Estes OOP - Aero Fin
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Fore Check
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Estes BT-20B = 8.65" long
Here's a link to a handy reference chart for use in your future cloning endeavors:
https://www.ninfinger.org/~sven/rockets/body_tubes.html
Oh, and thanks for giving me a reason to look at that plan! I've always stayed away from the Aero Fin because I thought those tips were glued on at an angle, and it just didn't look sturdy.
Now that I've seen that the end result fins are "flat", I just may have to build one!
Here's a link to a handy reference chart for use in your future cloning endeavors:
https://www.ninfinger.org/~sven/rockets/body_tubes.html
Oh, and thanks for giving me a reason to look at that plan! I've always stayed away from the Aero Fin because I thought those tips were glued on at an angle, and it just didn't look sturdy.
Now that I've seen that the end result fins are "flat", I just may have to build one!
Fore Check
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Now yer talkin!
How about a 180% upscale, BT55 based with an E engine mount. You'd need a 15.5" long body tube, and a fairly common ogive nose cone.
Or, how about a 353% upscale, BT80 based with a 4 x E engine cluster or a 29mm mount and fly it on a G80. Whoopee!!!
How about a 180% upscale, BT55 based with an E engine mount. You'd need a 15.5" long body tube, and a fairly common ogive nose cone.
Or, how about a 353% upscale, BT80 based with a 4 x E engine cluster or a 29mm mount and fly it on a G80. Whoopee!!!
The latter is what I had in mind...
I've attached a pic of what I came up with in RockSim. I added forward fins to make it a little more stable. It's basically a bashed Executioner, which happens to be on sale for half price at Hobby Lobby this week
I've attached a pic of what I came up with in RockSim. I added forward fins to make it a little more stable. It's basically a bashed Executioner, which happens to be on sale for half price at Hobby Lobby this week
Fore Check
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Interesting...
The addition of forward fins *take away* from the stability of a rocket (which makes them easier to maneuver under guidance in practice, rather than in a straight and stable shot)
Now, five big honkin' fins probably provide a high degree of "overstability" and the addition of forward fins may lessen the degree of weathercocking involved.
Cool Idea! I was just pointing out that forward fins generally don't make a rocket more stable.
OK, so I'm decreasing the stability to bring the CP and the CG to within 1 caliber, right? I was playing with different settings in RockSim trying to get the rocket stable, and hit on the idea of forward fins.
Just so I understand what's going on:
if the rocket is not stable then the wind will pitch the nose over and the rocket will fly downwind of the launch site.
if the rocket is overstable then the wind will blow harder (I don't know the technical term) on the fins, pitching the nose into the wind. The rocket will fly up wind of the launch site.
It seems to me that a certain degree of overstability is a good thing, since the rocket will drift with the wind on descent. If you can get the amount of drift in either direction to match, then the rocket will wind up (theoretically, at least) back at the launch pad. This would minimize the amount of wandering through swamps that I have to do to retrieve my rockets
Just so I understand what's going on:
if the rocket is not stable then the wind will pitch the nose over and the rocket will fly downwind of the launch site.
if the rocket is overstable then the wind will blow harder (I don't know the technical term) on the fins, pitching the nose into the wind. The rocket will fly up wind of the launch site.
It seems to me that a certain degree of overstability is a good thing, since the rocket will drift with the wind on descent. If you can get the amount of drift in either direction to match, then the rocket will wind up (theoretically, at least) back at the launch pad. This would minimize the amount of wandering through swamps that I have to do to retrieve my rockets
shreadvector
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If your rocket is going FAST (with respect to the sideways wind) then overstability is a good thing. It will keep your rocket moving pretty much where you pointed the launch rod.
Slow rockets which are not overstable are very dangerous. The sideways wind will blow them sideways and if there is ANY misalignment of forward fins the rocket will steer wildly and possibly go unstable and start a fire when it crashes.
Slow rockets that ARE overstable will rotate and point into the wind (like a weathervane or weathercock). If the wind is high, that is also dangerous. I only fly slow rockets with little or no wind and I use as long a launch rod as possible to allow them to build up as much airspeed as possible. Estes Maxi V-2 with an E9-4 motor (abouot 1.1 pounds at lift off) uses a 1/4" dia x 6' long steel rod for perfect flights with little or no wind.
The worst Team America rockets that I saw were those with very low margins of stability. Those with high margins flew bullet straight. Those with low margins meandered all over the sky (or ground!)
Slow rockets which are not overstable are very dangerous. The sideways wind will blow them sideways and if there is ANY misalignment of forward fins the rocket will steer wildly and possibly go unstable and start a fire when it crashes.
Slow rockets that ARE overstable will rotate and point into the wind (like a weathervane or weathercock). If the wind is high, that is also dangerous. I only fly slow rockets with little or no wind and I use as long a launch rod as possible to allow them to build up as much airspeed as possible. Estes Maxi V-2 with an E9-4 motor (abouot 1.1 pounds at lift off) uses a 1/4" dia x 6' long steel rod for perfect flights with little or no wind.
The worst Team America rockets that I saw were those with very low margins of stability. Those with high margins flew bullet straight. Those with low margins meandered all over the sky (or ground!)
Originally posted by tmcqueen
OK, so I'm decreasing the stability to bring the CP and the CG to within 1 caliber, right? I was playing with different settings in RockSim trying to get the rocket stable, and hit on the idea of forward fins.
Just so I understand what's going on:
if the rocket is not stable then the wind will pitch the nose over and the rocket will fly downwind of the launch site.
if the rocket is overstable then the wind will blow harder (I don't know the technical term) on the fins, pitching the nose into the wind. The rocket will fly up wind of the launch site.
It seems to me that a certain degree of overstability is a good thing, since the rocket will drift with the wind on descent. If you can get the amount of drift in either direction to match, then the rocket will wind up (theoretically, at least) back at the launch pad. This would minimize the amount of wandering through swamps that I have to do to retrieve my rockets
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