75mm sub min balls project.

[Model_rockets]

This is a build thread for a balls project that will hopefully be launched at this years balls. So the quick overview of the project is that I am building a 75mm sub min rocket that will hopefully go to about 35k ft. the motor is going to be a ex 76-6000 motor. the airframe is going to be made out of soller sleeve and the fin can tube is carbon with 3/16 g10 fins with carbon tip to tip with proline fillets. I will be using a telemini,straloggerand some gps tracker for the electronics. and two cable cutters for deployment. so far the fin can tube has been made and the fins cut and beveled. and right now I am working and on a custom metal coupler and av bay design.

 

[Hobie1dog]

When is BALLS this year?

 

[Model_rockets]

When is BALLS this year?

sep 22-24

 

[Model_rockets]

Fins have been tacked on.

 

[gloy]

I guess I'm not very smart, what is sub minimum diameter? What diameter is this project.

 

[StreuB1]

I guess I'm not very smart, what is sub minimum diameter? What diameter is this project.

Sub-min = airframe diameter = motor diameter

Basically, no airframe.

 

[gloy]

Thanks, but wouldn't the fin can over the motor now make it min. Diameter. Splitting hairs here maybe but just curious. Sub min. Would require the fins directly to motor.

 

[StreuB1]

Thanks, but wouldn't the fin can over the motor now make it min. Diameter. Splitting hairs here maybe but just curious. Sub min. Would require the fins directly to motor.

Generally that is correct, though at some point it is no longer worth arguing about. Its all about flying, after all. There are no prizes for min-dia vs sub-min etc. Its braggin rights at that point.

 

[bobbyg23]

Thanks, but wouldn't the fin can over the motor now make it min. Diameter. Splitting hairs here maybe but just curious. Sub min. Would require the fins directly to motor.

This is correct. This project is just a minimum diameter project. Still pretty darn cool.

 

[gloy]

Yes it is , I'll be watching. 30k feet sounds awsome.

 

[Neutronium95]

IMHO, the distinction between submin and minimum diameter is actually kind of important. With a normal minimum diameter rocket, you can do things in a relatively standard way, with the motor in a body tube. With a submin, you are forced to anchor everything to the top of the motor. The need for a fin can is mostly just going to depend on the motor material. With a fiberglass casing, it's relatively simple to bond fins directly to the motor, while an Aluminum case will most likely require a fin can, unless you braze some metal fins onto it.

 

[Model_rockets]

This is correct. This project is just a minimum diameter project. Still pretty darn cool.

Hard disagree. I mean the whole airframe is the same diameter as the motor and like others have mention this comes with a host of challenges. It is the same build process and design as a flying case and basically is one.

 

[Model_rockets]

First set of fillets is curing

 

[Model_rockets]

Project update.
just got the carbon for the tip to tip but still waiting on epoxy
but the custom forward bulkhead design is done and will be sent off to be machined soon.