This seems like the only reliable way to go. Speed traps are subject to wind shifts, radar guns are fine, but expensive and not so easy to come by. Why is the data so hard to compile with a GPS? Even a cheap one will give accurate averages and max speeds. Mine read 29 knots max in a big puff on my Hobie 20. We were going up wind, but not too close hauled, on a mountain lake with very flat water. The speedy stretch didn't last long - maybe a quarter mile - but was very wild.

one word...current. A GPS has no way to account for current and will only read ground speed. A speedometer mounted on the boat and sensing the water will account for current and give your true water speed. It depends on what you are after and where you are sailing I guess.

I have tried number of things to measure speed on my boat and most methods fall short for one reason or another.

The I tried both versions of the speedmate, the trailing wire and the non wired version. I mounted the trailing wire speedmate on the front crossbar but it was hard to read from the wire. The non-wire version has an impeller that mounts to the trailing edge of foil, so I mounted it on the rudder and put the display on the rudder arm. This worked well but you need 2 units, one for each rudder, plus the impeller is very fragile and it ends up getting clogged up with salt water.

Next I tried GPS. I went through 3 Garmin etrex GPS, but the waterproof claim wasnt real and they all stopped working after a couple of salt water dunkings.

Most recently I bought a Suunto M9 GPS watch. This thing is pretty cool and will tell you all kinds of sailing/racing data like laylines, favor end of start, headers, shifts, etc. However the GPS takes forever to acquire and if you are not careful it loses view of the satellites and the GPS function stops working. Plus the menus are cumbersome and the battery life is limited. Also, it is a big watch and the band isnt quite long enough to fit comfortably over a wetsuit, gloves, spray top,etc. Its probably better for a monohull tactician type that has time to navigate the menus and isnt wearing a wetsuit or moving around like we do.

Has anyone found a reliable, really waterproof GPS? I dont really want to put it in a plastic bag. And it should be small. Anyone tried out the new Garmin Geko? Garmin is also promising a handfree marine unit in March 2004.
http://www.garmin.com/products/foretrex201/#

I wish that Tactic would put a GPS receiver in their digital compass. The Tactic works great, its waterproof and solar powered and the compasss works great. They could make the display bigger and add GPS based speed readout. I bet the cat sailors would all buy one.

Anyone have a contact at Tactic?

Bill

Well, yea, but won't current also affect impeller-type speedos? It seems like using the current is another tool in the art of maximizing speed in any sailboat.

I used a Garmin Geko on my cruise to NAMSA Mid-winters.

In my opinion its operation was flawless. Only negatives are; small viewing screen and batteries have to be changed every 10-12 hours.

Admittedly, I have no other experience to compare it to. It just got me there and back.

Salt water will no doubt make a GPS not water proof after a few dunkings. The salt makes the rubber stiff and crack even after only a few uses. TO keep this from happening, you can spray the outside (not the screen) with a dry silicon spray, or you can wash it when you get home. I have had similar problems when i was doing some mapping for my university out in seattle. Washing it daily is what Garmin recomends. For the battery problem, i purchased some good energizer rechargable batteries. I would use my unit for 10 to 12 hours at a time and it would last the whole time. It only takes an hour or two to recharge and the charger automatically shuts off when charging is done. Presto chango.

Reid Rechel
N5.2
Lake Superior

Good points! Hadn't thought about rinsing, stays dry except for some occasional spray.

Also, I'm in the market for a solar cell type recharger for all onboard electrics. Any suggetions in that regard?

I remember seeing a solar recharger (or power adapter) made by Sony that was for operating Walkman's.

Since Walkman's are probably low (electrical) draw items, what I would do is read the specifications on the solar device as to output. See how many milliamps (MA) it puts out.

Make sure it it puts out the amount you need for the GPS. The Manual for the GPS should tell you this somewhere in the technical data section. (front or back) Garmin has good gear and probably makes a solar charger.

Also the solar charger may put out a leser amount but by the same token it may put out some of the necessary juice so that the installed batteries last longer. I would ask the manufacturer if this is possble. It may be that when you hook up an auxiliary power source the main pack is disconnected.

Even if the output of the solar device is less than the amount required to charge it, it may have enough juice to operate it.

Make absolutely certain you get the polarities correct when connecting the two devices.

Another way to skin the cat is to buy rechargeable battery packs that have a lot bigger batteries with the same voltage as the ones you put in the gps. Lots of model radio controlled aircraft/boat shops/sites and rechargeable battery resellers will gladly make you up a blister pack with batteries that will last as long as you could ever want them and you would just get an adapter power cord to hook it up to the GPS. The GPS manufacturer may even sell them.

Most regular AA cells would have (I am guessing) about approximately somewhat maybe 500 to 1000 MA of juice. If you use the battery up in 10 hours you are using (for instance @1000 MA battery) 1000 divided by 10 = 100MA per hour. so if you buy a battery pack with all 4000 MA batteries you get 4 times the life.

Also not all batteries are created equal. NiCad's are cheaper and come in a wide range of output. You can get fast charging ones that have low output (Ma) or slow charging ones that have lots of juice. The fast charge ones are OK with getting overheated. Some missile batteries can be charged in minutes.

NiMH batteries are slow charging and supposedly give out more juice as much as 50%, although I've heard some people say this is not true. Maybe someone else can advise.

In my hang gliding days we used to make up battery packs which we would remote into our pod harness for long days going cross country.

Make all connections very high quality! Better still get a professional (such as a marine) electronics guy to make up the connections as salt and or water is very corrosive and you don't need a battery /GPS failure. Poor connections can be a pain as they cause gremlins.

Thanks Alan! I'm continually amazed at how much information you can pick up on the site!

As a flyer of electric powered Radio Controlled aircraft I have a fairly good knowledge of rechargable batteries. There are currently four technologies which would concern us here:

A. NiCd - (nickel cadmium) commonly known as Nicads. These are the most common type of rechargable batteries and available at just about any hardware store.

B. NiMh - Nickel Metalhydride - these have a capacity that is about 150 to 200 percent the capacity of an equivalent sized nicad.

C. Li-ion - Lithium ion - these are a step up again from both NiCds and NiMh

D. Lipo - Lithium Polymer - these are the batteries that the RC world in a state of excitement. They have a capacity perhaps six times the capacity of a NiCd pack of the same weight.

Li-ion and Lipo are the battery technologies that are used in laptops and mobile phones. These batteries also require that EXTREME care be used when charging as Lipos especially can cause serious explosions and fires. There is a lot of energy stored in those little babies when charged. Overcharging will cause the cells to balloon and explode. Mobile phones and laptops have sofisticated circuitry built into the packs to ensure safe charging and discharging. We RC'ers though construct packs with no such circuitry as we require packs of various voltages and capacities which are not used elsewhere. There have been several near misses and a fair bit of burnt property: cars, houses, garages that have been caused by incorrect handling of LiPo's. Unless you can adapt a mobile phone battery to fit in your GPS (and it happens to be the correct voltage and supply the required current) I would say that this technology is currently not suitable for use in a GPS that is not designed for it. I am surprised that Garamin doesn't have batteries similar to mobile phone batteries in their GPS's. It could be due to the current requirements. Lipos are not able to supply the high currents that NiCds are capable of - they are catching up though.

Bottom line for Lithium batteries: DO NOT PLAY WITH LITHIUM BATTERIES UNLESS YOU KNOW WHAT YOU ARE DOING!!


NiMh is probably the best bet for GPS use as you can buy them from many hardware stores of the shelf. They require a different charger to NiCds so make sure you get the correct charger and do not attempt to charge them with a NiCd charger.

NiMh batteries are also much more environmentally friendly than NiCds. Cadmium is a heavy metal which should not be simply chucked out with your usual rubbish. NiCd batteries must be disposed of correctly. NiMh on the other hand are safe enough to chuck out with the rest of your household rubbish.

Rob.

Thanks Rob. And my wife thanks you, she'd as soon I not burn down the house!

Hi Gareth,

I have used the Speedmate on my windsurfer. The impeller lasted 4 years in the Chesapeake Bay, Long Island sound, North Carolina surf and even the East River in the Bronx. It was great for getting a continuous speed readout that is not effected by current.
Never tried the catamaran version.

Some hand held GPS units can give spurious results for maximum speed. If the GPS is unable to get a good fix for a couple readings when you are sailing slowly, and then gets a good position fix when you are sailing fast it will report a false-high maximum speed reading. If you read the same speed for 10 seconds or so while sailing you can be confident that your speed (over ground at least) is correct. Just don’t trust the “max speed” stored in memory when you get to shore.

I also have a Timex GPS speed/time/distance watch that seems not to have this problem. The watch is intended for running, and the engineers must have designed in some better filtering. The unit consists of a water resistant watch portion and a (3x3x1in) receiver that is “weather” resistant. The watch only reports speed and distance – not position or velocity.

I always put my handheld GPS or the Timex receiver in a vinyl dry bag. The dry bag clips to my life jacket on the cat and to my booms on the windsurfer. Just for reference, zip lock freezer bags do not seem to be even water resistant. I killed an FRS radio that way.

Happy sailing (Tw + Ta -> 100 deg f spring is almost here!)
-colin

I hate to run too far off topic here, so I will offer my gps advice after I mention my solor battery observation.

On Solar, I must humbley bow to the best hobo I've see on the internet. That would be TIMO NOKON ANSIOLUETTELO, The Professional Hobo.

This kayaker who has done many things for himself, as hobos do, has done some very innovative things with such things as electronics and solar charging.
Solar batteries on a Garmin Etrex.

Now for my take on gps's while cat sailing. I use a Garmin Etrex because it is small, light, "waterproof," and has a huge load of electronics packed inside of it.

You need to do what you can to reduce the impact of water spray, but I can tell you that I have reported my position from the belly of a pitch-poled Tornado in the ocean with this unit after it had taken a dunk with me.

The battery case leaks a little bit, but you can open it up and dry it out. Sometimes they leak water and go crazy and eventually the joy stick will go bad. But Garmin, with their best customer service I have ever seen, has always taken care of me!

My advice is to keep it in your pocket when you are not viewing it. They will read satellites right through the fabric of your pocket. Keep the direct salt water hits to a minimum and rinse them off when you get home.

The weak point is the data contact points. The rubber cover is not waterproof. If you don't take action against this leak, you will end up with some serious electrolysis that will eventually cause problems with the computer, patch cord. But when the electrolysis is occuring, you will be bleeding your batteries.

The solution: Place a couple of 1" long pieces of electrical tape over the edges of the rubber flap that is supposed to be covering-up the elelctrical contacts. This takes care of it. And I have proven it in 3 and 4 day trips in the Santa Barbara Channel at Channel Islands National Park.

(Who else do you know who has been There?)

GARY

I now have a Garmin 76S that lives in a dry bag. We nuked three etrex legends in the '02 Worrell. Typically you could see liquid water droplets through the blue plastic. We did encounter electrolysis (to some degree or another) on all four of the units we had.

The next to last night I wanted to download the tracks from that day, however the contacts were so bad that I couldn't even jury rig a solution (was using foil from a Becks beer bottle to fill the holes, it worked on previous attempts). On the last day, both GPSs we were using died. One died one the water; the other one gave up the ghost on the beach. I really hate it to, because I would have LOVED to have the data from both those days. It doesn’t really surprise me though, because they got HAMMERED that day. Anybody still have their tracks from those two days?

I love all the features on the 76S and the big screen is GREAT! However I don't trust it to be any more water resistant than the Etrex.

I got the following reply from Tacktick when I inquired about a solar GPS/Digital compass

"Thank your for your comment on new product possibilities.

We can only agree that this would be a useful product but currently there are two problems involved.
1. Currently GPS engines are relatively power hungry and are difficult to operate via the Solar charge routine.
2. Most Class associations specifically outlaw use of direct speed input into their electronics and therefore the market is restricted making anything other than an extremely expensive item impossible to design and produce.

All this is great for the future and rest assured that as soon as situations change Tacktick will be in the forefront of developing this type of product.

Regards

Steve Moore
Customer Support
Tacktick Ltd.
Tel.: +44 (0) 1243 379331 (ext30)
Fax.: +44 (0) 1243) 379199
steve.moore@tacktick.co.uk
www.tacktick.com"

I've found that a little vaseline or other waterproof grease does wonders around the battery compartment lids and cable sockets with rubber caps on these GPS units & on my marine radios.
I've sailed for many years now with a Garmin GPS III+ mounted on my boom for hands free monitoring of my course. The mount lets me swivel the unit after a tack. I can read the display (set to large numbers in compass mode) from the rear corner, and even while trapped!

Try it out!

Mike.

Great post...but one thing I didn't see mentioned...NiCds suffer from a memory effect where unless you are regularly fully discharging/re-charging them, not just topping them up with the charger, they tend to lose their full capacity quickly. NiMh do not have this problem and so you don't need to replace them as much as NiCds.

MaHa makes a great battery pack charger that can handle both NiCds and NiMh's in many voltage/capacity ranges. I use it to fully cycle (i.e. us the discharge function to drain the battery, then automatically re-charge it) on my 1400 mAh NiCd battery in my Marine Radio. And also to charge differnt battery packs around the house.

Check out http://www.mahaenergy.com/store/viewItem.asp?idProduct=185 for more info.


Mike.

I still have much trouble in realizing that you have not capsized. My gps has been in the salt water, reporting my position when turtled. And you sail in some of the wildest waters.

GARY

Mike,

You quite right I didn't mention the 'memory effect' of NiCds. I didn't think of it at the time but if I had I probably wouldn't have mentioned it anyway. There is much debate about this effect and whether it exists. Some say it doesn't some say it does, I'm sitting on the fence. There are even cell manufacturers that guarantee that their NiCd cells will never develop a memory. (see http://www.srbatteries.com for example)

Still others will argue that the effect does exist but can be reversed by cycling the batteries as you mentioned. There are charges available in the model aircraft world that can be set to cycle batteries a number of times. The claim is that this will recondition NiCds. If you find that your NiCds are not performing as they used to you may be able to breathe new life into them by cycling them. This can be done without a specialist charger simply by fully discharging the cell then fully charging it a few times. You could discharge it by leaving it in whatever you usually use it in and leave the device turned on till the cells went flat. You then charge it for the recommended time so that it is fully charged and repeat as neccessary.

If you are interested in high tech computerised battery chargers the one I use is called a Triton charger and it can charge all the battery types I mentioned as well as lead acid batteries like the one in your car. See: http://www.electrifly.com/accys/gpmm3150.html for info about the Triton charger. This charger is really overkill for anything but Electric Flight or similar use. The charger that Mike mentioned looks like an excellent choice for the average user.

I hope this isn't too off topic for a sailing forum.

Rob.

Ahhh...you just want me to buy a Solo-Right from you

Mike.