Re-Coil: A 3 Stage Ring Finned Rocket

[lakeroadster]

I saw a post earlier today by @Vonskii about a design by Bob Dinsmore in the Estes September 1976 Design of the Month contest.

This design is similar, but with a "slant". The plan is to make the entire ring fin with the support fins and BT-50H as a 8" long single unit. Then put that on my chop saw and slice out the individual ring fin units with the saw set at a (30 degree ??) miter. Then the individual ring fin sub-assembly's will slide over a C-50 to make the individual stages.

The Sustainer has (1) ring fin,
the 2nd Stage has (2) ring fins,
and the 3rd Stage Booster has (3) fins.

The sustainer has a rear eject spool design, and a the rocket has an 11" long payload bay.

 

[Raythain]

New lakeroadster build thread with a wild concept and clever fabrication techniques?



Although if you’re constructing the whole fin assembly as a unit, have you considered how you’ll paint the ring fin? I think most designs paint the ring fin prior to attachment.

 

[BABAR]

Not sure if you are doing a broken helix or true slanted rings.

@neil_w sent me this (btw, belated thanks , Neil! I love it, it works perfectly)

https://www.blocklayer.com/pipe-mitereng.
Not sure if this is exactly what you are thinking , Lake, but is a nice tool in the box

 

[neil_w]

I am not at all clear how you plan to do what you're saying, but I'll definitely be following along. Ask your wife to video the chop saw operation.

I can see how you'd separate the different stage assemblies with the saw, but not how you could carve out the space between the individual rings. Unless you weren't planning to actually do that.

 

[lakeroadster]

... have you considered how you’ll paint the ring fin? I think most designs paint the ring fin prior to attachment.

Just paint it afterwards. That's what I did on my Ahpla.​

Not sure if you are doing a broken helix or true slanted rings.

@neil_w sent me this (btw, belated thanks , Neil! I love it, it works perfectly)

https://www.blocklayer.com/pipe-mitereng.
Not sure if this is exactly what you are thinking , Lake, but is a nice tool in the box

True Slanted Rings... The link you posted is bad?​

​

I am not at all clear how you plan to do what you're saying, but I'll definitely be following along. Ask your wife to video the chop saw operation.

I can see how you'd separate the different stage assemblies with the saw, but not how you could carve out the space between the individual rings. Unless you weren't planning to actually do that.

To make this easier to visualize... slide all the pieces over a C-50 internal full length coupler for each stage.​

​

Miters not shown... but the rings and spacers will be mitered.​

​

 

[kjohnson]

True Slanted Rings... The link you posted is bad?​

Remove the period at the end.

 

[lakeroadster]

"The Toilet Bowel Brush" or.... "Simulation of Ring Fin Designs in Open Rocket"

Looks stable... the semi-transparent fins represent the ring fins, as defined in the above link.

 

[kjohnson]

Maybe this will help folks- cut the tube on an angle, ditch the gray extras and you have a bunch of slanted rings. Did I get it right?

 

[lakeroadster]

Maybe this will help folks- cut the tube on an angle, ditch the gray extras and you have a bunch of slanted rings. Did I get it right?

Yep.. that's the approach. Just set the tube assembly on the chop saw...

Cut, slide, repeat.​

Easy, peazy​

 

[Vonskii]

I saw a post earlier today by @Vonskii about a design by Bob Dinsmore in the Estes September 1976 Design of the Month contest.

Wow, I'm glad I shared that design the other day now! This new rocket you're cooking up looks amazing, can't wait to see how it turns out!

 

[lakeroadster]

Wow, I'm glad I shared that design the other day now! This new rocket you're cooking up looks amazing, can't wait to see how it turns out!

I'm glad too... thanks. I'm a huge fan of the designs of the 70's.

 

[BABAR]

​

True Slanted Rings... The link you posted is bad?​

​

Bad link?

Try

https://www.rocketryforum.com/threads/forgot-how-i-templated-an-offset-ring-fin.179958/
Post 2

 

[BABAR]

The sustainer has a rear eject spool design, and a the rocket has an 11" long payload bay.

wow, one of my Holy Grails.

Trying to get a zero delay motor to do TWO things at burn through,

1. Light sustainer (or if 3 or more stages, next motor). This function obviously supersedes anything else.

2. Anything else. Most commonly deploy a chute. IIRC your Ahpla was tumble recovery. How do you confidently light the sustainer AND eject the spool with a single zero delay motor? I have ideas that would prooooobaaaably work 70-80% of the time, but I haven’t come up with one I felt was in the 98-99% range. Maybe your fuse cords could do it.

My go to long gap booster chute deployment method has been a second clustered motor, usually something small like an A8-3 but a. 13 mm motor would work, with a pod. That obviously won’t fit the plan for this bird.

Btw, if you DO use a spool , either go with a streamer or wrap the chute kind of tight (opposite of what you normally do.). I used a pod technique once where the booster pulled the chute out of a pod in the sustainer at separation. Nearly instantaneous chute deployment. Did I mention this was activated at separation, when rocket (or at least booster) was at max Velocity? Snapped 7 of 8 shroud lines. Need something to slightly delay deployment. Not an altimeter delay, just something that takes 2-3 seconds. Often the booster is STILL climbing after separating.

I am curious also, is there a reason simple tumble recovery of the two boosters isn’t reasonable?

 

[lakeroadster]

wow, one of my Holy Grails.

Trying to get a zero delay motor to do TWO things at burn through,

1. Light sustainer (or if 3 or more stages, next motor). This function obviously supersedes anything else.

2. Anything else. Most commonly deploy a chute. IIRC your Ahpla was tumble recovery. How do you confidently light the sustainer AND eject the spool with a single zero delay motor? I have ideas that would prooooobaaaably work 70-80% of the time, but I haven’t come up with one I felt was in the 98-99% range. Maybe your fuse cords could do it.

My go to long gap booster chute deployment method has been a second clustered motor, usually something small like an A8-3 but a. 13 mm motor would work, with a pod. That obviously won’t fit the plan for this bird.

Btw, if you DO use a spool , either go with a streamer or wrap the chute kind of tight (opposite of what you normally do.). I used a pod technique once where the booster pulled the chute out of a pod in the sustainer at separation. Nearly instantaneous chute deployment. Did I mention this was activated at separation, when rocket (or at least booster) was at max Velocity? Snapped 7 of 8 shroud lines. Need something to slightly delay deployment. Not an altimeter delay, just something that takes 2-3 seconds. Often the booster is STILL climbing after separating.

I am curious also, is there a reason simple tumble recovery of the two boosters isn’t reasonable?

Only the sustainer has the rear eject spool design.

The boosters are tumble recovery and the motors hang out the back quite a bit to hopefully take the brunt of the ground hit. But the 4" rings are 1/16" thick, and the ring fin supports are papered 1/8" thick basswood.

​

 

[billpr]

I saw a post earlier today by @Vonskii about a design by Bob Dinsmore in the Estes September 1976 Design of the Month contest.

This design is similar, but with a "slant". The plan is to make the entire ring fin with the support fins and BT-50H as a 8" long single unit. Then put that on my chop saw and slice out the individual ring fin units with the saw set at a (30 degree ??) miter. Then the individual ring fin sub-assembly's will slide over a C-50 to make the individual stages.

The Sustainer has (1) ring fin,
the 2nd Stage has (2) ring fins,
and the 3rd Stage Booster has (3) fins.

The sustainer has a rear eject spool design, and a the rocket has an 11" long payload bay.

View attachment 591941

Like the design. I'm wanting to build th 3 stage ring rocket from Estes MRN. Can't find the 3/8 inch rings. Gonna try to cut down a 33/4 inch BT-101.

 

[jqavins]

Not sure if you are doing a broken helix or true slanted rings.

OK, now I want to make a helical fin rocket, multistage or not. The laser cutter at my near(ish)by maker space has a rotary positioner, so cutting the helix would be the easy part. Positioning the pylons just right would be the trick, but I could use the same laser cutter to make marks on both the helix and the body tube.

Now, back to your regularly scheduled LakeRoadster build.

 

[lakeroadster]

OK, now I want to make a helical fin rocket, multistage or not. The laser cutter at my near(ish)by maker space has a rotary positioner, so cutting the helix would be the easy part. Positioning the pylons just right would be the trick, but I could use the same laser cutter to make marks on both the helix and the body tube.

Now, back to your regularly scheduled LakeRoadster build.

https://www.rocketryforum.com/threads/lakeroadsters-helical-fin-rocket.172143/​

 

[jqavins]

Cool, but not what I mean. Take a big tube, maybe 3". Make a helical cut at, oh, let's say, 2" up the length for each full turn around. Then make another such cut, offset from the first by, let's say, 1/2" vertically. Leaving you the world's thinnest curly fry.

 

[BABAR]

OK, now I want to make a helical fin rocket, multistage or not. The laser cutter at my near(ish)by maker space has a rotary positioner, so cutting the helix would be the easy part. Positioning the pylons just right would be the trick, but I could use the same laser cutter to make marks on both the helix and the body tube.

Now, back to your regularly scheduled LakeRoadster build.

I think that @neil_w Starship Avalon had segmental helical fins. I thought that alone presented engineering and craftsmanship challenges of high level to form and particularly mount those complex curved fins so surfaces were properly lined up with airstream.

https://www.rocketryforum.com/threads/starship-avalon-build-thread.136389/

 

[jqavins]

Indeed, almost as soon as I wrote post #16 I thought of Starship Avalon. That has three different pieces; they're nearly vertical, and each one covers about a third or less of the circumference of the imaginary tube they lie on. I'm talking about a single piece, being nearly horizontal, and wrapping two or three times around, like a screw thread or a curly fry.

Enough threadjcking.

 

[neil_w]

Those were indeed helical... but cutting a curly fry out of a single piece of tubing would be an altogether different challenge. Lacking a laser cutter with a tube-cutting attachment, I would foresee a long and careful hand-cutting adventure. Would like to see it.

Since discovering the ability of OR to visualize weirdly-carved body tubes, I'm very interested in this sort of thing.

This took some effort, but worth it. No one has more fun abusing OR than I do.

 

[jqavins]

Yes, that's it exactly.

I wouldn't try it without a laser cutter, but I can imagine how one might. Start with a printed pattern wrapped around a mandrill. Cover the mandrill and wrap in something "glue proof", such as by painting it with molten wax that will soak in leaving the pattern visible. Then use straight strips of paper, moistened with glue of some sort, and lay them over the pattern. Build up sufficient thickness by adding layers. Wrap it tightly in cling wrap while the glue dried, cures, or otherwise does its thing. Apply filler and sand as necessary.

To do it with a laser cutter, I would stiffen the tube I'll be cutting up with a nice thin CA soak and fill the spirals before cutting. That means cutting through mixed materials, which means the best cutter settings won't be on the cheat sheet, but it should work out OK all the same. Experimenting on CA hardened scrap tube would be in order.

 

[stealth6]

I love your build threads.

s6

 

[DaHabes]

I'm glad too... thanks. I'm a huge fan of the designs of the 70's.

I'm a fan as well. I actually used the same plan and built it with two sets of boosters - one set for C11's & D12's and one set for E12's. Let's me mix and match motors - 27 combinations if my math is right...

 

[billpr]

Like the design. I'm wanting to build the 3-stage ring rocket from Estes MRN. Can't find the 3/8-inch rings. Gonna try to cut down a 33/4-inch BT-101.

Sounds like a great idea. Might do it that way. saves time and will be cut right. Thanks .

 

[Hobie1dog]

We need to have a "Design of The Year" , and I nominate this one.