CTI Cesaroni Technology

nute said:

So, how about a 3-way canted cluster of mellow? 3 J150s should be enough to lift about a 50 lb rocket plus 6.5s of burn time = fun!

Nate

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In addition to the math issues already pointed out, the problem is not so straightforward.

First, to fit three 15-deg canted 38mm 6GXL motors in a rocket, it needs to be about 10" in diameter, maybe more. Of the 20 or so pounds that the rocket can weigh and still have a reasonable thrust/weight ratio, 6.3 pounds is taken up by the motors themselves. Most of that weight is of course in the extreme aft end of the rocket, and unless you go up to about an 11" body tube a good portion of that must stick below the aft end of the airframe. The fins need to protrude aft of the motors to protect them on landings. Now you have a really intense CG problem, because you have only 13.7 pounds to build a 10+ inch diameter rocket long enough to be stable. And then you've still done it wrong.

The focus of the motor mount needs to be approximately halfway between the CG and the CP. And So you usually need to add a little nose weight to the thing to get it to do that. But with a motor that long you're going to have a fairly forward motor mount focus, so then the CG has to be WAAAAAY forward relative to the likely Cp, especially given base drag considerations for such a fat rocket with motor tubes sticking out of it. So it becomes a real challenge to get the rocket to bee stable under two motors, especially given that you were scraping the lower limits with all three motors lighting.

It ain't gonna happen.

How about Mellows on the side with a tiny Vmax in the middle to get it off the pad?

I like the Mellows just the way they are, yielding a slow liftoff in conjunction with the long slow burn. Just build a rocket around the motor specifications, use the proper length rail, and launch in decent weather conditions.

Titan II said:

I like the Mellows just the way they are, yielding a slow liftoff in conjunction with the long slow burn. Just build a rocket around the motor specifications, use the proper length rail, and launch in decent weather conditions.

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I'm not advocating changing the mellows at all. I'm saying that there's a pretty big gap in thrust between most of the motors and the mellows, and it would be nice to have something in between.

More BP in the 24mm relaod

CarVac said:

How about Mellows on the side with a tiny Vmax in the middle to get it off the pad?

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Can't do that...will over pressurize, due to tiny nozzle throat needed for Mellow. But rumor has it, there may be a Dual-Thrust Mellow, in another form in the works!

I want a 6xl 98- Dual thrust mellow.

wfcook said:

I'm not advocating changing the mellows at all. I'm saying that there's a pretty big gap in thrust between most of the motors and the mellows, and it would be nice to have something in between.

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Can't argue with that. A dual thrust would be a great addition. Just leave the Mellows as is.

blackjack2564 said:

Can't do that...will over pressurize, due to tiny nozzle throat needed for Mellow. But rumor has it, there may be a Dual-Thrust Mellow, in another form in the works!

I want a 6xl 98- Dual thrust mellow.

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That's what I was thinking too. Get it off the pad fast and let it burn for 15 or 20 seconds. Not sure how that would work grain wise, but a great idea. I'm putting the L395 in my Mongoose 75 next launch, but I had to build a 10 ft. tower to get a safe launch speed. Still will need a fairly calm day to pull it off. I love those long burn motors, but you have to build a pretty special light rocket for them.

A dual-thrust mellow would rock my world. That would be an awesome addition and I am kicking myself for not having thought to suggest it

blackjack2564 said:

Can't do that...will over pressurize, due to tiny nozzle throat needed for Mellow. But rumor has it, there may be a Dual-Thrust Mellow, in another form in the works!

I want a 6xl 98- Dual thrust mellow.

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I meant a cluster, as that was the topic at hand. One separate Vmax in the center that burns out shortly above the pad, and then it would be surrounded by Mellow motors for the sustain. Inhibit the smoke grain on the vmax with some grease if you'd like to eliminate the center smoke trail.

CarVac said:

I meant a cluster, as that was the topic at hand. One separate Vmax in the center that burns out shortly above the pad, and then it would be surrounded by Mellow motors for the sustain. Inhibit the smoke grain on the vmax with some grease if you'd like to eliminate the center smoke trail.

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It also tends to be a touch difficult to fit a central motor into a triple canted cluster...

Why does it have to be a canted cluster ? how about putting a 2 degree of rotation on the outboard 38's ? That would impart a nice roll to keep the rocket stable .

Eric

3stoogesrocketry said:

Why does it have to be a canted cluster ?

Eric

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Because I like them. Nothing quite like the smoke plume you get from a large Deuce- or Tres-style mount.

wfcook said:

Because I like them. Nothing quite like the smoke plume you get from a large Deuce- or Tres-style mount.

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That's why I eat ribeye steaks and wash them down with wine. :wink:

Wouldn't it be easy if the central motor was shorter?

Ravenex said:

Wouldn't it be easy if the central motor was shorter?

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Sometimes yes, sometimes no. It gets pretty tight in there. And then you're moving the CG even further aft in an already delicate balance. Believe me, I've looked at it.

I don't want to turn this thread upside down based on my particular rocketry bent, though. Suffice it to say that I'd like something in a single motor that has more initial kick than a mellow but a longer burn than most CTI propellants. Something in between or dual-thrust.

Flew my High Tech H45 to 4257' on an I55 Mellow Saturday.Beautiful flight.
I also like big canted clusters, particularly the Deuce. My 54 mm Deuce would fly on 2 J150's on a calm day (off a 3/4" 10 ft rod).

Here is an updated list of CTI offerings, sorted by imp. class & avg. thrust, imp. class & tot. impulse, burn time & imp. class, propellant type, and case:

If anyone finds mistakes, omissions, etc. then please let me know.

Greg

View attachment CTI Cert Motor - 2015-04-24 - By Imp Cls and Total Imp.pdf

View attachment CTI Cert Motor - 2015-04-24 - By Prop Type.pdf

View attachment CTI Cert Motor - 2015-04-24 - By Burn Time and Imp Cls.pdf

View attachment CTI Cert Motor - 2015-04-24 - By Case.pdf

View attachment CTI Cert Motor - 2015-04-24 - By Imp Cls and Avg Thrust.pdf

Area66 said:

More BP in the 24mm relaod

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Very simple to add your own.

GregGleason said:

Here is an updated list of CTI offerings, sorted by imp. class & avg. thrust, imp. class & tot. impulse, burn time & imp. class, propellant type, and case:

If anyone finds mistakes, omissions, etc. then please let me know.

Greg

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Thanks Greg, I use your charts for almost all of my launches. Adding in the Mellow long burns makes it easier for me.

jimzcatz said:

Very simple to add your own.

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Can one just tape some extra onto the top of the cap?

Nate

Wayco said:

Thanks Greg, I use your charts for almost all of my launches. Adding in the Mellow long burns makes it easier for me.

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You're welcome Wayco. I had forgotten about the list and assumed no one was looking at the data.

Greg

GregGleason said:

You're welcome Wayco. I had forgotten about the list and assumed no one was looking at the data.

Greg

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Is it possible to get this info in an Excel Workbook?

GregGleason said:

You're welcome Wayco. I had forgotten about the list and assumed no one was looking at the data.

Greg

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Awesome chart GregGleason! I hadn't seen this before and it's great to have all the data in one place, and the format is perfect. Just to let you know, it does look like the new F51 and F70 are labeled as E's on the impulse sorted chart.

GregGleason said:

If anyone finds mistakes, omissions, etc. then please let me know.

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The by-case sort seems off to me? I was hoping, for example, to see all Pro54 4g grouped together in that file.

Second the motion for sharing the underlying spreadsheet if you're willing to, it's something I'd be pleased to keep on the notebook I take along to launch sites... But in any case, thanks! This is a much easier form for perusal than trolling the CTI website which is what I usually do.

SCrocketfan said:

Awesome chart GregGleason! I hadn't seen this before and it's great to have all the data in one place, and the format is perfect. Just to let you know, it does look like the new F51 and F70 are labeled as E's on the impulse sorted chart.

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Thanks for finding that. In the process, I found two more that were in error. Here are the ones with the incorrect impulse:

50F51-13A
53F70-14A
143G33-9A
4937L395-P

I'll fix them and post new prints, but probably won't be able to get to it until next week.

Greg

bdale said:

The by-case sort seems off to me? I was hoping, for example, to see all Pro54 4g grouped together in that file...

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You are correct bdale. The case grouping is off. I didn't have the sort sequence properly set for that one. I write the sort sequence down in the future.

BLKKROW said:

Is it possible to get this info in an Excel Workbook?

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bdale said:

... Second the motion for sharing the underlying spreadsheet if you're willing to, it's something I'd be pleased to keep on the notebook I take along to launch sites... But in any case, thanks! This is a much easier form for perusal than trolling the CTI website which is what I usually do.

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The spreadsheet has embedded links to a master spreadsheet, so it would be a pain to split that all out so that there aren't errors. If folks were interested, I could output a plain-jane, tab-delimited ASCII file and post that on TRF. That you could bring into Excel and make your own data how you would like it.

Greg

Paging Jeroen_at_CTI:

Are any of the following new CTI motors case bonded?



Greg

GregGleason said:

You are correct bdale. The case grouping is off. I didn't have the sort sequence properly set for that one. I write the sort sequence down in the future.


The spreadsheet has embedded links to a master spreadsheet, so it would be a pain to split that all out so that there aren't errors. If folks were interested, I could output a plain-jane, tab-delimited ASCII file and post that on TRF. That you could bring into Excel and make your own data how you would like it.

Greg

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Hi Greg,

I was able to convert the PDF to Excel by making a quick conversion in Word first. I didn't post it in response because the data set is yours, not mine.
I can post it here if you are OK with that. I did send it to one member here already.
The colours and everything are still intact. The links are gone.

Len B said:

Hi Greg,

I was able to convert the PDF to Excel by making a quick conversion in Word first. I didn't post it in response because the data set is yours, not mine.
I can post it here if you are OK with that. I did send it to one member here already.
The colours and everything are still intact. The links are gone.

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Len B, that's fine and I think that's very helpful.

You might want to wait to see if anyone finds anymore issues.

Most of the numerical data comes from a copy/paste routine that comes from the Cesaroni website. Actually the process is pretty involved to retrieve and place the data, but since it wasn't keyed in manually (except on rare occasions) there should be a high confidence level that the numerical data is correct.

Greg