Bizarre scratch build

My friend Mat is finishing completely this scratch he is working on. Its a 3" carpet roll with a LOC nose cone. It has 1/4" ply fins, center rings. It fly's on a 38 and weighs in at 2.1 lbs so it pretty stout. Just thought I would share some pictures and see what you guys think. It hasn't been simed yet.

that's a little tank of a rocket. I like the fins and overall shape but it's got to be pretty ass heavy with the thick fins and body tube and a light nosecone. who builds a rocket without siming it first?

Looks pretty cool and I like the look of it.

But I have a name: death spiral

I was thinking sky writer or duck and cover

RKeller said:

that's a little tank of a rocket. I like the fins and overall shape but it's got to be pretty ass heavy with the thick fins and body tube and a light nosecone. who builds a rocket without siming it first?

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Don't worry its definitely a "HEADS UP" flight

RKeller said:

I was thinking sky writer or duck and cover

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All the names are cool but "duck and cover" I like the best

RKeller said:

that's a little tank of a rocket. I like the fins and overall shape but it's got to be pretty ass heavy with the thick fins and body tube and a light nosecone. who builds a rocket without siming it first?

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I build rockets without simming them first all the time.
John Boren, AKA JumpJet, does too, so before you go acting all holier than thou...
There's a lot to be said for common sense and experience.


That said, I don't understand why the modeler went with such a design, as far as the heavy thick materials go.
From the looks alone it would seem you'de have to practically fill the nose cone with lead.

TopRamen said:

I build rockets without simming them first all the time.
John Boren, AKA JumpJet, does too, so before you go acting all holier than thou...
There's a lot to be said for common sense and experience.


That said, I don't understand why the modeler went with such a design, as far as the heavy thick materials go.
From the looks alone it would seem you'de have to practically fill the nose cone with lead.

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Theres no weight in the nose cone

AfterBurners said:

Theres no weight in the nose cone

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Then you might want to get behind and under something solid prior to launch.
It's HPR though, so I'm sure a responsible RCO won't let it fly anyhow.

TopRamen said:

I build rockets without simming them first all the time.
John Boren, AKA JumpJet, does too, so before you go acting all holier than thou...
There's a lot to be said for common sense and experience.


That said, I don't understand why the modeler went with such a design, as far as the heavy thick materials go.
From the looks alone it would seem you'de have to practically fill the nose cone with lead.

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no "holier than thou" intended. not saying you can't or shouldn't, I like to put all my crazy ideas into the simulator so I can see them first.

AfterBurners said:

Theres no weight in the nose cone

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ok, then it's "Lindsay Lohan".......... similar stability and driving

RKeller said:

no "holier than thou" intended. not saying you can't or shouldn't, I like to put all my crazy ideas into the simulator so I can see them first.

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Sorry, I took it the wrong way.
Now that I know how to do Sims, I do typically utilize them, but even one 3x24mm BT-80 based scratch build I'm currently doing is almost finished after beginning it about 6 months ago, and I just barely did the Sim for it last week.

RKeller said:

who builds a rocket without siming it first?

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ME!!! I don't Sim and I don't OR. Never have, never will. I've been doing this stuff for 45+ years now, and learned how to design by trial and error. These days, I have 1 in 50 rockets that have stability issues. I will not become dependent on software to do my thinking for me!

Gary Byrum said:

ME!!! I don't Sim and I don't OR. Never have, never will. I've been doing this stuff for 45+ years now, and learned how to design by trial and error. These days, I have 1 in 50 rockets that have stability issues. I will not become dependent on software to do my thinking for me!

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I don't sim my designs either. Like Gary, I have learned by doing, experimenting, and sometimes failing. Over the years, I have developed an intuitive understanding of materials and of the nuances of stability. When I designed the Fractal, I *KNEW* it would be stable. (I had some concerns about its structural integrity, but I don't think OR or RS address that anyway).

There are times I fear that the dependence on software during the design stage, has a side effect of diminishing creativity.

Now, I *do* run general sims via Thrustcurve.org to help me with motor selection - but that is just cranking out the math. I use Grey Matter version 5.9 for cranking out the creativity.

I thnk the point is, with this being an obvious failure, the builder is not yet ate point of designing without some help

To the folks who don't run sims. Have you ever tried the card board cut out barrowman method of getting your Cp location? It is super easy, doesn't require any math and would help with those crazy projects that might be riding the hairy edge stability.


Sent from my iPad using Rocketry Forum

Random Flying Object said:

To the folks who don't run sims. Have you ever tried the card board cut out barrowman method of getting your Cp location? It is super easy, doesn't require any math and would help with those crazy projects that might be riding the hairy edge stability.

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I know we've known how to do that since we were kids. I can't speak for LW since I'm not sure if he still does, but I never do it. Just a waste of good cardboard if you ask me.

Really,

I think the only problem is with the short, stubby, butt heavy rockets or any combination thereof. I think a flier can avoid problems purely based on past experience so those who say "I never sim" I can appreciate that.
I like to run a sim if I'm getting close to a ceiling or if stability is marginal. Flew a short stubby job that sim said "ok" but it went off at 25 degree angle first flight. Recovered fine but in went more nose weight. Now all is well.
People need to realize a sim is an educated guess that is not infallible. Kurt

Random Flying Object said:

To the folks who don't run sims. Have you ever tried the card board cut out barrowman method of getting your Cp location? It is super easy, doesn't require any math and would help with those crazy projects that might be riding the hairy edge stability.


Sent from my iPad using Rocketry Forum

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I don't bother with that. I try to visualize the CP, but I'm mostly concerned with CG and that I can actually feel as I hold the rocket or balance it on my finger.

I really like the looks of the rocket, design is straight forward and sharp.
I wish you the best on your first launch, and please post pics after it's been given paint, please.
Keep building, you only get better, and it only gets fun-er!

I could see this rocket with a Steampunk paint scheme, some rivets, and maybe a porthole.

Comments regarding stability, heads up launches, etc, notwithstanding.

Gary Byrum said:

I can't speak for LW since I'm not sure if he still does... <snip>...Just a waste of good cardboard if you ask me.

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TopRamen said:

I don't bother with that. I try to visualize the CP, but I'm mostly concerned with CG and that I can actually feel as I hold the rocket or balance it on my finger.

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Gary, I have not done the cardboard cut-out method since the Nixon administration. That's around the time I graduated from simple 3-4FNC designs. By then, like TopRamen, I had learned to visualize the CP.

I will admit the more difficult designs are the short, fat ones. Then, it becomes a question of not whether nose weight is needed, but rather how much is needed?

Woody's Workshop said:

I really like the looks of the rocket, design is straight forward and sharp.
I wish you the best on your first launch, and please post pics after it's been given paint, please.
Keep building, you only get better, and it only gets fun-er!

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This one has to earn its paint

AfterBurners said:

This one has to earn its paint

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Joking aside, this one needs another foot or so of bodytube or some serious noseweight. It currently has zero chance of a safe flight, and should not be launched as is.

DizWolf said:

Joking aside, this one needs another foot or so of bodytube or some serious noseweight. It currently has zero chance of a safe flight, and should not be launched as is.

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I was just browsing the forum, but had to log in to second this suggestion.

Let's not forget that mind-simming with many years of experience is a completely valid way to go.

I mindsim both rockets and RC aircraft and never have any issues.

tab28682 said:

Let's not forget that mind-simming with many years of experience is a completely valid way to go.

I mindsim both rockets and RC aircraft and never have any issues.

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It works just fine when you're using wide safety margins. In essence, you're guessing and using experience.

But all of that isn't the point, the point is this obviously doesn't pass, which is why a sim was mentioned. Because the mindsim of this designer was a failure. Thus, all the hundreds of people who can successfully mindsim are irrelevant.

I mindsimed this one real quick like and got scared. I got that big lead ball in the tummy feeling. I know that big lead ball is just a bunch of no good, stinking, performance robbing nose weight. Or maybe it was those two Quarter Pounders I had for lunch with the buy one, get one free coupon.

On this one I would use every tool I could, even going as far as putting it in the computer as it doesn't look too hard to do with this design. I sure can't hurt. You got the tools. You got the talent. Maybe trying to simulate the materials and weight would be an issue? Where is the carpet roll listed in the body tube section? Oh well, try for not too much garbage in, garbage out, but at least you have a computer verified sim and that is like a golden ticket. Folks love those sims.

Awhile back some kids came to the launch from an engineering school recently ranked first in the nation and they looked a whole lot at their laptop screens and not much at the rocket. Awesome dude, the guys couldn't have been happier.

Then I came up with the Beech Staggerwing and well. . . um. . .er. . . I like that term irrelevant!

Now I know how Data must have felt when the Borg would not assimilate him. Primitive android utilizing a positronic matrix, there is no place for you in the collective, you are irrelevant. And then to make things worse I got the big lead ball in the tummy feeling. Then the Sheriff and Park Ranger showed up. I could have really used the comfort even a garbage sim could have provided, I just wanted to huddle up with the laptop on the couch and make all the fears go away.

"Irrelevant data can act only as a distraction, therefore I shall ignore you." I need to pull out that old VHS tape and watch the classic 70's Sci-Fi movie Dark Star again. Hey guys, I was just watching a movie where they talked to bombs and I thought the Dark Star would make a cool model rocket. That is when I will learn the RSO is a big Seinfeld fan and he will invoke one of those classic episode phrases "Go to the back of the line, no soup for you!"

I guess in the end over reliance on one method and eventually you will be burned. The question is how long do I have? Whats that you say Mr. RSO? Time has already run out for this mindsimmer?:sad:

Have you been snorting the AP? You need to INJECT that.

Last time I saw a big engineering school project it snapped in half under boost. Apparently they didn't sim coupler length or fit. :/

DizWolf said:

Have you been snorting the AP? You need to INJECT that.

Last time I saw a big engineering school project it snapped in half under boost. Apparently they didn't sim coupler length or fit. :/

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No, just too many years filling balsa with old school dope. With the AP you really have to mesh it down and get out the powdered sugar.

Kids these days with their computers. Old farts with their fuel proof dope.