XX Tarp Tent – A Work in Progress

Hi Sam

I n t e r e s t i n g . . .
I haven't seen an thing quite like that before. Off the top of my head, I can see that you will have to come up with some neat way to pitch the tent – how to get the poles in place.
H u u m m …

Cheers

That's really cool. I'm sure you've thought of tons of options for the awnings already. Take a look at some of the shelters with similar profiles to see what the successful ones have done for geometry and materials. It looks like breathability is high on your list of requirements. Pertex Endurance or Epic fabric could be a solution for you if you don't need a perfectly dry vestibule. Too bad Dri Ducks ponchos can't stand up to the stresses of being a shelter. Best of luck, I can't wait to see more pics.

Interesting design, thanks for posting that

Poles 9.5 ounces
fabric must be 6 ounces

pretty light but not super light

I wonder how it would do in wind?

What happens if wind blows rain in the sides?

"you will have to come up with some neat way to pitch the tent"

Roger,
Don't know how neat it is, but the plan is with the tent spread on the ground and a peg holding the rear awning if need be, then at each canopy end two poles will slide under the canopy edges and over the netting, through the break in the netting at the cross point, and then be pointed and pushed to the general vicinity of the internal elbows. Ditto, the other side. There will be zip sliders at the tops, as well as the bottoms of the net doors, so they can be opened from the top, and one can reach inside. The end covers, or awnings, will also allow one to unzip up top and reach inside and underneath the peaks. So the plan is to reach inside, underneath the peaks, and attach the upper pole tips to the elbows. The tip inserts are drilled out to have a snug press fit over the Ti rod so everything will stay in place during pitching. With the elbows in place, the bottom ends of the poles will be inserted in the receptors (instead of the usual grommets). Once all four bottom ends are in the receptors, the tapes from the receptors to the ladderlocks sewn to the canopy corners are tightened up (not captured in the photos – lousy photographer). As the canopy rises, lines from the 4 bottom floor corners to the receptors will hold the pole bottom receptors in place so the poles cannot spread wider than the intended arc. That's a mouthful, but once the upper pole tips are fixed to the internal elbows, it won't look much different than any other dome of similar design going up. Guess that's why a video of the pitch is intended. Will the plan work? Pretty sure.

"sure you've thought of tons of options for the awnings already."

"Pertex Endurance or Epic fabric could be a solution …"

David,
Something like the GG One awning in the front, and at the rear, a fairly common triangular awning, such as the ones on the Hubba, or the Rainbow. Gave up on Epic Malibu because of the weight and almost total loss of water resistance when the surface tension is lost at around 1500mm HH. Also, polyester Malibu would probably not stretch enough for this design. From Alan Dixon's article on this site, the urethane coated WPB's appear to transmit vapor only when sufficient humidity pressure is built up; as with a jacket, for example. So, it will be just the best waterproof sil available for the canopy, and more sil or one of the Cubens for the awnings – not sure yet.

"fabric must be 6 ounces"

"I wonder how it would do in wind?"

"What happens if wind blows rain in the sides?"

Jerry,
The sil is ca. 2005 40 den 1.36 oz from Quest. Expect under 2# total, but have expected before. So it's a wait and see on the weight.

This design was quite a bit more rigid and stable than the single cross domes I tried. Once full size frames were built, realized that none of the single cross two pole domes had much rigidity rotationally, no matter what gimmicks were tried, and strong winds could raise heck with them. Even strung with all the lines, this frame wobbled like the dashboard doll in the BPL store:

This XX frame, once the the canopy is stretched over it, is rock solid, both rotationally and front to back; but there is slight side-to-side sway when pushed from the sides; hence, the loops for the side tie-outs from the pole crossing points. Only concern about the wind is the need for good ventilation at the front; so if the wind shifts all the way to the front of the tent, the canopy will baloon. Front and rear guys from the awnings in addition to the side-to-side guys should keep the tent from blowing away, but yes, balooning can be a problem when camping in exposed locations. A taut canopy, as this one has, helps a lot with that, though.

The alternative is to run the canopy and the awning down to the ground, as TT did with the second version of the Scarp, and as with the superlight Terra Nova tents.
Have no desire to camp in a sweat lodge, so having none of that. Older tents, with no more coverage than planned for this one, have kept me dry and resisted wind blown rain in exposed areas so extreme that the PU fabric coatings failed before any water blew in from under the edges or awnings. So IMO, total coverage for 3-season shelters is over-rated, is more psychological than practical, and just makes folks uncomfortable in foul weather due to the lack of ventilation. Even in heavy snow, I'd be very worried about air quality with total coverage covered by a foot or two of snow.

But please note: This design can readily be done with total coverage for those so inclined.

Hi Sam

Ah, OK: the elbow is retained inside the tent. That works – I did that myself in the late 1960s.

About 7' square, 70 d nylon, fibreglass poles – we hadn't even gone metric at that stage. It took the weather very well under some extreme conditions in SW Tassie – winds direct from the Antarctic. The big weakness was not the poles going sideways – they didn't, but the centre tended to pop downwards when pitched under a cliff when the downward vortices got too much. But a quick whack of the hand would push the top back up. I did add diagonal tension guys inside from the corners to the peak.

The thing had poor ventilation of course, but the steep roof and the separate groundsheet meant things were quite livable despite that. You can see the guy ropes on the poles and the sides: they were generally sufficient.

The notable thing about it was what it looked like when I got inside it to fix the last pole into the 4-way elbow at the peak. There were comments about wrestling matches inside …

The one thing which might give a problem will be where the fly presses on the poles. Rain hitting there will create a far higher pressure, and you might get some leakage along the pole lines.Changing from silnylon to EPIC would, in my opinion, be a total disaster there.

Interesting.

Cheers

That's interesting, Roger. Hadn't thought of that. In some of the older posts about the BD Epic tents, people mentioned that some water tended to collect on and run down the poles, even when the rest of the inner surface was dry. Will look for and report on that when I do the update on this silnylon number.

original design, you could, have an arrangement by which the frame is set up first then the tent is stretched over, hang an inner tent inside. Why not? Tons of possible configurations, super strong up to the breaking point of the poles, easton ultralite poles more robust than carbon ,good weight.

I hadn't thought about the higher impact force of a water droplet against the pole. I may be mistaken in thinking that it was condensation collecting on the pole due to higher thermal mass.

discusion reminded me of something. In my geology days we used big canvas tents with aluminium frames, they only weighted about 400lbs, but the rule was, NEVER TOUCH THE INSIDE TENT WALL IN THE RAIN! . Which was because it drew the water through the fabric by osmosis creating a long term drip, talk about low HH!!

Samuel,

I love your design! Very clever. Obviously a lot of thinking went into this. Good job of building to accomodate the characteristics of the materials used, particularly the carbon fiber poles.

You said "but there is slight side-to-side sway when pushed from the sides; hence, the loops for the side tie-outs from the pole crossing points".

Not quite sure which movement you are referring to given the two possible definitions of "side" with a side entry tent. I can assure you, however, that things really tighten up when the triangular vestibule/beak pieces are added to the long sides of the tent. Here's a photo of a similarly shaped tent showing one side vestibule:

When the vestibules are pulled out and tightened on both sides of the tent in the photo it really tightens things up. I've used it in 40mph winds without any other guy lines.

Your tent canopy is nice and wide (36") so the vestibules or beaks could be made of uncoated (non waterproof) 1.1 ounce nylon and weigh only 1 or two ounces each (no zippers). (The tent shown in the photo has a 24" wide top canopy.)

Daryl, good looking tent! Did you make it yourself? Ive been wanting to make a shelter like that for use in windier places. My 9×5 tarp works good below treeline, but I need something that can shed winds from all directions.

Thanks for the helpful comments.

"You said "but there is slight side-to-side sway when pushed from the sides; hence, the loops for the side tie-outs from the pole crossing points".

"Not quite sure which movement you are referring to given the two possible definitions of "side" with a side entry tent."

Daryl,
Sorry for the confusion. By "sides," I meant the surfaces the poles are under; so, when looking at the tent from the front, the sway is to your left and right. It is much less than with some single pole "side" entry tents, like the Hubba, but should be almost eliminated for use in high winds by running guy-lines from loops at the points where the poles cross out to pegs on the left and right. Hope that is clearer.

Agree that the staked end covers will also help with reducing sway, not to mention keeping the tent from tipping over front-to-back. You have got that front end cover very taut, all things considered. I am thinking about bringing a similar front end cover only about half way down to the ground, and using WP fabric rather than netting for the lower part of the door. This should keep the rain out, but as mentioned earlier, will allow the wind in, and allow some balooning. Awnings with a little more coverage on the netting doors have worked well on my Bug Dome in keeping out wind blown rain:

So it is just the wind itself that worries me if the front awning does not come all the way down to the ground. The consensus in the many posts I've read on BPL seems to be that this is not a good idea. Joe Valesko added bottom beaks to his awning to address just this situation. I really like being able to cook in the rain under a front awning, though.

Samuel,

"but should be almost eliminated for use in high winds by running guy-lines from loops at the points where the poles cross out to pegs on the left and right."

I agree. Thanks for the clarification.

Daryl

For anyone interested in using this design for a project, please note that the length of the long rectangle that is the main canopy fabric piece has been corrected from 11.5' to 10.66' (128"). Sorry for the error.

Samual,
Great design! I was wondering what the length of the poles you used?
Fred

Fred,
There are 4 poles. Each one is 6.5' long, and is made up of 5 carbon fiber tube sections. The sections are made from Victory V-Force V6 300 wrapped carbon arrow shafts that weigh about .265 oz. per running foot. These are a little heavier than Fibraplex poles, but lighter than Easton carbon FX, and much lighter than Easton aluminum alloy poles or DAC Featherlight poles.

Each pair of poles joins inside the tent's peak with an elbow attached to the inside of the canopy and made of a 3/16" outer diameter titanium tent peg, at which point the combined pole length after attachment to the elbows becomes 13'. The idea was to limit the four lengths to 6.5' so that they are easier to handle and install on the tent than the longer poles used in most domes.

There is more about this in the original post and the thread, above, with a picture of the disassembled and folded pole set, the total weight of which is 9.5 oz, including the tips, shock cord and 3" long external alloy ferrules made of Easton .344 oz tent pole tube material that came from a TarpTent Scarp's crossing poles at a price lower than charged by Quest Outfitters for the same tubing.
It was perhaps risky to limit the ferrules to 3", rather than the usual 4" used for internal carbon ferrules, but the goal was to save weight. The fit of the ferrules over the Victory carbon tubes is not tight, but snug, and I found in a number of break tests that the snug fit makes the carbon poles more resistant to breakage.

Thanks for the info about the poles Samuel. I think Your design looks great. It will be interesting to see how you progress with it. Fred

Sam,

I really appreciate your direction to this thread as part of your thoughtful response to my inquiry. Your design is elegant and beautiful. I have a thought about livability: rather than stand your idea on its head I’m thinking about standing it on its side. That is, reorienting the panels such that they are rectangles with the long sides on the ground along the long axis of the tent. That would create more of a tunnel design with the vertical (netted or beaked or vestibuled) ends at the head and foot end of the structure. That way there would be no angled wall limiting head space when moving from laying down to sitting up. Also eliminating the nasty foot box wetting of an angled wall at the foot of the structure. I’m thinking that orientation might lower the overall height adding to stability in the wind while still allowing decent head room and a feeling of more space without having to avoid the angled wall. I hope this makes sense to you. Let me know if I’m being clear and what you think about this idea. I admire you’re ingenuity and originality.
Bruce Baker

What is the reason for the Ti elbows? Seems it would be easy to have two overlapping hoops (“actual double rainbow!) that crossed where you want them to? Are the poles really stiff?

Michael,

Thought I’d dropped through a time warp for a second until I realized you must have brought this old thread forward.

The elbows have several functions.  They provide peaks at the ridgetop, that help to shed precip.  So instead of forming a parabolic arch, the poles form what I believe is called a gothic arch.  The elbows thus modify the shape of the hoops, lower the profile of the tent, and help to lower wind resistance.  This in turn reduces the space at head and foot of the side-entry tent, eliminating weight; albeit the walls are still bowed out enough to sit up from a sleeping position more easily than in an A-frame tent.. The elbows also hold the shape of the tent more rigidly than do the long hoops of single pole crossing, two hoop domes, or ‘wedge’ domes.

The Ti elbows used in this old thread, have been lightened to around 0.14 oz each.  After  calculating the weights, I’ve also decided to add a ridge pole that will support the ridge even better in snow.  I don’t hike overnight in the winter; but have been caught in deep snowstorms in the shoulder seasons in places like the Adirondacks.  And the ridge pole will add structural strength to the tent in high winds.

If I understand your post, you are talking about modifications of the crossing points in two-hoop tents where the poles cross twice.  Unlike using elbows bent to a chosen angle, the hoops dictate a parabolic shape, so choices of crossing points are more limited.  While this has been a popular design, such as with the Terra Nova Solar One tent, the roofs of such tents have large near-horizontal areas at their tops, which collect snow and rain.  And hard driven rain will eventually wear down sil coatings on roof fabrics and create leaks.

You can experiment with where poles cross, but I think you will be much more limited if using hoops without elbows.

No, the carbon poles are not really stiff, but are much stiffer than, say, the heavier fiberglass poles that were offered on Moss tents.  The design will not work unless the outer fabric, which forms a bias stretch over the pole frame, also helps to hold the tent’s shape and rigidity.  That is why except for the tent floor, I’ve decided to go to silpoly.  As noted in a recent post, silnylon expands when wet, and no longer helps to hold the pole frame in position.  When vestibules are added, they also add to the tent’s rigidity.  If all these factors are not enough to cope with the elements, there are also conventional guylines to hold the tent and poles in place.

Sorry, I have noticed a lot of old threads get dragged out of their coffins – I usually notice, but I guess this time, I did not.  Sorry!

Michael,
And I’m sorry if my response sounded critical.  Only in virtual reality do we get dragged alive out of our coffins.  I enjoyed responding to your post.

Bruce,
For some reason I didn’t catch your post. Not sure I follow. A sketch or photo of a model might help me.
Should note that I’ve been very careful to build the XX with double walls, and large enough so that there is no bumping of the head or feet against even the inner walls when lying down or sitting up.  As you will see when the tent is done.

One thing that frustrates me a bit, is that folks look at A-frames and other tents in which the walls descend in a straight line directly from the tents’ ridges or peaks to the ground, and have no problem with that. Even when those walls become somewhat concave due to silnylon sag or catenary cuts. An example is the walls of a TarpTent Moment descending from the spacious area under the hoop to the head and foot ends.

I think dome tents waste a lot of space and create unnecessary weight by providing room for sitting in areas where only enough space is needed to for head and feet while sleeping.  Even so, the XX tent walls bow outward, with a deflection of 8 additional inches of space over a sleeper’s head and feet.

There was even a thread with drawings that showed a human figure sitting up hinging only at the hip joints, an impossibility because the head and torso are much heavier than the legs, and trying to sit up that way would see-saw the feet into the air.  In reality, we sit up by flexing our spines and/or using our  hands or elbows until our center of gravity moves forward.

But I’d love to see an image of your idea, here or on another thread.

Sam,

No problem. I appreciate your reminding me of the double wall and the 8 inch convexity. My idea of a long skinny tunnel with a low height would only tighten space without reducing weight, as I reflect on it. I look forward to seeing the next steps in realizing your idea. Truly original.
Bruce