The South Haven Dory is a one-person rowing boat that is based on lines of the St. Pierre dory, a traditional dory hull shape. The construction method is plywood/epoxy/composite (stitch and glue) with no building mold. It is not an "instant" boat; there are many steps to go through and the result is a strong yet lightweight hull that uses the best properties of plywood and composite construction. This project is an attempt to create a boat with modern construction methods that has beautiful traditional lines. The design can be built out of three sheets of 1/4" plywood with a half sheet or so of 1/2" plywood and 1/2"x2" stock as framing. The wood can be purchased at any building supply store. The bottom is sheathed in a 6 oz fiberglass cloth.
The completed boat is light enough that a strong person can carry the boat a short distance, so the boat can be car-topped or trailered. An estimate for total cost is a little over $300. The boat is very fast under oars and is an excellent introduction to recreational rowing. It is stable if you are used to canoes and kayaks, but not as stable as a fishing boat (for example). I have been able to stand up in it in flat water, but it is a balancing act. The best part about this boat is dropping the anchor and napping in the sun in the front of the boat. You can tell yourself that after rowing, you deserve to relax. I have written these instructions for someone who has had experience with epoxy and stitch and glue techniques, however a beginner could build this boat with help of a book such as "Devlin's Boatbuilding" by Sam Devlin.
If you are considering building this or any boat, I would recommend that you build a model first. I believe that the offsets and information on this page are correct, but I have not built a boat using this document yet, so you might want to make sure the panel shapes fit together before cutting up your ply. I took the information from my notes that I used to build my first dory, so I am fairly certain that the information is correct. I hope to check the lines by building another dory soon.
Scarfing - The idea here is to join the two 2'x8' panels to make a 2'x16' panel. Use a long work table (mine was 8' long). Dry fit the panels: Clamp one 2'x8' panel down with the good face up, factory edge toward you, with the 2' edge at the middle of the table. Clamp the other panel next to it, butting the 2' ends tight next to eachother with the good side up and factory edge toward you to make a 2'x16' panel. Take two pins and some thread, and check to make sure that the 16' edge is reasonably straight. When you glue the panels together in the next step, it will be important that there is little space between the 2' ends to avoid a weak point, so if the long side is not straight then you may want to flip one of the panels to see if it works better the other way.
Glue-up - Lay a sheet of saran wrap in the middle of the table under where the joint will be. Cut two 4" strips of glass cloth (a little wider is OK) that are just a little longer than the joint (2'), and mark the middle (with 2" on each side) with a pencil at a few points. Wet out the glass strips, panel ends and the parts of the panel to be covered with cloth with epoxy (don't be epoxy stingy with this joint). Lay the glass strip centered on the saran wrap, wet it out some more with epoxy and set one of the 2'x8' panels on it so that it covers half of the tape (which you have marked at the center). Clamp the first panel down. Put the second panel on the tape, butting it up tight against the other panel, and aligning the long edges exactly. Tap the panels to make sure they are butted up tight against each other and are perfectly aligned on the sides. Clamp the second panel down tightly. Make a small amount of epoxy/filler mix (molasses consistency) and fill the area between the two panels with plenty of goo. Wet out the second glass strip liberally and put it on top of the two panels to be joined. I found it important to lay the top glass strip down immediately after pouring the epoxy/filler mix to avoid any air bubbles in the joint (I do have some air bubbles in the joints, there's probably no way to avoid them completely). Lay another sheet of saran wrap on top of the panels and glass cloth, and put something flat and smooth like a scrap piece of plywood on top of the joint, and weight it down (I used two 5 gallon buckets filled with water).
Wait 24 hours or until the epoxy cures completely. Remove the clamps and weights and inspect the scarf joint. Trim off the excess glass tape and sand lightly. Sanding into the weave of the cloth will reduce the strength of the joint and may result in dramatic failure. Paint on some clear epoxy to fill the weave of the cloth, repeat on the other side after curing. Repeat this procedure for the second hull side panel and the hull bottom panel.
Lines - There are four lines or edges to the completed hull side.
The dimensions are written in boatbuilder's notation, so 1-3-4 means 1 foot, 3 inches, 4 eighths (or 15 1/2"). A "+" means add a sixteenth to the dimension.
|Station||Bottom Line||Top Line||Notes|
|0||1-3-4||1-3-4||Sternmost point, top of transom|
|1||-||1-4-0||Bottom line is a straight line to next entry|
|2 plus 4 1/2"||0-0-0||-||Bottom of transom|
|4||0-2-2||1-7-1 +||Top line corrected, 4/27/01|
|7||0-3-7 +||1-10-6 +|
|13||0-1-0 +||1-9-7 +|
|14||-||1-9-2||See next entry for bottom line|
|14 plus 1"||0-0-0||-||Bottom of stem, begin stem curve|
|14 plus 6"||0-3-2||-||Stem curve|
|15||0-7-4 +||1-8-3||Bottom line is part of stem curve|
|15 plus 6"||1-0-6||-||Stem curve|
|16||1-7-2 +||1-7-2 +||Stem curve and top line meet in bow point|
Use a straight edge to draw the transom line, from Station 0 Bottom Line point to Station 2 plus 4 1/2" bottom line point.
Use a batten and clamps to draw the top and bottom line curves. Use a thin batten to draw the stem line curve, from Station 14 plus 1" Bottom Line to Station 16 Bow Point. If some of the points do not fit into a curve well, check your dimensions and if correct, draw the curve fair rather than bending the curve to meet the point. Please report any mistakes in the offset tables to me, Paul VandenBosch.
One word of advice about the curves at the forward bottom corner: if you are going to adjust the curve here, make the hull side panel bigger rather than smaller. Another way to say this is to adjust the curve out rather than in. This point is where the hull bottom and two hull sides come together in front. I have found that curving the bottom of the sides up at this point makes for a weak joint because it bends the hull bottom panel too much. You are better off straightening this part of the line out or even reversing the curve a bit to make the hull side bigger.
Lay the unmarked panel with the good side down. Lay the panel with the lines on top, carefully aligning the edges of the two panels. Clamp them together in a way that you can cut one of the lines with a jigsaw. Cut the line, readjust the clamps and make sure the panels are still aligned correctly, and continue cutting until the hull sides are completed. While the panels are clamped together, you may also drill holes for the wire stitches (see below).
Scarf a 2'x16' panel as described above. You will not need all of this panel, only 2'x12' of it. With the good side up and factory edge facing you, cut off the left 4' of the panel so that what remains of the bottom panel is a four foot section, the scarf, and an eight foot section. (Alternately you could cut a 2'x8' panel in half before you scarf). Using a framing square, mark a centerline exactly one foot from the factory edge, and check to make sure that the centerline splits the panel exactly with one foot on either side, in particular at Stations 5, 6 and 7. With the factory edge facing you and the good side up, mark one foot stations along the factory edge, starting with 0 at the left. If all is well, the scarf should be at station 4 or close to it. Check your centerline; if you run your framing square along the factory edge, the centerline should always show the same distance from the factory edge, and it should be very close to 12".
Take a framing square, and at each station, measure from the centerline (not from the factory edge where the stations are) and mark the offset from the centerline in both directions with a sharp pencil. Keep the framing square square to the factory edge. Note that the aft end of the bottom panel (at Station 0) is 1 1/4" wide, while the forward end comes to a point.
Before you cut out the bottom, add marks on the centerline for the position of the footrest, oarlock, aft seat frame, forward seat frame. Use a heavy marker to mark these positions on the centerline so you don't lose these marks during construction. Label them so you will remember them in a few weeks/months. Note that the footrest is located for a six foot tall person, you may want to adjust it later by getting in the boat and figuring out what is comfortable.
|Item||Bottom Panel Station:|
|Footrest||3 plus 2"|
|Oarlock||4 plus 6"|
|Aft Seat Frame||5 plus 8"|
|Forward Seat Frame||6 plus 10"|
Use a batten to join the points, and cut out the bottom. Do not drill any wire holes in the bottom until assembly.
I used a thin steel baling wire to wire the boat. It is not particularly thick. A slightly thicker wire might not cut into the plywood as much, but the baling wire did fine. The procedure I suggest is based on experience of having to restitch the boat two or three times to get to the point where I could spread the hull and fillet and tape the interior. You don't have to be this precise, but the way I describe it should work the first time.
Drilling holes for wire should be done symmetrically, so there are the same number of holes in the same places on both sides of the bottom. The best way to do this is to predrill the sides while they are clamped on top of eachother. Choose a drill bit that allows your wire to pass through the hole easily but without too much extra space. The wiring holes should be located as close to the edge of the panel as possible without allowing the wire to rip out the plywood. For the middle of the boat, where stresses are low, drilling the holes a little less than 1/4" from the edge of the plywood is acceptable. Near the corners and on the stem curve, stay about 3/8" from the edges.
Clamp the two hull side panels together and make sure they are aligned perfectly. Starting at the stem top, drill the first hole at the corner, 3/8" from both top and side. Drill a second hole 1/2" down from the first as a reinforcement. Drill the next three holes further down the stem, 1" apart. Then move down the stem and drill two holes 3" apart. Starting at the bottom of the stem, drill a similar pattern of holes moving up, making sure that the first is in the very corner of the stem bottom. Complete the middle of the stem by drilling holes about 3"-4" apart, evenly spaced.
At the transom bottom on the hull side, repeat the pattern, moving up the transom about half way. Repeat the stem top pattern at the transom top on the hull side. DRILL THE HULL SIDE, NOT THE TRANSOM.
Starting on the forward corner of the bottom line of the hull side, drill three holes about 1/2" apart. Drill the next three holes about 1" apart. Drill the next three holes about 2" apart, and then continue to the middle of the panel at about 4"-6" apart. Repeat the pattern starting from the aft corner of the bottom line of the hull side.
Just keep in mind through this process: the bottom fits over the hull side edges and the transom edge. The transom fits over the hull side edges.
Start by wiring three or four holes in the middle of the stem curve. Do not wire the corners at this time. These first stitches are preliminary and should be slightly loose. You will likely remove them and replace them with tighter wire stitches later, because the bending involved in getting the hull to the right shape will stretch and weaken the preliminary stitches. Next, align the transom and drill three or four holes on either side of the transom to match the holes in the hull side exactly. The transom bottom should be even with the hull side bottoms, and the transom fits over the ends of the hull sides. It is very important to position the holes so the wires will pull the parts together with the correct alignment. Wire a few preliminary stitches on both sides of the transom and the hull sides. Check the alignment of the stem bottom, and wire the stem bottom corner reasonably tight but not so tight that the wire will be ripped out when the sides are spread to fit the bottom. Repeat with the stem top, and transom tops and bottoms. Check alignment, drill a few holes, wire them up, and move on until the stem curve and transom are wired up completely.
To add the bottom and turn the flexible mess into a boat, turn the hull upside down on a table, and start at the rear corner where the transom, sides and bottom come together. Drill three holes along the width of the transom bottom. Align the hull bottom with the transom bottom, with the hull bottom over the transom edge and drill the mating holes in the correct position. Putting the holes in the right place is very important! Wire them up tight. Spread the sides out a little so they roughly approximate the shape of the bottom, and put the hull bottom on the edge of the side. Starting at an aft corner, drill a couple of holes in the bottom to match the first few holes on the side panel. Do not drill more than a few holes at a time. Wire them up, and move to the other side, repeat. Continue this process a few holes at a time until you reach the stem. Complete wiring any holes that are not yet complete.
Is the bottom longer than the sides? I drew up the plan so that the bottom should be a little longer than the sides. When you get close to wiring the forward end of the bottom, mark the shape of the sides on the bottom, and use a jigsaw or sander to trim the bottom down so the bottom and sides fit together well. This is the area where you will be able to tell if I did a good job writing down the offsets. Please let me know how this fit for you at firstname.lastname@example.org.
Check alignment, are there any problems? If so, feel free to remove any old stitches that are not holding the hull together correctly and to drill new holes and restitch. Go through all of your stitches and inspect the wire carefully. Hit it lightly with a pliers and if it is loose, tighten it up until it sings. Grab it with the pliers and shake it a little and see if it breaks. Don't cut off the ends yet. Check each one. Everything OK? Then its time to spread the hull.
Turn the hull over (avoid getting jabbed by the thousands of sharp points!) and support it by a couple of cinder blocks (or similar) on the floor, with the blocks near the fore and aft ends of the bottom panel. Put a weight in the middle of the hull (5 gallon pail full of water) and watch the hull assume a beautiful shape. Take a piece of wood and a few clamps and find a way to spread out the hull sides a foot or two aft of the middle of the boat. I fastened a clamp on each side of the hull and cut a batten to the right length to stretch the sides by jamming the batten under the clamps. After admiring it for a while, remove the weight and spreader until you are ready to fillet and tape the inside. You should install the spreader when you tape both the interior and exterior chines.
Taping is a job that you have to do in one shot. Running out of epoxy and running to the store for more halfway through is probably going to be a disaster. So have your workshop organized, prepare for every step of the process, have the stirring sticks, the plastic gloves, the goo squeegee, the silica filler powder, the tape, the cleanup products, plastic bag, trash can, rags and and everything that you will need standing out on display. Go through a dry run and imagine goo dripping everywhere, how do you deal with it?
Check each wire again, replacing any that are broken, loose or are of questionable strength, and when you are satisfied with the wiring and the boat seems ready to be glued together, put the hull back on the blocks and weight the center. Put the spreader in and stretch the boat just a bit further than you want it to be when its done (it will relax a little when the spreader is removed). Look at the alignment of the edges, and at the curves of the sheer (top). Hang a plumb bob and look down the centerline. Does it look pretty fair and balanced, no bulges out to one side? If so you are ready to rock and roll.
Take a large flat screwdriver and gently push each and every wire in towards the joint on the inside of the boat. Take a one inch paintbrush and paint clear epoxy on the plywood about 3" on either side of all the joints. Mix up a pot of thick epoxy/filler (peanut butter consistency) and use a squeegee together with a one inch putty knife to push the filler into the joint. Another way to do this is to use a plastic bag and cut a small hole in the corner and squeeze the epoxy/filler out. Use a rounded stick or squeegee to cove (round) the filler, maybe a 2" radius curve in the middle of the bottom, and 1" or less in the stem. Clean up any extra filler laying outside of the coved (rounded) area. A good cove is about one inch wide (more or less), except for the stem which will be narrow due to the sharp angle. Use a lot of filler in the stem. Have you filled all the joints? Have you cleaned up the extra goo? Good, move on to the tape.
Gently lay the dry tape along the joints centered on the joint. There should be at least an inch or more of tape touching the plywood outside of the filler cove. More is better. Try not to gouge into the filler cove too much, be gentle, no need to push it in or anything. Take the paintbrush and paint clear epoxy over the tape, sticking it down. Keep it centered nicely. Are you getting gooey threads that are a pain to deal with? Me too. If you can get them off with the paintbrush, slobber them on to the wastebasket or a piece of cardboard or something. Otherwise just leave them hanging in the air rather than disturb the rest of the tape. You can get them off after the epoxy cures.
You can cut off the ends of the tape that hang over before you start epoxying it, or you can let them hang over the top of the hull a little and cut them after the epoxy cures. Overlapping the tape at the bottom corners is a good thing, it strengthens the hull at a high stress spot. Keep putting tape down until all the joints are covered. Are you thinking that this will never be strong enough to float your bloat? You could add another layer of filler and tape along the stem. This is the joint that I think needs a little strengthening, although I have not had any problems. I used one layer of tape on the inside joints (except where the tape segments overlap).
When you are done, make a final inspection, then stop poking at it, turn off the light, leave the room, shut the door, and don't let anyone near the boat for 24 hours, including you. Don't try to change it while it is curing, you will only make things worse.
After 24 hours or more, remove the spreader, take out the weight, and clean up the glass that is hanging above the hull top, if any. Don't start cleaning up the inside yet, let it cure at least another day first. Turn the hull over, avoiding the many sharp wire points. Use a wire clipper to clip all the wires off of the outside. If you can pull the wires out, go ahead, but if they won't come out, leave them and just clip them off flush. Use a diagonal wire cutter to get them close to the wood. Sand the all of the outside chines (joint corners), stem and transom joints so they are rounded nicely. They should all have nice round corners, not sharp corners. Now put 4" tape and clear epoxy on all the outside corners. You may have areas where the tape won't lay nicely, try shorter pieces of tape in those areas. Once again, let the epoxy cure a day, lightly sand any rough stuff and then paint another layer of clear epoxy over the tape to fill the weave. Let cure. Flip the boat, lightly sand any rough areas on the tape on the inside of the boat, and paint a layer of clear epoxy over it to fill the weave. Let cure. You now have a hull which will need only minor framing to make it ready to row.
You will need to scarf pieces together to make 15'2" pieces. There will be a lot of stress at the scarf area so make sure you are scarfing ends together with no weak knots or cracks. I used an 6" scarf, trying to get 15' out of two 8' sections and one of my scarfs cracked so you might want to go with a 10" or 12" scarf with two scarfs per batten if you are using 8' stock. I wasn't too concerned about the crack, I just smeared epoxy/filler (molassess consistency) in and outside the crack, put a piece of saran wrap around it, and clamped a piece of furring strip next to it as a sister to make sure it cured with the right curve.
What, you don't know how to scarf? Well, you probably should get a book on boatbuilding, but basically it is cutting an angle into the end of a stick, and cutting the same angle into the end of another stick, and gluing the two sticks together. When I talk about a 10" scarf, it means to start the angle 10" from the end of the stick. I drew a line which showed the area I wanted to cut off to make the angle, and then took a hand saw and cut it off. Then I took the orbital sander and smoothed it out and made sure both angles fit each other OK. Then I glued them with epoxy/filler and clamped them down so they made for a straight 15' stick.
Gluing the outside sheer clamps is a matter of wetting the hull top and sheer clamp with epoxy and clamping the two together. Do one side at a time and have at least 10 clamps (more is better). Sometimes the batten doesn't quite want to follow the curve of the plywood and you have to clamp it hard and bend it hard. If you have to fight it, you might want to let the sheer clamp take it's natural shape and either carve off the additional plywood which sticks up after it cures or fill in the hole with more epoxy/filler and plywood after you add the inner sheer clamps. I had to do both on my boat, which means the top curve should be adjusted, but it wasn't by much. The solution is to use battens that are not very thick. I will use 1/2" battens on my next boat.
Cut the sheer clamps off flush with the hull at the ends, or if you like, you can cut it so the forward end is pointed, which is a little bit more difficult cut, but the boat would probably look better with a pointed sheer clamp. When the first outside sheer clamp has been installed and is cured, stand in the front of the boat and imagine the centerline as it passes through the sheer clamp. Cut the sheer clamp along the centerline. Before installing the second sheer clamp, cut the end to fit the first sheer clamp and use lots of epoxy/filler between the two.
If you don't have enough clamps, there is another way. You will have to start by installing the inside sheer spacers (see below) and put them in to be able to use screws to hold the outside sheer clamp in place.
Are the outside sheer clamps cured? Good, let's move on.
The inner sheer clamp is glued to the spacer blocks. The transom is a little difficult because it is rounded. I just glued straight battens across it and then sanded and ground them down to a rounded shape. Not fine cabinetry work but effective.
The ends and transom corners of the inner sheer clamp will have to be cut to join with an angle. I just look at them and imagein the centerline and maybe mark where I want to cut it and at what angle, and then use a handsaw to cut it. This is not accurate and leaves open spaces, so I put plastic tape around the bottom and side of the joint and try to shape the tape how I want the part to look and then fill the joint with epoxy/filler (molasses consistency). You could also epoxy a piece of fiberglass tape under the forward joint (breasthook?) for strength, or pour some epoxy/filler (molasses consistency) under the joint while the boat is upside down.
The arms are 3" wide 1/2" plywood, and are cut to taper from 3" at the top of the seat base down to the width of the inner sheer clamp, where it touches the sheer clamp. The seat base goes inside the arms and holds up the seat. Install the seat base and arms by painting all mating surfaces with clear epoxy, then join the parts and hull with lots of epoxy/filler (peanut butter consistency). Clamp the seat base and arms together, then cove the joints. I did not use glass tape here, but you could. You can also do this in steps to make sure it fits right, for example epoxy the arms and base together while inside the hull, then install the assembly inside the hull. It should work OK either way. I added a cleat on the inside of the seat base to help hold up the seat and keep it from falling in when I tried to open it, but I am not sure that this is needed. I did not add limber holes. The advantage of limber holes is that you have only one puddle in the boat instead of three, but I personally would rather keep the mud and oar splash in the aft area so the front stays clean and I can lay down in it.
I'm sure that there are many ways to make a foot rest. The advantage of this style is that it serves to strengthen the hull.
Email me at:Paul VandenBosch.