Internal guys in a Nallo 2

[Derek Goffin]

I have been making adjustments to our Nallo 2 for a trip to the Andes and Patagonia where high winds are expected. I just made internal guys for the Nallo. I am impressed by how much stiffer the tent can be. The guys are thin webbing temporarily fitted with toggles across the hoops. They only weigh about 10 grams the pair.

The guys hardly get in the way. They go from the top guy point on each hoop across the tent to the other top guy point. The front guy does not even interfere with the inner it goes at about sitting face height just outside the inner door. It is easy to duck under it to get out. The back is a little more difficult. I have permanently fitted short webbing from the correct inner toggles horizontally across to the inner and added webbing loops on the inside of the inner at those points. In a storm a 31" tape is toggled across the 2 loops. It is placed well above the ankles and feet of people in sleeping bags.

Advice from Hilleberg was tension the Nallo strongly front to back but do not tension the pole guys, just snug them up. If you over tension these pole guys you distort the hoops.

With these inner guys in place you can get a good bit more tension on the pole guys as the inner guy stops the distortion of the hoops. Without internal guys the up wind side of a tent hoop is supported by the upwind guy, but the hoop is still pushed over at the top by the wind, increasing the bend in the downwind side of the hoop. The suction on the downwind side has only the stiffness of the pole to resist it. The downwind guy is loose and useless. The pole is likely to break. With an internal guy and tighter pole guys the downwind side of the hoop is supported by the internal guy and the upwind side does not get pushed over so much because of the tighter guys.
Whether a tunnel pole breaks at the point of bending stress caused by the upwind guy or at the point of maximum curvature of wind distortion at the downwind side I do not know but I think the internal guy will help both cases.

Tonight high winds are expected in England the night for a test!

I may separate the top pole guy from the lower one as the lower one does not get an internal guy to resist the tension.

I recommend Nallo users who want more security in high winds to experiment. Tie a bit of string across the front hoop at top guy height and see how much stiffer the front hoop becomes.

[Stuart Murphy]

I don't have a Nallo, but am interested in the general concept. Are you able to post pics or even a test video?

Note that I think some manufacturers don't claim this makes the tent stronger (Stephenson do think it helps and so does Roger Caffin), but it certainly could make it more stable. I wonder if it does increase strength (i.e. the force needed to break or permanently bend poles by wind loading).

There is also a chance I suppose it could make things worse (eg. by not allowing the tent to lay over in strong side gusts and promoting failure in either the poles or other things like guy points/fabric).

Anyway interested in any tests you do.

Cheers
Stuart

[Derek Goffin]

Hi Stuart,
It does seem to me that it is bound to help the pole, but it might well put stress on other parts that were not designed to take it. I cant imagine what part, but that's the problem. I have added stretch limited strong elastics to these top guys so in a gust the fabric may be helped by a few inches of give.
I was going to reply to Petra Hilleberg who sent me an email some months ago and ask what Hilleberg thought

[Stuart Murphy]

Hi Derek,

Trouble is the manufacturer may not have done the testing for the type of thing you are trying and even if they have may be reluctant to give "advice" or data that is somewhat subjective. Hilleberg won't even quote wind-speeds their tents will take (not even for artificial environments like a wind tunnel). They are certainly not alone in this, so I'm not singling them out.

I say bring in an international standard so the consumer knows what they are buying… a most frustrating situation as things currently are. You can't even infer the performance of a "design" eg. all tunnels are not created equal – even if they look similar in that they have 2 hoops. If you look on Outdoor Magazin similar designs can have greatly different wind values they flattened or failed at.

I guess all you can do is test it yourself. Note that age/UV damage are significant variables too. So the test you do today is not valid after X hours of exposure to sun (and chemicals like sunscreen?) You could have the strongest tent in the world ready to shred from UV exposure. So condition of tent,design and pitch (including orientation and location) are all important.

Are you able to post some pics of how you did the mods?

I was thinking about ordering a thick pole for my tent (say 13mm or 16mm). Lighter than double poling but I'm not an engineer/material scientist (eg. is 1x16mm pole stronger than 2x8mm but more prone to breaking? I have no idea) and then what is the impact on the rest of the structure of the stiffer poles as you say?

I hate that there is no standard and so manufacturers get to claim whatever they want based on tests / experiences you no little about because they differed from their competitors.

I guess at the end of the day we are therefore reliant on anecdotal evidence of consumers (itself problematic), which brings me back to why isn't there a standard for these products that manufacturers expect consumers to pay a lot of money for.

Anyway, plse keep us updated with your experiment.

Cheers
Stuart

[Derek Goffin]

Hi Stuart,
I am hoping to test my Nallo in a gale tonight so you will hear. The tent is 5 years old but has not been used that much and was hardly ever left up during the day. You do not get any sun in Scotland even in the day! I hope the UV degradation is low.
As far as double poles or one stiffer pole goes I would go with 2 thinner ones on the bundle of reeds theory. The Stephensons warmlite has a large diameter pole but it is prebent. A large diameter straight pole bent into a hoop sounds as if it is close to failure already.
A larger diameter pole of the same weight will have thinner walls. It will be stiffer and stronger but will break at a larger bend radius than the smaller pole. It will go without warning.

[Stuart Murphy]

There aren't many options for buying after market aluminium poles that I am aware of. I think http://www.polesforyou.com can pre-bend as needed. Maybe that then becomes an attractive weight saving (compared with double-poling) and maybe as good so long as you treat the pole with care (eg. don't dent it)?

Here's hoping for some big wind for your test.

[Derek Goffin]

We went up Pendle hill last night to camp. We have no anerometer but predicted Met office maximum winds for 400m in the Dales and Peak district was 75mph. Pendle is over 600m. Mwis predicted higher

We camped on the flat top just upwind of the summit. We could stand and walk with difficulty except in gusts. Putting the tent up was difficult, the soil was poor and rock ridden. I have enough confidence in these internal guys that although we had double poles available we did not use more than one set. We got the tent up, with the wind unfortunately just off straight down the tent. The pegs were pulling out in the wind so we loaded the pegs with rocks. We have set the tent up with rock loops so we could also take the strain off the pegs by putting rocks in the loops. When everything was set and the front points tensioned the tent felt good but it was flogging and shaking continuously. The internal guys were tensioning and slackening with gusts, but mostly tensioned. I cooked in the porch. The front internal guy did not get in the way too much. You ducked under it to get in and outThe rear guy did not cause any problem until, feet to the door, I lay back to pull waterproof trousers on then I had to get under the guy to lay down. In normal use it was not a problem.

The tent survived the night, with no damage that I have noticed. The wind reduced a little during the night. The problem seemed to be the pegging not the poles or the fabric.

Sleep was intermittent because of the noise.

I do not think there was any gusts from above, just because of where we were in maximum wind, as clean as it comes. My suspicion is downward gusts happen behind rocks or on lee slopes.

I think internal guys do a lot to keep the pole hoop in shape.

[Stuart R]

I hope you stopped for a pint at The Ship. Pendle Witches Brew was my favourite…

[Stuart Murphy]

Derek,

75mph is a lot of wind. So the wind was about 10 deg off axis… or…?

Do you think the bracing will help in cross winds? Is your setup like this:

http://www.outdoorlife4u.co.uk/Tents/Vango_Tempest_200_Tent/

or more like this:

http://www.flickr.com/photos/warmlite/4370801694/in/photostream

Stuart

[Derek Goffin]

Hi Stuart,
mine just go straight across from pole guy to pole guy ignoring the inner as much as possible.I want to get tension from the ground outside to the hoop, straight across the hoop to the other side and down to the ground again on the other side. As I see it that is a closed structure. If you look at a guyed television mast I am thinking of that. A compression mast with 3 guys each to a series of points up the mast to stop buckling. My tent has 2 guys one interior and one exterior to support the hoop. It does not need 3 because the fly supports the hoop too.
Both the pictures you show are diagonal braces. The warmlite does not have any exterior pole guys to connect anyway, which to me is a mistake. The vango has put the guys up to the peak and down again to avoid them getting in the way. My solution is to make them removeable and they are only in the way in storms when I could not care less as long as the tent stays up! The Vango internal guys do not seem to connect to the external hoop guys, the internal ones are lower down the pole. The problem with this: if you tension the external guys you distort the hoop. My solution the internal guy resists the distortion if you tension the external guys.
Although 75mph was predicted as a maximum, my feeling was that we did not experience 75mph. I would imagine you could not stand and would have to crawl at 75mph. Without an anaerometer I do not know

[Roger Caffin]

Hi Derek

Yeah, internal guys are the go on some tents. If you read "When Things Go Wrong" you will see I had internal guys on my 4-pole double-skin winter tunnel tent while the wind outside was gusting over 100 kph, and the tent was fine. Er – until the morning when I lost 6 out of 8 guys …

Recently in Europe (Slovenia, under Mt Vogel) we camped in the WRONG place with my UL 3-pole single skin summer tunnel and had even worse winds in gusts (after the tent was pitched). In excess of 150 kph would be a good estimate. My excuse is that it was serious karst country and there was almost nowhere to pitch a tent. The inner guys held – just! The tent bucked like mad though, and it was not clear that the guys would hold. We pulled the tent down (an interesting exercise in a storm) and retreated to some shelter.

> The pegs were pulling out in the wind so we loaded the pegs with rocks.
The security of the pegs is the critical bit. If you lose the guys, big trouble. Even with the tent bucking like mad the carbon fibre poles and silnylon fabric were holding.

> My suspicion is downward gusts happen behind rocks or on lee slopes.
Don't they ever!!!!!!!
Internal guys can help reinforce against that too.

Cheers

[David Adair]

This has been an interesting discussion. I think what you are doing makes sense and I am not seeing a downside.

"I may separate the top pole guy from the lower one as the lower one does not get an internal guy to resist the tension."

One advantage to Hilleberg's approach of using a single guyline with two attachment points is the wind resisting force provided by the guyline is distributed over a longer length of pole. I can also see that in a variable wind loading it would allow for greater displacement of the top attachment point which would moderate the critical stress concentrations in the pole existing at that particular point. All good so far. For this to occur, however, the stake must be functioning like a "pully". Which is again fine as long as the line doesn't tend to "saw" itself through on the stake.

So I suspect it is worth maintaining the single line approach if you can find a stake attachment that allows the line to pass freely and does not saw. Perhaps some decent mini-biners or some kind of ring?. I don't see the additional pre-tensioning acting on the lower attachment point as a likely problem as long as the localized pole distortion is not unreasonable.

Is my logic off on this?

Appreciate your ideas and experimentation and look forward to hearing more on what you learn in the field.

Oh and forgive me for stating the obvious but a lot of tension on the pole end adjusters should help minimize the wind deflection of the poles as well.

[Roger Caffin]

Think I agree with most of what David Adair is saying.
My Spectra guys (in When Things Go Wrong) did saw themselves apart on the sharp edges of the titanium snow stakes – since fixed.
I do use a single guy attached at two points on the tent as described, and it has not been a problem when tensioned. There does not seem to be much pulley action in practice as the wind loading hits both upper and lower attachment points.

Cheers

[Derek Goffin]

That is all useful stuff and thank you. Before the internal guys we tested the same tent ontop of a Munro in a gale and nearly lost the tent by the sawing action of the double guy. 2 of these double guys were down to a few white dyneema threads only by mormimg with all the red nylon gone. All the single guys were fine. Our first attempt to solve that was PVC sleeve but it does not stay inplace and by last week we had got to a hard black nylon ring to put the peg though, which as you say acts as a pulley. We had no trouble with abrasion of the guys. This could be down to the nylon rings or another Idea I had. I added double 3mm elastics at the top point only. This stretch was limited by a webbing strap. The higher point is about twice as far from the pivot point of the ground as the lower point so as the pole moves the sawing action had been obvious. With the strong elastic the top point moves a certain amount without the guy and I could not see sawing.
You are probably right I did not see any gross distortion of the lower point due to pretensioning. The pole is after all only attached to the guy point through a floppy sleeve and the fly was pulling at the lower point but not enough to move the pole.
Advice has been in the Andes it is so rocky that pegs are no use and you must rely on rocks to hold the tent guys. Thus we have rock loops on all guys. After that experience on Pendle the first thing you do when setting up your tent in a gale is gather a large pile of suitable rocks!

Yes David I pulled the pole tensioners as tight as they would go as Hilleberg advises. I also put lots of tension front to back, pulling the hoops forward at the top. I had lomg guys on the ventilation hood loops too which helped pull the top of the hoops forward. This all helps tension the back of the tent which is taking the worst of the wind.

[Diplomatic Mike]

Just a comment on the windspeeds Derek.
That same night, mwis was forecasting 110 mph winds over the Scottish hills. The storm wasn't as bad as expected, and the highest gust was measured at 78 mph.
You may want to downthink the actual windspeeds you encountered.
I'm interested in this discussion, as i've had someone make external guys for my Stephensons 2R. I didn't want internal guys, but i may change my mind.

[Roger Caffin]

> I also put lots of tension front to back, pulling the hoops forward at the top. I
> had lomg guys on the ventilation hood loops too which helped pull the top of the
> hoops forward. This all helps tension the back of the tent which is taking the
> worst of the wind.
Yes indeed. The tension from end to end is very important, which means the windward end guys are ultra-critical. Big rocks there? Oh yeah! I have also used solid sticks (>30 mm) through the two end anchors with rocks piled right along the whole length of the stick. More mass. Also rocks on the ground for the stick to lean against.

The extra end guys at the windward end are not common, even on tunnel tents, but they are also very valuable.

The sawing action definitely needs to be managed. The nylon rings sound like a good idea. I used some loops or hooks made of 2.4 mm Ti wire: same idea but stronger. I have had nylon saw through when a guy slipped under load.

Cheers

[David Adair]

Your experience with the hard black nylon rings is promising. I would guess the difficult part is finding a ring with the right specifications. Seems like a 1 inch diameter ring with a 1/4-5/16 cross section would be about ideal. Although the right synthetic might ultimately be the best choice, aluminum at least has the advantage of being a known quantity. As Rodger suggests, we don't want to mitigate one potential failure mode by adding another (ie like an inconvenient propensity to shatter at 20 below).

Is it possible a loop of 5mm rope of say 6 inches in diameter could serve the same function as the ring? Or are the ropes likely to abrade through one another?

I do like the ring idea as it seems simple to drive a stake through or alternately attach a snow/rock bag.

btw: Where ever did you find those hard black nylon rings?

Thanks for sharing your investigations.

[Stuart Murphy]

Would it be worth just cutting the double guy rope at the apex?

How much load is distributed between the 2 guy point in practice by virtue of the sawing? Sounds like you guys are suggesting "not much"?

Do you think the manufacturers are doing it because the design is better or to simplify the guying process for users (who would have greater scope to misuse independent points)?

Two separate guy lines would avoid the sawing issue altogether and give you the option of two independent peg points which could help for some ground conditions. You could always just use the one peg for the two guys as well.

[Derek Goffin]

I got the nylon rings from Extrem textil in Germany but they are available from yacht chandlers too. Does nylon cope with cold? surely we would have more problems with nylon fabric if it didnt.
Stuart Separating the guys was my suggestion that started this part of the discussion. The Nallo as supplied did saw guys nearly to destruction but something I have done has solved the sawing problem. Double guys are good if the problem is solved

[Roger Caffin]

> Do you think the manufacturers are doing it because the design is better or to
> simplify the guying process for users

I was using two separate guys on the tents I made but switched to a single guy rope between the two. The reason is that it makes major adjustments to the length of the guys very easy.

The red is the tent pole.
The green is the stake.
The blue is the double guy.
The purple is a single LineLok from ClamCleats.

If you imagine this in a storm you can see that the lower attachment point is not going to move very much, so there won't be too much sawing action. But tightening the guy rope is very easy as the adjustment is at a convenient height.

Cheers

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