Work in Progress

Tyre 332 BC

Posted by Mr. Cryns on 28 Jun 2017, 10:08

Gentlemen, thanks for your technical feedback.

CASTING A RESIN SCALE 1:72 HUMAN FIGURE IN A THREE PART MOULD

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Below is an original sculpt in its mold:

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Pouring hole and vent canals have been cut after the different silicone mould parts have been made. If possible vent canals go upwards, but side- and downwards is possible too because of the pressure injecting of the resin.

All mould parts are covered in a very thin layer of baby powder to make the resin run through the mould more easy and stop air bubbles from getting stuck at the surface of the casted figure:

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To realise the fragile handle of the canteen in its right hand, a 0,3 mm copper wire enforcement is made....

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...and inserted at the right place before the central mould is placed into position again:

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Different kinds of resin are used. Like Smooth-Cast 300 by Smooth-On:

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This resin is white. It has about six minutes of pot life so is useful for casting different moulds in one go. Curing time is about 20 minutes.

Also a very quick version of this product is available. It has only 30 seconds of pot life, forcing the user to work very quick, leaving almost no time for mixing, inserting in the syringe and injecting in the mould. One mistake in this process and the resin is cured too early.
But at the same time the very short curing time of just a few minutes makes it so attractive. A single casting can be made over and over again within a short period using just one silicone mould.

Another brand of resin is Sintafoam 1:1 by Prochima

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The colour is cream or beige. This one is developed for casting miniature models in particular. I like the result of this product better because fewer air bubbles appear during the curing process and the cast is stronger. But this product is more aggressive to human skin and its protection: its eating away rubber gloves and the skin profile on finger tips :shock:

To achieve the human skin tone, resin dye can be added up to 5% of the total resin volume. For a light skin tone 1 or 2% mixed with white resin created a light pink flesh tone. For representing darker wood tone up to 5% is added:

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The large flask is for resin, the small one is dye for translucent silicone moulds.

For the injection of single figures, several figures or larger objects, a collection of syringes is used:

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Injecting is necessary because the 1:72 human figure mould has an internal space that is too narrow for the resin to run properly into and through it and successfully reaching all outward laying tight holes like toes and fingertips by pressing away the air. For bigger scale figures and massive objects like a separate head, this will be a lesser problem.

With a short time 30 seconds pot life resin, there is no time to mix part A, part B and brown dye before pouring it into the syringe since several seconds are needed to press the air out of the tube before injecting in the mould. For that reason part B (less fluid than part A so less quick pouring) and the dye are inserted first with the plug closing the front hole, so no time clock is ticking yet, and these are mixed by shaking. After that part A is added, the tube closed at the back and all is mixed by shaking for about five seconds. Then the plug is removed, the air is pressed out and the tip of the syringe inserted into the pouring hole of the silicone mould.

For syringes without a plug, one can be cut of wood (centre) and should be marked with some colour paint (green top) not to confuse it with pieces of trash wood on the working desk ending in the dustbin the same day.

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The first test cast reveals imperfections of the silicone mould. The air bubble in the elbow reveals a 'dead spot' where the air has no possibility to leave the mould:

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Also the canteen shows such a 'dead spot':

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From the deepest end of such 'dead spot' a vent canal is pierced and widened by filing, using a round, sharp pointed micro-file:

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The air canal runs to an outside surface of the mould that will stay open during casting and will not be covered by the mould-supporting hardboard sheets:

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The original vent canals are visible together with the pouring hole on the dividing line of both outer mould halves. The new drilled canal is on top. It has been cut bigger on the outside with a hobby knife in a later stadium of the casting process to serve as a secondary pouring hole: the inside hollow space of the canteen was too far away from the original pouring hole. Resin leaked out from all vent canals before it was able to fill up the canteen space.

Hardboard and rubbers keep the mould together and equalise pressure.
Pressure can be increased by winding the rubbers an extra time around the mould or by adding more rubbers. Too much pressure creates deforming and misfitting mould halves.

After cleaning all mould parts these are covered in baby powder again and assembled for casting.

Fresh resin is injected until it runs out of all vent canals: first visible on the bottom and side openings and finally on the top side of the mould:

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Only the new cut vent canal did not show any resin coming up at all. That meant it was out of the 'pressure zone' and it was filled up from the outside by injecting some extra resin through this hole.

After curing time:

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An other mould:

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The excessive flash looks terrible. Its mainly a result of syringing with pressure. But at the same time, the creation of flash helps to remove the air trapped into the mould:

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Air bubbles are not visible anymore. There still are, but inside the resin, not on the surface of the figure, because of the use of baby powder:

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As soon as the flash is removed with a hobby knife, the air inside of the resin gets visible:

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Some times the air bubbles are fewer and painting the figure will fill up those micro holes easily anyhow.

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The air bubble problem is not only because of air trapped in the mould.
Its also because during the curing process, new air is produced inside the resin and that has to come out as well. Usually this will float upwards and leave through the vent and pouring openings. But the smaller and narrower the mould is (scale 1:72!!!) the more difficulties the air has to escape.

Other ways can be helpful too to let air escape from the resin:
- Wait a few minutes before injecting the resin into the mould. This enables the air produced during the curing process to float upwards and leave the resin before its injected. This can be done when the resin is in the syringe with the back still opened. Or it can be done before its poured into the syringe. Not possible with 30 seconds pot life resin.
- Shake or drill the mould after resin is inside.
- Squeeze it softly from both sides when resin is inside.

The air bubble problem can be solved best in a professional way by using a de-gassing machine.

An example of a two part silicone mould:

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Three different casting procedures were tried as a test:

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Brown: no vent canals, no baby powder
Pink: vent canals only, no baby powder
White: both vent canals and baby powder

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Mr. Cryns  Netherlands

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Posted by sberry on 28 Jun 2017, 12:00

All this continuous experimenting and improving the procedure, that's the road to perfection! The effects of this constant effort can be seen so nicely in the last of the three casted figures.
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Posted by Kostis Ornerakis on 28 Jun 2017, 15:23

Wonderful my friend! :notworthy: :notworthy: :notworthy:
I'll have to try the baby powder tip.
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Kostis Ornerakis  Greece
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Posted by Mr. Cryns on 30 Jun 2017, 10:31

Thank you my dear friends.

Kostis Ornerakis wrote:I'll have to try the baby powder tip.

Yes you should. This suggestion came from Gerard Boom.
But I understood its a widely used technique in resin casting.

It works like this:
Scatter some powder on all different mould parts. The powder will not be spread out equally over its surfaces at all when doing this. So for that reason, keep both moulding halves towards each other in your hands and smash your hand palms to each other while your fingers keep the moulds just a little bit apart from each other so the moulds do not hit each other in full speed and force. By doing this you create a powder dust cloud between both mould halves. The excessive powder will leave the mould and jumps over to the other one. The dust cloud creates that very thin layer of powder covering all internal (but also external) parts of the mould.

In case you have a single part mould (which you have ;-) ) throw some powder inside, open the incision cut in the silicone mould as wide as possible, and hit the mould on the table so the powder sinks down. Turn the mould and hit it on the table with the opening downwards so all excessive powder falls out.
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Mr. Cryns  Netherlands

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Posted by Kostis Ornerakis on 30 Jun 2017, 17:57

Mr. Cryns wrote:In case you have a single part mould (which you have ;-) ) throw some powder inside, open the incision cut in the silicone mould as wide as possible, and hit the mould on the table so the powder sinks down. Turn the mould and hit it on the table with the opening downwards so all excessive powder falls out.


First of all thank you again as the it already worked. :notworthy:
I did something similar. I dropped enough powder inside the mould, then shaked so dust got everywhere and finally I blowed gently inside while the mould was wide open. :-D
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Kostis Ornerakis  Greece
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Posted by FredG on 30 Jun 2017, 18:09

Perhaps a talcum powder puffer would be helpful?

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FredG  United Kingdom
 
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Posted by Mr. Bos on 27 Jul 2017, 09:57

With great pleasure I have started to built the Greek merchant ship.
I am using the drawings found in this topic.

But I have two questions.

In the picture 'rigging of the mast' there goes a rope from mast to bow.
But, with this rope attached, there is little space to attach the sail, it will hang a bit to low.
In the picture 'rigging of the halyards and anchors' the rope isn't drawn at all.
How is this intended?

Where do I have to attach the end of the ropes from the low corners of the sail?
To the center beams?

It is a great ship, with a lot of detail :-D
Mr. Bos  Netherlands
 
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Posted by Kostis Ornerakis on 27 Jul 2017, 13:46

Dear Mr. Bos,
Here: viewtopic.php?f=11&t=20765&p=226820#p226820
I work with another Mr. Cryns boat. In the 2nd page there is a post from Mr.Cryns which I believe is helpful. :-D
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Kostis Ornerakis  Greece
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Posted by Mr. Cryns on 02 Aug 2017, 13:12

Dear Mr. Bos,

I am very delighted to hear you are building one of those ancient ships too.
Please feel free to post pictures of its development in this thread.
Or, of course, in a new one if you prefer that.

Thanks for directing those questions at me.

Mr. Bos wrote:In the picture 'rigging of the mast' there goes a rope from mast to bow. But, with this rope attached, there is little space to attach the sail, it will hang a bit to low.

This may be a beginners mistake of myself.
I did not finish any of those ships myself including its rigging.
You are doing that for me now so you add to the development of the model :-D

First of all for the right English rigging names we can use this image:

http://www.mediterrraneancom.org/initia ... ion720.jpg

Now when in full wind, the sail will be pressed towards the forestay (front cable) thus creating a deep fold as can be seen in the fore-sail of the Olympias trireme.

http://italianalmanac.org/2011/ship.jpg

Maybe the technique presented to us by Kostis using a hairdryer to soften the resin sail and thus re-shaping it before getting cold and hard again makes it possible to add such fold. I definitely will try this at home.

Also the forestay will be pushed up when its loosened a little (in Dutch sailor's slang: 'laten vieren' ), making a bend, as can be seen here and so you do not have to change the shape of the sail:

http://www.mediterrraneancom.org/initia ... /styled-4/

Mr. Bos wrote:In the picture 'rigging of the halyards and anchors' the rope isn't drawn at all. How is this intended?

That is common use in modelshipbuilding manuals:
not all rigging lines in one pictures, that will make it too complicated.
But: separate pictures for separate parts of the rigging system.

Mr. Bos wrote:Where do I have to attach the end of the ropes from the low corners of the sail? To the center beams?


Thats a question I expected already and Kostis faced it too.
It all depends on which sail you use (full sail or reefed sail) and which way it hangs: towards the front or one of the sides.
I imagine those ancient sailors to change the fastening spots of those 'sheets' (schoot of schoten in Dutch) every time the wind is changing or the direction of the route is changed. It has to be adjusted again and again by them.
Because of the sails size, I think the best place to fasten those sheets are to the horizontal beams on both inner sides of the hull or at the base of the ten stakes holding up the board canvases but as you said it could be the center beams holding up the mast, too.

Good luck with the building !
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Mr. Cryns  Netherlands

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Posted by Mr. Bos on 10 Aug 2017, 22:04

Hallo Mr. Cryns,

After some extra work my problems solved themselves.

Mr. Bos wrote:
In the picture 'rigging of the mast' there goes a rope from mast to bow. But, with this rope attached, there is little space to attach the sail, it will hang a bit to low.


It seemed that the sail would hang to low, but it doesn't :-)
With some glue the rope now even supports the sail.

Mr. Bos wrote:
Where do I have to attach the end of the ropes from the low corners of the sail? To the center beams?


Mr. Cryns wrote:
Because of the sails size, I think the best place to fasten those sheets are to the horizontal beams on both inner sides of the hull or at the base of the ten stakes holding up the board canvases but as you said it could be the center beams holding up the mast, too.


The center beams worked good. ;-)

When finished I surely post some pictures in this topic.

Thanks for the responses!
Mr. Bos  Netherlands
 
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Posted by Mr. Cryns on 12 Oct 2017, 12:43

Dear friends and followers of this topic,

This summer the continuation of the Tyre 332 BC topic has been transferred to the 'Geschichte in Miniaturen' forum:

http://www.geschichte-in-miniaturen.de/ ... f=32&t=251

Over there we focus on 1:72 scale historical diorama building, research and 1:72 non-plastic figurine production. All of my work since june 2017 can exclusively be seen over there. The website is both in German and English so please have a look in case you are curious:

For now, thanks a lot to all of you who supported, feedbacked and attributed to my work that was published here in the past two years.
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Mr. Cryns  Netherlands

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Posted by FredG on 12 Oct 2017, 19:48

Thanks for the heads-up ;-)
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