Where do I get the Rocksim file for a 54mm Acme Fin Can ???

Hi Guys,
I'm building a minimum diameter 54mm rocket.
I have an Acme fin can for the rocket.
I have a minimum diameter Aeropac retainer for the rocket.
This retainer gets epoxied into the airframe at the height of the longest motor you intend to use.
This retainer leaves you with a stud to screw the threaded forward closure onto.
Or,,,, if you'd like to fly with a shorter motor, you can screw a rod coupling onto it,
and a piece of threaded rod.
This way you can fly any length motor you'd like, up to the longest motor you epoxied the retainer in for.

Anyway, this whole build begins with the decision, how high to epoxy in the retainer.

To make this decision, I need the Rocksim file for the Acme fin can so I can build the rocket in Rocksim.................

Teddy

Giant Leap doesn't provide an Acme fin can in their Rocksim database. You can easily build it via airfoil fins and a sleeve of proper dimensions. Make them solid polystyrene to start with and see how close you get to the weight specs Giant Leap provides and then, if needed, just adjust and/or add an item to the materials database. Here are the needed specs for the fin cans: https://www.giantleaprocketry.com/docs/acmefincans.pdf.

onebadhawk said:

Hi Guys,
I'm building a minimum diameter 54mm rocket.
I have an Acme fin can for the rocket.
I have a minimum diameter Aeropac retainer for the rocket.
This retainer gets epoxied into the airframe at the height of the longest motor you intend to use.
This retainer leaves you with a stud to screw the threaded forward closure onto.
Or,,,, if you'd like to fly with a shorter motor, you can screw a rod coupling onto it,
and a piece of threaded rod.
This way you can fly any length motor you'd like, up to the longest motor you epoxied the retainer in for.

Anyway, this whole build begins with the decision, how high to epoxy in the retainer.

To make this decision, I need the Rocksim file for the Acme fin can so I can build the rocket in Rocksim.................

Teddy

Click to expand...

If you are using an acme fin can, you might as well use a slimline aft end retainer and avoid the hassle. I believe the fincan matches the outside diameter of the retainer.

dixontj93060 said:

Giant Leap doesn't provide an Acme fin can in their Rocksim database. You can easily build it via airfoil fins and a sleeve of proper dimensions. Make them solid polystyrene to start with and see how close you get to the weight specs Giant Leap provides and then, if needed, just adjust and/or add an item to the materials database. Here are the needed specs for the fin cans: https://www.giantleaprocketry.com/docs/acmefincans.pdf.

Click to expand...

You are a man among men !!!!!!!!!!!!!!!!!!!

This will be my first from scratch build in Rocksim,
but I kinda get what to do and where in Rocksim to go,
and I definitly understand what your saying.........

I basically have to do the same thing you said with the airframe and nose as well.
I got 54mm filament wound glass frame and same Von Karmen nose from Tim Lehr.
Beautiful material, but neither of these items are in Rocksims database, so I'm going to
call Tim and get specs and enter the items spec by spec...........

Until now, I'd just download a rockets file and start from there.
I mostly just used Rocksim to jive out motor selection and project altitude
so I don't take chances with the clubs waiver.

First, specs on Tims material, then when thats in, it will let me mess around with the fins.

Thank you very much Dixon,,, I'll poke around,,,,,Teddy

I dont remeber where, but theres a well done model of it avaliable on rocketreviews. Just insert it as a subassembly and save it to the rocksim database. Works like a charm!

awseiger said:

I dont remeber where, but theres a well done model of it avaliable on rocketreviews. Just insert it as a subassembly and save it to the rocksim database. Works like a charm!

Click to expand...

I have the design file for the 54mm Acme can.................

You better hope I don't find out who you are cause I'm gonna kiss you on the lips.............

Easy peasy toooooooooooooooo...........

Thank you so muchhhhhhhh

Teddy

Here they are:


View attachment acme_54mm_fin_can.rkt

View attachment acme_38mm_fin_can.rkt

Thank you so much guys,
I got it.
I did a search on rocket reviews and found it.
I downloaded the file for it.
And Tim told me to just download the file for any rocket from his site that is a 54mm airframe.
I have everything I need.
I already built the rocket,,,,, very cool,,,,,, I never built my own on Rocksim before........
I have 2 concerns right now.
It won't launch because theres no motor tube,,,,,,, it's 54mm minimum diameter,,,,,,,,
I'm going to use a Aeropac internal motor retainer,,,,,I don't see any provision for this anywhere.

And,,,,, It says the rocket is 10.63 overstable,,,,,,,

I have an extra long payload section on my 3" Wildman Intimidator,,,,
It says thats more overstable,,, I think 25 or so......

I'm not understanding what overstable means...........

Thank you again guys,,,,,,,,,,,,Teddy

I have to tell you that adapters and such for minimum diameter retention with shorter motors is a pain.

The acme fincan already sticks out past your airframe do you can use a slimline retainer without an aerodynamic penalty.

If you load a motor then your stability will normalize.

Yes, and it wont let me load a motor till I jive out the issue with the motor tube.
No, but thank you anyway,,,, I'm going to stick with the internal retention..............
Teddy

Put a check mark in the box says this is a motor mount and choose the size from the drop down.

10.63 Overstable!!!! :surprised: That's the stability you'd expect from a rocket with 5-square foot fins, 12 feet long carrying a few lead ingots!

Not really, but you should really check your simulation. Something is very wrong. It is also possible the rocket is 10.63 over-stable without a motor in it, but this still seems a little odd.

If you have the rocket constructed already, measure the final mass and Center of gravity in real life and put it into the mass override section. However, if you override the whole rocket, putting motors into your simulation will not move the CG. I would Measure the mass and CG of the nosecone, and then the rest of the rocket. That way, there's two "mass objects" in the simulation and the motor's mass and position will change your stability rating.

Also, Overstable means that the Center of pressure is far more than 1.0 Body tube diameters behind the Center of Gravity. Someone correct me if I'm wrong but I think with Rocksim the error pops up at 2.0 body tube diameters. Usually, it means that your rocket will weathercock horribly. a 10.63 over-stability margin means you have built a windseeker, and any wind will cause the rocket to fly sharply into the wind. It's not un-safe per say, as the rocket is stable, but you should try not to have rockets be *that* over stable in launch configuration.

Also, to answer your very initial question, put it in with a 6XL case (or the longest AT case). You don't want to limit yourself! I always make my rockets able to take the biggest motor that fits in their motor mounts. I'd hate to be at Black Rock with all my rockets, unable to launch more than 5000 feet.

If you post up your file, I can give it a look.

There it is...................how ya like me now,,,,,,,,,,,,,,,,,,

View attachment Altitude Seeker.rkt

Sorry Alex,
I dont know how to post the file.
Teddy

Terry,,,thank you,,,that worked,,,,,,,,,,,,,