3" Semi-Scale Bullpup Build

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qquake2k

Captain Low-N-Slow
Joined
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I'm back!

Three years ago when I got my Jet lathe, I turned a tailcone for a 3" Bullpup that I really didn't plan on building. I only turned it because I had a short piece of basswood left over, and thought it would be simple and fun. It was, and I successfully turned it. Fast forward three years, and my Secret Santa gift at work was an Estes Bullpup 12D kit. That got me thinking about the tailcone, and I dug it out. I thought about a 3" upscale for several days, and even played around with the Open Rocket file I had made then. I rooted around and found a length of LOC 3.1" tubing, along with a 29mm motor tube. I thought about ordering a LOC nose cone, but then I found a 16" piece of basswood I had. So to make a long story short, I decided to go for it.

https://www.rocketryforum.com/showthread.php?60359-A-thing-of-beauty!&p=627474#post627474


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I have a nice 3" faceplate for my lathe, which is threaded in the center for a 1/4-20 hanger bolt. That allows it to be used as a screw chuck. I put a #8 screw through the hole and attached it to the basswood to center the faceplate. I marked the four mounting hole positions with a transfer punch, then drilled pilot holes and attached the faceplate with #10 woodscrews.

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The nose cone doesn't require any weight, but I decided to embed the eyebolt in resin, as I've done in the past. I trust it more than using a screweye. So I removed the faceplate, and started to drill a 1" hole in it with a spade bit. Well, that didn't work. The spade bit I used is threaded on the tip, to help "pull" the bit into the wood. Since I didn't have the basswood mounted in a vise, the bit immediately grabbed it and drilled at an angle. Bummer. I decided to try drilling out the hole with an S&D 1" bit. That didn't work either. Bummer.

The block is 16" long, and the finished nose cone will be 12-1/2" with a 2" shoulder. I think I can trim off the damaged section, and start over. I think.


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As it turns out, I have a drill press vise that the basswood block fits into. I should have used it the first time, but I will definitely use it the second time.

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The best build threads ever!!!!!!!!Glad you decided to build it Jim.Now I might get off my rear end and work on my V2.
 
The Captain in Back!!!!!!!! This year is already better than last because we have a Jim build thread.
 
I've had much better luck using Forstner bits. Spade bits tend to grab as you've illustrated in your nose cone.
 
A new build thread from Captain Low 'n' Slow!! This is most awesome!!
 
Alright Jim! Show em what a real build thread looks like.. Great to see you getting around once again.
 
I got the 29mm motor tube and body tube cut to length. I also cut a 1" piece of body tube to use for sizing the nose cone.

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I cut an inch off the basswood block before re-drilling it. This time I mounted it solidly in a vise. Using a new stubby spade bit without a threaded tip, I successfully drilled the new hole.

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As I said, the hole in the nose cone will be for attaching the forged eyebolt, by embedding it in resin. The faceplate I'm using was just a tiny bit tight. Normally, I would file something like this, but the faceplate is chrome plated, and is too hard for a file. So with it spinning on the lathe, I ground it a little bit with an angle grinder. That did the trick. I also remounted the basswood block to the faceplate.

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I mounted the block on the lathe, and with it spinning very slowly, I advanced the cupped live center into the opposite end. Apparently my bandsaw didn't cut it square, because the tip end was wobbling quite a bit. I'm pretty sure I have enough material to cut it to shape. I started the long process of roughing it round.

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Great to see you back at it Captain :)! The build is coming along nicely. Excellent job on the wood turning!
 
Just like turning a fine pen,great looking nose cone Jim.That will be a great looking Bull Pup!
 
I marked the blank for the 2" shoulder, then cut it with a variety of chisels, and finished it with 60 and 120 grit sandpaper. One of the better shoulders I've cut. Lots of nice curly shavings from this project.

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Now the process of shaping the nose cone begins. I marked it at 12" from the shoulder, but that probably wasn't necessary. A trick that Sandman told me about, and that I've used in the past, is to hold the small nose cone up to the big one, to use as a shaping guide. But the shape of the Estes nose cone that came in the Bullpup kit I have doesn't look right to me. It looks more tapered that ogive.

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Now the process of shaping the nose cone begins. I marked it at 12" from the shoulder, but that probably wasn't necessary. A trick that Sandman told me about, and that I've used in the past, is to hold the small nose cone up to the big one, to use as a shaping guide. But the shape of the Estes nose cone that came in the Bullpup kit I have doesn't look right to me. It looks more tapered that ogive.

A trick for shaping NC's that has worked for me is using a profile drawing and cutting a pattern I can hold up to the blank as I turn it. The profiles can be gotten via pictures that have been blown up to the right scale or from line drawings done the same way. I cut the patterns on either foam board or picture mat board.
 
A trick for shaping NC's that has worked for me is using a profile drawing and cutting a pattern I can hold up to the blank as I turn it. The profiles can be gotten via pictures that have been blown up to the right scale or from line drawings done the same way. I cut the patterns on either foam board or picture mat board.

Funny you should mention that...
 
One of the features of Open Rocket, is the ability to print the nose cone profile. As it turns out, the Estes cone is closer than I thought. I printed it on card stock, then used it as a guide as I slowly shaped the cone. As with cones I've turned before before, final shaping was done with 60 and 120 grit sandpaper. Then finally, I cut the tip off.

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I chiseled the tip a bit, then went to sandpaper. I'm very, very happy with how this turned out! I still need to do final sanding with finer grits to get it paint ready. I got to thinking about it, and this is the first true ogive cone I've turned, and also the longest.

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Sanding basswood on the lathe is a messy business. And yes, Kit, I wore a mask!

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