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Nose cone weight placement

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blackwing94

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Working on a MAC MPR38. I want a simple motor eject set up and use a JL chute release. I used rocksim to simulate several different motors and if I can adjust the nose cone weight I can compensate for different (as in bigger) motors. So I'm going to cut off the aft end of the plastic nose cone and epoxy a ring in the shoulder to attach a bulkhead. I plan to put an eyebolt in the bulkhead as my recovery harness attachment point. If I use an eye bolt that's 4 or 5 inches long, I can add/subtract washers/bolts to the part of the eye bolt inside the nose cone to adjust the weight as needed.

I read I'll have to add more weight in the shoulder to move the CG forward than if I had added the weight to the nose cone tip. Not a problem.

I could pour shot and epoxy into the nose cone tip or use 2 part foam. But then the weight is not easily adjustable.

I like that the recovery harness will be attached to the heaviest part of the nose cone. Also the nose cone wont come in ballistic if detached.

I'm thinking the nose cone will also free fall... not as ballistic, more draggy, while waiting for the chute release to open.

My question is, does it matter if weight is added to the tip of the nose cone or in the shoulder? Are there other down sides, aerodynamic or otherwise, to adding weight to the shoulder and leaving the tip hollow and light?
 
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tfish

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The further towards the tip of the nose cone you go, the less weight it will take to change the CG. I've used flat round fishing weights. They come in 1 - 6 oz maybe bigger. I drill a hole in the center of them and use the nose cone eye bolt to hold them in place.

Tony
 

Incongruent

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Working on a MAC MPR38. I want a simple motor eject set up and use a JL chute release. I used rocksim to simulate several different motors and if I can adjust the nosecone weight I can compensate for different (as in bigger) motors. So I'm going to cut off the aft end of the plastic nosecone and epoxy a ring in the shoulder to attach a bulkhead. I plan to put an eyebolt in the bulkhead as my recovery harness attachment point. If I use an eye bolt that's 4 or 5 inches long, I can add/subtract washers/bolts to the part of the eye bolt inside the nosecone to adjust the weight as needed.

I read I'll have to add more weight in the shoulder to move the CG forward than if I had added the weight to the nose cone tip. Not a problem.

I could pour shot and epoxy into the nose cone tip or use 2 part foam. But then the weight is not easily adjustable.

I like that the recovery harness will be attached to the heaviest part of the nose cone. Also the nose cone wont come in ballistic if detached.

I'm thinking the nose cone will also free fall... not as ballistic, more draggy, while waiting for the chute release to open.

My question is, does it matter if weight is added to the tip of the nose cone or in the shoulder? Is there a down side, aerodynamic or otherwise, to adding weight to the shoulder and leaving the tip hollow and light?
Mindsim says that forward nose weight affects CG more than less forward nose weight.

How about if you add whatever minimum nose weight you will feisibly need to the tip, then adjust per flight with washers?

It sounds like you going to attach the eyebolt so that it's removable. Wouldn't that weaken the attachment point? Unless maybe you epoxy a bolt to the bulkhead or something...
 

blackwing94

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The eyebolt will be bolted, locktight, then epoxied to the bulkhead. The eyebolt will not be removable. Only the extra bolts and washers on the end of the bolt.

I went ahead and put 1 oz of BB's in the tip and 3.5 oz of 2 part foam to fill up 3/4 of the nose cone. So the weight is more evenly distributed through out the nose cone. The shoulder will still weigh a bit more.

I'm on the rebound from finishing my level 2 rocket that was DD with redundant eggtimer altimeters. I want a simple rocket this time. I'm building it around a JL chute release. With the nose cone NOT top heavy, I'm hoping for more of a flat free fall. I also fly a LOC Cyclotron with a chute release. When it free falls, the tub fin end is the heaviest part and it aligns with the wind and it actually falls up wind. Weird.
 

Nytrunner

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You've got a good plan sketched out, and several people do things similarly.

I use an eyebolt through the bulkhead with a coupler nut that holds a threaded rod up into the nose cone.
That allows me to get some fender washers or other "holey" weights pretty dang near the tip of the cone.

I started doing this after my L1 because that was basically a "Big Dumb Rocket". No electronics, nothing removable, just motor deploy and an inaccessible nosecone. It flies great, but its limited to 2 or 3 grain 38's.

Example at the end of my recent Leviathan build
https://www.rocketryforum.com/showt...than-HPR-capable-refit)&p=1657636#post1657636
 
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