Origami Hull

The Origami hull is a hull formed by folding steel into the shape of a hull. The hull plates are first butt welded to form a two large flat plates. Each of the two larger plates will be formed into one half of the hull from bow to stern. To form each side, darts cut into the plate and then is bent so the edges of the darts close together where they are welded. With both sides of the hull completed the side are brought together and welded down the keel.

Test pattern for a single chine origami hull.

Here is an example of an Origami Boat pattern for a single chine hull. You can download and print the large image of the pattern, then cut out the pieces and tape it together to see how the process works.

See "Paul's 65ft Origami" for an example of how a large origami hull is built.

Want To Lean More about Origami Boat Building?

On Alex Christie's web site, Origamiboats: The Art of Frameless Steel Boatbuilding, you can find more information and purchase a video and book that covers the origami building process in more detail. You can also join the Yahoo group; Origamiboats as well as a FaceBook group Origamiboats -- Frameless Steel Yachts. You can also download a self extracting (zip) compressed file of all of the messages on the Yahoo group between it's creation and Jan of 2010: Yahoo_Origamboat_Archive_Feb2000-Jan2010.exe. Thanks to Ben Okopnik for putting that together. And Ben keeps an updated, online searchable archive is here: http://okopnik.com/origami.

Steel vs. Aluminum

Originally we had planed on building in Aluminum but the price of aluminum would have required waiting another year for us to have enough cash. So the cost was the most important factor to us because the other differences in the end were a washout.

Comparison	Mild Steel	Aluminum
Material	Hot Rolled 1/4" in 6 x 45ft plates	3/8" 5086 H116 8ft x 20ft
Hull plate cost, July 2008	$36,456	$76,800
Weight	10.2 lbs. per sq. ft. of 1/4 inch. Steel is heavy. The only good thing about that is a heavy boat tends to roll less, but you can always add more ballast to an aluminum boat and that wait will be lower and do the same job better.	5.19 lbs. per sq. ft. of 3/8 inch. Hands down, aluminum boats are going to save weight, which translates to more cargo, less fuel, and more speed. Some of this weight savings will need to be used to reinforce around welds and in areas of vibration.
Endurance	Yield Strength: 36,000 psi Ultimate strength: 60,000 psi The difference between the yield and ultimate strength represents the "plastic range". Steel is stronger that aluminum by volume, but when you make the aluminum 50% thicker it is stronger than than the steel. Steel has superior abrasion resistance. Drop a sharp object on steel and you will just get a scratch in the paint. Steel is much less susceptible to fatigue due to vibration.	Yield Strength: 30,000 psi Ultimate strength: 45,000 psi. To compensate for it's lesser "plastic range", aluminum hulls are made150% thicker than steel. The thicker plate provides additional stiffness and a hull that is about 30% less likely to dent and about 12% stronger before it fails. It is easier to mare the surface of aluminum with a pointed object, like the end of a pipe. Additional reinforcement is required around engine beds and chain plates to reduce fatigue from vibration.
Cutting	Quick and easy provided you have a plasma cutter. Slow and messy if you have to use a torch.	Cuts perfectly clean with normal carbide bit blades in any wood working tool.
Welding	Stick weld to pull the hull together and then finish it with either stick or wire welding. A stick welder power source, a long welding lead, and a suite case for wire welding with shielded wire will set you back about $4000. You will still need a spool gun for welding aluminum that will be used on the pilot house and hatches.	MIG wire weld is easy even for the novice provided you spend about $6000 for a welder like the Miller 350P with a 30ft push-pull wire gun. You will have to work in doors or wait for the right weather. It needs to be 90 degrees so that thermal expansion is not a problem, and you have to be protected from wind and rain. Welds on Aluminum are weaker than steel but backing bars can more than compensate for the loss of strength in critical areas.
Corrosion	One word: Rust. You will need find, prep and paint chips and scratches soon after they occur. Both steel and aluminum boats need to be protected by zinc anodes. But steel is much less susceptible to galvanic corrosion.	Corrosion can be a serious problem if you plan to say in marinas where stray electrical currents are often a problem, as well is the presence of steel or iron in close proximity. Organic growth will hasten corrosion and bottom paint must be designed for aluminum. Aluminum is very susceptible to corrosion from copper. A penny or piece of wire laying in a bilge and eat through a hull in days. Any non aluminum metal laying against the hull will be a problem. Fasteners must be plastic or stainless steel. For this reason bilges are often painted to help insulate them. This is a big drawback for us, because our boat will have shop in the cargo hold for metal working, a welder and a plasma cutter. The spray from a plasma torch will immediately burn into the surface of aluminum impregnating it with steel which immediately starts to corrode.
Paint	Two coats of epoxy paint are required for both inside and outside after you have sandblasted the metal. Sandblasting a 70 foot steel boat will be around $6,000 which is a sizable chunk of the original savings on the material.	No need to paint the inside of the hull. Painting the outside is strictly for controlling the heat. No will stick really well to aluminum so plan on repainting every few years. No paint is an option but it will be hotter in the tropics. Only routine coats of bottom paint is required, but that is needed for steel too.

Metal Estimate

Originally thinking in Aluminum it is ideal to get the plates wide enough to avoid as much welding as possible. In aluminum everything would be 3/8 inch except the pilot house which would be 1/4 inch.

Hull: 15 wide x 75 long x 2 sides; 16 plates - 8 x 20ft
Deck 16 x 70; 8 plates - 8 x 20ft
Bulkheads 8'x 16' x 5; 5 plates - 8 x 20ft
Keels 20' long x 2 deep x 2 sides x 2 keels; 2 plates - 4 x 20ft
Skeg & Rudder 15 long x 8 deep x 2 sides; 4 plates 4 x 20ft
Pilot House: 15 x 16 roof + 4 x 62' perimeter; 2 - 8 x 20 and 4 - 4 x 20

When converting to steel the wide plates are no longer important but steel comes off a roll so lengths up to 65 feet are available if you don't mind paying extra for the oversize truck to deliver them. If I could get 75 foot long sheets, it might be worth considering, but I choose 45 ft sheets because they fit on a standard truck and will allow the butt joints in the hull to be staggered.

The pilot house will still be aluminum on a steel boat; so to convert the aluminum sizes to steel I just took the square footage for all of the 3/8 inch plate which came to 5,120 and divided that by 6 ft, which is currently the widest steel plate available without having to pay extra and that comes to 854 feet. Divide that by 45 ft plates and it comes to 18.9, but 20 is a nice round number. In July of 2008 the price is 61 cents a pound delivered, plus tax. It would have been half that cost if we had purchased in January, but that is spilled milk.

In addition to plate we also need 1000 feet of 2 1/2" to 3" Sch40 for the bulwark and for rounding the corners. We chose to go with 3 inch. It's considerably more but I have bent 2 1/2" pipe and never bent a 3 inch pipe yet. Also 800 ft of 1/4 inch, 2 x 2 inch angle that will be used for ribs and stiffening the deck. We could go with 1/4 thick, 3 inch flat bar too, but I banging your head against the flat of an angle is much nicer that the edge of a flat bar.

Metal Purchases

CWT = 100 pounds
CFT = Foot

Date	Qty	Description	Size	Weight	Weight Each	Price	Price
July 2008	25	Steel - 3" Sch 40 Pipe	42 ft	7,959 lbs	318 lbs	$6.25/CFT	$6,562.50
July 2008	30	Steel - 2 x 2 x 1/4 Angle	20 ft	1,914 lbs	64 lbs	$58.5/CWT	$1,119.69

Metal Arrives

Movie - Unloading plates

20 - 6 x 45 ft plates.

Freshly rolled off a coil it looks
really clean.

Moving Big Plates of Steel

We decided it was time to move the steel inside the fence on up on cribbing where it will be easy to access from the building pad. We learned some lessons about moving big plates of steel along the way.

Pilot House

The pilot house is about 16 ft wide and 20 ft fore to aft and will be constructed from 1/4" 5000 series aluminum in order to keep the weight down. The only trick is connecting the aluminum to the steel so that the aluminum does not corrode away. There are two basic approaches. The most popular is to completely isolate the aluminum form the steel with a water tight gasket and bolts that are insulated by nylon washers and sleeves where they pass through the holes.

The second approach it to bond the aluminum to the steel so that the electrons can flow across the joint easily. When there is no air or water gap between the two metals then the aluminum will not corrode. You can not weld aluminum to steel in the conventional manner but they can be explosion welded together in sheets. You then buy a bar cut from the sheet and weld the aluminum side to the pilot house and the steel side to the deck. The only real problem is that explosive welding is not something you can do at home and a 2 inch wide aluminum to steel bar will cost you $62 a foot (Jan 2009).
Video on Explosion Welding: http://crazymotion.net/explosion-welding/wldl6fIDGQ5EjAy.html

There is a chemical approach for bonding the aluminum to steel. Ultra Safety Systems makes a product called TefGel; www.tefgel.com. To use TefGel, you would dry fit the pilot house with a gasket made from butyl rubber or strips of fiberglass board. Then paint the steel, put the gasket and pilot house back in place and coat the inside of the hole, the bolt and nut threads as well as the washers with TefGel and tork it down. A fiberglass gasket will add a little more stiffness to the structure that rubber but they did not recommend any other sealer in the joint although it would not do any harm and would work to hold the gasket in place as stop leaks between the joints in the gasket. They recommended G-10 or FR4 epoxy fiberglass. A 1/16" thick, 12 x 48 inch sheet is under $30. TefGel is $22 for 2 ounces. And like the explosive welded interface you will also get a pilot house that will conduct a lighting strike on into the hull. I can see where it would be useful for all the other stuff that gets bolted on as well.

Getting to the Water

There is a highway bridge just blocks from the house that is 15 ft 8 inches. After that it's just utility lines. The pilot house as well as the forward and aft bulwarks will have to be attached after we are on the other side of that bridge. The mast will have to wait until we are at the Port of Catoosa; www.tulsaport.com. Then it's just 440 miles and 420 feet in elevation through 18 locks to the Mississippi and then another 600 miles to New Orleans and open water. The closest call we will have is the I-430 bridge in Arkansas which has it's clearance listed at 53 ft when the water is at it minimal level. Luck for us, the top of our mast is 52 1/2 ft from the water.

Links

www.moonflowerofmoab.com -- A completed project with lots of photos and documentation.
www.harderwoods.com/pipedocs.html Online Pipe Fitting Templates