Open Rocket & CFX Six Footer

Hello,

I launched a few rockets with friends when i was in middle school/high school in the early to mid '90's but I have an 8 year old boy now & I'm getting back into it with him.

So of course being a fan of the Mean Machine I bought the CFX Six Footer because of it's similarity. I see the package says it can go 600' and only recommends the D12-5 engines. I downloaded OpenRocket in case I wanted to make any changes to the design & if I did it right it's saying it will top out around 200' with the D12-5 engine. This was with the downloaded file from apogeerockets.com

Is the OpenRocket software way off on this one or am I doing it wrong? Other rockets seem to be much closer to the advertised estimates. Apogee also said rocsim estimated 540'.

Thanks

My Custom Rocket Equinox hit just under 400’ per the altimeter and the three teams of students using altitude trackers at a school demo launch - considering the smaller diameter and slightly lower weight 540’ on an ideal day seems reasonable for a CFX. Rocsim files can be a little wonky in OpenRocket, I typically verify all the component weights and all the variables (like launch rod length, geoloc, wind, temp...etc) when using an .rkt vs .ork file in OR.

OR should be very accurate. Double check the weight shown on the package vs. what shows in the sim. Also check fin width. As the saying goes, garbage in garbage out.

I have had sims run to within 20ft of the actual flight with weight and CG override along with the correct surface finish.

...also advertised altitudes are about 10% higher than real world results. Should be close.

Cabernut said:

OR should be very accurate. Double check the weight shown on the package vs. what shows in the sim. Also check fin width. As the saying goes, garbage in garbage out.

I have had sims run to within 20ft of the actual flight with weight and CG override along with the correct surface finish.

...also advertised altitudes are about 10% higher than real world results. Should be close.

Click to expand...

Thanks for the info.

I felt pretty confident that it would go higher than 200ft from looking at what others had done and remembering what the Mean Machine did. I even took a look at the Mean Machine’s numbers. Both in OpenRocket and from old Estes catalogs. (I believe Estes was usually higher on the altitude estimates).

I know there’s no guarantees, but I was trying to estimate a field size and if it was really only going to go 200ft, I’d probably worry much less about wind drift.

Just to tempt you....the other way to ensure a stable flight and more altitude is to use more powerful motors. I just built the Equinox with my son, and I'm thinking if flying it in an E30. (Of course, that will necessitate a bigger field.)


Sent from my iPhone using Rocketry Forum

By the way, I downloaded and ran the same file on a D12 and got over 450'. Maybe re-unzip the .rkt file and add the D12 simulation again.