upside down finless rocket

[Andyd103]

i have built an upside down fin less rocket that will run on 2 canted c's (in such a way that it will spin rocket), these are mounted at the very top of the rocket and my nose cone is at the bottom attached to the chute, on the top is a rounded thing to block that end.

Here is how i think it will work, i built the motor mount so that when the ejection charge pops it will allow the pressure to bounce off the hemispherical top and flow through the mount which is made from 2 1/4 inch sheets of play wood to the diameter of a bt-40 , and baffled, this should pop the bottom and allow the parachute to pop out. I have never seen anything like this but i will post flying results with aftermath pics when i have the time to fly it.

IF ANYONE has anything i should be aware of please let me know before i make a fool out of myself when i fly this at my local club

[Zeus-cat]

It sounds interesting. I'm sure there are people here that will have a better undertanding of how this SHOULD work; assuming it works at all. I am not sure I would launnch an untested rocket with no idea of what it will do at a club launch. This sounds more like test it with no one else around type of thing. Just my two cents.

[Andyd103]

It sounds interesting. I'm sure theree are people here that will have a better undertanding of how this SHOULD work; assuming it works at all. I am not sure I would launnch an untested rocket with no idea of what it will do at a club launch. This sounds more like test it with no one else around type of thing. Just my two cents.

well thats probably a good idea, the rocket feels stable

[NjCo]

Maybe run it by your club's RSO prior to launch day. It certainly seems like it'll be a rocket that might raise a few eyebrows at the RSO table on launch day.

[Micromeister]

Andy:
Yours is an experimental model design. Of that we can all agree.
Because of this your model Should NOT be flown at a Club launch open to the public, or where there will or might be other people.
As an experimental model this project should be test flown in as complete isolation as you can make it. As far away from people and property as humanly possible. Your model seems Like a great candidate for experimentation, but NOT with others around and a first class example of the type model rocket that should only be flown in complete isolation.

Here are a few things to think about.

* You have not mentioned where the launch lugs are located on this model or if they are centered between the motors allowing the model to freely rotate around this axis as the model begins its flight, building rotional speed as it raises. or you've mounted them offset on the outer body which would cause binding on the launch rod retarding the gaining of spin and forward motion.

* How long a launch rod is required to reach safe RMP & air speed?

* What is the minimum RPM your model must attain to achive spin stabilization?

* Have you considered starting with a less energetic set of motors. Say 13mm A10's? or even a micro version to test the fesibility of the design?

* "Feels Stable" What exactly does that mean? have you run any simulations on the design? done an aerodynamic calculations on the various states that this model must preceed through to obtain a safe and stable flight?

To be perfectly honest, I seem to recall forward mounted motors being examined rather extensively in the early 1970's. Perhaps a little research into the old Model Rocketeer magazine might give you some helps rather then taking the approach..."lets stick some motors in it and see if it flys." That is not a very scientific approach.
This could be a worthy experiment; but MUST NOT be done in the presents of a crowd. YOU and you alone or with as minimal a launch/recovery crew as you can muster should view these first "TEST FLIGHTS". Only after you have a WORKING, PROVEN Flying prototype do you take it to a club or public event. SAFETY FIRST Always.

[Andyd103]

if rocksim could do these calculations i would use it but for now I've done my pencil and paper work, there is no reason this rocket should not fly stable, rpm's are a different story, i have no idea how to calculate those but im guess it should be fast enough, i have a LR going through the center of the rocket, i drilled a hole in the motor mount the bottom cone and the top cone(it has a rubber valve on the top 1) so that when the rod has left that area it will reseal and not pop the bottom off, but i plan to do a test flight next Friday will post pictures

[ScrapDaddy]

Recomend this article on Emrr http://www.rocketreviews.com/reviews..._no_fins.shtml

[Andyd103]

Recomend this article on Emrr http://www.rocketreviews.com/reviews..._no_fins.shtml

thanks provided some insight but i want to try and keep the engines in the top to keep it unique and a learning experience

[Micromeister]

thanks provided some insight but i want to try and keep the engines in the top to keep it unique and a learning experience

Andy:
Not all that new or unique, well the USD recovery phase may be. Unfortunately I can't get to my back issues of the Rocketeer from the 70's currently the Basement rocket lab is torn-up for some rewiring, I'm pretty sure the articles i'm thinking of were in 1970-72 era, with or without them your experiment it should be a neat individual learning experience. Please give ourself plenty of room away from cars and windows.

Have you considered the action inertia may play on your model? I still think you'd be much better off starting with a smaller motor combo.

[Andyd103]

Andy:
Not all that new or unique, well the USD recovery phase may be. Unfortunately I can't get to my back issues of the Rocketeer from the 70's currently the Basement rocket lab is torn-up for some rewiring, I'm pretty sure the articles i'm thinking of were in 1970-72 era, with or without them your experiment it should be a neat individual learning experience. Please give ourself plenty of room away from cars and windows.

Have you considered the action inertia may play on your model? I still think you'd be much better off starting with a smaller motor combo.

like what motors should i start with?, the inertia shouldn't be a problem the rocket empty will be pretty light and the way i have the tubes set-up it should provide enough air resistance to slow it down on the 5 second ejection charge

[Micromeister]

like what motors should i start with?, the inertia shouldn't be a problem the rocket empty will be pretty light and the way i have the tubes set-up it should provide enough air resistance to slow it down on the 5 second ejection charge

I was thinking perhaps a pair of A10-3T 13mm motors would give you a very high initial thurst, get things moving and maybe spin-up, without the longer burn that you may not want on this first flight.

Actually I was thinking about the matter at rest phase of inertia. whats keeping your NC and recovery system in place? Please don't say friction.

[stickershock23]

This idea WILL WORK. but YOU NEED TO CHANGE IT AROUND A LITTLE BIT.

I have done this several times. I have a witches broom I fly at halloween.

3 motors at the top canted inward is better than 2. because it it making it stable along more than one axis.

You need weight at the BOTTOM of the rocket. down where the motors should be on a regular rocket.

as long as you do that it will fly fine.

One thing. it is a heads up flight. if a motor fails to fire it will make a nice arc to one side.

Make sure you put it out on a far pad, and let it rip.

I have a little gripe. then I am done. if you are an RSO at a launch. letting something fly that is untested is not a big NO NO. Use your brain think about what it should do and what it might do and make a decision accordingly. How else do you LEARN? a sim, is just, it will NOT tell you for sure what will happen. sometimes trying it is the best way to go. and if if fails. learn from it.

JUST DO IT SAFE. put it out far enough, call a heads up, get EVERYONE ON THEIR FEET you are good to go.

This does not mean let EVERYTHING fly, there are times an RSO MUST say no. but in this case as long as it is built fairly decent. built SQUARE, and it is not a missile (metal, sharp, way over powered, made of something dangerous) let it fly.

I know some will disagree with that. but that is my thoughts. I won't hate you if you think different. don't hate me because I do.

[Andyd103]

I was thinking perhaps a pair of A10-3T 13mm motors would give you a very high initial thurst, get things moving and maybe spin-up, without the longer burn that you may not want on this first flight.

Actually I was thinking about the matter at rest phase of inertia. whats keeping your NC and recovery system in place? Please don't say friction.

why is friction a bad thing? there is quite a big of force required to remove the nosecone, it has 1.5 inches of bite into the rocket, suggest any other methods?

[NjCo]

why is friction a bad thing? there is quite a big of force required to remove the nosecone, it has 1.5 inches of bite into the rocket, suggest any other methods?

You'll leave that nose/tail? cone sitting on the launch pad.

[cjl]

3 motors at the top canted inward is better than 2. because it it making it stable along more than one axis.

This shouldn't be the case. 2 vs 3 motors should not impact stability at all, so long as they are spaced evenly and balanced.

[Andyd103]

You'll leave that nose/tail? cone sitting on the launch pad.

well why is that? explanations would help because i am experimenting and the point of an experiment is to formulate a conclusion, which i cannot do without data

[stickershock23]

This shouldn't be the case. 2 vs 3 motors should not impact stability at all, so long as they are spaced evenly and balanced.

I am thinking if they were pointed straight down ( but still angled out) as compared to pointed one direction ti cause a spin. If you spin it yes it should be stable. if you don't spin it you are basically building this.

[cjl]

Yes, but even then, 3 vs 2 doesn't make a difference. In either case, the net force vector is the same.

[Micromeister]

You'll leave that nose/tail? cone sitting on the launch pad.

Andy:
Come on think! If your relying on friction to keep your NC, chute and wadding in place your gonna be very unhappy at liftoff. Those parts have mass and that mass is a rest and wants to remain at rest. Making sure they are at the extreme rear will help a bit but your going to need some sort of launcher lashed pull pin that will keep everything together until they all get going. The highter the initial thrust your motors produce and more twist they impart the more likely your Friction fitting NC will be dislodged at or very shortly after ignition.

One more little side note:
While it's nice to seal off the hole for your launch rod, it's not necessary or even all that good idea as the self-sealing rubber stopper or whatever your using is causing friction between it and the launch rod retarding your launch acceleration and spin-up. That small 1/8" hole isn't enough to keep either of the motors ejection charges from working as planned unless you have one HUGE cavity of a core body.

Do you see now why I strongly suggest that your first few flights be done in isolation and with smaller motor combinations? It might also be helpful to vidoe tape the first few seconds of the flight if you have that options for review and possibly slow motion inspection.

[Micromeister]

This idea WILL WORK. but YOU NEED TO CHANGE IT AROUND A LITTLE BIT.

I have done this several times. I have a witches broom I fly at halloween.

3 motors at the top canted inward is better than 2. because it it making it stable along more than one axis.

You need weight at the BOTTOM of the rocket. down where the motors should be on a regular rocket.

as long as you do that it will fly fine.

One thing. it is a heads up flight. if a motor fails to fire it will make a nice arc to one side.

Make sure you put it out on a far pad, and let it rip.

I have a little gripe. then I am done. if you are an RSO at a launch. letting something fly that is untested is not a big NO NO. Use your brain think about what it should do and what it might do and make a decision accordingly. How else do you LEARN? a sim, is just, it will NOT tell you for sure what will happen. sometimes trying it is the best way to go. and if if fails. learn from it.

JUST DO IT SAFE. put it out far enough, call a heads up, get EVERYONE ON THEIR FEET you are good to go.

This does not mean let EVERYTHING fly, there are times an RSO MUST say no. but in this case as long as it is built fairly decent. built SQUARE, and it is not a missile (metal, sharp, way over powered, made of something dangerous) let it fly.

I know some will disagree with that. but that is my thoughts. I won't hate you if you think different. don't hate me because I do.

I totally disagree with your assertion that unproven models should be allowed at public events. By the Safety code we've all sworn to uphold ONLY proven models are to be flown at Public or club events.
Unproven models and ALL expermiental models should be flown IN ISOLATION. NOT for our safety but for the safety of the general public. NO-ONE knows What an unproven model will do just by looking at it period.

All that said why did you use forward motors on your witches broom? My full size Witches broom flys on a single D12 in the rear.

[cjl]

I disagree Micro. Given proper caution and correct motor choice, unproven models can absolutely be flown at public events.

[stickershock23]

I totally disagree with your assertion that unproven models should be allowed at public events. By the Safety code you've sworn to uphold ONLY proven models are to be flown at Public or club events.
Unproven models and ALL expermiental models should be flown IN ISOLATION. NOT for your safety but for the safety of the general public. NO-ONE knows What an unproven model will do just by looking at it period.

All that said why did you use forward motors on your witches broom? My full size Witches broom flys on a single D12 in the rear.

Micro I don't want to argue. I think we just have different points of view.
I will say I wouldn't let every experiment fly. there should be some fact to back up stability. if a rocketeer can show me his thoughts on why it should fly correct, and show he's put some thought into it. and taken some good safety measures.. then let it fly. FROM THE AWAY PADS.. and again call heads up and everyone on their feet.

Personally if I were to tell someone like that NO you cant try it. I fell like I am stopping new thinking and learning. thats where I have a problem with it.

Of course if it does not seem safe or it built out of dangerous things. or the rocketeer can't even explain why he thinks it will be stable.. then the answer would be NO. Of course bottom line is it is up to the RSO on duty.


I guess for Halloween we are drag racing brooms... my has a cluster of 3 18mm's LOL

[Micromeister]

I must ammend my pervious post! as the Model Rocket safety code as been ammended removing the wording about unproven models, replacing it with far less safety minded verbage.

I do not however change my position on unproven designs. As we can not On the field, "Check stability before Flight", nor adaquately "Warning spectators and clearning them away to a safe distance" at public or Club launches.

Chris;
This is EXACTLY how accidents happen. examples like the X-wing, X-15, and on and on. Test flights for every type of flying vehicle in the world are done in Isolation, out in the middle of a dessert somewhere with minimal flight crews and observers. Why? to protect the unknowing by-standers. Our models deserve the same respect. Underestimation and disprespect will be the undoing of our hobby. We must always think SAFETY First. I hate to say it but honestly most RSO's these day are not qualified to make such decisions... myself included.

[Micromeister]

Micro I don't want to argue. I think we just have different points of view.
I will say I wouldn't let every experiment fly. there should be some fact to back up stability. if a rocketeer can show me his thoughts on why it should fly correct, and show he's put some thought into it. and taken some good safety measures.. then let it fly. FROM THE AWAY PADS.. and again call heads up and everyone on their feet.

Personally if I were to tell someone like that NO you cant try it. I fell like I am stopping new thinking and learning. thats where I have a problem with it.

Of course if it does not seem safe or it built out of dangerous things. or the rocketeer can't even explain why he thinks it will be stable.. then the answer would be NO. Of course bottom line is it is up to the RSO on duty.

I guess for Halloween we are drag racing brooms... my has a cluster of 3 18mm's LOL

I don't think its arguing at all:
We are not telling the modeler don't fly this widget. We are saying; "Look the Scientific Method says our experiments be done AWAY from crowds of unsuspecting distracted people.

You know as well as I do that even with PA announced HEAD-UP, Everyone on their feet calls. NOT everyone is paying attention to the flight. I see this all the time at launches all over. True it's mostly the very young and Teenagers but it's also the distracted MOMs dealing with the young kids. or the bunch of vets discussing this important flight detail from an hour ago. People NOT directly involved with a given flight just don't take them all that seriously...until something happens... then they are all " Well why didn't you folks do something".

We are not stopping any thinking or learning.. as a matter of fact we are encouraging the BETTER use of the Scientific method to presue the goal. AND encouraging and further driving home the NEED for SAFETY FIRST thinking. Flying unproven models in isolation can even be set up as a ClUB activity using limited launch crews and range provisions. Thats the problem with common sense.... it just seems it isn't so common anymore.

[Shade]

....dessert ...

??? I'm hungry!!!

[Micromeister]

??? I'm hungry!!!

Dang! never said I could spell. I think i'm gonna leave it as is LOL!!!!

[luke strawwalker]

Andy:
Yours is an experimental model design. Of that we can all agree.
Because of this your model Should NOT be flown at a Club launch open to the public, or where there will or might be other people.
As an experimental model this project should be test flown in as complete isolation as you can make it. As far away from people and property as humanly possible. Your model seems Like a great candidate for experimentation, but NOT with others around and a first class example of the type model rocket that should only be flown in complete isolation.

Here are a few things to think about.

* You have not mentioned where the launch lugs are located on this model or if they are centered between the motors allowing the model to freely rotate around this axis as the model begins its flight, building rotional speed as it raises. or you've mounted them offset on the outer body which would cause binding on the launch rod retarding the gaining of spin and forward motion.

* How long a launch rod is required to reach safe RMP & air speed?

* What is the minimum RPM your model must attain to achive spin stabilization?

* Have you considered starting with a less energetic set of motors. Say 13mm A10's? or even a micro version to test the fesibility of the design?

* "Feels Stable" What exactly does that mean? have you run any simulations on the design? done an aerodynamic calculations on the various states that this model must preceed through to obtain a safe and stable flight?

To be perfectly honest, I seem to recall forward mounted motors being examined rather extensively in the early 1970's. Perhaps a little research into the old Model Rocketeer magazine might give you some helps rather then taking the approach..."lets stick some motors in it and see if it flys." That is not a very scientific approach.
This could be a worthy experiment; but MUST NOT be done in the presents of a crowd. YOU and you alone or with as minimal a launch/recovery crew as you can muster should view these first "TEST FLIGHTS". Only after you have a WORKING, PROVEN Flying prototype do you take it to a club or public event. SAFETY FIRST Always.

"Presence" not "presents"... antonyms, -1...
LOL J/K... what I get for helping my English-teacher wife grade papers...

Seriously, "copy that" to everything you said.

ESPECIALLY about the 'try it on lower power motors first. 13mm adapters are easy enough to make to fly it on mini motors first, or barring that even A8-3's would be a better choice for a first flight.

Be sure you get REAL GOOD RELIABILITY in your ignition methods-- carefully inserted Quest Q2G2's would probably give the best reliability in this regard, IMHO...

Good luck! OL JR

[luke strawwalker]

I must ammend my pervious post! as the Model Rocket safety code as been ammended removing the wording about unproven models, replacing it with far less safety minded verbage.

I do not however change my position on unproven designs. As we can not On the field, "Check stability before Flight", nor adaquately "Warning spectators and clearning them away to a safe distance" at public or Club launches.

Chris;
This is EXACTLY how accidents happen. examples like the X-wing, X-15, and on and on. Test flights for every type of flying vehicle in the world are done in Isolation, out in the middle of a dessert somewhere with minimal flight crews and observers. Why? to protect the unknowing by-standers. Our models deserve the same respect. Underestimation and disprespect will be the undoing of our hobby. We must always think SAFETY First. I hate to say it but honestly most RSO's these day are not qualified to make such decisions... myself included.

"desert" (hot dry place) not "dessert" (tasty sweet after-supper treat)... antonyms -1...

OK, I'll shut up now before you tell me to go to a "hot dry place" (and I'm not talking about a desert... )

Later! OL JR

[RangerStl]

Luke;

"Homophones", not antonyms... -1

They sound the same (Homo-same; phone-sound) but have "different" spellings.

Antonyms are words with opposite meanings; not necessarily spelled or sounding the same.

[Andyd103]

great input... anyone else have any ideas on how to keep the nc on, i personally don't think the 25g of nosecone and streamer are going to create a big enough force to pop off the noce cone under the acceleration of liftoff but then again you probably know more than me so any ideas on how to keep it on will be great