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How to Cut Slots in Blue Tube

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jadebox

Roger Smith
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In January, I launched my "Tikva" on a motor that was just a little too powerful for the clear Lexan I had used for the fins. As you can see in the video, significant fin flutter occured. One of the fins snapped in half.

Even though the fins were mounted to wood braces inside the booster, I found that I was able to remove them with only a little swearing and not much damage to my fingers or the rocket's fiberglass body tube.

I used a chisel to break the joint between the rear centering ring and the body tube. Since the tube had been slotted all the way to the end, I was able to peel each section up to get to the fins. Only one section of the body tube broke and I could repair it with a sufficient amount of filling and sanding.

So, it would be possible to replace the fins and rebuild the booster using the existing body tube. But, it would be a lot of work making the result look nice.

So, I decided to replace the body tube.

I ordered a length of 4" diameter Blue Tube from AAR which I'm going to use to rebuild the booster. I'm going to cut the old body tube just above the upper centering ring of the motor mount so that I can re-use the motor mount, centering rings, and (most importantly) the Aeropack retainer. I'll try to make the cut clean so I can use the upper part of the old body tube in a later project.

As with the original booster, I'm going to make four large fins to, hopefully, reduce the amount the rocket rolls on the way up. This time, however, they are being made of G-10 (I found some sheets of it at a local surplus store) and I'll make them trapezoidal to reduce the chance of flutter and breakage.

So, anyway .... what was my question?

Oh, yeah .... for the original Tikva, I cut slots for the fins by marking the outline for the slots with masking tape. Then I sat down with my Dremel and a cutting disk and cut them out. The result wasn't bad.

This time, however, I'm thinking of using either my router or table saw as decribed at:

http://www.jcrocket.com/finslots.shtml

My question is, does using Blue Tube make any difference in the technique? Do I, for example, need a special router bit or saw blade?

-- Roger
 
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ttabbal

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I used a miter saw with the wood blade it came with and it worked fine on blue tube, phoenolic and dyna-wind. I don't see any reason a table saw or router wouldn't work with the standard wood cutting blades so long as they are sharp.
 

kandsrockets

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Router with a spiral up cut bit will work. I use this for cardboard tubes, phenolic and glass tubes and cuts a nice clean slot.
 

SteelyEyed

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I just used a dremel tool and a cutoff wheel. I lined the slots with painters tape and used the tape as a guide and cut them freehand. Take a look at my Bolaero-Endgame thread on this site (there are lots of photos). Once you start a cut straight, it tends to track straight. I had no difficulty.
 

deandome

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All hail the mighty Ryobi BT3K table saw!!!

Nothing on the market does/did as much, as well, for the $$ as this machine. Scoff all you want, Unisaw/Powermatic owners...in the end, the BT3K OWNS YOU!!!! :bangpan:


http://www.bt3central.com/
 

jadebox

Roger Smith
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Thanks for the suggestions. I just got the Blue Tube tube in the mail. It's kind of misleading. It looks like a giant blue Estes paper tube and feels sort of like paper. But, I accidentally dropped it on our tile floor and it bounced, almost back into my hand! :)

--- Roger
 

AHansom

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I have had pretty good succsess using a table saw for slotting body tubes. Make a triangle or square guide depending on if three or four fins are needed out of somthing laying around like thin plywood or masonite. The outside of the guide needs to be the same size as the diameter of the body tube so the guide and body tube will rest evenly on the saw. Epoxy the guide to one end of the tube. Set the cut to 1/2 the body diameter put a mark or stop on the saw to keep the cuts even length. The guide holds the body tube from rotating while making the cut and the body tube resting aganst the fence and table keeps the cut straight.

DSCN0705.jpg
 
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dlb

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I second the Dremel and a cutting blade

use them on all my app's, cardboard to carbon fiber.
 

jadebox

Roger Smith
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I have had pretty good succsess using a table saw for slotting body tubes. Make a triangle or square guide depending on if three or four fins are needed out of somthing laying around like thin plywood or masonite. The outside of the guide needs to be the same size as the diameter of the body tube so the guide and body tube will rest evenly on the saw. Epoxy the guide to one end of the tube. Set the cut to 1/2 the body diameter put a mark or stop on the saw to keep the cuts even length. The guide holds the body tube from rotating while making the cut and the body tube resting aganst the fence and table keeps the cut straight.
That's a neat idea. Looks like I need to add a new template tool to PayloadBay.com. :)

-- Roger
 

jadebox

Roger Smith
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I have had pretty good succsess using a table saw for slotting body tubes. Make a triangle or square guide depending on if three or four fins are needed out of somthing laying around like thin plywood or masonite. The outside of the guide needs to be the same size as the diameter of the body tube so the guide and body tube will rest evenly on the saw. Epoxy the guide to one end of the tube. Set the cut to 1/2 the body diameter put a mark or stop on the saw to keep the cuts even length. The guide holds the body tube from rotating while making the cut and the body tube resting aganst the fence and table keeps the cut straight.
During lunch, I added a "tool" to PayloadBay.com to print a template for a fin slot jig like you describe. It works for three or four fin rockets:

http://www.payloadbay.com/index.php?page=Tools&action=SLOTGUIDE

Of course, I'm cutting four fin slots, so the design of the jig is much simplier. :)

-- Roger
 
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