Airbourne Survellance Missile, Estes kit #0867

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Here's a trick if you want a "quick-n-easy" fin placement guide without having to print and glue up and cut out templates...

Take a sheet of printer paper and wrap it around the body tube tightly, and make a mark where it overlaps the end of the paper sheet, with an arrow pointing back toward the overlapped edge (reference so you measure to the right end from then on). Remove the sheet of paper and lay it flat, measure from the overlapped edge to the mark. Measure the other side of the sheet and duplicate the mark on the opposite edge of the paper, and connect the marks with a ruler. This is the tube circumference.

Next, select a number that is an easy multiple of the number of fins you plan to use, that is also greater than the tube circumference. Say the tube circumference is 8.75 inches, and you want to use 4 fins. 10 would be a good choice (because 2.5x4=10). Line the ruler up with the corner of the paper, pivot the other end until the "10" mark lines up with the circumference line across the paper you made earlier, forming a long slender 'triangle' across the paper. Make the marks at the selected "multiple number" you chose earlier (2.5 in our example) so you'd put marks at 2.5, 5, and 7.5 inches. Flip the paper to the opposite edge and repeat. Connect the fin placement lines across the paper and extend them to the edge of the paper-- this ensures they're all square to each other and the paper edge. Wrap the sheet around the rocket again, tape it with a bit of tape, and transfer the fin placement lines to the tube.

Voila you're done! Quick and easy.

Course, your templates are nice too... :)

Later! OL JR :)
 
Here's a trick if you want a "quick-n-easy" fin placement guide without having to print and glue up and cut out templates...

Take a sheet of printer paper and wrap it around the body tube tightly, and make a mark where it overlaps the end of the paper sheet, with an arrow pointing back toward the overlapped edge (reference so you measure to the right end from then on). Remove the sheet of paper and lay it flat, measure from the overlapped edge to the mark. Measure the other side of the sheet and duplicate the mark on the opposite edge of the paper, and connect the marks with a ruler. This is the tube circumference.

Next, select a number that is an easy multiple of the number of fins you plan to use, that is also greater than the tube circumference. Say the tube circumference is 8.75 inches, and you want to use 4 fins. 10 would be a good choice (because 2.5x4=10). Line the ruler up with the corner of the paper, pivot the other end until the "10" mark lines up with the circumference line across the paper you made earlier, forming a long slender 'triangle' across the paper. Make the marks at the selected "multiple number" you chose earlier (2.5 in our example) so you'd put marks at 2.5, 5, and 7.5 inches. Flip the paper to the opposite edge and repeat. Connect the fin placement lines across the paper and extend them to the edge of the paper-- this ensures they're all square to each other and the paper edge. Wrap the sheet around the rocket again, tape it with a bit of tape, and transfer the fin placement lines to the tube.

Voila you're done! Quick and easy.

Course, your templates are nice too... :)

Later! OL JR :)



That's quite a different way to make a fin placement guide. Thanks for letting me know about it. I'll give it a try sometime in the future.
 
That's quite a different way to make a fin placement guide. Thanks for letting me know about it. I'll give it a try sometime in the future.

Old drafting trick... use it all the time... :) It's a lot harder to type how to do it than it actually is TO do it! LOL:)

Later! OL JR :)
 
A few scale measurements.

Expand the photos to see details. A paper wrap was used to apply those measurements to the BT-60 and the 3 inch body tube.

The angled aluminum is used to extend the tic markes made from the fin placement guides.

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Aprrox. 34 inches of coolness starting to come together.

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What could I use to make this ring in step five?
To read the instructions and my notes, follow these steps:

You need to place the curser on the photograph of the instructions and right click the mouse.

Then select the "Open Link" option.

A larger window with the same notes and instructions on it comes up.

Move the curser down to the bottom right hand corner of the screen. To the right of the percentage box is an arrow.

Click on the arrow.

Select 200%.

Now you can read the instructions and my notes on modifiying the instructions.

I know there's got to be at least one person out there that didn't know how to do that. Now they do.

Go back to post #36 and reexsamine the notes for step one on that page of instructions.

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Parts for cobbling a baffle together. Expand pic 3 to see detail. See post #41.

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Here's how the baffle works. Expand picture to see details (See post #41).

The pressure wave from the ejection charge has to move up the motor tube because the motor hardware is mechanicly secured into place, blocking one of the two exits. The path of least resistance is up the motor tube, through the baffle, into the parachute compartment, pushing out the parachute and nose cone to reach the only exit available to the pressure wave. Unless there's a CATO and a new exit is created. :shock:
The path the pressure wave has to take is already full of cool air. As the pressure wave travels up the motor tube it's forcing the cool air up the motor tube, through the baffle and pushing out the parachute. The parachute is deployed by cool air and will be long gone before any hot gas from the ejection charge reaches the parachute compartment. Pretty cool! :bangbang:
 

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Interesting.

A+ for your presentation !

I don`t remember ,what is the finished length of the rocket ?

Paul T
 
34" sounds like a good size.Me thinks I gots to make me one of those......if you don`t mind ;)


Paul
 
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Baffle parts.

The top for the baffle cup will be epoxyed and filleted, inside and out so it has a real good grip on the baffle walls.

After being epoxyed into place, the wood dowels will support, suspend and secure the baffle cup above the end of the motor tube (with the aid of a aluminum strap and two wood screws).

Bottom of the baffle will be epoxyed onto the centering ring that's already epoxed to the motor tube.

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One baffle. No need for the screws to be tightend yet. The baffle is also the anchoring point for the shock cord. The cup is removable for maintenance or to use another deployment set up.

Baffle waiting to be epoxyed to it's bottom centering ring on the motor tube.

Aprox. placement of baffle in the three inch body tube.

Baffle flow.

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Before and after shots.

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That's an interesting baffle set-up... is/does the inner tube have holes drilled? Or is the idea to allow the gases to pass thru the outside tube/chamber?
 
That's an interesting baffle set-up... is/does the inner tube have holes drilled? Or is the idea to allow the gases to pass thru the outside tube/chamber?

No holes drilled in the inner tube. Yes, the gases are allowed to pass thru (up and out) the outside tube/chamber.
 
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Here's how the baffle works. ... The pressure wave from the ejection charge has to move up the motor tube. .... The path the pressure wave has to take is already full of cool air. As the pressure wave travels up the motor tube it's forcing the cool air up the motor tube, through the baffle and pushing out the parachute. The parachute is deployed by cool air and will be long gone before any hot gas from the ejection charge reaches the parachute compartment. Pretty cool!

Very well explained. Thank you. Using the insulating effects of distance as a piston. Makes perfect sense, and also explains why we add vent holes in the coupler when gap staging. Good looking rocket, enjoying following your build.
 
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