Michael is thinking and experimenting.
If enough skippers particpate, there will be a breakthrough.

Frank Perry

Here was my idea. Use the basic cyclo computer. The sensor I had planed on using was a paddlewheel type setup. Easier to build at home, lower drag. Something semi-submerged, placed at the stern. The amount of drag would depend on the intertia of the paddle, less mass=less drag. Thinking foam blades. The basic bike sensor counts the number of pulses per second. Each time the wheel magnet passes the sensor it closes a switch, creating a pulse at the computer. A switch is connected to the paddle wheel to simulate the bike sensor. The average wireless bike computer has a usable distance from the sensor of about 1m, not really enough. However, the electronic geniuses of Japan have solved this problem as well. There is a recent influx of these tiny little radio control cars. Each car is about the size of a matchbook. Each transmitter is about 2.3" in diameter and 3/4" high. The transmitter works by sending a pulse to the rx. The onboard sensor is wired to one of the control buttons on the transmitter to create the pulse. The rx is then wired to the cycling computer. Each pulse it recieves corresponds to a pulse at the pickup. Distance is somewhere between 30-100 feet. Cost of cycling computer at walmart is $12, $5-$15 for the RC car.

As Robert Fulghum once said, Maybe, Maybe Not.


Here is a link for the Speedtech impeller.


The magnet is embedded in the plastic shaft just ahead of the blades, at right angles to the axis of rotation. The Hall detector chip, nearby, will “feel” the poles as they rotate past it, as North, South, North, South, etc. By counting the pulses per second, you develop a signal that is proportional to boatspeed.

The thing is tiny. The impeller component will sit on a fingertip.

Michael and Kristopher:
Thanks, for comments and link.
We are on the same page.
Keep on, keeping on.
The future is out there!

Frank Perry

I have some digital photos of the tachometer boat, but it is not clear to me from the Posting Form how to attach them to a post. Chad? Thank you for your help on this. Best, Michael.

Mike, why couldn’t GPS electronics be used to give speed and direction and perhaps the same transmitter that transmits the GPS information to shore be coupled to a small impeller for apparent wind speed and direction? Please educate me on GPS accuracy: I’ve been told that the accuracy of speed measurements is entirely disconnected from positional accuracy; is that right?

Doug Lord
High Technology Sailing/Racing

Hi Doug, I have sent you the photos by separate email. The “telemetering” transmitter is the pc board from a HiTec pistol transmitter intended for car racing. (Ebay tuh’nology). It has two channels. I only used one channel to transmit boatspeed data. I think it was the steering wheel channel. The other channel is free to use for anything else. Windspeed would be interesting, and the impeller/hall detector would work equally well.

I’m afraid I don’t know much about GPS. From reading discussions on the electronics forums, I understand it does have high enough resolution to measure the progress of a small sailboats.

My interest is acceleration – I am chiefly interested in what happens to boatspeed in the first second or two after a mark rounding, or the first second or two after you change by jib twist by one nth. Intuitively, I think it is easier to get this data from an impeller. But I used it because it I happened to have one. The great appeal of GPS is that is doesn’t drag anything through the water.

Still, any of these systems is heavy. You are putting a transmitter on your boat, and the eight NiCads that go with it. As science, okay. But as a racing accessory, I think nix.

Any system that reports a change in position has to be teamed with a clock to produce information about speed as, for example, a function of impellor revolutions per second. The Basic Stamp, like most processors, has a clock built into the chip, so the “per second” is easy to come by.

I think Kristopher has great idea with the bicycle speedometer readout. It would save a lot of tinkering around to have the tachometer component and readout already manufactured and packaged.

Best, Michael

A photo of the telemetering speedometer dinghy has now been posted in the articles section on this site, along with a brief description of the components. Best, Michael

It seems since I mentioned the little cars they are impossible to find! Last week the mall had them at every turn, there were none last night. I will have to keep looking, Walmart has them for $20. If I can get my hands on one I will try to build a working prototype and publish the details.


Checkout www.layline.com/prodinfo.asp?number=tmx59561
It shows a wristwatch style GPS

nerds of the wold untie

I rounded up all the electronics I need tonight. Should I put together a how-to or is the previous description self-sufficient? Target had the little cars on sale for $10, I have an old bike computer…so far the price is right!


i wonder what happen to us puting our boats in the water and sailing for fun. I saw a posting for an ice boat up there, and no body said anything
i will nice boat. any plans you know off