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Cosmodrome Nike Apache

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JAL3

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Of the Consmodrome line, the 2 that have the most appeal to me are the Vostok and the Nike Apache. The Vostok has been sitting in my pile almost since the beginning of my return to rocketry intimidating me. The Nike Apache is a recent acquisition and does not seem nearly so intimidating. I decided to give it a try

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JAL3

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Construction started out by locating the 29mm motor tube and running a line down its length. An Estes angle was used to do this. Tick marks were then placed 1/2" from either end along the line.

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The kit came with 2 plywood centering rings. I had to locate the one with two notches, as opposed to the single notch ring, and the steel recovery harness.

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JAL3

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The loop in the steel cable was fitted through the 2 notches in the centering ring and then slipped into place on the motor mount at one of the tick marks. The ring was then epoxied into place.

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The other centering ring had only a larger, single notch in it. It was placed at the opposite end of the motor tube with the notch lined up over the line and epoxied into place, making sure that no epoxy obstructed the hole formed by the notch.

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JAL3

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The instructions indicated that I was to cut 2 pieces of cardstock, one was a strip 1.5x1/8" and the other was 1/2x1/8".

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JAL3

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A piece of threaded rod was then fed through the hole on the centering ring and the tube was marked at the point where 3/4" protruded from the end.

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JAL3

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It took a while for me to understand the purpose of the strips I had cut. The Instruction said to place them between the threaded rod and the motor tube. They did not indicate a purpose or an orientation. After a while, I realized that the longer strip terminated at the mark I had made for the rod and deduced, correctly I hope, that they are just to give a slight angle to the rod which is used for motor retention. I tacked the long strip in place and then the shorter one on top of it.

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JAL3

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The rod was then inserted to the mark and epoxied into place, taking care not to let epoxy onto the lower threads.

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JAL3

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The kit came with 4 plywood fins for the Nike portion of the stack. The instructions said to sand them down to a knife edge on the leading and trailing edges. I marked the centerline, got out a sanding block, sanded a bit and then reconsidered. There has to be a "good" way to do this right.

I would very much appreciate any advice on how to sand the fins.

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cosmodrome

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It took a while for me to understand the purpose of the strips I had cut. The Instruction said to place them between the threaded rod and the motor tube. They did not indicate a purpose or an orientation. After a while, I realized that the longer strip terminated at the mark I had made for the rod and deduced, correctly I hope, that they are just to give a slight angle to the rod which is used for motor retention. I tacked the long strip in place and then the shorter one on top of it.
I now see this needs to be clearified in the instructions. :confused2: The two strips are to move the threaded rod off the MMT just a bit. This is to give some clearence of the aft motor closure. It turns out that some aft closures are just slightly thicker than the MMT. I'm going to re-write the instructions a bit for this.
 

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The kit came with 4 plywood fins for the Nike portion of the stack. The instructions said to sand them down to a knife edge on the leading and trailing edges. I marked the centerline, got out a sanding block, sanded a bit and then reconsidered. There has to be a "good" way to do this right.

I would very much appreciate any advice on how to sand the fins.
I put one layer of masking tape on the center line, on the half that is not being sanded. I then add two more layers on this piece, about 1/16" tward the unsanded side. Start to sand. As the two additional layers of tape are sanded away, stop, remove then and add two new ones.

Alternately to hand sanding, I take a belt sander with the finest grit paper possible, and then sand a piece of scrap metal with it. This makes it extra dull. Than sand the fin. Careful, go slowely and check the progress often.
 

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You could also try using a metal file. Clamp the fins to a corner of your workbench and hold the file at the angle you need. Hold your arms steady and use your legs to rock your upper body back and forth. The longer stroke you get with a file makes it easier to achieve a flat bevel. I bevel all my fins but I didn't think it was possible to make that profile when I built my Nike-Ajax. I made the fins as built up paper with an internal frame of balsa. The cardstock was painted with epoxy glue on the inside and CA on the outside. I'll bet if you doubled up the paper, made the frame from the supplied plywood and added a fin tab for ttw the fins would be tough enough for 29mm power. Ted

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JAL3

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I put one layer of masking tape on the center line, on the half that is not being sanded. I then add two more layers on this piece, about 1/16" tward the unsanded side. Start to sand. As the two additional layers of tape are sanded away, stop, remove then and add two new ones.

Alternately to hand sanding, I take a belt sander with the finest grit paper possible, and then sand a piece of scrap metal with it. This makes it extra dull. Than sand the fin. Careful, go slowely and check the progress often.
I appreciate the advice.

I thought about using my belt sander but the finest I have been able to find is pretty course. I know that if I tried to do it the easy way, I'd wind up with little stubs.

Using the tape, how do you handle the second side? presumably with the first side sanded, that would change the angle.
 

JAL3

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You could also try using a metal file. Clamp the fins to a corner of your workbench and hold the file at the angle you need. Hold your arms steady and use your legs to rock your upper body back and forth. The longer stroke you get with a file makes it easier to achieve a flat bevel. I bevel all my fins but I didn't think it was possible to make that profile when I built my Nike-Ajax. I made the fins as built up paper with an internal frame of balsa. The cardstock was painted with epoxy glue on the inside and CA on the outside. I'll bet if you doubled up the paper, made the frame from the supplied plywood and added a fin tab for ttw the fins would be tough enough for 29mm power. Ted
Thanks for the input. Your description makes sense but what worries me is my lack of aptitude doing fine work. I'm talkign about doing fine work here. most of my efforts are gross.:confused2:

I've read about built up fins as you describe. I DO want to give it a try sometime.
 

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I wouldn't call your work gross. Your build threads show some fine work. I know paper fins seem daunting at first but they really aren't that tough when you dive in. Building TLP's Flail kit with paper fins gave me the confidence to try making my own. You can't see from the pic but the frame parts are beveled to conform with the shape. They do require some precise marking, cutting and folding. I use a thin 12 inch metal rule with the cork removed for all three tasks. A 0.5 tip mechanical pencil is essential for laying them out. If you would like it I can provide more details of the method. Ted
 

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I wouldn't call your work gross. Your build threads show some fine work. I know paper fins seem daunting at first but they really aren't that tough when you dive in. Building TLP's Flail kit with paper fins gave me the confidence to try making my own. You can't see from the pic but the frame parts are beveled to conform with the shape. They do require some precise marking, cutting and folding. I use a thin 12 inch metal rule with the cork removed for all three tasks. A 0.5 tip mechanical pencil is essential for laying them out. If you would like it I can provide more details of the method. Ted
I guess I should have said course instead of gross. What I mean is that I can do ok with big things or things that are seen from a distance. Precision work is tough though.

I'm interested in learning just about any new technique. I may not be any good at it but I am interested in learning.
 

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After hearing back from Cosmodrome on TRF, I adopted the manufacturer's recommended practice for sanding in the correct profile to the fins. I applied a wide strip of masking tape along the line I had marked on the side opposite to which I wanted to sand. I then put two more strips of narrower tape right on top of it and did the same to the reverse side. A sanding block was then repeated drawn along the side to be sanded gradually removing material. When the sandpaper had eaten through the top two pieces of tape, the tape was replaced and the process continued.

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I found that for each surface of each side of each fin, I would have to replace the tape about 4 times in order to achieve the "knife edge". Be advised that I am speaking in terms of butter knives, I was afraid of ruing the fins by sanding any more. I got 1 fin done per day because it does take time and, frankly, was not an enjoyable process for me. That being said, it was effective and I have not complaints. I think the result will be worth it.

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With three fins done and a fourth one waiting to be done, I stared dejectedly at my dwindling supply of course sandpaper and looked wistfully towards my belt sander. Against my better judgment, I decided to give it a try. I masked off the high areas as before, flipped the switch and hoped that I was not destroying the fin. It actually went easier and slower than I expected with SLOW being the key word. I was able to give the fin an acceptable profile and avoid a trip to the hardware store.

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At this point I would like to ask for some help from anyone who has built this or similar kits in the past.

THe next step involves marking the BT for the fins and applying some plastic wrap. I'm afraid I just don't understand what the goal is or what is meant. Can somebody give me a clue?
 

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At this point I would like to ask for some help from anyone who has built this or similar kits in the past.

THe next step involves marking the BT for the fins and applying some plastic wrap. I'm afraid I just don't understand what the goal is or what is meant. Can somebody give me a clue?
 

cosmodrome

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With three fins done and a fourth one waiting to be done, I stared dejectedly at my dwindling supply of course sandpaper and looked wistfully towards my belt sander. Against my better judgment, I decided to give it a try. I masked off the high areas as before, flipped the switch and hoped that I was not destroying the fin. It actually went easier and slower than I expected with SLOW being the key word. I was able to give the fin an acceptable profile and avoid a trip to the hardware store.
The goal of this step is to from the body tube wrap. I have you get the card stock wet so that it curves around the body tube without creasing. It is then dried in place to help hold the shape. The purpose of the plastic wrap is to keep the body tube from getting wet from the wrap. Once the wrap is dry, the plastic wrap is removed and the wrap is grued into place. The fin lines are then re-drawn over the wrap. Cut fin slots, add fins, etc.

Let me know if this helps.
 

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With three fins done and a fourth one waiting to be done, I stared dejectedly at my dwindling supply of course sandpaper and looked wistfully towards my belt sander. Against my better judgment, I decided to give it a try. I masked off the high areas as before, flipped the switch and hoped that I was not destroying the fin. It actually went easier and slower than I expected with SLOW being the key word. I was able to give the fin an acceptable profile and avoid a trip to the hardware store.
Looks like you're ready to tackle some Black Brant II fins. :D
 

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Looks like you're ready to tackle some Black Brant II fins. :D
I'm still dreaming in terms of the Vostok.

Now I just need to get to the store and get some plastic wrap.
 

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I'm still dreaming in terms of the Vostok.

Now I just need to get to the store and get some plastic wrap.
Plastic wrap, wax paper, aluminum foil, anything to keep the water from getting to the body tube.

The Apache wraps will be a good practice for the Vostok shrouds. :D
 

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Plastic wrap, wax paper, aluminum foil, anything to keep the water from getting to the body tube.

The Apache wraps will be a good practice for the Vostok shrouds. :D
Is that supposed to BOLSTER my confidence?
 

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The last page of the instructions came with a fin marking guide of the type where you set the rocket on teh circle and make your marks. I generally prefer the wrap around type but don't knock any points for this type. This is especially with so since, for me, the butt types are not as difficult to use with the larger tubes. It also helps with both types when the sizes are dead on and this one was.

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