First Oddroc - Pyramid

I know this is mellow by Oddroc standards, but it is my first and I want to be able to answer RSO questions with more than 'Uhhhhhhh?'

It is a simple pyramid, 8" x 8" base x 9" tall that is used to 'request' that shippers don't stack stuff on top of pallets (pic attached). Weight of the piece (just cardboard, not rocket) is 85grams.

I'm pretty sure I (or just about anyone) could make this structurally flyable, but I want to make sure that it is a smart and stable design.

I plan on gluing the cardboard together and adding a wood base (thin ply or balsa). I will use a BT-80 as the motor mount carrier, which gives me options for a 29mm single or 3x 18 or 24mm cluster easily including recovery area.

Questions:

Are there general rules for simulating pyramids in Openrocket? If I had to guess at what to do, I'd use a 6"OD x 9" long nosecone with motor, but that could be left field as I am not an Openrocket expert.

Is there a good way to simulate it in wRASP? CD 3, dia 6" maybe?? Just a guess.

Does a 3X 18mm (C6-3) cluster seem logical? I like the idea of running the launch lug through the middle, which is easy with a 3X cluster. I'd prefer to stay away from 24mm due to cost alone. I'm OK, with 1X 29mm, but already have a 29mm saucer type of rocket. . .

I figure I'm good to fabricate the rocket sans motor mount, so I'm going to go do that now, but any help you guys could provide by tomorrow night will help me finish it out to fly this weekend.

Thanks,

Sandy.

That is too funny, I just brought one of those home from work too! I like your interchangeable motor mount idea, I think I will incorporate that as well.

I am fairly certain that none of the amateur rocketry simulation software will be able to determine stability on "saucer" type rockets. While I make extensive use of OpenRocket for my traditional designs, all of my saucers are done by seat-of-the-pants experimentation. I started by copying proven designs and then gradually started altering various parameters. I have made several dozen now and I have yet to have one that didn't fly. Keep everything small (start with a single 18mm motor) and lightweight and you should be ok.

For pyramids, so long as you keep the motor as far forward as possible you should be ok. Pyramids, unlike most other saucers, *do* need a recovery system. Typically just ejecting a motor pod attached with a cord is enough to keep the rocket from coming in pointy end first. It is simple enough to do some testing by tossing it off a several story building with a spent motor casing to see what happens.

Oh... One other thing...

When working with corrugated cardboard, I find expanding urethane glue ("Gorilla Glue" ) to work quite well. It will allow you to make secure joints to the "end-grain" of the cardboard without needing a perfect fit as with PVA glue. Lightly paint the end-grain as well as the contact point, tape or pin the pieces in place, and the foaming action will lock everything together.

Sandy H. said:

Does a 3X 18mm (C6-3) cluster seem logical? I like the idea of running the launch lug through the middle, which is easy with a 3X cluster.

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Looks like a great project. Are you sure you'll have enough thrust with three C6-3's? Sunward's "King Tut" Pyramid flies great on a G40, and I think that yours might end up slightly heavier. (The one "No Stack" pyramid I have seen fly was glassed, so it was quite a bit heavier.)

SMR said:

Looks like a great project. Are you sure you'll have enough thrust with three C6-3's? Sunward's "King Tut" Pyramid flies great on a G40, and I think that yours might end up slightly heavier. (The one "No Stack" pyramid I have seen fly was glassed, so it was quite a bit heavier.)

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Hmmm. If the pics in your attachment are any indication, I should do something different!

One of our club members flies pyramids all the time and some of them are pretty large. I was inferring from the flights I've seen him do that a cluster of C6's might be OK, but I tried simulating it in open rocket as a conical nosecone with the cluster mount and flights were just 40-80 feet depending on the specifics. Doesn't really sound like what I'm looking for. . .

A have an Art Applewhite Stealth that flies great on G's, but it is low and slow, so maybe I should reconsider the C cluster.

Thanks for the comments, as it has made me re-think the best course of action. Safe flight is #1 priority.

Sandy.

Sandy H. said:

I know this is mellow by Oddroc standards, but it is my first and I want to be able to answer RSO questions with more than 'Uhhhhhhh?'

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but wait, isn't that the whole point of oddrocs?

u gotta remember though that any of the all nose cone type rockets will fly very low and come in with a technically ballistic recovery, so you gotta build light but strong, and you should look at art's 18mm pyramid and check out how big that is, then build something similar with 3 mmts.