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Talos RIM-8 J GENERAL Build Layout

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El Phantasmo

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I've decided to build a scale Talos RIM-8 from parts I can purchase. The CAD drawing is my own work. The dimensions (not shown) are not true to scale as they have been rounded off the the nearest 1/16 in. And I came across some conflicting data, but I used the data from the sources I trusted most.

All fins would mount through the 4in "outer body tube" and into but not through the 3in "inner body tube." I don't plan to support the "inner body tube" with anything else but the fins and a coupler where the booster joins. I'm still not sure if this is going to be a single or two stage rocket, and that will influence where the recovery stuff will go.

The curve of the "outer body tube will come from cutting off the ends of a 4in nose cone. The nose cone of the "inner body tube" would be a composite of two modified nose cones, to achieve a truer look. The overall length is about 66in.

Might the "double body" do undesirable/unsafe things in flight?

All comments are welcomed.





 
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ben_ullman

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Ditch the double body idea. Its really not doing anything for you but adding weight. Just contact Sandman on the forum, he will make you a nosecone to scale.

Ben
 

El Phantasmo

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Ditch the double body idea. Its really not doing anything for you but adding weight. Just contact Sandman on the forum, he will make you a nosecone to scale.

Ben
Is there a feasible way to get the look of the ram jet w/o creating an inset nosecone that creates a huge amount of drag? I'm mostly trying to replicate the look, speed and altitude are very much secondary.
 
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ben_ullman

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Is there a feasible way to get the look of the ram jet w/o creating an inset nosecone that creates a huge amount of drag? I'm mostly trying to replicate the look, speed and altitude are very much secondary.
yes, Just do like you are thinking. use a noseceone inside a nosecone. you jus don't need 2 BT's and such.

Ben
 

cjl

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Is there a feasible way to get the look of the ram jet w/o creating an inset nosecone that creates a huge amount of drag? I'm mostly trying to replicate the look, speed and altitude are very much secondary.
The nosecone will create a huge amount of drag, whether or not you do a double body design.
 

Handeman

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The nose cone will be draggy, but maybe not as much as you think. As long as there is no way for the air to flow through the gap between the two, pressure will build up and cause the air flow to go over the outer edge. It will still be like having a flat ring on a standard nose cone, but it shouldn't be too bad.
 

new2hpr

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Just do like Estes did on their ramjet style nosecones; make the "intake" recessed part flat instead. Still not very streamlined, but better.

-Ken
 

sandman

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^^^^^ Told ya Gordy would fix ya up right!!! :D

Ben
Actually it was a proposed kit.

Unfortunately the amount of nose weight required to make it stable almost guaranteed a broken fin on every landing.

But maybe.:rolleyes:

The best arrangement of fins was a BT-70 booster and a SEMROC ST-20 upper stage.
 
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ben_ullman

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Actually it was a proposed kit.

Unfortunately the amount of nose weight required to make it stable almost guaranteed a broken fin on every landing.

But maybe.:rolleyes:

The best arrangement of fins was a BT-70 booster and a SEMROC ST-20 upper stage.
wow, it just doesn't seem that unstable. Cool looking none the less!

Ben
 

Handeman

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wow, it just doesn't seem that unstable. Cool looking none the less!

Ben
Ben, what do you mean, "doesn't seem that unstable"? It's got mid fins almost the size of the aft fins, and large forward fins too. It looks very unstable without a huge amount of nose weight. The CP looks to be above the middle fins and the CG with any motor would be about half way between the middle and aft fins. About -2 to -3 calibers of stability.
 

Marlin523

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Really cool project. I hope you will post pics when it is not only finished, but painted.
 

El Phantasmo

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Ok, I'm ditching the double body tube design, but not the general nosecone build yet. Below is a new drawing. Again the body shape will taper from a nosecone with the end cut off. Although, I'm not sure whether to make the inner cone from 2 cones or just one. All nosecones are currently plastic.

Anyone know where or if I can find a 3" ellipse plastic nosecone? Spherically blunted is actually preferable. My internet searching has been fruitless; all I can find is ogive.

Looks like the US Navy solved the weight/balance issue by using Plutonium and what not in the inner cone.

Talos-4in-mod-2.png
 
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El Phantasmo

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One thing I'm going to neglect is the slight shift in diameter from the upper section and the booster. On the real Talos it's all of about 2" different, so at about 1/7th scale I'm not bothering.
 

powderburner

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I've decided to build a scale Talos RIM-8 from parts I can purchase. The CAD drawing is my own work.
Here's one possible approach to making a stable, flyable model out of this. (I've been dabbling with drawing up this one too but I am nowhere near building.) First, to get sufficient "bypass" airflow around the core body, I think you might want to keep the diam of the inner body closer to half the diam of the outer body (or less). If the bypass airflow space (between the inner and outer BT) gets too snug the airflow will begin to suffer from boundary layer buildup (on internal surfaces) and will end up stalled somewhere along the length, effectively blocking any useful bypass airflow. I think your 0.5 inch wide bypass airflow (width of path on either side) is going to be pushing into the territory of "stalled flow" for a path length as long as you are planning.

I think the nose cone "shape" in the inlet should not be much (if any) bigger than the smaller diam for the inner body. This advice is based purely on qualitative assessment instead of analysis or more quantitative computation, but that NC and inner body will have to leave a significant path for bypass air. I think you will be OK (with a four inch outer BT) if the inner body diam is 1.5 to 2 inches (maybe even as big as 2.25 to 2.5 inches?). The smaller diam for the nose body may result in a less-than-scale appearance but I think that's what you're going to have to work with.

Second, I would keep the inner body as short as possible, only enough length to hold the motor and recovery system. This should get the motor forward into the middle of the rocket (or even slightly further forward) and the rest of the outer rocket body then serves as a thrust tube to contain the mixed exhaust. (If you don't build the back end too heavily.)

You will need an access break at (or immediately below) the nozzle location when the motor is installed. You can do this by cutting the outer body tube and using a coupler (glued to one side or the other) just as if you had a normal two-stage design. The joint might fall right behind the first set of fins. Open up the joint to install motor and igniter, re-assemble the rocket for launch and secure the two body pieces with an outer tape wrap or with a pair of nylon screws.

Drawback: you won't be able to make a two-stage model with a separating booster, and the whole thing will remain in one piece throughout the flight. And if you select a motor that is too "big" you could end up with some roasted surfaces on the inside of the BT.

Advantage: all those fins can now be located behind the model's cg where they will help you. You could CHAD stage a motor (if you are using low power) and just let it fall out the rear, and the booster would still be located well forward inside the model (it wouldn't destabilize the model too badly)
 
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H_Rocket

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Mike Stoop of Madcow set me up with a prototype 2.6" Talos kit. I flew it three times and it never was quite stable. The massive fin area made it very unstable and prone to the wind pushing it sideways. I had almost 4oz of nose weight in a 30" long model. The last flight it looked like it was a real SAM as is went in every which direction seemingly beam riding after a dragonfly on acid.

I want to rebuild it, however it is a bit down on the work list.

Somewhere I have an in flight picture.
 

El Phantasmo

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Here's another design; it goes back to the double tube architecture. I thought the 3" inner tube might cause some air flow restrictions, so I'm glad that was mentioned. Now the inner tube is about 1 5/8" in diameter. The nosecone has been simplified to a 2 1/2" diameter plastic ball with a cone on top. A good sized 38mm motor is fine.

But where's the parachute going to fit? Should I use 2 chutes and a long shock cord (one chute in the lower and one in the upper)?

Talos-4-2.png
 

cjl

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Honestly, I'd bet that you would get more altitude if you ditched the double tube idea. I doubt that the (minimal at best) drag improvement would offset the increased weight. It would also make the recovery setup quite a bit easier.
 

El Phantasmo

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Nothing is set in stone. Right now, I'm just pitching around ideas for feedback.

Thanks to everyone so far.
 

GregGleason

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Is there a feasible way to get the look of the ram jet w/o creating an inset nosecone that creates a huge amount of drag? I'm mostly trying to replicate the look, speed and altitude are very much secondary.
One thought is that you can build it as you describe, then fill a small portion of the void that is tangent to the outer tube with epoxy. It dries clear so you get the effect without as much of a drag penalty.

Another thought is create a "flight ring" that you add whenever you fly. This is a clear ring that sits inside the ramjet, again that is tangent to the OD of the outer tube. Then you remove it when it is on display. This would be one of those "ADD BEFORE FLIGHT" items.

Greg
 
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