Give away is my user name... I've worked as a canoe and kayak coach for 10 years on upto G3 white water.
Couple of points to consider when looking at Sit on tops:
-The basic sit on tops often have a very low weight limit; 150kg isn't a bad limit.
-They often miss out on some of the nicer features that you get on the better boats
-If they get damaged they sink as they fill up with water; unlike a general purpose closed cockpit kayak they have no inherent buoyancy (my kayak has foam pillars internally, as well as buoyancy bags, whilst my canoe is a 3 core plastic with a foam centre - I can paddle that out fully swapped out of a grade 2 rapid, albeit slowly and not into a nice tight eddy)
-The danger comes from them hitting you on the head, hence the need for a PFD. If fooling around a helmet isn't an unreasonable precaution.
Ed's top tips from years of coaching:
-Flat hulls will spin more than a V-shaped hull... no matter how long the boat is... if you think about it, all you're doing is getting forward motion by pinging the bow of the boat left and right - minimise that swing, and you get forwards motion
-Keep the paddle shaft upright, and the blade close to the boat, and that will stop the spin... alternatively wide (low) paddle strokes will turn you much more
-Pretty much wherever your head is looking you will end up, give or take a bit... sit on the floor, with your knees up and slightly splayed apart and with your heels on the ground, and turn head and shoulders - watch what happens with your knees. That movement will turn you, especially if the boat drops an edge - in time, this can be used to your benefit; it's a bit like how a snowboarder turns.
Length will translate to speed - look at the length of a wave ski compared to a surf ski - its why I like my 15' canoe over my 9ish' kayak for speed - even with a single blade I can be as quick as a whitewater kayak.
Also, PLEASE don't use ratchet straps to secure the kayak to roof rack... a 50mm wide strap with a camlock buckle is enough - I've carried canoes and kayaks around the UK and Europe and we used either rope or camlock straps; the ratchet lets you crank it down so much you crush and distort the hulls. The other thing is to carry them upside down; the roof rack bars will crush the hull, but upside down they're much stronger and the ropes/straps don't exert as much pressure.
And some pictures of what I used to get up to:
Washburn, G2/3, dam release river in the North of England (that drop is high G2, low G3)Another from the Washburn; it sort of shows me looking into the eddy to get the boat there, and using the edge to help the turn:
Ullswater, staff training tripAgain in this one you can see how my body position is turning the boat:
And this is what happens when you over edge:
All done in the name of training - we were practising swimming in white water and self rescue with a canoe - bear in mind one of those can have 500kg of water in it, and weighs 30kg dry...
above 3 pictures taken on the River Spey, G2 (where good whisky comes from...)Picture showing the straps I use (sort of):
Hope some of that helps; if people have any skill based questions, please PM me (I might be slow replying as I don't come on here that often)
By the way, even as skilled and experienced white water paddlers (my preference is for white water over flat water/sea) things go wrong; I didn't go on the trip, but one of the guys who was a member of my club died on a trip - unfortunately his son was one of those who attempted to resuscitate him after the group, Mountain Rescue and fire brigade worked together to rescue him. Think about doing a first aid course for your own sake.