for a small servicable boat.
This is about building a pair of oars.
But first, I'd like to extend my compliments to Tony Hunter and Don Elliott for designing and drawing such a practical little dinghy as the Twig. For those of you who aren't familiar with the Twig, it's a one-sheet dink, 4' long on the bottom, and (up to) 3' wide. I say "up to" because I diverged somewhat from the plans by making ours 3' wide... because I didn't have the plans at the time of laying it out and did it from memory. But that's another story altogether. See: "The Accidental Rowboat"
For the Twig Brian and I built, we needed oars no more than five feet long because Brian wants to be able to lay them inside the dink. This particular dinklet is for Brian for helping me these last several months.
I've been puzzling over the "oars" question for about a week. The boat's almost finished and it is, after all, a rowboat. You've probably heard of people who design in their sleep. Well, I'm one of those people. I'll go to sleep with a problem and wake up and know how I want to build something.
But first every design needs a drawing. I was explaining to brian how we were going to build these oars.
So here's the drawing.
As you can see, the blades are 5½" wide and 20" long. The section details on the side show the loom and the blade as they mate with each other.
I went to Home Depot and picked up 2 brand new replacement shovel handles 48" long, Made in USA, 6 dollars each. (There are longer handles available for longer oars. They also cost more.)
After cutting the two blades from ½" plywood, I laid out centers and perpendicular lines across them at 8", the depth they were going to sleeve onto the looms. Then I found a suitable radius piece to trace the upper curve. I was looking around for a trashcan lid but couldn't find one. This oil drain pan was the biggest round thing around the yard. By a happy coincidence it's not round. Part of the curve forms a parabola which will give the baldes a nice [somewhat] graceful curve.
I traced this curve ONCE, then after cutting and sanding it slightly, I used it to reproduce the similar curves needed on the other blade. Tuna cans, coffee cans, and for this case, a yogurt cup, are all repeatable radii. I never remeasure or redraw a radius unless absolutely necessary.
Once the second blade was cut, I used it to finish the first one.
Next. I screwed the blades together through the sleeve area. It'll be cut out later so it doesn't matter about the screw holes.
The screwgun makes a handy hammer for breaking off the screws.
If they don't break off cleanly, you'll have to grind them down so you can flip the blades over for sanding.
There shouldn't be much to it. A couple of passes with a beltsander just even up all the curved edges. That's it for the blades for the time being.
Shovel handles are normally thicker at the bottom and slimmer at the top. I wanted the reverse, the thick part up where your hands would hold the oars to offset the weight of the blades at the slim end.
But the slim end flares a bit, so I turned them down so they were cylindrical using the Kensington Lathe.
For the grips... We decided on 5½"
Proper use of the Kensington Lathe requires the use of the entire arm, from the palm to the elbow. A loose grip with the opposite hand and a smooth rolling motion with the arm.
After a few twirls of sandpaper we both decided we liked the feel, fit and look of the grips.
Back again to the looms. The rabbetts were cut with the tablesaw.
I set the blade height for a ½", and with the fence on one side, I cut all four "first cuts". Then I moved the fence to the other side of the saw blade and turned the looms 90° and made the "second cuts".
Take note of the plywood "stop" clamped to the end of the table. Coincidentally, this stops the looms at 8½", giving me a full depth cut at 8". The inset shows the resulting rabbetts.
The rabbetts were finished up with a short chop of the chisel at 45° and a couple of swipes to clean out the very end of the cut.
Now the blades need to be slotted. The width of the slot is determined by the width (or depths) of the rabbetts and the thickness of the plywood. Now, you can do your geometry and determine the depths of the rabbetts correctly the first time, or, you can go hell for leather and cut what looks "right". I'm sure you can guess what I did.
"X" is the width to mark on each side of the blades, (for ½" plywood.)
Test fit the blades to the looms. If they've been marked and cut properly, they should just slide on. If not, sand the bevels, a LITTLE BIT on each face.
There's a slight bevel cut into the opening of the slot. That's to accomodate the bevel at the ends of the rabbetts.
The tips of the looms are slotted also. A ½" wide and a ½" deep so that the tip slides on past the end of the slot in the blade.
Scribe a line ¾" from the edges of the blades on both sides. Taper these lines to "0" as they get to the tip of the blade. Sand on a beltsander. Finish with hand paper.
The rabbetts and beveled blade slots were wetout with straight epoxy. This was allowed to soak into the woods, then Cabosil was added to the rest of the batch of epoxy until it reached a thick peanut butter consistency.
The gaps were treated like fillets.
A couple more coats of epoxy and...
Brian tests the new oars.
"The Chief Instigator"
Naturally as with any project there are a few "wrap-up" details. The oars need a couple of coats of polyurethane for UV protection.
But, that's it. They're oars.
Click on this little shack anytime you want to go "Home".
Copywrite © Alan "Maddog!" MacBride 2001
Most recent Revision 06/24/01