Walker log and sextants for SHTP

[GBR3068]

I picked up this log for $16+10 not expecting much but it arrived and was unused. I wanted the one that hangs from the rail as I dont have room for the one that has shoes.I just spent a crazy amount on a new Airmar sensor with a supposedly more accurate spinning wheel but it is not very accurate at all. People say these logs are pretty accurate. I found very little information on how to use them though. I have the manual that came with it but does anyone else use one?

Related… anyone planning on using a sextant? I have a plastic lifeboat sextant for practice but was thinking it would be fun to get a better one. Advice?

8157

[sleddog]

I've used a sextant and Walker Log to race to Hanalei in 1978. Big fish took my 3 spinners and I found an estimate of speed was plenty accurate. Remember, a Walker log gives you distance through the water, not overground. There was little plastic in the ocean in '78. These days you are likely to wind up the Walker spinner with something undesirable and have to pull it aboard to clear, always festive. I used a Plath sextant...the plastic one warps in heat, but should be plenty accurate if you use a correction.

[MillyB]

I have only, ever really used a sextant and Walker log. I own 4 sextants, and the primary one was once used on a sailing ship- the Libertad Aldgate - dated 1904. I had it calibrated, and since it's scale is largely made out of platinum, it does not distort. I have used it coming back from Hawaii and several trips to Mexico. While I respect modern navigation, I never want to lose hold of this knowledge. I did lose one spinner from the Walker log. Ugh- I hate to think of all the plastic out there !

[DaveH]

I found an estimate of speed was plenty accurate

how many oranges would be needed to keep this estimate calibrated Sled? ;)
DH

[GBR3068]

So I seem to remember that story about oranges was Chuck Hawley asking about how to measure speed with no thruhulls and you throw the orange in at the bow and time the traverse of the length of the boat. Probably more accurate than my new Airmar DST810 which measures 2.5 knot at 4 knots boat speed. Does anyone else have issues with the Airmar accuracy? and have any suggestions. This DST810 is a brand new unit with new wheel design that replaced a DST800 that suddenly started to refuse to report model number to my B&G MFD and Airmar had no idea why.

If anyone has a sextant that they would like to sell, its probably not good form to ask here but I've been shopping and the choices I see are a new Chinese-made Astra https://www.celestaire.com/product/astra-iii-professional-sextant/ or a used Plath (or a Davis plastic sextant). The problem is I have no idea what I am looking for in an old used sextant and there seem to be a lot of what look like "fake" sextants.

[Dazzler]

Probably more accurate than my new Airmar DST810 which measures 2.5 knot at 4 knots boat speed. …any suggestions.

Suggestions:
1) Have you attempted to calibrate your speedometer? This is usually done by making repeated runs under power on flat water.
2) Do you pull the transducer between races? There’s a variety of small marine life that can get in and interfere with the paddle wheel.

[Critter]

I recently bought a Davis Mk 25 sextant. 40 years ago I managed to work out a sight or two while crossing the Atlantic, then promptly forgot how. 20 years ago I took a good Cel Nav class at Club Nautique, had a good handle on it, and gradually forgot. Now planning to learn for the third time, but other issues seem to be taking precedence.

Last year I replaced the paddlewheel in my Airmar speed transducer; the pin was backing out, so the wheel was flopping around and surely not giving good readings. I found the best price at a powerboat shop in Georgia or someplace like that. If anyone needs to do the same, let me know and I'll dig up the name.

Max/Iniscaw

[GBR3068]

Dazzler:

1. I think something is wrong with my new Airmar. They keep changing the designs. So, for example, the DST800 housing is supposed to fit the DST810 but some older housings without the flapper valve dont fit with the o-rings supplied. I am wondering if I have an o-ring size problem that is stopping my Airmar from reaching the correct position in the thruhull, and this affecting the flow over the paddle wheel. The Airmar is tricky to fiddle with while in the water. I think it is going to be easier just to buy a spare, try that, experiment with what is going on with the fit "dry" rather than fiddle with the sensor while in the water. Stay tuned.

Critter:

2. I bought a Davis Mk 25 at Blue Pelican. They have about five there right now so I just bought the one that looked like new. My first sextant (other than the lifeboat version) so I know nothing. There was one of the five Davis sextants that had some extra add-on attached to the beam converger. I dont know what that was, but part of buying a used sextant was to find out what you need, what you don't and what you can add. Stay tuned. I got my Airmar with the new paddle wheel design from WMJ Marine.

[Hitchhiker]

@GBR3068 Newbie here, but not to B&G! You might consider getting a Signet knotmeter transducer. Often work better than the Airmar units.

[BobJ]

We installed a Signet blue top "Hall effect" paddlewheel on centerline when I bought the boat. It doesn't plug directly into NMEA because it's pulse-type input, so I added the H5000 computer to get the speed data into the rest of the system. What a difference from ANY of the speedos I've had before - it's just right, all the time, on both tacks.

[hijan1]

Hi, I put an Airmar CS4500 ultrasonic speed sensor in my boat in 2015, $700 at the time. It did come with a pulse converter and is hooked up to my Garmin depth sounder display. The sensor did fit into the throughhull of the old paddlewheel sensor that had been plugged before I got the boat. It has so far been working quite flawlessly. Very occasionally there is growth if I have not used the boat for a while, but it generally goes away by the time I have motored out of the Sausalito channel and am ready to hoist sails. If it it dirty it shows lower speed than my GPS. Sometimes I need to turn it off and on as well.

Not sure if your sensor is an ultrasonic sensor, but the pulse converter could not be picking up all pulses due to an electrical connection problem (corrosion?). In my boat the problem is almost always contact corrosion.

Cheers Jan