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[PSUBS-MAILIST] home-built strobe location beacon




Someone made the mistake of not supervising me this weekend, and so I decided to build a prototype Strobe Surface Location Beacon for use on small submersibles.

This project came about after the latest version of ABS rules were released which requires a surface location device be installed on all submersibles. Since strobe lights typically have high intensity output they seem like a good choice to aide in surface detection of a vessel as long as some way can be achieved to make them not only watertight, but also resist the water pressure obtainable by a typical personal submersible. I began to ponder what existing products could be modified for use on PSUBS and shared some email with Vance Bradley on various options. My first thought was to use an aircraft beacon which are easily obtainable from various markets. However, I couldn't find an aircraft beacon that was manufactured in a small enough format to transfer well to underwater applications. Most are either rather bulky or specifically packaged to the physical requirements of a particular aircraft. Additionally, the lenses for most aircraft beacons are irregularly shaped for aerodynamic purposes or to fit the shape of a particular aircraft. Also, no specifications exist for those lenses which makes it impossible to project (without field testing) how much external pressure a particular lens would be able to resist.

I turned my attention to strobes used for emergency vehicles. Light bars and roof beacons are typically too large for a submersible application and again, the resistence of their lenses to external pressure is a complete unknown. However, strobes designed to fit within the headlight and tailights of vehicles (hide-a-way) did hold some promise and so I began to concentrate my efforts on these units. I have found as a general rule that most products associated with emergency vehicles are inherently expensive. This proved true with hide-a-way strobes as well since most of them are sold by emergency equipment suppliers or automobile safety shops. I did a lot of web research in an attempt to locate the brightest strobe for the least amount of money. Most of the strobes I came across advertised an output of 25-40 watts and cost $100.00 or more.

I finally came across www.autodirectsave.com who were advertising a 12VDC strobe kit with an output of 100watts for only $49.99, plus shipping of a bit more than $14. So for $64 and some change, I purchased the kit which consists of two strobe lights and a multifunction control box. I attached the kit to my car battery and was somewhat disappointed with the light output. While bright enough to be highly visible in daylight, it still doesn't look like 100 watts to my untrained eye. I noticed that the packaging box had lots of information about the multi-function capability of the control box, but not a word about light output. I contacted AutoDirectSave and told them I was disappointed in the light output and that since the manufacturer made no claim about light output on the packaging that somebody somewhere must have over emphasized the 100 watt output. Their response was "everyone says these are the brightest ones". Ok, whatever. They offered to take the unit back, but since I paid $14 to ship it to me, and would require another $14 to ship it back, I decided that rather than losing half my money I'd just keep it. In any event, they are certainly bright enough to spot easily in daylight. I was just hoping for something incredibly, dastardly, blindingly, bright...all for $50. Of course, it later dawned on me that I had viewed the strobes through my sunglasses, but please don't repeat that to anyone.

As I was researching some suppliers of acrylic tubing, I came across a company Harvel who manufactures clear PVC. This seemed like a reasonable option to follow since the pipe properties are identical to regular PVC, just clear instead of colored. Well...almost. It turns out that clear PVC is not really clear, but has a bluish tint to it. A very light tint, but still, not clear. It did however turn out to be clear enough for this purpose. I was hoping it would be "clear" in the strictest sense of the word since any pigmentation would reduce the light output. I was able to find a local supplier and picked up a 10 foot section of clear PVC pipe and two clear PVC caps. The PVC pipe was $2.50 per foot which wasn't TOO bad, but the caps were $7 each which is outrageous. I'm going to call the manufacturers rep this week to find out if the plumbing supplier had the wrong price attached to the PVC caps. Given that white PVC caps are about 50 cents each, I find it hard to believe the clear is that much more expensive. In any event, this is a prototype (and I'm unsupervised) so I just bit my lip and payed it.

I ended up using eight inches of pipe for the prototype which translates to about $1.75 when the cost of the 10 foot length is pro-rated. A couple of other regular PVC fittings account for another dollar or two, so the entire prototype (pro-rated) ended up being about $83.00. I created a photo journal on the website to document how I fabricated the unit, and the prototype is for sale to anyone who wants to install it on their sub. I did this for proof of concept and am satisfied with the results, with the exception of the price for the 1 inch PVC caps.

While acrylic tubing is an alternative option for the housing, PVC is just easy to get and easy to work with. According to Sched 40 specifications, one inch pipe (which is what I used) can survive up to 900 psi of external pressure which makes it applicable to almost every small recreational sub we might encounter. I offer this project as a solution for sub owners to install a low-cost strobe location device on their vessel in compliance with ABS standards, and also as an incentive for others as a starting point in hopes they can achieve a better and/or lower cost "cookbook" solution.

The project photos are on the web site.
Go to http://www.psubs.org
Select "PSUBS Community" from the top menu.
Select "Projects & Photos"
Select "Jon Wallace" from the left menu
Select "Strobe Light Project" from the right page

Or just go to:
http://www.psubs.org/projects/1234567801/strobelightproject/





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