The New Boat
26-Feb-02
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Why a new boat ? Why build one ? The design process. Making a model.
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The model
The real thing
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After building and sailing Amakhaya for 30 years and sailing it around the world you might think the bug had finally been exterminated. But it hasn’t. It is still alive and well. The pull of the remote bays and scenery and smells of far off places, the freedom to go where you want to and not where the roads and signposts let you, and the challenge of being self-sufficient have become overwhelming. So I have no choice, I have to have an ocean going vehicle.
Marit and I looked at buying one of those fancy fibreglass sailboats which you can basically buy and drive away, but we rapidly realized this was not what is was about. There were two strong reasons for this. First, most of the standard boats in our price range were not the sort of boat we wanted. Nice as they are they are not really good for cruising. You cant see the outside from inside, the machinery is all tucked into inaccesible corners, hard to get at when your skeleton is getting more and more rigid. Second, if one bought a new boat, what was left to do except polish it and sail it around. What is going to occupy those other 6 months when it was not being sailed?
It was clear we needed a challenging project that would allow us to vent our construction urges and end up with a product that could take us anywhere. So it was decided to build a boat that was laid out the way we wanted it and not the way the commercial boating industry dictated.
So the new boat would have to have;
- A good size engine room to house a generous main engine, a generator set, a water maker, big batteries, auto pilot and sufficient fuel capacity to stay away from docks for long periods.
- A good size main cabin and galley from which you could watch the world go buy and in which 4 or so people could comfortably carry on daily living.
- A simple to handle sail rig that would also enable the boat to move respectably under sail, both downwind and upwind.
- A strong hull and rigging that could take the pounding that sailing into a sea will give.
- A handling capability that gives manouverability under power.
All these factors lead towards a motor sailer type sailboat. In addition it must be reasonably easy to build.
Given what we want from the boat the first step in the design process was to make some sketches to see how these requirements would constrain the layout of a boat. A generous and accessible engine room together with a generous and usable main cabin with an outside view immediately demands that the engine room be under the main cabin and sets the heights of the deck level and cabin top.
The manouverability requirement indicates a fin keel and skeg rudder. A long straight keel as on the Amakhaya is definitely not to be repeated.
Sketches soon showed what rough shape and dimensions the boat would have to have to look reasonable and to achieve the desired results.
The next step was to implemement a detailed design on a computer using auotocad. I had decided steel was the best medium for what I wanted and by using computer controlled cutting of the steel parts I could greatly simplify the building. This meant making a 3D model of the boat and then projecting the components onto a 2D plane so the dimensions could be specified to the steel company using autocad format drawings. The main challenge I found here was untwisting the side plates of the hull. I ended up writing a little program to do this which involved incremental rotations about two axes.
The first step in the design process was to generate cross-sections every 2 feet. These cross-sections were then used to construct a 3D model. During this process center of buoyancy, center of mass, and moment parameters were also calculated to verify a design water line. The next step was to iterate on the model by adjusting the cross-sections so as to achieve a fair hull that would float properly. The final 3-D wire frame model and Half-sections are to be seen by clicking these links. After finalizing the shape I then generated the flat sheets needed for cutting out the steel parts. An example is Flat sheets (These replicas of the autocad drawings are “washed out” in order to keep these image file sizes reasonable)
To test the accuracy of my computer lofting I decided to first make a model out of steel using the exact same methods I would use for the full scale version. That is the steel company would use my autocad drawings to cut the steel at 1/12 scale and then I would assemble it using the same methods I perceived I would use for the full size boat. This involved making a keel support structure and then tacking the model together from the keel up. I even had Seaview boatyard where I plan to build the boat do the final welding of the model so I could verify their capabilities, which are very good.
So here is a picture of the The basic hull with the main bulkheads.
Here is a picture of the The final model with a wooden cabin etc.
To test that the model floated here is the proof… The model floating Unfortunately I had to use 12 guage steel for the model hull just to make welding possible. This resulted in a model which is more than twice as heavy as it should have been for 1/12 scale. So it sits a lot deeper in the water than the real boat will. However pushing it along in the water indicates it should behave reasonably well in the real world.
After family negotiations the decision is made on Sept 15, 2001 for a GO and an order was emailed to American Steel in Kent, Washington, with attached autocad drawings.
Building the hull and deckhouse.
After the decision was made on Sept 15 to Go and the order for the steel was place, events moved fairly rapidly.
After receiving my order American Steel (Mike Hanson, Himzo Huznic and others) then arranged for the 47 ft long plates to be special ordered and sent to the factory for ” wheeling” and priming. This is a process which removes the slag from the steel and applies an inorganic zinc primer (Defoe 302) to the steel. It allows the steel to be painted right after it has been assembled and welded. After the wheeling and priming the steel was then shipped to American Steel for cutting. In this process the steel sheets were offloaded from the truck onto an 80 ft long bed where the boat parts were precut according to my computer drawings using a computer controlled plasma cutter. This resulted in parts that were cut to an accuracy of about 1/16 on an inch over 47 feet.!!!
On Saturday October 19 the first shipment of steel arrived at Seaview boatyard, was offloaded , and construction was started in a tent structure they have on the premises. The first thing was setting up a support structure for the keel plates. This involved surveying in the supports to get the correct shape and to correct for irregularities in the floor. Marit and I did this on Wed. 17 and on the Saturday 19 the keel plates were installed when the steel was delivered. From then on it was me and Tad ( from the boatyard, who is an excellent welder and terrific help in setting up) putting in the engine bearers, the bottom plates, the forward bulkhead and the aft bulkhead and finally the side plates on the hull. Since these were all precut they fell into place easily and fit together very nicely. So after 2 weeks and by Nov 2 we have the basic hull all tacked together.
The next step will be fairing up the hull, putting on the decks and then welding all the seams inside and out with Tad’s MIG (multiple inert gas) system. At this stage the hull will be ready for the internal ribs, the keel and rudder and the deckhouse.
Update on December 24, 2001. The project is now just over 2 months old and the basic hull is almost complete. All the major steel pieces are installed and most of the finish welding is complete. Still remaining is to construct and put on the keel, the rudder, the propshaft tubes and the inevitable detail work. Marit took some pictures about Nov 30 and here are a few.
. Workshop and tanks. The workshop in the engine room is usable and the tanks are installed and pressure tested.
Deck The decks are all on but still need to be finish welded. Glyn was helping me on this day.
Galley The galley area is in the main cabin and we can now see where everything could go.
Transom steps I have installed steps on the transom for getting in and out of the boat and used temporary lumber for the steps while we are constructing. They are very useful
Update on January 19, 2002. Today it is 3 months since the first shipment of steel arrived at the boatyard. This is a special milestone for me because I had hoped to have the steelwork on the hull near to completion about now. In fact in a day or so we will complete the finish welding on the basic hull, so I was not too far off. The next step is to elevate the hull 5 feet so we can weld on the keel and rudder assemblies. The steel for the keel will be ordered on Jan 21 so we should be able to install the keel about 2 weeks from now. Some pictures taken near the beginning of Jan. showing the progress up to then.
This pic shows Marit standing in awe of the Deckhouse installed on the hull
This pic shows Brian sitting at the site of the future Eating table and enjoying the thought of the view of the ocean going by ( on autopilot) while eating a good meal of curried beans.
Finally some Example welds showing the hull plate seams and the ribs that stiffen them
Update Feb 26 2002. Today the hull is out of the tent with a new coat of primer paint. It is also covered with a tarp so it can endure the next 3 months without any possibilities of rusting. Marit and I leave for SA tomorrow and a break from the routine ( including recovery of Brians strained aging joints and muscles). The hull is now pretty much done. The keel is on, the rudder is on, the hull has been sandblasted and primed on the outside and so is pretty much ready for the final paint job on the outside. All that remains on the outside of the hull is to install the thru hull fittings, shaft log etc.. Over the past few weeks we raised the hull 5 feet so we could install the keel (using a small hydraulic jack), we built the keel (which consists of a 4 inch thick solid steel ballast plate mounted to a fuel tank) as a module in the shop and then cut a hole in the bottom of the boat into which it fit. We also built and mounted the rudder and its skeg, including finishing off the welding of the hull seams at the points where we lifted the boat (which required grinding a groove into which the weld bead would go). Finally we used a trailer to move the hull out of the tent and backed it into its new space outside.
At the end of May we return and will then finish of the hull, install the engine and put it in the water.
Well we returned on schedule and went right to work at the end om May. The main jobs were to finish welding the stainless rails and other fittings, painting inside and out, installing the engine, propshaft etc and testing. Doesn’t sound like much but it was a lot of work. Anyway its done and the boat is now floating and at home at our dock. There were no leaks, it floats exactly where I said it would, the weight is what I calculated (30,000 pounds), and the boat handles pretty nicely under power. So ….so far so good.
Will provide more details shortly after I have settled into the new routine at home.
Thursday Oct 10, 2002…….The launching
and then underway under its own power to home …..underway.jpg
Now we are at the end of August 2003 and the boat has a mast, rigging and some used sails and has been for its maiden voyage. More later.
For a picture see sailing3.jpg
