New Design Temporary Female Mold Build Help...

I have been rethinking my design/build process for a small cruising sailing catamaran. I have received a lot of good advice here on boatdesign.net, and because of this I am now moving in a new direction. I am building a one-off composite boat, and I am not going to build a full production mold for the full size hull for many reasons. 1) I am a one man show, and I typically want to do the layup by myself. With that said, there is no way that I can layup the complete hull in one shot. Thus I want to segment the hull into 4 or more reasonable components (segments). 2) I need to have the ability to move the boat components around within my backyard during assembly and having smaller parts would be simple and easy.

The idea is with smaller individual hull components, the female mold would be a considerably smaller footprint, the layup work would be manageable, the handling/moving of the individual components would be smaller and lighter and thus the gantry crane to move the parts around could be smaller, and the ease of burn-out from doing too much of one thing for a long time would also be eliminated (less time spent on one single process at one stretch).

The idea with the smaller individual hull components is also that the design of the boat would be safer/stronger because I would create bulkheads along the connections of each of the individual hull components creating watertight segments that relate to each of the individual components.

The individual hull components would then be attached to each other at the bulkheads just like a nesting dingy design. Therefore, the bulkheads would be double thickness as each hull component will have its own bulkhead and then making the connections at this location would be easy to align and attach each component.

Given this design concept, I am thinking of a footprint about 8'x12' for each hull component, and I think that this would be the largest area that I would want to do composite lay-up in one day. With that said, I want to be able to use the same female mold for multiple parts, effectively making two parts from one mold setup. Building a catamaran, I also want to be able to mirror the female mold for the opposite side of the boat, thus I want the ability to un-assemble the female mold and move the external station frames from front to back to back to front, thus using the same strong-back and the same station locations and by re-arranging the form frames, I will be able to use all the same mold materials and create a new mirrored version of the first component.

Let me know your thoughts on this process and concept. With this now understood what I am trying to achieve, how can I create an easy multi-chine plywood female mold, where the finish is not like a perfect professional gel-coat finish, but more of a basic bones for the DIY one-off composite.

I was thinking of maybe using clay on the interior of the female mold to fillet the corners etc... and then maybe covering the plywood with a like wax paper, or a plastic sheet (heavy duty plastic bag type of material) attaching with a tyvek or packing tape to form the semi-smooth interior form for interior the mold. If I need to wax the tape or the plastic then that may not be so bad.

The concept is to create two or more parts from each mold and then take the mold apart and rebuild it for the next component. So I cannot create many different perfect female molds sitting around when I am done, as this is a one-off design. Using this concept would reduce the cost of the mold construction and reduce the overall footprint size for each part. In fact the concept could allow someone to build a forty foot boat in a typical size garage in smaller chunks and then move the finished parts outside to be installed on the finished boat.

I would use this concept for the hull and the hull interior and then the deck - roof and then the deck - roof interiors. Each individual component would be built on the same strong back / gantry crane area (production area) in the manor in which the lay-up would be assisted by gravity... lay-up will be built from ground up like on the floor up toward the ceiling... allowing easy construction.

So the only problem that I need to solve is how to cover the plywood so that I can spray a layer of gel-coat and do my lay-ups while allowing an easy way to remove the part and quickly get the mold ready for then second or consecutive parts from the same mold, all while having the ability to take the mold apart and rework it for the next different part.

Has anyone done anything like this before?

Any Ideas would be greatly appreciated... I am a year or two away from actual building.

Thanks,

Brian

 

Let me see if I have this right. You're looking to build two boat shaped things in multiple pieces? The first piece will be the mold, faired and smoothed to a fine finish, before you actually make a boat part, right?

Look into some of the "one off" methods for a 'glass build. You don't need to make a mold, though you will need some form of temporary jig, which cheap foam can come to the rescue. For example you can bend and glue cheap foam over a jig, skin it with the appropriate amount amount of fabrics and then pop the part out and move onto the next portion of the build. The moment you try to incorporate molds, stiff and durable enough to be reused, your costs quadruple.

 

Thanks for the input...
But, nope and sorry for the confusion. I want to make a strong back with exterior station frames that will hold plywood or foam that will form the exterior surface or the female mold or "jig" so that I can make two or more of the same parts... without the need to build a perfect faired and smoothed to a fine finish..."production mold", but good enough to get a close enough composite parts out of (that can be faired later) and then use the same "jig" parts to make a second mirrored jig or mold to make additional parts using the same station frames and plywood or foam base. The Frames will be outside of the boat to support the plywood or foam that will shape the outside of the part. Thus I want to build the composite hull like it is being built in a female production mold without the need to make an actual production mold. Using this method will allow me to create two or more identical parts without actually building a production set of molds. The Boat will be a catamaran with symmetrical bi-directional hulls like a Proa.

So yes and no. If i use your non-mold method will the foam be part of the finished hull? I want to build the "jig" or mold that will not be part of the finished boat so that it can be reused and re-use the materials over and over and manipulated into creating a mirrored part by simply moving the station frames in the reverse order on the strong back.

My issue is how to treat the plywood/foam to make a good enough surface that can receive the composite/gel-coat and still be able to remove the part and reuse the jig over and over.

If I have to place a plastic wrap over the jig for each part, that would work for me, I just do not want to have to build the mold over and over for each part.

I hope that this helps you understand want I would like to do. I am sure that someone must have thought of this process before... like I said the finished parts do not have to be perfect mirror finish, but just good enough that fairing the parts would make a usable DIY product but not a million dollar yacht.

Thanks again for the input.
BJD

 

I guess since plywood was mentioned it will be developable surfaces. Is this thing great big or sort of small? Maybe medium sized?

 

Each segment (component) will not be any greater than 8' wide, 12' long and 4' high (the max size of the interior production area)... the boat will be 36' long (3 segments) and 16' to 24' wide.

This project was started in this thread:

New to site, design and looking for perspective!? https://www.boatdesign.net/threads/new-to-site-design-and-looking-for-perspective.57683/page-2#post-823752

My question is how to easily prep the plywood / foam surface for gel-coat and lay-up so that the part can come out of the mold and then the mold be easily reused without needing too much work.

I am thinking of using clay to fair and fillet in the corners using a 2" pvc pipe radius to contour the clay, and then to use spray adhesive over the clay and wood and then fit large commercial wax paper over the mold. Another thought was to use packing tape or Tyvek tape where needed and then waxing that.

The idea is to have a quick method of producing multiple parts from a single setup... someone must have used a quick method of mold making using wood, don't you think? People glass over plywood all of the time, I just want to do the same, but not have the composite stick to the plywood...

Thanks,

BJD

 

Here is an example of the Foam Core female mold application:

Going back to this method... For me this method is too much work... Although this would be the a solution, I would prefer to use a multi-chine plywood hull design and only build the wooden mold once... and then make multiple parts from a single setup leaving the mold in place.

This process is where I received my inspiration, if we can build a female mold in this fashion, why can we not use the same concept to build multiple parts. I am trying to create a down and dirty, quick and easy method for my build. I am not trying to make a masterpiece but a quick cheap build. Go small and be able to go now! I can work with small parts and easy lay-ups, I cannot lay-up a 36 foot long boat all by myself.

Not unlike this method that Jamie used:
Jamie made this boat with a small section of fiberglass mold. Now I think that I can do much better in the fit and finish, but then again I am not building a million dollar yacht.

Again, using this method of a multi-chine plywood mold: how do I fair and treat the surface to prepare for lay-up? Remember Quick and Easy and Cheap.

Thanks,

BJD

 

If I understand you corectly you want some form of constant chamber method adapted to glass construction? Construction Methods - Constant Camber http://smalltridesign.com/Trimaran-Articles/Construction-Methods/Constant-Camber.html
I think it would be possible but the hull must be designed for it.
Another possibility to try is Kelsall's KSS method.
As for quick, easy and cheap that's another story. Mold costs have to be factored in, that's the reality of FG construction. Build S&G ply and you can get away without it (but with other costs).

 

Nope just a multi-chine hull built out of composite... it will have integral ribs and stringers on the interior for stiffing. Just a simple hull that you would build out of plywood, but I am not putting any wood within my boat, thus making it out of composite. And since there are many parts that are identical I want to mass produce them in a mold.

I cannot believe that this concept is so foreign. The question is how to prep the plywood... This is where I need help.

Thanks,

BJD

 

You can make an exterior frame, put in length ways 1x2 stringers every so often (enough to support the liner) and then line it with this stuff. EUCATILE 32 sq. ft. 96 in. x 48 in. Hardboard Thrifty White Tile Board-HDDPTW48 - The Home Depot https://www.homedepot.com/p/EUCATILE-32-sq-ft-96-in-x-48-in-Hardboard-Thrifty-White-Tile-Board-HDDPTW48/205995949 .

Reply #15 describes it a little more... Newbie wohooooo!!!! Need help!!!! 20' Flat bottom River boat https://www.boatdesign.net/threads/newbie-wohooooo-need-help-20-flat-bottom-river-boat.21958/

 

For that you don't need a mold. You can get by with a flat surface with a shiny surface. Lay out the panels on the table gelcoat down, laminate, then stich and glue them togheter like ply. You will only have to fair and paint the corners.

Sam Sam is right. You don't need plywood, you need something flat and shiny. Melaminated surfaces like he linked above, formica, glass, etc. all work.

 

Sorry, I don't get it... I guess that i am just stupid. How do you build a hull on a flat shiny surface or table? Sorry that I bothered everyone... it was just a simple question... how to treat the wood and corners of the mold? I guess that I will just experiment on my own and figure it out myself. I guess that idiots like me should just find somewhere to go.

Thanks,

BJD

 

Thanks for the help... the hardboard is only finished on one side. When I mirror the hull I want to use the same parts but in the mirrored configure. With that said, the back of the boards will be reversed to become the front of the boards for the mirrored mold. I am thinking of using 1/4" luan plywood which is about the same price and they are sanded finish two sides. I like the clay idea, did you have to wax the cay or did you let the clay come off onto the hull where you then simply cleaned it off? It would be an expense to use clay everywhere. I was thinking that drywall mud is cheap. If I placed down packing tape over the corners and then used drywall mud on top of the tape it would be simple to remove once the mold had to be dis-assembled.

I was thinking of using a small finish nail gun to attach the plywood to the station frames and then filling the tiny nail holes with drywall mud. This would allow the plywood to be removed from the stations by simple brute force by pulling the nails through the back of the plywood leaving the nails in the station frames to be removed after the fact.

The idea is not only make multiple parts from one setup, but then reverse the setup and make multiple mirrored parts using the same parts that were used in the first set up.

I like the idea... I think I will try the wax paper idea on a test bed and paint on some gel-coat and apply a few layers of glass to see how this would work on a typical corner joint situation.
I am glad that someone has done something similar. I am interested if you have any pics of the mold work and your setup. Do you think that this was an easy and cheap way to build a mold to get multiple parts?

Let me know what you think and thanks again for your help,

BJD

 

You build the boat like you would do with plywood, only instead of using plywood you laminate your own flat panels from fiberglass and resin on a table. If the panel is not to thick it can be bent to shape. After the hull is formed you can always laminate more on the inside to bring it to the required thickness if necessary. On corners you use fillets and tape just like with plywood. Some hullforms require darts to be cut out in order to be able to take the required form. Then you join and laminate some tape on the inside. It all depends on the design. Use cardboard to make a model and you will see where you can bend and where you must cut and join.

As to your original question the answers are:
If you use gelcoat over waxed plywood the wood grain will show on the gelcoat. In order to have a good surface you need something flat and shiny like glass or melamine (Formica).
For fillets, roundings, and other details everybody uses bondo. Lay it on, sand it to shape and mirror finish then wax and spray mold release.

Here is a video explaining the building of hulls from flat fiberglassed panels. These are infused and partially cored, but you can handlaminate them.

 

Yes, thanks... I have seen this process as well... the real way to make accurate parts (in my mind) is with the infusion foam being cut to the exact size that you need and then infusing them. I would assume that if the hull was comparable to a stitch and glue type of hull then you could only attach two panels at one point of contact and then bend the panels into the jig and attach the remaining panel length or locations with the tape and epoxy method while clamping the panels together somehow while the resin sets up. I cannot see me just blindly creating fiberglass sheets into anything that would resemble the parts that I need unless I fully let them cure and then cut them out with a pattern before setting them in the jig. This would be wastage for the glass/resin and I would have to do this same thing for each part that I create.

As to the waxed plywood, I would not go that route. I don't really want to wax (not crazy enough to apply 10 coats), thus the idea of using wax paper. An option would be to use drywall mud and lightly cover the grain of the wood and lightly sand the plywood finish, but then I would want to spray the plywood with a clay or something that would act as an easy release agent. I don't really need a perfect mirror like finish... this is not that kind of boat. I am going to epoxy and bolt the hull segments together along the bulkheads and then epoxy and tape and glass the interiors and exteriors seams of these connections and then I plan on covering the seam patchwork with flowcoat. I only really want the gel-coat for UV protection, as I am not looking for a perfect 10 out of 10 project. I care more about strength and comfort than appearance, and I don't care about resale... This is a once and done project... I just want to get splashed, live aboard and travel. Once I get too old to care for the boat, or if the boat does not care for me, than it can be donated to someone who wants to take it over. I have only a small amount of usable years left, I refuse to spend my time "wax on wax off" and sanding and faring till my nose holes are clogged.

My goal here is not to make a masterpiece but turn the composite portion of the project around as fast and as cheap as I can while making the structure ultra-strong, safe and insulated and most importantly into the configuration that I desire. I had a family friend who built a "40 foot spray schooner" mahogany strip plank hull, but he never finished the project. What work he did do though was expertly crafted and so very beautiful. His father was a shipwright and he and his father build many smaller boats during his life. For this one he steamed bent each 2" x 2" mahogany plank and used wooden dowels and epoxy to attache the planks to each other, but he never got to set it in the water... But he made all of the rigging and most of the internal and exterior parts to complete the boat (in his basement during the winters), he just made it to the sheer-line with the hull... and then the city made him remove the boat from his yard after 30 plus years of building his masterpiece. He had to give away everything that he built, or take a chainsaw to it and haul it off to the dump. He gave me a small block (pulley) that he made from scratch which took him about 20 hours of work and $150 of brass and oak... It would be piece of fine furniture if were only bigger... I am not that guy.

So if there is a cheap magic spray that will give me a good release on the mold than I am there... I don't want to use bondo filler as this is too permanent and I want to be able to dis-assemble the mold and reverse the existing all ready made parts to make the mirrored mold and mirrored parts, so the compound in the corners and along the seams needs to be easy removable.

I know I sound like an idiot... I can hear myself... so I will just try things out and experiment on a small scale and see what happens...

Thanks,

BJD

 

I am building a developable panel boat.

Just the epoxy area alone is a table 8’ long 2’ wide and 2’ of clearance to meter into buckets.

The boat is 32’ long. However, there are no discontinuous joins on the 32’ 6” panels, so the vac table is 400” long.

I am sure you could build a boat with less space, but the smaller the workspace; the longer it will take.

I think you ought to revise some expectations about workspace.