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Bridge Superstructure, part I

November 9, 2008 / efoeth

I’ve done a little work on the bridge, one of the major parts of the model. The entire superstructure from the deck up was built at least twice but I don’t have many pictures left of the original superstructure. As I’m working here and there on various parts of the superstructure, this category won’t be that organized.

These pictures were taken from the first bridge attempt and contained a lot of small errors. For instance, I choose a 0.25mm thick plate as a deck part which is too thin. A 0.35mm plate makes all the difference. The conning tower is built up from plastic plate and filled with putty. The detail of the slits in the armour plate of the conning tower was added by plastic strip. The side of the superstructure is made from strips, as to leave out a few spaces for a series of grids. This all didn’t work out very well and the entire model of the bridge was thrown out after some considerable deliberation. This is the major reason the model isn’t finished yet.

Here’s the mark II bridge base part. The conning tower is made from strips glued against a few support parts and the side of the bridge is a single plate. This works a lot better.

Here’s a nice recent shot of the conning tower and the rain guards above the view slits. This was very difficult to do, as I want to have the guards to droop down at the ends and still look properly. All the brass wires, made from 0.1mm winding wire, were first bent around a strip of the correct width, glued in place and trimmed. There’s some variation in height, but it’s more of a mess on the real ship!

A voice pipe can be seen curling over the roof on the conning tower into one of the viewports. After staring at my picture collection for an hour or so, I found a few images that show this voice pipe and added it. This is all the material I can find, but I think it is quite convincing. An eye for detail?

The platforms of the forward quad Vickers guns appeared to be open at the rear, and not closed as I originally thought. I spent this weekend carefully chipping away the old part and added a new platform. Much better!

A series of wind baffles are visible near the forward torpedo lookouts. Only a few photographs are available as this is a very late edition, but enough to make a good approximation.

The pictures of the air defense platform (the highest and open deck below the spotting top) was also fitted with a wind baffle and it again took a lot of time to find the right photographs to get an idea of the layout of this detail.

At left you can see that how it was fitted to the splinter shield, going around the small sponson. At right, the wind baffle is seen from two good angles.

Here you can see the model. The sponsons in the splintershield were particularly nasty to build, being both complex in shape and quite small! The front view shows the bridge suffered a bit from sanding, but the model itself looks good enough. The wind baffles were constructed from 0.13mm plate. A knuckle was added to the plates using a small folding jig.

Sounding Machine

September 28, 2008 / efoeth

A sounding machine is a device for (as far as I know) measuring the water depth. I wouldn’t have noticed it if it weren’t for these two photographs (from the HMS Hood site). . The “Anatomy of the ship: the flower-class corvette Agassiz” has an excellent drawing of the Kelvin Sounding Device Mk Iv on page 16, but it’s a different type. Good enough for basic dimensions and for some detail.

Fortunately, around the time Hood was built, several of the Imperial Japanese Navy ships were built in Britain and carried the same equipment. The photograph at left was found on the net, taken in a Japanese museum. The picture at right is from the book “Grand Prix Shuppan: Anatomy of Japanese Battleships 2”. From these two images I made a small photo etch design in Autocad.

At left, the photoetch parts are shown. I added some disks to simulate the detail prior to cutting the parts loose, making it easier to handle them. The lower picture shows the finished parts. Cute! The picture at right indicates where the sounding devices where fitted to HMS Hood’s bridge structure. That is, if they were still fitted in 1941?

How to make a miniature hull

September 14, 2008 / efoeth

Making a large full-hull model of a large model is one thing, making very small boats and launches is another and requires a different approach. You can hollow out small hulls or batter a sheet of metal against a plug, both with nice results. I chose to use vacuum forming, as it is repeatable and the hull is now from styrene which is easy to handle. My simple vacuum former was explained earlier here.

With a technique ready to be used for small hulls, the only thing left to build are the hulls themselves. After having spent some time tracking down the hull lines of all but two of HMS Hood’s boats and launches at the time of her sinking, I decided to make them all to scale with correct hull forms to match. Some of the pics I show you are already quite old and bad. At the time of this writing, most models are nearing a state of completion but are not quite ready yet.

This is a bad picture of the lines drawing of the 45ft motor launch. I’ve drawn a grid with plate thicknesses to scale, in this case 0.75mm and 0.50mm. When the lines are mostly vertical you can do with thicker strips. Near the bottom of the launch, the lines change quickly and thinner plates are required. These points were measured and put into a spreadsheet, for which I use Microsoft Excel.

Plotting the measurements is a quick way to see if there are any measurement errors. I plotted both the stations and the waterlines and both must look right. (click images to open if they look poor in the post). Once you have the measurements right, you can start cutting the ingredients for the hull.

There are two basic hull forms for HMS Hood; the soft and hard chine types. The soft type hull requires many strips of different length, while the hard chine hull has fewer unique components. The left part of the image shows a collection of strips required for building a small hard-chine hull, the right part of the image shows all the strips laid out for easy construction of a soft-chine hull. In order to cut these strips accurately to size, please see the chopper page in the tips section.

The tiny hull is now built up by stacking the styrene strips. I only glue two or three strips at a time, aligning them by eye and squeezing them a bit with the caliper. After all sections are glued and the glue has dried, the sections were sanded down a bit and glued to each other. The result is a very clunky hull that might look like it isn’t going to be anything. I completely covered the part with putty. When it has dried, just sand away until no putty can be seen. The small hull just barely contains the shape you want, so once the putty is gone you’re left with small hull. At the bow (and some sterns) you need to be careful not to sand away too much. Without too much trouble, you form the plastic blocks into a reasonably faired shaped.

My first attempt is seen at left, with the bow reconstructed using putty. This isn’t necessary and the center image shows a hull make from styrene only. As both sections on either side of the maximum thickness are the same section width, I used strip twice as wide. The hard-chine boats were finished with putty. Note that very little putty remains on the hulls. Note that vacuum forming will damage the moulds a bit, so making a resin copy might be a good idea.

scaling hull lines

I could not find lines drawings of the 42ft motorized barge and the 16ft fast motor boat (skimming dish). I used lines drawings of similar hulls as a basis, with the 45ft barge as an template. For this barge I do have the top view, so I measured the top outline of this barge and used the 45 ft barge as a base template and scaled it accordingly.

The above chart plots the normalized ratio of the beam of the 42ft barge to the 45ft barge (local beam divided by maximum beam). I then use a small averaging polynomial to obtain a smooth curve (e.g., a trend line in Excel). The height can be scaled linearly, by taking new thinner plates. This may require measuring all data again for the new plate thicknesses.

The results are compared and look fine.

After the hulls are complete and vacuum formed, the hulls need to be trimmed to size. For this, I use another cutting template. The height is taken from the side view of the hulls. Cutting it by hand doesn’t really work for me and when you need a few identical hulls, I really want something to look repeatable.

Here’s a pic I took today of a few of the cutting templates for the various hulls.

Another pic of all miniature hulls except the hard-chine 16ft fast motor boat which I apparently misplaced indefinitely. HMS Hood carried a 16ft dinghy and a 16t fast motor boat, for your information, and not two identical 16ft boats. The top row, from left to right, shows the 45ft motorized barge, the 42ft motorized barge, the 35ft fast motor boat, and the 32ft motor cutters. The lower row shows the 30ft sailing gig, the 27ft naval whaler, the 25ft fast motor boat, and the 16ft dinghy. Note how well the different lines of the various hulls have worked out. For making these small boats, it’s important that the outline at the deck is correct so that the cabins are not off scale. Note that he 45ft and 42ft models, based on the same parent hull form, look very similar.
I have an example spreadsheet right here to scale one set of data to the next. Here is the 25ft-fast-motor-boat sheet that adds the number of required strips. It also has a section where the sides of the hull are straight, so all values are interpolated linearly. This sheet also scales all measured values to the right model scale. None of the sheets take the thickness of the vacuum formed plastic into account, so perhaps you need to make everything a bit thinner if you really want to be properly scaled. For these hulls, I don’t think it’s really necessary.

Drilling with the Punch & Die set

September 14, 2008 / efoeth

Another small tip with a Punch & Die set. It can be used as an alternative for drilling, which is near impossible for the part below. The problem is always aligning the part with the set so that the punch is properly centered, but that can be easily solved

This series of pictures shows the in-progress platform of HMS Hood’s type 279 radar antenna. The platform is very small and is to be fitted to the mast. But as it is very small, it will show when it is off center making proper alignment more important. I use the Punch & Die set to punch off a part leaving the end of the platform circular, making it easier to position and glue to the mast. In stead of making a lot of platforms and keeping the one which worked out best, you can also first glue a disk (or rod) at the exact location where you want to punch out excess material. With styrene parts, you have some time before the glue sets and shift the disk to its proper location (top right). You can then—after the glue has set—use the disk to position the part with respect to the set simply by putting it in the correct hole. Just tap the punch gently and the part is done.

I use this trick quite often as it is easy to use and accurate. Drilling very small parts isn’t always possible, as you don’t have any space to hold them fast and they often tear when using larger drills. Very small parts can be destroyed during the punching as well, but less often than with drilling.