/Mex border).
My brother is the one you can hear in the video. The wind totally canceled out my countdown downwind.
(For any cloud watchers out there, ceiling was ~1600 ft. Well out of this range on the F50)

Details in the vid description:
[video=youtube;Ho-lBbE37G4]https://www.youtube.com/watch?v=Ho-lBbE37G4&feature=youtu.be[/video]
 
Broncbuster II is getting a nosejob, but not definitely not to take weight off.

Some time before I joined the forum, I read Tonimus's Patriot build and really liked the method he used for a variable weight emplacement. If I want to be able to fly it on small H's and still get it off the ground on F's, adjustable weight is gonna be necessary.

Thanks to Nat at Upscale CNC, I have a great set of rings and bulhkeads for 3", 2.5", and 2" Pro Series II cones. That covers the Ventris and Argent cones, but I'll need another 2.5" set for the Partizon (+AV bulkheads for the Vent/Arg/Part). Just need to adjust the holes to accept some T-nuts or weld nuts, and order some coupler nuts from mcmaster.
IMG_20170107_204755266.jpg
 
Car decided it wanted a new radiator and water pump as a late Christmas present. Thats going to eat at the rocket budget if I still want to pretend to be a responsible adult.

Fortunately I've got my Secret Santa Black Star Voyager to keep me busy for.....awhile (still slightly scared to start it). Plus this little Sequoia I got on sale at Hobby lobby. Figured I'd see if I can stuff an Estesmeter in a 13mm rocket :cool:.
IMG_20170104_191158098.jpg
Got my coupler nuts from Mcmaster and have the nose weight fixture all ready now. It's still stable with Single use G's, but if I want to put cased reloads in, I'll be able to adjust as necessary now.

And now I've got to make a decision......what 29mm hardware to invest in....
Do I gamble that CTI will get back into full production? I love the ease of use of the Cesaroni stuff
Or do I start to trying to figure out the AT luber-tubes. My only experience there is helping build my old IREC team's 75mm M. The 40-120 case has a lot of reloads, but to fly thin H's I'd need to get the RMS 29 stuff too...
1st world problems...
IMG_20170111_211238424.jpg
 
I should stop thinking this thing is finished.....I just keep messing with it.

There wasn't room for washers (other than lock washers), so I made some epoxy collar/disk/things to protect the plywood.
IMG_20170116_212435830.jpg
 
My rocket pursuits have taken a theoretical turn again.
I've been steadily cranking up the refinement of Solidworks flow simulator.
According to my uncle, rough results can be achieved with a rough mesh, you want to make sure answers are independent of the grid size. This basically means making the mesh finer and finer (increasing the number of calculation cells) until the results no longer change.

So I've been working on applying this method (video) to determine a CP location and compare it to OpenRocket. Since this is just 4 fins and a nosecone, I'm hoping that OR isn't too far off. And if I'm confident with the results, I can use the same method on ring fins or pods or other things that OR can't support.

[video=youtube;dxUf2oN_mTk]https://www.youtube.com/watch?v=dxUf2oN_mTk[/video]

Now my little Acer Aspire V has been doing its darndest, and I've used the Broncbuster II leviathan model to chart the calculated drag force and generalized CP location. Taking my uncle's advice I applied a logarithmic trend to the data to give a rough prediction of where a "perfect" calculation would get us if allowed to iterate indefinitely at a much higher cell resolution. I'm going to assume an asymptote lies real close to where y trendline is heading.

All of these runs were at 550 ft/s.
Force is total acting on the rocket along is primary axis (x)
CP distance measured from tip of nose.

The force chart is pretty much what I predicted: Flat is worse than round which isn't as good as foiled. Now I've got some numbers to answer Rex with from earlier in the thread :eek:.

The CP location chart is interesting because the rounded leading and trailing edge case has almost the exact opposite behavior when compared to the foiled or flat fins. Worth noting is that by reducing the drag effect of the fins, I may have inadvertently nudged the CP forward by reducing its interaction with the airstream. An interesting study would be on whether the increased speed due to reduced drag would compensate for the reduced stability margin.


CP BBII.PNGForce BBII.PNG

Speaking of margin, what does our faithful hobby simulator have to say about all this CP business? It says that the CP is at 30.9" from the nose tip.
First off, OpenRocket Will Not Change the CP with Fin Profile. Even with the rough results from flow simulator, there's a distinct difference between the three fin forms.
Secondly, taking the lowest asymptote from the rounded fin case, the calculated CP is ~.75" further behind OR. Foiled is ~1" behind, and flat fins are ~1.5 behind the OR position.

That being all done, I decided to represent the locations on the model itself to give a more visual relationship. Just pretend all of those lines are along the central axis (spread out vertically for clarity).

They are close to OR, but they're consistently further back. Maybe this info will allow me to use a tiny bit less nose weight for bigger motors and still maintain a static margin that's 8-15% of the rocket length.
Locations BBII.PNG

And tomorrow I'll post the results of a variable speed study!
 

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Thanks Dhbarr!
Any luck finding a CFD or modeling program to try out on your system? I recall you were interested in such things awhile ago.
(PS, how do you pronounce your handle? Its probably D.H. Barr, but in my mind it always comes out Da'barr)


As advertised, a speed analysis.
I started from the 550 f/s which is near the OR predicted top speed of the Broncbuster II on a G78 (mojave green). I chose 400 and 250 ft/s as a couple other analysis points for......reasons....which -given enough time- I could probably bluff my way through an engineering based explanation for.

Also, I only did this on the foiled fin rocket because the graph would get pretty crowded otherwise. BUT, I did reorient the model so that the 2degree off-axis flow would be parallel to one fin this time. Just to check out what the affects of the flow hitting it at a different angle may be.

Standard casesBBII 45.PNG And parallel fin case BBII 90.PNG

Predictably, the drag forces were nearly identical. The 45 degree fin case may present a little more fin area to the flow accounting for its slight increase as opposed to the 90 degree fins. Whats really cool is that the drag has almost a perfect 2nd order relationship to velocity. This is encouraging since Drag force is proportional to the Square of flow velocity.

Similarly, maybe the 90 degree case doesnt present as much fin area to the flow which is why the center of aerodynamic forces (or CP :) registers slightly further forward than the 45 degree case (~.75"). And at these subsonic speeds, the CP doesn't shift much with a change in velocity.

All in all, I've really enjoyed applying the program to my hobby and looking for analytical insight into whats going on with my rockets. When I do a trans/supersonic build, I get to do this all over again and see how Mach screws with things :cool:.
variable speed BBII.PNG
 
Thanks Dhbarr!
Any luck finding a CFD or modeling program to try out on your system? I recall you were interested in such things awhile ago.
(PS, how do you pronounce your handle? Its probably D.H. Barr, but in my mind it always comes out Da'barr)

I'll be using OpenFoam at some point. I just don't yet know enough to be aware of what to try :).

Specifically once I get a working 3FNC sub, trans, super, hyper I should be able to batch up some tube-fin variants between about M.5 and M5.

DH is usual, but da'barr is good.
 
BBII had an unfortunate run in with an antifreeze bottle while driving home from a launch that was too windy.

Put a slight crease in the tube, but a slit section of 3" mail tube, titebond II, spot putty, and a couple rounds of primer then paint and it was back in condition for Saturday.

Perfect straight flight on a G78 mojave green (click to see the flame, not sure why its sideways. Must be an iphone thing...). Estimeter called 1572, and a newly gifted altimeter 2 called it 1524. Chute release at 300' put it down about 950' away in a 10 mph wind.

One more proof flight an a high G, and then its time to give it an H!
IMG_5308.jpgIMG_20170211_143223565.jpgIMG_20170211_143227999.jpg
 
why wait, send it up!

fm

If Chris Short is going to be making his way up to us every month, I see no reason to pay shipping for something just to get it now. I'm playing the long game here.

I can pick up a G or F from the RC hobby barn if I'm really impatient. Are you going to the SLI launch this weekend? I think it's getting moved to Sunday cuz of rain Saturday
 
Agh! Yes I did.

I forgot to write up a flight report before I hit the sack.
Guess I'll do that now and add a picture tonight.
IMG_20170218_230232395.jpg

Good boost on a G77 redline (SU) to ~1410 ft. (Reconciling the Altimeter 2 and the Estemeter onboard).
Chute release popped right at 300 as set. But.......

It was early in the day and the pads hadn't been angled out to the center of the field yet. The breeze took it about 600 ft behind the pads into the top of ~60 ft tree.
Fortunately, the greenery hadn't come in yet so we could ALL see it hanging there. Also fortunate, Music City Missile Club (MC^2) has a 50 ft fiberglass pole in their trailer
Less fortunate: a 50 ft telescoping fiberglass pole is still kind of heavy and tends to bend.....a lot.

[I'll mention now that the rocket was ~35$ but it had a Chute Release and an Altimeter 2 in it (and an Estes alt, but that's expendable)]
I really should have took a picture of it up there.

Anyway, a very helpful gentleman from the club and an SLI student from Vanderbilt (and his mini-Little Giant ladder) soldiered on with me for an hour in an effort to retrieve it.

First challenge was getting the pole up the tree. We settled on resting it vertically in forks and adding sections from the bottom. We also started taping hooked branches to the end to augment its own carabineer hook (an addition from the last user) and made a kind of grappling pole. Now there's 6'7" me, standing on an 8 ft ladder, holding a 50 ft bendy-pole at arms reach waving and wiggling it, just managing to knock and poke the tube of BroncBuster II.

After about 45 minutes, my arms and shoulders were complaining, so I traded places with the student on the ladder. ~10 mins later he somehow caught the chute with the carabineer. Walked the pole down the ladder and I was able to catch it and pull. And pull. And remove telescoping sections, And keep pulling. Boy does that Pro Series II elastic stretch....... Thankfully, the elastic is stronger than the top branches and twigs.

It fell! Fins, nose and Tube body survived the final descent. The only damage is ~1/2" of zipper that was a side effect of pulling down by its elastic.
Considering there were lawndarts, missing cert flights, closure failures, and recovery system anomalies that day, I think I came out ahead.

IMG_20170220_194000308.jpg

I also flew my L1 Patriot "Big SAM" again on an H225 with the recovered JLCR. That went perfect with only a slight chipping of paint on landing. I think my air holes got gummed with paint because the Estemeter didn't read and the ALt 2 gave flight stats of: Altitude 2', Max speed 67900 mph, Max accel 0 G's, Average accel 270 G's, flight duration .5 seconds. Suuure......

IMG_20170219_133053973.jpg
 
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I've ordered a Pro29 starter set from Tbonerocketeer for pickup at the Manchester launch on Saturday. Included in that order are a pack of D10's (Little patriot and mercury redstone's gonna fly!), and ......an H90!

This'll be Broncbuster II's maiden Hi-power flight, so I wanted to start it out easy.
But if I want to sneak it past the RSO and fly Saturday, I had to work on repairing that zipper.

I cut out the offending tab and used the leftover length of Scion tubing to fill the void and stuck it in place with TBII.
IMG_20170312_202912292.jpg

Then I made a backing strip out of Scion tubing and cut a matching "keyway" in my nosecone shoulder.
IMG_20170312_205504142.jpgIMG_20170312_210157463.jpg

I'll sand it down and try blending it with CWF tomorrow. Then primer and spot putty, and eventually repainting.
I won't cry if it doesn't get repainted by Saturday. (and if I wait, I can touch up any flight marks also :)) Its weathered its launches quite well.
IMG_20170312_205111347.jpg
 
Nice repair. Good luck with the H90 flight.
 
Well, all good things must come to an end.
Now I'm really glad I didn't spend a lot of time repainting that patched zipper.

Our sod farm launch site owner preassigns our location based on his crop. Unfortunately, today the wind was not cooperating.
Chute released perfectly, but the NNW wind carried it probably a few hundred yards into ~60' trees. An hour of searching along the direction proved fruitless. (I had no idea small patches of red leaves could look so much like a PSII parachute)

In hindsight, I really should have angled the rail directly away from the woods. And waited for the wind to die down for a second. Or asked to go to the far pads lol.

Since the Scion parts package only cost ~30$, I'm really miffed about the Chute Release.

Shout out to Forever_Metal who can be clearly heard pointing out the flight deviation in the video.
[video]https://youtu.be/YoelmdAZ90Q[/video]
 
That sucks! Sorry for your loss.

Haha, thanks BD.
This isn't the first I've lost, and I have a feeling it won't be the last. This is the nature of the hobby where we turn dollars into fire and smoke (or tree ornaments)
 
Well, all good things must come to an end.
Now I'm really glad I didn't spend a lot of time repainting that patched zipper.

Our sod farm launch site owner preassigns our location based on his crop. Unfortunately, today the wind was not cooperating.
Chute released perfectly, but the NNW wind carried it probably a few hundred yards into ~60' trees. An hour of searching along the direction proved fruitless. (I had no idea small patches of red leaves could look so much like a PSII parachute)

In hindsight, I really should have angled the rail directly away from the woods. And waited for the wind to die down for a second. Or asked to go to the far pads lol.

Since the Scion parts package only cost ~30$, I'm really miffed about the Chute Release.

Shout out to Forever_Metal who can be clearly heard pointing out the flight deviation in the video.
[video]https://youtu.be/YoelmdAZ90Q[/video]

Sorry Nyt, That was a good bird.

I wouldn't count out finding it yet, though. When myself and a few others went searching for a ballistic re-entry we found 3 other rockets in the trees and were able to retrieve recovery packages. You never know.

fm
 
Looking back, there may be an advantage to using the Estes-style tri-fold mount on the PSII rockets. If stuck in a tree, there's perhaps a weak point that will fail with exposure to wind and rain and eventually drop. This happened last year at our club. There was a nice Partizon that got stuck on top of a large tree, couple months later it was found on the ground. It had separated at the tri-fold mount. Nose cone and chute are still up there but at least he got the rest back.
 
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