I used LPU on my Double Osprey and it came out really nice. I think the problem that you're having might be from trying to do to large an area at once. LPU dries really fast and you can't go back to touch it up or brush it out. Your temp and humidity conditions sound about the same as when I applied it but I only diluted it 20% with distilled water.

I found that doing an area about 1 1/2 foot wide (from keel to sheer) and then doing the next section while the edge from the first area was still wet worked well.

Sounds like you're going to have to do some sanding and do it again (hopefully, you haven't done the crosslink coat yet).

: LPU people - Help!!

: I have two coats of system 3 water based LPU on my Kayak now. I brushed it on
: with a foam brush. I started early this morning with temps in the high 50s
: and 70% humidity. When I finished the last coat it was around 71 degrees
: 50% humidity. I thined it with 25% water. I see a lot of streaks and
: splotches and brush marks and it just does not look good when the light
: hits it right. I would like to know what I am doing wrong and how to fix
: it. I am planning 2 more coats at least. Do I need to wetsand to take out
: the streaks or will they disappear under more coats?