Looking For Help With New Rocket......Loc ? V -2

[gregtro]

I bought this rocket at a launch last weekend.
It is a 7.5'' V-2
80'' long.
54mm motor mount.
My problem is I don't know where the cp. is.
The rocket has not been flown.
I was unable to get any further info from the seller
because someone bought this as part of a package from him
and later sold me the rocket.
Can anyone help me ?

T.I.A. Greg

 

[Chuck Rudy]

Here ya go, go nuts!

https://my.execpc.com/~culp/rockets/Barrowman.html

 

[gregtro]

Wow !
Looks like I'll be brushing up on my algebra !!!

Thank You !!!

greg

 

[dr wogz]

Wouldnt there be a rkt. file available for Rocksim?

It'll point out teh CP

 

[Ryan S.]

I think it is about half a caliper in front of the fins.

I would suggest a 75mm mount for this rocket it will come in handy, though you may need more noseeight.

 

[jetra2]

Yeah - there's likely a Rocksim file available on EMRR. Go to the Rocksim database - I'm sure someone's submitted a V-2 file at SOME point.

Personally, I would recommend trying it with pencil and paper just once, to see how it goes. Also...remember when you have a fraction under a radical sign...each part gets their own radical...I think that was my mistake when I tried and failed on pen and paper.

EDIT: Here's a link to the LOC 5.5" V-2 RSim file.

Jason

 

[GL-P]

Got rocksim???

https://www.rocketreviews.com/cgi-bin/rocksim/rocksim.cgi?V2&&search

At the bottom there is a file with a full scale V2 which should have the Cp

Just right click and go to "save link target as"

 

[JStarStar]

If the proportional profile of the V-2 remains consistent (i.e. same length-diameter ratio, profile of the nose cone and tail cone, and fin size) from one model to the next, wouldn't the CP remain in the same place, relatively, for all scale versions??

 

[GL-P]

If the proportional profile of the V-2 remains consistent (i.e. same length-diameter ratio, profile of the nose cone and tail cone, and fin size) from one model to the next, wouldn't the CP remain in the same place, relatively, for all scale versions??

Yeah it would have the same Cp location in proportion to the rest of the rocket.

I just said it was full-scale cuz it makes it fun to play around with and someone must've put a lot of time into the design to make sure it's accurate.

The only way it could change is if the rocket goes mach. The small scale ones can't but the full scale one does which pushes the Cp backward. Nothing to worry about at this small size.

 

[Dbarrm]

COOL, now I can figure all this out for my stick rocket.

Dan

 

[Stymye]

the loc v2 appears to be much longer than scale, one other dimension nice to know would be the fin span
so 1/2 caliber ahead of the fin junction would be a good ballpark guess
a scale v2 is right at the fin to BT junction.

 

[rdbones]

QUOTE:
Wow !
Looks like I'll be brushing up on my algebra !!!

I said that same thing when I used the formula's from that page to calculate teh CP on my scratch built.

The one thing I suggest - spend the $10.00 and get a scientific calculator and use it (with the parentheses). It will make all the difference in the world !

That or go to the bottom of the web page - open his spread sheet and plug your numbers in !

 

[Stymye]

while it's nice to practice those math skills
are we still in the stone age?
way back in 1973 it was determined that Barrowman will get you an overstable rocket..not necessarily a bad thing, but hardly accurite

 

[GL-P]

We don't really need to be accurate in this hobby. When your job is a rocket scientist then you need it but. I would prefer overstable to understable

 

[Stymye]

We don't really need to be accurate in this hobby. When your job is a rocket scientist then you need it but. I would prefer overstable to understable

Gl-p, you missed my point,
I'm not knocking the Barroman equasions by any means,just adding that we have come a long way in this hobby since those calculations were published and perhaps some future rocket scientists WOULD like to learn more as they progress, obviously you don't, and that is perfectly alright,as it does not make the hobby less enjoyable.but I think learning more, is an important part of the hobby for each individual to persue if they have the desire

In alot of my posts to this forum I might try to take the subject a little further ,I definately ask alot of questions and on rare occasions I hope I add something meaningfull to the disscussions.
I'm beginning to think mabey some people miss-read this as having a know it all attitude,and that is not my intention.but I can see that is the perception

so I think it's time for me to take a break, permanent,I'm done here

 

[gregtro]

Thanks to everyone for the replys !

To Stymye,
Yes this rocket is longer, 15'' I believe.
The fin span at the very aft end is 7''
I'm trying this Barrowman thing but I must be doing something wrong as I keep getting a cp at 11'' from the tip of the nose cone

greg