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Discussion in 'Mid Power Rocketry (MPR)' started by James Duffy, Apr 21, 2017.
Glad you're back at it James, this is a great thread.
We're going to transfer the forward hatch details to the nose cone next. Let's start by taking a look at the tools we'll be using.
The tool on the left is a panel line scriber, used in plastic modeling to refine or add panel line details to plastic models. As one nose cone is just a big hunk of plastic, it is ideal for our purposes. I was once told that it is essentially a dental tool that has been reworked for optimal use for plastic models, and that makes sense to me. It is available at most quality hobby shops (if you still have one), or direct from Squadron.
On the right you'll see a #11 blade and holder, and the tip has been broken off. The back side of the blade will be used after the scriber to refine the shallow trench created by the scribing tool.
More in a bit,
The first panels to be detailed will be the hatches found in quads 1 and 3. Masking tape is used to define where the lines need to go, and pencil lines representing the panel lines are then drawn directly onto the part using the tape as a guide.
With the lines in place a strip of Dymo labelmaker tape is aligned next to a panel line location. The Dymo tape will guide the tool as we scribe the line. Note that this is the old school, thick tape used with a "clicky-clicky" acoustic label maker, not the new electromogrified digital label maker products. It's thick enough to provide a robust guide for the tool, and is great for this application. It can also be peeled up and reused a couple of times.
Three or four passes with the scribing tool should be plenty for each line. If you do it right, you'll end up with long curls of plastic thread emerging from the trench after the last couple of passes.
After the lines are cut with the scriber, and single pass with the back of the X-acto tool will refine the profile of the scribed line, and you'll end up with a part that looks like this...
Note that we're reusing the cone from an earlier project, and that most of the paint from that project has been sanded away. There's still some residual paint left though, which accounts for the funky surface look. That will all go away when we finish sand and prime the cone.
The two remaining quads will be done next, using a different technique. On the actual V-2 vehicles quads 2 & 4 seem to be antenna panels, as evidenced by what appears to be a border of insulating wood. Here's a shot of the V-2 on display at the Imperial War Museum in London:
We are going to simulate this frame with a raised detail cut from .010" styrene sheet. To do that, a printed copy of the quad drawing is attached to a sheet of styrene with clear tape.
Using a fresh #11 blade, the inside frame line is cut first, followed by the outside frame line. The resulting part is a thin, delicate representation of the insulating frame.
Next, tape strips are used to define the lower and side edge positions of the frame on the nose cone. The bottom edge of the frame is carefully attached to the cone by wicking Tamiya thin plastic cement into place with a fine brush. Working in small sections, the remainder of the frame is attached in a similar fashion.
Eventually we end up with an accurately placed insulator frame detail.
I should pause to mention the tape that I am using. Years ago I went down a non-rocketry hobby rabbit hole and began building ukuleles. That nasty little habit is supported by tools and supplies from a company called Stewart-MacDonald, who are essentially the Apogee Components of the lutherie trade. They recently began offering a nifty little desktop tape dispenser, which you can see here. I opted for the version with three tools of vaguely defined "orange tape," which you see here. This stuff isn't masking tape, as it is far too tenacious for that purpose. On the other hand, it is a great all-around utility tape, and the assorted widths are handy.
Where are you getting your Dymo tape these days? I haven't been able to find any for a while now.
I have a stash that is many years old, but it is readily available on Amazon.
Next, sections of the quad drawings will be used to locate the various rivet/bolt/fastener locations found on these panels. The drawing bits are taped into place on the model, and a small awl is used to punch lightly through the paper into the plastic below.
Once all of the locations are marked the paper is removed, and the rivet locations can be lightly drilled with a tiny bit.
Note that we are not drilling through the plastic, just cutting into the top layer. This is the exact same technique used for the large rivet fields found elsewhere on the cone, and documented earlier in this thread.
After the antenna quads are done we can move on to the "barn door" hatch quads.
The hatch details on the #2 antenna quad are next. The large hatch detail is cut using a copy of the drawing as a guide, and the hinge line is scribed into the part.
The hatch is glued into place with Tamiya thin cement, and the three screw details are added.
The small hatch is then cut out and glued into place.
Our next task will be to add the little latch details to the barn door hatches as well as to the access door on one of the antenna panels. These will be fashioned from strip styrene, and it is critical that each little segment be exactly the same length. A tool called the "Chopper" will be pressed into service, which I grabbed 20+ years ago from the railroad section of my local hobby shop. It appears that it still available direct from the manufacturer, Northwest Short Line.
I tend to make many more parts than are needed, as I always seem to screw up a couple. Also, parts tend to go missing in action when they are this small.
The locations for the latch details are added using a section of a quad drawing as a guide.
The parts are positioned and tacked into place with a tiny bit of Tamiya thin cement.
Here's a quick look at the status of a couple of the quad panels after all of the parts are in place. The next step will be to clean up our work, sanding away a few rough spots and taking care of a couple of glue squeeze-outs. I also need to add some sort of detail separating the Bumper transition section (the bit with the fin slots) from the rest of the cone.
A couple of quick updates...
First, I decided that I wanted to locate the rivet line divisions between the hatch quads. Studying several drawings it appears that these divisions have either 23 or 24 rivets. I settled on 23, and whipped up a quick rivet drawing in Illustrator. These drawings were taped into place on the nose cone, and used as a template to punch the rivet locations.
With the rivet locations marked, we do the little trick with the drill bit to enlarge each marking. Here's the result.
Next, a strip of .040" half-round styrene stock is used to define the joint between the warhead/WAC section and the instrumentation section. As the strip is slowly wrapped around the cone Tamiya thin cement is wicked into the joint.
Here's what the joint looks like with the half-round strip in place. There's a great deal of clean-up that needs to take place, such as refining the fin slots for the WAC sustainer.
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