From OpenRocket to a Christmas present

[CalebJ]

A few weeks ago I mentioned in passing to my son that there was a computer program for designing and simulating rockets. He pestered me for more information over the next few days until I had a chance to show him OpenRocket. While I was on a phone call shortly afterward, he took the basic 4FNC model I'd created for him and added a second stage and various other bits I hadn't had time to show him. Then he wanted to know about booster pods, so we downloaded the latest beta version (which us down the road of filing a couple of bug reports that were quickly handled).

Long story short, he and I worked together over the next few hours to get to this:


I'd love to build something like that, but needed to clean it up so it actually worked as a real kit that could be assembled. Plus it needed some simplification before things got completely out of hand...

Here's the current incarnation:


I just finished ordering all the parts at eRockets. Hopefully they'll be able to get it all out the door in time for Christmas. If anybody is exceptionally bored, feel free to pull up the Open Rocket file or the bill of materials I threw together in Excel to see if anything obvious is missing.

If you have any interesting name ideas that would be great too. I might toss in an order at Stickershock for some decals.

 

[SecondRow]

Cool present. Your son should get to name it, though.

 

[Tractionengines]

Cool. I like the original version.... larger body tube at payload bay is fun.

 

[CalebJ]

Cool. I like the original version.... larger body tube at payload bay is fun.

Me too. It had just gotten bigger than i had time to deal with figuring out the pieces for by the time you include transitions and boat tails, another body tube diameter, etc. That version would have been something like five feet tall.

This one is still something like 42". About as big as he is. And the erocket order was close to $100 with shipping

 

[neil_w]

Me too. It had just gotten bigger than i had time to deal with figuring out the pieces for by the time you include transitions and boat tails, another body tube diameter, etc. That version would have been something like five feet tall.

This one is still something like 42". About as big as he is. And the erocket order was close to $100 with shipping

I love erockets but for an order like this BMS is really most ideally suited. Pretty sure it would have come out cheaper, although I could say by how much.

 

[CalebJ]

I'll have to compare next time. Once the process was started with the first place that came to mind, it developed some inertia quickly. Thanks for the suggestion.

 

[CalebJ]

Looks like the parts should be here tomorrow. With a little luck I'll have some time next week to cut the fin slots and cut out the fins themselves before packaging it up for Christmas. Also need to pick out motors for first flight launches and get a good battery for my PS2 controller to handle the 3 engine cluster launches.

 

[CalebJ]

Question regarding the side boosters and ring fins - What's the most appropriate way to attach those to the larger body tube they're parallel to? I'm assuming a single glue joint along the narrow point of contact isn't necessarily adequate. If not, would a strip of balsa sanded to match the curve of each tube and sandwiched between the tubes be appropriate?

 

[neil_w]

Question regarding the side boosters and ring fins - What's the most appropriate way to attach those to the larger body tube they're parallel to? I'm assuming a single glue joint along the narrow point of contact isn't necessarily adequate. If not, would a strip of balsa sanded to match the curve of each tube and sandwiched between the tubes be appropriate?

Just glue and fillet, nothing more special needed.

Filleting a BT-BT joint take a bit of care if using wood glue since you will get bubbles, especially with a runny wood glue. But it’s ok for the first fillet layer, and you want something liquidy so it’ll get into the joint. Finish off with something like TB Quick and it’ll look good and be strong.

 

[CalebJ]

Excellent - that keeps things simple.

 

[BABAR]

Question regarding the side boosters and ring fins - What's the most appropriate way to attach those to the larger body tube they're parallel to? I'm assuming a single glue joint along the narrow point of contact isn't necessarily adequate. If not, would a strip of balsa sanded to match the curve of each tube and sandwiched between the tubes be appropriate?

A trick I use for tube fins and pods (when placed individually rather than attached pairs and pods when not abutted against a fin):

use an angle or door frame and a pencil to draw lines where you want each to go. *Then draw a line parallel to the lines moved over just a bit (maybe 1/8”, you may have to fudge it a bit.)

use 1/16” balsa to cut a strip 1/16”x1/16”x length of the tube you are attaching. You can make it shorter by 1/4 inch or so on each end. I call this a balsa fillet.

using wood glue, and double glue joint, attach the fillets with one side edged against the line. You may need tape or rubber bands to keep them from curling up.

use double glue joint to attach the tubes/pods butted up against the balsa fillets. The fillets are small enough that they really don’t show on the final product, but they serve two purposes:

1. They help set and maintain alignment of the tubes.

2. they provide a bit more surface area for quicker tack and I believe stronger attachment for the tubes. This is more important if you put MOTORS in the pods, but works for either.

*the fudge factor is because if you put the fillet right ON the line where you want the tube to go, it forces you to move it over a bit when you place it.