The British T Class 1:72 scale

[Kazzer]

If I did my math right thats 46" long. Is that right?

274'/12 = 3288" 3288/72 =45.66"

[Kazzer]

I've managed to do a little more to the plug. I guess the most difficult thing was trying to figure out exactly how I was going to make the molds. Seeing as my sand/epoxy molds idea seems to be a winner, then how to actually get this puppy done was a bit of a worry. i have a lot of money invested in the plug and I didn't really want to ruin the thing.

So, here is my 'cunning plan' (to quote Baldrick -Blackadder)



I cut a board of Melamine MDF (now referred to as MMDF in future) about 1" longer and wider than the plug. I already had a strip of MDF cut to the profile of the keel, so I hot glued that to the center-line of the MMDF, then mounted the plug on top. I secured it in place with wooden blocks cut 1/8" lower than the waterline, which ran parallel with the keel.
Then I shaped a strip of hardboard to the edge of the boat along the waterline and hot glued it on top of the blocks.

Next, comes the sealing of that joint with modelers clay, and the installation of the MDF board cut to go on top of the plug. This will hopefully give me the first quarter section of the four molds.

On reflection, I could have left those darned torpedo tubes on! Hindsight is a wonderful thing!

The plug has been waxed and sprayed with a couple of coats of PVA, but I intend to treat each section again, prior to pouring the epoxy slurry.

[oztruck]

The eyes of the world are upon you. Just luv the old pommy boats.

[Kazzer]

The hardboard gets all the edges along the plug filled in with clay. Then a coat of Wood Sealer.




A formed section of 1/4" MDF is sealed with Wood Sealer and then tacked into position atop the plug with latex caulk.



The MMDF board (laying flat) has been coated with wax. It will be screwed into its vertical position after sealing with PVA.

[Kazzer]

These long thin models are a real pain to photograph well.

On the left, I've screwed the MMDF board on, then caulked the joint to the hardboard. On top of the model is a 1/4" thick section of MDF contoured to fit the boat. I put a thin line of latex caulk on the underside to seal it. Then I ran a wet acid paintbrush over all the caulk to smooth it out. We'll let that set up tonight, then I'll do the MMDF end caps and - we're almost ready to pour!!!!!!!! Egg-ziting izn't it!

[Kazzer]

I coated the inside of the mold and the plug with another coat of Release Wax



Next, I installed a piece of steel rod. Actually, it was one of those rods used in the garden for holding up flowers.

(The rod is hard to see as it's dark green, just to the left of the MMDF board)
Pouring the resin



Adding the sand


Pouring the mix into the mold



AND!!!!!! Ta!!! Daaaa!



It's done!!!!!!!

I rattled the mold on the table for a minute or so, to help the resin settle.

Until - tomorrow. Patience!

[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.

[oztruck]

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

[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.

[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 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]

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'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]

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]

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.