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Choices & Decisions

I do, however; think that a good hull design using foam strips, Corecell or Airex, for a foam/fiberglass/epoxy composite would produce a very light, strong and totally rot resistant hull. This style of construction has it's concerns and limitations, everything decision on a boat is a compromise after all, but if Wharram's were designed for that style of construction I certainly would have been willing to build it.

    So I've decided to build it in plywood, so it's time to order the wood right? Wrong! Try doing a Google search for marine plywood.  Almost 2 million results from that search. This is where the various message forums on the internet come in so handy. If you spend the time and effort to crawl through the archives of the WoodenBoat, Multihull,  and various Woodworker forums you can begin to educate yourself on the pros and cons of the different type of marine plywood but I'll sum up what I learned here.

    "Marine plywood" as a phrase describes the specifications of the construction of the plywood. It has very little to do with the wood species themselves. There are standards for marine plywood construction, British Standards (BS) 1088 and 1056. These standards were set to control how untreated tropical hardwood veneers were made into plywood. While they are British Standards, the finished product does not have to be British made, actually the standard was associated with Lloyds of London as it set standards of construction for all types of materials based on what it would, or would not, insure. While there are no longer "British Standard" inspectors checking plywood construction, manufacturers are building and marking their product as conforming the BS standards. So while the standard is not monitored by any regulating body if you buy materials from a reputable dealer you have some level of comfort that the product meets those standards. However, that in and of itself is no guarantee the plywood meets the standards as some boat builders have discovered. A prudent course of action is to buy from a reputable dealer and to test the plywood before you use it. If after that you still have problems, the reputation of the dealer will determine if they will back their product.

    What are the standards?

    BS1088 - is defined by the following 4 basic requirements

1. Same species of wood throughout.
2. WBP Phenolic or Advanced melamine resin glue line
3. No core gaps, some small pinhole gaps are accepted
4. Whole piece face and back, no spliced faces, allowed Grade is normally an A/B

   BS 6566 - is defined by the following 4 basic requirements

1. Wood can be mixed in species, normally the core will be different from the face.
2. WBP Phenolic or Type 1 Ext Melamine glue permitted.
3. Some allowance of core gaps permitted, recommend filling any exposed edges before further encapsulation etc.
4. Faces can be made up of one or more pieces, spliced together. Grade of face is normally B/C

    The vast majority of marine plywood in the world is made from the Okoumé (Acuomea Kleinea) tree which is harvested in the African state of Gabon in the tropical forests of the Congo Basin. This wood is also often referred to (correctly or not) as Gabon, Gaboon, Okume, Ocume, Ocoume, etc. and the plywood core as well as the skins are made of the same wood. Virtually all Okoume plywood is manufactured outside of the US and Canada so it is a good bet that the plywood will likely come from some factory in greater Asia, Israel, France or Greece.

Another less common variety of marine plywood is Meranti. It is made from many subspecies of the 'Shorea' tree species which also happens to be the source of wood for the common Lauan (luan) plywood. Both Lauan and Meranti plywood are also referred to interchangeably as Philippine Mahogany and the wood is harvested in Indonesia and the South Pacific rim forests.
Now, there is also White Lauan made from Shorea almon, Red Lauan made from Shorea negrosensis which happens to be the Red Meranti. Other Meranti plywood is made from Shorea curtisii, S. hypochra, S. leprosula, S. multiflora, S. platiclados, S. pauciflora to name a few. Marine plywood is also made from Fir, Ash, African Mahogany (Sapele),  Honduras Mahogany and/or combinations of Okoume core with other wood skins. Clear as mud ?

What was available in my area came down to four basic choices: Sapele, Okoume', Meranti and Fir. There are several manufacturers and prices vary widely. Here is a comparison of these four choices looking at a 4X8 sheet of 1/2 material for weight, durability and price:

    Weight is an issue for cruising catamarans. Lighter, stronger hulls translates to faster boats. All good catamarans will be constructed of some form of cored hulls, either wood to composite materials, because a solid fiberglass laminate would be extremely heavy in order to get the hull stiffness required. This isn't a problem for a displacement boat but it is a death sentence for a catamaran.  So the lighter the plywood panel is the better. Every pound of weight put into the boat during it's construction stays in the boat. One must be careful not to overbuild and thus impact performance. Based on that criteria the Okoume' seems to be the best choice however it is much less resistant to rot compared to the other wood species. While that should not be a problem for a panel that is encapsulated in epoxy, the real world has concrete seawall, coral heads and other boats that all threaten to breach the epoxy barrier when, not if, you have accidental contact. Another consideration is the renewability of the tropical woods. None of us what to encourage the wanton destruction of rain forests for unchecked consumption of resources.

    Fir on the other hand is a known renewable resource with excellent rot resistance, fairly light weight and is usually the least expensive of the panels. The one big downside of Fir is that the plywood panels will check, cracks in the face veneers, unless they are sealed with epoxy and fiberglass. Even then Fir tends to telegraph grain patterns through the fiberglass. It will be much harder to achieve and maintain a high quality finish on boats made of Fir. If you are willing to put in a bit more time to work with fairing the Fir and accept a workboat finish, i.e. a rougher, simpler finish, then Fir is an excellent choice.

Meranti is a good compromise between the Fir and the Okoume' with a nicer finishing surface and fairly light weight and the Sapele is a beautiful wood to work with especially if you plan on a bright finish.

I spent a great deal of time thinking through these choices and a few others that are available, MDO, pre-made Composite Panels, SuperPly, etc. and what I decided on was to use BS 1088 materials for the hulls with Meranti for the keel and lower hulls, Okoume' for the topsides and Corecell foam composite for the decks and pod. This put the heaviest and most durable materials below the waterline and progressively lighter materials higher up. The decks will be foam/fiberglass composite to prevent any chance of rot in the decks.

The next big choice... Epoxy. Up to this point all I had used was West brand epoxy because that was what I was introduced to when I first started using epoxy. Never one to just go with the flow I started researching epoxies. I went to the websites for the big three: West, System 3 and MAS.  I also researched other epoxy  sites included Raka, Progressive Epoxy Polymers and Industrial Formulators. Each of these sites are loaded with information and the time you spend researching epoxy is a good investment that will pay off  dividends when it comes to using the product that you choose. Since I was already familiar with West epoxy, I ordered samples of System 3, Progressive Epoxy and MAS and played with them... bonding some sample panels and making practice fillets. In my experience, all of these epoxies are very similar with only minor variations so a lot of it comes down to individual comfort using a product, price and customer support. One issue to consider is what the mix ratios are. Resin to hardener ratios vary between 5:1 all the way down to 1:1. The chance of error in mixing ratios is greatest when you have a high ratio.  Regardless of what the mix ratio is of the epoxy you are using you always want to be very careful when measuring your epoxy components.  Most vendors offer calibrated pump sets that will dispense the components in the correct volumes. These pumps are great but if you are using a lot of epoxy more than likely you will find that the pumps are too slow for larger batches. As an alternative to the pumps you can measure by weight or by volume and mix larger amounts faster. You don't want to try to mix too much at once though, the greater volumes with speed up the chemical reaction and you can easily lose a large batch of epoxy because it "kicked" to fast. The plans come with Wharram's recommendation for West System epoxy and granted, the Gougeon Brothers have contributed an amazing amount of research and information to the world of boat building but that aside, I find West to be harder to work with, the high mix ratios are harder to work with and carry a higher chance of error, West blushes easily which means more work for me and the amines seem to be more caustic. It is also more expensive... a lot more!

I ended up choosing MAS epoxy. In the course of my research I spent quite a bit of time on the phone with JB Currell, CEO and co-founder of MAS epoxies. He was very interested in my project and was quite complimentary of James Wharram designs. For me he was the perfect salesman, he answered my questions, offered some opinions and then left it up to me, with no pushy sales tactics at all, just another guy that loves boats and believes in his products. In the end I will end up spending a little more money as MAS wasn't the least expensive epoxy but the quality of the support that I have gotten from JB and everyone at MAS has clearly shown me that I made the right decision.

    A key selling point was that the MAS epoxy with the slow hardener is a non-blushing epoxy. No amine blush means less work and less exposure to the agents that cause most of the contact dermatitis, or "epoxy allergies," that cause some builders to suffer. Beside they used MAS on Ocean Planet, Bruce Schwab's Open 50 racer so I am in good company!

    Another decision that I really don't have a good answer for is how much of a "business" to make this venture. Do you incorporate as a boatbuilding company? What are the tax considerations? What about port hazard or builders insurance? What I have done is open commercial accounts with Noah's Marine, Port Supply and Fawcett. There are lots of suppliers out there that you can use so call the ones that you are familiar with and talk to them. They all have slightly different requirements regarding order volumes and discounts but you can negotiate everything. The mindset that you need to have is that you are going to spend a LOT of money so they need to earn your business. If you want contacts for any of the suppliers that I use please drop me an email and I'll be glad to help out. You should also talk to your accountant or tax attorney about the advantages/disadvantages of setting up a corporation for the boat building. This will vary from state to state but don't over look the potential tax benefits of creating a business.

    The last big decision at this point in the project came to dimensional lumber, softwoods and hardwoods. The building plans comes with a detailed materials list that includes dimensioned lumber.  Each item is presented in it's finished dimensions and total linear feet. For my use this list had to be converted to board feet and I calculated it in rough cut sizes, i.e. 4/4, 6/4 and 8/4. Some builders have been able to obtain lumber that was already cut to finished size at no extra cost but I wasn't lucky enough to find a resource that offered that service. I did find a great source for lumber nearby, Walls Lumber in Mayodan, N.C. Steve Wall has an incredible lumber company and he stocks almost everything that you could want in lumber, plywood, molding or woodworking machinery. Steve is into building guitars and stocks lots of exotic woods and veneers for instrument building. I went up and toured his facility one weekend looking at the inventory of lumber that was appropriate for my uses and ended up choosing to use Southern Yellow Pine (SYP) for my boat. Steve agreed to support the project by keeping a running list of my purchases and back crediting previous purchases based on the total lumber purchased. So while I paid more initially I will get credit for the overall purchased amount as I go along. The first purchase was for 900 board feet in 6/4 (six quarter) and 8/4.

So now I had my materials planned, ordered and starting to arrive. I started shopping around for a few more woodworking tools that I was going to need, a jointer and a surface planner. I had ordered a 14" Grizzly Bandsaw early in the planning stage and ended up choosing a Jet jointer and a DeWalt planner.  Once I had these were in place and tuned up I started milling the SYP for the stringers, keel flange, bulkhead guides, and support legs for the bulkheads. This process started with surface planning to thickness, jointing once edge flat and square to the face and then ripping to size on the tablesaw. In order to create the stringers I needed to scarf the ends to make up sections long enough for the hulls. Most scarf joints are around 8:1, meaning that for a 1 inch thick board you measure back 8 inches from the edge and plan that angle to the edge on both boards and then glue them together. This joint makes an incredibly strong joint due to the large gluing area and one that will bend as if there isn't a joint there at all. There are several different scarf joints that you can cut, either by hand or with machines: Stepped Scarfs, Finger Joint Scarfs, and just a regular Scarf Joint. For my application I elected to go with a regular scarf joint with a 1:10 ratio. The first few I cut by hand with a VERY  sharp jack plane. It worked but I wasn't especially fast. Considering the number of scarf joints I need to make I decided to move up to a machine powered solution . So I made a jig to hold the boards and used a router with a straight bit to cut the scarf. That was quite a bit faster but Holy Cow did it ever make lots of shavings and dust. Not totally satisfied with the results I made a sled for the table saw. This one works like a champ. The only tricky part is that in order to cut both ends of the milled scarfs I had to feed one side of the stringer in backwards. A sharp thin kerf blade and VERY careful progress allows me to keep my fingers attached to my hand when I do this. Every once in a while I end up with a rough spot that needs dressing with a block plane but over all I am very happy with this method of cutting the scarfs for the stringers.

 So let's build a boat. . .