, I can’t “practically” dye sailcloth; and I doubt most of us could.
Polyester/Dacron (sailcloth) requires the use of disperse dyes*, as opposed to acid dyes (for wool or nylon) and fibre reactive dyes (for cotton and rayon).
The difficulty with polyester dyeing is that it requires a lot of heat to get the dye into the fiber. Boiling water
is not hot enough to do the job by itself, so a noxious-smelling carrier chemical must be added, for immersion dyeing. Polyester dye actually transfers to the fibres best at very high temperatures.
* Instructions for Immersion Dyeing Polyester using PROsperse Disperse Dyes:
C:\Website\Immersion Dyeing Polyester.htm