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StenLight S7 Review

The regularly scheduled Webster System survey trip took place this Saturday, 20050917. The Webster System is a hostile cave, very big, dark, wet, and demanding. It’s a great place to have a good, bright light!

Mark Phillips, Pat Mudd, and me met at the Webster Post Office at 0800CST and quickly made our way over to the cave entrance. Our goal for the day was to continue and hopefully finish the Marathon Lake survey. This lake contains chest deep water pretty much the whole way. I would also be testing a new lighting system on this trip, a StenLight S7 high powered LED lamp. I had received one just a day before from Inner Mountain Outfitters . The Webster System, with all its huge trunk passage and light eating mud and water, would be the perfect proving ground. The following is a combination trip report and tech report.

Being somewhat of a techno head, I am always cognizant of new caving gear hitting the market. I'll never forget the first real caving light I ever owned: a Premier carbide lamp my Mom bought me from the Speleoshoppe way back in 1982. I can still recall firing it up, smelling the acetylene, taking it apart, cleaning it...lovingly. Funny how things can come full circle! Today, I am especially interested in the new breed of LED lights. After starting off with the Premier, I soon migrated to the Koehler Wheat lamp, which became to me the standard caving candle. It was not without fault, however, and the lead acid battery was the weakness. I also invested in the Speleotechnics FX series of lamps, and currently still own an FX2, FX2 dual, and FX5. Nothing beats carbide for a nice wide, diffuse lighting if you ask me. LED modules like those made by Gemini and Petzl come close to reproducing the carbide effect. If only there was a light that had both the properties of a well focus Wheat lamp and the softness of a high fired Petzl ceiling burner (and its aroma)…

For the past year or so I had been looking intently at the Speleotechnics NOVA 5 five watt LED light. Then came along the improved NOVA 3 featuring a Luxeon three-watt driver. The version I sought (a corded model for fixing to a belt battery) turned out to be vaporware. Enter the StenLight…

I made the drip line at around 0847. Little rivers of anticipation ran down my wetsuit inseam as I kicked those double-barreled StenLight 3 watt Luxeon LED's into life, and left my experience with all other cave lights behind me. Rather than allow my eyes to dark adapt to the cave environment, I boosted the Sten straight into Turbo mode. Wow. The output of the Sten reminded me of a video light. Bright, broad, having excellent color temperature, and very reaching. I didn’t burn it on Turbo long for fear of wearing down the battery too soon or causing overheating (it is a misnomer that LED's don't get hot--they do!). These fears were unfounded I would later discover.

Making lake at around 0900, I had an opportunity to see what the Sten was capable of. The passage here is only about 8 feet high, but is over 50 feet wide. I was able to pierce the darkness for several hundred feet. During this initial experience, I discovered the only shortcoming I was able to find in the Sten. The StenLights dual lamps are driven by highly sophisticated electronics and power plants in order to efficiently run the LED’s. Heck, they're even thermally regulated. Technical data can be perused at .

Dual LED’s serve two purposes: one has a wide angle beam pattern and the second is narrower for “throw”. They are aligned to give a multi purpose spread pattern. The narrowe-angle beam, however, presents an odd artifaction: a dark donut. In fact, at first I thought it was a shadow cast by my helmet brim. I soon discovered it was from the left or wide-angle beam. It seemed to fall right at my feet, and was obvious when looking at a low ceiling or solid colored ceiling or mudbank. I immediately started thinking about replacing the spot collimator with a matching wide beam to get rid of it (this is a modification easily made by the owner, and additional collimators are availble from ).

Pat and Mark soon joined me at the first lake and we proceeded down the passage towards the back section of the cave. We had over 10,000 feet of main trunk to cover before we could start mapping. Soon we were in classic Webster trunk passage: 30 feet wide and over 40 feet high. Even with its low albedo, the StenLight was able to fully illuminate this massive trunk passage. Even on “high”, it was able to show passage character for hundreds of feet. It was truly impressive. On Turbo, it was a sight to behold. I could easily make out the entire trunk! By this time I had completely forgotten about the strange halo observed earlier. I continued to play with my new light, delving into various power modes depending on passage conditions. The magnetic switch used to control the four different power modes was extremely easy to adjust with a wetsuit glove. It was very tactile with wide separation between modes. Splendid.

Within one hour we had covered 6000 feet of muddy and deep-water trunk, and took ten for a break at Parks Avenue. The water was markedly down over our trip last weekend, and the Mulu sump was likely open. After resting, we continued deeper in to the Middle Section of the cave. After about another hour of fast paced caving, we made it to B-119, the last Marathon Lake station. Marathon Lake is the longest lake of the system at over 1700 feet. We had previously mapped about 700 feet of it. Here and beyond, the Webster Cave System becomes truly unbelievable. For thousands of feet, the main trunk winds its way around corner after corner reaching huge dimensions. In places, the passage is over 40 feet wide and nearly that high, with neck deep water wall to wall.

We started our mapping with Mark on notes, Pat on lead tape; I took instruments. It was somewhat slow going at first as Mark familiarized himself with the sketching of such a huge passage. Within four hours we had charted over 1100 feet of cave. Along the way, we set permanent stations at the mouth of Bundy Canyon and the Necronom lead. I had not seen Bundy Canyon in over 15 years, and its appearance seemed to have changed (perhaps owing to mudbank erosion). It was blowing a strong breeze. I also noted a high upper level lead out in Webster Avenue nearby, likely associated with the canyon lead.

By this time I was becoming elated with the StenLight. It had proved to be the brightest light I had ever owned. Heck, even on low it was almost too bright to cast at your lap when having a snack. It cut through the fog and darkness very effectively. My adaptation of the StenLight S7 system to my helmet was a bit unusual. The 7.2 volt Lithium ion battery is meant to be mounted to the back of the helmet. That’s where my Petzl Duo sits and I decided to keep this light attached as a backup. So, I opted to mount the StenLight battery inside my helmet. I know, I know, “that space is there for a reason”. But the battery fits there perfectly. I cut the supplied Velcro in half and positioned two pieces by the Ecrin vent holes. The battery neatly “pops” into place. The added weight is counterbalanced by my Duo headlamp, which I have mounted to the right of center.

We ended the survey for the day at Necronom, found 11,470 feet from the Main entrance. During the last part of the survey a few strange things happened. First, we all started hearing odd sounds coming from all around us. We eventually concluded this had to be the sounds of traffic passing overhead. This part of Webster Avenue lay beneath KY333. Then, it got really weird.

Suddenly, I heard what sounded like flowing water coming at us. No rain had been forecast, so it seemed a bit odd. Suddenly, it started to sound like movement in the water, then I saw light. It was a caver paddling around the corner in a kayak! Never in all my years caving here had I ever encountered another caver (other than who was with me). “Chris Anderson?” he called out. He knew me but I didn’t know him! It was Jeff Gillette from Western Kentucky come to join the trip. He was aware of our survey trip from the website , but wasn’t able to join us early.

After wrapping up the survey, we stopped for lunch and a little token exploration in Necronom. The total for the survey now stands at about 17,667 feet. We turned for the entrance at 3:30 but stopped for one photograph of Marathon Lake:

We made it back to the daylight at 5:30 PM. I burned the StenLight on Turbo for the last half-hour of the trip, and it continued to burn very bright well after getting out. I’d say I got over ten hours of lighting out of just one battery: 60% high, 20% Turbo, and the rest medium and low. Even when it finally stuck on low, it was pretty bright. I was impressed when, thinking I had it on Turbo, it was really just on high. The odd donut artifact I spoke of earlier ceased to be a problem. I think I just got used to it. On the way out it never even occurred to me.

I also did some unscientific tests regarding compass deflection with the Sten. Some had expressed concern over the magnetic switch mechanism it uses. I got noticeable deflection of my Suunto when the Sten was brought to within about fourteen inches horizontally! When brought in at a 45 degree angle, however, it had to be within about seven inches before you could see the card start to move. Seems about the same for my other helmet mounted lights.

Well, it was a great trip. This section of Webster Cave is very beautiful, and remote! I reckon soon we’ll be spending three or four hours just getting to where we need to start mapping. The next scheduled trip is October 15th.

Now to sum up my first experience with the StenLight: wonderful! I wanted a very bright, well made caving light. Although I was prepared to keep my belt mounted “brick” battery to power it, I must admit having it all self contained in the helmet is really nice. The milled aluminum housing, heavy duty wiring, and compact Lithium ion power source all help to make the Sten as close to “perfect cave light” as I have ever used. Sure, it is expensive at over $300 for the kit, but I plan on selling off the rest of my other cave lights pretty soon anyway…

This new cave light is perhaps the greatest advancement since the taming of fire itself!

Need a second StenLight S7 opinion?

C.G. Anderson
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5 degree and 25 degree collimator beam pattern
5 degree and 25 degree collimator beam pattern
15 degree and 15 degree collimator beam pattern
15 degree and 15 degree collimator beam pattern
15 degree and 25 degree collimator beam pattern
15 degree and 25 degree collimator beam pattern
Cracked Sten Cover Window
Cracked Sten Cover Window
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