Depends on the time of year and duration of hike. In winter, I can get the asym to fit close to the hammock and thus help retain some body heat inside. In summer, when the rains down here in Houston can get quite-----impressive-----the bigger bigger tarp is probably a better idea. Having said that, the only time my hammock ever got wet (so far) was when using my Hennesey Hex in an August rainstorm.
If there is no rain forecast and I'm going a long distance or for several days, the Asym might be a better choice b/c of the lighter weight.
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Ive never gotten wet in my henessy ultralight asym in the summer rains. The thing to remember in the woods you have more falling rain. In the open you get more sideways rain at times. Setting up in a good spot is key. My first winter camp with it there was a sideways freezing rain and it got the underquilt near my head a bit, not much. I made a diy hammock sock and that problem is nixed. Saved me $300 for a cuben all season tarp with doors i was looking at.
I used the smaller tarp that came with the Hennessy Ultralight during my 2004 AT thru hike and never had a problem. I think the bottom entry helped with this. If I'd had a side entry hammock, the smaller tarp might not have been enough.
The stock is great, & can be pulled tight & in close. I even added extra pull outs, with some shock cord so that it wraps around close to the hammock in major hard wind & rain. I have added sewed on doors to my MacCat, but still have my HH stock tarp. I'm going to make a DIY Griz Beak door for one end, so that I can take it or leave it depending on the weather.
Maybe see you at Trail Daze some time in Damascus, VA, hiking with the 2004 group in the parade.
This has all been very reassuring input. I'm pretty hand with tarps and knots and I've camped under some very small tarps (I used to go canoe-tripping with a tent and a 4' x 6' polyurethane tarp), but I wasn't trusting my sleeping system to my tarp as I will be when hammocking, so I had a bit of trepidation when I saw how small the stock tarp was on my new (used) Hennessy.
Can't wait to finish my suspension system so I can string it up and climb inside it.
My thanks to all who've taken the time to post in response to my question.
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Hey Martin. good to see you over here too.
I upgraded to an OES McCat Std (10oz) when i started doing more canoe trips, but for light backpacking trips, you can rely on the stock hennessy tarp (7.5oz) to keep you dry in a downpour... as mentioned, you can't go anywhere, or sit out, but if you pick a good spot, where the trees are actually taking the brunt of the wind and rain, and just dripping it on you, you can actually hang the tarp flat, but tilted, which increases the footprint enough to where you can actually cook breakfast or dinner underneath until it's time to hit the trail again. you have to take the side anti-sway tieout from the hennesy and tie it off to the other side, swinging the hammock out of the way to make room, but it works.
for the extra 2.5oz though, i usually take the McCat... but until i could afford it, i took the stock tarp in lieu of a much heavier 8x10 i had.
Another thing that is frequently overlooked is that it is not hard to rig up a poncho as an undercover (thus making it dual-purpose) to block sideways rain with that tiny tarp. Simply add loops to the corners and run shock cord through the bottom hems of the poncho, carry a few snap links (or tie some shock cord in a slipknot) to attach shock cord lines to the loops and hammock suspensino, and you're set.
Something very similar to the Hennessy tarp and a poncho/undercover like that kept me dry for over twelve hours in the fringes of a tropical storm (~20 mph winds, 30+ mph gusts, and perhaps two inches of rain). The only reason I got wet at the end of the twelve hours is because the tarp slipped off of the ends of the hammock and I wound up with water intrusion through my whipping knobs. Now, I use a pair of mini 'biners to keep the tarp in line with the hammock suspension. (Hennessy has already addressed this with his Prusik knots, so no worries there.)
As mentioned, though, one doesn't really have a spot to cook with the tarp and hammock set up. But...if you leave the hammock in its snakeskins with the tarp attached outside of them, well, it's possible to use that real estate to remain relatively dry. Just a thought.