Straight edge board joints

[Idrisdraig]

I'm plasterboarding a room where 95% of the joints will work fine with taped / tapered joints, but there's a line across the ceiling that has to be the straight edge of tapered boards.
Is there any way to cheat and avoid skimming the whole ceiling?

 

[Wayners]

You can buy 4 sided tapered boards.

If not. There is no tape required joint compound on the market. B&Q sell although I've never tried it. Id seal the dry board edges prior to using though to give it a good change.