Maybe it's a midlife crisis, but temptation got the better of me and I picked up a second hand Blokart with a 4m sail, I already have too many boats and surfboards, but haven't owned a landyacht (except for using a tarp and garden stake on my skateboard as a youth). Looking forward to taking it for a spin, but out of curiosity I'm interested if anyone has seen polar (diagrams) for Blokarts?

Not sure a polar could be produced for a land yacht,as I understand it each Water Yacht has a polar produced by the builder based on displacement, hull shape etc. A land Yacht has too many variables ,The pilot weight has probably the greatest effect so the builder could never accurately determine the speeds possible.( the pilot is usually much heavier than the yacht) It's muted that a land yacht will top out at 2.1/2 times the wind speed but sail sizes,surface conditions,clean wind, gusty off shore winds, type of yacht plays a major part.Ie a class 5 will usually beat a mini, A well sorted Y framed mini will usually beat a blokart .Mainly because of the basic designs, the blokart uses small wheels which limits top speed the 5s have considerably larger wheels,the 5.6 minis has 8ins wheels which are slightly larger than the blokart.etc.
I am constantly experimenting, with a GPS ,different tyre pressures ,sheeting systems ,body position ,mast stiffness , wheel camber, wheel toe or out in. After 10 years still haven't settled on the optimum settings. Best 47mph in 20mph wind with 3m sail. Once above 20mph control becomes an issue once onto two wheels you slow down or capsize . All good fun.
As an aside this forum is rarely used used these days dont know if there is a mod looking after it,would think this topic is better on general if there is one.you may get more info from more knowledgeable sailors there.
If you want to read up on all of the topics enter seabreeze construction page 2 it will bring up hundreds of topics and discussion going back years Keep you entertained for months
Good luck and fair winds Bf 4 or5 please.