In-hull transducer

NoRush · Post by **NoRush** » Sun Apr 29, 2007 4:50 pm

Has anyone mounted an in-hull transducer in a C26. I tested my new depth sounder at various points in the boat, but I am getting a false 2.5' reading.

I think the Chrysler is "cored" boat and I must drill to get to the exterior fiberglass.

Any tips or suggestions would be appreciated.

Jason
Astraeus

OldUgly · Post by **OldUgly** » Mon Apr 30, 2007 5:22 am

If you get the In-hull transducer working for you let us know. I need a depth sounder, but not excited about drilling another hole in the old ugly boat. Thnx

EmergencyExit · Post by **EmergencyExit** » Mon Apr 30, 2007 7:25 am

I recently rebedded my thru hulls for both depth transducer and water intake (under port banquette), as well as repaired a 3/8 hole between the winch and the port banquette caused by a drill ( no i don't want to explain further !)

I didn't find any coring in those areas, just about 3/8" of solid 'glass. Was suprised how thin the hull is there.

I did read an article where someone bedded a PVC pipe to the hull, placed the transducer in that, filled the pipe piece with water, and sealed it. That worked for them.

Windwalker · Post by **Windwalker** » Mon Apr 30, 2007 9:28 am

I have a humminbird depth sounder mounted just aft and about 1 foot to starbord of the rear bilge, under the cockpit, just under the plywood that gives you access to the bilge. I have had no problem with the readings. The hull is solid glass with no core (1978 C26). I have thru-hulls on starbord and port just behind the head (or had on the port side, just closed it up as this was the discharge for the head), also solid core.

I am planning to move the transducer to the bow to give me warning BEFORE I run out of depth. Lesson learned.

Windwalker · Post by **Windwalker** » Mon Apr 30, 2007 9:32 am

BTW, this is a through the hull transducer, not the type that needs a hole in the hull. It is epoxied on the inside surface of teh hul.

The instructions warned me to be careful about air bubbles in the epoxy, they could give a false reading. Could this be your problem?

NoRush · Post by **NoRush** » Mon Apr 30, 2007 3:49 pm

Thanks for the replies. Now I am a bit scared.

I tested the new transducer using a bag full of water in all the areas mentioned above and the best reading I got was 2.5'. The reading I got holding the transducer to the water's surface was 85'.

I will do some more research before drilling for water

EmergencyExit · Post by **EmergencyExit** » Mon Apr 30, 2007 6:10 pm

Hey, Try this, I found it in my marked web pages -

Get a wax toilet bowl ring, pull the wax away from the center plastic piece, and mush it into a ball, make sure it is solid.

Press that into the hull making a pancake about inch and a half thick, then press the tranducer halfway down into the center of the wax. Be sure no bubbles/voids exist.

Good Luck !

Windwalker · Post by **Windwalker** » Tue May 01, 2007 4:08 am

Good suggestion with the wax! The instructions included with my transducer were to test it with the transducer in water in a partially flooded hull, the transducer in the water inside the hull. You need a denser media then air to transmit the ultrasound waves. You could build a dam with the wax ring, fill the cavity with water and put the transducer in the water to test. If you are trying to test by pushing the transducer against the hull surface, that may be the reason for the error.

Good Luck, let us know how you make out.

EmergencyExit · Post by **EmergencyExit** » Tue May 01, 2007 12:27 pm

In the article they just used the wax to be a pliable voidless go between for the inner hull and the transducer face.

Question - how clean is the bottom of the boat ? I bet if it has growth on it, the "perfect" echo return needed from the transducer would be hindered.

Also where you got the reading in the water of "85'", did you mean 8.5 feet ? Or is the water actually that deep there.
(ie is the depth gauge reading right)

Gus · Post by **Gus** » Tue May 01, 2007 12:38 pm

Why epoxy? I used 4200 to glue the transducer to the hull. Before placing the ducer, I used my drill with a wire brush to remove growth, and I followed with a nice deep cleaning with acetone.

NoRush · Post by **NoRush** » Tue May 01, 2007 4:19 pm

Thanks for the tips. I will give the wax idea a try this weekend.

Yes 85' is accuarate in the marina.

Could be a bit of a growth issue, but it seems most of the growth is on the water line.

I will let you know how it goes.

Jason
Astraeus

Archy · Post by **Archy** » Tue Jul 17, 2007 8:14 pm

EmergencyExit wrote:Hey, Try this, I found it in my marked web pages -

Get a wax toilet bowl ring, pull the wax away from the center plastic piece, and mush it into a ball, make sure it is solid.

Hi folks -

I just bought a similar Hummingbird device. Pardon my ignorance vis a vis household plumbing, but what the heck is a wax toilet bowl ring??

I put the bottom paint on today ... bought a battery, picked up my 1980 Sailmaster from the shop ... now I'm just waiting on the yard manager to give me to go ahead to launch!!! Smiley should be in the water soon.

cheers!

Archy

EmergencyExit · Post by **EmergencyExit** » Wed Jul 18, 2007 2:16 am

It is the seal between the toilet and the floor and the plumbing, like a gasket. The "wax" is dense, but pliable, and quite sticky.

Here's a link to a pic

http://www.hammerzone.com/archives/bath ... eplace.htm

Beau

Patrick · Post by **Patrick** » Wed Jul 18, 2007 5:44 am

Hi Guys , I have tried this ... pretty messy , then I tried the blue stuff that is use for putting poster on wall , better but the transducer would not work , I finally put out of the boat where it is supose to go and it work well

EmergencyExit · Post by **EmergencyExit** » Wed Jul 18, 2007 7:00 am

Just curious - did the transducer work with the wax ring ?

Archy · Post by **Archy** » Wed Jul 18, 2007 7:16 am

Patrick wrote:Hi Guys , I have tried this ... pretty messy , then I tried the blue stuff that is use for putting poster on wall , better but the transducer would not work , I finally put out of the boat where it is supose to go and it work well

Salut Partick!

I have a question too. Did you drill holes in your transom to mount the transducer (like it says to in the instructions) ?

I really feel on Lac St Louis I'm going to need htis sounder!!

Cheers and thanks for your help.

Archy

Patrick · Post by **Patrick** » Wed Jul 18, 2007 8:25 am

No , I have read that transducer that was desing to be install outside the boat could work if there was no air "entre" ..."betew" ( sorry serching the rignt english word) the transducer and the hull , so I tried and it fail .So I put were it belong ...outside .

NoRush · Post by **NoRush** » Sun Jul 22, 2007 6:49 pm

I haven't had a chance to try the wax ring idea, but I am still planning on tackling it. I've been spending too much time playing and not working at the boat.

Someone above mentioned mounting transducer on the transom, any suggestions on this. My transom does not reach the water.

Thanks again, will keep everyone posted on the progress.

Jason
S/V Astraeus
1980 C26

Windward · Post by **Windward** » Tue Jul 24, 2007 6:03 am

The Chrysler 26's hull is not cored, so no worries there.

I have a Humminbird Piranha Max 15 with a transducer that was designed for transom mount, and used epoxy and PVC pipe to install it beneath the port settee, just aft of the head. No holes in the hull, and works perfectly.

I began by testing the unit, holding the transducer just submerged outside the boat to get a baseline reading

Cut a piece of PVC pipe large enough diameter to comfortably hold the transducer at an angle matching the slope of the hull, so that the top was level when it sits on the hull.

Washed the area, sand and wipe down with acetone.

Use a hot glue gun to stick the PVC base to the hull. Then use blue tape as a temporary flange to better seal the joint, because epoxy can heat up enough to re-melt the hot glue when it kicks.

Be sure you have a power hookup for the head unit, because you'll want to test before everything's permanent.

Mix up epoxy thoroughly but gently, to avoid aerating it and introducing bubbles. Then give it a few minutes to collect itself and lose any bubbles.

Paint the hull at the bottom of the PVC with epoxy to ensure you have good adhesion to the hull and no bubbles. Then gently pour the epoxy into the PVC tube. You need just enough to permit it to level off, not fill the tube. Doing this in several batches will help keep it from going spectacularly exothermic, but increases possibility that bubbles will be introduced.

While waiting for the epoxy to set, hook up the transducer to the head unit to be sure it still works (you'll probably get 0 for depth), wipe off the bottom of the transducer, and make sure you know which was is forward. I'm not sure it matters, but no reason to take chances.

When the epoxy's set but not fully cured, carefully and gently mix up another small batch, paint the bottom of the transducer with it and pour a bit on top of the set epoxy in the tube. Gently press the transducer down into the epoxy and work it around to squeeze out any air bubbles.

Immediately turn on the head unit and see what you've got. You should see a depth reading that's pretty close to the baseline you took from the surface. If you don't get an accurate reading, try repositioning a bit. You can still back out here by removing the transducer and wiping the epoxy off with acetone.

I initially anticipated that I'd show less than actual depth, since I had installed below the waterline. I calibrated by leaving the keel all the way down and slowly (.1 kt or less) motoring to the ramp. When the sounder registered 6 feet, I felt a gentle bump. Since the C26 is reputed to draw about 6'2" with the keel down, I was more than satisfied. I think that perhaps shooting through the hull and epoxy alters the response for the transducer a bit, with the happy effect of perfectly adjusting the offset in my case.

Fair Winds,

Jeff

Archy · Post by **Archy** » Tue Jul 24, 2007 8:24 am

Hi Jeff -

Thanks a million for the detailed instructions. I will do the wiring of my new boat in a couple of weeks and will want to install my new Hummingbird 215 as well.

The "lake" here isn't very deep in most spots so it would be good to have a little help besides my chart.

Happy sailing!

Archy

Gus · Post by **Gus** » Tue Jul 24, 2007 9:32 am

I tried to make a BottomLine fishfinder to work inside the hull. The unit works fine if I put the puck inside a water back, I can get readings back. Inside the boat, won't work. I tried everything, the PVC with baby oil, gluing the puck to the hull with silicone, the water back (works sometimes) last I tried, epoxy the puck to the hull. One time I took the puck outside the boat, hold it in the water, and didnt work neither.
Frustrating as it is, I feel I don't need a depth finder. The swing keel makes it easy to get unstuck, and I usually follow the depth using a chart.

Gus

Windwalker · Post by **Windwalker** » Tue Jul 24, 2007 2:31 pm

The question was asked a while ago as to why epoxy and never answered. If you mount the transducer outside the hull anything will work, but inside the hull, i.e. through the hull (as apposed to thru-hull), you need a media that will transmit sound efficiently without absorption. This means no flexibility. Epoxy transmits the sound waves better then almost anything else. It's rigid and should be close to the density of the hull itself.

The important thing is to make sure the media the transducer is transmitting the sound waves through has as few transitions as possible. Changes in density will dissipate sound energy and may prevent the depth sounder from working altogether. This is why it is very important to get ALL of the air out from between the transducer and the hull.

I also have a in-hull transducer, also a Hummin Bird, and it works very well in my 78 Chrysler 26. The transducer is epoxied about 1 foot below the waterline to starboard and aft of the rear bilge.

The wax ring may work, but your sound energy will be dissipated some, so the depth sounder may not be able to read as deep as it would with a ridged or outside mounting. This should not be a problem for most of us that use the depth sounder as a warning for shallow water.

Use what works for you. (this is probably a mantra for most sailors)

Gus · Post by **Gus** » Tue Jul 24, 2007 3:06 pm

Where are you located in NC?

p/s I did the epoxy thing last week, but I didn't have the chance to tested in the water yet.

Gus

Windwalker · Post by **Windwalker** » Tue Jul 24, 2007 3:08 pm

Kerr Lake, Steele Creek Marina

Gus · Post by **Gus** » Tue Jul 24, 2007 3:10 pm

oh cool. I'm south of you, I mostly sail in Jordan or the coast.

Windwalker · Post by **Windwalker** » Tue Jul 24, 2007 3:17 pm

Gus,

You sound local. Physically, I live in Wake Forest.

NoRush · Post by **NoRush** » Mon Sep 03, 2007 11:35 am

Finally complete!!

I want to thank everyone for thier input on this. I ended up using a slow cure epoxy in a pvc pipe, mixing enough batches to compensate for the angle of the hull.

Thanks again

Jason
S/V Astraeus
1980 C26

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