OK, Dave, it took a few days of part-time work, but here's the second part of the information you asked for, this one dealing with GRP hull fabrication tooling. Enjoy.
TOOLS FOR GRP LAY-UP (HULL MAKING)
Fiberglass hulls are laid-up within large multi-part tools (called molds in some circles). Typically a set of tools comprises an upper-lower or left-right set for the hull and a left-right set for the sail. Regardless of tool type, the end game is the same: production of thin walled, strong fiberglass structures.
Glass reinforced plastic (GRP) hulls and sails are preferred over other substrates for three main reasons:
1. GRP's very thin wall thickness -- the less water the above waterline structures displace, the less ballast tank you need to get the model up to the designed waterline (only a consideration for wet-hull type r/c submarines)
2. strength
3. the ability of the initial gel-coat laminate to capture the most complicated of detail within the tools cavity without the need to resort to exotic pressure differential equipment (pressure/vacuum vessel)
The hull-sail tooling can be GRP hard-shell, cement, a hybrid of rubber and GRP (mother-glove mold), clay, cuttlefish bone, heavily filled resin, or any number of other materials that can capture, in negative, the form of a master (pattern, or model if you will).
However, this discussion will be limited to the cement, GRP hard-shell, and hybrid mother-glove mold type tools.
GRP HARD-SHELL TOOL AND SPACE STATION TORUS GRP PART LAY-UP
The traditional (most often used) type is the GRP hard-shell tool. It's both cheap and easy to make.
(Surprisingly, I can't find any pictures in my massive collection of pictures of a hard-shell GRP tool applicable to submarines. But, as a stand-in I present these shots showing the fabrication of the master, tool, and model parts of a 'wheel' type space station model, based on an effects miniature used in the old George Pal movie, The Conquest of Space).
The first picture is of the finished space-station model fabricated principally from GRP -- those parts fabricated in a hard-shell GRP tool of unique form. The second shot is a frame enlargement from the actual film, The Conquest of Space. A magnificent movie that does not get the credit it deserves.
Though a bit outside the preview of this discussion, I thought you would like to see how I gave form to the master of the torus. If you will, the 'hull' of the space station. The process is called screeding -- giving form to a pliable mass, in this case warm modeling clay initially, followed by an over-coat of uncured automotive two-part filler.
A circular screeding blade swings around a fixed pivot over the mold board. The blade gives form (half a torus) to the clay as it's pushed in a circle about the mold board -- this is described as circular screeding.
Note the larger semi-circular blade at the top. This one is used to give form to automotive filler, which goes over the clay. The clay is there to reduce the amount of filler needed to make the torus half-master. The filler formed spoke elements were linearly screeded on another board and transferred to the torus to make up the space-station half-master. The central hemisphere was turned from solid Renshape.
The space-station master and mold board was first given several coats of wax, buffing between coats. Finally, the entire master and mold board was spray coated with polyvinyl alcohol (PVA), a water soluble film that serves as a barrier between the soon to be applied epoxy laminating resin and the waxed surface of the master and mold board. This type barrier is referred to as a mold-release.
This mold-release step, and the products used, are the same as used between the submarine master and its mold board and the hard-shell tool (mold) that will be laid up over them. And, conveniently, the same wax and PVA are used as part-release agents forming a barrier between tool and GRP model parts.
In this shot you see the GRP space station hard-shell tool under a space-station GRP part. The broken popsicle sticks and hammer were used to pry the GRP part off the GRP tool. An ugly affair but no damage resulted during the 'liberation' effort. Once a second GRP part is made, they are trimmed to the flange face of the tool and bonded together forming the complete torus and spoke assembly that represents the space stations hull.
With the exception of the dumb-bell central parts and white-metal mirror support pieces, the entire model was constructed of very thin walled GRP.
How thick (wall thickness) should the r/c submarine GRP hull be? We want it thick enough to have the strength to survive normal handling, and moderate collision forces. But we don't want it so thick that the structure above the models waterline displaces an unreasonable amount of water. Balancing these two requirement, strength and displacement takes some though and experiment.
My considerable experience in the field has taught me to keep the nominal wall thickness of a GRP hull at about 1/16" - 1/8" thick. 1/16"thick for small models up to 50" in length. And 3/32" - 1/8" thick for the longer model hulls.
The thickness of the gel-coat and number and weights of fiberglass cloth/mat laminates is driven by the geometric complexity of the tool cavity. The more complicated the geometry, the thicker the gel-coat(s), the more laminates of light-weight weaved glass. A simple hull like the DELPHIN only required one gel-coat, and two laminates of 15-ounce glass mat.
Above is a test I did for a simple of geometry 70" long submarine hull. The nominal wall thickness was to be 1/8", built up from the minimum number of laminates I could without having the saturated glass bunch up and produce the dreaded air voids. Several test samples were laid up from scrap material into the most complicated section of the tool -- the objective to work in the gel-coat and glass laminates, finding the heaviest glass weave and mat that would wet out completely without producing air voids. On this particular model I found that a gel-coat, followed by one laminate of 4-ounce cloth, a laminate of 10-ounce cloth, and a laminate of 15-ounce mat produced a GRP structure able to produce void free parts and achieve the 1/8" wall thickness goal. This established, the required number, weight, and type fiber glass sheets were cut out, and work laying up the GRP hull halves began.
CEMENT TOOL AND HULL LAY-UP
Darrin Hataway -- an excellent professional model builder, and responsible for several of the excellent OTW hull kits -- gave me an old cement tool he made for a large scale model of the WW-2 era German DELPHIN one-man submarine. This tool was made from a fine grained type cement, sometimes sold as 'hydro-stone' or dental cement. This type mold making material is good for producing tools whose surface is not festooned with high relief engraved lines or plating, as the cement is relatively weak in shear and such details would break off with usage. However, as a quick-and-dirty, cheaply made tool for un-detailed GRP hull fabrication, it's perfect. Owing to the rigid nature of the material there can be no negative draft to the cavities, and zero draft is to be avoided or you'll never be able to de-mold the laid up GRP part after lay-up.
I laid up the upper and lower GRP hull pieces in the tools. The two hull parts were then cut (lower hull bow and upper hull stern) and re-assembled and glassed back together to achieve the Z-cut so favored by those assembling GRP type r/c submarines of the wet-hull type.
Darrin's tools arrived already saturated with part-release wax. It was a simple matter to lay down a fresh coat of wax, buff it out, and spray in three coats of PVA barrier film -- this readied the tools for gel-coat and GRP lay-up.
Gel-coat is simply a thickened laminating resin, laid down without glass re-enforcement. It's the first layer of material to go into the tools cavities that forms the eventual model part. Therefore the gel-coat becomes the surface of the GRP model part. You want this layer (the gel-coat) to be strong, and able to wet out every portion of the tools cavities -- the primary job of the gel-coat is to capture all the details present in the tools cavity and to produce a softened, curved (fillet) transition between sharply angles projections within the cavity, over which the laminations of fiberglass cloth and mat will go. Sometimes multiple coats of gel-coat are applied to areas of sharp relief to further fillet the area so subsequent laminations of glass won't be stressed to the point of de-laminating and producing voids.
A simple hull form, like the DELPHIN, results in hull tools that permits laying in relatively heavy material over the minimal thickness of gel-coat. Glass mat or weaved cloth is measured by weight of the square-yard. In this case I went right in there with 10-ounce weaved cloth, three layers (laminates).
For economies sake -- particularly if you have many laminates to build up and/or you are going to make multiple copies of GRP parts -- it's a good practice to trim one piece of the glass cloth to make a tight conformal fit within the tool, mark off where the cloth meets the tools flange face, remove it, set it over a big piece of poster-board, and trace its outline with one-inch more boarder for safeties sake. You can see the DELPHIN's orange poster board glass marking template in foreground -- used to cut to mark out all subsequent glass cloth pieces for cutting. This saves material and time doing it this way.
GRP HARD-SHELL TOOL AND HULL AND SAIL LAY-UP
My boss, Mr. Caswell, purchased tooling for a 1/72 M-1 submarine kit and asked me to evaluate it by laying up a hull for him and me. This tooling is of the classic GRP hard-shell type. However, a bit unusual in that there is no egg-crate support structure backing to prevent these long items from warping over time. But, I found to my surprise that the GRP model parts I pulled from these tools fit near perfectly. So, no egg-crating, no problem.
Once the initial fit of glass cloth bits to fit the tool is made and that cloth laid out over some pink poster board (pink???) and the templates made, the templates are used to cut out all the pieces of cloth and mat needed to achieve a full laminate.
The perfect cutting tool for glass fiber sheet is a pizza-knife over a plywood cutting board. You lay the cloth over the cutting board, use the template to mark out the outline of the cloth/mat, and then cut the laminate out with the circular-knife/pizza-knife. The knife is very easy to steer and won't pull and snag the tough glass material as an X-Acto blade or scissors would.
Here's the M-1 tooling. Whoever did this work is damn good at it: thick, wide flanges; good tool design (optional superstructure stand-alone tool or superstructure incorporated in the hull tools); and the sail tools were indexed to clamp together permitting me to bond the two halves together in-tool. A joy to work with!
Here you see all tooling after receiving their third spray coating of PVA. I use the heat gun between layers of PVA to speed up the work.
These tools came to us already built up with wax, so all I had to do was lay down and buff up my own wax layer, spray on three coats of PVA and get to the gel-coat. Now, there are various fillers you can add to laminating resin (by the way, I like the West System laminating epoxy laminating resins -- I use the 'fast' one) to thicken it up so it will build fillet between harsh angled items in the tool cavity. On the M-1 there are near zero draft angles between the hull and superstructure, and the hull and deep keel -- these areas required more than one coat of gel-coat to soften their edges. If you fail to do this, even the lightest fiberglass cloth will bunch up and leave awful air voids.
The most difficult glass work is the sail. Lots of gel-coat, and many layers of 4-ounce cloth, cut into small bits so the class could negotiate the tight fillets without bunching.
Once the GRP sail part had cured hard, it was popped out of its tool and the excess GRP that extended past the flange line (obvious on the parts, so no need to mark it while still in the tool) ground off. The flange and cavities of the two tool haves were then waxed up in preparation of the next step.
The GRP sail halves were re-inserted into their tools, and the two indexed tools assembled, putting the edges of the GRP parts up tight against one another and in perfect registration. It was then a simple matter of wetting the seam area from the inside of the part and sticking a strip of glass in there to back up the seam, turning the assembly into a one-piece sail. Pretty slick took design!
The open sail tool with the three securing bolts used to hold the assembled tool halves together as the GRP sail halves are bonded into one unit.
Between laminates of gel-coat, glass cloth and/or mat I sand the surface of the hardened laminate while it's in the tool to knock down bumps and give plenty of tooth for the next layer of resin saturated glass to grab onto. There is no cohesion at work between a cured hard surface bonded with epoxy or polyester resin to the next laminate, so the agent of 'stick' is strictly mechanical and adhesive in nature.
A completed M-1 GRP hull half part next to the tool that gave it form.
TOOLS FOR GRP LAY-UP (HULL MAKING)
Fiberglass hulls are laid-up within large multi-part tools (called molds in some circles). Typically a set of tools comprises an upper-lower or left-right set for the hull and a left-right set for the sail. Regardless of tool type, the end game is the same: production of thin walled, strong fiberglass structures.
Glass reinforced plastic (GRP) hulls and sails are preferred over other substrates for three main reasons:
1. GRP's very thin wall thickness -- the less water the above waterline structures displace, the less ballast tank you need to get the model up to the designed waterline (only a consideration for wet-hull type r/c submarines)
2. strength
3. the ability of the initial gel-coat laminate to capture the most complicated of detail within the tools cavity without the need to resort to exotic pressure differential equipment (pressure/vacuum vessel)
The hull-sail tooling can be GRP hard-shell, cement, a hybrid of rubber and GRP (mother-glove mold), clay, cuttlefish bone, heavily filled resin, or any number of other materials that can capture, in negative, the form of a master (pattern, or model if you will).
However, this discussion will be limited to the cement, GRP hard-shell, and hybrid mother-glove mold type tools.
GRP HARD-SHELL TOOL AND SPACE STATION TORUS GRP PART LAY-UP
The traditional (most often used) type is the GRP hard-shell tool. It's both cheap and easy to make.
(Surprisingly, I can't find any pictures in my massive collection of pictures of a hard-shell GRP tool applicable to submarines. But, as a stand-in I present these shots showing the fabrication of the master, tool, and model parts of a 'wheel' type space station model, based on an effects miniature used in the old George Pal movie, The Conquest of Space).
The first picture is of the finished space-station model fabricated principally from GRP -- those parts fabricated in a hard-shell GRP tool of unique form. The second shot is a frame enlargement from the actual film, The Conquest of Space. A magnificent movie that does not get the credit it deserves.
Though a bit outside the preview of this discussion, I thought you would like to see how I gave form to the master of the torus. If you will, the 'hull' of the space station. The process is called screeding -- giving form to a pliable mass, in this case warm modeling clay initially, followed by an over-coat of uncured automotive two-part filler.
A circular screeding blade swings around a fixed pivot over the mold board. The blade gives form (half a torus) to the clay as it's pushed in a circle about the mold board -- this is described as circular screeding.
Note the larger semi-circular blade at the top. This one is used to give form to automotive filler, which goes over the clay. The clay is there to reduce the amount of filler needed to make the torus half-master. The filler formed spoke elements were linearly screeded on another board and transferred to the torus to make up the space-station half-master. The central hemisphere was turned from solid Renshape.
The space-station master and mold board was first given several coats of wax, buffing between coats. Finally, the entire master and mold board was spray coated with polyvinyl alcohol (PVA), a water soluble film that serves as a barrier between the soon to be applied epoxy laminating resin and the waxed surface of the master and mold board. This type barrier is referred to as a mold-release.
This mold-release step, and the products used, are the same as used between the submarine master and its mold board and the hard-shell tool (mold) that will be laid up over them. And, conveniently, the same wax and PVA are used as part-release agents forming a barrier between tool and GRP model parts.
In this shot you see the GRP space station hard-shell tool under a space-station GRP part. The broken popsicle sticks and hammer were used to pry the GRP part off the GRP tool. An ugly affair but no damage resulted during the 'liberation' effort. Once a second GRP part is made, they are trimmed to the flange face of the tool and bonded together forming the complete torus and spoke assembly that represents the space stations hull.
With the exception of the dumb-bell central parts and white-metal mirror support pieces, the entire model was constructed of very thin walled GRP.
How thick (wall thickness) should the r/c submarine GRP hull be? We want it thick enough to have the strength to survive normal handling, and moderate collision forces. But we don't want it so thick that the structure above the models waterline displaces an unreasonable amount of water. Balancing these two requirement, strength and displacement takes some though and experiment.
My considerable experience in the field has taught me to keep the nominal wall thickness of a GRP hull at about 1/16" - 1/8" thick. 1/16"thick for small models up to 50" in length. And 3/32" - 1/8" thick for the longer model hulls.
The thickness of the gel-coat and number and weights of fiberglass cloth/mat laminates is driven by the geometric complexity of the tool cavity. The more complicated the geometry, the thicker the gel-coat(s), the more laminates of light-weight weaved glass. A simple hull like the DELPHIN only required one gel-coat, and two laminates of 15-ounce glass mat.
Above is a test I did for a simple of geometry 70" long submarine hull. The nominal wall thickness was to be 1/8", built up from the minimum number of laminates I could without having the saturated glass bunch up and produce the dreaded air voids. Several test samples were laid up from scrap material into the most complicated section of the tool -- the objective to work in the gel-coat and glass laminates, finding the heaviest glass weave and mat that would wet out completely without producing air voids. On this particular model I found that a gel-coat, followed by one laminate of 4-ounce cloth, a laminate of 10-ounce cloth, and a laminate of 15-ounce mat produced a GRP structure able to produce void free parts and achieve the 1/8" wall thickness goal. This established, the required number, weight, and type fiber glass sheets were cut out, and work laying up the GRP hull halves began.
CEMENT TOOL AND HULL LAY-UP
Darrin Hataway -- an excellent professional model builder, and responsible for several of the excellent OTW hull kits -- gave me an old cement tool he made for a large scale model of the WW-2 era German DELPHIN one-man submarine. This tool was made from a fine grained type cement, sometimes sold as 'hydro-stone' or dental cement. This type mold making material is good for producing tools whose surface is not festooned with high relief engraved lines or plating, as the cement is relatively weak in shear and such details would break off with usage. However, as a quick-and-dirty, cheaply made tool for un-detailed GRP hull fabrication, it's perfect. Owing to the rigid nature of the material there can be no negative draft to the cavities, and zero draft is to be avoided or you'll never be able to de-mold the laid up GRP part after lay-up.
I laid up the upper and lower GRP hull pieces in the tools. The two hull parts were then cut (lower hull bow and upper hull stern) and re-assembled and glassed back together to achieve the Z-cut so favored by those assembling GRP type r/c submarines of the wet-hull type.
Darrin's tools arrived already saturated with part-release wax. It was a simple matter to lay down a fresh coat of wax, buff it out, and spray in three coats of PVA barrier film -- this readied the tools for gel-coat and GRP lay-up.
Gel-coat is simply a thickened laminating resin, laid down without glass re-enforcement. It's the first layer of material to go into the tools cavities that forms the eventual model part. Therefore the gel-coat becomes the surface of the GRP model part. You want this layer (the gel-coat) to be strong, and able to wet out every portion of the tools cavities -- the primary job of the gel-coat is to capture all the details present in the tools cavity and to produce a softened, curved (fillet) transition between sharply angles projections within the cavity, over which the laminations of fiberglass cloth and mat will go. Sometimes multiple coats of gel-coat are applied to areas of sharp relief to further fillet the area so subsequent laminations of glass won't be stressed to the point of de-laminating and producing voids.
A simple hull form, like the DELPHIN, results in hull tools that permits laying in relatively heavy material over the minimal thickness of gel-coat. Glass mat or weaved cloth is measured by weight of the square-yard. In this case I went right in there with 10-ounce weaved cloth, three layers (laminates).
For economies sake -- particularly if you have many laminates to build up and/or you are going to make multiple copies of GRP parts -- it's a good practice to trim one piece of the glass cloth to make a tight conformal fit within the tool, mark off where the cloth meets the tools flange face, remove it, set it over a big piece of poster-board, and trace its outline with one-inch more boarder for safeties sake. You can see the DELPHIN's orange poster board glass marking template in foreground -- used to cut to mark out all subsequent glass cloth pieces for cutting. This saves material and time doing it this way.
GRP HARD-SHELL TOOL AND HULL AND SAIL LAY-UP
My boss, Mr. Caswell, purchased tooling for a 1/72 M-1 submarine kit and asked me to evaluate it by laying up a hull for him and me. This tooling is of the classic GRP hard-shell type. However, a bit unusual in that there is no egg-crate support structure backing to prevent these long items from warping over time. But, I found to my surprise that the GRP model parts I pulled from these tools fit near perfectly. So, no egg-crating, no problem.
Once the initial fit of glass cloth bits to fit the tool is made and that cloth laid out over some pink poster board (pink???) and the templates made, the templates are used to cut out all the pieces of cloth and mat needed to achieve a full laminate.
The perfect cutting tool for glass fiber sheet is a pizza-knife over a plywood cutting board. You lay the cloth over the cutting board, use the template to mark out the outline of the cloth/mat, and then cut the laminate out with the circular-knife/pizza-knife. The knife is very easy to steer and won't pull and snag the tough glass material as an X-Acto blade or scissors would.
Here's the M-1 tooling. Whoever did this work is damn good at it: thick, wide flanges; good tool design (optional superstructure stand-alone tool or superstructure incorporated in the hull tools); and the sail tools were indexed to clamp together permitting me to bond the two halves together in-tool. A joy to work with!
Here you see all tooling after receiving their third spray coating of PVA. I use the heat gun between layers of PVA to speed up the work.
These tools came to us already built up with wax, so all I had to do was lay down and buff up my own wax layer, spray on three coats of PVA and get to the gel-coat. Now, there are various fillers you can add to laminating resin (by the way, I like the West System laminating epoxy laminating resins -- I use the 'fast' one) to thicken it up so it will build fillet between harsh angled items in the tool cavity. On the M-1 there are near zero draft angles between the hull and superstructure, and the hull and deep keel -- these areas required more than one coat of gel-coat to soften their edges. If you fail to do this, even the lightest fiberglass cloth will bunch up and leave awful air voids.
The most difficult glass work is the sail. Lots of gel-coat, and many layers of 4-ounce cloth, cut into small bits so the class could negotiate the tight fillets without bunching.
Once the GRP sail part had cured hard, it was popped out of its tool and the excess GRP that extended past the flange line (obvious on the parts, so no need to mark it while still in the tool) ground off. The flange and cavities of the two tool haves were then waxed up in preparation of the next step.
The GRP sail halves were re-inserted into their tools, and the two indexed tools assembled, putting the edges of the GRP parts up tight against one another and in perfect registration. It was then a simple matter of wetting the seam area from the inside of the part and sticking a strip of glass in there to back up the seam, turning the assembly into a one-piece sail. Pretty slick took design!
The open sail tool with the three securing bolts used to hold the assembled tool halves together as the GRP sail halves are bonded into one unit.
Between laminates of gel-coat, glass cloth and/or mat I sand the surface of the hardened laminate while it's in the tool to knock down bumps and give plenty of tooth for the next layer of resin saturated glass to grab onto. There is no cohesion at work between a cured hard surface bonded with epoxy or polyester resin to the next laminate, so the agent of 'stick' is strictly mechanical and adhesive in nature.
A completed M-1 GRP hull half part next to the tool that gave it form.
Comment