I reckon you've been reading too many sales brochures....
Why not take your external mount transducer, and try to shoot through
the hull with it in several places?
There have been innumerable notes on this topic.

You will likely find a pl;ace or two in the hull that gives
reasonable performance shooting through the hull, with it.

Then don't drill any holes at all. and fill up any you have with glass
epoxy. And sleep sound aboard

Brian w

On Tue, 5 Aug 2003 18:07:28 -0400, "Gary Warner"
wrote:

Ron,

Thanks for the answer but I *think* you and I are talking about
two different things. Unless I'm not catching what you mean.

This transducer is NOT a Shoot-Through-The-Hull type mounted inside the
boat. (Also called an "In Hull Transducer" ?? )

It IS a THROUGH-HULL type where there is an actual hole cut in the wood.
The transducer has a "mushroom" head on it and a "stem." The "stem" is
pushed through the hole in the hull and the mushroom head sets outside the
hull.

With this type there is not the concern of air-bubbles in the wood or in the
epoxy/sealant because the transducer head makes direct contact with the
water. (Though there are still concerns about bubbles that are IN the water
from a bouncing hull or the prop.)

What the directions seem to be concerned about is that because the stem of
the transducer is actuatlly going THROUGH the wood...if that wood swells it
might put too much phyisical pressure on the stem of the transducer and
physically break it.

That makes sense to me on a planked boat where the wood swells a LOT and
where the thickness of the wood is quite a bit.

My question is: Does the same hold true for 3/4" plywood? Seems to me that
A) Plywood hulls probably don't absorbe much water or swell much. And B)
the plywood being only 3/4" thick would not put the pressure on the
transducer like a 2" or 3" thick hull would.

Gary

Brian,

I haven't seen any of these innumerable notes of which you write...

But thanks...sounds like a good idea. I can build a little
holder for the trandsducer that will have it set still in the hull. If
it works someplace - Great. If not, I can always install it
through the hull later.

Any other tips (or links to info) on how to make this work?

Gary

"Gary Warner" wrote in message
...


Brian,

I haven't seen any of these innumerable notes of which you write...

But thanks...sounds like a good idea. I can build a little
holder for the trandsducer that will have it set still in the hull. If
it works someplace - Great. If not, I can always install it
through the hull later.

Any other tips (or links to info) on how to make this work?

Manufacturers make "pucks" into which transducers can be
placed, but that is generally for "through the hull" installations -
not sure if it would work for a wood boat - through the hull
that is. My guess is not if only because of the varying density
of the wood.

After that one contribution, I'm at a loss. The experience I
have with hull style transducers are for much larger vessels
(by a couple of hundred feet) that we generally talk about
here.

Later,

Tom

Thanks Tom,

I think my plan at the moment is:

A) Take my nylon mount-in/through-the-hull transducer and put
it in some kind of block of wood to see if there is any place
it will work. It very well may NOT work because of space between
it and the inside of the hull and/or because it won't work through
the ply wood.

B) If the above does not work I think I''m going to install the
nylon mount-in/through-the-hull and mount is through the hull.
I will leave a little extra space for the wood to expand (not
much).

Thanks,
Gary

Why not mount it on a bracket off the transom under the waterline?

"Gary Warner" wrote in message
...

Thanks Tom,

I think my plan at the moment is:

A) Take my nylon mount-in/through-the-hull transducer and put
it in some kind of block of wood to see if there is any place
it will work. It very well may NOT work because of space between
it and the inside of the hull and/or because it won't work through
the ply wood.

B) If the above does not work I think I''m going to install the
nylon mount-in/through-the-hull and mount is through the hull.
I will leave a little extra space for the wood to expand (not
much).

Thanks,
Gary

On Wed, 6 Aug 2003 13:25:54 -0400, "Gary Warner"
wrote:



Brian,

I haven't seen any of these innumerable notes of which you write...

But thanks...sounds like a good idea. I can build a little
holder for the trandsducer that will have it set still in the hull. If
it works someplace - Great. If not, I can always install it
through the hull later.

Any other tips (or links to info) on how to make this work?

Gary


People have described their tests like this:
1) with a water balloon, place the balloon on the hull, and the
transducer on the balloon.
Can you read the floor at a reasonable depth?
2) Using a dam of putty etc.inside the hull, , pour a little mineral
oil into the dam, and place the transducer level in the oil.
Test for depth reading etc.
3) Using a blob of RTV silicone on the hull, place the transducer in
it etc., etc.

These are not difficult, destructive or time consuming tests.
You MIGHT find some wood hull section that transmits the signal
sufficiently well. People have shot through composite hulls. Wood is
composite!
You have lost a few dollars if not.

Brian W

I haven't seen any of these innumerable notes of which you write...

But thanks...sounds like a good idea. I can build a little
holder for the trandsducer that will have it set still in the hull.
-------------snip-------------------------------

If you want to shoot through the hull you
need to fill the air gap between the
transducer and the hull with something
like mineral oil. the way it's normally
described is to build a little oil tight box
inside the hull, fill it with the oil, and mount
the transducer so it's face is even with
the surface of the water inside the oil
cavity.

You need this 'impedance match' to get
the sound through the hull. I know this
works well in a 'glass hull, but you
can try some of the other suggestions
in earlier appends.

Frank