lakeroadster
When in doubt... build hell-for-stout!
Say What? A Flying Sword? Yep. The 24mm rear eject spool makes it possible. The handle is BT/C-188 and the pointy end is 1/4" plywood.
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"X-Caliber" - A Scratch Build
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Soooo, if you get a ballistic return do you need to resurrect Arthur to extract it?
That's not a heads up flight. That's a oh ****, everyone run flight. 
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NTP2
Well-Known Member
I say make it a Gladeus instead of a German long sword. The better to threaten a RSO with
Swords? Space?
Hm...
Hm...
lakeroadster
When in doubt... build hell-for-stout!
I say make it a Gladeus instead of a German long sword. The better to threaten a RSO with
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lakeroadster
When in doubt... build hell-for-stout!
And the Lady of the Lake, her hand covered with shimmering samite, did thrust the Excalibur rocket from the bosom of the water. Blessed are we all!
If unstable just say you are scale flying the Mysorean rocket sword.
The British East India Company will not be pleased.
The British East India Company will not be pleased.
NTP2
Well-Known Member
I love it!!
lakeroadster
When in doubt... build hell-for-stout!
The long Sword has a stability caliber of 2.73,
the Gladeus Sword has a stability caliber of 1.15
No doubt in my mind.... they are stable.
NTP2
Well-Known Member
Ahh so it’s better, I know how much you oddrok people love a less stable rocket!
lakeroadster
When in doubt... build hell-for-stout!
Not me. I check the stability with calc's... update the calc's as the build progresses, and then verify with swing tests.
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NTP2
Well-Known Member
Ohh I just thought you are all like @Daddyisabar
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Okay, that brings back some memories of a certain CHAD staged Twin Factor flight……
Mindsim has always worked for me...except that one time, but the RSO was in Italy and it was the last launch of the day.
Making your rocket stable is easy until you push the envelope too far. Trust in thrust. Love that no good, stinking, performance robbing nose weight!
Purposely make them go unstable only to frighten the British.
A good Scottish Claymore two handed sword would be cool. Dress up like Mel Gibson with the kilt and woad face paint for historical accuracy!
Strange people lying in ponds with a copy of Open Rocket is no basis for a system of government.
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And I'll see that and raise you modern Sword and Sorcery/ Space Metal
Double post
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Well-played, old chap!
lakeroadster
When in doubt... build hell-for-stout!
Final simulations... time to fire up the CAD station.
Good God man, another one already?!
Long rockets need greater stability margins than more "normal" looking ones, when measured in calibers. (And short ones need less.) Some say that, because of this, it's better to measure stability as the CG to CP distance divided by the length, rather than dividing by the diameter; by that measure, it is said, one should aim to have at least 10%. You have 4%. There's a very good article on it here. Considering that, the design looks marginal to me; I'd go for three calibers or better.
Would increasing the fin span, pushing the shields out further hurt the look?
Long rockets need greater stability margins than more "normal" looking ones, when measured in calibers. (And short ones need less.) Some say that, because of this, it's better to measure stability as the CG to CP distance divided by the length, rather than dividing by the diameter; by that measure, it is said, one should aim to have at least 10%. You have 4%. There's a very good article on it here. Considering that, the design looks marginal to me; I'd go for three calibers or better.
Would increasing the fin span, pushing the shields out further hurt the look?
lakeroadster
When in doubt... build hell-for-stout!
Yeah... quite the pile o' rockets.
Bad link?
How's this? Added a 1/2" to the rear fin height and made the sword 1/2" plywood (Glued up 1/4" thick 2X)
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I may be missing something here (not the first time.)
Can you post a top to bottom view (90 degrees from the one you have.)
IOW, is the sword blade FLAT? Or at least not perfectly cylindrical?
You always make thing work, but this one if flat will definitely need two swing tests at 90 degree difference. Depending on the degree of “flatness” the nose end is gonna have a tendency to act like a forward fin in the yaw axis as currently pictured.
As @neil_w has said, there is little that some depleted uranium won’t cure.
Can you post a top to bottom view (90 degrees from the one you have.)
IOW, is the sword blade FLAT? Or at least not perfectly cylindrical?
You always make thing work, but this one if flat will definitely need two swing tests at 90 degree difference. Depending on the degree of “flatness” the nose end is gonna have a tendency to act like a forward fin in the yaw axis as currently pictured.
As @neil_w has said, there is little that some depleted uranium won’t cure.
I'm not sure about OR, but I know this is true of RS: it computes the CP from all angles around the rocket axis, and reports the minimum value. You can see the values all the way around on a special view. I would bet that OR does this too.
lakeroadster
When in doubt... build hell-for-stout!
The blade is made from (2) pieces of 1/4" plywood, glued together and inserted / glued into a solid wood bulkhead (nose cone).
Stability during flight has a min caliber of 2.77 and a max caliber of 5.50
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Yeah, @Daddyisabar , I know, fear is the mind killer.
I’m a complete ignoramus with OpenRocket, but my mind-sim simulates the forward 3/5 of the rocket as a single fin, all of which is forward of the CG. From an aerodynamic standpoint, I would expect a bad positive feedback loop in yaw axis.
I’ve got a bad feeling about this.
As usual, I fully expect @lakeroadster to prove me wrong.
The standard solution of more nose weight will be a challenge, as there is no forward compartment to place any metal mass, and @lakeroadster is admirably committed to follow the low power safety code and not use metal as part of the nose itself (plus while significant accidents are rare, NAR INSURANCE is likely to frown on covering a sword shaped rocket with a metal nose cone that causes significant fecal turbine interaction.)
The other solution is more fin surface area in the rear, maaaaybe there is already enough there.
On the good side, @lakeroadster is one of the few forum members that actually documents swing tests on everything, so the situation will be known before the creation even sees the launch pad.
I’m a complete ignoramus with OpenRocket, but my mind-sim simulates the forward 3/5 of the rocket as a single fin, all of which is forward of the CG. From an aerodynamic standpoint, I would expect a bad positive feedback loop in yaw axis.
I’ve got a bad feeling about this.
As usual, I fully expect @lakeroadster to prove me wrong.
The standard solution of more nose weight will be a challenge, as there is no forward compartment to place any metal mass, and @lakeroadster is admirably committed to follow the low power safety code and not use metal as part of the nose itself (plus while significant accidents are rare, NAR INSURANCE is likely to frown on covering a sword shaped rocket with a metal nose cone that causes significant fecal turbine interaction.)
The other solution is more fin surface area in the rear, maaaaybe there is already enough there.
On the good side, @lakeroadster is one of the few forum members that actually documents swing tests on everything, so the situation will be known before the creation even sees the launch pad.
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