I use the 1/2" PVC-pipe-inserted-into-the-bag method to push the bag
into the wing (end of pipe padded with duct tape; two lengths of pipe
joined with a wood dowel for easy storage in trailer). Never have been
able to pull the current bags all the way out into the wing with just
the string. Years ago, I watched the dealer install a set of double-
layer [loaner] factory bags in my new glider by propping the spar up
on a sawhorse, putting the tip on the ground, and yanking on the
string hard as he shoved handfuls of bag into the wing while I bounced
the wing. Had some left over so he just pushed that in, too. Scary.

I remove the pipe after installing the bag. In the old days (1970s),
not all gliders had strings. The bags mostly worked fine without them.
"Mostly" means that once in a while the bag would get twisted and trap
a lot of water outboard. Bad. I think the strings help to prevent
that. If you've got three strings in the wing, I suspect at least two
of them are connected.

It also depends on what your bags are made of. The original Smiley
bags in the US were relatively lightweight, smooth (yellow) material.
It was easy to slide them out into the wing. The later Smiley bags
were heavy, rubberized (black) fabric. Tough. But heavy. Much more
difficult to slide out. My LS-3 had smooth, lightweight material and
they were easy to pull out into the wing with the string.

Sell the glider and buy one with hard tanks. Oh, but there are
potential problems with those, too. Let's just ban water ballast
altogether. The gliders fly so much better on strong days but it's
a real pain to deal with on the ground. I'm flying the Sports Class
Nats in the US this year so don't have to worry about it.

Chip Bearden
ASW 24 "JB"
USA