At 5:15 AM +0000 1/30/09, John Hartog wrote:
>To those participating in the DIY raincover discussions - just a
>couple points of progress.
>
>I bought the "Sea to Summit" stuff sack I had previously pointed out,
>and although it does seem nicely thin and acoustically transparent, it
>is crinkly sounding when crushed and may be too loud unless somehow
>stabilized.
>
>Using other nylon materials I found some problems. The umbrella type
>materials that have a water repellent finish but are not coated with a
>waterproof layer seem to lose their water repelling effect if not
>pulled taught like on an umbrella or if bonded to any material that
>obstructs droplets from immediately beading and rolling off. In tests
>with a couple different fabrics under a dripping faucet, the water
>began streaming through after only several seconds.
>
>I made one actual rain test using a dome made from the nylon mesh
>floor buffing pad material and under layer of thin, coated waterproof
>nylon, but the results were not as promising as I had hoped. Neither
>water nor wind got through, but the rain drops were still clearly
>audible - not much of improvement over just letting my usual fleece or
>fur wind screening get wet in the rain. Similar to wind screening, the
>proximity of the protective layer to the mic capsules makes all the
>difference, and my rain cover at 2 to 5 inches away was not far
>enough. At this point I think a larger rain barrier suspended at
>least a couple feet above the mics would be a much better solution.
>
>Another issue is that although the coated nylon or the nylon mesh,
>either one alone, seemed fairly quiet to the touch, when bonded
>together (I used a spray adhesive) the interface became very noisy to
>the slightest touch or movement.
>
>Ripstop nylon is not a quiet material, as I'm sure many other nature
>recordists have discovered trying to record too close to an occupied
>tent and sleeping bag.
>
>~John Hartog
>
Hi John--
Thanks for getting back with your extensive studies! Wind is
definitely the culprit and any material used has to be very taught.
That's probably why new, cheap umbrellas do a pretty good job of the
water-shedding part. I've been suspending large ones with bungy cords
to branches that move with the wind. They usually only flap during
gusts. The large-size (golf?) umbrellas can be positioned a couple of
feet above the capsules unless its rainy and windy. I've covered the
large umbrellas with hogshair which is a significant improvement, but
not "silent."
Maybe we should expand the concept of a sound transparent, more
"rigid" (less flappable) shield? Are any of the water resistant
materials you are testing "stretchy?" If so, this "fabric" could be
stretched taut across a frame and covered with the diffusion
material. This plane could then be sloped and suspended several feet
above the rig with bungy cords. A much more workable solution if the
location has surrounding tree branches to tie onto, though. Rob D.
--
|