Printing on nothing..

Hi all. There are a lot of interesting parts on thingiverse that have areas where a layer is printed onto nothing. That is, there is no support material beneath it. How is this done? I am assuming the material is just stretched across the empty gap? What kind of settings in skeinforge do I need to change in order for my parts to support this? Do I need to lower the flow rate and increase the feed rate of the x/y?
Thanks

The flow/feed rate should be such that the filament is stretched across the gap but doesn't snap. See this:

[www.thingiverse.com]

Should I be adjusting the flow/feed rate globally? I notice there is a setting under speed for Bridge feed rate and bridge flow rate multipliers, however those seem to not have any effects when I tried them out.

With Bridge feed = 2.0 and Bridge flow = 1.0 I was able to print out a working whistle v2.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

I assume that is an ABS whistle. PLA is much more tricky. You really need to get it right to prevent sag without snapping the filament.

No, PLA is all I am using at the moment.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse