Storm-proofing the Side Panel on a lightweight A Frame Design

[Edward John M]

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 weight

[Geoff Caplan]

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.

[Roger Caffin]

Hi Geoff

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.

Cheers

[Edward John M]

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 tent

[Edward John M]

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 configuration

[Roger Caffin]

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.

Cheers

[Edward John M]

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 weight

[Roger Caffin]

Hi Ed

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.

Cheers
Roger

[Edward John M]

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 tho

[Roger Caffin]

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.

Cheers

[Geoff Caplan]

Hi guys

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.

 

[Roger Caffin]

All points understood.
Then the only thing left is to demand PHOTOS! We want PHOTOS!

Cheers

[Nick Gatel]

Geoff,

Great to see you back on the project. Its been an interesting thread and am looking forward to your solution.

[R]

https://backpackinglight.com/forums/topic/box-foot-tarp/

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!

[Geoff Caplan]

Hi Rene

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…

[R]

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.

[Edward John M]

Easton 90/145 degree arch connector

http://tentpoletechnologies.com/?page_id=671

http://tentpoletechnologies.com/?page_id=631

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.

 

[Edward John M]

Just a note on the Gothic arch centre poles

Sierra designs used it in the Aireflex tent

[Bob Moulder]

That photo does not give me ‘the warm fuzzies” when contemplating how the Aireflex would fare in truly hideous weather.    :^/

 

[Nick Gatel]

STAKES!!!

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.

https://www.youtube.com/watch?v=BkGX_jvd6vg

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.”

2009 article

2017 article

[Roger Caffin]

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
https://backpackinglight.com/make_your_own_gear_titanium_snow_stakes/
https://backpackinglight.com/myog_ti_snow_stakes_part_2/

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.

Cheers

[Geoff Caplan]

Hi folks

There was so much kind help on this thread that I thought I’d report back on where I’ve ended up, for now at least. It might help someone else working through the same issues. As a reminder, I’m looking for a lightweight solution for high and exposed camping on multi-week treks in areas like Scotland, Scandinavia, the Western Alps and the Pyrenees – all vulnerable to sudden nasty wind storms at any time of year. I’ve been using a TrailStar + nest and was looking for something lighter with a smaller footprint that would use my trekking poles for support.

But what became clear is that there’s no simple, elegant solution to storm-proofing the A-Frame for a solo user. I was going to end up with a full mountain tent of complex design, including sleeves, 4 zips,  1 or 2 additional poles, fancy vents, and 14 pegs in storm mode. It would be bomber and well-vented but my gut was rebelling against all this weight and complexity. Solutions with a transverse ridge like the Tarptent Notch weren’t much better once you harden them for wind. The Aarn Pacer, for example, is strong but complex and too heavy for my usage at 1.4 kg.

I’ve had the TrailStar out again in winter and summer conditions and fallen back in love. I realised that my reservations were mainly with the over-engineered nest I’d been using rather than with the tarp itself, so I figured out a light, simple and zipless way to add a floor and bug protection.

For the tarp, the big advantages are failproof simplicity and unmatched wind-shedding. I can get it up in 2-3 minutes with 6 pegs in clement weather and 9 for a full storm rig. There’s masses of space for living and cooking – hell, you can have a party inside (quite literally). You can adapt the pitch in half a dozen ways to match the conditions and terrain. You can keep it open and vented in severe weather – there’s something special about lying safe and dry in your pit and watching all hell break loose around the nearby peaks. And you can drop the height and batten down all the sides to survive Armageddon.

But the MLD Sil version has a couple of disadvantages – the fabric can sag badly and because of its size it’s relatively heavy for a tarp, especially when wet. You can’t solve these issues with Cuben – the design works much better with some stretch in the fabric. So I looked at cloning it with the 1.1 oz RSBTR silpoly PU, which would address the weight and sag issues. A highly experienced industry designer has assured me the fabric should work, and that’s been confirmed by someone who’s made one. As an added attraction, there’s a rather pretty Marpat camo which will be more stealthy than my current grey version. Turns out I can bring it in for under 650g for tarp, bathtub and bug protection. The tarp needs 10 yards and would cost around $70 US. This is the same kind of weight as the popular $600 ZPacks Duplex. It’s a bit less livable because of the central pole but far more storm-worthy, not to mention far more wallet-friendly. For me, those are the right tradeoffs. To have truly bomber 3.5 season protection for 650 grams at around $100 all-in is pretty much unbeatable.

Plus it’s a trivially simple build – a few basic seams and you’re done. It’s a tarp, pure and simple, so a good project for a MYOG newbie.

That leaves the big footprint as an issue – well, you can’t have everything. But it’s not really that much bigger that a StratoSpire or a Duplex, especially when you take guys into account. And because it’s a tarp you can always improvise – it’s so big you can even pitch with rocks or tussocks inside on the other side of the pole and still have a livable space!  I wouldn’t take it on the AT – but then, I’d rather have root-canal treatment than walk the AT. I prefer open country where the footprint isn’t such a big deal. And by bonding on a few external tie-outs I can bodge a narrower pitch that would work OK for sheltered sites like woodland where the footprint is more of an issue.

So, I greatly enjoyed our nostalgic trip through the intricacies of A-Frame design. But now that I’ve solved the weight issue the simplicity, strength and elegance of Ron’s brilliant tarp have won out over the attractions of a smaller footprint.

[Nick Gatel]

I posted early in this thread, after sharing my old a-frame pictures, that my high wind shelter of choice is a silnylon Trailstar. Pure genius. Sagging material hasn’t been an issue in rain. I don’t use it is snow, I use a Scarp 1.

[R]

What are your thoughts on the shapes of a solo mid or hexamid? They both provide a living space similar to half a trail star (which is all one person really needs) with a smaller footprint and similar weather handling.

You arrive at something similar if you consider an asymmetric trail star – make the door side panels smaller and pitched steeper. I realize this would reduce the efficacy of the door. You could add a zipper and you’d end up with an asym penta-mid. If you take the door zip all the way up to the apex you can open it up as a flat tarp for more pitching options.

I don’t know if there would be a benefit to this over a solo or hex mid, but you might want to noodle on it a bit before committing to a custom clone of something you previously wanted to replace.

Also, don’t forget about Rockywoods’ 0.7osy (actually 0.8) silnylon.  It’s reported to have very little wet sag.  Available in unobtrusive ‘sky gray’ :)

[Geoff Caplan]

Hi Rene

Thanks for your thoughts – always worth listening to.

Mid design – room for innovation?

Mid design is a whole different subject – we probably shouldn’t go there!  I’ll see if there are other threads.

Long story short, MLD, Zpacks, Six Moons, TrampLite and others have all played with asymmetrical mids. I doubt there’s anything radically new to discover. My tentative conclusion is that you gain a smaller footprint, and in some designs a nicer living space. But you also get steeper walls to catch the wind, and much less coverage. Either you go for simplicity and accept that as-is like the MLD Cricket. Or to counter these issues you’re opening up a whole world of doors, panel support guys, vents etc and the simplicity is gone. Just look at the Hex or the TrampLite – very sophisticated. You also end up with a fixed-shape tent rather than a relatively flexible tarp.

You can’t say that one approach is better or worse than another – they’re all good shelters and it’s a question of priorities. I’m pretty convinced that the TrailStar is the most storm-proof, the most flexible, and the easiest for a first sewing project. It’s not the most livable, but I’ve got a hundred nights in it now and it’s perfectly bearable. And I do like the way you can keep it open is all weathers – something you lose if you go for a smaller footprint design.

You’re right – I should play around a bit more. But I’m pretty close to pulling the trigger on a TrailStar clone. It’s not a big project or a big outlay, I’ll learn a lot, and I’ll get something useful at the end.

And a last hurrah for the A-Frame

I haven’t completely abandoned the A-Frame though, but I’m returning to simplicity and sacrificing a bit of storm-worthiness. The idea would be similar to the MLD Patrol, but improving coverage by giving it a deeper beak and get access by sliding the beak up and down the front guy – an idea inspired by the Exped Vela which has a zipless porch that slides up and down the hooped pole. Something I could prototype pretty easily in silpoly. Unlike the TrailStar this would work in Cuben and would weigh under 300 grams, so with a lightweight bug nest it would be about as light and minimal as you can get with near-to-full coverage. And it’s a smallish footprint.

For really severe weather the idea is that instead of building something super-strong with a fixed shape like the Phoenix Phortress, you keep flexible and simply drop it to the ground  with a very low profile. Seems that the Patrol can survive pretty much anything with that pitch Not very comfortable but it won’t be needed very often, and you can feel macho while the storm rages outside :-)

There’s a triple-crowner who swears by his Patrol – but it’s obviously a bit of a minority approach as it hasn’t taken off like the TrailStar. Still, I fancy seeing how I would get on with such a minimal setup.

Here’s the Exped with it’s door slid up to the top of the pole:

[Author]

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