CNC Routers, Vacuum Bag Test and a Surf Canoe

This past week was a hodgepodge of work. The F22 building process is somewhat on hold because I'm waiting for materials to be shipped from the mainland. Hawai'i is a wonderful place unless you need to find unusual materials. Biaxial fibergass is one of these. I'm currently waiting for a large shipment of fiberglass, fillers, vacuum bagging material and laminating tools from Fiberglass Supply in Washington state. It will probably be another two weeks before it arrives. Bummer.

Until then, I have been keeping busy with several mini-projects. The first one is a test of pulling a vacuum bag on the foam surface. When I was laying the foam strips down for the core of this boat, I extended the strips proud of the keel join line and further forward and aft of the ama's overall lines. On these extensions, I covered the foam with a putty mixture of epoxy, microspheres and colloidal silica. To test the vacuum that could be achieved, I re-used a piece of bagging material from another project, recycled breather material and a single vacuum port.

The picture below illustrates this better than I can in words, but the net effect is that I was able to obtain a vacuum pressure of 12 in Hg (roughly 6psi). This is not ideal (I'd prefer around 15-20 in Hg), but it will do. I think the leaks are due to the fact that 1) air is being drawn from the deck flange, especially at the bow and 2) I am reusing bagging material with holes that have been patched with masking tape (the blue tape). I'm hoping that the actual bag will be a bit better.


























Also, the Marine Education Training Center now has a CNC router, which takes CAD drawings and converts them into computer code (G-code) to cut out patterns. We have a three-axis router and I hope to use it to cut out bulkheads, form frames, the deck and foils (daggerboard + rudder). It is so cool to watch the router process, so I have attached a video below. The sharp pitched squeaking noise is from the spindle RPM being too low. We increased the RPMs from 12,000 to 18,000 during the cut to eliminate them.




Finally, I spent a large part of the week filling and fairing a 4-man outrigger surf canoe, which I built from April to August and now just needs to be painted. I built this boat because it has a similar construction to the F22, foam core and knitted double bias (+-45/45) fiberglass with epoxy resin. It is reinforced with carbon fiber stringers for the hull and around the waes in case the canoe will be sailed (to anchor traveler, etc).

Gluing the Foam Together

This week, I did not have much time to work on the F22, as I was busy fairing a 4-man surf canoe to be primed and painted in the upcoming weeks. In addition, I also got to play with METC's newest toy, a CNC router! (I'll post pictures soon).

However, I did get to glue the foam pieces together this week with a putty consisting of epoxy, microspheres (easy to fair) and colloidal silica (for thixotropy to cling on the vertical surface).

In the pictures below, you'll notice that the foam extends proud of the keel join line a couple inches in addition to extending past the first form frame at the bow. I am doing this because I want to create an auxiliary flange to support vacuum bagging on the part itself. I really don't know if this is going to work because it depends on several variables: 1) Is the 12mm closed cell foam airtight? 2) Are the putty joints between the foam pieces airtight? 3) Will the foam want to torque after the bag is applied?

I'm going to try to pull a "test bag" on the foam to see if I can get a good seal. I'm looking to get between 12-20 in Hg in pressure.

Anyway, here is the foam bonded together (before fairing).

Thermoforming

Thermoforming is the process of heating a piece of foam to a point at which the normally rigid material becomes flaccid and conformable. It is a necessary process in building the F22 because the flat sheets of foam will not bend to fit the hull curves without breaking. In order to get the foam to bend, it needs to be heated between 200 and 220 degrees Fahrenheit (93-104C). The least expensive way to accomplish this is by using a hand held heat gun (think turbo-powered hair dryer) to bring the foam up to this temparature.

Thermoforming a 20+ foot ama in an 85F loft with a heat gun is a hot and grueling task. In addition, the heat gun creates localized heat where one spot in the foam is hot and conformable, while other spots are still cool and rigid. Heat guns will scorch and burn the foam if held in a location too long or the gun is too close to the material. In addition, due to the curved shape of the ama, the heat from the gun is redirected back from the foam to the person operating the gun. It is a hot and sweaty job, so much so that I drink 64oz of water before the day begins and I never have to use the restroom all day.

In the never ending quest to build a better mousetrap, we assembled a makeshift oven to heat the foam up to thermoforming temperature without holding the heat gun or battling the heat. We used a large foam insulated case, with plywood wedges partially opening the case and holes cut out for the heat guns (pictures below).

After heating the foam to its thermoforming temperature, the builder has about 10 seconds to get the foam from the oven onto the mold surface and conform it to shape. Using the thermoform oven was such a blessing to accomplish this task. Below are pictures of the thermoforming oven, the foam bent to the curve of the hull, the join lines of the foam covered in packing tape and the fully planked hull (4 hours total)

And Planking Begins...

Today was the first day of planking the ama with foam. To get to this point, we first needed to lay battens over the form frames to define the shape of the hull. Rather than butt battens together, which I believe creates a hard, unfair spot, I scarfed three lengths of lumber together with a 12:1 scope. I used clear Douglas Fir, 1"x4"x8' (2) and 1"x4"x"10', with the 10' section in the middle and the 8' sections on the end.

I glued the scarfed wood with WEST system epoxy mixed with 403 Micro Fibers and 406 Colloidal Silica. After the glue set (2 days), I sanded the excess off and trimmed each 24' length of lumber into 4, 3/4" battens. All in all, I had 3, 24' lengths of lumber, which produced 12 battens. I only used 10 on the ama and you can see from the pictures below how the battens are oriented.

That was the fun part. I'll get to the thermoforming in the next post. What a grueling job.

Strongback and Ama Form Frames

After some time spent culling through the stacks at the lumber yard, I now have a strongback and form frames standing. We built the strongback, or the base of the building site, out of 2"x6" dimension lumber. Ian's plans called for 1"x6", but I thought this might be too flexible and I really wanted to make the strongback bulletproof. I think it paid off and the cost of dimension lumber at 2"x6" was slighly less expensive than 1"x6" clear material.

The strongback is completely level, square and plumb by use of a transit and plumb bob and ordinary level. We shimmed the legs of the strongback to the correct height or filed down the strongback sides to attain level and plumb within a tolerance of 1mm, measured by the transit.

The form frames were lofted from the full-size patterns provided by Ian. We cut each sheet of MDF to a working dimension of 22"x48". The width (48") is not that important, but the height needs to be exact for each frame, so the 22" is right on the money. Once the patterns were lofted, we rough cut the curves with a jig saw and then sanded them down to the line.

One suggestion for new builders is to rip the MDF approximately to width (22.5") and then make a second cut exactly to width (22"), hopefully using a feather stick on the table saw to keep the material tight against the fence.

The greatest part about this process is that once you get the form frames standing, the shape of the ama is immediately apparent. You can almost envision the hull you're about to build, sitting nicely within the frames.

The pictures below show the beefy 2"x6" strongback, the assembled form frames and a light at the end of the tunnel!

From paper to wood

The construction of the F-22 ama began in earnest last week, but not in any of the ways outlined in the plans. As an effort to learn lofting and how to fair curves (at least on paper), we lofted the ama (float) of the F-22 in full size, using 3 butted sheets of masonite.

We generated a table of offsets using the DXF files I purchased from Ian. Essentially, we imported the DXF files into Autocad and took measurements from the centerline of each of the float frames. We created artificial waterlines (since the ama does not have a "true" waterline) and then compiled buttocks lines on top of that. We also lofted each frame in a body plan view. We faired the lines of the ama with a 24' wooden batten and you wouldn't believe how fair Ian's plans are!

I included some pictures in this post, if you'd like to take a look at an "old school" lofting. Sorry the ink is difficult to see, but I just could not think of a better way to take the picture becuase the ama is so long. Please feel free to let me know what you think. Aloha, Mike

First picture is body plan, then profile view, then a view of the raked transom.

Why would you ever build your own boat?

Aloha! So, for my inaugural post, I am probably supposed to write something inspiring for other boat builders in the world. What I have come to realize is that boat building is truly an art and it is an activity in which the amount of effort that is put into the project is immediately apparent in the work.

I think it would be unwise for anyone to attempt to build a boat as a means of saving money to get out on the water. Ian has predicted between 1,500 and 2,000 hours needed to construct the F22. It would be more financially sound and way less grueling to get a job at McDonalds and save the earnings to purchase a boat.

The real reason for building a boat is that it is incredibly rewarding to see the result of your time consuming and meticulous efforts. You will put a bit of your soul and a bit of your mana into the boat. At the end of the project, you will have a vessel that you are intimately familiar with to take out on the water. You can be extremely proud because you have a boat that works and you know how to fix everything on it because you built it. What a great feeling!

Anyway, enough evangelism. I am maintaining this blog to document the process of building my fifth and most important project: the Farrier F-22 Trimaran with aft cabin and daggerboard. I have built (or been on the build team of) rowing, paddling and sailing vessels in the past, ranging from a 12' rowing dinghy to a 46' sailing Hawaiian canoe, but I consider the F-22 to be my most ambitious (and most rewarding) project yet.

When I first learned about Farrier trimarans, I purchased the plans for the F-32. I was younger and more foolish than I am now and came to realize that I just did not have the time nor funds nor facility to complete the F-32. So, I traded my plans in and purchased the F-22 plans. It is my intention to keep this boat on a trailer ("dry sailed") and launch it each time I want to go out sailing.

I live in the Hawaiian Islands, on the island of Oahu. We can sail year round, so it is one of those places where owning a boat makes sense. My past boats have been a Ranger 33 and now a Hobie Getaway. I expect the F-22 will be a mix of the two, providing performance and comfort. I want to use the boat to sail between the Hawaiian Islands. I can't wait to get started on this project.