Wearing a down jacket under a dry suit?

I have not used a drysuit fir ackrafting but have used one for snorkeling & a little canyoneering  .

My gut feel is that it would not be a good idea.  In the water, hydrostatic pressure will compress the down and you lose insulation.  Additionally, DrySuits do not breath so your gear underneath tends to get moist.  The more active you are the more moisture builds up.   Even wearing fleece, you end up being warm, but moist.  You don’t really notice it until you remove the drysuit  My 2 cents.

Dry suit + down jacket seems like a bad idea to me. I’ve drained sweat pooled around ankles on rafting trips – it’s like wearing a giant Ziploc bag – GoreTex dry-suits included. You could be working as hard paddling a boat as you do hiking, down will make sweating worse. Dry suits can develop leaks, especially around the fragile seals. A PFD will compress a down jacket, if you are wearing the PFD tight enough. Getting in and out of a dry suit is hard enough without adding a bulky down jacket. You want layer flexibility when the day turns from cold, windy, and rainy to warm-ish and sunny.

I’d stick with layers of fleece and polypro.

— Rex

There’s an Inuit concept of “never sweat” when you’re out in the elements – meaning you regulate your clothing and exertion to never get so warm that you generate liquid sweat.  The more I do that – and I’ve been working on it for 20 years – the better things go.  My clothes aren’t so wet when I stop, I don’t need to drink as much water, and I find I have more endurance if I take things just a bit slower.

I’m not perfect at it – I’m still learning.  I haven’t been doing it my whole life nor am I from a culture that has done it for a hundred generations.

But I’d suggest you develop that skill if you aspire to hike with down under a rain shell.

Down under a dry suit while pack rafting introduces additional problems. Even if you don’t produce liquid sweat, your skin still generates water vapor due its heat and moisture content.  The drysuit will be cold if the day is cold or it’s in river water.  Then the water vapor will condense.

If you don’t any of this, some night when you’ll watching 3 hours of Netflix, put a large plastic trash bag around your legs and tape it closed at your waist.  You’ll find it moist inside after a few hours of NO exertion.

Ok good to know guys! Sounds like there would be a significant enough amount of sweat accumulation to worry about. In the conditions were I would be wearing that much insulation (cold, rainy or snowing) it would be probably be hard to dry a down jacket out.

I’ve done it.  Less than ideal due to the inevitable moisture accumulation but if it’s that cold drastic measures are necessary.  Not catastrophic under those conditions, especially if you’re talking about less strenuous paddling.

Fleece is ideal for under a dry suit for obvious reasons.  You’ll probably be surprised and just how much extra warmth being inside a sealed WPB system will add, lots of folks overlayer the first few times out.

“You’ll probably be surprised and just how much extra warmth being inside a sealed WPB system will add”

I agree with this but will note an exception.  If you’re immersed in cold water (during a rescue? unable to immediately re-board the raft, in waist-deep water while fishing in chest waders, etc), then that 1 psi of water pressure does compress your insulating layer a lot.  It would compress down the most, but any puffy will suffer versus pile or fleece which in turn are out-performed by neoprene wetsuit material.

And, yes, it is about 1 psi.  2.31 feet of water column is exactly one pound per square inch, so that’s the water pressure on your lower leg if you’re belly-deep in water.  Twice that, 2 psi, if your legs dangle down with only your head out of the water.

1 psi is also the pressure of a stack of nineteen 500-sheet reams of computer paper (5 pounds each x 19 = 95 pounds spread over 8.5 x 11 = 94 square inches).  That’s a stack of computer paper (or books), 38 inches high.  Stack a meter of books on your down jacket, any puffy, or even your fleece, and see how much dead air space gets squished out.  Almost all of it.

Yes, when I first went winter camping in 1973 our trip leader advised us to always be comfortable cool, no matter what the conditions.  I have been following his advice ever since then, in any condition where it is possible.  Actually even on hot days I’ve been known to soak a cotton t-shirt in water and wear it all day, re-soaking as needed (easy to do in the PNW, where I used to live).  This is one of the times that cotton works well.