BT-60 / C11 / Ring Fin: How High?

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Could I ask you to run your program on the Animist 3, please? Let me know what additional data you need.

Sure... I can do that.

I'll need dimensions and materials list for every component, top to bottom,
  1. Nose Cone type (including dimensional data and shoulder data) and material,
  2. Body Tube(s) I.D. / O.D. / Length and material,
  3. Transition thickness, length, and material,
  4. Ring fin I.D. / O.D. / Height and material,
  5. Support fin thickness, length and material

and all data for the internals

6. chute diameter and material,​
7. shock chord type and length,​
8. motor tube I.D. / O.D. / Length / location in body tube and material​
9. centering rings I.D. / O.D. / thickness and material​
10. Motor size and delay​
That'll get us started.​
 
Being a student of WWII.. that fin configuration... looks familiar... 🤔
View attachment 477573
I had that issue with my helicopter rockets, which tend to be four rotor jobs as that configuration is ideal for ROTOR retention and MOTOR retention on boost (most of my previous models have no dedicated engine mount.)

https://www.rocketryforum.com/threads/swirly-nother-boring-square-helicopter-rocket.35551/
I tend to use a forward sweep on the fins now to further discourage comparison

https://www.rocketryforum.com/threads/sundancer-helirocket.153647/
 
I had that issue with my helicopter rockets, which tend to be four rotor jobs as that configuration is ideal for ROTOR retention and MOTOR retention on boost (most of my previous models have no dedicated engine mount.)

https://www.rocketryforum.com/threads/swirly-nother-boring-square-helicopter-rocket.35551/
I tend to use a forward sweep on the fins now to further discourage comparison

https://www.rocketryforum.com/threads/sundancer-helirocket.153647/

These symbols were used by native Americans.... way before Prussia and then Germany used them.

No need to avoid geometric shapes. Life goes on, no worries.
 
I'll need dimensions and materials list for every component, top to bottom,
  1. Nose Cone type (including dimensional data and shoulder data) and material,
  2. Body Tube(s) I.D. / O.D. / Length and material,
  3. Transition thickness, length, and material,
  4. Ring fin I.D. / O.D. / Height and material,
  5. Support fin thickness, length and material
and all data for the internals

6. chute diameter and material,​
7. shock chord type and length,​
8. motor tube I.D. / O.D. / Length / location in body tube and material​
9. centering rings I.D. / O.D. / thickness and material​
10. Motor size and delay​
This is far more detail than necessary to create an accurate sim.

Here is a pared-down version:
1) Rocket total mass and measured CG with no motor
2) Nose Cone shape and length (not including shoulder
3) Body tube length and diameter
4) Transition length and shape (front and rear diameter)
5) Ring fin ID/OD, width
6) Support fin thickness and shape
7) Motor position in tube
8) Motor size and delay
 
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This is far more detail than necessary to create an accurate sim.

Here is a pared-down version:
1) Rocket total mass and measured CG with no motor
2) Nose Cone shape and length (not including shoulder
3) Body tube length and diameter
4) Transition length and shape (front and rear diameter)
5) Ring fin ID/OD, width
6) Support fin thickness and shape
7) Motor position in tube
8) Motor size and delay

Far more? :dontknow:

No chute data means no way to know ground hit speed. Kind of critical, don't you think?

And it takes all of what, 15 seconds, to input that and the shock chord?

Might as well build an accurate model with all the components.

So we're left with the tedious task of measuring a nose cone shoulder....
 
Far more? :dontknow:

No chute data means no way to know ground hit speed. Kind of critical, don't you think?

And it takes all of what, 15 seconds, to input that and the shock chord?

Might as well build an accurate model with all the components.

So we're left with the tedious task of measuring a nose cone shoulder....
@neil_w
I'll input the all data in due course. I need to finish it and fly it first, and determine the best motor(s).
It'll be hard to describe the "support fins" in your familiar terms. These are actually shear panels made up of two T-sections and a panel, a jumble of different shapes and dimensions, the panel itself being .020". The whole thing is only 0.5" high by 1.0" long, and there are only three of them. If so desired, I can submit a cross section with dimensions of the T-section, and a close-up photo of the assembly.
 
@neil_w
I'll input the all data in due course. I need to finish it and fly it first, and determine the best motor(s).
It'll be hard to describe the "support fins" in your familiar terms. These are actually shear panels made up of two T-sections and a panel, a jumble of different shapes and dimensions, the panel itself being .020". The whole thing is only 0.5" high by 1.0" long, and there are only three of them. If so desired, I can submit a cross section with dimensions of the T-section, and a close-up photo of the assembly.

From my way of thinking.... the more actual data you provide, the more accurate the simulation will be.

And if you provide the data before the flight, you can use the simulation data to help determine the best motors.
 
Far more? :dontknow:
Yes.

No chute data means no way to know ground hit speed. Kind of critical, don't you think?
Not for verifying ring fin simulation model, no. I believe that's where this all started.
And it takes all of what, 15 seconds, to input that and the shock chord?
And materials, and parachute info, and centering ring info, and.... none of which affect the ascent simulation.
Might as well build an accurate model with all the components.
Depends on your objective, and especially when you're asking someone else for the information. In order to simulate the ascent characteristics, all you need are the exterior dimensions, mass and CG, and motor data. Nothing else factors in, period. It's great to add in this stuff if you want to put in the work (I certainly do in the planning stage), but it does not contribute to the accuracy of flight simulation.

Given an already-built rocket, the only things you need to know are the external dimensions, mass/CG, and motor info. Parachute is the only thing you need for descent info.
 
.... Given an already-built rocket, the only things you need to know are the external dimensions, mass/CG, and motor info. Parachute is the only thing you need for descent info.

It's not already built Neal, @Dotini already pointed that out to you.

@neil_w
I'll input the all data in due course. I need to finish it.....
 
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It's not already built Neal, @Dotini already pointed that out to you.
The rocket is already built. See multiple Animist 3 photos and descriptions on previous page of this thread. By "finish" I mean exterior finish. Since my launch session is canceled today, and my launch partner is going off on another vacation with his hausfrau, I may as well get busy writing down the data requested.
 
@lakeroadster
@neil_w


Animist 3
DSC00353.jpg
Animist 3, general data:
length, 20" from tip of cone to back edge of ring which is equal to back end of motor section tube
weight, 2.85 oz including chute, wadding, and altimeter but no motor
CG, 9.5" from tip of nose cone
Current general level of finish: spirals partially filled, nosecone slightly larger in diameter than tube (I'm currently reworking this to fit better), support fins somewhat rough

1. Nose cone, balsa, elliptical (? see pix) 3.0" length , 0.85" shoulder
2. Motor section tube, Apogee BT-50, 5.5"
Recovery section tube, Apogee, BT-55, 7.4"
Payload section tube, Apogee, BT-55, 2.9"
3. Transition, 1", balsa, 3/8" bore hole
4. Ring, 2.0" ID, 1.8" length, 0.020" thickness, PETG plastic
5. Support fins (3), ~0.50" high, 1.0" long, .020" thick PETG plastic
T-sections, Part #766 from this vendor: https://evergreenscalemodels.com/collections/14-35cm-opaque-white-polystyrene-t-shape
6. Apogee parachute, 15" printed nylon
7. Shock chord, 7', 135 lb Kevlar
8. Motor mount tube BT-20 tube, 2.75", protrudes 0.2" from base of tube, motor protrudes 0.3" from motor mount tube, centering rings .040" paper, thrust ring 0.25" green paper, Apogee retainer clip
9. Bulkhead in payload section, in Estes coupler, Qualman wood, 0.115" thick.
10. Anticipated motor selection: B4-2, B6-4, C6-3, C6-5

Need more information? Just ask.


DSC00343.jpg

I tried to make the total fin area equivalent to a 3 fin BT-55 rocket with square fins 1.5x body diameter.


DSC00347.jpg
 
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@lakeroadster
@neil_w


Animist 3
View attachment 477733
Animist 3, general data:
length, 20" from tip of cone to back edge of ring which is equal to back end of motor section tube
weight, 2.85 oz including chute, wadding, and altimeter but no motor
CG 4.1" fwd of base of recovery section tube
Current general level of finish: spirals partially filled, nosecone slightly larger in diameter than tube (I may try another one), support fins somewhat rough

1. Nose cone, balsa, elliptical (? see pix) 3.0" length , 0.85" shoulder
2. Motor section tube, Apogee BT-50, 5.5"
Recovery section tube, Apogee, BT-55, 7.4"
Payload section tube, Apogee, BT-55, 2.9"
3. Transition, 1", balsa, 3/8" bore hole
4. Ring, 2.0" ID, 1.8" length, 0.020" thickness, PETG plastic
5. Support fins (3), ~0.50" high, 1.0" long, .020" thick PETG plastic
T-sections, Part #766 from this vendor: https://evergreenscalemodels.com/collections/14-35cm-opaque-white-polystyrene-t-shape
6. Apogee parachute, 15" printed nylon
7. Shock chord, 7', 135 lb Kevlar
8. Motor mount tube BT-20 tube, 2.75", protrudes 0.2" from base of tube, motor protrudes 0.3" from motor mount tube, centering rings .040" paper, thrust ring 0.25" green paper, Apogee retainer clip
9. Bulkhead in payload section, in Estes coupler, Qualman wood, 0.115" thick.
10. Anticipated motor selection: B4-2, B6-4, C6-3, C6-5

Need more information? Just ask.


DSC00343.jpg

I tried to make the total fin area equivalent to a 3 fin BT-55 rocket with square fins 1.5x body diameter.


DSC00347.jpg

Transition length and it's shoulder lengths?

The red thing... is that a piston? What are it's components or just tell me the weight of it
 
@lakeroadster
@neil_w


Animist 3
View attachment 477733
Animist 3, general data:
length, 20" from tip of cone to back edge of ring which is equal to back end of motor section tube
weight, 2.85 oz including chute, wadding, and altimeter but no motor
CG 4.1" fwd of base of recovery section tube
CG is normally specified from tip of nose cone
 
Transition length and it's shoulder lengths?

The red thing... is that a piston? What are it's components or just tell me the weight of it
The red thing is an Estes coupler, 0.07 oz, already listed, which connects the payload section to the recovery section. It is fitted with a Qualman bulkhead, 0.05 oz, previously mentioned, and a 3/4" screw eye, 0.04 oz. There are a total of 3 screw eyes, all visible in the pic. The screw eye on the nose cone is redundant, and can be removed, unless I want to attach the altimeter to it. Normally, I attach the nose cone with strip of electrical tape, which has never failed. I've got a package in the mail which has rolls of electrical tape in 9 colors!

The 1" transition has shoulders of about 0.7".

@neil_w
Gotcha. Measured from the tip of the nose cone (which I am now sanding to fit better), the CG is about 9.5", no motor.
 
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Here's the Open Rocket Simulation....

Void. See Post #95

I had to add 0.42 ounces to the nose to get the weight correct (2.85 ounces as specified above) that added weight also corrected the CG (9-1/2" from nose as specified above).

Technical Notes:
Bruce S. Levison, specifies in the Apogee Newsletter 27 to use 6 fins to simulate the ring. That generates a "Too Many Parallel Fins" error. So I use 4 fins, but make them thicker, in order to equal the required frontal area that mimics the ring.​
In the configurations shown, I had to increase the height of the fins in order to get the rocket to be stable. I'm looking forward to seeing if Dotini's rocket is stable, or if it needs a bigger diameter ring. Something like 2-13/16" o.d. instead of 2".​

Animist 3 - TRF - Dotini Ring Fin Design.jpg
 
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Here's the Open Rocket Simulation....

I had to add 0.42 ounces to the nose to get the weight correct (2.85 ounces) which also corrected the CG 9-1/2" from nose?

View attachment 477787
Fascinating representation and predictions. I look forward to testing in the field - though that may be some days away.
I envy your resources and thank you for your efforts!

What could be the source of the weight discrepancy? The parachute does have a large brass fishing swivel, and the altimeter weighs about 0.5 oz with the pouch.
 
Fascinating representation and predictions. I look forward to testing in the field - though that may be some days away.
I envy your resources and thank you for your efforts!

What could be the source of the weight discrepancy? The parachute does have a large brass fishing swivel, and the altimeter weighs about 0.5 oz with the pouch.

Thanks. It took about 50 minutes to finalize the model and run the simulations.

As to the weight discrepancy... I don't know. If you have an accurate scale, weigh each of the pieces... and let me know what those weights are. Then we can dial in on what's happening.
 
Thanks. It took about 50 minutes to finalize the model and run the simulations.

As to the weight discrepancy... I don't know. If you have an accurate scale, weigh each of the pieces... and let me know what those weights are. Then we can dial in on what's happening.
Too bad, but the individual pieces have been glued together for several days. However, using my digital scale, I will weigh the nose cone and payload section independently from the remainder of the model tomorrow.

Thanks again for your efforts. I think they will prove to be quite impressive.
 
@lakeroadster
@neil_w

Animist 3 was tested shortly after dawn this morning at Dahl field. Wind 4mph, temperature 58 F, humidity 82%. The field was watered overnight and quite wet, so the local humidity may have been approaching 100%.

Two flights were attempted on B4-2 and B6-4. Both were completed successfully. Altitude achieved was 188' and 222' respectively. Stability was excellent, both flights arising vertically, straight up. I suppose the next steps include shortening the ring in increments until stability goes away.

Edit:
I weighed the nose cone and payload section (with altimeter and pouch) independently. They were 0.46 oz and 0.78 oz respectively
 
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Thanks. It took about 50 minutes to finalize the model and run the simulations.

As to the weight discrepancy... I don't know. If you have an accurate scale, weigh each of the pieces... and let me know what those weights are. Then we can dial in on what's happening.
I usually have to add weight to my sims after the fact. Chalk it up to glue and paint, which is almost impossible to predict beforehand.
 
@lakeroadster
@neil_w

Animist 3 was tested shortly after dawn this morning at Dahl field. Wind 4mph, temperature 58 F, humidity 82%.

Two flights were attempted on B4-2 and B6-4. Both were completed successfully. Altitude achieved was 188' and 222' respectively. Stability was excellent, both flights arising vertically, straight up. I suppose the next steps include shortening the ring in increments until stability goes away.

That's awesome. Congratulations.

Void. See Post #95

It appears the simulation is more optimistic than reality in this case, as it relates to apogee.

Motor.... Sim.... Actual... Variance
B6-4 ....... 276' .... 222' ..... 80%
B4-2 ...... 243' ..... 188' ...... 77%

But even more interesting, well to me anyways, was the simulation stated the rocket wasn't stable with the 2" I.D. ring fin. I'll do some more iterations and try to determine how to make the straight fin simulating a ring fin OR model stable by goofing with fin heights and lengths that I can somehow correlate to the actual ring fin that you have proven is stable.

Neat stuff @Dotini
 
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That's awesome. Congratulations.

It appears the simulation is more optimistic than reality in this case, as it relates to apogee.

Motor.... Actual.... Sim.... Variance
B6-4 ....... 276' .... 222' ..... 80%
B4-2 ...... 243' ..... 188' ...... 77%

But even more interesting, well to me anyways, was the simulation stated the rocket wasn't stable with the 2" I.D. ring fin. I'll do some more iterations and try to determine how to make the straight fin simulating a ring fin OR model stable by goofing with fin heights and lengths that I can somehow correlate to the actual ring fin that you have proven is stable.

Neat stuff @Dotini
The humidity was almost oppressive at the time of launch. Could that have hindered performance?
 
The humidity was almost oppressive at the time of launch. Could that have hindered performance?

I guess the quick answer is yes... like running in water verses running in air, but in reality, I can't imagine it would affect the launch much.

What's the altitude at your launch site?
 
I guess the quick answer is yes... like running in water verses running in air, but in reality, I can't imagine it would affect the launch much.

What's the altitude at your launch site?
I don't know for sure, but it's very likely no more than about 200'. Did you notice the weights posted in the edit to post #85 above?
 
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