Building L Francis Herreshoff's Pram
The building of this pram was inspired by the lines and table of offsets in John Gardner's book, "Building Classic Small Craft". These lines and offsets were taken from a half model that John Gardner fashioned after a pram of L. Francis Herreshoff many years ago before including them in his book. This pram is easy to plank due to there being no hard bends or twists in the planking. While it is a simple boat to build, the inexperienced builder should not underestimate the skill level required according to Mr. Gardner. My knowledge of boatbuilding comes from having a father that was a shipwright in the early years of his working life. I also am a graduate of the Northwest School of Wooden Boatbuilding as stated in my profile https://www.nwswb.edu.
My previous three posts are about the lofting process. The tools needed are few and the process takes 4-6 hours with some basic knowledge of lofting. Once the lofting is complete it is time to take up the lines and begin making molds for determining the shape of the boat. I prefer using clear acetate, tracing the lines onto the acetate, then transferring the lines to the mold stock by positioning the acetate on the mold stock and poking an awl through the acetate into the mold stock, then drawing the cut line. Another popular method, and more traditional I believe, is to lay nails such as roofing nails on their side, heads lightly pressed into the floor along the lines and pressing the mold stock onto the nails to mark the line on the back of the mold stock.
The 4 lines in the photo are of the aft molds (1-3) and the aft transom in the plan view of the lofting. Another sheet of acetate can be used for the forward stations and with 2 sheets, you have recorded all the lines. I often use blank sections of the acetate to trace the knees and other lofted components.
I used 1x pine for the molds and sawed the required bevels into the molds when sawing out the pieces. Fortunately, my band saw is equipped to saw rolling bevels from -10 deg to +45 deg. Some will just use the cut line as the point of contact with the planking but there is more support and less force on the mold when the bevels are cut into the mold before beginning the planking. Where a gusset was required, I used 1/4" plywood to join the mold sections glued with carpenter's glue and light screws.
Here (left) is the mold for the #3 station just aft of amidships. The construction is basic. The bottom of the mold in this case runs the width of the station and the vertical pieces are joined along a diagonal from the lofting. The gussets are positioned inside of the station line so they don't interfere with the planking. When the molds are constructed, it is important to mark ALL information from the lofting that you may need later onto the molds, (eg., Sheer line, Waterlines, Center line, Diagonals). The cross spall is fastened so that the top edge is at a waterline above the sheer on all the molds and when the mold is inverted onto the building jig, the shape of the boat is complete.
To the right you see the molds are complete and attached to a "ladder" building jig with both the aft transom (not visible) and the forward transom in place. The keel has been placed into to notches in the molds and now it is time to line out the planking. Planks generally run somewhat straight, have little twist, and with the 1/4" thickness, there is little need to steam any of the planks.
Lining Out, or determining where each plank will go is accomplished by milling thin (1/4") battens the width of the lap (over lap of one plank onto another or 3/4") and are placed over the molds in fair lines over the length of the hull. Once these lines are established, the widths of each plank are recorded on the molds and transferred to the opposite side of the hull.
Planking starts with the Garboard (the plank along the keel) and proceeds down (up with the boat right side up) to the sheer. Each succeeding plank overlaps the previous and the lap is marked and beveled so that the two planks join tight against each other. Each plank is riveted every two inches between frames and riveted through each frame when they are installed later.
The planking material used for this pram is Atlantic White Cedar (Chamaecyparis thyoides) which is sometimes confused with Northern White Cedar. These planks at 1/4" in thickness can be milled in pairs from 1" rough boards and installed as a right and left, saving time. Since the length of this boat is 10', I tried to use full length planks. Where this was not possible I used a feather edge scarf to join the two pieces to make one strake. In this photo above only two planks remain to be installed and then the boat will be removed from the molds, turned over and the plank laps riveted.
In the photo left, the pram has been removed from the molds and is ready to rivet. If you look closely, the rivets appear to be in pairs with a space between each pair. That space is a frame bay, and each steam bent frame (rib) will be installed in that position with a rivet through the planking and the frame.
Below the frames have been installed and a lot of riveting remains to be completed.
Here is the boat complete and ready for some varnish. Once complete, the seats will be installed and the bumper line attached to the gunnels.
Here is a detail shot of the thwart knees which I chose to make from steam bent Black Locust which I had available. Black Locust is incredibly strong and works well in a nicely finished tender like this pram.
This is a 7/8ths in. polyester 3 strand line laid into a concave channel cut into the gunnel. The gunnel (outwhale) is riveted through the planking and inwhale.
Here is a view of the Herreshoff Pram complete, with oarlock blocks, oarlock sockets, bumper line, and floorboards installed.
At this point it might be a good idea to review the various materials used in the construction of this pram.
1. The batten keel is of white oak as are the knees joining the transoms fore and aft.
2. The transoms are of Mahogany as are the cheek pieces installed on each transom.
3. The seat risers are of Sepele (mahogany) as are the inner and outer components of the gunnel.
4.The steam bent frames are of white oak.
5. The floor boards are Atlantic Cedar.
6. The seats are of White Ash milled from suburban trees removed due to the ash borer, the thwart knees are steam bent Black Locust as are the oarlock blocks.
7. The pram is fastened with Silcone Bronze carriage bolts where called for, Silicone Bronze screws, and copper rivets for fastening the plank laps and through fastening the plank laps and frames.
8. The bright finish is of Epifanes clear varnish.
9. Oars are Spruce, 6' in length, varnished and leathered.
We wouldn't be complete if we didn't mention propulsion. The oars I made for this pram are 6' in length and of clear Spruce. The oars are completed with hand sewn leathers and buttons with bronze oar locks.
This post is about my experience building the Herreshoff Pram. Prior to this project I built two 111/2 ft. Herreshoff Tenders one with sails and one for oars only. If you are considering building your first boat take some to read the many books out there on the subject and/or enroll in a boatbuilding workshop in your region of the country.
Here are some references for publications that may be useful or that I have mentioned in this blog:
The Northwest School of Wooden Boatbuilding
"Building Classic Small Craft", by John Gardner
International Marine Publishing Company
Library of Congress: 76-8778
ISBN: 0-87742-065-3
"Lofting", by Allan H. Vaitses
International Marine Publishing Company
Library of Congress: 78-75110
ISBN: 0-87742-113-7
"Clinker Boatbuilding", by John Leather
Adlard Coles, Ltd.
ISBN: 0-229-11504-7
"Boatbuilding Manual", Robert M Steward
International Marine Publishing Company
Library of Congress: 77-133677
ISBN: 0-87742-014-9
Please comment and let me know if you have any questions about building the Herreshoff Pram.
Bob
The 4 lines in the photo are of the aft molds (1-3) and the aft transom in the plan view of the lofting. Another sheet of acetate can be used for the forward stations and with 2 sheets, you have recorded all the lines. I often use blank sections of the acetate to trace the knees and other lofted components.
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