Cradle Boat for Vormulac

[SketchUp Guru]

Vormulac, you mentioned that you might want to build a cradle of the sort I built. I zipped out a quickie drawing to give you an idea of how I started. It's actually fairly simple to do. I can give you more detail about building it and make dimensioned drawings if you'd like them.

 

[Vormulac]

Hi Dave,

Thanks for that. I'm really impressed by your design and would love to see any additional details about the construction. I think this would be a really good project to break in my workshop when it's finally complete!

Thanks!

Vormulac.

 

[SketchUp Guru]

I'll work up some details and post them. If you have specific questions, feel free to ask. I might miss something.

 

[Vormulac]

Thanks Dave, I'm looking forward to this!

V.

 

[SketchUp Guru]

Let's see how this goes for a start.

Bow Transom

This is the aft face. The edges will get beveled after the building form is completed. You have to figure out the bevels by wrapping a flexible batten over the forms. the batten and thus the planks should lay fair on the bevels.

The notch shown is for the keelson. It should be 1/4" deep. ( I drew it deeper than that so it would show better in the overall view. See below) The notch is cut after the form is setup.

Form No. 1

This won't get beveled but will get a beveled notch. The notch depth is determined in the same way as the bevel on the transom.

Form No. 2

No bevel. The notch on this one is straighforward. No bevel required in the notch which is 1/4" deep.

Form No. 3

Treated the same as No. 1

Stern Transom

Mounted vertically. It gets a notch similar to the bow transom. Again, the notch is cut after everything is set up.

Form Spacing

Note which face of each form is located at its station.

The forms and stern transom are mounted vertically and must be parallel to each other. The bow transom is 12° from vertical. Be sure to align their centerlines so the boat will be symmetrical. I made the forms out of MDF. Plywood will work or you could build open forms out of inexpensive framing lumber as long as it is straight.

Use scraps to attach the forms to the base board. the dimensions of the base board aren't critical but it needs to be straight and flat. There is no sweep to the sheer on this boat so the the top edge of the top planks (sheer strakes) will fall along the outermost corners of the building frames. Keep in mind that you will need to be able to reach up inside the boat with your hand and with clamps so make the base board narrow enough for that.

There are knees that join the bow and stern transoms to the keelson. I haven't drawn them yet but they are made extra long. The transoms are attached to the base board through the waste portion of the knees and some other blocking so there will be no screw holes to fill later.

The next installment will come sooner or later.

 

[SketchUp Guru]

I guess it will be sooner.

Keel Section

This shows a section of the keel and keelson at the Form No. 2 Make the keelson 2" wide and 3/8" deep. The length will be determined by fitting so measure and make it extra long. Glue it to the transoms in the notches you've made. Mark the location of the keel on the keelson. Then using a shoulder plane, take down the bevels on the keelson so that they match the angles of the garboard planks. Attach the keel after you're pleased with the bevels.

Bow and Stern Knee

Leave the waste attached and use it along with some scrap blocking to attach the transom to the base board at the correct angle. The exact shape is up to you. Make it a pleasing Cyma shape. The angle between the transom face and the keelson face (up in this view) will be determined from the keelson. A small sliding bevel is handy here. You'll find it worthwhile to work with some inexpensive wood to make patterns for these pieces as you go.

The knees should be glued and screwed to the transoms from inside. Counterbore the holes so they can be plugged later.

 

[Vormulac]

Wow! Thanks Dave! :shock:

I am looking forward to getting to grips with this! A great project for the summer

V.

 

[SketchUp Guru]

You sound excited. I hope you'll shows us some WIP photos as you go.

Here are a couple more drawings. The show the bevels on the planks and how they lay over each other.

Before you get to planking, make sure the forms are symmetrical. This will make the planking much easier.

The garboard plank (bottom-most plank) has a straight edge along the keel. Start with plank pieces that are a few inches longer than you need. I used 1/8" thick clear pine which was resawn from thicker stock and planed to thickness. The plank blanks were 5 1/2" wide which is plenty for this boat. Bend the plank in place and clamp it down. Clamping it at the ends is tricky but it can be done. Put some blocks on the building forms or bore some large holes in them so you can clamp the plank on its outboard edge. Make marks on the underside of the plank at the chine points on the building forms and transoms. Make sure you work on the proper side of the building forms and mark at the outside of the transoms. I traced a light line on the underside of the plank along the face of the building forms. This made it easier to align the plank properly after shaping it.

Remove the plank from the boat and lay it on the bench inside face up. Bend a thin batten so it passes through the points you marked. Trace the batten to get the curve on the plank. Tape the other garboard plank to the first outside face to outside face. Bandsaw the pair to just proud of the curve you drew. A block plane will make quick work of cleaning up to the line.

Glue the garboard planks in place. I used epoxy. Clamping the first is easy enough because you can clamp around the keel. The second one takes a bit of ingenuity. I sued my planking clamps for this since they would reach across the width of the plank. I drilled for and then nailed the hood ends to the transoms with bronze ring nails. Don't do this unless you're sure because those nails are a bear to remove.

After the glue has cured, remove the clamps and cut the bevel on the garboard to receive the next plank. This is quickly done with a block plane. You can either eyeball the bevel between the building forms or bend a batten over the next flats on the building forms and transoms to give you a runner to guide the plane along. Just clamp a block of wood to the plane so the block rides on the batten.

Once the bevel is completed on both garboard planks, clamp the next plank blank in place, mark it along both edges, connect the marks, saw out the planks and fit them, glue them in place and repeat until you've gotten all the planks on.

This will give you an idea of the bevels. There's no need to cut gains (the sloping rebates used at the ends of planks especially on boats with pointy ends.)