Fast, cheap, reusable male molds?

I had this idea and posted it in another thread in which I was looking for boat guidance. Since the idea is buried a few posts down, I decided to give it its own thread because, the more I think about it, the more I want all of your opinions on the idea. This would be for a small ship built in a garage for a minimal cost. Undoubtedly, there are far superior methods for mass production and it would probably not be appropriate for large hulls.

Basically, my idea is for a Reusable and Collapsible Form. It would allow homebuilders to manufacturer a one-off boat with accurate dimensions without having to do a lot of frame building or lofting. Someone could set up their entire plug in an hour or two and permit them to make the entire shell of their boat- all 4 sides- at once. It would work such that multiple people could make one-off foam-cored boats with the same mold that can then be broken down into small pieces and shipped to other builders at a reasonable cost to help amortize the cost of the mold. My idea was actually intended for aircraft construction, but I thought it could work equally well (or poorly) for boats. Here's how it would work:

Imagine I'm building an 8 foot boat. It's going to be built in one piece.

You would have, say, 20 metal(?) U channels, ~ 3/4" in all dimensions with the open side facing outward aligned radially. Into the channel you would screw in (or otherwise secure) a piece of wood which would serve as the stringer. This wood would be shaped to give the appropriate dimensions. Attached to the base of the U-channels would be a threaded rod and butterfly hinges. When collaped, it would be 8 feet long with perhaps 24 inches in diameter.

Now, you want to get those stringers out farther than 24 inches because the boat is going to be wider than that... so you start turning the threaded rod and this pushes the stringers outward. Then you turn another threaded rod... and another... with each threaded rod pushing different stringers out to varying degrees. I would provide a measurement describing how many inches each rod is to be extended.

When all the rods are extended, you now have the shape of the boat, as provided by the wooden stringers. You lay the foam on the stringers, fasten it by, say, wrapping roving around the foam pieces and epoxying it into place. Then coat it in a slurry. Then you lay up the layers of fiberglass all around the boat (obviously, this would have to be done in multiple steps as it would be impossible to glass a structure upside down).

Finally, once the outer shell is complete, you reach in from the passenger compartment or other provided access areas (which had no foam covering), and collapse the entire supporting structure by turning the threaded rods and pull it out the entire assembly through the transom area.

You now have a complete 4-sided one-piece structure. The form can now be shipped to someone else- in its collapsed condition to save shipping costs- to build their boat. You then proceed to glass the interior of your structure.

Of course, you would probably also want to slide in premade bulkheads and bolt them to the frame in order to stiffen up the structure a bit more before building your hull. The point is that, instead of using glue and nails and whatnot to create the male part of the mold, you are simply using threaded rods to provide tensile strength and the bulkheads for compressive strength and the "mold" is collapsible and reusable and allows you to build all four sides at once.





Here's the same idea, with a different approach-

Make the frame into 5 pieces, each running the length of the ship: A right side, a left side, a top, a bottom, and a middle.

Once the foam is secured and the exterior is glassed up, unbolt the middle section and pull it out through the transom. This will cause the top piece to fall down and you can then pull it out as well. Next pull out the two sides, followed by the bottom.

Voila! a 3-dimensional plug that can be removed through an opening which is smaller than the plug itself.




What do you think?

 

Sounds great but all boat builders however big and small are constantly searching for the ultimately plug. Stability of a plug is vital for a good fair surface.

Grp, foam on wood framing, foam of steel framing, 100% wooden plugs have all been tried. At the end of the day, the more stable the plug, the better. Each have there own pros and cons. The idea is great but unfortunately not practical.