Gunwale to Deckbeam Joinery
Gunwale to Deckbeam Joinery
There are a number of different ways to joint gunwales to deckbeams. We will demo four of them.- mortise and tenon
- doweled butt joint
- East Greenland joint
- stone tool joint
Mortise and Tenon
To make this joint, we cut a tenon on the end of the deckbeam and carve a mortise or square hole the size of the tenon in the gunwale. Then we assemble the two. The shoulders of the tenon are cut at an angle to match the angle of the mortise. This is the angle that the deck beam will make with the gunwale.While this joint takes a fair amount of marking and cutting and careful fitting, the payoff for all this effort is that this joint very firmly aligns the deckbeams and gunwales at the angle that you have cut your mortise and tenon. Assembly simply becomes a matter of sliding the pieces together.
We drill the mortise into the gunwale at an angle that matches the angle at which we cut the shoulders of the tenon. Then we clean up the mortise with a chisel.
After some final adjustments to make the tenon fit the mortise and vice versa, we slide the tenon into the mortise.
Doweled Butt Joint
This joint is simpler to make than mortise and tenon but requires greater care in assembly. The thing to watch out for in this method of construction is that the gunwales are properly aligned before the deck beams are doweled to the gunwlaes. Otherwise any misalignment or twisting of the gunwales becomes permanently fixed in place.
In this joint, the deckbeam is cut off at the angle at which it will meet the gunwale. It is then temporarily nailed in place to allow the drilling of doweling holes which go through the gunwales and into the ends of the deck beam. Dowels are then hammered into the holes and the joint is lashed to prevent it from pulling apart.
East Greenland Joint
This joint is similar to the doweled butt joint except that a notch is cut into the gunwales. The end of the deck beam which is cut to a more acute angle than the notch sits in the notch. The joint is then doweled and lashed. Unlike the butt joint in which the dowels go into the end of the deck beam, in this joint, the dowels go into the top of the deck beam, come out the bottom and go into the gunwales at an angle. This joint is also lashed to keep it from coming apart.
This is the notch cut into the gunwale in which the end of the deck beam will be seated.
The deck beam is set into the notch in the gunwale. The angle of the gunwales is fixed by the dowels through the tops of the deckbeams and the joint is held together by the gunwale to deckbeam lashings.
Stone Age Joinery
Before steel tools became available to kayak builders, they had to carve all of the frame components with stone tools. Making mortise and tenon joints was out of the question. Drilling deep holes with stone tools was likewise difficult. This made doweled construction difficult.
The solution that builders used was to carve shallow depressions into the gunwales and then set the deckbeams into the shallow depressions and lash them in place with lots of lashings. The lashings ran from gunwale to gunwale to pull them together to keep the deck beam from popping out of place. In addition, the lashings ran around the deck beam to keep it from sliding upwards and out of its seat in the gunwales.