On nose cones, epoxy and CG weight . . .

[markfsanderson]

Greetings,
A couple of questions on my 2.6" Madcow DX-3 build:

1) According to one reviewer, keeping the nosecone attached during ejection is problematic. He stated he taped up the shoulder and etc. How do I keep this from happening? 3 3/32" screws 120 degrees apart in drilled holes shored up by CA? Plastic rivets, I've read of folks using them but I've found no link to these rivets. Does anyone know a source? Any other ideas?

2) According to the DX-3 instructions, Epoxy will not stick to the front inside of the nosecone reliably for the purposes of adding nosecone weight(BB's and Epoxy). They suggest that before painting that a screw be driven into the nose cone and the head removed to prevent slippage. I've already painted my nosecone (oops) and don't want to do that. I'm assuming that I'll need some to ensure a proper CG with the engines/cases that I'll be flying (29mm 40/120 with G rated motors will be the heaviest(?)/most powerful). I was thinking of using the expanding foam insulation after the epoxy set to prevent the sudden shift of the nosecone weight mass. Has anyone done this? Any other ideas that don't involve drilling holes? I will if I must . . .

3) I have some micro balloons in a bag that I can use as fin filet material to mix with the 30 minute epoxy that I'm using. Are there any downsides to utilizing this material as fin filets? This rocket will not be flown with anything more than G motors in a 29mm 40/120 AT tube.


Thanks for your time and patience . . .

Mark F. Sanderson

 

[Steve Shannon]

Public missiles and many other places sell the removable plastic rivets:
https://publicmissiles.com/product/hardware

If you’re going to add foam to your nosecone after epoxying in the weight, consider just using foam and no epoxy.
Also, consider using something other than lead, please. Sand, water, or even tungsten shot are all better for the environment if you crash that nosecone into the ground.
The downside to using micro balloons is that they weaken the fillets. If that’s no problem, then don’t worry about it. They are easier to finish.

 

[markfsanderson]

Public missiles and many other places sell the removable plastic rivets:
https://publicmissiles.com/product/hardware

If you’re going to add foam to your nosecone after epoxying in the weight, consider just using foam and no epoxy.
Also, consider using something other than lead, please. Sand, water, or even tungsten shot are all better for the environment if you crash that nosecone into the ground.
The downside to using micro balloons is that they weaken the fillets. If that’s no problem, then don’t worry about it. They are easier to finish.

Steve,
Thanks for the info . . . I'll using copper BB's . . . no lead. I'll be purchasing some of those rivets . . .

Mark Sanderson

 

[ericm541]

What is a good alternative to lead if you need a lot of weight, like 10 lbs or more?

 

[markfsanderson]

What is a good alternative to lead if you need a lot of weight, like 10 lbs or more?

Maybe Bismuth?

Mark

 

[Nytrunner]

Something I like to do is put a centering ring and bulkhead inside the nose past the shoulder (John Coker method, LOC adjustable system, etc...). This gives me easy access to change weights for different motors and keep the rocket flyable on a greater range of motors.

Another source for removable rivets is McMaster Carr, or even ordering from Walmart. I got a pack of a couple different sizes and don't foresee needing to reorder for a very long time

 

[markfsanderson]

Something I like to do is put a centering ring and bulkhead inside the nose past the shoulder (John Coker method, LOC adjustable system, etc...). This gives me easy access to change weights for different motors and keep the rocket flyable on a greater range of motors.

Another source for removable rivets is McMaster Carr, or even ordering from Walmart. I got a pack of a couple different sizes and don't foresee needing to reorder for a very long time

Where do I find out details on the 'John Coker method'? Walmart!? Do you have a link or search term? I'll try plastic rivets and see what turns up . .

Thanks!

mark

 

[Nytrunner]

Coker video



Here's some for a couple different panel thicknesses (not available in stores annoyingly)

https://www.walmart.com/ip/100-x-Removable-Head-Nylon-Push-Rivet-Fasteners-for-5-5-6-5mm-Thick-Panel/128578152
https://www.walmart.com/ip/100-x-Removable-Head-Nylon-Push-Rivet-Fasteners-for-3-5-4-5mm-Thick-Panel/154997558

From McMaster

https://www.mcmaster.com/push-rivets

 

[markfsanderson]

Coker video



Here's some for a couple different panel thicknesses (not available in stores annoyingly)

https://www.walmart.com/ip/100-x-Removable-Head-Nylon-Push-Rivet-Fasteners-for-5-5-6-5mm-Thick-Panel/128578152
https://www.walmart.com/ip/100-x-Removable-Head-Nylon-Push-Rivet-Fasteners-for-3-5-4-5mm-Thick-Panel/154997558

From McMaster

https://www.mcmaster.com/push-rivets

Thanks! Just dropped $10.00 on the shorter rivet set . . . Watching the video next!

Mark

 

[David Schwantz]

Here are a couple pics of what I like to do. Take NC and draw a circle using the shoulder as a pattern. that is about the right size that will fit inside NC but will lodge against shoulder and not pull out. Glue in place, do NOT use CA, it will eat the plastic. Use some form of epoxy or a foam tac glue.Remember to prep before glue. I use telescoping cardboard airframe tubes for the mount inside, one takes the weight, the other takes the eye bolt.

 

[grouch]

What is a good alternative to lead if you need a lot of weight, like 10 lbs or more?

Longer body tube.