mperegrinefalcon
Well-Known Member
- Joined
- Jun 12, 2017
- Messages
- 360
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- 75
Initially I built the nosecone bulkplate with a single threaded rod and an offset eyebolt with a small fillet on the edge.
While this works on smaller rockets, I do not think it is very good idea for this heavy of a nosecone. I do not think the thread is a problem, I just think the lever from the eyebolt to the center might break the fiberglass. I tested the weight and balance and found I needed a good amount of nose weight anyway, so I decided that instead of doing the traditional thing of epoxying lead in the tip of the nosecone I would re-do the bulkplate using 2 rods and have a central eyebolt. I realized it was too late to remove the other bulkplate with the tools I have, so instead I cut down the center threaded rod, used a few washers as spacers and epoxied a bulklplate with 2 rods attached behind the other bulkplate. I used 5 minute epoxy around all the nuts to prevent them from coming undone and I tightened down a washer and a nut on the the central rod as well. After that cured I put a fillet around the edge. This added about 120 grams of nose weight, but with my tests I needed about 400 grams total. I filled up the threaded rods with washers, and that was about 200 grams more, so not quite enough. I drilled a hole through both bulkplates and now I epoxied lead in the tip of the nosecone. I used about 130 grams of lead and 70 grams of 5 minute epoxy in the nosecone tip. Using the threaded rods in the NC I added the rest of the nose weight with washers, so I can adjust it as needed.
I realized this rocket was going to be heavier than initially predicted, so I purchased a Fruity Chute Iris Ultra 84. The expected mass on recovery is 27.5 lbs, and this parachute is predicting 16.78 FPS. The altitude of the launch site in Colorado is about 5400 feet though and in my experience I need to add about 15% to that, which brings it to 19.30 FPS.
With the added nose weight I am getting a stability margin of 1.15, which I am happy with. I would rather it be a little heaver and have a bit more of a stability margin.
While this works on smaller rockets, I do not think it is very good idea for this heavy of a nosecone. I do not think the thread is a problem, I just think the lever from the eyebolt to the center might break the fiberglass. I tested the weight and balance and found I needed a good amount of nose weight anyway, so I decided that instead of doing the traditional thing of epoxying lead in the tip of the nosecone I would re-do the bulkplate using 2 rods and have a central eyebolt. I realized it was too late to remove the other bulkplate with the tools I have, so instead I cut down the center threaded rod, used a few washers as spacers and epoxied a bulklplate with 2 rods attached behind the other bulkplate. I used 5 minute epoxy around all the nuts to prevent them from coming undone and I tightened down a washer and a nut on the the central rod as well. After that cured I put a fillet around the edge. This added about 120 grams of nose weight, but with my tests I needed about 400 grams total. I filled up the threaded rods with washers, and that was about 200 grams more, so not quite enough. I drilled a hole through both bulkplates and now I epoxied lead in the tip of the nosecone. I used about 130 grams of lead and 70 grams of 5 minute epoxy in the nosecone tip. Using the threaded rods in the NC I added the rest of the nose weight with washers, so I can adjust it as needed.
I realized this rocket was going to be heavier than initially predicted, so I purchased a Fruity Chute Iris Ultra 84. The expected mass on recovery is 27.5 lbs, and this parachute is predicting 16.78 FPS. The altitude of the launch site in Colorado is about 5400 feet though and in my experience I need to add about 15% to that, which brings it to 19.30 FPS.
With the added nose weight I am getting a stability margin of 1.15, which I am happy with. I would rather it be a little heaver and have a bit more of a stability margin.
