How important do you find a 'speed through water' reading.

[markbarendt]

Currently we have 15 through hull holes, at, close to, or below the waterline: we want to eliminate most of them.

One of the upgrades here is going with composting toilets so all the 'sanitary plumbing' and their separate sea water intakes are going away.

We may add options like fancier sonar at the next haul out, after we figure out more about how we like using the boat. We'll poke new holes then for that stuff as, and if, needed.

Before the fiberglass starts filling the holes in a few weeks we are trying to think through what we might want going through our bottom for the next 2-3 years.

For now we're planning on keeping:
A-two gray water drains
B-one sea water & engine cooling inlet (with a manifold to supply sinks and anchor wash as needed.
C-one shared bilge pump discharge for our two pumps
D-one depth/fish finder transducer

The boat does not appear to have ever had a speed transducer.

My impression and experience seems to indicate that the old paddle wheel sensors are pretty marginal in reliability anyway unless the wheels get cleaned regularly. A fair number of people seem simply to give up on them unless they are racing.

I found this one https://www.nasamarine.com/product/electromagnetic-log/ which is reasonable in price and has no wheel and thought that looks interesting.

So my question is 'do you see a practical advantage with yours?', say in diagnosing performance problems or in navigation or something else.

Does your water speed sensor get used and does it make your life easier?

 

[rslifkin]

I don't have one and don't miss it. In my mind, it's an occasional nice to have, but not at all necessary.

 

[RT Firefly]

Greetings,
Mr. m. I would re-think the single bilge pump discharge. You will have to incorporate anti-backflow valves, of some sort, and these have been known to fail/cause problems. The LAST thing you want in a leakage situation is a bilge pump system failure. My $.02.


Regarding speed sensors. As Mr. rs said. Don't have one and don't miss it.


A question: Why are you having sea water go to the sinks? The only use I can see for that is rinsing dishes.

 

[Capt Jack]

Have one that looks like it is as old as the boat. Has not worked for the 5 years we have owned her. Removing and filling the hole this haul out. On previous planing hull I liked the gps speed reading much better and found the paddle wheel to be unreliable.

John

 

[bayview]

Had one on an older boat the was very erratic.

never saw the need. SOG is what I need to tell me where I am.

 

[Ski in NC]

Paddle wheel speed sensors are not very accurate and very prone to fouling. Just use the GPS and take note of current. It will be accurate when in areas with known no current.

And second that about not sharing suction/discharge flows with different machines. That can cause all sorts of bad outcomes.

 

[Bacchus]

Current boat has COG only via GPS and don't feel it's a big problem.
Last boat had paddlewheel for speed and it was interesting sometimes to compare Speed to SOG to see what the current was. As noted the paddlewheel accuracy is questionable so true comparison difficult.
I found I could calibrate my paddlewheel but could only get it accurate at low OR hi speed but not both. Don't miss it.
AN interesting aside - In 2019 I repeated a cruise we had done 20+ yrs ago in our previous boat and found my old distance log where I used the paddlewheel was off around 20% vs recent cruise using GPS exclusively.

 

[High Wire]

With the speed and accuracy of GPS today, paddle wheels are not necessary if you just make an accurate rpm table.
Where I see it useful is fishing by trolling where certain lures work best at certain speeds and you need to tweek lure speeds a tenth or two quickly.

 

[markbarendt]

With the speed and accuracy of GPS today, paddle wheels are not necessary if you just make an accurate rpm table.
Where I see it useful is fishing by trolling where certain lures work best at certain speeds and you need to tweek lure speeds a tenth or two quickly.

There we go, trolling for fish is something I had not thought of.

 

[markbarendt]

Greetings,
Mr. m. I would re-think the single bilge pump discharge. You will have to incorporate anti-backflow valves, of some sort, and these have been known to fail/cause problems. The LAST thing you want in a leakage situation is a bilge pump system failure. My $.02.


Regarding speed sensors. As Mr. rs said. Don't have one and don't miss it.


A question: Why are you having sea water go to the sinks? The only use I can see for that is rinsing dishes.

Good thought on the bilge discharge.

The sea water is for washing the decks, anchor, anchor rode, pre-rinsing dishes, and in general keeping the grand kids from wasting all the fresh water.

 

[caltexflanc]

I enjoyed having a working STW gauge. We cruised in a lot of places with varying currents, and it was useful in understanding what those were, plus I enjoyed comparing them to the predictions, and generating my own extrapolated predictions for locations that were not a substation. At any given point in time, STW determines what your engine performance and fuel consumption actually is. If you wanted to maintain a certain fuel efficiency, then understanding currents helps with trip planning. The sport of basic navigation is one of the pleasures of boating for me.

By the way, I too would absolutely avoid consolidating bilge pump outputs.

 

[Northern Spy]

It's important for catching salmon depending the lure. Hoochies, spoons, and plugs all have different speeds to be effective.

I generally have to clean mine a few times a year.

What is interesting is how much current changes on the flood and ebb relative to geologic features like points and islands.

If you don't fish, I find it more of a novelty.

 

[refugio]

It was important to me - I just added an Airmar DST810 to get STW. I already have a Raymarine RV200, but I needed STW for Raymarine MFDs to calculate Set and Drift. And the really odd thing about Raymarine Lighthouse is that they also use STW to calculate TWA and TWS - which I was also interested in. I don't agree with their reasoning, but fighting them was pointless.

So if you want Set, Drift, TWA, and TWS and you're using Raymarine, you'll need STW. The Airmar unit I linked to is solid state, NMEA 2000, and has quite a few additional features - but no paddlewheel.

 

[Hippocampus]

Will take a contrary view. Had an Airmar ultrasonic sensor. Total POS. They replaced it 2 times at no cost to me but I got tired of running the wire so went with a paddle wheel. Find it’s key for understanding set and drift. Although carry nav on a garmin handheld, open cpn in a toughbook, navionics on on 2 IPads and 2 iPhones still want direct readings from sensors integral to the boat. Find having that speed through the water gives you information you can’t get any other way. In the open ocean without it there’s no way you can see ocean currents. You can feel it indirectly seeing your SOG rise or fall and when the AP steers more in one direction than the other. But the speedo to sog comparison tells you right off. Yes, we also watch water temperature, look at satellite images and listen to the weather router to understand currents but the speedo remains important. Must be a dinosaur. Also run a DR plot of our progress, carry a log and a lead line.
BTW- a bit of transducer paint and taking it out (putting in the plug) when away from the boat you can get decades of use with no issues.

 

[rslifkin]

I have a feeling those with sailing backgrounds will tend to find speed through water more useful. For me, with a powerboating background and not crossing oceans, tide and current charts, weather info, etc. give me enough in terms of what to expect for currents. And I know what speed the boat does at my typical cruise RPM in flat water, so if I'm going faster, I've got a tailwind or following current. If I'm going slower, it's either due to seas, wind, or current slowing me down.



Having an onboard check of that stuff is nice, but in the end, what matters for getting where I'm going is "how fast am I moving and in what direction?" which is answered by GPS SOG / COG.

 

[bayview]

It was important on my sailboat because small changes in speed were important.

 

[ancora]

For Predicted Log contests, my GPS is woefully inaccurate. We run the measured mile before every contest for accuracy.

 

[O C Diver]

Having an onboard check of that stuff is nice, but in the end, what matters for getting where I'm going is "how fast am I moving and in what direction?" which is answered by GPS SOG / COG.

As far as combining discharges, I rather like the setup on my boat. I have a 2" through hull on each side above the waterline and under the swim platform. Almost all discharges (galley sink, shower and sink sump, air conditioning raw water & condensate, clothes washer, and most bilge pumps) are plumbed to them. Because of their size, they act as 4" drain pipes in a house. All discharges have high loops to prevent siphoning. Really like the clean look of the boat sides without all the through hulls and stains below them.

Ted

 

[Hippocampus]

Also think Raymarine isn’t the only autopilot that requires STW to function correctly.

Would note getting rid of through hulls is a great idea. Believe they are a common reason for sinking when a boat is unattended. Putting in manifolds/sea chests is easy enough to do. Just keep in mind high flow (engine cooling) or pressure sensitive (watermaker) requirements in mind. Would always want engine intake separate.

 

[Comodave]

Last year we glassed 3 thru hulls closed when we had the port engine out. This year I glassed 6 holes closed while we have the starboard engine out. Glad to get rid of all those holes. Did you say you have gray water discharges below water? I would get rid of them and move them above water. Below water you can get barnacle fouling. A friend had his sink drains clogging all the time because they were below water. If you are worried about stains on the side of the boat, cut some clear hose and glue it in the bottom side of the thru hole that is above the water. It will act as a drip edge and the water won’t run down the side of the boat. Good luck.

 

[BigTime]

It was important to me - I just added an Airmar DST810 to get STW. I already have a Raymarine RV200, but I needed STW for Raymarine MFDs to calculate Set and Drift. And the really odd thing about Raymarine Lighthouse is that they also use STW to calculate TWA and TWS - which I was also interested in. I don't agree with their reasoning, but fighting them was pointless.

So if you want Set, Drift, TWA, and TWS and you're using Raymarine, you'll need STW. The Airmar unit I linked to is solid state, NMEA 2000, and has quite a few additional features - but no paddlewheel.

If you want Set, Drift, TWA, or TWS you need STW regardless of who or what is doing those calculations for you.

 

[SoWhat]

If you are in an area with numerous speed zones then an accurate speed would ne nice. GPS speed is adequate but not terribly accurate in a current.

I would shy away from connecting X bilge pumps to 1 drain. Redundancy in a boat is a good thing.

 

[Dougcole]

Pulled our raymarine paddle wheel and glassed over the resulting hole last year. I never used it a single time in 8 years of running the boat. I hated having it, as it seemed to be made of cheap plastic and just didn't feel safe to me. The boatyard manager who did the work told me paddle wheels are the most common cause of sinking that they see in boats.


Just my .02.

 

[Lepke]

In the 1970s I trolled salmon and tuna without a speed sensor or GPS. I banked 80Gs or more a year after expenses.

A shared thru hull has lots of potential problems.

 

[OldDan1943]

Mark and others, I have install 3 additional bilge pumps. I alternate discharge, port/stbd incase the boat start to list. If one discharge is under water then the next bilge pump will discharge to the other side of the boat.

Mark IMO, 2 bilge pumps on one through hull if a VERY bad idea.

 

[Bacchus]

With the speed and accuracy of GPS today, paddle wheels are not necessary if you just make an accurate rpm table.
Where I see it useful is fishing by trolling where certain lures work best at certain speeds and you need to tweek lure speeds a tenth or two quickly.

The serious fishing by trolling use a Fish Hawk device that provides temp and speed at trolling depth. No thru hull required it is simply lowered overboard to trolling depth. Usually set on a downrigger. Temp is a real key to finding many species of fish.

 

[koliver]

Sounders don't need a thru hull.
Mine gives me depth and temp, in a 4" ABS pipe epoxied to the inside of the hull.
I still have a paddle wheel, but the sounder/speedo that used it failed 20 or more yrs ago. One day I might remove it, but my haulouts are usually too short and it is low on the list.

 

[Blissboat]

In my offshore sailing days. a knotmeter was sometimes useful. For example, on an offshore trip up the east coast of the U.S., it was interesting and helpful to compare the knotmeter's record of speed through the water with the Loran's SOG. The delta between those two values, sometimes nearly 3 knots, was the approximate speed of the current, telling me when I was in or near the axis of the Gulf Stream current, and getting the maximum push.

My first time sailing out of Woods Hole, MA into Buzzard's Bay on a flood tide, it was fascinating to this Floridian to see the knotmeter indicating 6.5 knots through the water while the Loran showed something like 11+ knots SOG. Hell Gate in the East River (NYC) was similar.

But those situations are kind of novelties. In most situations, the electronic measure of SOG is plenty of information and needs no hull penetrations. I say forget about the knotmeter.

 

[psneeld]

No need for cruising or fishing and I have done plenty of both.

Important nfo? Yes occasionally...but really not hard to guess accurately enough.

 

[Lou_tribal]

Cruising on rivers I like to know current speed, just to learn where the current is stronger/weaker. Is it essential? No.
Now with experience with my boat I know its speed when no current at given RPM so not really need it.

L