Cutting rib templates for Boats

[Rob Wright]

I decided to start a new long term project this weekend - building a Adirondack Guide Boat. I have gone back and forth about building rib or ribless but have ended up going with the more traditional ribbed design.

I started by lofting the offset tables in AutoCAD to build the rib templates. I will use the rib templates as a top mount template to flush cut the laminated strips on the router table after they have been laminated on forms created from the rib templates.

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I then converted this to a dxf file for importing into VCarvePro to cut the rib patterns out on my home built CNC.

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The rib templates took about 5 minutes each to cut. My wimpy machine only cuts at 10-inches a minute and I decided to cut them in one pass with a 1/8" spiral up-cut to avoid some of the backlash problems that I have been having.

I had envisioned being able to cut the rib templates out full size and then use these "ribs" to construct the forms that will be used for bending and laminating the spruce strips that will actually form the ribs of the boat. The forms need to be of the of the interior surface of the ribs. I had then hoped to use the rib templates as a top mount template to flush cut the rough blanks of the laminate forms on the router table. This was not to be since I need the other side to properly use a router to cut these out.

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Continued....

[Rob Wright]

I needed to cut a form for the inside of the curve of the ribs to properly laminate the inside of the ribs. This is not possible with only the ribs (above). I started to sand the forms down with a belt sander - then it hit me - I have the shape I need on the cut-outs of the ribs from the CNC. I was lucky in that I was lazy when I nested the items to have a fair amount of space between the ribs. This allowed for the outside of the inside of the rib to be used as a template when mounted to the scrap.

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I cut these apart and mounted them onto a rough cut blank with screws. I was then able to use a top mounted flush trim bit to shape the forms to the exact shape of the inside of the ribs without having to spend the time to sand to the traced outline. It ended up working out just how I wanted - just through a backwards way.

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Two things learned this weekend:

1) Use the lead and ramp setting in VCarve to get better results I was having problems in the first few I cut when the router would return to the start point - the ramp/lead setting solved this.

2) It always isn't the best to nest your parts so close together that there is little or no waste. It saved me from having to cut 13 new templates for the outside!

- Rob