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#11
I have Rocsim running on my Windows Vista, it had some issues at first but they did patches and it runs fine now. Also I make a point of checking for updates periodically. doing this will keep your version of Rocsim up to the latest version for free.
FYI, Tim VanMilligan designed Rocsim to run on his Apple computer, so if you use that type of system you should know that Rocsim will run best on it.
I just wanna fly ROCKETS!!

Dutch
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#12
(10-15-2012, 01:00 PM)Mike Dutch link Wrote:I have Rocsim running on my Windows Vista, it had some issues at first but they did patches and it runs fine now. Also I make a point of checking for updates periodically. doing this will keep your version of Rocsim up to the latest version for free.
FYI, Tim VanMilligan designed Rocsim to run on his Apple computer, so if you use that type of system you should know that Rocsim will run best on it.
Thanks, Mike.
(Raspberry) oh, brother... I guess I'm going to chance that with Window 7 laptop. I hope Timmy would be still hanging around longer.  :o
It is tough to see only one person, Tim VanMilligan, knows the programming, but no one else would be able to do this.

Ken Kressler
NAR#94955
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#13
Win 7 is a much more stable platform than Vista. You shouldn't have problems.
Evan Brown
NAR# 92851
Level 2
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#14
I run Rocksim on a fast win 7 desktop pc, a win 7 laptop that I bring to the launches, and have run it under XP.
No crashes ever, and it does what it claims.
It really helps with designs, coming real close on CP/CG distances, as well as calculating apogee delay times for various engines, etc.
No software is perfect, but this is pretty solid.
As to the cost - figuring what folks invest in their rockets, and their HP motors, this one time investment is peanuts...
Greg Young - L3
NAR #42065
TRA #00234
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#15
Nice discussion about RocSim and Open Rocket, but back to the subject at hand...My winter projects include this and something similar with a 38mm motor. The objective is to add nose cone weight, so that I can move the CG forward, allowing me to come up with a design that has the CP also far forward. This gives me much smaller fins which reduces my CD and allows me to gain much higher altitude even though there is almost a half pound of weight in the nose cone of a 2.26" diameter rocket. Weight distribution-wise, it is like a baseball bat with fins. The 38mm DD design sims out at 7,500' with a J530 motor even though it is a 3" airframe. That will break mach (close to 1.3), so I am going to try my hand at wrapping a cardboard tube with fiberglass.
Evan Brown
NAR# 92851
Level 2
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#16
buy a sock from soller composites . com .  No easier way to do fiberglassing of a tube. 

Your minimal fin and "bottle rocket" stability design is a questionable practice IMHO-  I bet that rocket will cone and generally thrash around on the way up.  Dynamic stability issues.

N
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#17
Part of the rear stability is regained by using 4 fins instead of 3. In the component analysis of OR, it suggests that there may be issues with roll, but pitch and yaw should be OK. If there is greater roll, the angular momentum generated will also increase stability.

A bottle rocket's stability is gained by having the stick aft of the thrust component (you can get higher altitude if you break the the bottom 3-4" of the stick off) and if the stick is warped, it impacts the aerodynamics. Not sure that analogy fits here.

Minus the gyros, this configuration of weight placed far forward and smaller fins is more consistent with commercial/governmental rocketry. Some rockets being launched have no fins at all. Since placing gyros in small rockets is not practical, we need some fins for stability to compensate.

General rule of thumb is one diameter of distance between CG and CP. If that can be attained moving the CG forward and instead of the CP aft, it should still still work. That was an L2 exam question. Is there a guideline that says the CP must be no more than a certain percentage of the rocket length forward from the bottom of the rocket?

The key I think is to make sure there is a strong boost at the launch. It may get more squirrelly on lower power motors than higher power. If it leaves the rail at a high rate of speed it should be OK. My Delta Clipper is a narrow pyramid rocket that has no fins and about 2 oz. of clay in the nose. When it flies on a C6-3, it gets a little squirrely. However if I fly it with a D21-7, it goes straight.

Also not sure I would do this for minimum diameter. You gain a modicum of stability when you use a 29MM motor in a 54mm tube instead of a 54mm motor (think of the rocket as a very narrow pyramid in that configuration).

Attached is a 38mm motor version using a 3" airframe. It uses 12 oz. of weight in the nose. The added DD weight also helps as well.

[attachment deleted by admin]
Evan Brown
NAR# 92851
Level 2
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#18
That fin area doesn't seem radically small to me to cause flight problems. 
John Derimiggio
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#19
Evan,
I am definitely going to have agree with JD here on the nose cone descent rate.  20 fps is the standard accepted safe rate.  Sure defects occur that cause pieces parts to occasionally descend faster but not intentionally!

As far as fiberglassing... i think everyone should try it- at least once.  That way they will never complain about the price of fiberglass tubing again!
Chris Prinzi
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#20
I'll make sure it lands OK. Just means that it cannot fly on windy days.
Evan Brown
NAR# 92851
Level 2
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