Thwart-less rowboat possible?

Note: the plans show completely unnecessary thwarts and stringer. I built one of these from the original Popular Mechanics plans over 30 years ago with removable thwarts.
It rowed very well, was built from a/c ply, oak sawn frames, bent over boat nails, butt blocks and butylflex bedding in about 4 days, and is still in use.

 

Our Traditional Newfoundland dorys were built from sawn frames (we called them ribs) but built in much the same manner as the photo by Battan. As such they were stronger to begin with and once the gunnels and interior seat longitudional supports were installed, thwarts(seats) were never considered a structural member. So strong were these dorys that they could be hoisted aboard loaded with fish if necessary.

 

Yes, but can you lift one up and put it in the back of a pickup by yourself? I thought the original SOR was to have a light, easily transported boat. A 200 pound little, traditionally built dory, don't sound like fun to heft into the pickup. A glued lap version would lighten it up considerably and eliminate much of the structural element fitting and fiddling, which may work for this poster.

 

Not likely PAR-- one of these 18 footers weighed in the order of 600 to 700 lbs. by fishing seasons end they soaked up so much water. We'd pull them up in the fall turn them over and cover with tree boughs by spring they were a pleasue to launch and haul up at about 400lb. Our fishing area had no harbours and they had to be launched and hauled up the beach on rollers,many occasions thru very heavy surf. The 18 ft.glass dory i built two yrs. ago comes in at about 250. I could have gotten it down to 150 to 175 but wanted to use it on the open ocean and out there one does not want a light boat- too lively.

 

Yes keep it light, please

Thanks for the link to the plans, BATAAN. The first thing I noticed about this particular little boat is it's almost entirely free of rocker. It also calls out 1/2 plywood sides so it could be a little on the heavy side too. If nothing else, it is a good source for lines and we know a bunch of them have been built and appreciated.

Originally I wanted a boat for myself to row on our sheltered inland lakes that I could throw in the back of my truck and strap in or possible get on the roof of my van, singlehandedly. I also wanted it to row well with a displacement of five to six hundred lbs.
The boat design I show has a cP of 0.62 at a displacement of 0.3 tons. It would probably be a bit tippy with one person on board but it should row well.

It is, for lack of a better word, chunkier than a traditional dory, but with more rocker and a significant dead rise. It would perform well even if it was a bit on the heavy side, construction wise, but would be a bear to get in and out of the water.

 

Russ--500 to 600 lbs. is far too heavy, as per my prev. thread regular grand banks fishing dorys are in this range and other than lifting gear, rollers and winches these are monsters to move. You'll need the strength of the average 4 men. The 18ft.(LOL) fiberglass dory shown is one i built two years ago and I purposely built it on the heavy side(250/300lb.) for ocean work. It's a unique design the fishermen developed in Shelbourne N.S. having a schooner style spoon bow for surf work. They were traditionally wooden built, narrow bottom, curvature in her frames, about 4in. rocker in her bottom, spoon bowed, and more volume aft of mid ship than the traditional dory. This to keep her on her lines with one man rowing in the forward oar locks and 5 lobster traps aboard. As such she rowed like a dream with that spoon bow giving her lift and softer penetration out thru the surf when launched from the beach. Once the traps were set the rowing position was changed to the more mid ships located oar locks and again she was in balance on her waterlines and easily rowed. I built this one as my exercise machine and regularly row some 20 miles a week ( 3 to 4 miles a day) averaging from 3.5 to 4.5 knots depending on tide and wind. I have taken her on several 20 mile trips on the open ocean, up to 5 miles offshore along the coast. I found her an excellent sea boat but in windy conditions i like to weigh her down with about 200 lbs. of rocks. She has more than ample flotation built in her ends and under the seats and after experimenting I found 9ft. to 10 oars are a good match with her beam.--Geo.

P.S. The last photo shows a big 20ft.LOL NFLD. motor dory(make & break engine 3hp. Acadia) that i converted into a motorsailer. Made some great long coastal trips but a little uncomfortable with 2 people --cutty cabin and a cedar bucket

A yacht is not defined by the vessel but by the care and love of her owner--

 

Boat plus my big butt and crew

VikingNorth

Perhaps I was confusing - I meant to say I wanted the boat to row well when displacing five to six hundered pounds. I hoped to keep the boat weight below 100.

 

The plans I linked to make a good little boat with excellent stiffness for the type. The very slight rocker gives good displacement in the ends and keeps her dry in a chop. The original was dragged out of cranberry bog and was quite old when discovered and copied.
Using 3/8" ply in 3 lapped strakes for the sides makes a strong structure and 3 sawn frames, plus a stitch and glue bottom/garboard strake connection would enable the thwarts to be removable.
You could probably get the weight down to 100-125# by carefully picking all materials.
I used this model for several years when anchored out in Sausalito as a tender and it packs well and rows nicely.

 

Got ya Russ I'm a speed reader and as such at times i miss the details--The glass dory could be trimmed down to 200 with careful attention maybe 150 with carbon fiber but that would be the limit. 100lbs. displ. with 500 to 600 cargo and still row easily will most likely warrant a plastic reinforced build both for strength and weight saving in the volume you need otherwise you'll have to be very very vigulant in making the 125 to150lb. mark. As Battan mentions above lapstrake is a good weight saver allowing a reduction in framing--Geo.

A yacht is not defined by the vessel but by the care and love of her owner--

 

Found the original 1968 PM plans. Original possibly from 1890s or earlier, and not a Banks dory, but quite different shape, an along shore work boat that was light and portable, and ended up being used to harvest cranberries. Could be built with epoxy and lapped (3 planks) 5/16" marine ply or 3/8" lesser quality. Same with bottom, S&G garboard to bottom, use epoxy and fillets, one thwart aft and one forward and a removable something in the middle, like a box or chest to row on.
As I said, this model was built in 1969 from the magazine plans to a very low standard by me and is still in daily use by its current owner as an exercise trainer he can beat up.

 

Thanks BATAAN

Thanks for the original plans.

I downloaded these and I am strongly considering this boat. As an excersise, I may redraw it in rhino. I find that sometimes this helps during pre-construction, sort of building it out of electrons before building it out of wood. If I do this, I will Upload an STL file here as well.

Russ

 

Russ, that would be very nice. Rhino is great to have but expensive. The special effects industry uses it a lot to design miniatures and full size sets and make cutting plans for the laser cutter to generate precise parts.

 

For a boat of this size, a 3/8" bottom and 1/4" strakes will be just fine, as a glued lap build. This is less then 60 square feet of hull material and if using Okoume, the planking will weigh about 50 pounds when glued in place (about 57 if meranti). Toss in a couple of end boxes, some lap stringers, as 1/4" doesn't fair well without a stringer backing up the lap, some type of sheer treatment and you're about 100 pound, before the thwarts get tossed in.

 

Battan--nice little craft--might be tempted to have a go at that myself, once i get the big one wetted--

 

I'd prefer to make a temp mold with stringers, plank it fair, then install frames. This makes it a bit lighter.