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- Jan 18, 2009
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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:
https://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
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:
https://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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