Wildman Sport CP/Open Rocket?

[Chris in Idaho]

Can anyone help me out? I've finished my Wilman Sport which is my first build bigger than an Estes Alpha 3. I downloaded Open Rocket and the Rocksim file from the Wildman website. In OR, I click "open" and the Wildman Sport file pops right up, but when I try to open it I get this:

So, is there something I'm doing wrong? I have very low computer knowledge...

Or, does someone know the CP location for the Wildman Sport? It's stock except for the 38mm MMT in place of 29mm, but that shouldn't have any aerodynamic effects. I was hoping to get OR to work so I could predict altitude with various motors, but I'd settle for the CP.

Here's the rocket:



Thanks in advance for any help!

 

[neil_w]

Please post the file.

 

[Chris in Idaho]

Here it is.

 

[Chris in Idaho]

I have an email in to Wildman, but I'm leaving tomorrow afternoon for the Sodblaster launch in Washington, so I'm hoping to get an answer ASAP. That's why I posted here, I figured a few of you must have one of these and might know the CP, or maybe I had made some simple error with Open Rocket that someone could point out.

 

[neil_w]

You only posted the RKT file, not the ORK file that generates the error.

However, OpenRocket opens that RKT file just fine. Looks like this:


Also attached here is an exported ORK file that opens fine for me at least.

 

[neil_w]

Note that motor configs don't import into OR from RKT files, so the above file has no motors or sims. Given the listed CP/CG *without* any motor, sure looks like some nose weight will be needed.

 

[Chris in Idaho]

Thanks Neil. I wish I was smart enough to know what I was doing wrong before, but it's working fine now. I've only ever downloaded this file one time so I have no idea what could be different. I guess you fixed it. Thanks!

 

[Chris in Idaho]

One more thing to note for anybody who finds this thread later, the nosecone in the sim file is 4 inches too short, the one that came with the actual rocket kit is 12.875" long. The body tube length and diameter are correct, but the nut on my aeropack retainer measures 1.95" and extends .625" past the aft end of the tube. Also the fin shape seems correct but the sim from Wildman has them too far forward, .875" from the aft end of the body tube while mine measure only .500" from the aft end.

With these adjustments, the CP comes out to 27.245". Now, I am NOT an Open Rocket expert or rocket designer, so please do NOT use my CP number for your rocket. My purpose here is just to warn you that you need to verify the measurements if you download the sim file from Wildman like I did.

Thank you!

 

[neil_w]

My purpose here is just to warn you that you need to verify the measurements if you download the sim file from Wildman like I did.

This advice applies to *all* sim files downloaded from the internet.

 

[JoePfeiffer]

This advice applies to *all* sim files downloaded from the internet.

Fixed it for you. Also, while this should go without saying, I'll say it anyway: check the weights (since this is a completed rocket, weigh it and override the mass and CG).

All that said, given Wildman's excellent parts and careful attention to detail with his fiberglass, I'm really surprised his .rkt file is so far off.