Comments from Phil Leitch:

Mainsail

Perform these steps on a smooth hard clean surface:

  • Remove sail numbers leaving sticky glue behind (recommend to just do part of one number first to make sure this method works on your numbers)
  • Spread Lavender oil over sticky glue and let soak in for a minute or so. You may have to apply twice.
  • Rub with a lot of down pressure just an inch or so at a time. Glue should roll off in clumps. Reapply lavender oil as necessary.
  • Final cleaning with a soapy liquid. We used Dawn Powerwash which worked well for us.

The final result was that we couldn’t find any trace of the old numbers - YAY
This doesn’t appear to harm the sailcloth but I bear no responsibility if it does for you.

Allow yourself lots of time as it takes a while.

Spinnaker

For felt pen numbers we used rubbing alcohol