Adding outboards...

[pr_rocket04]

I'm going to start working on the booster for the two-stage Armageddon, and I was thinking about adding 4 outboards to the 6" bt. Would this be possible without cutting the main tube and having them set in it? Like completely outboard? Because I don't have that much additional room with a 4" central mount. Thanks.

 

[llobdelljr]

Yes, it's possible. I permanently mounted two 2.1" outboard motor tubes to a 4" main body tube in the first stage of a two-stage rocket. It's a little complicated but if you want to know the details, please e-mail me.

 

[pr_rocket04]

Alright I sent you one, thanks.

 

[FredA]

Here is how I put together a new motor section for my 5.5" rocket. It has a central 75mm with two 38mm outboard that are long enough to just fit 38/720 motors (J350/J420R) for airstarting.

Not exactly outboards.....inboard/outboard.

 

[FredA]

Here is the rocket on the pad.
Virgin flight - J415W with two I285R's.

 

[pr_rocket04]

That's exactly what I wanted to do, I didn't know if there was another method possibly to have them completely external. I will probably just end up doing what you did, only my nose cones will be more exposed, shouldn't look too bad. Nice pics too.

One last thing, I've never had to add holes to centering rings. For the half circles on the outsides, how do I get them all perfectly cut out? And I take it you use a hole saw in the proper diameter for the size?

 

[Rocketmaniac]

Originally posted by freda
Not exactly outboards.....inboard/outboard.

Now that is a very cool way to add motors!!!! Someday when I have more time and can get back into building rockets, I might have to try this method out!!!!

 

[FredA]

Talk to Patrick Waite - Mr. Centering Rings.....
His email is: [email protected]

Custom Rings, great workmanship, fast turnaround and a fair price......can't be beat.

I just told Partrick what I wanted - sent him a crude drawing to make sure and they were in my hands within the week.

 

[pr_rocket04]

Wonderful.

 

[pr_rocket04]

Now my latest concern, is there anyway of simulating this design on Rocksim? I'm not too sure if 54mm's can work out, I added some additional weight to the design down low, keeping the same length and all, and it really loses stability, like where I'd have to put a bowling ball on top the nose to make it stable. Hmm. What to do, what to do? Maybe I can make the booster longer than originally planned.

 

[FredA]

Not hard to do....
Here is my Rocsim 6 file.
Enjoy!

 

[FredA]

Woops,
That was an early version - but you get the idea.
FredA

 

[pr_rocket04]

I saw the design, but is it possible to have true outboards simulated? I would like the proper drag to be simulated so I can time my delays as efficient as possible. Could you explain how you go about creating the design with different size outboards? I guess I'm not that experienced with Rocksim yet. Thanks.

 

[pr_rocket04]

Does anyone know about adding various size clusters and outboards on Rocksim? Help me help me!!!! No offense but this forum is slow moving! Oh well, as long as this thing gets done.

Might I add this project has been coming along slow for anyone who has paid attention to what I'm doing. And might I also add that it's going to take even longer now.

Why?

Well the 5 engine booster for my 4" Armageddon is still a go, and you might think I'm crazy now, but the 4" Armageddon is receiving four, yes four, outboard 54mm's. And in case you didn't previosuly know, the rocket already has a 75mm central mount. This will give me more options for the altitudes I'd like to acheive, with or without the booster.

I plan to do a central motor ignition, followed by two seperate pairs of 54mm's. When the booster is done, I can attach it and fly a booster with three ignition stages, leading to sustainer ignition, another three stages! I don't know if anyone has watched six-stage ignition occur, but Gates brothers watch out!

All should work out as long as I don't destroy the sustainer before the booster is complete. Wish me luck.

 

[FredA]

Explore Rocsim.....
Use the cluster wizard to add multiple motors.
Edit the MMT's and change their location if you need to.

It's easy - but YOU need to do it, it's your rocket, your design - look at my rocsim file for hints.

Only issue I've found is that sometimes rocsim gets confused on the motors and you can't load a motor in the last mmt on the list.
I've learned to "load all" the motors to get this problem motor, then go back and change the ones I want.

 

[pr_rocket04]

Thanks, but do you know how you actually add the motors externally on the body tube? Look at this link, they want like $11 to tell you how to do it (scroll down to second picture): https://www.apogeerockets.com/rocksim.asp

If you think of how much Rocksim is, this should be free, it's like having to pay for instructions. I'm sure someone in here knows how. And yes I can definitely create my own Rocksim files, check it out:

 

[FredA]

Add more tubes. Declare them to be MMT's.
Then change their radial position....second tab on the edit screen.
It's easy....the part I have not figured out are the extra nosecones.

 

[pr_rocket04]

Thanks, can't believe I never bothered with radial position. Hopefully someone can figure out how to add nose cones, because my open mmt's equate to dragging a chute up in the simulations.

 

[edwardw]

You can't add nosecones to an outboard body tube/motor mount. But, if you look through Apogee E-zines (free) #108 - #111 they tell you about simulating strap on boosters. I did this for the Delta II project we recently flew. Basically the nosecones will add stability, not detract. From there you will have to fly it a couple times and then adjust your Cd to accommodate to the altitudes you flew. Just remember to keep all other variables in the rocket the same, so that your basically just solving for one (the Cd).

Edward