I made a 2 person bilgy this summer and have been happy with it, mostly because of the low weight.

This weekend was our first encounter with heavy dew however, and it has me concerned. Despite the generous ventilation, condensation formed inside and out, continuing through the night. By morning we had about a cup of water in a pool at the foot of the tent.

Water would condense on the underside of roof, run down to the no-seeum walls, continuing from there to the tent floor and on to the lowest point which fortunately was the foot.

Water in the tent is never a good thing, and with a down bag, it's downright scary. I'm thinking some sort of diverter like piping where the mesh meets the tub that would make the path through the netting the one of least resistance is in order.

Another issue is the slickness of the silnylon tub floor. The instructions recommend painting silicone stripes on the bottom to prevent slipping. We tried that, and later painted stripes on the outside of the bottom too, but if the tent pad slopes at all from side to side, you and your partner will end up packed against the low side.

That silnylon is slick stuff! Sloping from head to foot doesn't present the same problem. I'm not sure why. We've been careful to orient the tent on the pad so it slopes only from head to foot which at least saved us from sleeping in a pool of water.

Edited by herman666 on 09/21/2008 18:41:26 MDT.

To avoid the floor slickness, try Jim Wood's floor treatment at http://jwbasecamp.com/Articles/Silnylon1/index.html

I used his technique on a Henry Shires Tarptent with great results.

> This weekend was our first encounter with heavy dew however, and it has me concerned. Despite the generous ventilation, condensation formed inside and out, continuing through the night. By morning we had about a cup of water in a pool at the foot of the tent.

Would I be right in suspecting that there was a heavy dew outside as well? Sometimes it can be VERY hard to avoid condensation forming, anywhere, inside and outside. Under those conditions about the only thing you can do is to use a double-skin tent and keep the inner tent warmer than the outside world. Even a candle lantern burning all night can help.

Cheers

Don't be afraid of your down bag getting a little wet by condensation. I once did a week long trip through Lappland in northern Sweden. I found a lot of condensation on my homemade Tarptent (plans from H. Shires @ tarptent.com). Although there was dew on my sleeping bag also, especially after brushing against the roof, I never noticed a decrease of loft.
The sleeping bag fabric is ordinary Pertex without a membrane. I never aired my sleeping bag out, it went right back into the Stuff sack after breaking down the camp.

To prevent the pooling and the brushing against the netting walls you might consider moving the walls to the perimeter of the roof (essentially making a "Henry Shires Tarptent" out of it) and using a loose floor that leaves a bit of a gap between the netting walls and itself.
HTH, Christian