Diamond Cutter build thread

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neil_w

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And so I finally pulled this one out of the virtual build pile, the most overthought design in (my) history. Actually it's my first scratch build ever, hence the excessive head-scratching and hand-wringing. I'm not used to thinking about some of these things, and it hurts my brain. In a good way.

If you're looking for a nice neat build thread that will end sometime this decade you're in the wrong place, this might take a while.

Here's the final OpenRocket file for this design. In this case, "final" means "still likely to change at any time". Unfortunately, this forum limits the allowable size of uploaded ORK files, so I had to remove the decals from this version.

View attachment diamond_cutter_upload.ork

Let's see what's in the package:
dc_parts.jpg

What's that you ask? Oh yes, I *did*. This is what happens when you spend (way) too much time stuck at the computer instead of at the workbench, so let that be a lesson to you kids:
dc_facecard.png

Frankly, I was so happy with the way that came out that I almost decided to quit while I was ahead and declare victory, but since I had already purchased the parts I figured I might as well proceed.

This rocket really isn't very complicated, but there will be a few tasks along the way that I expect to be a little tricky, finishing being tops among them. Sequencing will be important, and I've chosen (for now) just the sorts of paints to torture me: black metallic, silver metallic, and fluorescent green. Yay.

One last note before we begin: I am highly uncertain of the finish design of this rocket. I think it looks OK, but I don't know if the name should be there, or if something better could be done with the decals on the fins, or what. I do like the color scheme, odd as it is. Anyway, I'm wide open to suggestions as we go.


First bits of build will dribble out over the next week or so.
 
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LOL!!!!!

That is hilarious. Way too much time on your hands. (I say this as I'm reading TRF at work.)
 
Build thread on hold until I can post pictures again. I have already made my first build mistake, but it's a minor one and easily fixable.

In the meantime: LET'S GO METS!!!
 
Well, the pictures are back, so let's get to it. Here is the side view, as shown in OpenRocket:
dc_sideview.png

The transitions are each shown as two pieces (because that's the only way to do it in OR), but in fact each one is a single piece of balsa, custom turned for me by Sandman. We'll get to those guys later.

As with my previous build thread, I'll spend plenty of time on steps that may be old hat to many folks around here. But if they're new to me and/or present any particular challenge, I'll walk through it here, because maybe someone else out there will encounter the same issues.

First step was to cut the body tubes. I needed three pieces of BT-60 and one piece of BT-50 for the motor mount/stuffer tube. Having never cut a body tube in my life (that I can remember, anyway), I went the cheap and simple route and picked up the Estes body tube cutting guides:
small-Estes-Cutting-Guides.jpg
These are very straightforward: each ring (one for each standard Estes BT size) consists of two pieces. First you slide one of the pieces into position, and then slide the other piece into place to clamp the ring tightly on the BT. Then cut around the tube as shown in the picture above. The theory is to (try to) hold the blade in one place, applying light pressure, and then rotate the tube until eventually the tube is cut. In practice, I had a few issues. First, it takes a bit of practice to hold the blade properly against the guide at the correct angle with one hand while turning the tube with the other. I shaved off a bit of the yellow plastic on several occasions as the blade angle and pressure drifted a bit. More troublesome was the point where the tube was almost cut through (this was after *many* turns). It wasn't a matter of just merrily turning and then on the last turn it cleanly finished the cut all the way around. Some parts of the tube cut through before others, and I had to repeatedly push the blade in in some parts and pull it out in others when it would get stuck in a hole. I got better with practice but I'm still not really satisfied. A fixture that holds the blade in place (like the Kuhn tube cutter) seems like a better solution, but I'll probably keep trying with what I have.

Had I stopped and thought for a moment I would have realized that there are Youtube videos that show how to do this, includine a video from Apogee showing specifically how to use the Estes cutters (is there any technique they *don't* have a video about?). I haven't watched them yet because I don't want to find out what an idiot I am for doing it wrong until after this build is done, thank you very much.

One other issue: perhaps this is an artifact of the particular tubes I'm using, but the cutting guides actually left marks in one of the tubes where they clamp down:
tube_marks.jpg
I'm sure I could have filled them with CWF, but fortunately this only seemed to happen on one of the smaller pieces, so I designated it as scrap and cut another.

I CA'ed the ends of each tube and sanded them down smooth(ish). Here's the two-inch tail piece, still in need of more sanding:
tail_tube.jpg

Somewhat later on, it occurred to me that I'm gonna need to glue stuff to the ends of some of those tubes; either balsa transitions or in spot shown in the above pic, the aftmost centering ring. I think the transitions will extend well beyond the CA area and will still have plenty of raw tube surface to use Titebond, but for the centering ring I'll probably have to go with epoxy. No biggie. I'm not sure it would be practical to sand the ends of the tube *without* applying the CA first, so I don't really know what a good alternative would be.

Here are the finished tubes.
all_tubes.jpg
 
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I thought long and hard, and then some more, about how to sequence the assembly of the motor mount/stuffer tube. I finally figured it out, and it seems to have worked OK.

First I prepared an engine hook (I am not allergic to them) by cutting off the finger tab (I am not allergic to them either, but all the cool kids are cutting them off so I figured I would as well). I'm using an E-length hook, so I should have pretty good flexibility in engine choice.

The curvy end (where the finger tab was removed) was inserted into a slot in the tube and secured with foil tape:
ImageUploadedByRocketry Forum1446471084.177643.jpg

Next I added the necessary slots to the two plywood rear centering rings. I found that the edge of a file was the perfect instrument for this. I test-fitted the aft ring and put a motor in, just to ensure that the hook slot was deep enough in the ring to allow motor insertion and removal. Looks good:
ImageUploadedByRocketry Forum1446471105.217040.jpg

I then glued the ring with Titebond, and realized that for all my thinking about the sequence I still made a mistake, as I now had no way to get the second ring over the foil tape. So off came the tape, and on went the second ring, and a new wrap of tape was applied:
ImageUploadedByRocketry Forum1446471162.700147.jpg

Next I glued on the aft piece of body tube with epoxy:
ImageUploadedByRocketry Forum1446471202.164464.jpg

Finally, I glued in the rear transition. As I mentioned above, Sandman made the transitions for me. The rear transition is drilled for the motor mount tube, with (fortunately) a little extra room in it so it fits snugly but comfortably over the tape and the ring. The walls in the narrowest point of the transition are very thin, so I handled it carefully, but when there's a tube inside it it's pretty safe. I applied CWF to the transition, sanded it, and then it was ready to be glued in:
ImageUploadedByRocketry Forum1446471244.200515.jpg

Afterwards I wondered if I should have put some fillets on the joint between the second ring and the BT, but I decided that it didn't really matter; with a total of four centering rings it should all hold fine, and besides I'll be able to fillet the rear ring (which is why it's recessed a bit). I'm not concerned.

Progress!
 
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Very nice. I really like that you did 'packaging' for it. Very cute. ;-)

I'll be following along for sure.

This thread could have an equal home in the 'Scratch Built' forum; can threads live in two places?

Have fun!!!
 
Thanks.

I wasn't sure whether to put it here or in the scratch-build forum, to be honest. I don't generally read that forum so it felt odd putting it there. Pretty certain a thread can't live in both places, and I can't move it myself. If anyone thinks this should really be in the other forum I can certainly ask a mod to move it. I guess I'd ultimately want it to be in the place where it will get the most views. :)

In general I feel like there are too many overlapping forums, I don't know why things have to be subdivided so finely (this applies to others as well, not just TRF).
 
I wasn't sure whether to put it here or in the scratch-build forum, to be honest. I don't generally read that forum so it felt odd putting it there.

Putting it here meant that I saw it. :) I might have seen it in Scratch Built eventually. But not very soon. So I concur with your thinking.

Wes
 
Brief aside: how awesome is this ridiculous font (found on 1001freefonts.com) for this rocket? Click to see it in glorious largeness:
dc_great_font.png

Sadly, I don't think there is any cost-effective way to do this as a one-off. Getting a single sheet printed commercially is way too expensive, and I gather that I would not do well trying to print my own light green to show on top of black. Don't believe Stickershock23 could cut vinyl for something this crazy.

I am assuming that if I want any name printed on this rocket at all, it'll have to be a "reasonable" font, cut from vinyl by Stickershock23. But we'll see.
 
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A quote, from Stickershock23:

TELL ME THE FONT YOU WOULD LIKE HERE.
USE ONE FROM OUR FONT LIST OR MOST ANY FREE DOWNLOADABLE FONT FROM THE NET!(1001free fonts.com is awesome for this)
Please enter the fonts FULL name and where you found it if you can.


Since Mark uses 1001freefonts.com, it looks like you are good to go. Mark does good work!
 
Fortunately, I eventually remembered that I hadn't yet glued in the thrust ring. I applied Titebond inside the engine tube with a chopstick (mounting point for the ring was about 5 inches into the tube, so it was a fairly long-distance glue application.) I then inserted a dummy motor into the mount, and pushed the ring into the opposite end with a long 7/8" dowel (which I use to make display stands, but that's for another thread). The dummy motor was there just to make absolutely sure that the ring went in square; with the ring sandwiched between the dowel on one end and the motor on the other, it *had* to be straight. Once it was in place, I immediately removed the dummy motor so it couldn't get inadvertently glued in. No pictures of this process because i only have 2 hands. :confused2:

Next came the final two centering rings. I installed the first ring flush to the end of the transition (in fact I glued it to the transition, in addition to the motor tube). The reason it's there at all is because I don't want to rely on the structural rigidity of the transition; it will undoubtedly contribute a bit of strength to the completed assembly, but we shouldn't depend on it. The extra ring should carry the load. Here it is, glued to the transition:
ImageUploadedByRocketry Forum1446517565.751028.jpg

I put a small notch in the edge of the final ring with a small round file (to accommodate a Kevlar cord) and then glued it a millimeter or two off the end of the tube, just enough space for a fillet. Maybe not necessary but what the heck. Here's the final assembly:
ImageUploadedByRocketry Forum1446517578.826550.jpg

I can only guess if I have an appropriate length of tube there to provide sufficient rigidity to the final tube assembly. The centering rings are about 3 inches apart. It seems like plenty; we'll find out when it flies, one day. :p

So far so good. The more interesting parts of the build are coming up...
 
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Maybe I don't understand the process (actually, there's no maybe about it; I definitely do *not* understand it) but I don't see how it's possible to cut all the little fine crap in that font. If you can explain it, please PM me; I'm quite interested but don't want to fill up too much of this thread with that discussion.
 
Maybe I don't understand the process (actually, there's no maybe about it; I definitely do *not* understand it) but I don't see how it's possible to cut all the little fine crap in that font. If you can explain it, please PM me; I'm quite interested but don't want to fill up too much of this thread with that discussion.

Mark starts out with a full piece of "Alien Green" vinyl. He then cuts away everything not needed leaving the little pieces (diamond shapes) you mention in your font. It really is no different than leaving a dot on an "i" in any other font.
 
Ya I'm sure they can do it. If not let me know and I can probably help you out next time I'm cutting some stencils(in a week or two). You should consider cutting a vinyl 'stencil' instead of a sticker. My first exploit into vinyl cutting was to cut a mask for one of my models. I tried to take a picture but the camera battery is refusing me. Anyway - it's really easy to use a vinyl cut mask and then use the same paint that you are using for the rest of your trim.
 
Here's a picture of a Vinyl / Electronic Plot Cutter. They can do remarkably fine work. Practically speaking they can do finer work than the vinyl can stand; that is they can cut vinyl into parts so thin/small that you can't manipulate them any more. Pretty cool things.

Roland-Vinyl.jpg

They all come with software that can convert pretty much any image into a cut path. But you can also put together images for it, e.g. by using your custom font.

Some of these are crap and will only allow you cut cut patterns that you have to buy; yes we're looking at you Cricut! :(

But ones like in the image above are pretty much just a Plot cutter only limited by the width of their feed and the thickness of material that they will cut. In our local FabLab people are cutting paper, card stock and some cloths too.
 
Thanks, that's good background info. How exactly does the machine "remove" the unwanted bits?

While we're killing time here, waiting for more building, here are two candidate fonts, please cast your votes:
dc_fonts.png

Placement of the name in #1 should probably be a bit higher, don't let that sway you.

[update] Mark says he can make font #1 work. So it's definitely an option, if it's the winner. Live and learn!
 
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Thanks, that's good background info. How exactly does the machine "remove" the unwanted bits?

Ah, yes... the machined doesn't. You get out your fine tipped tweezers and do it yourself.

Wes
 
I keep forgetting to ask... are you planning on posting your source files for the 'packaging' card? Or just sharing how you do it?

I use a lot of image editing solutions so I'm always keen to see other peoples tricks.

Wes
 
I keep forgetting to ask... are you planning on posting your source files for the 'packaging' card? Or just sharing how you do it?

I use a lot of image editing solutions so I'm always keen to see other peoples tricks.

I put the Paint.net file on DropBox: https://www.dropbox.com/s/qrrl7e5iuqfddih/dc_facecard.pdn?dl=0.

A super short explanation is: I use Paint.net. I put an image of an Estes face card next to me and recreated it, piece by piece, keeping stuff on separate layers as much as possible. A few pieces I actually cut and pasted from the Estes artwork (e.g., the picture of the rocket with the altitude estimates, although I replaced the altitude numbers with my OR sim values). Some aspects of the Estes artwork I either skipped or did a bad job of, which is easy to see if you look at my image next to a real one, but the overall effect is "good enough". The rocket image was screen-shotted from OpenRocket, once I had the size and positioning tweaked just the way I wanted. I can answer any more detailed questions as desired.

In the meantime, I am feeling drunk with power:
dc_stripes.png

I like it a lot, but I need to control myself or I'm gonna end up doubling the cost of this thing just on decals.... (also, I should note that fitting the stripes precisely between the fins at the back would probably be fun, where by "fun" I mean "not fun at all".)
 
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I was really excited when I saw your thumbnail... in the thumbnail the 'stripes' appear to be diagonal from the length line. But in the actual version they are 'around' the body perpendicular to the length line. I wonder if you could explore some diagonals.

Don't worry; Us twonks on here will keep you busy. You might finish it this decade. :)

Wes
 
I'll try out the diagonals when I have a chance... what I like about the scheme with the "rings" is that they appear to emanate out from the glowing green areas. Diagonal will have a different, spiral effect. We'll see.
 
While my crazy paint planning continues in parallel, let's get back to building.

I tied the Kevlar around the motor mount tube and ran it through the notch at the edge of the forward centering ring. I buried the loop around the tube in a good fillet of Titebond II, so it'll stay put. I tied about 5' of 1/4" elastic to the end of the Kevlar. As always, the Kevlar ends about 1/2" before the end of the body tube, to prevent zippering. Here's the *really* completed motor mount:
ImageUploadedByRocketry Forum1446774340.764720.jpg

Next it was glued into the main BT with epoxy. I first spread a ring of epoxy about 3" from the end of the tube, then inserted the motor mount about 2" in, then put more epoxy on the last 1/2" or so of tube, and slid the whole thing together. My impression was that the whole thing was pretty darn solid when finished. I took a peek into the end of of the BT with a flashlight, and I could see a little natural fillet of epoxy around the forward centering ring where it had squeeged the epoxy off the walls of the tube. I didn't feel a need to add any more. This was my first time using epoxy for the motor mount, and I have to say I quite liked it.

Here's what the transition looked like, connected to both tubes:
ImageUploadedByRocketry Forum1446774356.253577.jpg

As I had expected, the seams between the transition and the tubes needed work. So a layer of CWF was applied to those areas and squeezed off with a razor blade, resulting in this:
ImageUploadedByRocketry Forum1446774372.875299.jpg

After I sanded it, the seams were definitely better, but the new CWF did not blend so well with the old CWF, so I put another whole (thin) coat of CWF on the transition, and after sanding, I had what I wanted:
ImageUploadedByRocketry Forum1446774385.785981.jpg
(Actually, that's a lie: I filled in a few more pits with CWF and *then* it was done.)

Finally:
ImageUploadedByRocketry Forum1446774398.385427.jpg

This piece is now ready for filler/primer, which I will hopefully get a chance to do before too long. In the meantime there are other tasks awaiting.

I am very pleased so far. That was a good bit of work just to put a dimple in the body tube, but hopefully it'll all be worth it in the end. I'm especially happy that my sequencing has worked out OK, given the amount of over-thought put into it. It's quite a different experience working all this out yourself, vs. just following the instructions in a kit.
 
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I like this. The hourglass transition mirrored by the fin shape is a really cool touch. Facecard is a nice touch, too. Maybe you can license the design (kit and graphics) to Estes.
 
Ha, they'd be welcome to it, though somehow I imagine that ain't gonna happen. I would be interested to see how the transitions would be implemented in a commercial kit, because the balsa transitions I'm using are fine for a one-off but probably not suitable for mass production.

Anyway, let's see how this thing looks when it's done. There's a lot of finishing work to do here that I am quite capable of butchering....
 
I decided to CA the nose cone next, following K'Tesh's tutorial (I had never done this before, and approached I t with some trepidation.) It did not go particularly well.

First I got a good coat of CA onto the cone. This actually seemed incredibly easy. So far so good:
ImageUploadedByRocketry Forum1447041075.571581.jpg

Then I black Sharpied the whole thing:
ImageUploadedByRocketry Forum1447041088.905307.jpg

Then I attempted to sand off the sharpie, and here's where things started to go south. No matter how much I sanded, lots of black spots remained. In my final push to sand through the black, I pretty much removed all the CA from the cone, and there was *still* lots of black. Apparently there were some deep pits in the balsa. (Sorry, no pic of this stage, I was frustrated and forgot to take one.)

Also, I did not at all enjoy sanding the black sharpie, for what it's worth.

Anyway, nothing to do but apply another coat of CA. I figured I had at least filled in some holes the first time. So on went the CA, until it looked like this:
ImageUploadedByRocketry Forum1447041099.010996.jpg

This time I dispensed with the sharpie and just went at it with sandpaper. It sanded very strangely; I could not seem to achieve a consistently smooth finish. Eventually, afraid of taking off all the CA again, I just gave up and cried uncle. The final result looks like this:
ImageUploadedByRocketry Forum1447041109.688847.jpg

It is definitely darker and glossier than the raw balsa, so I know there's CA on there, and it is smoothish. I'll find out how good a surface it is when I prime. I feel like there's not much more I can do at this point other than hope for the best.
 
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My instinct would be to get an other NC ordered just in case. ;-)
 
Since it's a standard part, and it won't be glued in (payload section access), I can replace any time I want in the future. I'll only know after I paint, which is still a while in the future. I think it'll be *ok*, if not perfect.
 
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