On Monday, 13 March 2017 19:48:27 UTC+11, wrote:
Hello, has anyone here repaired a leak on the ballast tanks of a Jantar Standard 3 glider? I don't mean washing the tanks with paint but accessing the inside of the tanks to repair a leak.

I would like to know how the tanks are constructed. Are they separate tanks installed in the wings or do the spar and wing skins form the tank sides?

They are a double-skin tank fitted inside the leading edge of the wing. The rear wall of the tank is not shared with the spar, standing off it by about 10mm. I'll try to get some photos on the weekend of a trashed Jantar 3 wing that clearly shows the tank structure for you.

I am considering buying a Jantar with leaky ballast tanks and am trying to assess how big a job it is to make them water tight.

Huge I've got 3 Jantars that I maintain currently with stuffed tanks in them and we're trying to work out the best way of determining where the leak is. Best option right now is a party smoke gun and a couple of very small witness holes to push in a borescope and look for leaks. One won't hold any pressure at all, whereas the other two have slow leaks.

I have also attempted, unsuccessfully, to chat with the factory about converting the tanks to bags, as has been done in several other glider types in the past. As usual with the Polish, nobody wants to bother talking with us.