Input on MYOG tarp/tent design?

[Kattt]

Looks really nice! Quite a project to take on. Thanks for posting the pictures .

[Jerry Adams]

Nice looking tent

Innovative use of building wrap for prototype

What about condensation? It looks like the door is not directly over your sleeping bag so you could leave it open or partially open for ventilation.

[Jim Colten]

Very nice.

You might find it useful to add guyline loops near the center of the roof and maybe the two larger sides. Especially if you will be using nylon fabric (stretchy and expands/contacts with temperature/moisture changes)

[Kevin Beeden]

I like it very much, and it may well just inspire me to find that missing roundtuit…

I'm pleasantly surprised to see that you didn't seem to need any side guys at all, even with the side rolled up. I'll have to go away and try to get my brain around that…

[Sam Farrington]

Agree that unless you take your chances with a spreadsheet or pattern, having the seam allowances face out is the way to go. When you get the catenary cut just right, you can fold them over and sew or bond them.

[David Drake]

Thanks to all for the comments.

Katharina: Thanks for looking and for the encouragement. I'll keep posting pics on this thread as the project continues.

Jerry: Best thing about the lumber wrap is it's free and would otherwise be thrown away by the lumber yard. Re: condensation. I've thought about this, and this will be my first single wall shelter, so it's not an area where I have a lot of experience. Just raising the canopy a few inches off the ground noticeably changed air flow, and I've thought about adding a top vent.

Jim: Loops at seam midpoints are a good idea–extra protection for wind, etc. I have loops at each end of the ridge, but it's hard to see in the photos. Still debating line locks vs. tautline hitch to re-tension quickly when the nylon sags.

Kevin: Yeah, being able to lose one stake and totally roll up a side was a pleasant surprise. I have the sketchy physics plugin for SU, but I don't think it's *quite* sophisticated enough to predict stuff like that. Even with the side rolled and no guys I can grab the ridge and give it a good shaking–seems plenty solid. Part of this is there's very little slop at the connections between spreader and pole tips, which seems to transfer loads. Obviously, with the poles angled off vertical (in two planes) the friction between pole and ground is very important. Going tips down would probably be more secure, but I haven't figured out a socket for the pole grips that's nearly as elegant as pole tips + grommets.

Samuel: I'm hoping once I get the prototype dialed in, I'll be able to make a pattern from it for the silnylon version. Interestingly, with the stiff test fabric and the seam allowance out, you can just about see the right curve as a shadow along the seam (see first picture). For me, the coolest thing about this process so far has been the "aha" moments, every time I see why tent designers do the things they do.

Sometimes reinventing the wheel can be a pretty good way to learn.

[Jerry Adams]

I made a similar tent, except it had a peak rather than a cross bar.

I had vents on all 4 sides, at the top, but it still had a lot of condensation.

Leaving the door open helped, but since there was a peak, the door was directly over my sleeping bag, so water tended to drip onto my bag. Also when it was raining and I opened the door. Your cross bar design should be better because then the door will not be directly over your bag, especially if you slide the bag slightly away from the door.

Having a few inch gap all the way around also helps with condensation.

[David Drake]

Hmm. That suggests trying to sleep two in this w/o widening might cause trouble brushing condensation from side walls. (Not really a problem, as I designed it to be solo) As is, the footprint is bigger than my Seedhouse SL2, but that's double walled (and pretty snug for two).

Seems like a set of extra loops and toggles (or some such) so the door can be rolled only halfway up might be worthwhile.

For the mock-up I used a wooden dowel for the spreader. For the final, I was thinking either a CF arrow shaft (can buy locally) or alum. pole section from Quest Outfitters. Any thoughts?

[Mark Ries]

David I think you might want to check out how lightheart(the solo model) makes their spreader bar as it would simplifyn things IMO and if it was me I would sew a sleeve for the bar to slid thru rather than nothing or velcro if the sleeve was tight the bar would tend to wander less in the wind. The velcro works fine in my lightheart but I also dont like velcro around lightweight mesh

[David Drake]

Thanks Mark. I guess the photo of my spreader bar assembly above isn't very clear. It's basically two pieces of grosgrain with sleeves sewn into the ends to receive the spreader and grommets for the pole tips. The grosgrain is bar-tacked to the underside of the canopy near the grommets, and the two free ends are connected and held taut with a ladder lock (actually a side-release buckle, as that was what I had lying around). Weight of the assembly is about 0.3 oz. I could probably make everything with tighter tolerances and spring the spreader into place to get rid of the ladder lock.

I looked at Lightheart website–nice tent. No details of spreader assembly, however, so I can't tell what the setup is. Obviously good detailing makes or breaks a tent. Because this project is just for me (no commercial intentions at all), I'm not above borrowing from proven designs. As I said above, I constantly feel like I'm reinventing the wheel, but that's how I learn what works.

[Mark Ries]

It is alot like pvc 1/2"and the ends are bent with heat to the angle that accepts the trekking poles so no grommets are needed and the bar protects the tent cause the tips are slid in it. And as I recalled the brand and type are marked on it. Do a search for sharkbite u860w10 and it is sold in 10'lengths for less than $4. I didnt look where it could be had from if even in this country. The one lightheart supplies is about 13" overall with about 1-1/2" bent at a 45 deg angle on each side and it weighs 8 tenths of an oz or 22.5 grams. And by the way the tent is looking nice but you might think about running a cord from treking pole handle to treking pole handle to keep the downward pressure from spreading the poles

[Jim Colten]

Jim: Loops at seam midpoints are a good idea–extra protection for wind, etc. I have loops at each end of the ridge, but it's hard to see in the photos. Still debating line locks vs. tautline hitch to re-tension quickly when the nylon sags.

The stars in this photo is the location I was trying to describe:

[Sam Farrington]

Suggestion: PVC pipe comes in both thick and thin wall. The thick wall would be more sturdy.

[Mark Ries]

ya know I dont think the problems with the spreader bar on the light heart tents has anything to do with the materials its made out of, its plenty sturdy, mine is. It is the problem of trying to make a one size fits all piece to fit all the different treking pole tips out there. And the problem has been solved by lightheart by having something to hold the spreader bar to the fabric so it can not walk around as the wind blows. Some of the origional tents did not have this as the tent the guy had the poles drop in his back yard did not. And I also wonder how tight his treking poles were after the sil nylon streched from rain. He was not even in it he just left a tent set up in his yard during storms, Then wrote a report. I just wish for a sleeve of fabric to hold the bar rather than velcro which can get stuck to ultra light screen (no see um) fabric and cause rips. Also I dont think the piece is pvc It seems much stronger and less brittle I dont want to try it but i think this stuff would bend to a much tighter radius than pvc before it would break If it would even break

[David Drake]

Thanks, everyone. Keep the comments coming. Maybe today or tomorrow I'll have time to make a catenary template and resew seams.

Mark–The material you're describing sounds like PEX plumbing line. It comes in several diameters, and is sold either in 100' coils or straight sticks. I've got some of the 3/8" coil stuff left over from a plumbing project–it weighs about 0.6 oz per foot which seems a bit heavy. Also, as you say, I'm pretty sure the straight stuff would be necessary for a spreader. Interesting idea–I like the idea of heat-forming the ends.

Jim–Thanks for the picture, I get it now. Could be a good addition. To keep the places I have to seam-seal to a minimum, I think I'd make the canopy without the mid-panel tie-outs first, then test and add if necessary.

[Bobby McDonald]

I've been reading your thread, it had a feel of a Terra Nova Argon 900 a British Company who make main stream tents. Your prototype pictures confirms this. Check them out, you don't want to be stepping on toes.

Great effort and an interesting thread of debate.

[Marc Penansky]

I can confirm for you that the Ridge Pole (what has been called the spreader bar in this thread) in the LightHeart Tents is 1/2 inch PEX or cross-linked Polyethylene. I make them myself. They fit the vast majority of trekking pole tips snugly and for those that have unusual tips, I have molded some custom ends for the trekking pole tips to go into.
Please PM me if you would like more information as long as you are only building a system for your personal use.
Marc Penansky
LightHeart Gear

[Kevin Beeden]

> Check them out, you don't want to be stepping on toes.

Bobby, David's made it pretty clear that this is a personal, non-commercial venture, so there are no toes to step on for design or patent rights.

[David Drake]

Thank you, Marc. That's very generous. And a neat bit of thinking to heat-form PEX. I can also imagine using short pieces of heat-formed PEX to form connections between hiking pole tip and CF pole. Similar to the vinyl hose Daryl Clark was suggesting up-thread, but rigid (ie, moment resisting).

Bobby–not familiar with that Terra Nova tent but will take a look.

Just to reiterate–this is a purely personal project, aimed at my own education, no commercial intentions at all. I admire cottage gear makers, but don't want to be one. As I said in the OP, I'm borrowing heavily from pictures published on maker's websites, but
haven't looked at any similar designs in person. Maybe one of the benefits of MYOG is being able to "crossbreed" different designs, which would clearly raise ethical issues if done with commercial intent.

At most, I have an interest in teaching the design development *process* I've used here (digital model to pattern to full-scale mockup to working version) within the context of an architectural design studio.

[David Olsen]

Move the tie out where the over the leg star is closer to your feet. Keep the fabric off
your knees when the wind is blowing.

Careful about infringing on Nessmuck's shelter patents. ;^).

http://www.google.com/imgres?imgurl=http://www.gutenberg.org/files/34607/34607-h/images/illp26.png&imgrefurl=http://www.gutenberg.org/files/34607/34607-h/34607-h.htm&usg=__crD-GllgVZwfltZZFbTXi-C5zQY=&h=677&w=500&sz=65&hl=en&start=32&zoom=1&tbnid=3Lsb-fFGVd5i2M:&tbnh=137&tbnw=101&ei=AoDdTe78AebSiAK6ptEC&prev=/search%3Fq%3Dnessmuk%2Bshelter%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26hs%3D6xh%26sa%3DN%26rls%3Dorg.mozilla:en-US:official%26biw%3D1070%26bih%3D598%26tbm%3Disch0%2C850&um=1&itbs=1&iact=hc&vpx=591&vpy=171&dur=3326&hovh=261&hovw=193&tx=48&ty=284&sqi=2&page=3&ndsp=17&ved=1t:429,r:3,s:32&biw=1070&bih=598

[Bobby McDonald]

No slight was intended – just thought I'd give my musings on this discussion.

[Roger Caffin]

He got a patent for that?????????????????????????????

Cheers

[David Olsen]

kidding

[Kevin Beeden]

> It's basically two pieces of grosgrain with sleeves sewn into the ends to receive the spreader and grommets for the pole tips.

Aha! So you do have a real, stiff bar in there. From the photos, it looked like it was just webbing of some kind. That's why I was surprised that it was so stable with no side guying. If there's a bar across the top, it now makes more sense…

As for the design 'copying' issues, once again, we see common designs evolve from looking at the same basic problems. Even with no knowledge of other solutions, the same designs appear from the basic mechanics of the problem. My X-pole design, for instance, started as an asymmetric design, with a shorter 'head' end, which came to a single point at the end, and had a double-pointed end to make a box for the feet, i.e. very similar to David's original images.

Then I added the flat sides to reduce the size of the panels, to keep the panels taut without needing to use mid-panel guyouts; same problem, different solution. This solution also gives more space under the fly, and may allow two doors in each side.

Oh, one little detail of the crossed pole solution not visible in the SketchUp is that the pole handles thread through the strap of the opposite pole, which hold them securely in place, and takes some of the stress off the flysheet.

[David Drake]

Modified my mockup with cat cuts on all seams. Really tightened the pitch. Cuts on the side seam are maybe a little more radical than necessary, and I'm not sure how the stress from the tighter side walls will affect a zippered opening. Still a little fiddle-factor with pitching, but getting better.

Just got the Bernina Record 830 that belonged to my grandmother, so I have a brilliant sewing machine and am ready to start on the actual tent in silnylon when I find time.

Here's pics:

[Author]

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