Jan 25, 2009 at 11:27 am #1233523
This is a concept sketch for a MLD DuoMid bug net that has the support pole base offset 6" towards the door to provide room for a 30" wide nest, 3" from the back wall, and 3" from the pole. It is 86" long. The tub is 3" high. The net hangs 3" below the 54" peak, in a to-the-ground pitch.
This was done in Google Sketchup, which can automatically calculate the dimensional call-outs, essential for pattern layout.
Now that I've got the hang of it, using as-built dimensions and any floor configuration, a new version could be created in about 6 minutes. (Which is good, because I see a couple of errors.)Jan 30, 2009 at 8:39 pm #1474200
Nice work Greg! I can't wait for my DuoMid to arrive! On your next version consider increasing the bathtub floor height to 5" per leaked specs… Also, shouldn't the lengths be the same on both sloping walls (towards your head and feet)? Presently one is 5'4 3/4" and the other is 5'8 3/4"…Jan 31, 2009 at 7:25 am #1474267
"shouldn't the lengths be the same on both sloping walls?"
Brian – Nope, the net is symmetrical end-to-end, but not side to side. And that is the challenge Sketchup meets so well. I do ok with geometry and trig, but I'm not up to compound angles, over and over and over.
The back of the Mid slope towards a pole, so the length of the back edge is greater than that of the front edge.
If the pole were vertical you'd have a right triangle. Moving the pole towards the door allows the bivy more room and though the 'pole side' begins to slope, it will always be shorter than the 'wall side'.Jan 31, 2009 at 8:02 am #1474275
Greg – Thanks for explaining why they were different. Makes sense now that I consider where the peak is. I hadn't noticed that one of the dimensions were for the rear slope and the other for the front slope.
I was thinking last night that it would be so cool to have a inner net made from mesh, but also one made from, perhaps, Momentum90 for an inner winter tent. What is momentum, 1 osy? One could leave the bivy at home and not feel so claustrophobic.Jan 31, 2009 at 8:24 am #1474280
Brian, I was thinking along your lines with the nylon tent inner for a project. With the Momentum being callenderized, though, I'm not sure how great it would be… I remember seeing a post in the last couple weeks (I think about windshirts?) that mentioned a similar ~0.9oz/yd fabric that wasn't callenderized, but I don't remember the name. Perhaps a bit better breathability, lower condensation. Anyone?Jan 31, 2009 at 8:31 am #1474282
Huzefa SiamwalaBPL Member
I think 20D taffeta is perhaps the lightest non-calendered wind resistant fabric.
http://www.nunatakusa.com/site07/main_pages/fabrics_nunatak.htmJan 31, 2009 at 9:34 am #1474286
Roger Caffin has a lot of experience with MYOG tents that have breathable inners. Roger – what fabric would you suggest?Jan 31, 2009 at 10:18 am #1474289
@jcarter1Locale: Pacific Northwest
That's a pretty cool program; nice work. Can it calculate the surface area for individual sides? You could probably get a pretty good weight estimate that way.
If you have a chance, would you we able to add a foot or two onto the head-side width? This would make for a funny shape, but would give more room for arms to stretch out and some gear stored inside the tent. You may have to put the pole inside the shelter at that point, but I personally see a few advantages to that (bug-free adjustments, simpler setup with no clip-on requirements of the bug net, and the pole would keep wind blowing the mesh inwards).
I'd be very interested in the weight difference between this and your design.Jan 31, 2009 at 10:57 am #1474295
Not to hijack Greg's thread (we just love your sketch, Greg)–
I think a standard, uncoated 1.1 oz silny would be fine. But MSR, for example, is using an incredibly silky, lightweight nylon on their HP tents. All I know is what they report: 20Dx330T ripstop nylon 66Jan 31, 2009 at 7:13 pm #1474379
This bug bivy is 30" wide by 86" long, has a 4" lip, and weighs 9.5 ounces. The netting is Nano and the bottom is silnylon 1.3 The support pole is at 54" for a tight-to-the-ground pitch, and 5" towards the door. There is about 4" between the netting and the DuoMid, all around. The pad is a full size ThermaRest
.Jan 31, 2009 at 11:38 pm #1474423
Those are AWFUL heavy looking tent stakes you have there…
CheersJan 31, 2009 at 11:44 pm #1474424
Depends on what you want the tent to handle.
3-season? I guess netting would do.
4-season & snow? Then you need something like Pertex Momentum or Microlight, or some other very light uncoated wind-resistant fabric with a good DWR. There are plenty of these on the market, and I am not personally familiar with them all. Email places like OWFINC and Thru-Hiker and ask what they have and recommend.
You will need a vent at the top, and that is a bit tricky to get right. Without it you are going to have fun with condensation.
You may want to consider having the fly go right to the ground if you are serious about using it in the snow. In bad weather the spindrift can get under the edge and pile up inside. And you need to have some air inlet as well – tricky with that design. But now you may be getting outside the original concept.
CheersFeb 1, 2009 at 6:40 am #1474435
"Those are AWFUL heavy looking tent stakes you have there…"
I only use them in the garage and on Canyonlands slickrock.
g.Feb 1, 2009 at 8:09 am #1474449
Greg – Nice work! How is the headroom when you sit up in the bug net? Do you need to lean much towards the pole?
Roger – Thanks! I appreciate your suggestions regarding the interior cloth.Feb 1, 2009 at 8:35 am #1474454
Brian – There's not a lot of room in there. Walls taper fast. But bumping into the netting is not an issue. It's dry and warm. And there is a lot of room between the net and the Mid so I don't feel constrained. When I'm prone I've lot plenty of room.
I wanted a floor to keep me and gear dry, a bug net big enough to roll around in, that would work with or without a shelter. I got it.Feb 1, 2009 at 9:08 am #1474459
Got it! I figured it would be tight while sitting. But, like you said – you've got plenty of room between the net and tent wall and also while prone.Feb 3, 2009 at 11:34 am #1475081
Greg, nice work! Those are some great looking tent weights, er, stakes! Actually, they seem quite handy for such projects. Since we all know someone will ask at some point, I might as well be the one: What did you use for the zipper?Feb 3, 2009 at 11:38 am #1475083
The zipper is a basic YKK #3 Coil with two double-pull sliders.Feb 3, 2009 at 12:49 pm #1475105
> The zipper is a basic YKK #3 Coil with two double-pull sliders.
I know most tent manufacturers use at least #5 for their tents, but I firmly believe this is only because so many novices bash gear mercilessly.
I have used #3 plastic coil zips on both my summer and winter tents for many years, and never had to replace one yet. No problems at all, with one exception. That is when the winter tent gets wet in the evening and the zip freezes overnight. But that is fairly rare, and even so the zip can be opened with a little care.
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