That would be the perfect name for the final model, if there is one. Just have a towel around at all times when launching.
"Finless" Rocket Design - Ram Air Intake Stabilization?
- Thread starter KenECoyote
- Start date
Help Support The Rocketry Forum:
That would be the perfect name for the final model, if there is one. Just have a towel around at all times when launching.
GlenP
Well-Known Member
- Joined
- Oct 3, 2014
- Messages
- 3,066
- Reaction score
- 1,580
That's what a I was trying to suggest earlier, make something like the finless rocket with the cone transition at the base, then put the larger air fin shroud around it. Great test flights, you are charting new territory.
https://www.rocketryforum.com/showt...Induction-Stabilization&p=1540979#post1540979
I'd say that they WERE totally harmless. Three points don't predict the future, however.
Yup! Agreed!
I basically snuck in the quick tests in the little window I had available...the snow storm as well as this week being above freezing really made things difficult testing-wise. I've already started making a new shroud for the 18mm one. I think the problem with the initial designs is that there isn't enough air going through the shroud to be enough to stabilize the rocket, so they acted almost like a rocket with fins which are too small...plus that one with a hole on the bottom. LOLThat's awesome! Thanks! I don't mind at all...all pics I put up are to share anyway.
I LOVE that! I'll name the next one "Mostly Harmless"!
Great minds think alike!
Sorry...I didn't realize I hadn't replied to that post. I did read it and thought I had replied...I did earlier consider having a cone base at the bottom of the shroud after my first "curly-q" sketch since it makes more sense to have the air funneled down and it should help the air transition from vertical to horizontal (I might have even posted it, but don't recall...one of many thoughts I've had on this design). However for first prototypes I figured it made more sense for me to give them flat bases for ease of building/KISS. My current thought is that the shrouds aren't big enough relative to the rocket to send enough air out for the "air fin" effect. I'm making a BT60 shroud for the 18mm "RAIS'N Heck" and will also try to add on a cone base to the shroud to make the air flow more efficient (could be some turbulence within the shroud messing things up a bit. I may build a few versions again before the next round of testing, so please be patient and stay tuned!
Also the "Mostly Harmless" version will likely be more like a saucer with an extended base around it as well as inlets in the top. This one should take advantage of base drag. I think. :wink:
Sketch:
Funny thing is that I think this design has a LOT of rocket science going on...saucer, base drag, air fins, wedge/cone base and even some spool action! :w:
Sketch:
Funny thing is that I think this design has a LOT of rocket science going on...saucer, base drag, air fins, wedge/cone base and even some spool action! :w:
Last edited:
Charles_McG
Ciderwright
Have you considered trying to airfoil the inner, upper lip of the shroud? I'm thinking along the lines of the hand thrown flying cylinders (like a zylo) or the dyson bladeless fans. The air moving over the airfoil creates a low pressure region inside the ring and 'multiplies' (to use the dyson terminology) the air flow through it.
Whoa. :y:
I'm starting to wonder if the fin holes being "slots" actually matters. In your sketch I could imagine them being round holes. In fact, I like the idea of three small tubes with capped ends and side ports, then the whole thing covered with a shroud (and that crazy nose thing), and then you'd just have to find a way to squeeze and engine in there. Or maybe that would be too much like tube fins for your liking, but still weirdly different.
Just ponderin'.
rstaff3
Oddroc-eteer
- Joined
- Jan 17, 2009
- Messages
- 11,763
- Reaction score
- 44
Also the "Mostly Harmless" version will likely be more like a saucer with an extended base around it as well as inlets in the top. This one should take advantage of base drag. I think. :wink:
Sketch:
Funny thing is that I think this design has a LOT of rocket science going on...saucer, base drag, air fins, wedge/cone base and even some spool action! :w:
Awesome looking design but it almost looks stable without any fancy schmancy ducting. You should build a solid version of the same dimensions, just to check.
Great idea! However I think that may be best as as separate new design odd-roc...one where maybe the ring is the bigger proportion of the rocket and the motor and short bt is attached in the center (maybe with thin rods or wire)...almost like the space station in 2001 Space Odessey.
Sounds awesome!I think slots make more sense than holes since slots would more likely have the wind pattern as a flat wall of air (like a fin) rather than a rod/column of air (like dowels). Round holes may work too, but from what I've seen with rockets, the ones with dowels for stabilization need longer dowels.
Thanks! I agree with your observation...in fact, my goal now is to make it more stable (as GlenP suggested earlier) and then slowly scale up to try to work off a base of success. Additionally, I can also tape off the outlets to see the difference. From my experience with cup rockets, the design without the outlets should work with enough nose weight; however it usually ends up being squirrely and my goal of the outlets is to stabilize the back end.
What would be really cool is that if I could get it to work reasonably well, perhaps it can almost look like one of these (I know...daydreaming
):
BTW - The exhaust nozzle on this one would likely also add GDS to the mix!
rstaff3
Oddroc-eteer
- Joined
- Jan 17, 2009
- Messages
- 11,763
- Reaction score
- 44
Great idea! However I think that may be best as as separate new design odd-roc...one where maybe the ring is the bigger proportion of the rocket and the motor and short bt is attached in the center (maybe with thin rods or wire)...almost like the space station in 2001 Space Odessey.
I think slots make more sense than holes since slots would more likely have the wind pattern as a flat wall of air (like a fin) rather than a rod/column of air (like dowels). Round holes may work too, but from what I've seen with rockets, the ones with dowels for stabilization need longer dowels.
Thanks! I agree with your observation...in fact, my goal now is to make it more stable (as GlenP suggested earlier) and then slowly scale up to try to work off a base of success. Additionally, I can also tape off the outlets to see the difference. From my experience with cup rockets, the design without the outlets should work with enough nose weight; however it usually ends up being squirrely and my goal of the outlets is to stabilize the back end.
What would be really cool is that if I could get it to work reasonably well, perhaps it can almost look like one of these (I know...daydreaming
BTW - The exhaust nozzle on this one would likely also add GDS to the mix!
He he he...
Oooh, add extra ducts next to your air fin slots and feed them into the cone...RAISGDS! Another way to get rid of the wobble is to put more motor in there.
My end goal is to make one like that sketch with inlets in the nose cone, but longer. Let's see how far I can take this...
Why not! :grin:
GlenP
Well-Known Member
- Joined
- Oct 3, 2014
- Messages
- 3,066
- Reaction score
- 1,580
I like it! You could even use profile fins in the shape of a nose cone, make the entire top an inlet.
Maybe try a shorter through tube with rear-eject, you can put the recovery device in the base cone transition near the engine mount.
Great idea! That was actually one of my earlier thoughts; however I wanted something more like a nose cone. Additionally, I initially wanted nose eject and with the larger cone, I can still do that with a smaller balsa plug that fits into the bt and is fixed into the larger nose cone. Additionally making a scratch build rear-eject would be more difficult for me (although I have a little experience with rear ejection rockets). However you may be on to something with the rear eject for this if this requires a lot of nose weight.
My current main end goal is to create a longer rocket without excessive nose weight, which has a stable smooth flight without fins...much like the one I pictured earlier here (or similar where the nose is like that in the most recent sketch):
Right now I'll work with larger shrouds and bigger outlets to follow the version I had the most success with. Next, I'll try longer shrouds and then maybe the shorter wider version I sketched today. Ideally I would build them closer to other designs (such as saucer, squat, cone base, etc.) and then slowly increase the shroud effect so I can figure what works best and still flies stable. Unfortunately for me I have a full time demanding job (today definitely had emphasis on "demanding") and so my build and launch times are limited. Others should feel free to try some of these designs and provide feedback since many of us East Coasters are currently dealing with less than ideal launch conditions. :wink:
Just a quick note that I got around to cutting the first shroud to the correct length and so here is the mock up of what I'll be flying first. Should be pretty close to what I'll end up with:
(I've also updated the pic in the OP since this is a better representation of what I want to first test.)
neil_w - Any armored bunker thoughts for this one? :wink:
Just make very sure you are completely alone or with as few people in the area as possible. This type Odd-Roc MUST be launched in a close to isolation as practical. As FAR away from all unaware persons and property as you can.
Frankly; After looking at all your "Data" I can't find a single profile where your BrainSim will be anything other then a Skywriting, snaking Crash waiting to happen. Hate to be a downer but We use fins for a reason. we don't have the luxuary of internal guidence and what you have proposed has neither the ram air area or speed needed accomplish the intended flight profile. Proceed at your own risk..... By ourself PLEASE.
Take a video of the launch I can't wait to see this. Experimenting is fun. Any date for the launch. Bring your friends and family and you'll spark a love for rocketry in there hearts... Or just do what you want.
Thanks for your concern John! Yes, given what others were saying, I thought it wiser to go small scale for first tests and launching alone at first. Also another reason I've changed to plan to start with less "RAIS" effect and more of the other known designs and slowly adjust. Likely nothing above an A8 motor until I can come up with a design that doesn't skywrite and then has repeated safe flights. My personal plan is to launch off the lake in my back yard once it freezes over enough again...I have pretty much acres to myself then.
I've seen really bad accidents and have also avoided really bad accidents, so I'm always aware that things can go wrong (one of my personal preoccupations is error reduction)...often the best way to avoid them is to realize they can happen and to take proper safety measures.
BTW- that first pic was just a brainstorm and I now know that shroud is much too small for that rocket.
LOL! Patience young padawan!
The tests as noted will be well-thought out and methodical (at least to me
). I'll tests a bunch first and report back. After I get a design that works well enough, I'll try to have my wife or friend video (too tough trying to launch and video a tiny rocket at the same time and I should be focusing on the launch and tracking anyway). I'm taking this slow and patient for now, which I think is a good thing.
Given my OCD and stubbornness, I'll likely eventually make it "work"...it may not work that well*, but I think I'll get it to work.
*I'm starting to think that this design may end up adding a lot of drag in order to gain enough stability (may also need higher lift-off speed). Fins are efficient and widely used for a reason.
Thanks for your concern John! Yes, given what others were saying, I thought it wiser to go small scale for first tests and launching alone at first. Also another reason I've changed to plan to start with less "RAIS" effect and more of the other known designs and slowly adjust. Likely nothing above an A8 motor until I can come up with a design that doesn't skywrite and then has repeated safe flights. My personal plan is to launch off the lake in my back yard once it freezes over enough again...I have pretty much acres to myself then.
I've seen really bad accidents and have also avoided really bad accidents, so I'm always aware that things can go wrong (one of my personal preoccupations is error reduction)...often the best way to avoid them is to realize they can happen and to take proper safety measures.
BTW- that first pic was just a brainstorm and I now know that shroud is much too small for that rocket.
Just one more thing to think about. Once these projectiles reach burnout they will also loose whatever sight "Ram Air" stability, at that point they will be skywirting all over the sky durning the entire coast phase which as I'm sure you realize is Most of the flight.
There have been many attempts at flying Finless Model Rockets, Cone shape, Double Taper Cones, and many Ram-Jet options. All met with the same end. Sometimes Passable powered segment, Awful coast phase and recovery segments. Continuing the experiment as ODD-ROC research is great as long as it is kept out of the PUBLIC launch enviroment. Build and Test all the Ram-Air models you want in ISOLATION to keep the Hobby safe.
Thank You
Got some last "thin ice" launches in (50F and sunny with ice melting quickly!) - where the biggest risk isn't the danger of the rocket to others...it's the ice for me! :wink:
The "Look! No fins!" rocket was left as is; however I've opened up the outlets on the "Well-DeFinned" rocket and created a larger shroud with a cone base for the "RAIS'n Heck" rocket.
"Look! No fins!" Launches #2 & #3 (1/2A3-2T):
Rose up quickly; however it was small and very hard to track. Boost was good and pretty straight; however I thought it went unstable right after boost. I later realized it was likely the delay phase and the rocket is getting squirrely after boost (again, hard to tell due to size and speed). Additionally, the motor ejection shotguns the rocket away making for very difficult recovery/finding. I almost lost it on launch #2 and finally lost it on #3. Oh well.
(Note the lack of anyone around...except for one crazy rocketeer on the ice!) :grin:
EDIT: I noticed in the 2nd pic that the rocket motor was actually pulled a bit out of the rocket...likely not good for the motor to ram up as it's lit...may explain some of the squirrellyness.
The "Look! No fins!" rocket was left as is; however I've opened up the outlets on the "Well-DeFinned" rocket and created a larger shroud with a cone base for the "RAIS'n Heck" rocket.
"Look! No fins!" Launches #2 & #3 (1/2A3-2T):
Rose up quickly; however it was small and very hard to track. Boost was good and pretty straight; however I thought it went unstable right after boost. I later realized it was likely the delay phase and the rocket is getting squirrely after boost (again, hard to tell due to size and speed). Additionally, the motor ejection shotguns the rocket away making for very difficult recovery/finding. I almost lost it on launch #2 and finally lost it on #3. Oh well.
(Note the lack of anyone around...except for one crazy rocketeer on the ice!) :grin:
EDIT: I noticed in the 2nd pic that the rocket motor was actually pulled a bit out of the rocket...likely not good for the motor to ram up as it's lit...may explain some of the squirrellyness.
Last edited:
"RAIS'N Heck" Launches #2 and #3 (A8-3):
I'll likely detail the new shroud at a later time; however for this one the base is a cone and the outlets were cut very large (I was planning on later adding another tube around it to serve as adjustable outlet sizing by rotating and taping in place. So for now, the outlets are very large.
For launch #2, I used a heavier nose cone in addition to the larger outlets. Rocket rose up decently; however it didn't go very high and arched over and deployed about 50' AGL. Of note is that I angled the rod more toward my yard rather than out to the ice.
Video link: https://www.youtube.com/watch?v=del4kM4vL0g&feature=youtu.be
***Trying to get video embedded...will edit/update once straightened out.***
Launch #3 wasn't good...I switched to a lighter nose cone figuring the last launch wasn't too high due to the weight. Rocket went unstable for a bit and did some slow "lobbing" swirls and came down not too far away. Post-flight inspection didn't look good...the shroud was broken at the bottom and the bt had shoved itself into one of the inlets between 2 fins. Further thought is that there might have been some slight damage to the bottom joint from the last hard landing (rocket hit the shed and landed on rocks). I'll switch the nose back to the heavier one and reglue the shroud for the next time (will likely also have the outlet adjuster tube in place by then).
*Of note is that when these rocket designs go unstable, it's fairly uneventful. Just some wiggling or twisting and lobbing...nothing dramatic at all. Worst part is the ejection closer to ground level. YMMV
I'll likely detail the new shroud at a later time; however for this one the base is a cone and the outlets were cut very large (I was planning on later adding another tube around it to serve as adjustable outlet sizing by rotating and taping in place. So for now, the outlets are very large.
For launch #2, I used a heavier nose cone in addition to the larger outlets. Rocket rose up decently; however it didn't go very high and arched over and deployed about 50' AGL. Of note is that I angled the rod more toward my yard rather than out to the ice.
Video link: https://www.youtube.com/watch?v=del4kM4vL0g&feature=youtu.be
***Trying to get video embedded...will edit/update once straightened out.***
Launch #3 wasn't good...I switched to a lighter nose cone figuring the last launch wasn't too high due to the weight. Rocket went unstable for a bit and did some slow "lobbing" swirls and came down not too far away. Post-flight inspection didn't look good...the shroud was broken at the bottom and the bt had shoved itself into one of the inlets between 2 fins. Further thought is that there might have been some slight damage to the bottom joint from the last hard landing (rocket hit the shed and landed on rocks). I'll switch the nose back to the heavier one and reglue the shroud for the next time (will likely also have the outlet adjuster tube in place by then).
*Of note is that when these rocket designs go unstable, it's fairly uneventful. Just some wiggling or twisting and lobbing...nothing dramatic at all. Worst part is the ejection closer to ground level. YMMV
Last edited:
"Well De-Finned" Launches #2 and #3 (1/2 A3-2T):
I've saved the best for last! :grin:
Launch #2 was beautiful! I didn't video it myself, but got a look from under as it rose straight up, over on the delay and ejection and came back down not too far away. Very nice launch!
Video Link: https://www.youtube.com/watch?v=Cp0HLCHuFGs&feature=youtu.be
Launch #3...tried again to make sure...judge for yourself.
Video Links (note the wind sent it over to the right; however the rocket didn't noticeably weathervane and instead drifted to the right):
https://www.youtube.com/watch?v=qycwPCPfZPw&feature=youtu.be
https://www.youtube.com/watch?v=xrgaIUVnC8w&feature=youtu.be
I would consider "Well De-Finned" to be a successful design! I'll have to do more tests with the others; however it seems to be a very difficult mix to figure out successfully. Given that the ice will likely be gone after today, I'll have to launch elsewhere and this will be a bit on the back burner for now.
One thing no one picked up on was the modular construction I had on these rockets. I don't recall having heard/seen anything on this other than an article in Sport Rocketry where there was a very expensive modular rocket. With this method, I can readily switch shrouds and such (can add an exhaust nozzle or even switch to odd fins for testing). I'll likely make a separate thread on this part of my construction method since I think it works extremely well and is extremely convenient.
Thanks for following this far everyone! I think it's a great first start on this design!
I've saved the best for last! :grin:
Launch #2 was beautiful! I didn't video it myself, but got a look from under as it rose straight up, over on the delay and ejection and came back down not too far away. Very nice launch!
Video Link: https://www.youtube.com/watch?v=Cp0HLCHuFGs&feature=youtu.be
Launch #3...tried again to make sure...judge for yourself.
Video Links (note the wind sent it over to the right; however the rocket didn't noticeably weathervane and instead drifted to the right):
https://www.youtube.com/watch?v=qycwPCPfZPw&feature=youtu.be
https://www.youtube.com/watch?v=xrgaIUVnC8w&feature=youtu.be
I would consider "Well De-Finned" to be a successful design! I'll have to do more tests with the others; however it seems to be a very difficult mix to figure out successfully. Given that the ice will likely be gone after today, I'll have to launch elsewhere and this will be a bit on the back burner for now.
One thing no one picked up on was the modular construction I had on these rockets. I don't recall having heard/seen anything on this other than an article in Sport Rocketry where there was a very expensive modular rocket. With this method, I can readily switch shrouds and such (can add an exhaust nozzle or even switch to odd fins for testing). I'll likely make a separate thread on this part of my construction method since I think it works extremely well and is extremely convenient.
Thanks for following this far everyone! I think it's a great first start on this design!
Last edited:
Funniest thing is that the rocket design I would say is the most successful so far has some resemblence to the original prototype I posted.
KidRockET
Epstein didn't kill himself
- Joined
- Dec 7, 2014
- Messages
- 877
- Reaction score
- 86
Funniest thing is that the rocket design I would say is the most successful so far has some resemblence to the original prototype I posted.
I am amazed that...
You're not dead...
Or severly maimed...:wink:
Very nice flights for Well De-Finned! I slowed down playback speed so I could see it better, looked perfect. So the question is: were you actually getting stabilization from the fin slots, or just base drag and/or the effect of a big tube fin? Lots of fun experimentation ahead.
That is a beautiful backyard vantage point you have there, I'd have enjoyed the videos even without the launch.
That is a beautiful backyard vantage point you have there, I'd have enjoyed the videos even without the launch.
LOL!
The greatest danger was actually to myself...I had a very real threat of taking an ice bath! (Note I'm wearing a life jacket and have ice rescue picks/claws attached to it as precaution.)
Additionally my wife kept laughing each time I slipped on some icy patches..."Whoa!"...."Whoops!"
Very nice flights for Well De-Finned! I slowed down playback speed so I could see it better, looked perfect. So the question is: were you actually getting stabilization from the fin slots, or just base drag and/or the effect of a big tube fin? Lots of fun experimentation ahead.
That is a beautiful backyard vantage point you have there, I'd have enjoyed the videos even without the launch.
Thanks Neil! You did pose some great questions! It's very tough to answer. I doubt any one of those things would be sufficient to give you a stable flight (ex. the tube alone seems too small, the base by itself is definitely too small). Additionally, on the first launch it had a spirally rear end when the outlets were too narrow, so the outlets definitely have an effect. In fact, I think it works as a combination of factors.
I'll later post instructions on how I built WD'd so others can try on their own so maybe we can get more results. Fairly simple build with small parts.
Thanks for the compliment! While I grew up in a slum apartment in a high crime area in NYC, my father would sometimes take me fishing and I dreamed of one day living on a lake, so I jumped on the opportunity when it presented itself.
Thanks!
I know where you're coming from (and definitely appreciate the opposing viewpoint); however I do understand their stance as well...once safety is mentioned, it's difficult to argue otherwise and besides, after the recent accidents (which weren't LP at all) renewed safety calls in general do make sense. EDIT: Also I think it should be required if you have an untested design to at least have it launched as a "heads up" flight and from farther away (I will likely do any further test flights at my club after regular flights are done and most are gone...maybe even wait for everyone to leave).
Aside from that, my personal opinion is that these rockets posed very little danger when compared to HP stuff that comes in ballistic*, blows up or does power loops. Additionally, I recently started making my own motors...heck I'm worried about that one!
YMMV! Another unique characteristic on this design is that I think it "muffles" any instability. I earlier noted that RH made odd unstable movements which I hadn't witnessed before. I think it's because the design of the shroud itself allows sideways movement to be muffled as well as allow for some sideways drifting during that period, so it's like an odd slow dance.
Halving the exhaust slots? See WD'd flight #1. After that flight I opened the slots almost double and got great flights.
*Note: Of my 100+ flights last year, I don't recall having any lawn darts on rockets with recovery systems.
Last edited:
Similar threads
