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Date Posted: - Friday - 02/ 6/09 - 11:10pm
Author: Dan M32 #36 Independence
Subject: Thru hulls
In reply to: Lyle Harris 's message, "Thru Hull Replacement Question, M31" on - Thursday - 02/ 5/09 - 1:37pm

What about depth sounder transducers and knot meter sending units? More holes in the hull? My M32 came with a big chunk of wood that the depth sounder sending unit is mounted in. It sticks out from the hull alot and isn't very fair. I assume that this was not original. Were depth sounders and knot meters original equipment? How are the sending units mounted on your boats?
Dan

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Replies:

[> [> Thru hulls -- Kathy Campbell SHADOW M32-#3, - Saturday - 02/ 7/09 - 1:54pm

Dan, I remember your boat then it was for sale. I didn't know the trailer that went with it was such a nice one. Like George Muller, don't sell the trailer without the boat. I would have bought it if I didn't already have a boat. Anyway, Shadow has a BIG chunk of wood on the port side which had an old Ocean navigator depth sounder. After 24 years of dragging this chunk of wood under the hull- it's out of here. A lead line will always work, but they have some pretty nice, flush thru hulls. One that looks like it would work is the Airmar's KW B164 (tilted thru-hull. Price is a problem with it. www.airmar.com.

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[> [> thru hulls -- Dan M32 #36 Independence, - Saturday - 02/ 7/09 - 2:47pm

Kathy,
Sounds like we have the same setup, maybe that was how they were sold. Seems a bit mickey mouse. I,m thinking about fairing in a small more or less level flat place to mount the two sending units in.
It was a nice trailer. George let me use it to haul the boat from Salt Lake to San Juan Island and in exchange I then found a buyer for the trailer. A guy From Atlanta,Ga. flew out to Seattle, bought an old 1 ton truck and pulled it back.
Dan

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[> [> [> Airmar in hull transducer -- Jared Kibele, - Monday - 02/ 9/09 - 5:11pm

I just installed an Airmar in-hull transducer. It was under $100, glued to the hull with a silcone sealant, and works great with my Garmin sounder and chartplotter. Here's the airmar link: http://www.airmartechnology.com/airmar2005/ex20/RMProducts/ElectCat.asp?ProdID=52&Man=All&PageNo=99

That being said, you may be able to use your old transducer with a new sounder. ...it depends on how old the transducer is. Most of them are dual frequency these days.

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[> [> [> [> Wow. That's cool -- Randall, - Monday - 02/ 9/09 - 7:40pm

I don't see anywhere a spec for the thickness of hull it can pass through and worry when it says "good for racing sailboats up to 25'". Thin hulled little bastards! But you're using it, so all must be good, no? Where did you position it?

My issue is more w/the readouts. Either they have gotten smaller or my eyes are less strong, but at night I can barely make out what they're telling me. So it's time for an upgrade...at least in font size!

Anyone use the "new wireless" units?

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[> [> [> [> [> Thick hull -- Jared Kibele, - Thursday - 02/19/09 - 11:41am

Hi Randall. I mounted my transducer under the aft-most drawer in the port settee. It turned out that was the only place I could find a 22 degree or less deadrise angle (this model of transducer can mount on a surface with 0 - 22 degrees). From my understanding, hull thickness shouldn't really matter. Sonar signals have problems crossing boundaries between different types of material but shouldn't attenuate much based on the thickness of the fiberglass. So a thick solid fiberglass hull works fine but a thin cored hull wouldn't work.

My transducer is hooked into a garmin sounder box (gsd 22: https://buy.garmin.com/shop/shop.do?pID=288) and the sounder is hooked to a garmin 4208 chartplotter (https://buy.garmin.com/shop/shop.do?pID=8113). The 4208 also works as my radar display. You can display the depth soundings in a whole slew of different ways. The whole mess is also hooked up with my autopilot.

...I went a little nuts with the electronics. I like that stuff.

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[> [> [> Depth sounders -- Dan M32 #36 Independence, - Tuesday - 02/10/09 - 1:20am

I'm with you Randal in reguards to the small display size.I recently put a Humminbird sounder in my San Juan 24 and it's about 2" in dia. and it's hard to read sometimes. It replaced a 5" dia. Standard Horizon that stopped working after only 6 yrs. I wanted to replace it with one the same size but apparently all the instrument makers got together and decided it would be funny if they stopped making 5" dia. to see what people would do with all tose 5" holes in their boats. I had to make a plastic filler for the hole. I think the 2" instruments are intended to go in a dashboard like on a powerboat. Anyway the transducer is a glued in hull type. I've only used the boat a few times since installing it and I've gotten some wacky readings. The old one was a Standard Horizon with a in hull transducer that was in mineral oil and it worked great until it stopped. I was considering going to a fishfinder but they're all rectangular and not made to go in a bulkhead. Looking on line for depth sounders recently( I'm starting to research all the things I'll need for my Mariner ) I noticed there is a lot of transducers for sale w/o the instrument so I guess some must be interchangable as long as they work on the same frequency. I also noticed that some are made with the transducer at an angle in the thu hull which is good but they are expensive. One more thing while I'm venting, why do alot of the new sounders read in tenths of a foot? Why could it possibly matter that it's 276.3 ft. deep?
Dan

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[> [> [> [> Ha! Tenths of feet -- Randall, - Tuesday - 02/10/09 - 1:51am

Thanks Dan. It's funny to be learning about many things--including eye site--from Murre. Only a couple years ago and while working in tight quarters, I noticed that I couldn't quite see the fastener nor the hole I was attempting to guide it into. I thought at first I'd inhaled too many epoxy fumes. But then Joanna reminded me I'm over 40. One can always depend on Joanna for the important stuff--like putting me in my place.

Wacky readings? I get those from my through hull unit...due to really muddy water...transponder out of the water, etc. But what do you mean by whacky?

Tenths of feet. That's funny. Now, let's see, I draw 3.8 feet and the depth is 276.3, so how many tenths of minutes till I run aground?

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[> [> [> [> [> thru hulls -- Dan M32 #36 Independence, - Tuesday - 02/10/09 - 12:40pm

Randall,
By wacky readings I meant that as I was sailing the soundings seemed ok and then they would fluctuate wildly. I knew It wasn't reading the bottom accurately. I never had that problem with any of the other sounders on any of my past boats. I know that in certain circumstances sounders will jump around. When I was sailing from Panama to Equador last June on a Passport 40 the sounder would occasionaly show 50 or 80 feet but we were 300 miles off shore. The captain said it was temp. changes. I just not ready to trust the new sounder yet. I think a hole though the hull is probably the best for a transducer.
Dan

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[> [> Murre's bum with transducer -- Randall, Murre, M31, - Monday - 02/ 9/09 - 1:42am

Murre's depth sounding and knot meter units are a little different. A couple photos from below are attached. They are both on the port side, both accessable from the port settee. Both are pretty flush. I've not done anything with them, so don't know anything beyond that.

But that does lead to a question of my own. I want to change out the knot and depth meter read-outs in the cockpit. Will I need to change the underwater units as well? Or can I simply plug in new read-outs into existing stuff?

click to enlarge.

From the side:

from below:

Quickpost this image to Myspace, Digg, Facebook, and others!title="QuickPost">

Quickpost this image to Myspace, Digg, Facebook, and others!

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[> [> [> transducers and thru-hulls -- Lyle Harris, - Monday - 02/ 9/09 - 4:42pm

HI Randall,
Don't know if it's helpful, but there are transducers that you just epoxy to the inside of the hull below the waterline, and don't make any penetrations. That may be one way to go.
I ended up using something like this on my current in-the-water sailboat because the depth finder was shot and I couldn't find anything compatible with the existing transducer.
Lyle.

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[> [> [> [> depth meter transducer -- Ardian, - Monday - 03/23/09 - 10:16pm

I installed the transducer inside the hull and it does work great since 2-3 years .I bought a hummingbird matrix 12 . To start i did build the dam that will hold the resin . so , i did cut in a form of triangle a piece of cartoon and used epoxy resin in to almost vertical sides to glue it to the hull . Of course after i cleaned the hull from the paint and dirt . Once cured i mixed the resin with a very slow hardener so the air bubbles created from mixing it will be gone by the time it cure .Because the air bubbles will create problem if there. sink the transducer but be careful that it must not move till it cures and also i place it facing fore a few degress . And the next day was done. Just be careful because not all the transducers work from inside the hull. Hope that this will help . Good luck. Ardian.

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[> [> transducers an sounders -- Kathy Campbell SHADOW M32-#3, - Monday - 02/ 9/09 - 10:49pm

OK, Here it is from the lead line specialist. There was an article in December SAIL magazine ' SOUNDER ROUNDUP '08. They tested sounders an transducers. It was brought out that impedance has to be matched between the transducer and the sounder to get the best readings. M-A-R-K twain, Kathy

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[> [> [> Final note on Thru-Hulls -- Lyle Harris, - Tuesday - 03/10/09 - 1:14pm

Follow-up to how many thru-hulls below the waterline on an M31... I'd originally thought there would be three thru-hulls below the waterline to replace. Turns out there were six. I'm fairly certain this was the original configuration for the M31. There are three in the Head, and three in cockpit area.
The cockpit drains and head (toilet)drain are all 1.5 inch size. The toilet saltwater intake and head sink intake are 3/4 inch, and the engine raw-water intake is 1 inch. All thru-hulls were mushroom-flanged bronze.
I suppose it could be different for other boats, but this is what I found.
Lyle.

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