Strip Planking Boat Construction
Definition of Strip Planking, ANCIENT and NEW
Strip building is one of the few ways an amateur boatbuilder can build a smooth rounded hull with compound curves. Plywood is capable of bending in one direction but as soon as you get bends in more than one plane the plywood starts complaining. Tortured plywood has limits before it breaks and often it is necessary to wet it to make it more flexible.
It is also possible to build boats with asymmetrical hulls where both sides are different. That is the cross section of the hull is not equal on both sides. This is sometimes seen in Proas where the main hull is shaped differently on each side. This is how Gary Dierkin builds one of his proas, Gary Dierking's lovely T2 proa is a strip built boat which has different profiles on port and starboard. His book Building Outrigger Sailing Canoes: Modern Construction Methods for Three Fast, Beautiful Boats has plans with sufficient information to build but he also offers fulls plans.
What kind of strips are used?
How are the strips fitted together.
To buy or not to buy that is the question.
Setting up the forms
Nailing vs. hot glue vs. glue and clamps
Starting at the bottom or starting at the top?
Which ever way you decide to plank you will have an area that will need fitting and trimming of strips.
Who's the fairest of them all?
There is no need to go as fine as 220 since the hull will be glassed but it should feel smooth to the hand, and have no flat spots.
Glassing the Hull
Do not use any thickening agent in the hull glassing. Fumed silica (cabosil) is sometimes used to reduce the number of coats required, and save time. It's fine if the hull is to be painted but will show as a veil effect in the sun if the hull is only to be varnished.
I have experimented with many ways of applying resin on cloth and my favourite is using a piece of hard foam as a trowel to gently work the resin into the cloth but not have extra resin on top.
It will take 2 or 3 coats of epoxy to get the weave fully saturated and the coating smooth. At this point you can sand to your heart's content to get a perfectly smooth surface before you varnish.
Once the outside is sanded, the boat is removed from the frame / strongback and turned over. The inside now needs to be smoothed, faired and glassed, then sanded again.
It's a good idea to include some form of flotation on your boat. If you want to build a water tight compartment this is done at this stage. It's also possible to use strap in bladders.
Gunnels Seats and Thwarts
At this point you will need to shape and attach seats, thwarts often with a carrying yoke, if this is a canoe, and any sailing modifications and of course the gunnels.
Varnish (or paint) is necessary to protect the epoxy which degrades in sunlight. Here is a link to my page on varnish.
Use Spar Varnish with UV protection. It comes as traditional or Polyurethane based. The Traditional varnish is often a more golden colour while the polyurethane can be crystal clear, although sometimes it is tinted. The difference in price and quality usually reflects the solid content of the varnish so that a cheaper brand will not build up as quickly and you will need more coats to get good protection.
Polyurethane based spar varnish can be applied over traditional varnishes but traditional varnish cannot be used over polyurethane. It will eventually peel off.
The last step is putting on whatever hardware you have decided to include. This could be an eye at the front for a painter, or rowlocks, or stem bands to protect the bow and stern.
email me : Christine
This information is for general knowledge. I have not personally tested these boats. I can't say if they are safe. If you build a boat be careful. Using tools can be dangerous, get help and advice if you are not certain.