Trip on Sheepscot River, Maine

On the Back River 

Taking a break at Sawyer's Island

Paddling down the Sheepscot River

On the beach at Powderhorn Island

Dinner on Powderhorn Island

Last Details and Launching

We finished the hulls in the last week of school but were still putting on final coats of varnish on Prize Day, when we put the boats out on display as part of the final exhibition of student artwork and furniture building. Here Andrew is varnishing his gunwales as Nick looks on next to his boat. 

This photo shows the parade of boats set up along the walkway to the lawn where Prize Day takes place. The boys were able to get plenty of acclaim from classmates and parents who came to the event.

close up of Nick's boat

Boat with Prize Day Lawn behind

Finishing the Boats

After finishing the skins, we put several coats of a heavy polyurethane finish on to waterproof and strengthen the skins. We used a product developed to coat garage floors, heavy bodied and low in VOC. While we put most of the coats on outdoors, several boys put finishing coats on indoors and with fans on, the solvents did not seem to be much of an issue. 

Pat screws on the ash cutwaters we had steamed and molded to the stems back while we were steaming the ribs. Cut from the same ash stock as the ribs, these protect the seam of the skin at the stems. We joined the cutwaters and ash keels with a miter cut on each end. 

Here Hendricks on the right helps Mathias screw down the keel. Mathias is putting a bead of silicone calking in each screw hole so that water won't come through the skin where the keel is screwed to the keelson. 

Varnishing the Hulls and Applying the Skin

We did much of the final sanding and varnishing out on the lawn just outside our shop. The boats were light enough to slip out the window just behind the left hand boat in the picture. For spots that needed real faring like the sharp edges of stringers as they twist toward the bow, we used a belt sander, but most of the sanding could be done by sanding blocks with grits of 80, 100, and 220. Rather than paint on varnish, most boys applied a number of thin coats with a rag. We used Epifanes marine varnish on the boat frame, applying it in the morning and then letting it dry through the day before putting the boats back inside over night. To hold the boats in place for this right side up work,we cut sections of 2x4 along the profile of the original molds and then squeezed clamped the boat and 2x4 cradles to sawhorses.

Here Andrew is attaching the kevlar roving to the gunwale using an iron as a heat source. We used regular clothes irons and a set of small travel irons for the work on the skins, available on Amazon for about 18.00. Two students elected not to use the kevlar roving, and the boats seemed to do fine without it. However we had built frames that were substantially more rugged than the specifications in Platt Montfort's designs. 

We were all amazed at how the dacron shrunk when ironed. It was important to lay the cloth down so that the strands were set at an angle to the stringers and the ribs. We tugged the cloth tight and clamped it at the ends and to the gunwales. Then we bonded it to the gunwales and shrunk it from the middle working out to the ends. The boat in the foreground has the cloth shrunk on most of the boat and is waiting for the intricate 

This photo shows Andrew attaching a strip of the heat bond tape to the stem. This stuff works very well and makes for a much more elegant and smooth stem than the traditional technique of sewing up a rolled seam at the stems. The boat on the left shows the way the dacron is stretched over the hull and then held in place by clamps while the edge is heat bond attached to the gunwales and keelson both of which had heat bond tape set in place. 

This detail shows the dacron skin cut and pulled over the stem. Small pieces of heat bond tape have been set in between the stringers with the dacron then bonded both to them and a headband strip on the stem. In Montfort's plans, the second layer of dacron is then pulled over and bonded to a strip on the opposite side of the bow. We decided instead to cut a piece of heat bond tape down the middle, attach it to the stem and then bond the second layer at the stem, cutting off the excess. This makes for a more elegant look. With a cutwater screwed over the two layers and the skin also bonded by several coats of varnish, this modification seems to be strong enough. 

Here is a close up of the stem with the two layers bonded. To cut and seal all the edges of the dacron, we used the Engel HSGM Hot Cutter - Pro available for 169.00 from Skinboat.org. This great little tool allowed us to make the very precise cuts needed around the stringers at the ends as well as accurate cuts along the gunwales. 

Finishing the Interiors

Fitting the Inwales

Andrew clamps an inwale in place

Our inwales are duplicates of the gunwales, cut out of 3/4" stock fir. The cutting of the ends required the most complex cutting so far, really a cut with three different angles represented by the inward curve of the stem ends, the inward curve at the sides, and the joining of the two inwale pieces on the inside. We used small aluminum rulers to mark the bevels, cutting "proud" and then rasping and sanding until they fit. Since we were using thicker sections of gunwale than the original plans called for, the original joints of gunwale and stem did not always yield an easy "pointy" juncture to then match with the inwale. We needed to improvise the shape of the breasthooks, and we got to do some fun problem-solving that yielded a variety of breasthook solutions.

Colton's traditional dinghy style breasthook

Another view

Chris's breasthook designed according to Monfort's plans

Overview of breasthook built according to Monfort's plans

Floorboards

Mathias clamps a floorboard into place

We cut our floorboards from the same ash log that we used for the rib stock. The light duty table saw we used determined the width of the floorboards at a narrow 7/4" and the length of the log (10') determined the length. Advantages: they were easy to twist slightly to follow the interior of the hull and it was easy to use the stringers as a guide to placement. Disadvantages: without a cushion, they might be a less comfortable seat for paddling. We glued them directly to the ribs to stiffen the frame. While it might be  more difficult to clean the interior of the canoe, we are confident that with a little water pressure on a spray hose, we will be able to clean out food or other debris that gets under them. 

They definitely make the hull stiffer. 

Detail of 5 floorboards cut to fit and glued in place

Gussets and Thwarts

Gusset and Thwart Detail

We cut our gussets out of scrap oak and glued up thwarts from two pieces of 1/2" ash and a 3/8" piece of mahogany left over from cutting rabbets for picture frames. The thwarts need to be planed a little on the two ends as the gussets have a slight upward deflection when they are glued to the inhales and gunwales. They also need to have an inset cut to fit around the rib.

Getting Ash for Ribs and Floorboards

Because we needed a little more wood for ribs and floorboards, I got in touch with Miles Amerault who runs a one man bandsaw mill just north of Dover, N.H. He was willing to mill up a 10 foot ash log he'd gotten from a tree surgeon. Cut into 3/4" width planks, about fourteen of them, they made great ribs and floorboards. 

I brought back the planks and set my rollers up and milled up both ribs and floorboards, cutting the floorboards to 1/4" x 5/4" x 10'. The floorboards are a bit narrower than those we have seen in the pictures of built canoes. Platt's plans call for three floorboards of 23/4" width, but the 5/4" width is easier to cut with a table saw running on 110 and they are easier to shape and bend to fit the interior. 

I cut the ribs to 1/4"x5/5"x42" - a little stouter than the 3/16"x1/2" that Platt Monfort's plans call for. We'll see when we get the boats skinned up and in the water whether the extra weight will affect carrying and portaging. 

           The wood was so green that I was able to bend it into a semi-circle just after milling it up. 

By the first week back from vacation at the beginning of April, we had all the ribs in and three of the boats turned over to work on the interiors. From the left, Jamie, Colton, Andrew, Chris, Mathias, and Pat next to their boats.

A week later we had all the boats turned over with starts on the inwales, breasthhooks, and floorboards. If you look at Chris's and Mathias's boat in the top right, you can see the system of stanchions and cross braces we used to steady the boats while working on the inwales.

Steaming Ribs Movie

Here is a 90 second clip showing Colton and Nick bending a rib into Nick's Arrow 14 hull. 

The rib is 1/4x1/2 quarter sawn oak set into a hull formed from 3/8x3/4 Douglas fir stringers. They are using a 1/8x5/4 piece of Douglas fir as a backing strap to keep the outer edge of the oak rib from fraying as the wood fibers gets stretched on the outer side of the curve. They have roughly one minute before the oak cools to bend it into place.

Steaming Ribs

We are now steam bending the ribs that fit inside the stringers. You can see the steam box in the background. If you look out the window you will also see snowbanks that reach up to half the window height on the left side, indications of the snowiest winter on record here in Boston. 

Monfort's design calls for 3/16"x1/2" but we were given scrap quarter sawn oak from a toboggan building project already cut to 5/16" depth. The wood is a little harder to bend because of its relatively low moisture content, but with the ribs in place, the hull is very stiff. 

We soak the ribs for several days in a set of chambers made from PVC drainage pipe cut to 45" - just a little taller than the 42" ribs. With a cap on top of the PVC tube, the ribs sit suspended in the water which we fill to the brim. The buoyancy of the wood should put the surface of the wood under pressure forcing as much moisture into the wood fibers as possible. 

What seems most important in the bending process is to get the wood as hot as possible. We use the kind of thermometer sold for outdoor grills poked down into the steamer to make sure that we have reached close to 212 degrees before we put the wood in the chamber. The general rule for steaming wood is an hour per inch of thickness. 20 minutes works well for our ribs. 

Here is the method we have used to bend the ribs:

1. Rib positions are carefully marked on the outside of the stringers by placing a piece of surveyor's tape over the hull and marking the positions on all stringers and gunwales. That allows us to quickly get the rib into position on both sides.

2. After 20 minutes at 212 degrees, two benders are ready at the box with heavy gloves. One opens and shuts door to conserve heat, while the other fits a very bendable wooden strap to the back of the rib. We use a piece of fir cut to 1/8" depth as a strap rather than metal because we worry a metal strap would wick away the heat quickly. We start with the fir strap in the steamer and draw it out with the first rib. 

3. Both benders race to the hull knowing bending time is one minute. 

4. We place the rib and strap above the hull and bend down with pressure on the strap from both sides to keep the rib's outside edge from splintering as that side of the rib gets stretched. Quickly but gently we bend the rib to take the shape of the hull.

5. The first bender then passes the rib inside the hull and we gently squeeze clamp it at the points of maximum curve while pushing up from the ends of the rib to make sure it meets all stringers and the keelson. If the rib is sufficiently hot, it should go in quite easily - at least during that first 60 seconds. You will feel it stiffening very quickly. 

Monfort's "clamp its" work well in securing the rib to the stringers because they can be set up beforehand on the stringers and then slid over the rib. But with practice, you can also quickly secure the rib with cable ties before it cools.

The boat on the left has all but its end ribs in place, drying out before we will glue them in place. While you could laminate ribs or probably get the bend with a boiling or soaking, steaming the wood is very exciting - and a great place to learn about wood with both the successes and failures. If a rib breaks, examine the point of failure carefully and you will probably find that the wood grain has "run out" - the grain veering off toward the edge just at the break or you may find a splintery edge that should have been sanded before steaming. Small knots or other irregularities in the grain will also cause breaks. Save the broken pieces if they are long enough as they can be used later as cutwaters, cross braces for sailing rigs, or deck ribs if you sew spray covers for the ends of the canoe.

Gluing Stringers to Stems and Shaping the Stringers

Here Mathias glues and clamps the stringers to the stem as Jonathan hands him clamps. You can see how carefully he has cut the acute angles that will allow a good glue surface between stringer and stem, the product of careful measurement and work with the pull saw. 

When all the stringers are glued into place along the stem, they must be shaped with rasps and sanding blocks until they meet in a fair curve. The top stringer in this picture joins the stem with the most difficulty because it must be twisted slightly. Some builders would put it in a long thin heavy duty poly bag and steam it to accomplish a radical twist. We just gave each of these a slight twist and then will sand down the sharpest outside edge. The top stringer above still needs more sanding so that the dacron skin will fit easily around the whole bow. You can see the sanding block made with red 80 girt sandpaper fixed to a block with 3M 77 adhesive. When the sandpaper wears out, we use a heat gun to soften the adhesive and put a new sheet on with a little more adhesive on the paper. The blocks allow you to fair several stringers together to create the overall shape of the bow.

In this photo Jamie is putting a curved edge on the stringers over which we will stretch the dacron skin. Just behind him you can see the pull saws, coping saws and rasps that now do much of the work of fitting the stringers. 

Chris uses a rasp in this photo to round the edges of the stringers. Block planes would be useful in this work but we do not have a set. The fir is soft enough that the rasp can do the work quite easily.

                 Here you can see the top stringers now rounded as they comes to meet the stem. 

Gluing Up the Gunwales and Stringers

Tools

The tools we've used have followed a progression from left to right with the levels most important at the start to make sure that the station molds and stanchions all would sit in a parallel set of planes and give the canoes a symmetrical shape.

We used the glue guns to anchor cleats to the cardboard and temporarily set the stems on the center line of the strong backs. We also use them for many small tasks like glueing scraps of wood together as jigs. The plastic bag just above the glue guns holds bandages and first aid. 

At the far right, you can see part of one of the eight plans we have posted around the studio so each builder can check the details and building instructions. A bulletin board holds pictures of finish details from previously built skin on frame canoes.

We put these pictures from Tom Loeser's sculpture exhibit "Flotilla" up on the board as a cautionary reminder. 

Tom actually built these sculptures by taking Platt Monfort's designs and shifting the stations so that the boats would bend and curve. We know that if we don't get the molds straight and true, we could easily build a boat that keeps turning left.

At the strong backs

Each builder has a mat knife and two bins, one with zip or cable ties and one with "clamp its," an ingenious wire clamp that Platt Monfort invented to help in holding parts together while gluing. They can be easily adjusted so that you can control the pressure while gluing. Too much pressure from a clamp, the problem with spring clamps, and you can squeeze all the glue out of the joint. Too little pressure will yield shifts in alignment or too little contact between the members. The bins are made from recycled lemonade cartons from our dining hall. 

We use cable ties to hold the stringers down to the stations by poking a hole in the cardboard and then securing the stringer so that it doesn't pop up and distort the hull when the ends are glued to the stems or the ribs are put in place.



We also use them to glue stringers to stems if we run out of clamps - which happens most every day. Chris is our most artful cable tie clamper. As you can see in this photograph, he leaves the ends of the stringers sticking beyond the stem. He puts one tie on the inside of the stem, one outside, and then ties them together with a third he can use to position the stringer and control the amount of pressure on the the two vertical ties. We wear gloves for all work with glue. 

Steam Box

I built a steam box to bend the oak ribs in our school's shop using scrap plywood, the frame of a futon that someone put out on trash day, and oak dowels. 


Andrew measuring for a cut on one of the bottom stringers which have a complex twist as they join the stem.

All of the stringers had to be cut at complex angles where they joined the stems and then glued using a two part epoxy. To adjust and refine the angled cuts, we used strips of 80 grit sandpaper attached to stiff cardboard with 3M 77 spray adhesive. If you pass the sandpaper back and forth between the stringer and stem with the rough side facing the stringer, you can make the fit very precise.

Sanding blocks to adjust cuts to stringers as they meet stems

We mark uncut pieces that stick out into the center of the studio with orange 

so that we won't bump into them when walking between boats.