Why lend? Why not charter the boats from individuals? Then get the manufacturer or sailmaker to supply sails that could be sold for cost after the regatta(money goes back to the manufacture/sailmaker). The manufacture/sailmaker gets the FREE advertising.
No contribution/ No advertising.
I thought I had read that the budget is 7K for charter boats. That would be $700 per owner.

Now the questions become:
How many people would provide a charter boat without sails for $700?
Could you get 10 charter boats of the same make?
And is there a market for these sails at cost?
Would a manufacture/sailmaker commit?