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- Aug 18, 2011
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So I have been stumped lately, I am trying to determine if my Blackhawk 38 is stable or not.
Here are the steps I followed, I loaded everything up with laundry/av-sled/Kevlar cords. I weighed the bird and got a mass of 983.8 grams.
So with everything still inside, I went out to the garage to figure out the CG. So I had it hanging from the roof with a shock cord, and got a CG of 78.6cm from the tip of the nose cone.
I input all this information into Open Rocket then selected the CTI H143 motor, and am getting a stability margin of 4.42 cal.
Something is not adding up, all the components have been measured and are accurate on the OR file. The only addition I made to the kit is instead of gluing the shock cord to the nose cone/coupler in the lower half, I used two washers and a bolt to sandwich the nosecone coupler, and the same with the other coupler. This does add some weight, but I don't see it adding that much more to make the rocket unstable.
Please help I am trying to get this bird to fly in the beginning of the year for my L1. This is the only thing holding me back.
Could it be this rocket needs a motor that is bigger then 2 grains?
View attachment Blackhawk 38.ork
Here are the steps I followed, I loaded everything up with laundry/av-sled/Kevlar cords. I weighed the bird and got a mass of 983.8 grams.
So with everything still inside, I went out to the garage to figure out the CG. So I had it hanging from the roof with a shock cord, and got a CG of 78.6cm from the tip of the nose cone.
I input all this information into Open Rocket then selected the CTI H143 motor, and am getting a stability margin of 4.42 cal.
Something is not adding up, all the components have been measured and are accurate on the OR file. The only addition I made to the kit is instead of gluing the shock cord to the nose cone/coupler in the lower half, I used two washers and a bolt to sandwich the nosecone coupler, and the same with the other coupler. This does add some weight, but I don't see it adding that much more to make the rocket unstable.
Please help I am trying to get this bird to fly in the beginning of the year for my L1. This is the only thing holding me back.
Could it be this rocket needs a motor that is bigger then 2 grains?
View attachment Blackhawk 38.ork