Something Crazy

[ThreeJsDad]

This is an old idea from many years back. My buddy and I would see the giant Easter eggs and say we should use them for rockets. I finally followed through. There is still a hadful of work to do on it but it iswoeking out really well so far.

 

[lakeroadster]

No doubt it looks cool... but have you done a simulation? Not a very stable configuration.... even with a ton of nose weight.

 

[ThreeJsDad]

I have not done a simulation.
Thanks for doing the drawing, I appreciate the help.
The photo is probably misleading because the CP will be back quite a bit from where your simulation has it.

I think it will fly very well when it is done.

 

[BABAR]

Big ring fin

 

[ThreeJsDad]

Big ring fin

That would look cool, Now to find something to form it on. It would also add some durability to the fins. Even a rod bend in that shape would add strength and a bunch of drag and make it really stable.

 

[0011001100]

Just a warning. I attempted one of these a few years ago, even with a large amount of nose weight they still aren't stable. Also the plastic used for the eggs is very brittle and weak and does not like have a motor in it.

 

[lakeroadster]

I have not done a simulation.
Thanks for doing the drawing, I appreciate the help.
The photo is probably misleading because the CP will be back quite a bit from where your simulation has it.

I think it will fly very well when it is done.

Great. Could you please explain how the CP will be back farther on your version?

As a point of reference, remember the Estes Dart Vader rocket? There was a reason they put that long body tube out front, and I think we can all agree that it wasn't to make it look good.

See how adding the tube allows weight to be added... that increases the stability dramatically.

 

[BABAR]

Name it “Embrio”?

 

[BABAR]

https://www.rocketryforum.com/threads/hiding-your-fins-in-plain-sight-240-calories-of-fun.47954/

Quaker Oatmeal canister containers make good ring fins. The generic canisters are too thin. Not sure if it will scale to your model.

Ring fins like my coke bottle above can make just about anything stable, you can fly a GI Joe or a Barbie doll or a teddy bear or a brick (well, a brick shaped rocket), challenge there is finding room for recovery gear.

 

[Rocketjunkie]

Here's one flown in 2001 at Orangeburg. Frame cap from analog video. I don't have info on whose rocket this was. IIRC 3" body and 9" egg max diameter. Flew well.

 

[lakeroadster]

Here's one flown in 2001 at Orangeburg. Frame cap from analog video. I don't have info on whose rocket this was. IIRC 3" body and 9" egg max diameter. Flew well.
View attachment 408450

 

[cwbullet]

View attachment 408451

You should post the file. I can see a lot of people making a trip to the store to buy these.

 

[lakeroadster]

https://www.rocketryforum.com/threads/hiding-your-fins-in-plain-sight-240-calories-of-fun.47954/

Quaker Oatmeal canister containers make good ring fins. The generic canisters are too thin. Not sure if it will scale to your model.

Ring fins like my coke bottle above can make just about anything stable, you can fly a GI Joe or a Barbie doll or a teddy bear or a brick (well, a brick shaped rocket), challenge there is finding room for recovery gear.

Is the reason for the added stability because ring fins are incredibly "draggy"?

 

[lakeroadster]

You should post the file. I can see a lot of people making a trip to the store to buy these.

I "hacked" this design our in about 5 minutes... proceed with caution.

 

[ThreeJsDad]

I am already reworking it !!! Thanks for all the input. The CP would have been back a bit further than the model that was simmed due to my "fins" being quite a bit longer and wider than the drawing. I had 13" between fin tips and the bottom of the egg was 6" off the table. That is why I said my photo did not really give a good reference.

That is already in the past !!! I made a ring fin from a long strip of G-10 I had lying about. I simply made a hoop and slotted the fins to accept it. The ring is 1.5" wide and 13" in diameter. I will shoot some new pics later but I think it looks even cooler.

If folks are interested in building one I will send all the specs to Lakeroadster if he is willing to create the plans or a file for it.

Here is the funny part, I was not after an "Egg Rocket" I was trying to build more of a Martian lander..... I just thought the egg was a good base to start with.

 

[ThreeJsDad]

Just a warning. I attempted one of these a few years ago, even with a large amount of nose weight they still aren't stable. Also the plastic used for the eggs is very brittle and weak and does not like have a motor in it.

Thanks for the heads up. This might be a different Egg because I am finding the plastic to pretty durable. It is on the softer end and less brittle side compared to a lot of plastics I have worked with. When I cut it with my dremel if does not craze like many plastics, it actually cuts similar to Lexan. I also made the MMT out of Fiberglass to add stretch to the whole thing.

To make some changes I had to pop the MMT out. I had not glued in the centering ring but i had glued the MMT at the bottom of the egg. I had to pop the MMT out with a dowel and a hammer and the egg was fine. I was quite surprised at how hard I had to hit it and that nothing broke.

 

[ThreeJsDad]

Name it “Embrio”?

That might offend some folks... So far I have come up with "Scrambled" and "Eggonator".

 

[BABAR]

Run your launch lug through the egg next to the motor mount. Your motor mount should extend all the way to the inside tip surface of the nose cone (can use an expended motor casing full of clay or other weight to form the internal “shoulder” of the cone.)

Use a straw or straws to make a single long internal lug running the length of the motor mount. Small hole in the aft end of the plastic base is the “entry site” for the rod. Small hole drilled the in plastic nose cone in the appropriate spot for the “exit” point of the rod. Worked great on Tank Killer
https://www.rocketryforum.com/threads/tank-killer-caught.157129/

With Easter coming up, other names would include
CottonTail
High Cholesterol

 

[ThreeJsDad]

Run your launch lug through the egg next to the motor mount. Your motor mount should extend all the way to the inside tip surface of the nose cone (can use an expended motor casing full of clay or other weight to form the internal “shoulder” of the cone.)

Use a straw or straws to make a single long internal lug running the length of the motor mount. Small hole in the aft end of the plastic base is the “entry site” for the rod. Small hole drilled the in plastic nose cone in the appropriate spot for the “exit” point of the rod. Worked great on Tank Killer
https://www.rocketryforum.com/threads/tank-killer-caught.157129/

With Easter coming up, other names would include
CottonTail
High Cholesterol

You nailed it. I may not run the MMT all the way to the nose. I already have a fiberglass one that is right about half way. I may bring a dowel back from the nose so it slips into the MMT. I did indeed plan to run the launch lug all the way through. The chute and maybe Marvin, will rid inside the egg and when it separates the upper half will pull the folded chute out of the compartment. If Marvin is in thee he will hopefully drop out on his own tiny chute.

I love the use of the toilet tank float.

 

[BABAR]

If your motor mount is completed, no problem. I would still run the straw so it does from plastic tail to undersurface of the nose cone. You may need a dowel or stick or fiberglass to stiffen it,

Originally with the toilet float I thought I would just need two holes, one forward and one aft. But it was a dickens of a time lining up the rod with the two holes, since I couldn’t see inside. The straw provides a guided path so once you thread the rear hole on the rod, it routed it right through the upper hole.

In your case you just need to rotate the nose cone until the straw lines up with the hole you place in the cone. It will also keep it from fouling your recovery stuff.

 

[ThreeJsDad]

If your motor mount is completed, no problem. I would still run the straw so it does from plastic tail to undersurface of the nose cone. You may need a dowel or stick or fiberglass to stiffen it,

Originally with the toilet float I thought I would just need two holes, one forward and one aft. But it was a dickens of a time lining up the rod with the two holes, since I couldn’t see inside. The straw provides a guided path so once you thread the rear hole on the rod, it routed it right through the upper hole.

In your case you just need to rotate the nose cone until the straw lines up with the hole you place in the cone. It will also keep it from fouling your recovery stuff.

Exactly !! I planned to run it full length to keep the recovery system from touching the launch rod. I think I will use an old carbon arrow shaft. The newer ones are nut just pultruded, they are spiral wound so that should work well. I will leave it attached to the lower half so it is glued to the MMT and the plywood centering ring. I think I will let it come through the top about 1/16" just to keep things lined up.

 

[ThreeJsDad]

Thanks Babar

 

[BABAR]

Is the reason for the added stability because ring fins are incredibly "draggy"?

I don’t think the are disproportionately draggy. They do have a lot of surface area. Also, as opposed to standard fins, the full surface are is displaced away from the center line. Think about standard fins, the most lateral few mm of the surface have the most effect on CP, as opposed to the most medial few mm which have almost ZERO effect on CP. for a ring fin the WHOLE surface area is way “out there.”

You can also extend it aft of the nozzle without KrUshnic effect.

It also kind of looks like a display stand when you put the rocket on the shelf.

If you don’t mind separating the nose cone, you can also use horizontal spin recovery (with a few well placed windows.). This appears to be the most rarely used recovery I have seen (although air brake is also pretty rare, also breakaway.)
https://www.rocketryforum.com/threads/bail-out-bill-and-the-horizontal-spin-recovery-rocket.147210/

 

[Kelly]

No doubt it looks cool... but have you done a simulation? Not a very stable configuration.... even with a ton of nose weight.

Can anyone explain, qualitatively, why the CP should be where that OpenRoc sim shows it to be? I would think that for just an egg, the CP should be at the center of the egg. It's symmetric, so why would it NOT be there? Then you add fins, that can only move it backward. What is going on that moves the CP so far forward?

 

[neil_w]

I made a ring fin from a long strip of G-10 I had lying about. I simply made a hoop and slotted the fins to accept it. The ring is 1.5" wide and 13" in diameter. I will shoot some new pics later but I think it looks even cooler.

13"! Now that is a *ring*.

BTW I think a big part of the stability challenge here is that the tail, uh, "cone" tends to push CP forward.

 

[ThreeJsDad]

13"! Now that is a *ring*.

BTW I think a big part of the stability challenge here is that the tail, uh, "cone" tends to push CP forward.

That makes sense and the cone shape to the tail end makes it cleaner aerodynamically but less stable even on a 3FNC. That means here it would be a nightmare to contend with.

I am glad you like the ring...

 

[neil_w]

Yup. Tapered tails reduce drag but push CP forward. Needs to be accounted for in a design.

 

[BBowmaster]

Easter egg and toilet float rocket... which you guys analyze as avidly as a Space-X launch.

I love you guys.

 

[neil_w]

Easter egg and toilet float rocket... which you guys analyze as avidly as a Space-X launch.

I love you guys.

Mr. Barrowman doesn’t take the day off when oddrocs fly!

 

[ThreeJsDad]

Easter egg and toilet float rocket... which you guys analyze as avidly as a Space-X launch.

I love you guys.

Thank You Sir, anyone can build and fly 3FNC. Getting a toilet to fly takes a special skill. The Egg just needs a really big ring to st in.

Just Wait.....I have three of these eggs and this is the smallest one....