Another finless rocket

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Sooner Boomer

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I didn't want to hijack the other thread. This is the build sequence for a finless rocket I designed and built last August. Hopefully I'll get to fly it before this August. One main difference is that it's designed to be tube launched, rather than off a rod/rail. I've got a nice 4' heavy walled cardboard tube for these projects.
 

McKailas Dad

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Tube launched? Is that similar to a piston launcher, and/or would it have the same affect?
 

Sooner Boomer

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The build:

From the beginning, I wanted to build the rocket with an ejection baffle. So let's start with the engine mount tube.
This is a BMS foil-lined BT-50 tube.

01 engine tube.jpg

And where the engine mount will go

02 baffle shell.jpg

and glue the engine mount inside (it really is square).

03 baffle inside.jpg04 baffle assy.jpg

the inside top of the baffle

05 top of baffle.jpg

with the top of the baffle glued on

06 top of baffle 2.jpg
 
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Sooner Boomer

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Next comes the assembly of the body

It's got a cone at the tail of the main body to help induce flow into the lower ring fin.

07 tail cone.jpg

I'm trying to save some money by making the lower ring fin from card stock

08 fin wrap.jpg

The tail cone is glued on

09 rocket body.jpg

Then I added struts and glued the ring fin on

10 mounting struts.jpg11 nozzle-ring.jpg


completed rocket

12 assembled.jpg

aft view, you can see the baffle...

13 aft view.jpg

(yeah, the struts are not perfectly tangental to the body tube)

I'll get back to this thread as soon as I can launch!
 

Glideroc

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image.jpg

I thought up one of these back in 1992 or so. I built two three rail launchers. The first was with all circular formers (six) and a framework to carry them. A LOT like this! The framework was not strong enough to keep the gauge of the aluminum C rails. So, I built one with square 3/4" Baltic birch formers and a square diagonally strutted frame. It showed promise and I made a couple of finless models from LOC 38mm tubing with a pair of pan head screws per rail. 14 years ago I moved to Kansas City where I now live and packed it away. Maybe I'll restart the project some day.

David Bucher "California Dave"
TRA 829
NAR 47674

PS, I don't know the origin of this pic but for my own project, SURPRISINGLY like this, I had planned a Vulcan Systems H300 buttkicker to see how it would work...and straight up, too!
 

rstaff3

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Cone fed GDS...cool! I'm anxious for the flight report.
 

KenECoyote

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Wow! Great build and very interesting design! So why would this need to be tube launched?
 

Sooner Boomer

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Wow! Great build and very interesting design! So why would this need to be tube launched?
It doesn't "need" to be. I just like to do tube launch designs. If this proves to be unstable, or marginally stable, I'll add fins and a launch lug, and launch from a rod.
 

Dotini

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Next comes the assembly of the body

It's got a cone at the tail of the main body to help induce flow into the lower ring fin.

View attachment 281504

I'm trying to save some money by making the lower ring fin from card stock

View attachment 281505

The tail cone is glued on

View attachment 281506

Then I added struts and glued the ring fin on

View attachment 281507View attachment 281508


completed rocket

View attachment 281509

aft view, you can see the baffle...

View attachment 281510

(yeah, the struts are not perfectly tangental to the body tube)

I'll get back to this thread as soon as I can launch!
Very interesting. Have you given this a swing test?

I've completed but not yet launched 3 similar experimental designs.
 

Charles_McG

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I love thread necromancy.

I think if I were attempting this, I'd airfoil the inner surface of the aft tube - like a Dyson fan. Or at least approximate it with an inner ring, like an X-Zylo.

My experience with ring wings is that they work under a very limited range of angle of attack.

Wouldn't a tube launcher for this be counter-productive? Inside the tube, the body is pushing the air out ahead of it with no way to backfill. The motor exhaust may well pressurize the tube aft of the body - but the flow over the aft ring would be static or turbulent until it hit free air.
 

Dotini

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I think if I were attempting this, I'd airfoil the inner surface of the aft tube - like a Dyson fan. Or at least approximate it with an inner ring, like an X-Zylo.
I did something like this on two of mine. But instead of airfoiling the inner surface of the aft tube, I added a small flange around the base of the outer side of the tube. I'm thinking this will also be helpful with my tumble recovery, as it will descend stern first.
 

Sooner Boomer

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I love thread necromancy.
Braaaaiiinnnnssss.......
I think if I were attempting this, I'd airfoil the inner surface of the aft tube - like a Dyson fan. Or at least approximate it with an inner ring, like an X-Zylo.

My experience with ring wings is that they work under a very limited range of angle of attack.

Wouldn't a tube launcher for this be counter-productive? Inside the tube, the body is pushing the air out ahead of it with no way to backfill. The motor exhaust may well pressurize the tube aft of the body - but the flow over the aft ring would be static or turbulent until it hit free air.
I just like tube launching rockets. I was thinking of adding a small skirt that would insure rocket tube would seal inside the tube; would give better pressurization. The tube is only 3 or 4 feet long. I don't think the air on top of the rocket while in the tube would be much of a problem. This got put aside and I'm just now getting back to it. I should be flying it within a couple of months (if the wind would ever die down on launch days!).
 

KenECoyote

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Very interesting. Have you given this a swing test?

I've completed but not yet launched 3 similar experimental designs.
From what I recall about GDS, the motor thrust/exhaust itself helps to pull air over the rear ring "fin" which is out of the normal flow of air, so a swing test wouldn't replicate what happens under thrust.
 

Dotini

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From what I recall about GDS, the motor thrust/exhaust itself helps to pull air over the rear ring "fin" which is out of the normal flow of air, so a swing test wouldn't replicate what happens under thrust.
Agreed. But since my model (the "Animist") did pass the swing test, does that mean it's overstable and I should try to reduce the diameter and/or length of the ring until it fails the swing test? My ring diameter/length is 1.6" x 1.5", my main body diameter is 0.78" reducing to 0.5", oa length is 8.5".
 
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KenECoyote

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Agreed. But since my model (the "Animist") did pass the swing test, does that mean it's overstable and I should try to reduce the diameter and/or length of the ring until it fails the swing test? My ring diameter/length is 1.6" x 1.5", my main body diameter is 0.78" reducing to 0.5", oa length is 8.5".
I would expect that it being stable during a swing test is good and indicative of it being stable during the coast phase. :)
EDIT: Missed that you asking about a ring fin rocket vs finless GDS.
 
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jqavins

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My ring diameter/length is 1.6" x 1.5", my main body diameter is 0.78" reducing to 0.5"...
With the ring more than twice the main tube diameter, doesn't that make it a regular ring fin, not GDS? That'd be why it passed a swing test.
 

Dotini

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With the ring more than twice the main tube diameter, doesn't that make it a regular ring fin, not GDS? That'd be why it passed a swing test.
I haven't found the regular ring fin design yet. I'd love to see it! I'm just building fun newbie experiments at the moment. GDS I never heard of til now.
 

KenECoyote

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With the ring more than twice the main tube diameter, doesn't that make it a regular ring fin, not GDS? That'd be why it passed a swing test.
Oh, I missed that...I thought this was all a finless thread.
 

KenECoyote

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Dotini

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Here's also my own sketch of what I think happens to help keep GDS stable during boost.
View attachment 453455
Very interesting!

In part, Van Milliigan said this:​
The holes letting air into the
sides of the rocket should provide
enough flow area to match the
cross-sectional area of the turbulent
mixing cone where the cone leaves
the body tube. For example, if the
end of the body tube is 2D down-
stream of the rocket nozzle, then the
diameter of the mixing cone will be
approximately half the diameter of
the body tube (D/2) where the flow
leaves the body tube. The cross-
sectional area of the mixing cone
where the flow leaves the body tube
will be approximately π(D/2)2÷ 4 =
0.20 x D2. The total area of the holes
admitting ambient air thru the sides
of the rocket should then equal at
least 0.20 times the square of the
diameter of the body tube. For differ-
ent distances of the end of the body
tube downstream of the engine, the
total area of the holes required will also be different.


In my little series of Die Glock models, my ring is approximately 7 to 8 body tube diameters downstream of my rocket nozzle, and is about 2x the body tube in diameter. There is nothing between the station line of the nozzle and the station line of the ring except 4 slender birch dowels.
 

jqavins

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If you attached the ring at the aft end of the body tube, that would be an ordinary ringtail. (I've been saying ring fin, but ringtail is the better term.) With the ring set back from the tube, I guess that's still a ringtail. If it has another name, I don't know it.
Red-Star.jpg
In this design, the pylons that attach the ring might make for sufficient fins by themselves, but the pylons could be just dowels and the ring would do the job.
 

Dotini

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If you attached the ring at the aft end of the body tube, that would be an ordinary ringtail. (I've been saying ring fin, but ringtail is the better term.) With the ring set back from the tube, I guess that's still a ringtail. If it has another name, I don't know it.
View attachment 453499
In this design, the pylons that attach the ring might make for sufficient fins by themselves, but the pylons could be just dowels and the ring would do the job.
Thanks, that is good to know! Perhaps I can now reduce the length of my ring! But, err, is that Red Star a well proved flying rocket? I went online to try to buy one, but it seems they are discontinued. IMHO, A rocket that uses both fins and a ring is like the man who wears both a belt and suspenders. :)

As far as nomenclature goes, I'm thinking about using the term venturi. I'm making efforts to extract/accelerate air from the ring by use of a small flange, or lip - possibly conical - at the outside base of the ring.

I really appreciate all the great information and help I'm getting from this excellent forum.
 

jqavins

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It's a model from Apogee Components. It's currently out of stock, not discontinued. If you don't know Apogee, poke around their web site for a while and sign up for the news letter.

I'm intrigued by your description. Pictures please?
 

KenECoyote

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As far as nomenclature goes, I'm thinking about using the term venturi. I'm making efforts to extract/accelerate air from the ring by use of a small flange, or lip - possibly conical - at the outside base of the ring.
Yes, pictures/sketch please! :)
 

Dotini

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It's a model from Apogee Components. It's currently out of stock, not discontinued. If you don't know Apogee, poke around their web site for a while and sign up for the news letter.

I'm intrigued by your description. Pictures please?
I'm extremely embarrassed to report that due to my age (72) and Paleolithic nature, I do not possess the technology to take and send a picture. I've asked my fellow Boeing retiree Blair, a knowledgeable engineer and close friend, to teach me how to send pictures. I'm going to do this thing! :mad:

The good news, all three of my ringtail models are complete, with finish and decals, and are ready for launch. I hope to accomplish that, with Blair's help and good weather, sometime in the next 10 days.
 
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