Hydrodyners.com

Hey Jim

You know a fair bit!

I used to get lots of calls and emails from people wanting a brass equalizer. I've never found a good reason to have one and everybody that has removed it has thanked me. I updated my web site with details of what the tube does. I agree with you, Airguides are much better without the tube. Fast and accurate.

Did you see www.skirecord.com

Greg

Greg,

I was aware that you guys had done that, but I had not seen all of the footage. You have to hand it to the guys in the middle in all that wake. Thanks for the link.

You have a fun loving county, I enjoy the V8 sedan racing series. It is cool.

I think the Morgan +8 still sells there too. It is no longer available here.

Ford and GM build V8 rear drive sedans (in Australia) that are really cool and fun. They are not available here.

In all fairness to the engineers at Airguide, I think the equalizers were used to help prevent water from traveling up into the line and getting trapped from high speeds. When water gets trapped way up in the line, it creates erratic readings. Your pressure limiter will prevent that. In any case, it is easy to blow it out.

Airguides are not for everyone. I have seen them really abused by teams. They require some care such as blowing out the lines in the fall. As you know the mechanism is similar to a clock. Some care and maintenance is required. Water ski teams are not always known for that. And quite frankly, most recreational skiers and many teams do not require the accuracy that I am looking for. That is why they do not understand.

I still maintain that a gps in the hands of a driver that does not understand how it works is worse than no speedometer at all.

jim

Guys

I was lucky to be on a Test boat for a new Volvo engine recently and they were also testing a new GPS Speedometer from a company called Veethree which is the old Teleflex gauge company. The speedometer was dead on, gave heading and was fairly smooth too. I am in the market for a boat and will look forward to getting a unit.

T/C

In my opinion one should study this article before buying any GPS:

http://continuouswave.com/ubb/Forum6/HTML/002179.html

You will at least understand what you are and are not getting.

jim

I have been thinking a little, or maybe a lot about using GPS measure speed.
Apparently, some GPS speedometers use a Doppler shift to measure speed, and in order for that to work, you have to moving closer or farther away from the satellite it is using for the Doppler shift information. That means a satellite directly overhead, cannot be used, because you are not really moving closer or farther from it. Unfortunately, the satellite directly overhead is in the best position for signal strength.
Likewise, a satellite 90 degrees to port or starboard will also have no relative change in the distance to the satellite, and is useless for Doppler shift information.
The best position for getting Doppler shift information is low on the horizon, directly in front, or behind you. This is the satellite that give you a relatively weak signal, and is possibly getting ready to set, and drop below the horizon, or it is rising, and could get into a position directly overhead, and become unusable.
Now, if you turn 90 degrees, the satellite that the GPS was using is now useless, because the change in the distance to that satellite has dropped to zero, and the GPS unit has to find a new satellite to use.

I use GPS Speedometers on boats. They work pretty good. I like them better than the pitot tube speedometers but I live on a lake that has it's fair share of weeds. There is some lag when you change speeds. The time when I notice the lag the most with GPS is accelerating up to barefoot speeds quickly. The old Air Guide Speedometers have some lag too.

There appear to be no problems when you turn the boat even very sharp.

Drive By Wire is awesome but that is another story.

I wouldn't worry at all how it works, but the Perfect Pass GPS speedo is excellent.

However, don't buy the basic 1hz model, all 1hz models are rubbish for skiing (in my humble opinion!)

The 5hz model is expensive but works great. One update per second is not enough for skiing. 5 per second (5hz) is fine.

However, an Airguide properly configured is almost impossible to beat. A 5hz GPS is as good but no better. I would NOT use the equalizer tube as it slows the response down too much. People thank me for my advice to remove it.

The only drawback to airguides is if you live in a weedy lake and you use transom mounted pickups. Outboard pickups do not often clog even in weedy locations.

Lots of info at www.airguide.com.au

Greg

There are some new GPS Speedometers for boats available that are very affordable. They sample 10 times per second. I will be testing one shortly.

I have never understood why a manufacturer does not make a Portable GPS Speedometer like the one in my car GPS System that I sit on the dash and move from vehicle to vehicle. I'd make it with a big digital readout with an analog gauge that runs on an internal battery or plugs into the accessory outlets.

My Garmin was only around $100 at it does lots of other things well also!