I discovered this synthetic plaster ( called “Zellan” or “Staturoc” ) in a art store. It is very fine and reproduces precisiously every details. Use 1kg of “Zellan” for 20-25g/cl of water; it makes a very liquid mix that you have to pour it on the shape you want to reproduce. Open time is 6 minutes and it is totaly dry in only 12 minutes.Once dry, it is very hard and gets a very high mecanical strength.
I put some wax layers on it and the fiberglass releases quiet easely.
I add some pictures of my works. I used it to create the female molds of the deck and the cockpit of my Open 60.
Next time I will try to pour the female mold of my ACC120. I’ll show you if it works…
I’ve also used it to pour the bulb in one piece of another boat. The synthetic plaster mold didn’t broke when I poured the lead and there was no accident… but the bulb was small ( about 600g ) and I don’t exactly know the technical specifications of this material.
SO I DON’T RECOMMAND TO ANYONE TO USE THIS MATERIAL TO POUR LEAD BULBS. PREFER “RTV HIGH TEMPRATURE” IN ORDER TO AVOID A TRAGIC ACCIDENT.
Last thing: the cost. You can find it between 12€ and 25€ for 5kg here in France. So the cheapest I found cost 2.40€ for 1kg.
I’m interested in this also for female mould making my new 120, dries super fast so you have to be quick one thing I remember when Jim made his mould with white cemet is that he used chopped fibre to strengthen mould binding, wondered if it need to consider same for this materail.
I’m trying Latex stretched over male mould also and will post results also.
Claudio: I don’t know about this material density yet. I don’t have enough material to pour a dm3 (with the ratio 20-25 cl per kg, I should need 2kg of synthetic plaster, at least… ), but I’ll go find some more today and will inform you in few hours.
Alan: You’ve got all the time you need. Once the mould or shape is ready, you have to estimate the volume of material you need ( with water…or at rough guess. If you need more,you can add it after a little while.), then put the water you need in a bucket or a bowl, add delicatly the synthetic plaster. When the water is almost absorbed, mix it. Now you’ve got 6 minutes to pour it on your male mould…
I don’t think you need to add chopped fibre to reinforce. This is a moulding material and looks very strong. Is also very liquid when you pour it and I think the fiber should float in surface, so…
I use “Hydrostone” (similar to “Ceramical”) for my lead molds. This material is a gypsum product that falls somewhere between plaster and cement. Very hard when cured and produces fine detail, I’ve used it for air release molds for my art tile production. A press mold with Hydrostone will produce sharp detail for over 1,000 reps under 5,000 pounds of pressure.
For bulbs casting I do take the precaution of using wire mesh reenforcement in the mold halves, less for strength but to hold the mold intact in case it should crack. I’ve cast bulbs up to 10 pounds with no breakage though so I have confidence in this material. It is available from sculpture and pottery materials suppliers as well from some masonry suppliers.
It’s done Claudio : a cubic decimeter “stricto sensus”.
While drying, the synthetic plaster gets quiet hot, and I noticed that its weight was going down as it was going colder.The steam going out of the mix.Once cold, it stabilised at 2090g.
Concerning the mix quantity, I was quiet good: I used 2kg of Staturoc for 50cl (500g) of water and I poured nearly the whole mix.
Here some pictures, one showing my quality control director at work !
Tell me what you think about pouring lead bulbs with this material… just in case. ( As it is smocking/steaming while getting cold, I understand that once cold, it must remain no water in the mould.So the hot lead won’t transform the potentiel water at liquid state in steam and produce the mould explosion… Hope you understood. )
I don’t know “Hydrostone”.Is it a synthetic product ? a gypsum derived ? a cement derived ?
I’ll try to find some here in France. Could you tell what brand is commercializing it ?
The main advantage of “Staturoc” (after its apparent strenght and its fineness) is its drying time (only 12 minutes)
Thank you very much Paulin,
Hi will calculate the pressure weight onto an empty hull laminated with 3 layers of 105g/m² glass tissue. I would like to knows if there is a potential risk of skin/form deformation
ClaudioD
Concerning a potential risk for skin:
nothing is mentioned. But I touched it without gloves…and nothing appeared on my hands so far, so…
Concerning a form deformation :
If you’re talking about the mould itself : no way ! Once dry, this material seems hard as rock.
If you’re talking about the shape you want to reproduce, I don’t know; to create mine I used polystyren foam, laminated with 2* 80g/m² fiberglass, and it didn’t appeared any deformation due to weight or warmth. For the rest…?
I don’t understand why do you want to calculate the pressure weight on a empty hull… Isn’t it better to work from a wood or polystyrene master ? Must have a good reason…
Of course Paulin, there is around Italy a hull made in ABS years ago.
No master, no drawings, no mould. The idea is to put it into a box and then pouring the synthetic plaster onto. The actual ABS hull still equipped with deck may still deform under the plaster weight ! Who knows ?
That the reason for the question, being the use of the plaster a very fast and cheap solution instead of hours to recover the frames profiles and start building a master…etc.
Thank for your informations
Cheers
ClaudioD
What about injecting polyurethane foam inside the ABS hull in order to reinforce it before pouring the synthetic plaster ? the original hull will be out of order, but you’ll have the possibility to get several prints.
Instead of wax you can use “lithium white grease” (3en1) to protect the ABS and remove it easely from the plaster… (have a try before, I don’t know on ABS)
Interesting concepts … take master hull desired, fill with this “plaster”, remove after cure and flip over (deckside down). Place on plywood panel and lay styrene panel of the plaster “plug” and heat styrene panel until it deforms, and sags down over top of plaster “plug”. Let cool and remove from plg - trim off bow and stern to length, add a flat bow plate for bow bumper and fabricate a styrene panel for transom. Probably need a bulkhead or two inside to keep deck form along gunwales. You end up with a vacuum formed hull without the vacuum - just let nature and gravity do their thing.
May give this idea a try this winter when nothing else to do when snow has been shoveled. May be possible to form each side of a multihull hull/float and then glue together. Hmmmmm - an RG65M cat perhaps?
if I have a male “plug” of foam - will the “plaster” stick - do I need to coat foam with epoxy to keep the material from sticking - or does the male part easily remove from the mold?
Basically I want to “create” a female mold of the hull, from which I can layup glass or heat styrene to form to the shape. Just worried so I don’t spoil the foam plug.
Would be worst since the polyurethane foam will spread randomly producing a variable pressure and deforming the hull shape more than a homogeneous gravity effect from plaster especially if retained by the deck .
Cheers
ClaudioD
I used “extruded polysthyrene foam” panels (used in floor insulation) that get more density and strenght than “expansed polysthyrene” panels (white panels with little balls inside) that it seems to be used on your picture.
I tried both technic : for my deck and cockpit plug I’ve coeted the foam with epoxy + FG, then applied mastic, sanding and wax or white grease coated.This way, the plug remose very easely.Fiberglass coating may not necessery.
The other way (used to pour the cube) using primary foam, it was a little harder to remove but there have been no damages ( notice the mold was in multiple pieces, each face fitted together and the shape was quiet simple )
Try it before !
I get Hydrostone here in New York from Ceramic Supply in Lodi, NJ. I believe it is also available from The Compleat Sculptor here in the city, more expensive from the later source. Ceramic supply houses are the best source because it is used a lot in press mold production of ceramic ware. It is an esoteric material so home stores like Home Depot or Lowes are not going to have it. In fact my local Lowes doesn’t carry Plaster of Paris, just modified plaster products for wall repair and smoothing that don’t pour well and stay in a putty consistency for a long time.
The mixing setting time is not anywhere near the 12 minutes of Paulin’s material. In fact Hydrostone’s mixing time takes forever to trail and get to pouring stage (about 20 to 30 minutes). Spray release for plaster molds on the plug. Demold time is at least an hour. I leave the new casting to dry slowly, elevated on dowels, on a sunny window sill for a week or so. Preheat the mold before casting lead to avoid too much shock.
For all the inconvenience of the casting process the mold is as strong as any I’ve seen short of aluminum ones. I don’t do production level bulb casting so an aluminum mold would be an extravagance. For a one off casting of a new or experimental shape there is always sand casting, but that is another story.
here are the pictures of a “staturc” bag. Brand name is “Rougier & plé” ( french company ) and another brand : “Voss chemie” ( german I think ) that commercialize another synthetic plaster called “Zellan” ( same material ).
You should search in art and moulding shops… Must find the same product under other brand.
one thing I remember when Jim made his mould with white cemet is that he used chopped fibre to strengthen mould binding, wondered if it need to consider same for this materail.