Estes Screamin' Mimi

[trogdor]

Just some notes and pics on a neat new kit I recently picked up after seeing a name and similar feature to a scratch design I called El Gordo...


Estes Screamin' Mimi EST2185 Skill Level 2

New for 2003

From packaging:

BT-60
25.5 inches long
5.3 ounces
18 inch parachute
C11-3, For Sound: D12-5, D12-7

"FITTED WITH 4 SUPER SONIC WHISTLES!"
"'sCREAMS' TO OVER 500 FT!"

Sealed in new packaging weighs 6.7 ounces

Package contains 3 bags of parts containing the parachute, die-cut balsa fin stock and remaining small parts including 4 round whistles and another small bag of parts.

Very professional packaging; every plastic bag has neat seals and small air holes.

4 page directions

Balsa sheets: 1.6 oz. , 0.9 oz fins only
Parts only (no stickers) 4.0 oz.

1/8 inch hard balsa stock good die-cutting, parts fell out after a couple corners cut.

4 - 4 inch BT-20
4 - whistles
4 - 1/4 inch BT-20 coupler
1 - 2 3/4 inch BT-50 engine mount
1 - 1 inch coupler loose fit over BT-50
1 - 18 inch parachute
1 - engine hook
1 - 24mm engine block
1 - 2 inch 3/16 inch launch lug
2 - 1/16 inch cardboard centering rings
1 - 18 inch BT-60
1 - PNC Mean machine/Der Red Max style(I think)
1 - 1/4 x 24 1/2 inch shock cord

Started prep by sanding outer surface of body tube and whistle tubes where fins would be glued. Also applied thin CA to ends of body tube and motor tube to strengthen and prevent unraveling of the tube.

Started assembly with motor mount. I deviated from instructions by cutting another motor mount tube from thicker LOC 24mm tubing and sanding the inside of the centering rings for fit on the thicker tubes. Also used odorless thin CA with accelerator.

Typical assembly steps follow including fin sanding and shaping and marking the tubes for all 8 fins and launch lug.

Glued motor mount in with liquid nails wood glue.

Next step is building the whistle tubes. As I've NEVER had luck with using plastic cement with plastic and paper tubing joints with model rocket kits, I used thin CA with similar terrible results! So, a little 5 minute epoxy fixed everything! I was a little surprised by the CA not working as I thought I read somewhere about it working well... but then theres the thing with the odorless CA maybe being the issue?? dunno...

Attaching the fins was a little difficult because there were so many close together. I also found the thin odorless CA to work poorly unless a thicker bead was used and accelerator applied immediatley afterward. This method produced strong joints that I am used to with normal teary-eye thin CA.


Built, no finishing 4.3 oz.

Not flown yet, WAY TOO cold on the East coast these days!

 

[trogdor]

Here's a pic of parts

 

[trogdor]

Here's model as a 4FNC

 

[trogdor]

here's the completed model, no painting yet

 

[trogdor]

and finally here's El Gordo (thought of naming it Screamin' Mimi but changed my mind at the last second before I filled out that first flight card making the name official! ) that I built last year. I had the idea for whistles independant of anything I saw from others since the mid 90s but never did anything about it.. thought about those little party whistles for a couple years and finally ended up in a party store with my wife and found some... thus El Gordo was born. El Gordo is basically a 16 inch shortened Broadsword with 8 "Sirenen" whistles from the party store and a BB enhanced 5.5 ounce nose cone (too much I think)... basically a Broadsword about as short as it gets with lotsa nose weight! (Initial unweighted nose produced really neat horizontal spirally flights! It did actually glide horizontally in the wind!)

Didn't have luck with the whistling though even on an F39... think I need to extend the whistles with "whistle tubes" like the Screamin' Mimi, maybe even extending past the body tube next to the nose?? Think I'll try that and see what happens... seems too much clutter near the end of the rocket without enough air forced through the whistles.

 

[WanderingWheel]

A stock Screamin' Mimi got a couple of flights this weekend at our launch and even with the small motors, you could barely hear the whistles over the motor. I doubt they would do anything but create drag on your rocket. It's not an issue of speed either. Blow into them and you will see that they don't need much airflow to work. They are just not loud enough.

 

[jflis]

That's acutally a pretty cool looking rocket. Had never seen one built before.

question, are the whistles located at the rear of the tubes? I ask because while in flight (you'd be surprised), the air flow will have a tendancy to flow AROUND the top end of the tube and not that much will go into the tube. you run into two effects here.

1) The airflow running off of the nose cone has a rolling turbulance that will roll away from the body (and the whistle tubes) and,

2) with the bottom of the tube partially blocked by the whistle itself, you get a high pressure area in the top of that tube that acts to deflect the air flow

That is one of the reasons that it doesn't whistle much on most motors.

 

[trogdor]

Yes, the whistles are at the bottom of the tubes...

I kinda figured that on El Gordo the issue was the airflow over the short section of the tube part of the whistle before the actual blades and the close proximity to the body and fins... I figured the Screamin Mimi might solve some of that by moving the whistles out of the airflow of the body tube and fins on those pods and provide more pressure because of the long tubes before the actual whistle. I remember reading a part in Stines book about an extremely large Cd with basically an empty blocked tube instead of a nose cone so I was thinking that the air flowing through a tube would allow more air to actual go through the entire device rather than be blocked and flow around as in my design... then there's always another F39!!

I'll see how mimi does on progressively larger motors and if results are good, I'll just add extensions onto El Gordo to replicate the mimi idea of the longer tubes extending up and maybe even with the nose cone (perhaps past the shoulder?)..

I also though about making the whistle tubes a large diameter and funneling the air into the whistle.. maybe a BT-50 down to the BT20ish size of the whistles.... that would seem to help too...

 

[trogdor]

Oh ya, wandering wheel... as for the whistles not needing much pessure, ya that's if you seal your mouth and force air through... in the free flowing environment of an actual flight it seems to be an issue with the air taking the path of least resistance around the tubes... my design only barely whistled too... maybe funnel things on the mimi design at the front as well can help... but then all this drag makes seeing an entire burn of a 24mm F motor pretty cool! I kinda like low and slow sometimes and if its loud too all the better!

 

[firemanup]

Completed ours last week, yet to fly but listening to the talk about the airflow, I'm thinking yall are right, didn't think about that before buying it though.

Still a different and kind of fun build though. Hate the stock silver though, had to change that.

<img src="https://members.aol.com/rocketcollector/images/mimi.jpg">

Jason

 

[trogdor]

hey nice paint.. I haven't gotten to paint mine yet but am still thinking about hollowing out some nc50 size nose cones to use as funnels for more airflow on the whistletubes! and im upset i forgot to clip the engine hook on the inside so rms would fit... darn!

 

[Fishhead]

I bought one at Hobby Lobby and gave the "whistles" to my kids to play with. It's not a bad looking rocket without them. When you hear the sound they make you'll realize how difficult they'll be to hear even under optimal conditions.

 

[KermieD]

Would it help to put the whistles on top of the tubes instead of the bottom?

 

[trogdor]

I think not as it would be similar to my El Gordo... I think the tube gives a volume for air to be forced through the whistles instead of an easy way around the whistle... if my wording makes sense! Anyway, I have much testing to do with this even if I need G motors and 50 of these whistles... I want to make it work... maybe just an air horn in the nose and be done with it!!

We'll see as soon as the fields dry! It was SO warm today, almost put the top down but the roads were too wet!

REALLY wanted to go to the field but its probably a mess right now...

 

[KermieD]

LOL...as usual, my thinking is way off. I shoulda been an engineer. I'd be the guy who designed the AMC Pacer.

Anyway, got one of these at the last HL sale. Another one I haven't built yet.

 

[rbeckey]

Ok, I realize the drag penalty on this would be outrageous. Put the whistles at the top of the tubes and made a transition out of card stock, and stick it on top of the whistles, like a funnel. Coat it with CA to stiffen. If I had one of these kits, I'd give it a try.

 

[trogdor]

ya! I've been thinking of the inverted nose cone funnel idea but how about really big pods with a BT80 size nose cone funnel! YA that should do it! Have like 8 of them around the rocket... and use an O motor... ya...

 

[gerbs4me]

I've got a Screamin' Mimi, I just need to build it, too many other projects going on at once.

 

[TheRadiator]

Just bought one today. I was thinking of a 29mm motor mount. Heck, the tube is big enough! I just wonder if 30 minute epoxy will hold the whistles on. Update coming later.............

 

[iceage]

Originally posted by TheRadiator
Just bought one today. I was thinking of a 29mm motor mount. Heck, the tube is big enough! I just wonder if 30 minute epoxy will hold the whistles on. Update coming later.............

That's the spirit! Two-ton epoxy and G64's! I need to go to Wal-Mart and find some whistles.

Patrick

 

[sandman]

Years and years ago I bought an arrow head at a local hardware store (they had a sporting goods dept. in the back) that was a very very loud whistle.

I immedietly thought of that when I got my Screaming Mimi.

How about glueing them together like a four engine cluster and mounting them right on the nose?

That would put them right IN the airstream!

The drag shouldn't be any worse than hanging them onto the side.

sorta like this.

sandman

 

[TheRadiator]

Hmmm, I like that idea! Don't have to worry about those balsa mounts breaking either...... hmmmmmmm, mebbe I need to go back and get another! Well, I'll finish up the 29mm mount, and then I'll go get the other one! If I didn't lack clustering ability, I'd look into a 4x13mm+3x18mm cluster..... kind of overkill, but at least it would look cool going up, or plowing into the ground.:kill:

 

[Justy]

Another idea might be to have a short tube behind the whistle, turned out, so that its opening is almost perpendicular to the rocket body... air blowing past the opening should create a vacum, right?

 

[trogdor]

Well, I tried an E30 recently and still the whistles only sorta worked.... i need to either find a better whistle or just pop out a small air horn and let that blast all the way down!!

 

[TheRadiator]

On second thought, I'd probably never hear those whistles over the likes of an F20 anyways. Hmmmm, if only I could get a Cadillac horn to work on a D-cell.....