Dinghy cruising: sail setting on a sprit boomed standing lug yawl

Someone was asking John on the JW builders forum to help them with a sail crease problem they were having on their navigator. I occasionally got that problem on Arwen but through John's help discovered that tying the halyard on the top spar further aft and putting plenty of tack downhaul tension on - the crease disappeared. Joel helped me work out that the angle of my sprit boom needed to be more acute and that the snotter attachment point needed to be higher up the mast. Attaching parrel beads to the sail tack and hauling it as tight as I could against the mast also helped.

So imagine how stupid I felt when I discovered John passing on this advice to said forum member

• "Outhaul tension on the yard is important, there should be enough tension on there to put a crease in the sail that does not come out until the tack downhaul is on, and the sprit outhaul is on"     what outhaul I hear myself ask - I don't have an outhaul on the sprit boom - the clew is directly attached to aft end of boom (hope I got my terminology right there).

• "The tack downhaul and halyard in combination put tension on the sail from tack to peak. With the sprit outhaul off, there should be a crease from tack to peak".  Does he mean the snotter - when he refers to the sprit outhaul - is it the same thing? Should I be tightening up tack downhaul and halyards first before then tensioning the sprit boom snotter?

• "When pulling the sprit outhaul on, it should have enough tension on to just pull the crease out, too much tension will form a crease from throat to clew".  ooooh!!  That would explain why a crease appears in the opposite direction.....ah enlightenment hits me six years later.............I am sooooo dim!

• "One of the things that can affect the set on these is having a yard that is not stiff enough. If its flexing more than it should it wont be possible to get the crease from throat to clew out. (forward top to after bottom corners, the one that is often the problem). Ideally there should be about 70 or 80mm of flex in the yard in 15 knots of wind, you'd just be able to see that from the helm position when sailing to windward.  Any more and you lose control of the shape, any less and the sail wont twist off to reduce the heeling effect in a gust".    FLEX? IN MY SPRIT BOOM? 7CMS? SERIOUSLY??  No one mentioned that to me. My boom is virtually inflexible - I know - its hit me on my head several times! Shape and twist in the sail?  steady on...........I'm still getting over the shock of discovering a boom outhaul that I may or may not have!!  Aargh!

John is an amazing guy who gives so much great advice but before I ask him some really dumb questions....does anyone know anything about the above which they can explain to me in one syllable words?

I feel a trauma coming on....................I need a cuppa!