Scratchbuilding Tutorial: Part II

(Spanish version)

PART I
PART II
PART III
PART IV
PART V

I am going to continue working on our turret. Now I am going to cut a strip of styrene to do the turret's top.

I'll use a steel ruler and a square set in order to make a straigh cut.

I cut the strip...

Cut another piece a little bigger than needed, place it on top and mark it with a pen.

The mark is going to be a little bigger than the actual top piece size, so I compensate it by cutting a little more than really needed.

Now I use a circular cutter to open a hole for the hatch.

Fits perfectly.

I observed, hovever, that the top piece was not thick enough. To correct this, I glue the top to another styrene piece.

I now wait some minutes to let it dry and cut (no need for rulers now) out the excess.

I carefully cut the hatch hole again.

As I plan to cast the turret, I need to close this hatch hole. I'll do that with a thinner styrene sheet.

I cut another strip and wind it tighly around my cutter.

I cut it roughly to measure, put it in place and glue it.

Once some minutes have passed, I cut out the excess styrene.

It's a bit crude, but we are going to solve it.

I dillute green Squadron's putty in industrial acetone (the kind used for cleaning nail polish doesn't works). The putty should be thin enough to be painted with a brush.

Now I seal every gap and imperfection with thinned putty.

This is the result, ready for sanding.

Now I am going to do a fake welding mark. I put plastic cement in the desired zone.

And I texture the plastic with a modelling tool.

Applying more cement will make the plastic softer.

Now it's time to work harder in the steel texture.

I play with the resulting texture alternating Tamiya's and Squdron's putties. I also use a hard bristle brush with a little acetone to add more texture.

Now we take a trip to the bit box...

And integrate the bits in the ensemble with a little putty thinned down in acetone.




Next day, we'll start working in the cannon's mantlet.

NEXT

Scratchbuilding Tutorial: Part I

PART I
PART II
PART III
PART IV
PART V

Now we are going to talk about scratchbuilding techniques. In fact, there is no point in making molds if you don't have a nice master model to cast!

I am going to do a T34-like tank for use it in Warhammer 40K or other wargames. I will base it on the KV-II I made before, so I'll just made a turret and a hull, using the same tracks as the other tank.

I'll start working in the turret, so I look for reference pictures in Google. This one is particulary useful to base my model.

I make then a quick sketch on paper, looking for the actual model dimensions.

Once I am happy with the design, I transfer the corners of the drawing to a polystyrene sheet using a pin.

I transfer just one half of the drawing, this is to avoid any errors I could have made drawing freehand. Then I join the points with lines over the polystyrene.

I transfer the drawing to the other half, measuring carefully

I cut the drawing from the styrene sheet to work more comfortably.

I cut the turret base. Cutting styrene is easier than you think, just put a steel ruler on the line and mark once or twice the styrene with your cutter. It's better to not use the cutting edge for this, use the other side of the blade, you'll notice that you'll make cleaner marks. Once the styrene is marked, twist it, the styrene will snap just over the marked line.

I also sanded the piece a bit.

In order to build the sloped armor I going to make an inner structure to support it. I cut a straight tire of styrene and make marks at its side with my cutter.

I use those marls to cut the styrene with my chopper. This is a must for every scratchbuilder around. A real time saver that uses very little space at your workbench.

Those are all the pieces I need.

I glue them in place with polysterene cement.

I'll cut now some little reinforts.

And put them in place.

Once it dries it will be surprisingly strong.

I notice now that the turret is going to bee to high. This kind of things happen continuously, so don't be afraid of sometimes throwing everything and start again for the beginning.

By chance this is not going to be one of those cases.

I marked the extra heigh by placing a pen in my desk, raising the turret a little and turning it.

I cut the styrene following the line.

I sand the top a little and continue on.

I cut anoth styrene tire, this is goin to be the sloped armor. I mark it to know the angle its going to need to meet the other pieces.

I cut the angle of each new piece.

We cut another five pieces.

I have glued all pieces in place, put another piece in the base and filled everything with Tamiya's putty. When using this kint of putty you must wet your tools in acetone continuously.

I cover every imperfection with putty. I am trying to get a textured finish, so I apply the putty in a roughly way.

Once dry, I sand the turret, giving it round shaped angles. It is possible that you need to sand too much and open cracks in the angles. Don't worry, I will cover them with more putty.

It is time to add even more putty. I will use now Squadron's putty, wich I feel its a little better for filling spaces. I continue giving the turret an irregular texture.

More sanding...

And we are ready to go on the next step.

Tomorrow I'll put the top, add more texture and a fake welding line.

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Resin Casting Tutorial: Part V (and last)

(versión en Español)

PART I
PART II
PART III
PART IV
PART V

Now that we have the mold ready, we can start casting some pieces.

We'll need: Quick setting utrethane resin, plastic cups, wooden toothpicks, a tool for removing the mix, latex gloves and some polyethylene shopping bags for protecting the table below.

I cover the vibrating tray with polyethylene. The great thing about this plastic is that you can scrape the resin from it once is cured.

You can never get enough protection. This will protect you eyes or glasses in the not so very unlikely event that a resin drop gets close to your eyes.

I start measuring the same volume for components A and B. There is not an exact method to know beforehand how many resin will you use in a mold (never, NEVER, try to measure it with water. A single drop of water will ruin some some kilogrames of urethane resin by itself). So just try to get used at wasting some resin each time you make a mold...

Once the components get in contact the clock is running! You have about 120 seconds before the resin gets too viscous, more than enough. Time will vary depending on the room's temperature. Resin will set quicker at higer temps.

I normaly mix the resin during 20 seconds and then pour it, you should experiment what settings suit you better, but remember that the resing must be completely mixed for better results.

I switch on the vibration tray, put both mold's halves on it and start carefully pouring the resin.

I pour some resin on the other half to avoid bubbles when closing the mold.

Now I pick a toohpick and remove any remaining bubbles. You should be vearing eye protection when doing this. Those bubbles are very small, so you would be forcing your sight, closing to the mold while you are messing with the toothpick so an accident could happen in no time. Remember: "safety first".

The resin is starting to set. you will notice that larger volumes set faster than smaller ones.

When the resin is gooey, I close the mold in a quick motion and gently press the excess resin out. Some call it the "sandwich technique".

You should remember that your urethane resin is very sensible to humidity. It's better to recap the bottles during all those operations.

I am casting another piece here. I made a mistake in the last one. As I did not cover completely the second half with resin, I got some empty spaces to fill with putty later on.

This time I prepared too less resin... Well, this is not a problem.

I just prepare more resin, add it to the molds and repeat the "Sandwich Technique". You'll notice that gentle slope we were talking about when making the mold. Its function is to accomodate a little excess resin wich will be expelled out when pressing the "sandwich".

Here is the completed piece. Nearly perfect! Altough there are some minor bubbles that I'll fill with putty in no time.

And that's it! Hope you find this tutorial useful.

Next time, we'll talk about scratchbuilding techniques. We'll follow a step-by-step process to do a T34-like turret for Warhammer 40K games.

Resin Casting Tutorial: Part IV

(versión en Español)

PART I
PART II
PART III
PART IV
PART V

One of the main concerns when considering resin casting is how to avoid bubbles in the resulting pieces. There are different techniques to help remove bubbles, some of them involving pressure changes. Either for degassing the resin in its liquid form and/or compressing it when is inside the mold, reducing the bubbles size.

Another method, that I personally prefer as I work with open molds (as you probably noticed, I do not build pour spout or air vents, we'll see why in the next part), is to remove bubbles with vibration.

Making something to vibrate is fairly easy. Just unbalance a rotating axle adding some excentrical weight. For doing this I just took an old computer fan, removed the case and blades and glued a nut on a side. Once the motor rotates, the small nut will make it vibrate. I then play with the amplitude of the vibration adding bolts of different lengths. Finally, I glued the fan to the tray.

To build the tray, I bought a cheap wooden frame and fixed the tray with four springs. This is to allow the tray to vibrate freely. I also built a box with polistyrene (I didn't had any wood at hand) and added a switch.

Here it is the final result. It can vibrate big molds like the one in the pic and get rid of more than 90% of the bubbles, although you'll need to remove some of them manually (this is why open molds are so convenient).

You can see below the mechanism working:

I suppose that I will someday build another table, with a more powerful motor and frequency and amplitude controls. But, for the moment being, this small tray does the job.

Next time, we'll see finaly how to cast. See you then!

NEXT

Resin Casting Tutorial: Part III

(versión en Español)

PART I
PART II
PART III
PART IV
PART V

Well, 24 hours have passed and we have now a solid white surface again.

It is time to remove the casting frame and see if the demoulding agent has worked...

Everything works fine:

I remove carefully the rest of the lid:

And that's it, the mold is ready to use:

Those are all the molds needed to do one of my Soviet-themed tanks. About 2500 grames of silicone rubber!

We'll see next about the vibrating tray.

NEXT