Portable Speed Log.

I was wondering if any members know of a portable log.

My boat has a couple of on board navigation systems that I am happy enough with but they only give an ' over the ground' boat speed and not a through the water boat speed.

I am happy enough with this and for most situations it is all I need but as we all know, if you know the difference between the over the ground speed and through the water speed you have a bit more information at you fingertips.

I was hoping to find something that I could use on an occasional basis until the next time I haul out and fit a permanent log.

Any suggestions (nice ones) would be appreciated.

Rick.

I remember doing a trip from Mackay to Townsville in a mates Cherry 16. All we used for a log was a bit of rope (maybe 15-20m long) with a float on it. We would have one end of the rope tied to the boat and the other tied to the float. Then we would hold the float beside where the rope was tied to the boat and let the rope drag in the water. Then we would drop the float in the water and see how long (timed) before the rope pulled tight on the float. I had calculated the speed of the boat for a few different time frames. Below are some for a 20m piece of rope. Can't get much cheaper than that!

If you need more accuracy, use a longer bit of rope.

7.9 Knts 5 Sec
6.6 Knts 6 Sec
5.6 Knts 7 Sec
4.9 Knts 8 Sec
4.4 Knts 9 Sec
4.0 Knts 10 Sec
3.6 Knts 11 Sec
3.3 Knts 12 Sec

Hi Crusoe,

Yes, I remember the old system of using a board and rope to calculate speed. It's just that I'm a lazy bastard and was hoping to find something a bit simpler.

You know, the old ways were all tried and true, but with the newer technology we all think there is something out there we can use or adapt to our purpose.

If push comes to shove I guess I'll be doing it the old way. I was just hoping there would be an easier (lazier) way.

Thanks for jogging my memory though. It sometimes needs a bit of a kick start, lol.

Cheers, Rick.

Thanks Cisco,

Sounds like the sort of thing I'm after.

I'll look it up.

The heart rate monitor would be good, although the only time I got past hull speed was on the East Aus Current going down a nice long swell. My GPS registered 11.3 knots, not bad for a 9.3 meter boat.

I don't want to use it all the time, just when I'm in places where tides or current may effect my speed so that I am able to get an idea of what progress I'm making and how I should handle the situation.

Thanks again. Rick.

Just had a look.

I'll contact the seller. I suspect the impellor housing is still in the hull it came out of.

As long as its working it would be worth buying.

Thanks