How to 3D print a jig for cutting puzzle joints with a router.

 

Building a plywood boat over 8 feet in length always involves joining two or more sheets of plywood end-to-end.  There are several ways to join the sheets.  Scarf joints, butt joints, and puzzle joints are three popular methods.

Scarf joints are the default method unless you’re assembling a kit boat.  Scarf joints are strong, offering a large glue surface.  They handle bending forces well and they bend in a fair curve.  However they can be difficult and time consuming to cut accurately, and they can be difficult to align precisely when joining the panels.

Butt joints with butt blocks are very simple and easy to make.  They align precisely and they’re strong.  Their downside is they may not bend fairly.  They can create a flattened area due to the double plywood thickness at the join.  They are functional, but unattractive inside in a visible area.

Puzzle joints are virtually always found on CNC cut kits.  They can be as strong as a scarf or butt joint provided the size and shape of the puzzle is designed properly and the joint is fiberglassed on both sides.  They look rather attractive finished bright, or are invisible inside and out when painted.  They handle bends without deformation.  They precisely align and interlock the sheets of plywood making joining precise and foolproof.  However, puzzle joints require a high degree of precision to cut accurately – precision that a CNC machine offers but a homebuilder simply cannot match without an accurate jig.

The puzzle joint

For quite some time I envisioned a router jig that could cut puzzle joints using a flush trim or pattern router bit.  A 4 foot long jig made of aluminum or plastic would work great for splicing sheets of plywood.  Armed with such a jig I wouldn’t need an expensive CNC machine to cut puzzle joints.  The problem is I’d need an expensive CNC machine to cut the jig.  That’s when the whole idea goes all recursive.

But wait!  3D printers are becoming commonplace now.  They’re getting inexpensive and they’re accurate to 1/10 of a millimeter.  Woodworkers 3D print templates for all kinds of projects, like cutting boards for example, all the time.  3D printers can’t print a jig 4 feet long, but they’re more than accurate enough to print a jig that can be assembled in multiple pieces. 

This is my 3D printed puzzle joint router jig.  Each identical piece is 6 inches wide.  They snap together at the sides using smaller puzzle joints.  You can assemble as many as you like; 8 of them would span a 4 foot sheet of plywood.

Attach the assembled jig aligned to the end of a sheet of plywood using your choice of double-sided tape, clamps, screws or small nails (numerous small holes are provided).  Then use your router with a flush trim or pattern bit to route the puzzle joint.

To learn all about making and using 3D printed router templates watch this video:

How to make and use 3D printed router templates

The jig is designed to leave a 1/2 mm gap between the plywood sheets when they’re assembled.  The gap is there to prevent the glue joint from being starved of epoxy.  Use thickened epoxy in the joint and cover the joint on both sides with a strip or two of fiberglass approx 200mm (8") wide.  The smaller puzzle joints that connect the jig pieces together have no gap.  They are designed to snap the jig together tightly for accurate alignment with no movement.

I am making the 3D printer file available free of charge for downloading here.  You are welcome to download and print this jig on any 3D printer.  My printer is a Creality Ender 3V3 KE.  It informs me that the cost of filament to print each piece of the jig is about $1.50, so a set of 8 costs about $12 USD.  I use PLA filament, which works fine, but be aware that PLA softens at 60c/140F and degrades over time under direct sunlight.  Mine takes about 90 minutes to print each piece, or 12 hours total print time for a set of 8.   The pieces stack up and store away neatly when not in use.

To download the .STL file for the jig to print on your 3d printer click here:

Puzzle Joint Jig.stl 

3D printer settings for best results:

• Layer height               0.2

• Seam position            Aligned. Paint the seam located near center of straight edge

• Wall printing order      Outer/Inner

• Sparse infill density    15%

• Sparse infill pattern    Rectilinear

• Supports                    None

• Skirt loops                 1

• Brim                          None
  

 

Balance Lug Cat Yawl sailplan for Navigator

There's been quite a lot of interest in a Balance Lug sailplan for Navigator lately. John Welsford drew plans for a Cat Yawl with a Balance Lug main and mizzen a while ago and posted it online.  He granted me permission to post the plans here to make them easier to find, so here you go.

The Balance Lug is a very popular sailplan for small boats.  This rig, with its unstayed mast and lack of a jib & bowsprit, is much simpler and quicker to set up and take down.  The mizzen provides its usual advantages such as heaving-to and balancing the helm.  Several Navigators have been built using this rig with their owners giving it an enthusiastic thumbs up. Personally, however, my preferred rig is still the Gaff rig for its ability to instantly drop the main and sail deep reefed under jib and mizzen. That's well worth the extra setup time to me.  For those accustomed to conventional sloops I recommend the cruising sloop rig for slightly better upwind performance.  With so many Navigator sailplan options (7 total I believe, although some are unpublished) surely there's one to suit anyone's needs. 

Note that the main mast on this Balance Lug rig is located forward of bulkhead 2 whereas the Standing Lug and Gaff rigs have the mast located aft of bulkhead 2.

Some builders have asked if it's possible to retrofit an existing yawl rigged Navigator over to use this sailplan without moving the main mast forward of B2.  John says No - the result would be an excessive amount of weather helm.  I asked him if the sail area of the mizzen could be reduced to compensate. He said the mizzen would then be so small it would become ineffective.  A new mast may be required as it's taller and may need to be stronger as it's unstayed.  So yes, anything's possible but it would require some considerable rework.

Click here to download the Balance Lug Cat Yawl sailplan

CNC files for Welsford Sherpa - FREE

If you're unfamiliar with CNC files, they are 2d vector (.dxf) files that you can bring to a CNC operator.  He will use these files with his CNC machine to cut your parts out of 4x8 foot sheets of plywood, thus creating a partial kit for your boat build.  Below, you can see which parts will be cut out and produced by your CNC operator for this boat (click to enlarge).

This will save you a tremendous amount of time, material, and possibly mistakes vs drawing the parts full size and cutting them out yourself.  Note however that not all parts are included.  Parts such as bulkheads, centerboard cases, transoms, doublers, lower panels, planks (on some boats) and other parts that are defined on John's drawings are included, but parts that are cut-to-fit parts usually are not.  Cut-to-fit parts include parts like seat tops, decking, and usually planks. Those parts are made by clamping an oversized piece of plywood to the boat, tracing the outline of the part, then removing and cutting out the part. Also, some parts may be intentionally oversized by design so that they may be trimmed to the exact size on installation.  Better they be too big than too small.

These CNC files are licensed by John Welsford and provided free of charge under the following conditions:

1. You must purchase one set of plans from John Welsford per use of these files.
2. I take every precaution to ensure the content of these files is current and accurate, nevertheless the files are provided "as is" and without warranty.  Use them at your own risk.
3. Minor alterations may be needed to the files for things like hatch sizes or other customizations.  Contact me if you need assistance with that

Click this link to download the CNC files for this boat

Full size paper templates are also available for purchase from Duckworks.  Click here for more info.

 

CNC files for Welsford Walkabout - FREE

If you're unfamiliar with CNC files, they are 2d vector (.dxf) files that you can bring to a CNC operator.  He will use these files with his CNC machine to cut your parts out of 4x8 foot sheets of plywood, thus creating a partial kit for your boat build.  Below, you can see which parts will be cut out and produced by your CNC operator for this boat (click to enlarge).

This will save you a tremendous amount of time, material, and possibly mistakes vs drawing the parts full size and cutting them out yourself.  Note however that not all parts are included.  Parts such as bulkheads, centerboard cases, transoms, doublers, lower panels, planks (on some boats) and other parts that are defined on John's drawings are included, but parts that are cut-to-fit parts usually are not.  Cut-to-fit parts include parts like seat tops, decking, and usually planks. Those parts are made by clamping an oversized piece of plywood to the boat, tracing the outline of the part, then removing and cutting out the part. Also, some parts may be intentionally oversized by design so that they may be trimmed to the exact size on installation.  Better they be too big than too small.

These CNC files are licensed by John Welsford and provided free of charge under the following conditions:

1. You must purchase one set of plans from John Welsford per use of these files.
2. I take every precaution to ensure the content of these files is current and accurate, nevertheless the files are provided "as is" and without warranty.  Use them at your own risk.
3. Minor alterations may be needed to the files for things like hatch sizes or other customizations.  Contact me if you need assistance with that.

Click this link to download the CNC files for this boat

Full size paper templates are also available for purchase from Duckworks.  Click here for more info.

 

CNC files for Welsford Tender Behind - FREE

If you're unfamiliar with CNC files, they are 2d vector (.dxf) files that you can bring to a CNC operator.  He will use these files with his CNC machine to cut your parts out of 4x8 foot sheets of plywood, thus creating a partial kit for your boat build.  Below, you can see which parts will be cut out and produced by your CNC operator for this boat (click to enlarge).

This will save you a tremendous amount of time, material, and possibly mistakes vs drawing the parts full size and cutting them out yourself.  Note however that not all parts are included.  Parts such as bulkheads, centerboard cases, transoms, doublers, lower panels, planks (on some boats) and other parts that are defined on John's drawings are included, but parts that are cut-to-fit parts usually are not.  Cut-to-fit parts include parts like seat tops, decking, and usually planks. Those parts are made by clamping an oversized piece of plywood to the boat, tracing the outline of the part, then removing and cutting out the part. Also, some parts may be intentionally oversized by design so that they may be trimmed to the exact size on installation.  Better they be too big than too small.

These CNC files are licensed by John Welsford and provided free of charge under the following conditions:

1. You must purchase one set of plans from John Welsford per use of these files.
2. I take every precaution to ensure the content of these files is current and accurate, nevertheless the files are provided "as is" and without warranty.  Use them at your own risk.
3. Minor alterations may be needed to the files for things like hatch sizes or other customizations.  Contact me if you need assistance with that.

Click this link to download the CNC files for this boat

Full size paper templates are also available for purchase from Duckworks.  Click here for more info.

 

CNC files for Welsford Sei - FREE

If you're unfamiliar with CNC files, they are 2d vector (.dxf) files that you can bring to a CNC operator.  He will use these files with his CNC machine to cut your parts out of 4x8 foot sheets of plywood, thus creating a partial kit for your boat build.  Below, you can see which parts will be cut out and produced by your CNC operator for this boat (click to enlarge).

This will save you a tremendous amount of time, material, and possibly mistakes vs drawing the parts full size and cutting them out yourself.  Note however that not all parts are included.  Parts such as bulkheads, centerboard cases, transoms, doublers, lower panels, planks (on some boats) and other parts that are defined on John's drawings are included, but parts that are cut-to-fit parts usually are not.  Cut-to-fit parts include parts like seat tops, decking, and usually planks. Those parts are made by clamping an oversized piece of plywood to the boat, tracing the outline of the part, then removing and cutting out the part. Also, some parts may be intentionally oversized by design so that they may be trimmed to the exact size on installation.  Better they be too big than too small.

These CNC files are licensed by John Welsford and provided free of charge under the following conditions:

You must purchase one set of plans from John Welsford per use of these files.
I take every precaution to ensure the content of these files is current and accurate, nevertheless the files are provided "as is" and without warranty.  Use them at your own risk.
Minor alterations may be needed to the files for things like hatch sizes or other customizations.  Contact me if you need assistance with that.

Click this link to download the CNC files for this boat

Full size paper templates are also available for purchase from Duckworks.  Click here for more info.

 

CNC files for Welsford Pilgrim - FREE

If you're unfamiliar with CNC files, they are 2d vector (.dxf) files that you can bring to a CNC operator.  He will use these files with his CNC machine to cut your parts out of 4x8 foot sheets of plywood, thus creating a partial kit for your boat build.  Below, you can see which parts will be cut out and produced by your CNC operator for this boat (click to enlarge).

This will save you a tremendous amount of time, material, and possibly mistakes vs drawing the parts full size and cutting them out yourself.  Note however that not all parts are included.  Parts such as bulkheads, centerboard cases, transoms, doublers, lower panels, planks (on some boats) and other parts that are defined on John's drawings are included, but parts that are cut-to-fit parts usually are not.  Cut-to-fit parts include parts like seat tops, decking, and usually planks. Those parts are made by clamping an oversized piece of plywood to the boat, tracing the outline of the part, then removing and cutting out the part. Also, some parts may be intentionally oversized by design so that they may be trimmed to the exact size on installation.  Better they be too big than too small.

These CNC files are licensed by John Welsford and provided free of charge under the following conditions:

1. You must purchase one set of plans from John Welsford per use of these files.
2. I take every precaution to ensure the content of these files is current and accurate, nevertheless the files are provided "as is" and without warranty.  Use them at your own risk.
3. Minor alterations may be needed to the files for things like hatch sizes or other customizations.  Contact me if you need assistance with that.

Click this link to download the CNC files for this boat

Full size paper templates are also available for purchase from Duckworks.  Click here for more info.