Caffeine Monster Build Thread

[Lowpuller]

So I suspect you may be asking, What is a Caffeine Monster?

Well you start with a Fliskits Decaffeinator like this:



Or with a glider like this:



You modify it to become a Humongous like this:



Then you modify it to 29mm motors and add this:



To end up with hopefully something like this:



That I like to call a Caffeine Monster!!



more to follow......




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[Lowpuller]

Ok everything, well almost everything, gathered up...



First step, build what I like to call the pods.



Then more pods



Then more pods



Then even more pods



Until you have something like this




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[rstaff3]

Here's a high power one at MDRA. I forgot how the flight went.



There is a video here https://www.mdra-archive.org/photos/RedGlare6/PeterAbresch/ No indication about the motor, could have been a G.

 

[burkefj]

Big foam rockets and gliders, cant go wrong...

 

[Lowpuller]

Next, time to build what I call the sticks, I'm only started on these!



I have also been doing lots of guestimation trying to determine a final weight. I've weighed everything except the HMG (hot melt glue) which turns out to be a major weight component.

My best guess after weighing all components and adding some for glue is around 50oz. to 55oz.

Looks like I'll be using an AT G76 which is Mojave Green, I was hoping I could fly it on a Black Jack motor but it does not appear to be in the cards.

My Decaf flys great on an Estes D12 or an AT E-11 Black Jack, but failed under load on an E18 White Lighting, to much thrust, to fast.

I want to come off the rod as slow as possible with minimum Gs so G76 is not my preference but comes as close as I can find based on Thrust Curve and the Lazy RSO Guide.

Don't be fooled into thinking this is a cheap project, while the cups are cheap, once you add the glue, and it takes a lot of glue, this will be a costly and likely one flight project.

The cups are also very fragile and transportation is extremely difficult even with a simple Decaffeinator. I plan to borrow another Jim Flis idea and have sections of the rocket that will be taped together on site. The overall length of the rocket is pushing 15'




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[neil_w]

op:

 

[burkefj]

You may consider foam tac or the equivalent from bob smith, it's a foam safe contact cement, much lighter than hot glue, dries clear but not stiff. You can apply to one side and then you can move things around till correct and just let set, or apply to one side, or both, puth them together and then separate for 10-30 seconds then re-attach for an instant bond.

Frank

 

[Nytrunner]

Have you checked out the G53 FastJack by Aerotech for the 29/40-120 case (assuming you have said case)?

It's got a decent initial thrust that will get you 5:1 at 55 oz.

That being said, your foam monster will be way more draggy than the average 29mm rocket.


Edit: 15 feet? That's prtty ambitious, but awesome if it works! (Will probably be awesome if it doesn't work either lol)

 

[Lowpuller]

Nytrunner, thanks for the suggestion but according to Thrust Curve a G53 won't get me there, to slow off the rail.

I building this for a rail and assuming a six footer.

And talk about draggy, the glider is gonna likely be the killer.

When I launched my Decaf with a glider on an E18, it shredded the glider and ripped the connection point from the rocket as soon as it left the rail.



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[Lowpuller]

Rstaff3

Thank you those were very helpful.


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[burkefj]

Try the G75 which is a short version of the H97 that might do it for you, you also might need to splice together a rail to get more rail length to support it properly for a longer amount of time, that's what I needed to do, also consider how your rail buttons will mount and have strength, are you using a stuffer tube? Where is your chute going and how is the ejection charge contained?
There are a couple of 29mm cti motors, H53, H54 I think that might suit depending on final weight.

 

[Lowpuller]

Burkejf

Thank you for the info. I plan to launch this one at my local field which is limited to Gs, so that adds another factor.

I am planning to use rear ejection identical to the stock decaf, but with a slightly bigger nylon parachute, and jacked to 29mm.

On my Decaf I glued blocks of balsa to the outside of the cups and attached the buttons to the balsa blocks. In this case I was considering adding some internal reinforcement but frankly it comes down to wall strength on the cups unless I add some type of super structure.

I had considered running the rail through the "center" of the rocket but switched back to the outside.

Again according to Thrust Curve a G57 won't work, too slow off the rail.

Please explain what you mean by stuffer tube?

Thank you for the input


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[burkefj]

On my large foam structure rockets, I use a center 29mm tube that runs the entire length, this adds a structural spine that everything else ties into. Mine do not use rear ejection so I have a 4" parachute compartment cup at the top which helps move nose weight forward. Obviously you don't need that, but you might use a phenolic 29mm tube as a spine to give some more rigidity. You could build some wood extensions off of that to mount your rail buttons to. Just a thought. If you are stuck with a particular motor limit, then you may consider redesigning it to be slightly shorter/lighter to keep with a thrust curve you are happy with. On these large light projects it is very easy to have things creep overweight very easily. Or you can go the other way, make it heavier and use a higher thrust motor than you originally planned.

Frank

 

[Nytrunner]

Hmmm. Good call against the G57. What kind of exit sppeds are you looking at?

I bet the low Mass/side area would exacerbate weathercocking if not going fast enough.

 

[Lowpuller]

Nytrunner,

You mean like this, just a light breeze.

https://youtu.be/yqDYqQMQP-E


I like the Thrust Curve minimum 50ft/sec

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[Nytrunner]

Oh yeah, that had near zero directional inertia lol. I never build that light, so my flights tend to stick closer to the edge of "nominal".

 

[burkefj]

Did you mean G75? that's the blackjack G75 not the metalstorm.

Frank

Hmmm. Good call against the G57. What kind of exit sppeds are you looking at?

I bet the low Mass/side area would exacerbate weathercocking if not going fast enough.

 

[boatgeek]

If you're not married to AT, the CTI G57 (2G 29mm) might possibly work as a low thrust option. It has the same initial thrust as the G53 but thrust doesn't taper off quite as fast as the G53. There's also the G88 Smokey Sam that is midway between the G53 and G76 in maximum thrust.

 

[Nytrunner]

If you're not married to AT, the CTI G57 (2G 29mm) might possibly work as a low thrust option. It has the same initial thrust as the G53 but thrust doesn't taper off quite as fast as the G53. There's also the G88 Smokey Sam that is midway between the G53 and G76 in maximum thrust.

Given the High drag, low mass of this thing, the G57 probably won't get him that initial velocity that he's looking for,

Although, I'm not sure how thrustcurve can be compared to these foam structures lol

 

[Lowpuller]

Ok payload section, basically complete, coming in at 9'4", the booster will add about 6', so in total she will be just under 16'. Made in three pieces for transportation. The payload section separates into 2 pieces.





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[Sooner Boomer]

You've got enough room for electronic deployment. Another option would be to use a rocket glider motor. The grains are slot-burners that transition to end burners - high initial power off the pad, tapering to a lesser, continuous thrust. Just an idea...

 

[LithosphereRocketry]

Given the High drag, low mass of this thing, the G57 probably won't get him that initial velocity that he's looking for,

Although, I'm not sure how thrustcurve can be compared to these foam structures lol

Using CTI, a G54 is perfect... It's a moonburner, so it lifts off at ~100N and drops off at a pretty much constant rate after that. (It's also the world's largest certified MPR motor and, not coincidentally, my #1 favorite motor of all time, at least until AT starts selling moonburning Dark Matter.)

55 oz on a G54 gives you 7:1 TWR off the pad.

 

[Lowpuller]

According to Thrust Curve a G54 is not fast enough off the rail.




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[Lowpuller]

Seeking advice from someone who has done this before.

Did you double the foam board on your fins?


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[DAllen]

According to Thrust Curve a G54 is not fast enough off the rail.




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How fast do you need to be? I mean, with the glider your fin area is going to humungous...although in a weird spot. Personally, I'd ditch the idea of going with a G motor and stick an H of some sort in there. If a CTI G54 isn't going to do it you're kinda screwed because that's right at the edge of a G rating since it's 159 NS.

I suppose you could find a higher impulse G but I don't really know what is available from CTI - if that's the direction you want to go. I'd be tempted to stick a G118 or G125 myself which uses the same case (I think) as the G54.

 

[Lowpuller]

Let me phrase my question better.

Did you use two layers of material for each fin?

I have double the fin size from the Decaf but I am concerned about them folding under load.


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[burkefj]

I would double them if they are made from foam board you may also consider putting in a spar or reinforcement along the span to the root to help flex/flutter. The primary issue will be landing crush/damage, so I'd put the spar out to the tip or whatever will likely hit the ground on landing. That's what I've done on my large foam structured/finned rockets. Or you can go with clear polycarbonate which is flexible, if your cg and rtf weight allows.

Frank

 

[Lowpuller]

Motor mount complete as well as a few other sub components





And the glider



Now for the fin can, I ended up using a single layer of foam board



And the core





And a quick dry fit



All three major components gathered for a dry fit

 

[Lowpuller]

Booster section assembled less rail guides and glider attachment point, and fin pods.





The top two payload sections will attach with masking tape at the field to ease delivery.

The payload sections including couplers are complete.

Booster section needs rail buttons, glider attachment, rail buttons and possibly fin pods.

I am unhappy with the fin alignment and frankly the overall appearance especially at the glue joints is poor.

This is not the type of rocket for the perfectionist.

Time for the final weigh then ordering motors, likely a G64 or G76.

If I finish putting it together, the motors arrive on tine and the wind is perfect, I hope to fly this weekend.

Debating weather maiden flight should be with the glider, most likely yes.

 

[CORZERO]