Tunnel Tents Tutorial and State of the Market Report – Part 2: Details and Commercial Models

I can think of a few different ways you could remove a curved mandrel. Wax or polymer that you could melt out as suggested already; some sort of inflatable tube; a material that has a sufficiently different coefficient of thermal expansion from carbon, (perhaps aluminium?) that could be heated and then cooled (or just cooled). Basically anything that can be made even just a little bit smaller so it'll slide out.

The more I think about it the more I think an inflatable bladder would work well. At high enough pressure it would be solid enough to form around and then you could just deflate it and remove it.

The author expresses concern about the Stephenson Tent having only one rear stake. We have two tents, 2R for high cold climbs and the 2X for light backpacks. Both have side window ventilation. The 2X weighs just over 2 lbs.

Our Stephenson Tents have been used more than a hundred times over the past 30 years on many of the highest mountains and never had a pullout of the rear stake. It is a case of using the right stake for the job. Even with two stakes, if one comes out a tent will not be stable.

Normally, we use an eight inch tubular aluminum stake. It holds well in everything but rock and snow. On high altitiude climbs in snow, we often use an ice axe. On Aconcagua we used nothing but large rocks (over 70 lbs.) for the entire two week trip. We have experieinced winds up to 85 mph and snow storms up to 6 inches in our Stephenson tents without difficulties.

During many base camp discussions, others have expressed that they had heard that the Stephenson does not have enough guy-outs, stake down points, it doesn't offer enough ventilation, etc. All these comments have seemingly come from those who have never used a Stephenson tent.

Clearly you have a good understanding of tents. I hope no one takes my comments as critism of other tents discussed in the article. I can only speak of tents that I have used.

I was concerned about the sewing of the Stephenson tent as well when I first bought my 2R which was in the 70s. I have always tried my best to treat ultralight weight gear with great caution, and I never have had any seam failures with either tent in more than 30 years of hard use. My son also uses a 2X with no seam problems.

Regarding, a vestibule, we were always able to cook in the front part of the tent that Stephenson refers to as an attached vestibule. When weather was better, we cooked just outside the entrance or with the door clipped open. On miserable nights we risked cooking inside with the door closed. Cooking inside is always a risk. People have lost their tent in seconds due to fire. Check out the Wilcox disaster on Denali in 1967.

Room is another issue. The square footages of floor area for the Stephenson tents are higher than most tents on the market. We often slept three in the 2R when weight was a major issue (about 1 lb. per person). The 2X tends to get damper on the inside due to condensation than the double layer 2R so we always limited it to one or two people so we did not touch the sides.

The 2X tent is a bit lighter than the 2R because it does not have the liner. Also,on the 2X I use the smaller 3/8" main pole instead of the 5/8 " pole (saves about 3 oz.), a shorter version of the tent (saves a couple more oz), 2 titanium stakes in front and one 8" in the rear (another oz), and no stuff sack (two more oz). All in all for a tent that is so light and can withstand severe weather, I really like the Stephenson.

I purchased the 2X about 10 years ago. My son purchased his about 15 years ago. I did not notice much difference in construction quality of the 3 tents. All of the tents were hand made in the USA and looked like home made tents. I can not speak for todays quality.

I pulled my tents out and took a look at them today. In general, the workmanship is better with straighter stitching than the photo in the minis. However, mine don't look like works of art. Maybe, by experience, they are art that works.

Stephenson has a long writeup on his site about different types of stitching and their inherent strengths. I can say that Warmlite has been very helpful with any questions and they are supposedly good with guarantees. I think that good seam sealing also helps keep threads from coming loose or tearing the fabric.

I have poked holes in my fabric, damaged the end of a pole and worn through some of the fabric where the pole inserts into the sleeve. All of these things were repaired at home with hand tools, urethane or silicone, and stitching. It is good to carry some extra fabric, thread, silicone for sil-nylon, and a muti-tool. I have never had anything happen during a trip that prevented me from setting up the tent properly.

I hope you don't think I am sounding like a saleman for Stephenson, but they make a 3R model that has sitting room at both ends and more ventilation. It is massive inside with some additional weight. On many trips and sometimes sitting out long storms, we have never complained about sitting up in the 2X or 2R unless there was three of us.

Good question, but …

You are trying to replace a steel mandrel which has CF cloth wound aroung it tightly and then it is wrapped very tightly with PE tape before thermal curing. I dare say a bike tube might withstand the compression if inflated hard, but what diameter would it be when inflated hard withough the constraint of a tyre? And how do you keep the exact curvature you want for the specs? Remembering all along that you are trying to make a tube about 8-9 mm OD.

I'll pass on the problem of finding such a curved tube to start with.

Cheers

Well, as I said, on second thought I don't think a pressurised tube would be that effective, but you guys both seem to have missed the second part of my post about the Plastimake stuff, which has a glass transition temperature of 60 degrees C. It would be relatively easy to use this stuff to wrap and set carbon fiber around, and then it would melt out at less than 100 C – a lost wax process I guess but even more effective than using wax?

Hi James

> This is used for fishing rods where a taper is desired.
Dunno about CF fishing rods, but I do know that many fibreglass rods start parallel and are ground down into a taper. Easy to do on a production basis.

Lost wax for curved CF poles? I suspect the wax, or Plastimake, will melt during the epoxy curing process. Um – well before the curing has got very far. Tricky.

Cheers

Yeah, there are lots of epoxies out there. I was thinking of quick process stuff that requires *some* heat, though. WIthout heat you probably couldn't create a continuous process. Once it is fairly well set, you could cut it and increase the heat melting the mandrel out and finishing the cure. Anyway…just thinking out loud.
As roger says, tricky, but doable.

Roger,
No, Fishing poles are NOT made by grinding them. (Well maybe old ones were.) They use quite fine mandrels, wrapped.Tips are often solid, though.

It seems to me that making a thin hollow bent CF tube requires a flexible Stainless steel wire inserted into flexible plastic tubing. The tubing ideally needs to be slightly stretched (ie increased in diameter), by the wire. Once the CF is set, removing the wire will allow the tube to shrink to its original size. Further, pulling one end of the tube causes it to shrink still further allowing it to be removed.
A few points:-The tubing needs to be sprayed with a release compound, I am trying silicon lubricant.
The curve of the wire/tubing can be set by clamping each end the required distance apart and allowing it to hang free giving space to wrap the CF around it. Very tight bends not practical.
Strongest results would be to use two layers of tape wound diagonally in reverse directions.

I am trying this out and will (hopefully) advise results. :-

Congratulations on finding a way to bring these to market !

Can't wait to see some at the 2015 GGG.