USS Greenling (SSN-614) Scratchbuild

[wlambing]

Re: USS Greenling (SSN-614) Scratchbuild

Howdy!

Very nice work, indeed! Just a couple of things;

a) Mushroom anchor needs to be flattened a bit. They weren't balls, but more like you took a ball, cut it into four slices, threw the 2 middle ones away, and used one of the ends. The left over one would be a spare! Also, they had a shallow dimple at the center of their bottom (outboard) end.

b) The "Dunce cap", or propeller nut cover, now in red, should be the same color as the screw. Once fully assembled onto the shaft, the screw, nut, and cap were pretty much a single entity.

c) Zincs are raised off the hull surface. Check out Racer's thread on the 637 he's doing by 'puter. I believe there's a picture or two of zincs in there. Zincs are sacrificial anodes, protecting the hull steel and bronze screw from the effects of galvanic corrosion. All subs have them in some form or fashion. The zincs get eaten up before the bronze and then the steel. They have to be changed out every so many years.

Keep up the nice work!!!!!!!!!

B^)

[salmon]

Re: USS Greenling (SSN-614) Scratchbuild

The zincs are blocks of zinc that are also called sacraficial anodes. Metals placed in salt water begin to flow a small amount of current and corrosion happens (galvanic corrosion). The zincs are used to inhibit more valuable/important metals from getting attacked or slow down the corrosion, the zinc bars are sacrificed instead.
Here is a link that has plans for the bars http://www.wbdg.org/ccb/FEDMIL/a18001k.pdf
Peace,
Tom

[tom dougherty]

Re: USS Greenling (SSN-614) Scratchbuild

Zinc anodes are placed near the propeller area primarily to "spare" the propeller bronze from being degraded and pitted (increasing turbulence and emitted sound) over time by seawater. Many of the ions contained in seawater have very high reduction potentials. The seawater will set up an electrochemical reaction that will degrade the bronze unless another metal (more easily oxidized) is nearby. As we learned from our Moms, the electrochemical potential difference between bronze and zinc in 2% saltwater is 630 millivolts, with zinc as the anode. So zinc is much more readily degraded in seawater and spares the bronze. The zinc anode bars degrade over time and are replaced periodically.

Here is a diagram of the Permit class zincs:

The starboard lower zinc is somewhat shorter than the starboard upper zinc, to accomodate the mushroom anchor).

And a photo of one of the zincs (the dull white horizontal strip between the upper rudder and port sternplane) on a 688][/url]

Now, who wants to derive the Nernst Equation to demonstrate the two half cell electrochemical reactions??

[rdutnell]

Re: USS Greenling (SSN-614) Scratchbuild

Awesome Tom! You told me everything I need to know and more.

[rdutnell]

Re: USS Greenling (SSN-614) Scratchbuild

Wow! A lot of feed back in a short time. COOL!! Sorry wlambing and salmon, I saw Tom’s post but I didn’t realize there were more. Thanks tons!! Anti-corrosion it is!

wlambing:
a) Thanks for the advice on the mushroom anchor. I’ll definitely be changing that and reposting it for comments.
b) Thanks for that info on the “Dunce cap” color. I thought it was black. I’m considering making the propeller out of metal, so I guess if I do I will do the Dunce cap out of metal too.
c) I will definitely look for Racer’s 637 thread.

Salmon:
Thanks for the plans. I see that there are several varieties. I’m guessing that the ones shown in Figure 6A on page 20 are the ones that would have been used on Greenling. I guess the bars shown in the shot Tom posted are a series of these bad boys all lined up. If that’s the case, it should be fairly easy to replicate.

Tom:
Thanks again for the pic and info. And no thanks on the derivation. I think I’ve done enough derivations thank you very much. )

I was about to post what I came up with based on Tom’s pic and the plans, but I think I’m going to change it based on the plans salmon sent.
Thanks again guys, I really appreciate the input.

[rdutnell]

Re: USS Greenling (SSN-614) Scratchbuild

UPDATE 10
After receiving all of the great input from you guys, I had another go at the Mushroom Anchor and Zincs. For the mushroom anchor I used a larger diameter sphere and moved it in more. I then subtracted a smaller sphere from it to create the “dimple”. For the zincs I made a single 0.01” thick bar, with a width of 0.0564”. This is wider than 0.0417”, which would be 6” at this scale, but it agrees well with the plans. Every 0.0833”, I cut 0.002” wide, 0.002” deep notches in the top and sides to delineate the individual slabs. I then mirrored this around to all four sides and sliced the one by the mushroom anchor.

All in all, I think it looks pretty good.




What do you guys think?
The red noticeable in the last image is the location for the “Access to Free Flood Area”. Since this is a hatch, I’m just going to etch a 0.01” x 0.01” groove on the outline, which appears to be almost an oval.
Well, as it turns out I went ahead and did the access hatch before finishing this post, so here are a couple of more goodies. FYI the access hatch as shown is 0.1462”, or 1.75’, which seems reasonable for a small access hatch and it matches the plans nicely too.


Next is the MBT no. 7 valve. Time for more research!

CHEERS!!!

[rdutnell]

Re: USS Greenling (SSN-614) Scratchbuild

UPDATE 11
Well, it’s been an interesting couple of days. First, as I was looking into the MBTs I talked to my buddy and he said that he should be able to do them for me in steel or brass, but that they are pretty busy right now. I’m not in any hurry so I changed my thinking on how I want to do the MBTs and I’m going to do them in whatever metal he can do them in. So for MBT No. 7 I simply created concentric circles with 1/8” OD and 1/16” ID and cut out the space between them to a depth of 0.010”. This design may change. Perhaps I should cut the center part out too. If I do, it’s an easy shape to work with so any change I make will be easy to do.

The next thing that happened is that I discovered a fairly major mistake. I was describing on the ModelWarships.com Forum how I do my alignments for locating various features and I discovered that I had botched the diving plane.


Long story, short,I had to fix it. Since the hull was good and had detailing on it already, I decided to simply cut the planes out, build new ones, and then reattach them, which is exactly what I did. The images below show the new plane over the plans, before and after cutting the plane into 2 pieces fore and aft. You can see how much better the alignment is.

Here’s an isometric view of the rebuilt stern piece.

It’s the right size, but the detail was horrid. I had to redo it one more time. Details of that process will be included in the next post.

CHEERS!!!

[rdutnell]

Re: USS Greenling (SSN-614) Scratchbuild

UPDATE 12A

Cool! The 12th update a little after 12 on the 12th day of the 12th month of 2012.
Well, in the last post I mentioned that I was redoing Part 7, the hull stern piece one more time. The next two posts will present the steps I took in redoing it.

[rdutnell]

Re: USS Greenling (SSN-614) Scratchbuild

UPDATE 12B

Continuing on…



















CHEERS!!!

[rdutnell]

Re: USS Greenling (SSN-614) Scratchbuild

UPDATE 13
One more update and you will be caught up to where I currently am in this endeavor. Once again, the focus is on Part 7.

Based on suggestions provided to me by my buddy who is making the parts for me, I added a chamfer and relief gap to the connecting flange on the front edge of the part.
To make the chamfer on the flange, I drew a line between the faces of the connecting flange and revolved it 360 degrees about the center axis of the ship. (There is a command that supposedly makes chamfers for you, but I couldn’t get it to work.)

I then sliced the flange along this newly created surface using the Slice Command and then discarded the end.

I then deleted the resolved surface…

And recolored the part.

The procedure for creating the gutter is essentially the same as for adding the chamfer, except a circle with a diameter of 0.04” was revolved.

One final bit of detailing was added to the part, that being the MBT No. 7 Flood Hole Baffle. This may change later since I have no idea what this guy looks like. I assume that I will be using metal for it, so I did the standard trenching to 0.01”.

Part 7 is now completed and ready for manufacture, unless there are unexpected changes, which is always a possibility.
‘til next time, “Keep your stick on the ice!”

[wlambing]

Re: USS Greenling (SSN-614) Scratchbuild

Hey, Big Guy!

I don't know where "MBT 7" came from, but it doesn't exist! There are only six! The stern of the 593/4 and 637 classes is all free flood space, lovingly referred to as the "mud tank". I think you are confusing a sonar hydrophone with an MBT vent valve. There is a flood port back there, but it's only there so the tank can fill/drain naturally. What plans are you using? If the yellow circle with the red dot in the center is labled as an MBT vent, it's wrong!!! It's too far aft to be a vent. The mud tank is the space where the rudder, stern planes, and stern tube bearing for the shaft reside. It got its name because of the silt, slime, and bearing grease that collect in there. The hydrophone should be represented by a plain, flat circle.

Sorry, but great work nonetheless!!

B^)

[rdutnell]

Re: USS Greenling (SSN-614) Scratchbuild

Hi wlambing!

Thanks for the comments, and there is no reason to apologize. I am always anxious to learn more and welcome all criticism.

As forthe plans, I'm not sure what their source is. Others might be able to tell you. Attached is a clip ofthe plans showing the part and the Legend ID'ing it.

When you say that the hydrophones should be represented by a plain, flat circle,are you talking just a little rise that is painted black, just an etching, or a small round piece of PE?

Thanks again for the input, though I must say that I'm perplexed now.

CHEERS!

[wlambing]

Re: USS Greenling (SSN-614) Scratchbuild

R.,

I would just scribe a scale 9" circle at the hydrophone location and you'd be good to go. In 1/144, that's really all you need. I noticed on the plan segment that there's another booger; specifically, Item 30, MBT 9 Valve. No such beast!!!!

There's way better plans out and about. As a recommendation, I would find some good ones like Greg Sharpe's, or maybe something from Matt Thor, as he make a 594 kit. Somebody out there has to have good ones, lifted from official USN drawings!!

Take care,

B^)

[rdutnell]

Re: USS Greenling (SSN-614) Scratchbuild

Well,
These were free and they certainly worked good for making the hull. Until yesterday I thought they were awsome.
I guess you get what you pay for.

[rdutnell]

Re: USS Greenling (SSN-614) Scratchbuild

UPDATE 14

The last thing I said in my last update was that Part 7 was completed, unless something unexpected happened. Well, I had barely typed the words when the unexpected did in fact happen. I received an e-mail containing photos kindly advising me that the rudders and stern planes did not have “bearing roots” as shown on the plans I have, and thus the way I built it. Soooo, I changed it yet again. It was worth it. Not only is it fun and gets easier and faster each time, it really looks better.








Having completed the Stern section, I decided to give all of the hull pieces the flange treatment and put it together. The first piece fit nicely. Everything was the right size (comparatively) and properly aligned. When I got to the next piece (Part 4) the diameter was significantly larger than the diameter of the piece it was supposed to mate with. It was the first center piece, so I knew what the diameter was supposed to be and it was spot on. That meant that everything before that was a hair too small. We’re talking about 0.02” in 2.4”, but it would have been noticeable and although it probably could have been sanded down, I might as well get the parts right to begin with (if possible).

This would seem like a small problem. All I needed to do was scale the entire rear assembly the amount needed to make it the right size. The problem was that the connections were made before, when they were mis-sized so scaling the one piece up threw everything off, and it was kind of a bugger trying to redo it. I tried to patch work it and it probably would have been faster to simply remake the entire part. In any case, I finally got it done and moved on to something different for a change, the waterline.

I started by aligning the”model’s” Dunce cap tip with the Dunce cap tip on the plans. I then, used ellipses and arcs to trace the waterline as marked on the plans. When I got to the straight part, I realigned the model so the bow of the ship was aligned with the bow of the plans, and again traced the plans using one big ellipse (how convenient!).

At this point I was curious as to just how much AutoCad has improved recently so on a whim I typed “projecting a polyline onto a solid, and TADA! The PROJECTGEOMETRY command does just that, it projects lines or shapes from a flat surface onto an irregular shaped one. You just simply place the line you want projected over the object you want to project it to and presto, your flat shape conforms to the shape. In the image below, I had just projected the traced waterline onto the hull.



The only problem is that at this point, the projected line is a so-called spline. Splines are difficult to work with and can’t be manipulated like I need. However, I was able to use the projection to align the traced polyline I had created. The polyline is needed because that is what I used to extrude the future “scribe” line on. I used a 0.02” wide x 0.1” tall box with the ends filleted at 0.05” to extrude around the polyline. This created a scribe 0.02” wide of varying depth due to the nature of the surface, but typically approximately 0.04”-0.06” deep.

Now let me say that when it comes to scribing widths, I am pretty much clueless. My investigation into the topic was limited to measuring the scribe lines in the rudder and radio towers from the 1/350 scale Essex kit, using a Micromike I obtained years ago, that has divisions of 0.002”. The thicker more pronounced lines in the rudder appeared to have polygonal cross-sections with bottom widths of 0.01”and top widths of 0.02”. The thinner lines were 0.01” wide, so those are the dimensions I’m using, 0.01” for less pronounced features and 0.02” for more pronounced features. Right or wrong, that’s what it is. Ideally, I would send a test piece to my buddy with different size grooves and protrusions, but I certainly don’t want to wear out my welcome before the model is built.

Anyway, here are some images of the way it came out.







Next is the Anti-skid coating outline.

CHEERS!!!