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1/96 Ohio SSBN/SSGN build underway

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1/96 Ohio SSBN/SSGN build underway

Postby Pirate » Wed Jun 20, 2007 11:42 am

Well, I've finally started the actual building of a 1/96 scale Ohio class. With the help of EB dockside plans from Don Evans, and input from many current and past SSBN crew members, updated and what I'm told are very accurate plans have been developed. Now the building can begin.

Plans are to build a master that's ready by the '07 Sub Regatta. From that, molds will be made, and multiple reproductions should be available by '08. I'm not going to take any orders until all the molds are done. But I may start a waiting list once the master is finished. If you would be interested in a model like this, go ahead and chime in. The more enthusiasm there is out there, the more I'll have, and the faster I'll build.

If any of you have seen my Seawolf and Virginia, you've seen models where the masters were made by turning wood hulls on a lathe. Even at their size, the Virginia was still too long for my lathe, so I only turned the tapered bow and stern sections, and was lucky enough to find a PVC pipe with the exact diameter needed to fill in between. Well, this puppy is a whopping 70" from stem to stern, and there ain't no way I'm going to turn that on a lathe. Not to mention, with the missile deck transitions on the Ohio, that wouldn't work too well anyway.

So for this model build I have taken a que from Kevin McLeod and the very large Oscar II that he made. I'll be using the foam sectioning technique with a few simplifications for shaping the foam to get irregular contours easier. Let's begin.

I started with the 2D plans and developed cross sections that would match the 9/16" and 1-1/2" thick construction styrofoam that I had, and is the easiest sizes to get. In the photos the blue is 9/16 and the pink is 1-1/2.

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Here you see my first mistake. Because the foam body of the master will be coated with plaster, and eventually a epoxy resin and glass shell, these cross sections don't account for the added thickness. So I drew circles 1/16" inside the actual exterior circles and printed them out and pated them down. Steve Neill says he uses old cereal boxes for a cardboard to paste them on to. Well, I don't eat enough cereal, so I got some thin gray chip board form my local art supply store to use.

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The next step is to cut all of these out. They will be used to sandwich a piece of styrofoam between, with each side registered to the other. Then they become cutting guides for the hull contour. You'll see later.

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After cutting out the cross sections, I then cut a slot up the center of each the width of the spineboard I am using. This slot goes up to the center line on each, and by that resting on the top of the spineboard every piece will be registered to one another. I then coated the edge of each with super glue to make them hard. Then the foam cutting wire will be able to travel over the edges without burning or cutting them.

Here they are lined up on the spineboard. I Super77'd a plan profile to the side of the spineboard which shows me where each section should go for a guide.

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From a 3/4 angle, you can start to see what the 3D piece will look like. And you can even kind of check your work at this point. If something is dramatically wrong, like a cross section is missing, you'll see it here and hopefully save some cutting and frustration.

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For the foam sandwiches I glued one cross section to one side of the foam. Then on a bandsaw (because that's easiest) I cut out the slot for the spineboard. The I glued (Super77) the next cross section in the sequence to the other side of the foam by lining up the slots. With a hot wire knife against the edges of both sides you can cut the foam center to a straight-line contour of each section. I take the cross-section templates off each foam piece once they're cut by using rubber cement thinner to unstick the Super 77.

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Once all the sections are cut, they can be assembled on the spineboard in order, checked with the plan underneath, then Super 77'd to one another.

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Here you can see them together, now really beginning to take on the distinctive shape of the Ohio bow with the missile deck beginning.

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With a little light sanding from one of those sponge sanfing blocks, the shape can be further refined. Don't sand away all the high edges, they'll be used to determine the depthe of the plaster coating later.

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So far I've only got the bow back to where the missile deck fairwaters begin done. In this photo I give you an idea of how big this sucker will be. Ain't it perty?

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More as it gets done.

Pete
Last edited by Pirate on Wed Jun 20, 2007 1:30 pm, edited 1 time in total.
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Postby silent runner » Wed Jun 20, 2007 11:53 am

At least I'll have a year to clean off my workbench.

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Postby STARK » Mon Jun 25, 2007 6:24 am

She looks so right Pete, that bow is trickey and you nailed it from the photo. Took me a few days with Plastic to shape her!

I want a model too when your ready to ship-em!

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Postby Mylo » Mon Jun 25, 2007 2:02 pm

REALLY looking good.

.....what would we do without our beloved blue and pink foam board ?

It looks as though billiards are on hold for a while.

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Postby Pirate » Mon Jun 25, 2007 6:39 pm

Mylo,

Billiards and poker on hold. That's actually a poker table top I am building to go over the pool table. Turning it over is to give me a work surface, but it's not quite working out that way.

Submarines are full speed ahead though.

Pete
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Postby Bigdave » Wed Jun 27, 2007 7:39 am

Hi Pete,
Looks great so far! :D
But I thought you world have it done by now. :roll: :roll: :lol: :lol: .

I used the same system to build my Dolphin except I did not make a master and mold. I did lost foam. Steve's system does work very well.
Steve probably has unlimited cereal boxes living in the land of granola. Ha!! I have found a good source of material at your local USPS. Some of the smaller Priority mail boxes are made out of a very nice thin and corrugated cardboard. It works great for making the patterns. The photos make it look thicker than it is, but it is very thin, stiff and easy to cut.
Keep up the great work, and I will see you at the regatta. BD
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Postby Pirate » Fri Jun 29, 2007 8:59 am

Thanks for the tip on new materials Dave. Although for this, since I use it as a guide for my hot knife, I want it as thin as possible. Otherwise it causes the profile to have more material added.

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Postby Pirate » Fri Jun 29, 2007 9:30 am

A little progress made.

I finished all of the chip board cross-sections, cut the remaining foam pieces and glued them up on the spine board. This is one long S.O.B.

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Here you can see again on the stern, as it did on the bow, how the plan pasted to the spine board with my cross-section lines helped to make sure things were lining up and coming out to the correct length. The gap between the edge of the foam and the outer margin of the hull will be filled by layers of plaster and fiberglass.

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With each successive piece of foam cross-section cut, I transferred the axis lines from my plan, which was glued to each chip-board cross section template, to the foam. Then, once they were glued together I connected the dots with a straight-edge to get very accurate vertical and horizontal planes.

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Here you can see how the spine board keeps everything nicely inline, as long as your spine board is straight. The numbers for each cross-section are listed on each piece, as well as on the plan pasted to the spine board. That sure helps keep things simple.

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Once all the pieces have been glued together, the next step will be to add plaster to the foam to fill low spots and even out the surface. I want to take the carcus off of the spine board to do this so I can work all the way around it, but it is so long, and the glue joints and styrofoam are not that strong, so I am afraid the longitudinal stresses of trying to pry it off of the spine board will snap it. SO my next step is to use some of that plaster-of-paris hobby cloth to wrap the sucker like a mummy. Here you can see what it looks like dry, and with one piece applied

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Once wetted, this cloth will conform very nicely to the foam so that hopefully I can avoid lots of air pockets between the foam and plaster layers, which would cause cracking. And it should hold the foam carcus together really well. We'll see.

More once the mummy is wrapped.

Pete
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Postby Bigdave » Fri Jun 29, 2007 4:58 pm

Hi Pete,
I used it as a guide for my hot wire as well. As I said it is much thinner than it looks. I also took into account the thickness when I did the dimension calculations in Photoshop. Steve's trick of adding the CA to the edge of the cardboard really stiffens it up and the hot wire works smooth. It does take a bit of practice to get the right amount of tension and speed on the wire so it will cut and not melt divots. Ha!! :lol:
Yours is looking great!!!!! :D :D :D BD.
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Postby Wayne Frey » Tue Jul 17, 2007 9:57 pm

Great work Pete!!!
Awsome looking already.
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Postby Navy2000 » Wed Jul 18, 2007 9:39 pm

Any new photos of how the model is coming along yet?

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Postby Pirate » Thu Jul 19, 2007 10:34 am

Yes. But they're still in the camera. I've been doing more building and less posting. Although it may not look like much progress since it's filling and sanding, filling and sanding. I'll be gone through the weekend, so new updates next week.

I can't wait.

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Postby STARK » Fri Jul 20, 2007 8:28 am

It can take up all your time, the back and fourth work of a proper scratch build!
The Craftsmenship of a profesional, and Pete does that so well!

I look forward to some more photos.


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Postby Pirate » Wed Jul 25, 2007 1:52 am

OK. Made a little progress.

I got the thing all mummified with the plaster of Paris cloth tape. It held it together good, but in the process I lost my center registration lines.

Then I coated the whole thing very thinly in drywall plaster.

Here you can see the plaster of Paris tape on the bottom, and the drywall plaster going on on top. If I had to do it again on a shorter hull, I would skip the plaster tape. This caused a lot of high spots where it overlapped itself. And when I sanded down into it, it got very rough from the fibers sticking up. I needed it to give some strength to the foam holding together because of the length of it, but on a shorter model I'd just go with plaster over the foam.

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Here's the entire thing coated in plaster before any sanding. Oh, it has some sanding to knocjk all the high spots down.

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Here it is after some sanding. In order to get it tobe even longitudinally, I made a sanding tool from the styrofoam. These pieces are cut to the diemeter of the hull, minus 1/16 inch which will be taken up by the final resin and glass layers. The tool was then run up and down the master length-wise to get a straight surface. You can also see a sanding sponge and a long, straight piece of wood wrapped in sandpaper. The longer the better for getting the sides really straight.

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After getting things pretty well straight, I sealed the plaster over the whole thing with shellac. Some areas ended up showing the foam underneath again, and shellac will not melt it. And it does a great job of sealing up the plaster.

Then, that allowed me to hit it with a coat of primer to help me see the imperfections in the surface. Without the shellac the spray primer would dissolve any foam exposed causing huge craters which would need to be repaired.

This photo shows the master after many rounds of plastering and sanding. After the initial long sanding, I needed to fill ruts made by the tool to get it nice and round around its width. After each sanding I recoat with shellac. Tis allows me to add more plaster where needed and not sand easily down into the previous layers.

The second photo shows up cloae some new platser applied (hopefully the last of it) up against the surrounding areas highlighted by the gloss of the shellac.

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I'm trying to get this as perfect in shape as I can before the glass. It's much, much easier to sand plaster than body filler and epoxy glass. And getting it right now will mean much less workon the fiberglass later.

Next time I'll show how I sand it to not get more longitudinal grooves and get the surface back to even and round.

Pete
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Postby ManOwaR » Thu Jul 26, 2007 8:42 am

Pete it looks great!
I would have to put a bet on that you are missing the MDF right now though? It looks like the foam and filler technique takes all the fun out of the game by eliminating the lathe.

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