Lakeroadster's Estes Logo Rocket

[sr205347d]

You may have discovered an instance where the base drag hack doesn't work. Sim it without the hack.

 

[lakeroadster]

@lakeroadster , can you try wrapping tape (maybe electrical/vinyl) tape around the gap to make this a “pure” smooth cone and retry the swing test?

Wrapping tape adds considerable weight. I'll try it with a paper template that negates the rear step in the cone.​

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I'm also going to bore a 3/4" dia. hole in the fuselage to allow addition of nose weight. I'd like to get a stable swing test of the raw fuselage before adding the fins and the motor mount, just to see how much nose weight is needed.​

My Ping Pong ball ring tail rockets flew great, but they swing tested consistently BACKWARDS.

Consistently flying backwards in a swing test is an indication of a rocket with stability, but not a lot of stability. Let's call this neutral stability. If it flies like this in a swing test at relatively low velocities, in actual powered flight where velocities are high, it will likely fly stable.​

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A rocket that has a high caliber of stability will re-orient itself and always fly nose in the wind. But it can be argued that this is too much nose weight and is robbing performance (reduced velocity and apogee) for no legitimate reason.​

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Ideally you want the rocket to just tip the scale of stability.​

You may have discovered an instance where the base drag hack doesn't work. Sim it without the hack.

Wait. What happened to "Trust The Sim"?​

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FWIW: The rocket has a stability of -0.163 without the base drag hack.​

 

[sr205347d]

Wait. What happened to "Trust The Sim"?

I didn't say to trust the hack.

 

[lakeroadster]

I didn't say to trust the hack.

You saw the sim... it has the base drag cone. Don't be "that" guy, the one that starts adding qualifiers after the fact.​

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It's called a "simulation" for good reason.​

 

[sr205347d]

It may be that swing testing itself may not be valid for some rockets.

Swing tests are not invalid (a rocket that passes will be stable), but a requirement to pass a swing test is unnecessary overkill. Remember, the CP location is AOA dependent. The backslide, HSR, and belly flop rockets all depend on the CP shifting forward of the CG at high AOA, and would fail swing tests.

 

[lakeroadster]

Swing tests are not invalid (a rocket that passes will be stable).

I've proven that not to be true when it comes to odd-rocs. My Cygnus Probe passed several swing tests, and did not fly stable.​

 

[BABAR]

I've proven that not to be true when it comes to odd-rocs. My Cygnus Probe passed several swing tests, and did not fly stable.​

 

[Daddyisabar]

Vader was a silly mindsimmer from an early age, flying oddrocs with widely spaced motors in pods.

 

[Pappy]

...the Estes logo rocket looked conical because it was receding into the distance...

interesting. didn't 'see' that until you pointed it out.

 

[Daddyisabar]

I just don't get it. Why, with all these fancy tools like computer simulations, cardboard mock ups, swing tests, miniature models, supersonic wind tunnels, electronic stabilization etc. etc., can we not make a simple bullet fly straight? Old dudes back in '06 with their .30 caliber Spitzer shaped round, Gerald Bull and his gas bleed design for who ever would buy it, super secret rocket assisted artillery shells we won't send to Ukraine. I just want the pretty cone to fly.

All I ask is for a simple finnless egg rocket to fly. Is that too much?

RSO: Yes Daddy, it is!

 

[cwbullet]

I don’t think nose weight will be required.

You are likely correct, a cone rockets tend to be easy to make stable.

 

[sr205347d]

I've proven that not to be true when it comes to odd-rocs. My Cygnus Probe passed several swing tests, and did not fly stable.

Copied from that thread:

Here are some thoughts for the mind sim:

The landing legs are cylinders with not insignificant diameter. When fluid flows fast enough across a cylinder, a vortex will form on one side or the other in an unpredictable manner. The static pressure in a vortex is less than in the free stream. Less pressure on one side of the cylinder produces an aerodynamic force towards that side. With three legs, it is possible that each has the vortex on the same side, in which case it would produce a pure rolling moment on the rocket. But if one vortex is counter-rotating, the net force will induce a pitching or yawing moment which will act to tumble the rocket.

At low speed, the air is more viscous, and there will not be any vortices. Vortices will form at higher speed, faster than your swing test can produce.

 

[lakeroadster]

Nose Weight & a Couple of Successful Swing Tests

I bored a 5/8" diameter hole x 5" deep into the fuselage to allow adding nose ballast. Then tossed in a 2-1/2" long 5/8" steel stud and temporarily secured that stud by jamming a small screwdriver beside it.

Swing test with the nose ballast shows it is now stable.

If you watch the video, I intentionally started swing the rocket slow... see how it doesn't look stable. And then when I pick the RPM's up, it becomes stable. If you view the video at 1/4 speed it becomes more obvious.​

As @BABAR suggested I did a swing test without any nose ballast, but with the tailcone covered.

That test was unstable. I removed the tailcone cover, and it also swing tested unstable.​

So what have I learned?

The base drag hack is over estimating stability caliber for this rocket configuration. That's confirmed by the swing tests, and by @Marc_G 's Estes logo rocket powered flight that also simulates as stable, but wasn't.​

Worth noting:

I reviewed one of the videos and I was spinning the rocket at 59 rpm at the end of a 7 foot string. That works out to 29.48 mph. Which is pretty nifty, since I always shoot for an off the rail speed that exceeds 30 mph.​

Time to make the motor / recovery spool, and figure out what I'm making the fins out of.

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[Daddyisabar]

No, no, no, it can't be that just more nose weight and thrust solve all the problems. I've always been told that rocket science is hard, needing years of top flight training at prestigious Universities, top end testing equipment, materials and procedures. They say more nose weight and power is just a crutch for exceededingly poor rocket design. My image and belief in elite, high end, expensive and exclusive rocketeering (not racketeering) has been totally shattered. With enough thrust the teaming masses can make bricks fly! Oh the horror.

 

[boatgeek]

No, no, no, it can't be that just more nose weight and thrust solve all the problems. I've always been told that rocket science is hard, needing years of top flight training at prestigious Universities, top end testing equipment, materials and procedures. They say more nose weight and power is just a crutch for exceededingly poor rocket design. My image and belief in elite, high end, expensive and exclusive rocketeering (not racketeering) has been totally shattered. With enough thrust the teaming masses can make bricks fly! Oh the horror.

As previously discovered on one of my monstrosities, the slogan should be "trust in thrust, just not on the first date."

 

[Raythain]

No, no, no, it can't be that just more nose weight and thrust solve all the problems. I've always been told that rocket science is hard, needing years of top flight training at prestigious Universities, top end testing equipment, materials and procedures. They say more nose weight and power is just a crutch for exceededingly poor rocket design. My image and belief in elite, high end, expensive and exclusive rocketeering (not racketeering) has been totally shattered. With enough thrust the teaming masses can make bricks fly! Oh the horror.

You have been told this because oddroc scum use the most heretical of measurements of success: fun per unit thrust.

The rocket code says that success shall only be measured in altitude per unit thrust. There is no fun, only efficiency.

 

[lakeroadster]

Papering Basswood

1/8" Basswood and 11 mil double sided matte paper. Using three of these for fins.

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[jqavins]

Here's my take on a rocket styled after the Estes Logo Rocket.

29mm power, rear eject spool.

I'm surprised Estes doesn't sell a kit like this?

@Marc_G took a stab at scratch building one of these back in 2012: Estes Logo Rocket... No idea how I'm gonna do it...

View attachment 582108
View attachment 582114

I just started reading this thread. It makes me want to do a NAR logo rocket.

 

[lakeroadster]

I just started reading this thread. It makes me want to do a NAR logo rocket.
View attachment 585169

Done... kinda sorta. Without the triangle, the rocket just looks like a rocket 3 pointed thingamajig.

 

[jqavins]

I don't understand. The NAR logo rocket has heavily swept back fins and its conical body does not extend aft beyond the fin roots. Apart from the conical body forward of the fins I don't see any resemblance.

(The NAR logo does make a nice decal on the Estes logo rocket. But putting a decal on a cone is easier said than done.)

 

[lakeroadster]

.... putting a decal on a cone is easier said than done.)

Not that difficult if you use MicroSol.​

I don't understand. The NAR logo rocket has heavily swept back fins and its conical body does not extend aft beyond the fin roots. Apart from the conical body forward of the fins I don't see any resemblance.

That's why I wrote...​

Without the triangle, the rocket just looks like a 3 pointed thingamajig.

Making the rocket on the NAR logo stable, while keeping its exact proportions, would be.. problematic. Which is more than a bit ironic.

 

[boatgeek]

Making the rocket on the NAR logo stable would be.. problematic. Which is more than a bit ironic.​

I feel like the white part of the NAR logo would be fairly easy to make stable. Keeping the fins from popping on every single flight is another matter entirely.

 

[lakeroadster]

I feel like the white part of the NAR logo would be fairly easy to make stable.

And you sir... are correct!

Keeping the fins from popping on every single flight is another matter entirely.

With rear eject... the tip of the cone hits first... better chance of saving the fins

 

[BABAR]

And you sir... are correct!


With rear eject... the tip of the cone hits first... better chance of saving the fins

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To quote Heinlein

TANSTAAFL*

Save the fins, risk the nose.


For flight, assuming you have some stability latitude, tape the forward inch of a nerf dart to the nose, otherwise that point isn’t going to last. Also kind of safer if there is a recovery system failure.

Probably just me. I like rear eject rockets, but not pointy tipped ones . Probably why I liked your Columbine.

*TANSTAAFL = There Ain’t No Such Thing As A Free Lunch

 

[lakeroadster]

To quote Heinlein

TANSTAAFL*

Save the fins, risk the nose.


For flight, assuming you have some stability latitude, tape the forward inch of a nerf dart to the nose, otherwise that point isn’t going to last. Also kind of safer if there is a recovery system failure.

Probably just me. I like rear eject rockets, but not pointy tipped ones . Probably why I liked your Columbine.

*TANSTAAFL = There Ain’t No Such Thing As A Free Lunch

So you're more of a "blunt force trauma" guy vs "impaling"?

The tip you see on my Estes Logo Rocket is as sharp as I'll ever build in regard to turning it on a lathe.

 

[Cape Byron]

*TANSTAAFL = There Ain’t No Such Thing As A Free Lunch

I beg to differ. In my younger years I had a number of free lunches with the old "Go outside for a durrie and just keep walking" routine.*

*Not recommended.

 

[BABAR]

For the Northern Hemisphere ignoramuses like me, a durrie (per Google) is a cigarette.

 

[Cape Byron]

For the Northern Hemisphere ignoramuses like me, a durrie is a cigarette.

I keep forgetting we speak different languages...

 

[lakeroadster]

Cutting and Installing Fins

S.O.P.: Cut the fins using the scroll saw, sand the fins using the table top disc / belt sander.

These aren't really TTW fins, but the grooves should provide a good strong attachment with the fin tabs. I peeled the paper off the fins at the tabs.

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[BABAR]

I keep forgetting we speak different languages...

Just get me a Vegemite sandwich and I’ll be good to go!