America to Japan Crossing - The Trimaran |
| Ama - Step 5 |
| Building an Ama (Strip Planking) |
| 1) |
Cut almost a full 4x8' sheet of 1/2" plywood into 1.5", 2" 2.5", 3", 3.5" 4.5" 6", 7.5" and 9" strips wide and about 12" long. After that we routed the cove and bead into the strips. |
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| 2) |
We then laid the sizers into the mold and figured out what sizes we should use. This was a great idea that we got from Andre Bilodeau's Book "Building Your Hull with The Bead & Cove Foam System". He said to use them as you work and cut the strips, but we used them to make a cut map for the foam. Here is Miki working out the strips on our main station (Station #12). We did it over and over until we were happy with the gaps and the number of strips that will be used. |
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From this we were able to figure out the key strip (A strip that will be coved on both sides allowing the cove to always be on the up hill side of the part your working). In this case our key strip will be a 4 1/2". |
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We sized about every other station. This helped us to see what strips needed to get resized as we went. One other thing we found to be useful is a 1/2" batten with a cove and bead cut into it, this allowed us to set our Key strip on every station. I spent a few hours in Visio making the cut map, while running outside at 1:30am to verify the numbers we had written down earlier in the day. |
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After the cuts were laid out I then moved them all into groups of like sized strips over a 4x8' box. Then it's just a drag and drop until each sheet is complete. Also accounting for blade width and waste. The visio file stated we will need 5 sheets of 5# foam and 2 sheets of 6#. Now for the test, we will not know if this is good or bad until we have routed the cove and bead into each strip. (The strips in the gray/dotted strips in the above cut map are where the 6# foam will go). |
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| 3) |
After building the cut map Miki and I set out to cut the foam into the 8' basic lengths at all the different widths called out in the cut map. |
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After a few hours of cutting the strips on the band saw, we had all the strips were called out. Total foam usage is about 5% more then was in the budget; this added to the other 20% what is lost to the cove and bead. The foam budget is now calling for a load more foam than we thought was going to be needed. The original 10% loss was erroneous, and we still have yet to glass a part. |
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We needed to cut 1/2" PVC pipe down to use as battens. This will be screwed into the foam between the stations to stop sagging. These were split into 1/4 and drilled holes about every inch. |
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The router table setup with a 1/2" Bull Nose bit. Miki and I routed all 66 of the strips in just under two hours, with a large break during the bit change (actual time spent was about an hour). The Bull Nose bit gives the foam a rounded over edge called a bead, the other bit we use is a 1/2" Internal Radius Bit it is used to create a dished out surface called a cove. |
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At the transom or aft end of the ama we needed to set our lines. The flat end on the left side of the picture is the keel with the right side being the deck. When it is completed we will have a fold down ladder acting as a swim/dive step. |
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The keystrip is laid just below the transition on to the deck, at the lowest section of the hull. The keystrip has a cove in both sides, this allows us to put bonding compound into the cove facing more up. |
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Once the keystrip is in place both sides can be worked at the same time. Here I have laid out the deck on one side and the bow on the other. It is a two sided jigsaw puzzle. |
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After bonding the deck, we started the jigsaw puzzle on the keel side. Builders Note: Cut more of every size strip then you think you'll need, stopping and making a 6" into two 3" strips at this point is just a waste of time. Also, get two routers, If you only have one (like us) then leave it setup with your cove bit, as it is easy to add a bead with a sanding block. |
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John, Sam and I worked the jigsaw puzzle for a few hours. We made due with the sizes we had already cut, it came together very well. We only needed to taper 2 small strips to complete the bends. |
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Here is the completed jigsaw puzzle. The desk section has been bonded to the key strip. |
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All the strips labeled and stacked up ready for bonding, note the PVC battens between every station. |
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Using wood battens to curve the PVC battens to insure the shape is maintained. |
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Here is Miki with her ZipLock pastry bags of bonding comp. |
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Here is Jeff attempting to mark the cut line. Kodiak really likes Jeff, and needs to play even when Jeff is attempting to work. |
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Here is the completed foam work, it was a good weekend. My plans to have the ama half glassed over the weekend were a little sort sighted. We need to learn how to work with the bonding compound, and spent more time in layout. If I can get the remaining foam bonded, we will glass over the weekend, else it will be a bonding fest with a bulk or two glassed. |
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