Winged and forward winged designs unstable for rockets?

[KenECoyote]

Hi everyone!
I've come up with a "self-stabilizing" design that may work well for rockets with forward fins as well as rockets with large mid wings and want to do further testing. I've already made a Lacrosse-ish build using Estes Viking parts and the first launch on 1/2A3 was fantastic and didn't have any nose weight added (future test version to have bigger wings, smaller bt, etc.).

Anyone ever saw some jet or missile design they thought would be great if it could be made into an lp rocket without a ton of nose weight?

One idea for me would be the ME 163 Komet; however that one may be too ambitious.

Life right now is absolutely nuts, but I wanted to get some ideas so I can plan to build next month or so.

 

[Daddyisabar]

F104 or Mig 21 make excellent rockets. Motor in the back, where it should be, and fins mostly aft, where they too should be. Not a lot of no good, stinking, performance robbing nose weight required. Maximum impulse motors are super cool in these airplane oddrocs.

 

[KenECoyote]

F104 for sure! And the Fishbed isn't one I ever thought of...delta wings and beautiful front nose inlet...dang I wanna build that!

 

[tab28682]

Mig-21 does make a great rocket and a great boost or rocket glider.

Here is my 27 year old D12 powered Mig-21 boost glider in action. It does have some nose weight in the pop pod, just enough to keep the CG the same for boost as it is for gliding.

https://www.rocketryforum.com/threa...rable-od-mig-21-d-powered-boost-glider.68296/
Interesting that your Lacross worked without nose weight. Where did it balance at launch? What was the wind at launch? Probably helped that is was a mini motor without much mass at the rear of the rocket.

I have never had any luck trying to fly an airplane or launch a rocket without the CG being In front of the CP.

 

[aerostadt]

I am wondering if the 1/2A3 motor in post #1 is very light and the model with nose weight flew well as a result. A heavier motor with more power might then require nose weight. As I remember my daughter did a science project 25 years ago with a lpr model that flew alright with a small motor, but the same model did cart wheels with a larger motor.

 

[KenECoyote]

Here's the balance point for A10-3T (may try next). The balance point for 1/2A3-2T is just maybe a quarter inch forward from that. No nose weight...empty BT5 nose cone except for recovery streamer (gimme some slack )

 

[KenECoyote]

Video of first launch on 1/2A3-2T...video doesn't do it justice since it was stunning rising up in the blue sky!
https://youtube.com/shorts/NW9RmDe2wIY

 

[neil_w]

I would think the AIM-39 Exocet would generally be nose weight-dependent to stabilize, probably not as much as that Lacrosse though.

 

[KenECoyote]

I would think the AIM-39 Exocet would generally be nose weight-dependent to stabilize, probably not as much as that Lacrosse though.
View attachment 457128

That's a beauty! I'll try to build that as the next bulk Viking bash.

 

[Ez2cDave]

F104 for sure!

F104 . . .

Dave F.

 

[Greg Furtman]

I grew up in Duluth, MN which at that time had a large Air Force Base so I was always seeing different types of jets over the years. The F104 has always been on of my favorites. I now live near Spooner, WI and a couple of summers ago I saw two beautiful F104s flying north. About 15 minutes later they flew overhead again this time heading south. I wonder who owns them. They were great to see again.

 

[KenECoyote]

I grew up in Duluth, MN which at that time had a large Air Force Base so I was always seeing different types of jets over the years. The F104 has always been on of my favorites. I now live near Spooner, WI and a couple of summers ago I saw two beautiful F104s flying north. About 15 minutes later they flew overhead again this time heading south. I wonder who owns them. They were great to see again.

I love the Starfighter, but there are already a number of kits out there for that. Still, it may be good for me to try a more scale one.

 

[KenECoyote]

F104 . . .

Dave F.

View attachment 457185

NICE! I do regret having missed this one. I actually have 2 or 3 of the same static plane from back when I was into collecting the large military models available at Toys R Us. I may dog it up one day and try the conversion myself.

 

[KenECoyote]

So far my plans for next builds is to do an X-15 (just started, but will be a lot of work), an Exocet and then maybe the F104. Hopefully I can get at least one of them done and launched this weekend.

 

[Sooner Boomer]

I built a scale model of the Isreali "Barak" SAM.

It acted like it was actually flying on the wings (fins). A noticably different flight from the normal "ballistic" flight.

 

[tab28682]

Here's the balance point for A10-3T (may try next). The balance point for 1/2A3-2T is just maybe a quarter inch forward from that. No nose weight...empty BT5 nose cone except for recovery streamer (gimme some slack )

View attachment 457122Or

A quarter mile inch ahead of that looks reasonable to me. More wing area behind the CG than in front of the CG. That little motor really helps.

 

[KenECoyote]

A quarter inch ahead of that looks reasonable to me. More wing area behind the CG than in front of the CG. That little motor really helps.

Whaaa? Lol
Tbh I don't feel a quarter inch makes that much of a difference here since I believe the cg is still at or behind the cp.

Here's a pic of the CG & CP of an Exocet for comparison.

 

[Ez2cDave]

Tbh I don't feel a quarter inch makes that much of a difference here since I believe the cg is still at or behind the cp.

You might want to re-evaluate your statement . . . " I believe the cg is still at or behind the cp".

WHY ?

If the CG & CP are in the same location, the rocket is Neutrally-Stable . . .

If the CG is BEHIND the CP, the rocket is Unstable !

Dave F.

 

[KenECoyote]

Vid to come!

 

[KenECoyote]

You might want to re-evaluate your statement . . . " I believe the cg is still at or behind the cp".

WHY ?

If the CG & CP are in the same location, the rocket is Neutrally-Stable . . .

If the CG is BEHIND the CP, the rocket is Unstable !

Dave F.

View attachment 457236


View attachment 457237

True and agreed...this is a test of my own design stabilizing system, hence I was asking for ideas on winged rockets that are naturally unstable (like your example on the right) without a lot of nose weight or some active stabilizing. Mine has what I call MAARS (Mechanically Active Automatic Rocket Stabilization). I'll create a post on it in a week or so after more tests and designs.

 

[KenECoyote]

I was able to test the Lacrosse this morning on an A10-3T and it was a bit wobbly, but successful. I liked that it seemed to be working to stabilize, which was GREAT data. I also included pics of the nosecone on landing to show it empty.
https://youtube.com/shorts/ivI5Q8qnJIQ

 

[Kelly]

This thread would be better if you posted a simulation file of the rocket design...

 

[Daddyisabar]

Forward fins on rockets rule! Airplanes love neutral stability, so airplane rockets should too! Oopsie!

 

[KenECoyote]

This thread would be better if you posted a simulation file of the rocket design...

I will eventually, but I have to get Rocksim or similar first and learn it. What are you looking for in the sim? Currently my time is extremely limited...stressing myself just getting these test prototypes built and personally I enjoy working with my hands more than the computer since I spend most of my working hours tied to the computer.

Right now my brain is full of multiple ideas and a dozen or so different designs for the system itself, so sim creating takes a back seat for me...that will come later after successful designs and before upscales. Testing stuff people say doesn't work/isn't possible takes time from my experience.

I also have a major life event going on right now that can determine my success or failure in my career, so this is actually a secondary focus. After that, my club will start soon and I have to get my rockets and electronics back into shape and relearned after 5 years away (but so worth it!).

Still, I really enjoy testing these "out there" ideas of mine, so I'll update and post as I find time. I hope to post on the design separately after that career life event is over this week (hopefully).

Edit: Oh, also I have two Miatas which I plan to mod & race this year! Too much fun, not enuf time!

 

[KenECoyote]

Forward fins on rockets rule! Airplanes love neutral stability, so airplane rockets should too! Oopsie!
View attachment 457348

Whoa!
Do those require a lot of nose weight? If so, how do you get good recovery? I find that a tricky part of some of my builds such as my upside down rocket, which in a way these resemble.

 

[Daddyisabar]

Whoa!
Do those require a lot of nose weight? If so, how do you get good recovery? I find that a tricky part of some of my builds such as my upside down rocket, which in a way these resemble.

At a recent launch the top designer for the largest model rocketry company in the world held the Backburn Triplane and then I handed him the nose cone. With out saying a word he immediately broke out into a sustained belly laugh. Yes, silly airplane oddrocs take copious amounts of no good, stinking, performance robbing nose weight. Recovery is on multiple chutes on seperate bits if you have a nose cone that separates. These rockets are like a really cheap hospital; no Recovery Room!

The Dornier 217 N utilizes powdered Tungsten in the nose. So desperate was the oddroc builder for maximum mass in a small volume. Many, many problems to overcome on each model. Asymmetric drag and weight, widely spaced pods (Asymmetric Thrust,) stability issues, exhaust flame burning fins in flght, poor boy dual deploy, ridiculous canted tractor motors, lack of computer simulation and ability to swing test. Use the dark arts and you will fly the airplane oddrocs you love!

 

[Daddyisabar]

F104 . . .

Dave F.

View attachment 457185

Flying this under rocket power with gear down and rockets strapped on the bottom? Crazy! Insanity! Hurry, get the RSO, get the Po Po! I am running to Bunker tightly clutching my model rocketry handbook! YIKES!

 

[KenECoyote]

At a recent launch the top designer for the largest model rocketry company in the world held the Backburn Triplane and then I handed him the nose cone. With out saying a word he immediately broke out into a sustained belly laugh. Yes, silly airplane oddrocs take copious amounts of no good, stinking, performance robbing nose weight. Recovery is on multiple chutes on seperate bits if you have a nose cone that separates. These rockets are like a really cheap hospital; no Recovery Room!

The Dornier 217 N utilizes powdered Tungsten in the nose. So desperate was the oddroc builder for maximum mass in a small volume. Many, many problems to overcome on each model. Asymmetric drag and weight, widely spaced pods (Asymmetric Thrust,) stability issues, exhaust flame burning fins in flght, poor boy dual deploy, ridiculous canted tractor motors, lack of computer simulation and ability to swing test. Use the dark arts and you will fly the airplane oddrocs you love!

I hear you and I believe we follow the same belief/religion/cult lol! But powdered tungsten...mind blown, but thumbs up!

 

[KenECoyote]

Here's a flight from this morning... it's my second "upside down" style build (yeah, I have a first! Bwahaha!).

I had to add some nose weight since this REALLY pushes rocketry fundamentals. It's cool that you can see it stabilizing as the wind pushes it...it works to remain vertical while fighting weather cocking. There was ejection, but streamer didn't deploy.

 

[KenECoyote]