Rebuilding the Thunder'ceptor

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gothique_97

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I have a wnter/spring project that I hope to complete by the April Whitakers gathering. I'm going to rebuild my 10 year old Thunder'ceptor .

Its been sitting in my mother's garage in Connecticut since it last flew in 1996 [post-college life has kept it and most of my other rockets grounded for several years]. Well, last month, I drove up to the Northeast to visit family for the holidays, and packed the rocket into the car for the trip home.

The trouble is, this rocket only breaks down into two 6 foot long sections that were certainly not going to fit into my Neon [along with mine and my girlfriend's luggage, and presents]. I knew before even driving up there that I'd be cutting the rocket into fourths.

This had an added benefit; since its last flight, it had developed a small but noticeable kink in the lower section airframe just above the motor mount. Cutting the lower section in half would allow me to cut out the kinked tubing, or reinforce it with a coupler.

I didn't get to take a closer look at all of the parts till we got back to Georgia. Silly me; I didn't think of the tubing coupler already in the rocket when I cut it for transport. I cut the rocket too close to the coupler to simply put another couple in there to rejoin the pieces [I left less than an inch between the cut and the top of the coupler; hardly enough room for another coupler to hold the other half of the 3 inch airframe in place]. So in cutting out that and the kinked section, I'll loose about 8 inches from the overall length of 148 inches.

Another of the things that will have to be replaced are the 'spikes' on the lowest set of fin tips. They were made from Estes BT-5s and were bent all to hell before I even painted it. My plans are to replace these with 1/2" wood dowels cut carefully in half down the length and bevelled to sandwich the fin.

I'll also be replacing the 3/4" wide elastic shock cord with tubular nylon, my first time using that.

For you photo-fiends, photographic updates will be few and far between. Our digital camera died recently and we only have an analog camera to take pictures with. But I'll try to get text updates posted here as they happen and as time permits.
 
Actually got started on this project...

It turns out that this rocket was more robust than I remembered. For instance, I mounted the shock cord with 1/8" steel cable. Keep in mind, this is a 3 inch diameter, 6 pound rocket; 1/8" steel cable is a bit overkill. I cut the airframe just below the coupler, but ran into some problems where my carpet cutter wouldn't cut through the airframe. Turned out that there was plenty of epoxy overrun.

I cut the airframe right AT the bottom of the coupler, figuring on salvaging the 2 inches of kinked airframe right below that point with a new coupler that would join it with another section of 3 inch airframe. I just couldn't get the coupler to go into the kinked section of airframe. Next time I go work on it, I'll probably cut off the 2 inches of kinked airframe, and make my life a whole lot easier.

One thing I am going to have to do after cutting off what will amount to 10 inches of airframe is re-calculate the CP. So, if anyone wants to assist me in calculating the CP of a 11 foot, 3 inch diameter rocket with 16 fins, that would be very much appreciated.
 
gothique,

Let me know the shape of the fins using typical specs (root, span, tip, slant angle, etc) and I'll give it a try. Also where the fins are mounted, nose cone shape, etc. That should get you purty close.

Just checked out the link. The size and position of the forward fins will be VERY important in determining the CP!
 
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