I built a 3" Darkstar for my L2. I've flown it 3 times and all four times it's shown the same behaviour. It has a very pronounced 'wiggle' for the first 1000ft or so of flight and then it straightens out and flies perfectly. I've flown it on an Aerotech I500T, Aerotech J450DM, and a Loki K527. It's 10.1 pounds without a motor. The slowest it sims off the rail is on the J450DM at 45.5 ft/s, the I500 and K527 both sim at 58 ft/s. The wind varied on the flights, but it was not what I would consider excessive on any of them.

Here is a screenshot of OR. Stability is 6.15 cal with the I500 in it. Stability is 4.41 cal with the K527.

When I launched it at NYPower in May, I talked with another guy who had built a 3" Darkstar. He told me that he'd had the same wiggle on his and cured it by chopping about a foot off the overall length of the rocket and putting a lighter nosecone on it.

I ran simulations in OR to compare stability on the rocket flying on the J450 at it's normal 88" length and again with 12" removed. It shows the rocket is less stable with the 12" removed. Here are the two graphs :

Full

Cut

I'll attach the OR file as well.

Can someone help me understand why this is happening and if chopping 12" off the rocket will help or hinder this problem?

cheers - mark

Here is a screenshot of OR. Stability is 6.15 cal with the I500 in it. Stability is 4.41 cal with the K527.

When I launched it at NYPower in May, I talked with another guy who had built a 3" Darkstar. He told me that he'd had the same wiggle on his and cured it by chopping about a foot off the overall length of the rocket and putting a lighter nosecone on it.

I ran simulations in OR to compare stability on the rocket flying on the J450 at it's normal 88" length and again with 12" removed. It shows the rocket is less stable with the 12" removed. Here are the two graphs :

Full

Cut

I'll attach the OR file as well.

Can someone help me understand why this is happening and if chopping 12" off the rocket will help or hinder this problem?

cheers - mark