The British T Class 1:72 scale

[Kazzer]

With the two molds bolted together, I poured black resin into the keel being careful to only let it run directly into the slot and not drip onto the side of the boat. This prevented the shot sticking to the sides and it rolled neatly into the resin. Once the keel was filled, I placed tape over it and wetted it out with lacquer thinner to help it lie flat. Finally, I coated it wath another coat of resin.



The skeg was filled with resin and a 1/8" bent brass re-bar, just to ensure it withstand the odd beating.

On the bow and stern, I filled these areas with a mix of resin and Cabosil to give them extra strength. I hope to use the stern to put the securing screw for the upper hull.

[Kazzer]

I've always hated those tabs everyone uses to get the sides of our models to line up together. They're a pain to install and look like hell.
I don't have the complete answer to the problem, but I decided to reinforce the edge of my model to hopefully prevent it from flexing quite so much.

After looking at several ideas to reinforce the edge, including styrene L shaped extrusions, I thought I'd try this - a piece of string! I know, it sounds silly, but ---



I soaked the string in resin, then laid it along the edge of the hull, on the waterline. It wobbled around a little, so I mixed some Cabosil and chopped strand fiber into a little resin, then laid that up to the string with an acid paint brush. Finally I pulled one end of the string while holding the other end and it straightened out very well.




The yellow string is just there to show what it looks like before the resin was applied. See the string bead on the right edge.

The string after it set up is flush with the mold edge, and should make quite a difference to the flexing. The hull at this point is over 1/8" thick. We'll see if it improves things. It was certainly easy to do.

[trout]

Nothing can go wrong, it is just a change in course. Can't wait to see it pulled and put together!

[Kazzer]

I've decided to give the molds a try and see if I could get a test shot off.

I put two coats of wax, then sprayed two coats of PVA. I have a neat little spray gun that is simple to operate and clean - see bottom left.



Next, I made a template for thin card by laying it into the mold, rubbing the edges with my fingers to mark the cut line, and finally cutting out the template shapes.

I've never got on well with fiberglass cloth and corners. Pulling the cloth around a corner usually means problems for me, so I have cut the cloth along the edges of sections in the mold. For example, you can see where I have cut along the edge of the ballast tank. Lower hull and ballast tank are two pieces of cloth. The layup went well.





Here, I cut out the fiberglass cloth and after applying a gel coat all over the mold, I laid the cloth in it and applied more resin.

This isn't a job I'm good at, or particularly like doing, but onward. After I thoroughly wetted out the cloth, I applied a little lacquer thinner and rubbed the whole cloth area with my latex gloved fingers to flatten it out and - hopefully - remove all the bubbles. Now, I've seen bubbles in Darnell (metcalf/MBD) and OTW (No disrespect meant) so it's just a process of the hand lay-up method. Thankfully, these bubbles are usually easily repaired.





I used a brown dye in the resin, but it doesn't show up too well against the tile red color.

My 'cunning plan' is to let the two lower hull halves set up, then after cleaning up the edges, mate them together and pour resin and lead shot into the keel. This simple move will join the two halves together, and form the keel with ballast all in one move. Slick eh!!!! What could possibly go wrong?

[Kazzer]

For those that are interested here is a link to the film I mentioned. Not something I'd race out and buy, but nonetheless I was very happy to see my beautiful wife made such an effort to buy me something I had not thought of.

http://www.imdb.com/title/tt0042810/

It features a fictional 1950's T class "Trojan". The film was almost never released due to the loss in 1950 of a T class, HMS Truculent.

....Mike have you seen this film?

J

I think I may have, many years ago, along with my dad.

The crew of a submarine is trapped on the sea floor when it sinks. How can they be rescued before they run out of air?

I seem to recall it was an unpleasant experience for me, as my dad relived some of his experiences in these boats whilst watching it. It was a T Class (Tactician) that scared him so much, he quit the Navy. I don't think I want to watch it, but thanks.

[Kazzer]

And then - DISASTER!!!!

I pulled away the black mold from the plug fairly easily, and the final mold, which was one of the first pours I made - stuck! I heaved, tugged, swore, cussed, heaved and tugged - and eventually, with a lot of creaking, snarling and cracking, the plug came away.

But it left substantial lumps of drywall and foam stuck well to the mold, as you can see here.



Arghhhh!



After soaking the drywall under a tap for 5 minutes, I was able to pick it away from the mold. Fortunately, there was no damage.

I can repair the plug, and once I've done that, I'll wrap it up and store it - just in case.




Note the red lines here. Along both of these, the edges are really bubbly. They are easily repaired, but I am a little puzzled as to why they are there. I haven't had this happen before, and I proves I have to get more method in this process to get it 100% every time. I usually tamp the resin in the mold several timnes, and whack the mold box to shake bubbles free. Maybe I didn't do that this time? I can tell this was a sloppy mix, by the look of the finished job, so a drier mix wasn't the problem.

Anyhow, we have a T class 1:72nd mold. This boat is as good as in the water.

[Kazzer]

After cleaning up the mold edges a little more, I fitted the two molds together, then drilled holes to accept a 3/8" bolt. These are to pull the two halves together.

On reflection, I think I would makes sure i placed the bolts through thin tight-fitting tubes, and placed them into the empty mold box, so the tubes were cast into the molds. I can see mistakes being made drilling these holes.


Now I've finished my first attempt at making molds from a plug, I have a better idea of what not to do.

I have to improve the waterline board. My 1/8" thick piece of hardboard was difficult to keep straight, and I have a small error in the nose of the boat. It won't notice because we're gluing the top and bottom together at that point.

I will put the tightening bolts and tubes in before pouring the resin.

I'll make the resin a little sloppier, although there we no voids in the casting, I did notice some tiny bubbles on the mating side. They won't effect the product.

My mold box was messy, I need to change from MMDF to MDF and be more precise in measuring the box height.

There are a few dings in the plug that have left bumps in the mold. These are easily sanded down, and I think it's easier to do this than try to fill the dings on the plug.

[Kazzer]

THE MOMENT OF TRUTH HAS ARRIVED!

I poured the last section earlier this morning. I used a black die, simply because I wanted to see the effect of the color (for another little project I have in mind)

After about three hours, I started to trim off spew and in doing so, I knocked one section as I pulled off the MMDF board. The two top parts almost slid apart as you can see here.





The top that came away first can be seen here -- PERFECT!!!!!!!





Both port and starboard above waterline molds -- PERFECT!!!



Lets have another look at them - DAMN THEY'RE GOOD!!!!



And now, we wait a day for the black section to cure out a little more.

Note, the plug is not the slightest bit damaged.

HE! HE! HE!

[Kazzer]

I've removed the MMDF, waterline hardboard and general crud and ended up with the last quarter exposed.

There were drips and stuff to contend with - the ugly side of this experiment.
Thankfully, PVA came to the rescue I LOVE THIS STUFF!!!!!!

See how this green film has de-laminated from the hull. The skin has peeled at the slightest touch, so the drips, splotches, and crud easily come away. I can pick this stuff off with a fingernail. Better still, it will dissolve with a wet rag on it, and can be re-applied in an instant.




I have an hour's work to clean up the plug, ready for the fourth pour.

Tomorrow!

[Kazzer]

I mixed up the resin, 2 quarts base, 1 qt solidifier with 1.5 gals of sand.

I like my resin warm, it flows better at about 80 degrees. Any hotter would cook this stuff off too quickly, so I placed a glass aquarium heater in the mix for a few hours.





I've always had a few problems splitting these molds apart, so I'm trying this idea. Two washers with a smaller one in between, then glued to one side of the first mold. The other side will be glued into the fresh pour of epoxy mortar. After pulling out the little washer, I have enough room to drive a wedge in without damaging the mold edge. We'll see!




Last quarter to be poured tomorrow!

Did the calculations of resin and sand work out? Yes, I had about two tablespoons left over! Sheer genius! (Damned lucky is nearer the truth!)

[Kazzer]

I thought I'd do a little maths on this next pour, just to see what volume of mix we actually use.

The section we are going to fill is 48" x 3" x 2.75" a total volume of 396 cu ins

7.48 gals in a cubic foot @ 1728 cu ins in 1 gal

therefore 396 / 1728 = .23 cu foot 7.48 x .23 = 1.72 gals

We have some of that void filled with the actual hull, so we could guestimate reduction in this figure so lets say 1.5 gals.

I'll mix up 1/2 gal of resin and add 1 gallon of sand. It's always a good idea to have some other little jobs in hand where you can pour any excess. For examples, some spalled concrete, a crack in the floor, another smaller model. I have inserts to make yet to press the resin into these molds, and as it doesn't really matter what they look like, I could just fill up the mold in stages.

Lets begin! But first - my afternoon nap!

[Kazzer]

It's 8pm on Tuesday, and I just removed the sides of the mold after pouring some 5 hours ago. The resin is still warm but a little soft, so scraping the odd bit of spill and spew off was easy.


So, here she is! We're looking at the above waterline completely encapsulated and the underside bared and ready for another pour treatment.


But right now, I'm going out to have a quick pint. And then - tomorrow - maybe The Grand Finale!


The MMDF on the left is the original bottom of the mold box.

[Kazzer]

I marked the first mold with dimples drilled into the side about 1/4" deep using a 3/8" drill. These are to locate the next section which is about to be poured.

I made a mistake with the waterline hardboard and forgot to allow for the side wall to go in, so had to start over. Then I cut the darned thing incorrectly and had to bodge it up a bit. There are no photos of this, I just couldn't bring myself to take them.




Anyhow, the board is in and the edge along the waterline of the plug is filled with clay and smoothed out. The MMDF side is caulked with Latex Caulk.



I coated the trough with Freeman Wood Sealer, Release Wax and two coats of PVA sprayed on.

Finally, I poured in the mixed resin, about 1/2 gal resin and twice the volume of sand, maybe a bit less, I wasn't really counting.



Tomorrow, we flip the whole thing over, remove one waterline board, wax up again, and pour the next quarter.

[oztruck]

You make it look so easy. A pleasure to watch.

[Kazzer]

After about 5 hours, I was able to remove the MDF along the top of the plug. As usual, thanks to liberal applications of PVA and Release Wax, it fell off. A quick trim of very minor spew along the superstructure, and we're ready for the next stage.

I spilled a little resin on the plug and forgot to wipe it off. As it was hard when I went to remove it, it took a little of the PVA with it. No problem, I'll wipe all the PVA down with a wet cloth, and then re-do it.


Here's a closeup of the top of the resin. You can see lots of bubbles solidified on the surface. These manifested after I'd shaken the part on the table and left the resin to settle. The shear weight of the aggregate in the resin pushed bubbles to the surface quite easily. More importantly, there are no bubbles within the mold.



Tomorrow I place the hardboard partition for the waterline on top of the wooden blocks on the starboard side.

Now the fun part begins.