- Jun 16, 2017 at 5:47 am #3473620
OK I must have totally missed that trekking pole argument earlier as being the main reason for going tapered. Why not a small compromise with a centre gothic arch using short CF sections and a single CF strut at the rear or even a second gothic arch? That is going to add a strong point where it is needed which could mean even 20GSM fabric should be more than adequate. The added weight of the CF poles being offset by the lower weight of the tent fabric because fewer strong points would be needed, externally sleeved naturally.
Not an original idea; Gerry Cunningham in his little 1950 DIY book suggests using bamboo for this purpose
You would get a shape similar to the old Blacks Tinker tent of the 1950s but at a tenth the weightJun 16, 2017 at 7:28 am #3473637
Edward – thanks for the input!
There’s a pic of Gerry’s DIY design here: http://www.oregonphotos.com/Gerry2.html
It would strengthen the side panel for sure, and it’s not a daft idea weight-wise. On a tapered design I’d need around 2.4 meters of pole, with a weight of around 100 grams + joints + sleeve + sealing tape. The weight saving of 20d vs 40d RSBTR silpoly PU would be around 120 grams.
But I do think I’d be in danger of over-engineering the thing. It complicates construction (I don’t have access to a machine shop for the arch), and it adds more stuff to set up/pack/break/ as against simply using the 40d with side-guys. I’m a klutz – one fine day I’m going to step on a pole…
The only example I know where this side arch was implemented commercially was a very heavy tent designed for Antarctic use. There have been generations of solid mountain A-frames that relied on side-guys. Granted they were using heavier fabrics, but I know that the current 40d TrekkerTent Stealth 1 is pretty much strong enough for my requirements, and I would be adding sleeved A-poles and better side-guying for a greater margin of safety. Plus the RSBTR 40d silpoly PU has low bias stretch for the weight. It’s interesting that Cunningham didn’t use the idea on his Gerry expedition tent.
I’m open to persuasion, but my gut feel is to go for the simpler solution. If I was going to innovate, I think I’d be more drawn to Rene’s pyramidal idea – it’s elegant and adds little weight. But as I said above, I’m concerned that it would be difficult to get a tight cut for the panels, (and it might be very sensitive to a good pitch).
On the Nothing New Under the Sun front, it’s striking how that old Blacks Tinker anticipated the design of the current Yama Cirriform. Though I can’t remember ever seeing a Tinker in the field – it wasn’t one of the more popular Blacks tents, and I grew up in Blacks country.Jun 16, 2017 at 4:07 pm #3473704
Poles weight: switching from standard aluminium tent poles to carbon fibre did halve the weight of the poles for me. Worth considering. Trekking poles at one end, CF tubes at the other? If you taper the tent, and I undestand the logic there for a 1-man tent, then the rear poles in CF will weigh very little. The CF poles I use are 19 g/m. If each of your rear poles are 1 m long, that is 40 g.
the twin arch design I can’t see that it offers any particular advantage over the A-frame,
Oh yes, a huge advantage in strength. Straight unstressed poles are all wobbly, but when they are bent into curves they are MUCH more resistant to movement. The curved end bell fabric seam (pole sleeve) adds to that strength as well.
Pegging down the edges – I never do this. The tension from the guys jams the poles into the ground quite well enough that they never move, and I do mean ‘never’. If you are running sod cloths around, per the photo, you can usually stick some rocks or blocks of snow or something on them.
CheersJun 16, 2017 at 4:40 pm #3473709
I owned a Tinker, they were reasonably popular in Victoria for a short time. One of its great benefits was the tall entry
If you take Rogers idea plus mine you get a tunnel / tipi hybrid sort of shape. Would be fast to put up too if the CF wand sections were left in place and the tent rolled around them when packing up [ assuming the rolled length wasn’t a problem] but as they would be exterior no real problem inserting them anyway I imagine and C-clips to hold them down weigh little and are strong.
But using a gothic arch at the rear of the tent and pegging it down with two pegs at the bottom of a triangle is surely stronger than a single vertical pole section.
Also I don’t think you need to change the shape of the tent to do this, you fit the CF wands to the tent, not design the tent to be specific to the tunnel shaped by two sets of wands the same size, one of the small illustrations in my book by Gerry seems to show two skinny bamboo wands tied in place on the outside of the tentJun 16, 2017 at 6:07 pm #3473719
Slightly off track for a moment.
I acquired a set of [ brand new] 9mm hubbed alloy poles a while ago for the very nominal sum of $5-, and I am thinking of making a tent to fit the poles so I am getting a lot of information here. I modified my pole set by disassembling and adding in an arch connector and I was amazed at how much stronger the new assembly seemed to be in the gothic arch configurationJun 16, 2017 at 6:20 pm #3473722
I was amazed at how much stronger the new assembly seemed to be in the gothic arch configuration
Absolutely! The maths for my tents would be so much simpler if all the poles were straight lines. But the tent would be so much weaker, to the point of silliness.
But note that whereas Geoff is talking about using trekking poles – maybe 20 mm thick wall tubes, I am using CF tubes only 7.5 mm OD and thin walled. I bend my poles to a 2 m radius of curvature to get the strength.
CheersJun 16, 2017 at 7:18 pm #3473726
I’m at the age and stage where I need to be able to stand to get myself dresed [ I need new hips and knees] so I am looking at a very all tent for my next project, hence my interest in strength. As tent size doubles strength needs to quadruple is the rule of thumb I was given. Which is why I am really surprised [ delighted] by the strength of the new CF tubing but deterred by the cost.
Geoff I’ve camped on Dartmoor in a heavy winter and also ditto the Cairngorms. Where Roger and I operate in winter is much worse most of the time, rogers AoO more so than Falls Creek and the High Plains but Bogong is worse than Kossie sometimes.
Hence our mutual interest in you getting it strong as well as light weightJun 16, 2017 at 7:36 pm #3473729
If Bogong gets worse than Kossie – that’s bad.
Betts Camp (near Mt Kossie) wind speed record is 243 kph. We have literally crawled across that gap.
Try https://backpackinglight.com/forums/topic/83877/ for further comments.
RogerJun 16, 2017 at 7:36 pm #3473730
I doubt a metre long each, an Easton 90degree joiner from TPT and a made up 650mm CF wand would give plenty of room at the foot end with clearance for the inner tent. assuming a decent hooded vent at each end then the low to high ventilation would help with condensation issues too.
In an aproximate equilateral triangle I dont think 500mm sections are quite long enough
I’m surprised the the TPT page doesn’t give the nominal weight for each item listed thoJun 16, 2017 at 7:39 pm #3473731
a made up 650mm CF wand would give plenty of room at the foot end with clearance for the inner tent.
Possibly: I was being a bit more generous. For those winter conditions you want a good 80 mm gap between inner and outer imho.
CheersJun 17, 2017 at 4:06 am #3473752
Well, if you’re thinking of handling the kind of snow dumps you’ll see in the NSW winter, your priority is obviously going to be strength without compromise or you might not walk out of there. Roger’s Gothic Arch seems to give unmatched strength to weight in those conditions if you’re not carrying trekking poles.
My own priorities are a bit different – a 3.5 season trekking pole design with the ability to handle big wind and a bit of unseasonal snow. Or a UK winter in a sheltered spot, where as you say we rarely get scary snow. I want the simplest, lightest solution that can manage this. Space isn’t a great priority provided I have room for sitting up – I do want a tent rather than a coffin-like bivy.
The front is pretty much settled, I think. Two trekking poles in sleeves, and a Phortress-style 4-panel front porch giving excellent flexibility for venting. Roger – when I talk about pegging down the edges of the fly, it’s mainly the porch I’m thinking of.
For the side panel, I’m still minded to go with the wing guys – simple and proven, and surely strong enough for my design goals. For a specialised winter tent, the additional arch is a great suggestion, and something I might build at some point. But I do feel it would be overkill for this application.
So as you’ve spotted, my final structural decision is how to support the rear. My choices are a single vertical pole like the Stealth 1, an A-frame, or a gothic arch. Now the rear seam is only 850 mm, so the gothic arch seems like over-engineering, even if I was confident I could build the thing. I’m minded to go with a sleeved A-frame as each pole in Fibraplex or similar would only weigh 20 grams, and it should improve the stretch on the side panels compared to the single pole. For such a short length, I can’t see that strength would be an issue for a straight pole.
And that pretty much gives me my design. I’ve ended up with something conventional, but there’s probably a reason why so many designers over so many decades have converged on similar solutions for a stormworthy A-frame. We haven’t come up with anything that is obviously superior at the same level of weight and simplicity.Jun 17, 2017 at 5:47 am #3473754
All points understood.
Then the only thing left is to demand PHOTOS! We want PHOTOS!
CheersJun 18, 2017 at 11:16 pm #3473952
Nick GatelBPL Member
@ngatelLocale: Southern California
Great to see you back on the project. Its been an interesting thread and am looking forward to your solution.Jun 19, 2017 at 2:51 pm #3474080
Rene RavenelBPL Member
Note my comments in the first post about size at the foot and space/material efficiency (SketchUp model towards the bottom). It beats a triangle. It does have a flat top which would accumulate snow, but it could be skewed to a trapezoid to minimize this. And it sounds like that’s not one of your prime concerns anyway.
Looking forward to your final product!Jun 20, 2017 at 6:49 pm #3474361
I did consider a hoop for the rear support – your crossed pole arrangement is a new idea to me.
As you say, it would provide more space with a minimal weight penalty.
But I have concerns about how it would impact the performance of the side panels. The advantage of the A-frame at the back is the ability to apply tension directly along the ridge seam and across the side panels, which I suspect will help the pitch. The transition from sharp peak at the front to a rounded or flat peak at the rear creates a much more complex shape that might be significantly more difficult to tension.
With your tarp, you wrote that you had an issue with tension, and the square shape of the old ConTrail foot end led to a large flat area at the top of the tarp which looked vulnerable even to moderate snow (and even to pooling water?). It’s interesting to note that in the ProTrail that replaced it, TarpTent reverted to a V shaped (single poled) rear.
My current design has plenty space at the rear to keep my bag off the tarp, so I think it’s unlikely that I’ll risk compromising the stability of the pitch to add extra space. An interesting suggestion, though, so I’ll sleep on it…Jun 21, 2017 at 2:54 am #3474374
Rene RavenelBPL Member
Fair point on tensioning. It would indeed take some iteration to iron that out. I think seams from the upper foot corners to the apex at the head would do it. But that’s more time, complexity and weight to seal it.Jun 27, 2017 at 1:02 am #3475655
Easton 90/145 degree arch connector
But thinking back to my experiences with my ex-wifes tapered Vango Force Ten Mk 2 I don’t remember ever being worried by thoughts of the side panels needing any more than the single side guy and this was without the heavy ridge pole.Jul 3, 2017 at 5:21 pm #3476882
Just a note on the Gothic arch centre poles
Sierra designs used it in the Aireflex tentJul 4, 2017 at 5:19 am #3476944
Bob MoulderBPL Member
@bobmny10562Locale: Westchester County, NY
That photo does not give me ‘the warm fuzzies” when contemplating how the Aireflex would fare in truly hideous weather. :^/Jul 5, 2017 at 11:08 am #3477075
Nick GatelBPL Member
@ngatelLocale: Southern California
Here is a video Peter Vacco made of his recent 6 week section hike across Canada above the arctic circle on the sea ice of the Northwest Passage. Peter posts here occassionally. I am not familiar with Hilleberg tents, but I think he uses an Atko? Check out the stakes and a single arch!
He was dealing with temps below -20F without compensating for lots of wind. Here is a YouTube Peter created about his trip.
A few of us BPL folks were getting SPOT messages from Peter. I kept everyone on the email list informed of progress creating a map with each SPOT message. You can read about in this blog post.
Also, here are a couple articles about Peter in case anyone wants to know more about his “qualifications.”Jul 5, 2017 at 4:28 pm #3477131
Yeah, 100% stakes matter. Getting them in place in the evening, having them hold overnight, and getting them out in the morning. Imho, titanium beats the hell out of aluminium for these conditions. See our MYOG articles on snow stakes at
Not so sure about the single arch bit myself, but if it worked for him – it worked. I see the ClamCleats also worked fine on his guy ropes.
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