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zixxerboy
12-31-2007, 09:02 AM
I have just completed building my first two rockets. One is an Este “Hi-Flier” and the second is a scratch built. I have yet to launch them.

I am struggling with the swing test to confirm their stability. The amount of clay jammed into the nose cone to balance them seems excessive. The Este production rocket should be pretty close but looks like it will need a clump of clay about the size of two regular dice.

The Estes Tech Manual I downloaded says to install an engine before testing – but somewhere else I thought I had read that a spent motor casing should be used. That would cut down of the ballast I need.

Also I will launch from a stand I built using 3/32” welding rod for the guide rail. How long should it be?

Thanks in avance for your help.

Thruster
12-31-2007, 09:18 AM
Check this site out.
http://www.rockets4schools.org/education/Basic_Rocket_Stability.pdf

rocketguy101
12-31-2007, 10:17 AM
The Estes Tech Manual I downloaded says to install an engine before testing – but somewhere else I thought I had read that a spent motor casing should be used. That would cut down of the ballast I need.

The motor should be fully loaded. Think about it: when do you want your model to be stable, at launch or at burnout?

Also your rocket should be "flight ready" i.e.: parachute installed, wadding, etc.

dwmzmm
12-31-2007, 03:45 PM
The Hi-Flyer is well known for going unstable on the larger motors; I got my son one and
plan to add to the length of the bodytube to correct this issue.

zixxerboy
12-31-2007, 09:51 PM
DW
Thanks.

You say these are unstable with a larger motor. I think it will use a "B". Is that considered large?

dwmzmm
12-31-2007, 09:55 PM
DW
Thanks.

You say these are unstable with a larger motor. I think it will use a "B". Is that considered large?

Not sure; the ones I've seen launched were on C6-7's and the model went unstable as soon
as it left the launch rod. If nothing else, you can add some noseweight to be on the safe side.

CPMcGraw
12-31-2007, 11:26 PM
DW
Thanks.

You say these are unstable with a larger motor. I think it will use a "B". Is that considered large?

I had to go back and search some of the other threads on this one. The Hi-Flier is horribly unstable with a C6-7 -- it has a negative margin -- minus 0.35 -- meaning the CG is behind the CP by about 1/3 of a body tube diameter. Using the B6, I think the margin was still marginally unstable at about 0.86.

Take some modeling clay and shove it to the tip of the nose cone. About 3/16th to 1/4th of an ounce should be sufficient. The model will now balance in the correct range with "B" and "C" power. In all truth, an A8-5 will shoot this model well into the sky to the point you might lose track of it, being as small as it is. Use a streamer for recovery -- 1.5" wide by 15" long should be enough.

James Pierson
12-31-2007, 11:59 PM
rocketguy101 Quote:
The motor should be fully loaded. Think about it: when do you want your model to be stable, at launch or at burnout?

Also your rocket should be "flight ready" i.e.: parachute installed, wadding, etc.

I agree and also add that the rocket to be fully loaded and with the largest motor you intent to fly in that particular design or largest specified by the manufacturer for swing testing.

Good luck, JP.

James Pierson
NAR# 77907

Tom Swift
01-01-2008, 08:42 AM
Another option besides adding weight to the nose or extending the body tube is to use mini motors.

I haven't started my HiFlier yet but plan to build it with a 13mm motor mount from the beginning.