I puzzled about this puzzlement as I have an (not unreasonable) fear of building a bent boat. The new building gig takes much of this worry away, and providing you have a level floor, I believe it would get you within 10mm of ‘straight’. Which is amazing for ‘zero’ effort. I distinctly remember the agonising over the ladder-frame gig for my Whilly Boat, and the niggling doubt that it must have a twist in it somewhere.
So the gig is up, bulkheads in and the keelson is poised. The keelson is not the next item to attach, but it plays a great role of locking in the centres. So I fit it to the middle bulkheads and gently draw the keelson down at the ends, watching it slot in one by one. Forward fits like a tube sock, aft displays a single bulkhead shuffle to the starboard by 8mm! A swift kick at stations F and G (appropriately named), and a wiggle back to the port for the transom sees the alignment sorted.
8mm error is pretty impressive, I am sure it could have been left in the boat, but why not kick a fix in?
Now to confirm the level. I reckoned that if I took a straight edge and rested it across the gig adjacent to each station, and put a level on that, I could confirm all is sweet. And this proved easy enough, but it did confirm I have a 6mm lift in the port for-quarter.
To the wedges! Some well placed bits of wood have partially fixed the twist, no matter how much I jammed in under that part of the gig, I could not avoid distorting the bow, so i have left a 4mm twist in the forward part of my Sharpie.
So watch out competitors, I expect to be unpredictable on one or all points of sail!
Well at lease more unpredictable than I already am…