Moin Uli,

I got the boat second hand as well, but I guess the tube was factory made. It is a must have, as you have noticed already.

I have the furling gennaker as well. I really like it, because you can use it at light wind on a close reach. To make it run, the halyard should be tensioned not too light. Unfurling is easy and always works. Furling works best if the sheets are eased and the sail is blown 90 degrees to the side. It must be furled with constant speed and not too fast. If you have a problem let it out again, sail deeper and furl it again even slower, once you got it it is a no brainer.
In this video at about 7:35, you can see how slowly and carefully my wife is furling the sail.
Some pictures:
[img]http://catsailor.com/gallery/displayimage.php?album=lastupby&cat=0&pos=2[/img]

[img]http://catsailor.com/gallery/displayimage.php?album=lastupby&cat=0&pos=1[/img]

[img]http://catsailor.com/gallery/displayimage.php?album=lastupby&cat=0&pos=0[/img]

This is my old setup. It was 1:3 purchase (not 3:1). If you pull one 1cm it pulls 3cm of the furler line. The idea was not to have so much slack line from the drum on tramp or in the water, if the sail is furled. It worked, but took longer to rig, so I went back to the simple system. The red furler line is a dynema rope. I removed the cover on the first 1m so it is thiner and more spare line can be on the drum, so I never end up with furling the sail tighter than last time and lack line on the drum for the last two or three turns. If furled, I just bunch up the line and put it under the front of the foot strap. I like simple solutions. If the line is long enough you can knot its end to rear beam. You can unfurl and furl from the back of the boat, a big advantage in strong winds.

Notice also the white plastic ring in the picture. It holds the furler drum upright. It is a homebuild solution from the last owner. The drum is (if I remember correctly) from Harken. Not sure if this the original one.

Cheers,

Klaus