A king plank on a deck is just a stringer along the center of the deck that allows two deck planks/planking to join on top or, in the case of the PAXes, join into notches along each side of the king plank.  If a different color of wood is used, the exposed part of the king plank adds a decorative touch.  The radius of the PAX 18's forward deck's curve is much smaller than your Chessie's and a bit more complex to build, but not unreasonably so.  Just take care.

I don't paddle a PAX so can't give you personal experience info.  It is a tippy rocket.  If you don't mind paying attention to staying upright all the time, initially, a PAX will get you straight from point A to point B quickest.

While there are "hundreds" of kits and plans sold, this is a very small number in relation to say the number of Chesapeakes sold. Also, these are not usually (and probably should not be) your first kayak. Point being, most builders have built other kayaks and don't have a lot of questions. They build pretty much the same as Chesapeakes and others, so except for the transom block which takes a little time to fit, they are like building something you have already built. If you put on a one piece deck there is no King plank.

About paddling:Someone else on this site frequently describes them as darts, and that is close. They track very well. Frequently I can paddle mine on just one side and change sides as desired. It goes straight. They need to be leaned to be turned and then it is a slow process. Very wide turns. They are very fast. I have trouble paddling slow enough to stay with other people. If you are paddling with others a chesapeake would be a better boat.

They are very narrow. In my other boats I frequently change position a little every now and then. Move my foot or heal a little. Once I am in one of these, that is the position until I get out. Someone else suggested that you could take a stick of gum with you, but don't bring the pack as there isn't room.

Notice also that the pictures shown on this site, don't show hatches. A few show small day hatches in the back. A lot of people build them without bulkheads to save weight or so you can dry it out if needed. 

In my opion, they are best as very flat water race boats only. 

Hope this helps. 

Thanks, ootbd and Woodie.   I understand a bit more about the 'king plank' now, and it seems as if a one-piece deck may be an option anyway - nice to have!

Having built from plans both a Ches 17LT and Shearwater 17 S&G I have no real concerns with construction.  

I understand from comments above and elsewhere that the PAX is a narrowly-focussed (and narrowly-cockpitted from the sound of things!) racing craft.   I want a lightweight no-hatches-or-other-frills performance craft for fitness paddling only (not organised racing) - but maybe the PAX might be a bit demanding for me.

I'll await any other inputs - thanks again for yours.

Wordsmith

I built the Pax 20, ditched the king planks and glad I did. I used 3mm ply on the decks taking the precaution of giving a light spray of water to the outside of the curve to assist the tight bending. I only used 4oz glass on the outside of the hull but not the deck which I  varnished. Sealed the seams with tape but the rest of the inside was just varnished to seal the wood. Boat came in about 18 kg!  I recommend extending the ends to join like a normal kayak, to avoid the dorky wedge ends. It was disappointing speedwise as it went about he same as my expedition single over a 5km distance. I found it stable enough under my 6' frame once accustomed but It shipped water if you did not  use a skirt as the sides of the cockpit are quite close to the water. I installed a rudder and this was useful on such a long boat. The boat may be good for short speed bursts but I believe the extra wetted area on this length boat is counter productive for any extended fast running.

Thanks, Rev - the 20 is out of the question for me (inadequate room in the garage to both build and store) but I guess your comments are valid for both.

I, too, don't much care for the bow treatment as drawn, although the stern would be OK as I'd plan to fit a SmartTrack rudder and the extra bit of width there would help.

Your construction pointers are helpful, too - much appreciated.   I'm still pondering!

Cheers to all...

Wordsmith