USS Roanoke (Worcester class light cruiser)

I started building a USS Roanoke this week. I'm new to the ship combat hobby, but I'm a longtime modeler looking for something different to work on. R/C ship combat looked interesting, but I wasn't really ready to take the plunge. Then last Saturday I attended a build session hosted by Mikey, where I learned how to mark up a hull and put in a subdeck. I also spent sometime looking through Mikey's copy of Conways and of course asking a lot of questions. I left the build session ready to start on my own model. I liked the look of the Worcester/Roanoke and decided to start one as my first build. It will have plenty of room and being only a 3 unit ship I will not have to buy a lot of equipment.
Fortunately, the USS Worcester has a great website that includes scanned copies of the original ships plans. I downloaded the hull profiles the next day and fired up the CAD program. After a several of days of computer work, I had my drawings done and and was ready to start cutting out parts.
I have a small hobby CNC mill that I use to cut my parts. The advantage of the CNC is very precise parts, but I'm also limited to parts 12" or less in length, so I had to break up the bigger parts. I had some issues with cutting the parts, but for the most part it went well. The only serious issue was that I under estimated the amount of 1/8 ply I needed, and had to stop work to make a hobby shop run.
Mark

 

I started by cutting a complet kit of parts. Below you can see the ribs being started. I'm using a 1/16" end mill to cut the parts, which does a good job but leaves the corners in the notches a little rounded. I had to recut two ribs and one of the mid-deck parts, but all the rest of the parts came out ok the first time.
Just getting started on the rib sheet...

The finished rib sheet. This 17 of the 24 ribs, and only includes 1/2 of each rib, so I had to make two of these sheets.

 

Here are some additional parts
Subdeck

Top deck

 

With the ribs and keels done, I started fitting parts together. Here I'm working with the side keels which will form the water channel.

 

Very interesting, Mark. Fascinating method for producing the ribs, etc. How did you make the subdeck and deck?

 

Got to love cad designed and cut parts. Most model aircraft kits now are CAD designed and laser cut. The parts fit is awesome ... so good that I've been able to put together assemblies that stay together without using any glue at all! Of course, we use glue to keep them together. Heh.

Recently, I cut a set of ribs from a CAD drawing and was amazed at how precise they were compared to the usual hand drawn or traced rib patterns. The drafter did an outstanding job.

You picked an interesting ship to model Mark. Keep us updated on the build as it goes along. It looks great!

 

I started with a computer drawing of the deck made from the top view of the guns and directors sheet in the ship plans. This gave me the layout of the turrets on the deck and the general outline. From there, I figured where I wanted my hatches and drew them in. From the top deck I laid out the subdeck and included notches for the ribs and support lips with magnet holes for the hatches. With the outlines done, I had to break them up into pieces that my CNC machine could cut. In the picture you can see the lines where the smaller pieces were joined to make a whole deck. you can also just see a full size print of the subdeck underneath - I used this to make sure the pieces were all straight before gluing everything together. The little squiggles were used to align the various pieces.

 

CAD does make it easier to assemble the model, because the left and right sides are identical and also take less fitting time. I have posted my plans in case anyone would like to look at the details of the pieces or build your own some day.

 

Once I had all the parts cut out, I started to assemble them together. I started by trying to put the ribs on the keels and then add the subdeck, but the pieces did not stay together. Maybe next time I'll use a center keel from front to back, instead of splitting it to make a water channel. So I ended up by gluing the ribs to the subdeck first and then adding the keels without gluing them at first. When I was satisfied that everything was together, I turned the model over and rested it on its keels to get the proper alignment of the ribs and decks. To get the subdeck to bend up properly in the bow, I cut 1/2 way through it with a saw at several places. With the bottom flat, I added glue and locked everything together.

 

Here's some views looking down the inside of the ship. Small digital cameras are great
Looking towards the bow. You can see the bottom (mid?) deck, which defines the -1" line to begin the solid portion of the hull. The parallel keels will form the water channel once the hull is sheeted. You might also notice the small dots on some of the ribs. These are shallow drill marks to show me where the water line is.

This is the view looking aft. The two holes close to the center are the holes for the stuffing shafts. The outer holes are for the dummy shafts. You can also just see where one rib is relieved to allow the motors to have mounting clearance. All these holes were generated from the 3-D CAD model, allowing me to fit the components virtually before cutting any material.

 

Hi Mark,

First, great build! What can you tell us about your setup and how it is done? I have a micro mark mill, would like to eventually think about going cad myself. Any advice or more detail on how you actually made the plans?

Lou

 

Having seen this hull first hand, I have to tell you it is a rare thing of beauty. My build looks amateurish in comparison.

 

I must say, very impressive. You (and many other Fast Gunners) have a very different approach to building wooden hulls than I do.

I am curious, though. It looks like the middle deck (interesting new term, by the way) actually seals off a small compartment in the bow, and a small compartment in the stern. Is that the intent? If not, how do you intend to let water enter and exit (and protect the wood against water damage)?

Also, how wide and deep is your water channel? It looks huge!

 

For my CNC setup I use a Taig mill that I bought "CNC ready" and added my own motors and control system. I started with a Zylotec stepper driver and some NEMA 23 stepper motors. I use software called DeskCNC to generate my G-code files and also run the files - it outputs step and direction signals for each axis. I recently upgraded to servo motors and new servo driver cards because I wanted to run faster.
To cut a part, I first start with a CAD drawing, generally just a 2D drawing. I export that drawing to a .dxf file. I import the .dxf file into DeskCNC, tell it what tool I'm using, what side of the line I want to cut on, how deep it needs to cut, and a few other things. From those parameters DeskCNC will generate the G-code. On some of the parts I cut for the ship it took about 12 mouse clicks to generate the file. Once I have the G-code, I take the file down to my shop and load it on my CNC computer to run.
Generating the drawings of the parts can take a lot of hours. For this model I started with graphic files of the side, top, and hull lines that I downloaded from scanned ship plans. I imported these files into my CAD program (I use Rhino 3D) and then traced the major lines. With the lines drawn, I get rid of the picture file and scale everything to the right dimensions. I start by building a 3D surface of the hull by taking the hull lines and putting them in the right place on the side and top drawings. You can see the result below:

Next I take the outline of the hull and generate the hull surface from that file. Unfortunately, it is very tricky and I must of spent 4-5 hours getting the hull done only to redo it completely the next day. Once I have the hull, I generate flat planes for the waterline, middeck, and ribs. I also put in the basic shape of the shafts and motors by lining them up with the drawing.

Once all the 3D elements are in place, I use a command to generate lines based on the intersections of the 3D surfaces. For instance, a rib right behind the motor will intersect both the motor shaft and the hull outline. Once I turn off the 3D layers, I'm left with an outline of the hull where the rib passed through it, and there is a circle where the shaft passed through the rib. After this step, it's just a lot of cleanup and trimming to get the final part.
I think I spent about 30 hours generating the CAD drawing. It took this long in part because I do not use the 3D features very often, so I had a steep learning curve. But 1/2 the work is also figuring out how you want to assemble the model so you know how to draw the parts. I spent a lot of time staring at the ship views, figuring out how I wanted to put my hatches, how I was going to sheet the bottom, how I was going to mark the -1" line below the waterline, ect. And even after all that thinking, I have to go back and make modifications, like adding the seat for the CO2 bottle in the middeck. But, for the most part, it was fun.

 

My approach to building is influenced more by my 20 years as a model airplane builder, I have not seen that many scratch built ships yet.
There was a small compartment in the bow that was basically sealed, but I have since put a hole in it to cradle the CO2 bottle. In the aft section the deck doesn't go all the way back, so it is open already. I'll add some appropriate water channeling material to make sure I do not get any trapped water in those sections. As far as waterproofing the wood, I have not yet decided. I'm toying with getting a garbage bag, putting a pint of polyurethane in and shaking it up - Shake n Bake for modelers. Any thoughts on this method?
The water channel is about 2" wide and 5/8 high. The bottom is formed by the 1/8 balsa that I used to sheet the hull bottom.

 

I am making sure that I have no sealed compartments. Everything below the middeck (including the middeck) is either a minimum 1" below the waterline or 45 degrees below the turn of the bilge - built to Treaty rules. And yes, those areas are also where I plan to put my ballast.

 

After I got all the ribs and keels glued, I put the top deck on. I probably should have waited on this step, but I wanted to shape the subdeck and top deck together. Besides, once there are gun turrets, I can pretend battle!

I used solid balsa to fill between the first few ribs, and then 1/8 sheeting after that. While the hull looked like a nice gentle curve to me, when I started the sheeting I split several of the 1/8 sheets. I wet the balsa down on one side and after that it behaved better.

After sheeting the bottom of the ship, I knocked out the center portion of the ribs (I made sure I didn't glue to them) to create the water channel.

 

Nice build Mark! Not surprised about the aircraft expirience ... it seems we do well in the wooden hull building department.

That middle deck thing is a nice idea that already has me thinking how to incorperate it into my next build.

I've used both materials (resin and varnish) to waterproof wood hulls. Both work as well as the other, with the spar varnish being the lower cost of the two.

Another viable alternative to hull sheeting material is 1/32" thick aircraft plywood. One of the other builders in the hobby uses strips the width of two ribs to sheet his hull then smooths the edges together. Turns out a light weight yet tough hull.