Monday, October 13, 2014

Building a 1/12th scale canoe

     OK!  This is the process I go through to build a one inch scale canoe.  This particular project will be a 16 footer in one inch scale, made of cherry wood.  It will be a "plank on frame" construction, using 1/16" x 3/32" strips of cherry wood.

     I start with a jig I made for the basic shape and size of the boat I want to make.  I call it a "strongback".  The strongback pictured is for the 1/12th scale, 16 footer I'm making now.   I also have jigs for a one inch scale 12 foot canoe, and for two different types of rowboats I like to build.  The base of the strongback is made of very strong apitong wood, and the forms are made of basswood.  I reinforced the forms with a triangle wedge for strength.  The middle form is the widest, the 2nd and 4th forms are the same size, as are the end forms.  There is a notch in each, on both sides, where the first plank for both sides rests.  A lot of tension is put on this strongback while planking the canoe, so it must be able to withstand this pressure.  The canoe is built upside-down with this type of construction.

The first pieces of the canoe are called "stems".  I cut out a piece of paper and trace it on a piece of 1/8 inch thick cherry wood.  I'll need two of these.  One for each end of the canoe.

I cut out the stems using a jewelers saw with a very fine blade, as close to my pencil marks as I can.  After it is roughly cut out, I use my Dremel to sand the pieces to the exact shape.

Here are the two finished stems, ready to glue to the strongback.

I use two types of glue for building boats.  The main glue I use is slow setting CA.  (Cyanoacrylate, super-glue type adhesive).  I like the "Loctite Gel Control" type, as it gives you a bit of time to align the parts where they need to be, before they set permanently.  Here, I have glued the stems in their pre-determined location, at each end of the strongback.  I put a shim underneath each stem, to make removal easier once the canoe is done being planked.  I make sure the top of the stem is exactly 1/16" above the upper edge of the forms, because this is where the bottom plank goes, and it needs to rest on top of them.

The next step is to install the bottom plank to the ends of the stems.  It is VERY important to glue this plank on straight, and to LIGHTLY glue it to all the forms below it.  I leave the ends roughly cut, and will sand them smooth later.

Now comes the fun part!  Planking!  Each plank must be beveled to the correct angle on each end before it is glued to the stems.  I usually bevel one end, and glue it in place like this:

Once the one end is dried completely, I bend each of the first planks (on each side) to the other end of the strongback, and glue them in place, making sure they rest in the notches.  Only the beveled ends of the first planks are glued to the stems, not to the forms.  The forms are for shape ONLY, and the planks rest against them to create the shape of the canoe.  Once I have the first planks in place, it looks like this:

After gluing the first of the planks in place, I double check to make sure the bottom plank is straight.  Bending the planks, and gluing them to the stems on the strongback, puts a lot of strain on the structure of the canoe. It is important to plank each side, one plank at a time, as I go up, to avoid any warping.

Now, it's just a matter of gluing the next planks to the stems and to each other.  It's important to get each successive plank as close as possible to the one below it.  Small differences will be sanded out later, once planking is done.

Here's the second layer going on:

Here, there are 5 layers of planks completed on both sides.  The process continues the same way, and is quite easy, in my opinion, until I reach the curves of the forms.  Again, the planks are only glued to the stems, and each other, as tightly as possible.

7 layers completed:

Now, beginning with the eighth layer of planks, I am approaching the rounded edges of the forms, which makes planking tricky.  Bending and twisting the wood strips to fit the forms tightly and on top of each other is time consuming.  It also puts a tremendous amount of pressure on the strongback, so it is important to glue them to each other well.  As you can see, the ends of the planks over hang the stems a bit, but this will be sanded flush once all the planks are installed.

By the 10th layer, the planks are beginning to take shape around the form curves.  It is unavoidable to make small steps going upward, while I stack the planks on top of one another.  This also will be sanded out, once all the planks are in place.  You can see these steps on the second picture.

The 14th layer of planks on both sides reaches the location where the stems meet the bottom plank.  From here on out, the bottom of the canoe is being made by the planking process.

The 15th layer of planks must now be glued to the bottom plank, and to each other, since there is no more stem material.  This will create the bottom portion of the boat.  They also have to be cut and shaped a different way in order to fit correctly, as compared to the planks on the sides of the canoe.  This is another reason why the bottom plank is glued to the forms, so it stays straight when these planks are applied.  Again, all rough edges will be sanded away, but it's best to fit them as closely and as snugly as possible.

There is a lot of pressure on the wood strips as the planking continues, and they do not want to stay against the forms.  It is important to keep pressing them against the forms as I glue them in place, and wait till the glue dries before letting them go.  Here, you can see the gaps this pressure creates as the planks want to warp.  I have to wedge a sharpened bamboo skewer against the bottom plank as I glue one end in, so I have room to apply the glue to the leading edge of the adjacent one.

Slowly getting there!  It takes patience to bend and twist the boards, and to wait for the glue to set before going on to the next layer.  In the 3rd pic, you can really see that the outside looks pretty rough, but this will easily be sanded out once all the planks are done.

Getting closer to the bottom, it is impossible to glue just one end of the last few planks in place, and finish gluing it in a bit at a time.  There simply is too much pressure on them.  I have to cut and shape the entire plank, dry fit it up to make sure it fits perfectly, then remove it and glue the whole thing in at once.  This can be difficult, because the glue cures so quickly, and you get glue residue on your fingers, so it must be quick!

Finally, the last two planks go in, to complete the bottom.  The very last one takes a bit of time to sand it to shape, dry fit it, and to make sure there are no huge gaps.

Now that the main body of the canoe is planked, I clamp the strongback to my desk, and sand the hell out of the entire outside of the boat.  I start with 100 grit sandpaper, and end up using 220 grit, to get rid of most blemishes.  The strongback keeps the canoe rigid while its sanded.  I save the sawdust created, just in case, to fill any huge mis-alignments or gaps, and mix it with the glue to form a type of putty, and re-sand if necessary, once I fill them in.  When its mostly smooth, I cut the extended stems off the strongback, and remove the canoe.

Here is the canoe fresh off the strongback.  Care must be taken to remove it, as some glue residue seeps through to the forms, and the bottom plank was glued to them.  You don't want anything to break at this point in time!  I'll sand the inside of the boat soon, but there's one more step to do first.

I like to add a few more planks to the upper end portion of the sides, but there isn't room to do it while the boat is held by the strongback.  So, after removal and a partial sanding, I add three more planks to the top of the canoe sides, on both ends, to create a little more of a curve to the top edge.  I use a pencil to draw out the material I want sanded away, and use my dremel to sand them into the shape I want.  Then, the outside is done, besides a final sanding.  It is too weak now to sand the outside any further, so the next step is to add ribs to the inside to strengthen it.

After sanding the inside of the canoe lightly, it's time to add the ribs.  The interior ribs help strengthen the canoe.  After all, the hull is only 1/16 of an inch thick, so it'll need reinforcement.  I put my ruler inside the canoe, and make a mark every 3/8 of an inch, on the center, bottom plank, the whole width of the boat.

I use cherry strips for the ribs, and they are tiny!  They're 1/16" wide x 1/32" thick.  To make them bend easier, and to conform to the interior shape of the canoe, I soak them a couple at a time in a solution of 50% water and 50% ammonia.  The ammonia helps the water evaporate quickly, and the super-glue will stick, even if they are still a little moist.  I use a fork to keep them submerged for about 10 minutes.

Once the ribs are pliable, I clamp 2 or 3 to the inside of the canoe where they are supposed to go, and use my light to speed up the drying.  Once they are dry, I take them out, and glue them in place.

It is important to keep the ribs straight with each other, flat on the bottom, and tight against the sides of the canoe.  Adding them to the inside creates strength, since the hull is so thin.  I can only do a few at a time, so patience is a virtue.  It's a time consuming process.