Is this a novel way to buid a boat?

I am planning to build a sail boat of my own design (38 ft LOA) with help
from a friend.
Although we built several small items such as rudders, neither of us tackled a full size boat before.
In the process of discussing several different methods of construction and considering their plusses and minuses, we came upon this idea.
Imagine we have access to rent a five axis CNC modeling machine from a friend capable of producing a solid foam (polyurathane) model of the entire boat, or in 4-5
more manageable sections which can be transported and joined together.
Now in your workshop there is your boat before your eyes made up of foam.
From there we guess we can go to cold molding, laminating several layers of mahogany sheeting with epoxy, or first isolating the foam and go conventional fiber glassing.
This applies to both deck,superstructure and the hull.
By doing this, we think we skip the major task of producing a mould, lining it up correctly and making sure all lines are fair. Which is difficult for a first timer.
What do you think?
Provided that we can produce the foam model at a reasonable expense, we think it is worth the effort. And if we decide to build another, the foam moulds can be re used.
What would be the pitfalls? Would a solid foam model of this proportion would be strong and stable enough to build a hull around it?
What foam would be best for such an application?
Can/How the foam model be properly isolated from epoxy based materials?
Has this method ever been applied to boat building?
Any wievs on this is gratly appreciated.

 

If surfboards are considered boats. yes.
If you are trying to get high accuracy, remember that foam of that scale isn't cheap. One software error and you gain nothing (but your foam is useless now except as scrap).
Then, in order to release the foam from the hull, it has to be slippery---- presumedly painted with something like epoxy and then waxed.
Your hull would be glassable, but strip-planking or cold-molding are out. they would both require temporary fastenings. You are then left with glass as an option, but all glass hulls are thicker in some places and thinner in others, meaning the shape you so carefully programmed into the foam isn't the same shape you are getting. You could, of course, go with the same glassing schedule throughout and later build up the inside, but in between, you'd need a new female form to support the floppy boat, one probably made from wood.
The outside surface won't have gelcoat sprayed into it as is usually done. Instead, it must be carefully filled, faired, and prepped for gelcoat to be applied carefully enough to avoid having to do much touch-up afterwards.
All in all, for the reasons above and others too numerous to mention, I'd say the method would be far too time-consuming and material-intensive to be practical.

Alan

 

No matter how you do it a 38' boat will be very expensive ($100,000+?) to build. It's quite an expensive risk to use an unproven design.

 

Omeron, SamSam is right, there is no cheap way to do it, they all cost money. I believe that strip planking for the home builder will produce the simpliest and fairest hull form, glass it or do what you like, but the construction is relatively easy to do, errors are immediately visable, and correctable without much cost at all, and the finished product is (assuming all other things being equal) a saleable item at profit.
Playing around with dimensional routers is still for the big boys I am afraid. The place where I work in China hads just had a mould made on router, it is far from cheap, but it is quick and accurate, well as accurate as the program is anyhow. As Alan basically said above, mistakes are very costly, and as a one off boat, I will put money on the table now that it cannot be done without a mistake being made. Many boats are built with mock ups of the layouts, these cost a lot to do, but generally they save more than they cost. To invest in a one shot go would be to err.

 

Thank you gentlemen.
Your points are well taken.
When i mean by designing my own boat, i mean the conceptual drawings and dimensions. Surely a professional will do the actual and final plans.
The idea seemed interesting, as there is a possibility of two or more boats being built.
I agree that machining such a big item is risky. But perhaps it can be divided into one meter thick sections and each piece checked before the process continues.
I do not know how expensive the foams are. But i guess each section can have a box frame inserted into it in a way where no machining will be done, thereby reducing the amount of foam required. This may also be more sturdy than just solid foam.
Also, if these sections are made smaller than the actual hull dimensions by an amount, equal to hull thickness and foam lining, than the finished hull would conform to the final dimensions.
If we fiberglass each foam section permanently,and as part of the mold,and insert plugs, than we can perhaps have permanent anchoring points for cold molding,strip planking.
It is appealing to have your boat molds stored as layers of flat packs in a corner of your storage facility,sent to anywhere in the world in a container, and literally deployed in a matter of hours to begin making another boat.
And it can be used many many times, as there is no danger of surface detoriation as it would be in a female mold.
Can anybody give an idea of where and how the foam can be obtained,and a rough idea of what the cost would be?
Many thanks.

 

It's plain to me that you are talking about a semi-production method because what you are describing is orders of magnitude more labor intensive and material intensive than molds and ribbands would be.
I can almost envision it---- the boat's built upside down, and the foam parts (fat interlocking rib-shaped blocks) need only follow a curving line on a flat floor. They could bolt together on the inside.
Unlike a production-built boat, this method is for the tiny segment of the boating population who build rather than buy their boats. Not many will ever be produced. Only heavy web advertising will get interest, and the design must be by a known architect if anyone's to have confidence in it.
While the idea has some appeal, the size of boat you are talking about may not be the best use of the method. A 16 ft foam open boat mold could be built in one piece and easily shipped. This would be for strip or cold-molding, of course, since you can also ship a small boat mold made of fiberglass.
While the smaller boat mold would find many more potential customers, your mold must be more cost effective than a home-built mold/ribband or simple station frame or bulkhead built mold.
When taken to this scale, you can see the comparison more readily. It is not that much work to set up for stripping or cold-molding a small boat---- the question is if the average home builder would pay to have shipped (two ways) a thing that big. Or if in pieces, to ship and then also have to assemble.
It seems the whole enterprise would turn you into a marketing business more than anything else, which is fine, but it's a lot of work and it isn't about boats. It doesn't need to be more efficient and cost-effective anyway, just systemized to the point where the home-building neophyte customer sees it to be fool-proof (color-by-number is tedious, but fool-proof too).
It's a question of what you want to do for a living, and whether the risks are worth the potential gains.

Alan

 

There is a boatbuilding method using bead and cove foam planks on a rather conventional mold setup.
Another method that has been used quite a bit is to lay up fiberglass panels on a large flat (or slightly curved) table and then splice them together on a jig for the hull or superstructure.
I would think you should investigate these methods before you decide to go ahead with the CNC male mold you are thinking of. The last price I heard for a CNC foam mold was $!00 dollars per square foot. Companies are willing to pay that if they have a paying customer who wants his boat as soon as possible. But not many are made on speculation. That price was from several years ago also. It may be higher now.