Undercover from HH Asym Tarp

[bmike]

I'm planning on making a BlackCat in the spring - and wondering about converting my stock Asym tarp for an HH Exped into an under cover... I could move a pad there, or use it to work with a homemade quilt...

Thoughts? I'm assuming the shape can be had by setting the hammock and pinning / tracing the tarp to it, then sewing some hems for shock cord to pull it tight to the hammock body.

[Just Jeff]

Check here for a pattern: http://www.tothewoods.net/ImagesStay...flyProject.pdf

But experiment and do it however you'd like. Post pics when you're done!

[bmike]

Check here for a pattern: http://www.tothewoods.net/ImagesStay...flyProject.pdf

But experiment and do it however you'd like. Post pics when you're done!

i knew i saw something on here somewhere... thanks for the link.

[Peter_pan]

You will get a non breathing bottom.... which will cause eventual condensation issues... BB58 and Turk have both recently posted on the condensation problems of non breathing bottoms or bottom components....YMMV.....or if you don't use it in too cool of weather you may not notice the issues.

pan

[kohburn]

if you take a pointer from construction insulation guidelines you want the vapor barrier on the warm side of the insulation. this does two things: it keeps moisture out of the insulation, and it maximizes the temperature of the vapor minimizing its ability to condense.

in a sleeping arangement this can get tricky as it will trap the vapor around you quickly increasing the humidity of the airspace. the key would probably be to allow enough ventilation to releave the humidity out past your body without letting cold drafts in.

[Just Jeff]

Good point on the first issue.

Second point - you don't want ventilation if you're using it as a true VB.

Also, VBs in construction aren't actually vaporproof - most types of housewrap have some level of breathability, but usually not enough for a hiker to consider it wp/b, and many housewraps are actually perforated for this reason. (At least that's what someone smarter than me told me - I'm not a housing contractor so I have no direct experience with it.) VBs in hiking are always vaporproof.

[kohburn]

Good point on the first issue.

Second point - you don't want ventilation if you're using it as a true VB.

you will want enough ventilation to control how much moisture you build up, in a sleeping bag this can be as simple as tightening or losening the draft tubes

i don't think its even an issue with under and overquilts and there is no seal between them.

Also, VBs in construction aren't actually vaporproof - most types of housewrap have some level of breathability, but usually not enough for a hiker to consider it wp/b, and many housewraps are actually perforated for this reason. (At least that's what someone smarter than me told me - I'm not a housing contractor so I have no direct experience with it.) VBs in hiking are always vaporproof.

house wrap is not a vapor barrier (despite being called so by many in the industry who don't know better) so much as a water plain to prevent wind driven rain from getting to moisture sensative materials while allowing the house to breath, much like DWR fabrics. actual vapor barriers used in construction are solid plastic sheeting or sprayed in expanding polyurethane foam insulation.

[rpettit]

I use the HH undercover, which is silnylon just like the stock tarp. I have never experienced any condensation issues from below freezing and up at various elevations throughout western NC. Even when there is some condensation on the underside of my rain tarp from breathing, none in the undercover.

[bmike]

I use the HH undercover, which is silnylon just like the stock tarp. I have never experienced any condensation issues from below freezing and up at various elevations throughout western NC. Even when there is some condensation on the underside of my rain tarp from breathing, none in the undercover.

good to know... thanks.