Sailing Canoe Chapter 5: Hull Frame Finishing




Introduction: Sailing Canoe Chapter 5: Hull Frame Finishing

About: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of, manufacturers of "3D Printer" output devices. His detailed drawings of traditional Pacific I…

Lashing the stringers to the stems. Locking the lashings with epoxy. Finishing the framework with linseed oil.
Here's what we end up with in this chapter. A mostly finished hull frame with a coat of linseed oil, a lot of finished lashings, and fewer sharp corners.

Continues from
Chapter 1: Make the Deck, Keel, and Cockpits.
Chapter 2: Make Ribs
Chapter 3: Lash the Frame
Chapter 4: Carve outrigger and Break tools

Followed by:
Chapter 6: Morton's Oar
Chapter 7: Sew a Skin over the Hull Skeleton and Seal it.
Chapter 8: Keel and Rub Strips
Chapter 9: Dipaakak
Chapter 10: Independent Suspension
Chapter X: Maiden Voyage

Please support the WAM canoe project as they preserve and foster canoe knowledge in the Marshall Islands.

Step 1: Stem Lashings

Here's how the stringers are lashed to the stem.
I trimmed the end of each stringer to lay against the stem with my pullsaw and knife.
Then I drilled two holes above and below each one. I lashed around each pair of stringers with 7 or 8 turns of polyester twine. I shoved a loop of wire under the lashing and pulled the loose ends through to finish the lashing.

I wasn't planning to do anything at all to the ends of the stringers.
I was going to leave them hanging out in space and not lash down the tips.
It felt like they'd break before they bent enough to reach the stem.
But I tied them bent and went away for a month. When I came back they bent to the stem easily.

So went ahead and lashed them to the stem.
Don't agonize over this part of the boat. You'll see when we stretch the skin over the frame it won't even touch the stringers here. And if it does, this part of the boat is above the waterline most of the time anyway.

Step 2: Epoxy the Stem Lashings

I didn't think these lashings needed to flex much and I don't expect the skin to touch them, so I soaked them with epoxy to make them permanent. I also fully soaked the lashings tying the ribs to the gunwales.

I DID NOT fully soak any other lashings, because I want them to flex and be soft where the skin goes over them.

Step 3: Trim the Spikes Off

Once the epoxied rib ties were hard, I cut the loose ends off with a side cutter. I pushed the cut ends around to make sure they weren't sharp fishhooks waiting to stab me or my gear.

Step 4: Lock the Lashings With Epoxy

I put a dab of epoxy on one side of all the other lashings. Many of these lashings are done daisy-chain style without terminations between. I didn't want the failure of one lashing to spread to others.
I didn't epoxy the outer part of the lashing so it wouldn't be hard under the skin.
I left most of the lashing soft so it could flex. I've seen fully soaked lashings break in wipeouts.

The epoxy stretches less than the fibers. that makes the lashing brittle.
That's a rule of composites. Use fibers that are less elastic than the resin. Otherwise the resin takes all the load and the fibers are mere filler, adding little strength.
These fibers are pre-stressed, which makes it okay, but if you have a stretchier resin to soak your lashings with, use that.

Step 5: Install Remaining Deck Beams

The deck is still a little wiggly, so it's time to install the rest of the deck beams. These are 3/4" square western red cedar (WRC) sticks. They've got two square notches cut in the deck side. Those notches are "scuppers" to let water flow out when the boat is upside down.
Otherwise water will pool under the deck and the boat will rot when it's parked upside down. And breed mosquitoes. And smell funky.

There were some lumps of hard glue under the deck from gluing on the gunwales. I carved them off where the beams would go so they'd lie flat and mate well.
I mixed some of that fast 5:1 epoxy. I painted it on the mating surfaces of beam and deck so it would soak in. Then I mixed white flour with the remaining epoxy til it was flowing slowly.
Some people say "like pancake batter". Some say "like peanut butter". I like mine just between those two. Epoxy soaks into wood very well. If your wood is thirsty the glue will wick away and you'll get a "starved joint". If you over-thicken your glue it gets even thicker once the wood starts drinking the epoxy out of it.

Step 6: Clamping the Beams in Place

I didn't have any big clamps so I wedged sticks under the keel to push the beams against the deck.
When I ran out of long sticks I put boards across under the stringers to wedge sticks against.
The push sticks bulged the deck a bit, which is good. A "crowned deck" sheds water, and the arch makes it much stronger.
To see why, play with a strip of paper. If you form it into a partial tube it's a whole lot more structural than when it's flat.

Every time a glue-up is done, it's tempting to sit and watch it. Or call it a day and come back when the glue is hard for the big emotional payoff of taking the clamps off.
That's one reason boatbuilding takes a lot longer now than in the good old days.

I've heard this a number of times from ear-whiskered curmudgeons who came from the past.
People were a lot more skilled in the old days, because they mostly lived on farms and couldn't avoid working with their hands. Without epoxy tempting them with the mystique of totally encapsulated non-corrosive perfection, they'd just pound some boards together with nails, leaving big enough gaps to shove caulk into and call it a boat. There wasn't any step that called for waiting, except the final paint job.

Step 7: Round Off the Rough Corners

There were some sharp corners where the knees poked into the cockpit. And all over the boat. So I put a 50 grit disk on my $10 disposable angle grinder and sanded off anything that didn't feel good to the hand. I hand sanded a few edges and corners with 80-grit paper.

I learned about illegal invasions on my jackhammer headphones.

I also wore my good "comfo classic" respirator mask and good safety goggles. I was making a dust storm and I didn't want crap in my eyes and lungs. Wood comes from nature, but that doesn't mean you should huff the dust. Especially if you smoke. A healthy old furniture maker told me "every woodworker who smokes gets emphysema".

I didn't have a backing pad or spacers for the grinder, so I just stacked a couple of sanding disks on top of the grit wheel that came with the grinder.
See that edge-on view? Don't ever look at your grinder from that angle. It's like looking down the barrel of a gun. After a wheel breaks and smites you, your heirs will lobby for laws requiring guards on grinders.

Step 8: Epoxy the Deck. Linseed Everything Else.

I painted the remaining bare wood of the deck with epoxy.
Epoxy's impervious virtue has its hazards.
Solara came with some rub rails that had lasted 20 years or so. They'd had no finish on them but oil. We painted them with epoxy. They rotted out from the inside in about six months. The moral of the story: Unless you fully encapsulate your wood with epoxy, a partial impervious finish can be like wrapping it in a plastic bag, and it can rot.

So I painted everything else with linseed oil. It repels water and lets the wood breathe enough.
Linseed oil is amazing stuff. It's what Rembrandt and all those other painters made their paint from. It will last forever.
The stuff you get from the hardware store has heavy metals mixed in to make it set up faster.
It's not intended as food so the law doesn't require them to fully disclose the ingredients.
A friend of mine got poisoned by his dad who thought linseed oil from the hardware store was health food. It actually is the same as flax oil, which is a valid modern health craze.
But the heavy metals made his brain a little odd.

Step 9: El Magnifico!

I put it in the sun for the picture, but then put it back in the shade. Linseed oil needs time to soak into the wood. It reacts with the cellulose of the wood fibers and cross-links to them. That's the exothermic reaction that makes oily rags a fire hazard. I'm told you can put a linseeded cotton rag in a plastic bag in the sun and it'll burst into flames.
If you put a linseeded board in the sun it won't ignite, but the oil will react too fast and turn into gummy "orange peel" gunk on the surface.


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    7 years ago

    Howdy dudes! Wonderful stuff protects it up.Movies


    10 years ago on Introduction

    You should enter this into the photo contest going on. You did a nice job of documenting the process in a pretty easy way to understand.


    10 years ago on Introduction

    I like your boat and your instructions. I live in Alaska and I want to try making a birch bark canoe. I have made some birch bark baskets, but am definitely a novice. Have you come across any resources specifically for making birch bark canoes? Haven't been able to find a whole lot other then a few websites without a lot of specifics. Appreciate any ideas you might have. Advantages to types of wood to use for frame? (preferably harvested from woods spruce, aspen, birch?) Thanks.

    Wade Tarzia
    Wade Tarzia

    14 years ago on Introduction

    Real purty! What are the measurements of the things? LOA, DAS, and the ama length?


    Reply 14 years ago on Introduction

    16 feet overall, main hull is 16" wide, outrigger main beams and outrigger float are both 10 feet long. Outrigger float has 17" circumference amidships. What's a DAS?

    Wade Tarzia
    Wade Tarzia

    Reply 14 years ago on Introduction

    Depth amidships. By the bye, you can see the use to which I put some of the masts I bought off you on last month's photo on Gary D's "outrigger blog." Almost caught the schooner but she turned and headed back for some reason (perhaps out of shame).


    Reply 14 years ago on Introduction

    Ahh. 2 feet deep in the middle. Hey! your boat looks nice! And it's in the water!

    Wade Tarzia
    Wade Tarzia

    Reply 14 years ago on Introduction

    Thanks. Yes, in the water since August. It is not quite finished (no hiking seats) but after two slow years of building I was impatient to sail it. The day the photo was taken (by kindly stranger on the beach) I sailed it 3 miles into the Sound, very rough but exciting, and boat hit 12 mph on GPS, close reach, and I was soaked through -- a wet boat! Side seats will divert the stray when I get around to them. I wish you joy in the warmer Hawai'ian waters! Carry on!


    Reply 14 years ago on Introduction

    On top for sailing, legs down in the cockpit holes for paddling


    Reply 14 years ago on Introduction

    He was done recovering by the time I met him. I mean, he'd done as much recovering as he was going to. I've got to finish it so we can sail it!