Starship Avalon: build thread

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Because the main BT50 tube extends all the way from nose to tail, there was no MMT centering ring to hook up the Kevlar to. So I was thinking about just putting a 2050 centering ring about 12" down into the tube, and using that. But I'm thinking I'd rather have a bit more of a shelf there, in case I choose to use Estes wadding sheets in this one rather than dog barf (getting dog barf into a BT50 is not fun in my experience). I could imagine the wadding sheets pushing through that hole.

I know Rex R once posted that he uses exactly what I'm describing (a CR with BT20-sized hole) and it serves adequately as a shelf. I'm not sure. Anyone have any good suggestions?
 
...because you only live once.
ImageUploadedByRocketry Forum1500600668.637266.jpg

If I had been thinking I could have used that same stripes pattern on all three triangles, so all sides would look the same. It really disguises the hook.
 
if you want the others to match, you could add similar black stripes: a decal or a sharpie could do the trick to duplicate the appearance of the decal over the engine hook.
 
Dang it, you're right, now I'm gonna have to try that. I have some spare black left over. I don't know if those little pieces will actually stay on long term; hopefully the coat of Future will seal them down a bit.
 
Dang it, you're right, now I'm gonna have to try that. I have some spare black left over. I don't know if those little pieces will actually stay on long term; hopefully the coat of Future will seal them down a bit.

Just bought some Future. Do you just smear it on using a foam brush and leave it? Is it self-leveling? I'm assuming it's like spraying a clear coat and leaves a hard protective "shell"?
 
Yes, yes, and yes. Typically you'll apply it on with a foam brush, position the rocket vertically, and it'll drip off the pointy bits. You'll want to periodically dab the drops off the points, until it stops dripping.

I usually only apply one coat, but some apply several.
 
OK, from the "don't know when to leave well enough alone" school, here's the result of putting a couple of thin strips of black over the green triangle, to make it match the side with the hook.
ImageUploadedByRocketry Forum1500849890.283151.jpg

Looks good from a distance. Definitely makes the three sides look the same now. Dunno if those little strips will hold forever, but should for a while at least.

Next, I had mixed some epoxy for a non-rocketry related job, so it occurred to me to put together the balsa nose block that'll be used for the base of the nose section. I decided to use a technique suggested by Micromeister, because it sounded fun. I drilled a hole into one end by first screwing in a screw, then enlarging the hole with a drill bit (stuck in and turned by hand). Then I dropped in a loop of Kevlar and filled in the hole with epoxy, also applying a nice layer to the whole end to harden it up.

Result looks good. This will provide one attachment point for the shock cord. Still need to implement the other end.
ImageUploadedByRocketry Forum1500849903.462339.jpg
 
Yes, yes, and yes. Typically you'll apply it on with a foam brush, position the rocket vertically, and it'll drip off the pointy bits. You'll want to periodically dab the drops off the points, until it stops dripping.

I usually only apply one coat, but some apply several.

Thanks for the info on the technique!
 
Hello Neil,
I just wanted to say Amazing Build!
I really dig the design. Going through your build thread with much interest. Cannot wait for the flight pics/vids.
Thx for sharing.
 
Hello Neil,
I just wanted to say Amazing Build!
I really dig the design. Going through your build thread with much interest. Cannot wait for the flight pics/vids.
Thx for sharing.

Thanks. Sadly I'm still not actually finished with this thing.

Tonight I glued the nose block into the nose section with TBII. Prior do doing so, I black Sharpied around the block approximately where the block would be inserted to; easier to do it now than after it's installed. And here it is.

Who would have guessed the most exciting build steps were going to come at the very end? :rolleyes:

By the way, the Kevlar loop epoxied into the nose block looks and feels great. Incredibly solid, and knowing how it's fastened in there I can't imagine any circumstances when it would ever come out, short of complete destruction of the nose section. Thumbs up on this technique.
ImageUploadedByRocketry Forum1502066292.376895.jpg
 
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Shock cord installation was a bit of a comedy.

I decided to anchor the Kevlar on a 20/50 centering ring. The trick is that I needed to push it way far down into the body, from the top end.

First, I filed a notch in the edge and glued in the piece of Kevlar (with a knot at the end). This was just to hold it together while I push it into the tube.
ImageUploadedByRocketry Forum1502225685.833820.jpg

Then I started to scratch my head figuring out how to get it installed.

I decided that I wanted to push the ring into position from behind, so it would form a natural fillet in front of the ring, in the direction the cord will be pulling it. So I pushed the ring all the way in, past where it needed to be (approximately underneath the front transition). From the front, I pushed with a piece of 3/4" PVC, which worked perfectly. Then I did a practice run pushing from the back. Uh oh. To work around the engine block, I needed to use a smaller-diameter pusher; I grabbed a 3/4" (or maybe 5/8", something like that) dowel. But then I couldn't push the whole ring at once; I'd have to push one edge at a time. This made it very easy to dislodge the ring and leave it cockeyed in the tube. I decided to try it anyway.

I applied epoxy (the inside of the BT was CA-coated, so I wasn't gonna use wood glue here) in a ring inside the tube, in the approximate correct position. I used a long 3/16" dowel, and trying to avoid touching the epoxy blob to the BT while threading the dowel down into the tube was like playing Operation. I eventually got what seemed to be a decent ring of glue there. Now to push the ring into place.

I got my dowel and pushed from behind, working around the edges of the ring. Doing this all by feel was incredibly difficult; so much so that I quickly dislodged the ring again, just like in practice, so it was now sitting at an angle. I could look in the end with a flashlight and see a bit of what was going on in there, fortunately. So then I took my small dowel and slowly pushed on the nearest parts of the ring until it seemed to be lodged symmetrically in the tube. This took a while. Then I looked in the other end with a flashlight to try to make some determination if I had probably landed the ring in the epoxy. I thought I saw some epoxy blobbed up around the edge of the ring, so I assumed I had landed in the correct spot.

Finally I attempted to add a little more epoxy around the perimeter as a fillet. I honestly have no idea if that helped (when working more than 10" away from the end of the tube, it is not easy.)

In the end, I think it's OK. When fully cured I'll test the strength a bit and make sure it stays put.

So it's probably successful but not one of my most well-thought-out bits of building. If I had anchored the cord to a short piece of coupler (or even stacked two centering rings), I could have at least made it so it would stay lodged properly in the BT. That would have saved a *lot* of effort.

Oh well, down to the very end. I also Futured the whole rocket, so the only step remaining is to attache the elastic shock cord and hook on the parachute.
 
Shock cord installation was a bit of a comedy.

I decided to anchor the Kevlar on a 20/50 centering ring. The trick is that I needed to push it way far down into the body, from the top end.

First, I filed a notch in the edge and glued in the piece of Kevlar (with a knot at the end). This was just to hold it together while I push it into the tube.
View attachment 325293

Then I started to scratch my head figuring out how to get it installed.

I decided that I wanted to push the ring into position from behind, so it would form a natural fillet in front of the ring, in the direction the cord will be pulling it. So I pushed the ring all the way in, past where it needed to be (approximately underneath the front transition). From the front, I pushed with a piece of 3/4" PVC, which worked perfectly. Then I did a practice run pushing from the back. Uh oh. To work around the engine block, I needed to use a smaller-diameter pusher; I grabbed a 3/4" (or maybe 5/8", something like that) dowel. But then I couldn't push the whole ring at once; I'd have to push one edge at a time. This made it very easy to dislodge the ring and leave it cockeyed in the tube. I decided to try it anyway.

I applied epoxy (the inside of the BT was CA-coated, so I wasn't gonna use wood glue here) in a ring inside the tube, in the approximate correct position. I used a long 3/16" dowel, and trying to avoid touching the epoxy blob to the BT while threading the dowel down into the tube was like playing Operation. I eventually got what seemed to be a decent ring of glue there. Now to push the ring into place.

I got my dowel and pushed from behind, working around the edges of the ring. Doing this all by feel was incredibly difficult; so much so that I quickly dislodged the ring again, just like in practice, so it was now sitting at an angle. I could look in the end with a flashlight and see a bit of what was going on in there, fortunately. So then I took my small dowel and slowly pushed on the nearest parts of the ring until it seemed to be lodged symmetrically in the tube. This took a while. Then I looked in the other end with a flashlight to try to make some determination if I had probably landed the ring in the epoxy. I thought I saw some epoxy blobbed up around the edge of the ring, so I assumed I had landed in the correct spot.

Finally I attempted to add a little more epoxy around the perimeter as a fillet. I honestly have no idea if that helped (when working more than 10" away from the end of the tube, it is not easy.)

In the end, I think it's OK. When fully cured I'll test the strength a bit and make sure it stays put.

So it's probably successful but not one of my most well-thought-out bits of building. If I had anchored the cord to a short piece of coupler (or even stacked two centering rings), I could have at least made it so it would stay lodged properly in the BT. That would have saved a *lot* of effort.

Oh well, down to the very end. I also Futured the whole rocket, so the only step remaining is to attache the elastic shock cord and hook on the parachute.

I have to ask: was there a reason you didn't just attach this to the MMT and do it when it was outside the tube? Seems like it might have been easier!! ;^)
 
I have to ask: was there a reason you didn't just attach this to the MMT and do it when it was outside the tube? Seems like it might have been easier!! ;^)
Two reasons:
1) There is no motor mount. The stuffer tube is BT50 all the way, and I left it for 24mm motors. So the only thing I have in there is an engine block. I *could* have anchored the Kevlar to the engine block, but...
2) ... I was originally thinking of putting one of Qualman's baffles in. In that case, the Kevlar would anchor to the baffle. I ultimately decided against that (for various reasons), so I needed to provide my own shock cord anchor in there.

No doubt, if I had done this all before I put the engine block in (like right at the beginning) it would have been *much* easier, but I just didn't know what I wanted to do yet.
 
Two reasons:
1) There is no motor mount. The stuffer tube is BT50 all the way, and I left it for 24mm motors. So the only thing I have in there is an engine block. I *could* have anchored the Kevlar to the engine block, but...
2) ... I was originally thinking of putting one of Qualman's baffles in. In that case, the Kevlar would anchor to the baffle. I ultimately decided against that (for various reasons), so I needed to provide my own shock cord anchor in there.

No doubt, if I had done this all before I put the engine block in (like right at the beginning) it would have been *much* easier, but I just didn't know what I wanted to do yet.

Just wondering if it would've been easier to mount the CR and Kevlar closer to the open end of the body tube, in the same position as the old Estes shock cords used to be? Much more accessible and visible? (Forgive my BAR ignorance but the last time I mounted a shock cord it was with the trifold paper mount, and to be honest I still haven't figured out why it changed to anchoring it on the motor mount).
 
Teabag mounts generally do work fine. I believe there are two advantages to attaching the shock to something down towards the rear of the rocket (folks can correct me if I get this wrong):
1) Eliminate protrusions on the interior of the BT that could hang up on the chute during ejection. With the shock cord anchored down towards the rear, there's nothing but smooth tube up top where the chute must slide out
2) It also makes it more natural to pack the shock cord below the parachute, since the cord "starts" at the back. You get a nice clean stack that way: wadding, shock cord, parachute, nose cone.

That being said, I've been thinking that in the event of a break in the Kevlar, the most likely repair would be to just put in a teabag mount. Been meaning to ask about this somewhere.
 
Teabag mounts generally do work fine. I believe there are two advantages to attaching the shock to something down towards the rear of the rocket (folks can correct me if I get this wrong):
1) Eliminate protrusions on the interior of the BT that could hang up on the chute during ejection. With the shock cord anchored down towards the rear, there's nothing but smooth tube up top where the chute must slide out
2) It also makes it more natural to pack the shock cord below the parachute, since the cord "starts" at the back. You get a nice clean stack that way: wadding, shock cord, parachute, nose cone.

That being said, I've been thinking that in the event of a break in the Kevlar, the most likely repair would be to just put in a teabag mount. Been meaning to ask about this somewhere.

Thanks Neil, makes a ton of sense to me now.
 
The shock cord comedy continues.

I looked in, and it seems like the ring with the Kevlar is pretty well anchored in there. Great! So the next standard step is to pull the Kevlar out the front of the BT, and Sharpie-mark a spot just below the end of the tube. This will mark the end of the loop I tie in it, so the Kevlar will always stay below the edge of the BT and not cause a zipper. Standard stuff.

After the Kevlar is marked, I pull it out the back so I can tie the loop. So I did that, and this is what greeted me:
ImageUploadedByRocketry Forum1502411604.032573.jpg

In other words, I seem to have managed to install the shock cord anchor at almost the exact centerpoint of the rocket. Which means location where I need to tie the Kevlar loop is inside the BT. :facepalm: On a 3" tube that might not be so bad, but this is a freaking BT50 we're talking about.

At this point I decided to put it down and think about it for a while. I am not confident that I could tie a good knot with two pairs of tweezers, although I might have to give that a try. Anyone else have an idea?
 
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Tie a loop knot outside the tube and use the tweezers or a toothpick to roll-slide the knot down to your correct location is how I'd be approaching it...
 
I guess I'll have to try that. In general, I'll just need to see what I can do with tweezers in there. Maybe it won't be so bad. Still, incredibly annoying to have made such a stupid mistake...
 
Can you keep the long Kevlar and add a zipper-proof wrap around it at the body tube lip?
 
Slide a length of shrink tubing over the kevlar portion where it exits the BT to protect it. I've seen this done when using low- and mid-power engines. Thicker tubing from model airplane fuel lines can also be used. A low tech approach is to fold a few wraps of masking tape over the area that touches the BT edge.
 
Or duck-tape a small piece of pillow foam to the cord where it exits the tube. About time to light the candle under this puppy, don't 'cha think ? :)
 
Can you keep the long Kevlar and add a zipper-proof wrap around it at the body tube lip?

Slide a length of shrink tubing over the kevlar portion where it exits the BT to protect it. I've seen this done when using low- and mid-power engines. Thicker tubing from model airplane fuel lines can also be used. A low tech approach is to fold a few wraps of masking tape over the area that touches the BT edge.

I will probably have to resort to this approach if I can't get the knot positioned correctly, but it is not my first choice.
 
OK, tying a knot inside the BT ain't-a-gonna happen. Tried futzing around with tweezers for a while and no effin way. Eventually I gave up and ended up with this:
ImageUploadedByRocketry Forum1502579441.114572.jpg

I believe that is the technique I have seen described before, though it's my first time using it. Not pleased about this but what can I do.

The rest of the shockcord (just visible at the bottom of the pic) is the last of my supply of Odd'l flameproofed 1/8" elastic, gotta resupply that.

Anyone have a good technique for stuffing shock cord into a BT50? What a pain.
 
...Anyone have a good technique for stuffing shock cord into a BT50?...

try over-under coiling the cord around a pencil, then stuff the coil into the tube. Start wrapping the cord near the nose cone, then you can just slide the coil off the pencil into the tube. I have used this technique for 13mm tubes with the thin round shock cord, should work for flat cords also. Over-under coil wrapping is one of those things, that once you learn how, you use it for anything, extension cords, shielded video cables, mic/guitar cables, water hoses, shock cords... Google search it for a how-to. It is not a matter of grasping how, but rather of how you grasp :)
 
try over-under coiling the cord around a pencil, then stuff the coil into the tube. Start wrapping the cord near the nose cone, then you can just slide the coil off the pencil into the tube. I have used this technique for 13mm tubes with the thin round shock cord, should work for flat cords also. Over-under coil wrapping is one of those things, that once you learn how, you use it for anything, extension cords, shielded video cables, mic/guitar cables, water hoses, shock cords... Google search it for a how-to. It is not a matter of grasping how, but rather of how you grasp :)

An IT guy at my company once taught me this, but I quickly forgot the technique. Just looked at a Youtube video and now I remember. That's a good idea for shock-cord wrapping, but I'll have to see if I can actually figure out how to do it with a pencil and with both ends of the cord connected to stuff. Knowing in advance that it is definitely possible should enable me to figure it out.

I think once I tried wrapping around a pencil but didn't do the over-under, and it ended up a bit of a mess....
 
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