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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

New Instrumentation Recommendations?

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MurphyPeoples
1st Mate

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USA
45 Posts

Initially Posted - 06/21/2009 : 06:09:18

Guys -
The 8" or so circular instruments that have been on my C-25 since forever, are non functional. The original knot indication paddle wheel has been pulled and pluged into the hole. And though it "might" work... I want to use current technology for speed indication. All I need for lake sailing is a depth finder and a knot meter. Has anyone here found a replacement that would fit into the original cut holes in the hull? Every GPS oriented instrument I've looked at is square and mostly meant to be mounted on brackets in a power boat. Seems like someone would have thought of the millions of boats with these circular holes, and thought up a replacement to fit into them. If you've used one, let me know what you think. I'm guessing I might have to resort to fiberglassing up the old holes and mounting a new square GPS.

Speaking of GPS - why are they all "Fishfinders"? Don't they know that some of us are only interested in depth?
Murphy

Edited by - MurphyPeoples on 06/21/2009 06:10:43

islander
Master Marine Consultant

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USA
4024 Posts

Response Posted - 06/21/2009 : 07:59:48

Murphy, A photo would really help. It seems everyones boat is different as to the instruments that were used through the years and the locations (port/starboard) My depth meter is a Standard Horizon DS150 and replaced the original round one . It is 4.4" square and covered the existing round hole. I use the Garmin 545 for my speed and charts.Its mounted on a Ram swing mount. Swings into the cabinflush with the wall when not in use.

Edited by - islander on 06/21/2009 08:04:57

MurphyPeoples
1st Mate

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USA
45 Posts

Response Posted - 06/21/2009 : 09:37:03

Islander- your 4.4 holes are exactly where mine are. Very Nice!
Does that Garmin operate even with the Bimini up over it?
Murph

Edited by - MurphyPeoples on 06/21/2009 09:37:36

ddlyle
Captain

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302 Posts

Response Posted - 06/21/2009 : 09:41:42

Hi Murphy,
Consider plugging the round hole (when you remove the imoperable instrument)with a (round) block of wood that you would mount the depth sounder onto or the GPS onto.
Perhaps the instruments would mount there only when you're sailing, and when you're away from the boat you would unplug the instruments and stow them below. You could bring the power supply in through the wood plug possibly.
Keeping your instruments below (when not sailing) helps them survive the sun better.

We're voyeurs ... wanna see pictures of your pretty boat.

Edited by - on

islander
Master Marine Consultant

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USA
4024 Posts

Response Posted - 06/21/2009 : 09:56:53

The Garmin has internal antenna. The bimini doesn,t interfere at all with GPS antennas only a hard top would.

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 06/22/2009 : 06:49:36

Murphy, what brand are your originals?

If they are SR Mariner, the company will still service them and bring them back to "like new." I have had my full set rebuilt for a fraction of the cost of buying replacements.

Of course they aren't sexy digital readouts that you can hook up to your computer, record second by second outputs, and re-live the race afterwards, but the SR stuff is reasonably decent for my needs.

Edited by - on

MurphyPeoples
1st Mate

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USA
45 Posts

Response Posted - 06/22/2009 : 11:04:43

Anyone recognize these? They ARE the SR Mariner. Prospector, please tell me how you handled getting them fixed. I plan on doing the exact same that. The paddle wheel is already out from the bulkhead so I can send'em asap.
Thanks for that info!!!!!
Murphy

Edited by - on

bigelowp
Master Marine Consultant

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USA
1778 Posts

Response Posted - 06/22/2009 : 11:07:24

I recently replaced my original knot and depth with a Raytheon ST40 wind and separate depth system. I had a new panel made from plastic to cover the old plates but with proper sized holes for the new instrumentation, then bolted on so the back of each instrument comes through where the 4" opening was for the old. It looks fine and enables any brand/size instrument be used.

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 06/22/2009 : 11:17:11

Murphy, I'll send you an email. Basically you contact Corey at SR Mariner and ship the instruments off to him.

you will have to recalibrate your knotlog to your paddlewheel when you get it back on. Best done with a GPS in an area without currents or tides.

Edited by - Prospector on 06/22/2009 11:23:15

MurphyPeoples
1st Mate

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USA
45 Posts

Response Posted - 06/22/2009 : 13:56:48

BTW - What IS the max hull speed of a Catalina 25 Fixed Keel?
Murph

Edited by - on

Blue Nose
1st Mate

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67 Posts

Response Posted - 06/22/2009 : 14:26:26

Mine is a tall rig and the hull speed is 6.23 mph

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 06/22/2009 : 15:18:29

By GPS, or by paddlewheel?

Max theoretical hull speed is determined this formula: Hull Speed = (1.34) * (LWL)^0.5 where LWL is the length of wetted waterline.

1.34 * 22.2'^.5 = 6.3

Now some folks will swear up and down that they were going at 11.7 knots last Saturday. Likely their paddlewheel showed that if it was out of calibration, or they were on big seas, and got surfy. Likely their GPS showed that if they were riding a tidal stream.

Your max speed (exact) is a function of how many beers are in your cooler since ballast will lower the boat in the water, lengthening the wetted surface. Heeling does the same, but adds to leeway.

I think Blue Nose has it about right at something between 6 and 6.5, there have been times when my GPS has tickled 7, and on our lake there are no currents, but I am dubious of anything over 6-1/2.

Edited by - Prospector on 06/22/2009 15:22:24

MurphyPeoples
1st Mate

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USA
45 Posts

Response Posted - 06/22/2009 : 19:43:28

Prospector-
murphypeoples@charter.net

Thanks!

Edited by - on

Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 06/23/2009 : 11:43:59

I plugged the hole on my Catalina with a round stained glass window decoration. It added some color to the boat. I installed a nice fish finder it gave me 3 beams instead of the old depth meters one. I was able to see the fish, know the bottom composition and water temp. I used a GPS for speed since the wheel type knot meters all quit eventually. It's been a long time since then but I imagine the technology is even better now .

Edited by - on

Deric
Captain

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USA
408 Posts

Response Posted - 06/23/2009 : 15:50:22

I have a GPS/Fishfinder Garmin unit, and the sets on a RAM arm -- same as Scott's set up above. I place a speaker in the hole where once had the compass. The speaker is plugged into my Marine radio. The benefit of having the speaker facing in the cockpit allows me to hear the radio messages while about in the cockpit.

The hole on the port side used to hold a depth finder -- now it is a port hatch. It has a "sock" on the inside that allows me to place small tools or items. I wanted to make use of the spot but not commit to something expensive.

Deric

Edited by - on

OLarryR
Master Marine Consultant

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USA
3467 Posts

Response Posted - 06/23/2009 : 20:24:22

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 06/24/2009 : 07:02:42

Murphy, did you get my email?

Edited by - on

mlg3733
Navigator

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118 Posts

Response Posted - 06/24/2009 : 16:42:53

Hull speed of a Catalina 25 is 6.82 knots or 7.84 MPH (1.15)

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 06/24/2009 : 18:06:05

The simple hullspeed calculation that most of us use ignores many aspects of hull form. Most boats fall in the 1.2 -1.4 multiplier range, but its actual position within that range is difficult to pinpoint. Extreme hull shapes can fall outside that range - rowing shells can be less than 1.1 and barges can exceed 1.8. I suggest letting it rest and calling it around 6.5 to 7.

Edited by - on

Deric
Captain

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USA
408 Posts

Response Posted - 06/24/2009 : 18:38:01

hmm I thought I read somewhere the hull speed of the Cat 25 was 6.32.. maybe I misread the 8 as a 3?

Deric

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 06/24/2009 : 21:17:14

OK, call it a little over six. I doubt that there is any point in trying be closer than 0.5 kt, taking the number beyond 0.1 kt is pointless. I agree that its major value is in tempering extreme claims and reminding us that longer is usually faster. I'm happy at 4 - 5. A former powerboater changed to sail and wrote a book called <u>Cruises With Kathleen</u> and said in comparison, a really fast sailboat moves at dead slow. And that's all the hijacking I'll do.

Edited by - on

Voyager
Master Marine Consultant

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USA
5378 Posts

Response Posted - 06/24/2009 : 21:51:14

I've found that the practical max speed indicated by the paddlewheel knotmeter is no more than 5.8 kts, but it occasionally hits 6.0.

My handheld GPS units (I have a Garmin 72 and a Magellan Explorist 200) largely agree with one another and measure speed over ground or speed made good (SOG or SMG) which really depends on current. I've done as high as 8.5 kts on the GPS.

My mental calculation for estimating the speed of the current is to subtract GPS speed from knotmeter speed. While it's not always exact, this approach is accurate enough when I'm going up or down the river with or against the current.

I've retained the original round 4" knotmeter display and paddlewheel because they both work and provide pretty reliable data. It agrees with the GPS at slack tide.

I eliminated the depth meter because the transducer never worked reliably. I retained the 4" window housing, removed the old electronics and mounted my new 2" round Norcross Marine digital depth sounder display <i>inside</i> the old housing. This setup works fine for me.

Edited by - on

Voyager
Master Marine Consultant

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USA
5378 Posts

Response Posted - 06/24/2009 : 21:53:30

Another question, for those who have electronics mounted nearby the compass, how do you compensate for the deviation caused by magnetic materials in the gear and magnetic fields produced by the wires?

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 06/25/2009 : 06:45:28

Bruce...

When I sent the knotlog into SR for refurb this spring, Corey told me that it was reading 0.5 knots faster than the boat was actually moving. Something to bear in mind if you haven't had your knot meter recalibrated recently.

When read against GPS, my knot meter now reads 0.5 knots slower than GPS. I wonder if the PO had a different paddlewheel installed and the knotllog was calibrated to the paddlewheel. In any case, I think that recalibration of the knot log is a turncsrew on the back of the unit, but it isn't a big deal to me since I'm not using it for DR.

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 06/25/2009 : 07:24:02

As accurate as GPS is in location, it is much better at measuring change in location over time, i.e. speed. Unless you have a follwing current that travels with you, I suspect that your knotmeter is reading slow. The paddle wheel transducer and head may be matched, but the transducer's access to freely moving water may be compromised because of location. Many locations, especially to close to the bow or keel, can expose the transducer to turbulence, lateral flow, air bubbles, and eddies that cause error. The best process would be to calibrate it at known speeds on the boat, which may have been its previous state, but you could still have errors on different points of sail.

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