Does adding Saturn V engine bells change CP

I am upgrading my Estes Saturn V and was wondering if adding the engine bells for launch not display changes cp. This would make it a lot easier to sim in rocksim if I can just add mass to the bottom of the rocket to see how much weight to add to the nose. I think this would not work if cp changes though. I've downscale the Apogee SV and am using that but changing weights etc. Bad or good idea?

The air is so disturbed by the time it gets down there that I doubt that it makes any difference in the CP. The weight at the very bottom affecting the CG is going to make a lot more difference...

Perfect, thanks for the help. I was a little concerned because adding mass to the bottom doesn't change the cp in rocksim. only the cg. I'm not skilled enough to add the engine bells so I'm hoping to add mass to the very bottom and correct for cg.

FWIW, I spent a lot of time modding mine to be able to fly the bells and had a fair amount of hassle getting it stable, but at the end of the day I don't think the bells add much to the visual appearance of a flight. You may feel otherwise, just my experience.

mikec said:

... but at the end of the day I don't think the bells add much to the visual appearance of a flight.
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I don't know, I think the engine bells add quite a bit visually.

I've added a 29mm mount, plywood cr. I also have a really long mm tube to transfer some of the weight forward. I hope all that will help a little.

And I have to agree, that looks amazing. I love all the SV launch pics but 90% are with no nozzles. Just trying to learn though.

mikec said:

FWIW, I spent a lot of time modding mine to be able to fly the bells and had a fair amount of hassle getting it stable, but at the end of the day I don't think the bells add much to the visual appearance of a flight. You may feel otherwise, just my experience.
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It probably doesn't make much difference after the first second or so when you can't really see it, but it sure makes it look better on the pad. Ditto for the LES, too.

Much depends on exactly how you put the bells on and the rest of your build. In mine, the nozzle of an AT E20 was about 1/2 inch or so below the main BT in a short MMT glued to the display engine bell assembly where the center engine was, and that MMT inserted with a coupler into the stock MMT. With about 2.2 oz of nose weight in the CM for the Apollo 11 configuration, this was marginally stable and ended up ascending at about 45 degrees, late ejection, etc. The SIVB part of the rocket was so heavy that with the off-vertical flight it stripped the chute and the CM/LES was trashed on impact. So beware. I think the fins on the Saturn V are small enough that even if it checks out in the sim, a little wind or rod whip can lead to instability.

It did look good on the pad.

I modified my 1969 Saturn V model to have the 4 bells attached during launch, I shortened the MMT about an inch from the end of the bells... Added about 3.5 oz extra weight in the CSM, and launched with an Aerotech E-15-4.... Flew fine, and in November, it’s gonna fly again on a bigger Aerotech for the Apollo 12 50th Anniversary!

Here's the video of the launch...Two shroud lines broke during the booster recovery, but for the Apollo 12 launch, I'll have two nylon chutes!