Old Boat, Reverse Sheer

I know what you're thinking. That boat was warped on account of that concrete pillar coming out of the cockpit. But not so. The concrete pillar coming out of the cockpit is an accident of framing.  I could tell when I was taking the picture that maybe my framing was not that good, but I was not in the mood to reposition the boat just for a picture.
Anyway, what I am trying to show here, and it may be more obvious if you click on the photo to see a larger version of it, is that the sheer line has gone into reverse, that is, the sheer is higher in the middle than at the ends. And the bottom of the boat has flattened out to the point of almost no rocker. 
The sheer line for the non-nautical is the line made by the tops of the gunwales, that is, the two boards that form the edge of the deck.
This was not a boat I built, but I am sure that when it was built, it had more sheer and rocker and that the downward movement of the bow and stern with respect to the middle of the boat was the result of the nylon skin tightening up over time. 
The other thing I noticed when I build boats is that since both the keelson and the stringers are bent into place over the ribs, they exert a downward force on the ends of the kayak that combined with the force of a shrinking skin will tend to make the keel line of a skin on frame boat more straight over time.
I am theorizing here, but the Unangan (Aleut) builders always built their keelsons in two or three parts and the parts were carved into a curved shape, not bent into place to avoid this kind of downward pressure on the ends of the boat. 

Old Kayak, Bent Ribs

I've got one more set of photos on deck for the old kayak series.  Not that I don't have more old kayaks or old kayak photos, but it's a matter of being able to find them.

Today's tale of woe is all about the lethal combination of heavy nylon fabric and a boat left out in the sun for too long.  Nylon, if you don't already know, contracts with high temps and as you can see in the photos, pushes down on the keelson and bends the ribs into a reverse curve.  This isn't that bad, mostly it makes the hull a little flatter.  What is worse is the end to end shrinkage of the fabric which compresses the keelson which responds by taking on something of an S curve when viewed from above.  This makes the boat pull to one side.  But even that is not lethal and I managed to fix it with a rudder.  It's just that the boat is not the elegant craft that you started out with. So beware of heavy nylon combined with heavy sun.

This Old Kayak, Old Paint, Part 1

People occasionally write me to ask whether they can use this or that material or process in the building of their boat.  I sometimes have answers for them and more often do not.  When I don't, I like to tell them to try whatever it is they are asking about and they will find out if it works or not and then they will be the experts on that particular topic.
In any case, I try a lot of stuff, more or less indifferent that a lot of it won't work.  I also am casual about boat storage so most of my boats are subject to accelerated aging. I also like to use off the shelf, not yacht approved materials to see whether there is a cheap way out of any particular conundrum.
So let's move on to today's topic, Old Paint. No not the horse.  Old paint that has turned dry and brittle and stressed and developed cracks.  To be more specific, old varnish.  Because the substrate of the varnish on a skin on frame boat is a flexible fabric, impact on the skin causes fractures in an interesting way. So proceed and feast your eyes on a variety of stress cracks in old varnish on a nylon skin.  Enjoy.

A small running critter.  The green flecks are fake gold leaf I put in the varnish.  The gold is actually brass and has oxidized to a green.

stretch marks.

Southwestern US petroglyph, what of, I'm not sure.

and a braid.

More stretch marks.

This one kind of looks like an ancient shrimp fossil.

This one, I'm not sure, kind of like a cartoon bird in flight.