saucer stability

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Well-Known Member
Jan 27, 2003
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I'm working on a saucer design similar to the kind made by
Art Applewhite Rockets.


Note that these are different than the Estes Snitch. The Snitch has an openning
in the center with fins that provide some stability.

The Delta Flying Saucers get their stability from the cone in a way similar
to funnel rockets, I suppose. In fact, the Delta Flying Saucer looks a lot
like the back end of the Deep Surface Probe kit from Rogue Aerospace (now

My question is this. Can you flatten the the top cone (the leading edge cone)
and still get a stable rocket? Can you fly a flat disk and still get a stable flight?
Would the flat disk be better located at the bottom of the motor or better
at the top of the motor?

Thanks for any insight into this.
There are a couple of spool rocket fellers on TRF and I'm sure they'll share their experiences. I for one have only flown a spool with both top and bottom plates, but it has been reported that you can elliminate the top OR bottom plates and it can be stable. I think CDs were used in each of the cases I heard about.
I my self have built a mini spool rocket and before I comenced construction I was warned that it might not fly that high. It gets about a 100' on an A10-3T. See thread:

I would suggest that you have suffient drag area and you should be fine. I must ask more info inorder to help you better. What size engines? More detail of construction. Lenght, width, Height? So give some more info and I'll be glad to help.
Well, yes, I guess what I'm thinking of is a half spool.
Here's what I had in mind:
1. A 24mm tube just long enough to hold the motor and a thrust ring (ca. 4 inches).
2. A flat disk about 6" in diameter mount on the bottom.
3. A D12-0 motor.
4. I might stick some Snitch-like legs on the top.

I don't expect it to fly very high. Altitude is not the goal here.
However, is this stable enough for it to fly straight up?
I don't want it to leave the rod and start thrashing around.
That should be fine. I also re-read that post and someone I guess was going to attempt a single disc spool roc. I don't remember the name, but if you look throught it and find him you should ask how it went.
Heck on my mini the disc is only 1.75" and it stays stable enough and mini A's. So if you're going to put a 24mm w/ 6" disc that should be more than enough. I personally made it so the disc diameter was the same as the length of the body tube. In your case I wouldn't go any smaller than a 2.75" disc.
I might add that there isn't a concrete rule and you also mentioned that attitude isn't an issue, but I'm a minimalist. Actually I think the guy at was doing spool testing; single and dual disc. But you'd probably have to get the software in order to get that info.
So I hope I've helped and you MUST POST PIX of this wonderful contraption.


Spools Rule!!!!

Yes you can only have one disk and it doesn't matter what end either.

I have a 7.5 inch LOC blukhead with a 2 inch piece of 29mm tube glued to the bottom of it. It has flown on motors from C11s to G35s. It flights its way strait up and tumbles down.

I also have a scratch built rocket with 3 inch LOC tube and a 14 inch disk on the bottom, flies great on almost any H motor.

Both of these rockets are unstable after burnout and do a few flips, etc but it has never been a problem anyway.

Go for it, they are great backyard fliers:)
btw, my avitar is the 3 inch one with a 14 inch disk on an H128
Your design will fly stable, since the CG will be way ahead of the CP. The CP is actually located behind the rocket! John Cipolla of AeroRocket has done wind tunnel testing and published a report confirming this, for details visit:

Be carerful to mount the motor perpendicular to the plate or the rocket will spin more and reach a lower altitude.

Bruce S. Levison, NAR #69055, Section #535 Tri City Sky Busters
Did you get my other post? In the other thread? I got some slightly new data.
thanks for posting that Teflon ! ... I'm really into reading that geek stuff lately
Single disc spools (I still have yet to come up with a better name for them... :rolleyes: ) while more simple to build, also fly higher** than a similarly sized 2-disc counterpart and require a launch lug to ensure a safe flight path. And call me a spool purist (imagine such a thing! hahaha) but the single disc spools recovery like a wounded duck. I prefer the rapid end-over-end tumbling of a traditional (2-disc) spool design :)

** - while hardly scientific, my best guess is ~25% higher based on about 50 spool launches.


Originally posted by lalligood
And call me a spool purist...

That's so true! Especially the part that goes: "First you're gonna build a 13mm spool rocket, and now you're gonna paint it!!!"
I don't know if you remember that but it was all in good fun. BTW I paraphased that if you didn't notice.
Seriously though, us spool guys need to get together and come up with a name for those abominations (Single Disc Spools). Though I am not purist, it still erks me to call something a spool that is not. Nuff said.

Spool Duel !!

Thanks for the info everyone. Looks like a single spool with the disk at
the bottom should be stable enough. I will definitely post pictures
here when I'm ready. I'm not scheduled to launch this until
October. I won't be able to post a picture of it until then.