ConeFin design

Onebadhawk
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tsmith1315 said:
I've been testing little frames to support the shroud. They're a bit fiddly until you get them secured with a dot of CA, but pretty stout after that.

These are for a 29mm tube, one from heavy mat and one from heavy paper, maybe 65lb cardstock.

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You need to PM me some dimensions too. That one looks like it would work well for the method too.

To the OP: If you want me to shut up and not bring up some dark magic method that nobody knows about, I absolutely will. My goal is to get a few people to try it and in this thread a lot of the shapes seem like they might work. I don't want to derail your thread, so again, a PM saying 'shut up' will be received kindly and I'll not at all be offended. I got stuck on some limitations of the idea and bailed out on it, but seeing the ratios I'm seeing, it might be worth looking at again to see if 15% of the time, it is a good way to go for projects people are building.

Sandy.
 
About 20 or so years ago, I got into an arguement on usenet rec.models.rockets. To prove my point (and at this time, I'm not sure what it was...) I built a rocket with base drag. I started by gluing a long launch lug at one end of an 18" piece of BT50. Whent it was dry, I stuck the tube onto a plastic funnel, lug down. I built up a cone from paper mache. I flew it a lot on lower powered 24mm RMS reloads (D9? D15?), and a few times of higher powered SU motors.. It flew really well, especially in wind. The paper mache was a lot tougher than I had thought it would be. I don't remember what happened to the rocket, and I'm sorry there aren't any pictures. I don't have any BT50 right now, or I'd build another.
 
Sandy H. said:
As mentioned in a post a bit above, I've got a method that might make !#$^%& turn to 'ahhhh' on certain types of shrouds. It is absolutely based on other people's work and is at most an incremental improvement, but the super shroud method seems to be 80% of it IMO and my method more of an iteration at best. Having said that, if you tell me the dimensions you're working with, I can draw up the shrouds, give a brief description and send you a pdf you can print to try. I will also need to know the cardstock thickness you have on hand to print, as the method refines the geometry of the patterns and thicker or thinner paper will render it useless.

The versions I laser cut work surprisingly fast, IMO. If you want to try a version that you print and cut and a version I laser cut to see if you get different results, I'm in. Just PM me the info and I'll mail something out for you to try.

Sandy.
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Well this one is rather tiny and I would like to know how to do this. But my initial test rocket is so small I am using printer paper. But I am looking to make one bigger if all goes well.
 

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tsmith1315 said:
I've been testing little frames to support the shroud. They're a bit fiddly until you get them secured with a dot of CA, but pretty stout after that.

These are for a 29mm tube, one from heavy mat and one from heavy paper, maybe 65lb cardstock.

View attachment 514274

View attachment 514276

View attachment 514277
Click to expand...
Wow that looks cool!!! I did not know cone finned rockets were a thing till now. I hope mine works and then I believe I will build one based on an 18 or 24mm tube.
 
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Long_Gone said:
Well this one is rather tiny and I would like to know how to do this. But my initial test rocket is so small I am using printer paper. But I am looking to make one bigger if all goes well.
Click to expand...
That one looks pretty good. If you don't have thicker cardstock paper, you could try an index card. You can print the transition, using the transition tool on PayloadBay.com on regular printer paper. Glue stick that to an index card, if it is large enough, or some other thicker paper. You can also make a thicker paper from a few layers of printer paper glue sticked together. Let them dry a bit, roll them up into shape before totally dry. For LPR, a glue stick is really all you need.
 
I really learned how to make conical transitions after a few Dr. Zooch kits. Smallest one I did was for the escape tower nozzles on the Saturn 1B. The Soyuz also has lots of cones that form the booster tanks and nozzles. They can be a lot of work, but practice helps, keep at it until you get the hang of it. Tweezers help, and a BBQ bamboo skewer for mashing down glue tabs inside nozzles too small for a finger tip. Very little white glue is needed for the paper joint or it can get soggy. I like using a glue stick since it is easier to control how much you put on and the thin layer stays where you put it.

Just some examples from the Apollo-Soyuz-Test-Program commemorative edition:


Screen Shot 2022-04-15 at 3.39.40 PM.png
Screen Shot 2022-04-15 at 3.40.17 PM.png
Screen Shot 2022-04-15 at 3.40.24 PM.png
Screen Shot 2022-04-15 at 3.40.47 PM.png
 
Long_Gone said:
Wow that looks cool!!! I did not know cone finned rockets were a thing till now. I hope mine works and then I believe I will build one based on an 18 or 24mm tube.
Click to expand...

Thanks! As with some of the others here, this one is the upper stage (a Sparrow missile) from a sounding rocket, an Aerobee 300.

Aerobee 300 Estes.png

Aerobee 300 Upper - Sparrow 2.png

It was intended to test the upper stage performance before incorporating it into a larger scale build. However, I'll probably back it down to a 1" diameter and use the carbon tube for something else.



Are you using a centering ring or base on the bottom of yours, or planning to leave it open?
 
A few years ago, I was just messing around with some construction paper and made this little 13 mm rocket. I call it Firefly. Rear eject feather weight recovery. It has a little bit of nose weight. I recovered the engine but never found the rocket, until a wind storm the next year when it blew out of the tree in my backyard along with all the sticks and pine cones I was picking up. Dried out pretty well, can probably survive another launch.
6C600C83-D7C6-4A3D-8CFB-29294CDB5B2E.jpeg
 
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tsmith1315 said:
Thanks! As with some of the others here, this one is the upper stage (a Sparrow missile) from a sounding rocket, an Aerobee 300.

View attachment 514412

View attachment 514409

It was intended to test the upper stage performance before incorporating it into a larger scale build. However, I'll probably back it down to a 1" diameter and use the carbon tube for something else.



Are you using a centering ring or base on the bottom of yours, or planning to leave it open?
Click to expand...
I have a centering but the transition is long.
 
I cut down a 12" Estes parachute to 6" instead of the streamer (Because My streamers were all too short)........Painted the Nose cone Yellow
Maybe we have an Easter launch.
 
Well first flight was a skywriter so I jammed some clay in the nose and it flew but was hard to see because of the snow and the chute did not open. So I need a streamer. And the damn GoPro video is only viewable on the GoPro. WTF!!!!!
Evil Knievel and Eddie Braun had issues also!!!
 
ok flew the conefin today or as I call it "The Finless Freak". It boosted perfect till it slowed down the then crazy skywriting at altitude, looked strange then ejection. No damage about 400' no altimeter will fit so it is a guess. No video did not want to mess with it. So tomorrow if the sky is not gray like today I will get the GoPro out and take a video. I am thinking as the rocket engine burns out and enters the coast phase the rocket slows down but is still traveling fast but not fast enough to be stabilized and skywrites. OR does not say this will happen, interesting. Finned rockets that I have dont do this........
 
The Finless Freak Died in a CATO incident today!
 

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amiles said:
Where did you put the CG in those sprint model for stable flight? I'm looking to build one.
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Sorry I missed your post...

The C of G was at or just a touch behind half of the overall length on all of the Sprints that I built. They all flew pretty well and were great small-field flyers, being a pretty draggy shape (at least in the subsonic realm... :p)

The CP of a cone is nominally 2/3 of its overall length from the tip, so I considered the mid length point to be the aft-most place for the CG. It took quite a bit of nose weight to get there, but it all worked out well!

Best of luck with your project and be sure to post pics of the build!

Mike
 
Mugs914 said:
Sorry I missed your post...

The C of G was at or just a touch behind half of the overall length on all of the Sprints that I built. They all flew pretty well and were great small-field flyers, being a pretty draggy shape (at least in the subsonic realm... :p)

The CP of a cone is nominally 2/3 of its overall length from the tip, so I considered the mid length point to be the aft-most place for the CG. It took quite a bit of nose weight to get there, but it all worked out well!

Best of luck with your project and be sure to post pics of the build!

Mike
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Thank you, and will do!
 

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