Unused thru hulls - knot meter sending unit

[Paul F]

Like many sailors I have gone with a gps instead of the existing in water knot meter. This leaves the thru-hull with a plastic blank insert. The plastic insert is fairly thin and you know "plastic". What do you think? Should I forget it or find something better to replace the insert?

 

[Ross]

Hole in the bottom

Grind the area clean and put on a proper fibberglass repair. That way when the weather pipes up you won't worry about the thin piece of plastic leaving home.

 

[mortyd]

hole

you may have gone gps but you have replaced water speed with groundspeed - apples with oranges. they are only the same if you have no current or tide. get a new knotmeter.

 

[JC on Bainbridge]

I agree, get another speedo

Here we go again. This is the same old issue that so many boaters gets confused on.GPS and speedo are not the same thing. GPS is speed over ground, speedo is speed over water. Totally different animals.Imagine yourself running on a treadmill at 10 MPH. The GPS will show you are going at 0 MPH. The speedo will show you are going at 10 MPH. If you are running the other way, if you could, your GPS will show 20 MPH.If your old speedo was retired because it died, then get another one. If it was retired because you thought a GPS would replace it, then get it back onto the boat and reinstall it.

 

[Paul F]

back to the question unused thru hulls

Knowing the difference in ground v real speed is not the issue. The boat is in the water and is likely to stay in the water for a least another two years. The question is how safe is the plastic insert replacement for the sending unit?

 

[Ross]

Travel lifts

Just have everything ready, ask your friendly marina operator for a three hour haul-out and repair the hole. polyester resin cures fast, fair it and apply some bottom paint and put if back in the water. then you don't have to worry about that temporary plug.

 

[Paul F]

All marinas are now condos

Thanks Ross, good idea and I could do it. Around here all the marinas are gone. Nearest take out is miles away, but what you suggest may work thanks.

 

[charles]

GPS is adequate except that

On my boat I'd be satisfied with GPS speeds except for one detail, my wind speed readout. Raymarine for some foolish reason uses boat speed to calculate true wind speed and direction as opposed to GPS speed. Not only is GPS more accurate for a true wind speed calculation, more importantly using GPS speeds means you don't have to clean the knotmeter. When the knotmeter is fouled boat speed is zero and the windmachine displays relative wind instead of true wind. The Raymarine Seatalk bus has both speeds to choose from but the wind machine has its heart set on boatspeed only. I have tried to explain to Raymarine that this is a simple software fix but have not been sucessful.

 

[higgs]

I second Ross

Obviously you are not confident with the insert so to give yourself peace of mind you need to haul to boat, grind it out, layer in fiberglass tape to build up the area then sand smooth.

 

[mortyd]

hole

here's the main point. if you really want to know how your boat is performing at any given time and condition, only water speed will tell you, and only a knotmeter will suffice. i have a gps for navigation and love it, but if you want to use it to tell how well you have trimmed sail, burn the gps and watch the smoke. that's all a gps will tell you about sail trim and boat efficeincy.

 

[Benny]

Leave current transducer in place.

Just leave the transducer in its place until your next haulout.

 

[Terry]

thru hull

The plug will seal the thru hull the same as the knotmeter, no problem there. If the thickness of the plug is a worry, drill a small hole in the top and fill with epoxy. This way you can always use the knot meter at a later time if needed. As for the debate of speed over land vs speed over water, if you aren't going anywhere in particular, who cares. If you are, then the actual speed, GPS, is the best way to go. Sail On... Terry

 

[Ross]

Tides

Paul, If the tides run to enough range you can ground the boat just past high tide, careen it as the tide ebbs, get your work done and refloat with the next flood.

 

[jimg]

thru hull

If your transducer is the same as most that I have seen, the plug is attached exactly the same way as the transducer paddlewheel, with a large screw-on collar of some sort. If so, then the plug is just as safe as the paddlewheel. Here where the weather is warm and boats stay in the water year round, for years and years, it is quite common to leave the plug in at all times the boat will be just sitting, and put the paddlewheel only when sailing. That's what I do, it keeps the paddlewheel cleaner.

 

[b393capt]

Charles ... Contacting Raymarine

I too, would want my wind machine to use GPS when calculating true wind speed. Can I lend some weight to convincing Raymarine to make this tiny software change? Who are you writing too / calling ?

 

[flyhop]

Forget it and go sailing

Seal up as described below at your next haulout if it really bothers/worries you. The plastic blank is probably fine. I don't think that the plastic would crack/break unless you hit it from the top. Even then, the plug is probably as good as the threads that are holding it in place. I'd let it be for the time being, but there are some excellent ideas on getting it sealed up now. I like the "Tides" idea. My two cents....

 

[Warren Milberg]

If you think..

.. you'll never use the knotmeter thru-hull again, best to seal it up. This is a fairly easy repair and covered well in the Nov/Dec 2005 edition of "Good Old Boat." In the interim, if the plug for the thru hull is in good condition, I doubt you have to worry about it failing.

 

[Liam]

Another intake??

If you ever thought that you would like to have a salt water galley pump this would be a good time. You can really stretch your fresh water by using salt for most washing, cleaning, boiling things, etc. When away from the dock (don't use harbor water) it really comes in handy.

 

[mortyd]

hole

again, you haven't replaced anything, anymore that a new stove replaces a refigerator. put a knotmeter back in, you will need it eventually.

 

[Geoff]

Changing plugs

jimg, I've never pulled the plug while in the water. How difficult is it? How much of a fountain is does it cause? How fast must it be? 3 seconds? 30 seconds? 3 minutes? Is it no big deal or a tense moment?Geoff