I just received my new depth finder and transducer in the mail. After
asking on newsgroups, reading Chapman's, and some West advisories I decided
on the Nylon Flush Mount thru-hull transducer.

The instructions that came with it say NOT to put it through a wood hull as
the swelling of the wood could stress/crack the transducer.

This boat is a lap-strake PLYWOOD boat. I know that planked boats swell a
lot to close/seal the gaps and calking. Do plywood boats swell much?? I'm
thinking they don't?

Is it OK to use this nylon transducer or should I send it back and pony up
the bucks for the bronze one?

Thanks,
Gary

Gary,
The 'supposed' reasons for the caution about wood {as well as using RTV
Silicone as an adhesive}is the possibility of getting an air 'bubble' or
'gap' interfering with the ultrasonic 'beam'.

By inference, if you *knew* that a particular piece of wood would ALWAYS be
WET {as in 'saturated', theoretically that placement would work !. "They"
also advise against RTV for the same reason. HOWEVER, I used a 10.5 ounce
tube and 'gunned' a tight spiral of the stuff on my 'in-hull' transducer,
gently 'squished it into place in the forward section of my 1989 West Wight
Potter 19 . . . and it WORKS like a charm !! {it changes by TENTHS of a foot
as I ride the wakes on my mooring !!}

My advice, FWIW, would be to do the same thing. (I am *guessing* that the
comments you have received - noting the ' . . .could stress/crack the
transducer' comment - are assuming the *permanent, epoxy in place* method of
placement. No matter what 'they' say about the 'impermanence of RTV - I have
had the misfortune to find out that it CAN 'stick' just as well as 5200. I
actually BROKE THRU a cabin top to remove a hatch slider that I had
installed with RTV!! {I had done the job about 5 years before, and DIDN'T
want to use a wire to 'slide/cut' it off due to the gelcoat}. In your case,
if it didn't work {the instrument would give fluky readings} it would be
fresh enough to easily remove, or you could use the 'cheese wire' technique
because any surface damage would be either hidden or easily repaired.

Let me know if you want me to 'talk you through it', or discuss the
situation in more depth.

Regards & Good Luck,
Ron Magen
Backyard Boatshop

"Gary Warner" wrote in message
...

I just received my new depth finder and transducer in the mail. After
asking on newsgroups, reading Chapman's, and some West advisories I
decided
on the Nylon Flush Mount thru-hull transducer.

The instructions that came with it say NOT to put it through a wood hull
as
the swelling of the wood could stress/crack the transducer.

This boat is a lap-strake PLYWOOD boat. I know that planked boats swell a
lot to close/seal the gaps and calking. Do plywood boats swell much??
I'm
thinking they don't?

Is it OK to use this nylon transducer or should I send it back and pony up
the bucks for the bronze one?

Thanks,
Gary

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

Gary,
I stand corrected.

FWIW, if it were MY decision I would go with the Bronze; because it's, well
.. . . BRONZE !! {kind of matches my personality . . .}

All joking aside, if ANYTHING penetrates the hull {wood OR 'plastic'} I want
it to be the strongest possible material. Something that is 'plastic' or
Nylon can be shattered or fractured if it is struck . . . have you seen what
can float, just submerged, after a big storm ? In addition, anti-fouling
paints easily 'attach' to Bronze fittings. I'm not sure about barnacles &
Nylon, but I DO KNOW that 'slime' & algae WILL cover Nylon quite rapidly.

However, if you already have the Nylon transducer and want to use it, here's
how I would proceed. Make the penetrating hole about 1/4 inch LARGER than
the diameter of the part that will go THROUGH. Coat the cut edge with epoxy,
let it soak in a bit, then apply more, plus some fine weave Fiberglass cloth
{an overlapping 'collar'} this will SEAL the wood from water penetration,
plus stabilize the area. There should STILL be some 'slop' in the fit. After
it 'cures' for about a week, clean the area with warm water and a bit of
liquid soap, rinse well & dry. {this will remove any Amine 'blush'. 'Gun' a
LOT of RTV around the 'mating face' of the transducer {typically they are
inserted from the outside of the hull}. Carefully insert it - CENTERED - in
the opening. You want a LOT of 'squeeze out' up through the opening.
Carefully snug down the interior 'flange; NOT all the way - just get a good,
even 'squeeze out'. Let the RTV 'cure' for about 24-hours. NOW tighten up
the interior 'flange' and trim off the excess. You now have a 'Custom Fit
Flexible Silicone Rubber Seal' .

The wood is sealed from water inclusion by the epoxy/glass 'collar'. If
there is any slight movement or pressure, it will be absorbed by the RTV
Silicone 'gasket', rather than cause a 'point loading' on the transducer.
Paint won't 'stick' to the Silicone, but it comes in Clear, White, and I
think - Black.

Let me know what you think, or if you want clarification.

Regards & Good Luck,
Ron Magen
Backyard Boatshop
{who has put Bronze chocks on his foredeck, and a 7 inch Bronze cleat for
the mooring pendant}

"Gary Warner" wrote in message
...
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.
SNIP

Now we're on the same page.

I've go to reread your post again to see
if I have any questions or concerns.

Again, Thanks!
Gary

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

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

Other than cost, is there any reason why you chose the plastic over the
bronze? In your case, I understand that you have a wood hull and are concerned
about stress cracking but I have never seen a good explanation on why you would
use a bronze transducer over plastic on a fiberglass hull, yet bronze seems to
be more popular.

Gary Warner wrote:

I just received my new depth finder and transducer in the mail. After
asking on newsgroups, reading Chapman's, and some West advisories I decided
on the Nylon Flush Mount thru-hull transducer.

The instructions that came with it say NOT to put it through a wood hull as
the swelling of the wood could stress/crack the transducer.

This boat is a lap-strake PLYWOOD boat. I know that planked boats swell a
lot to close/seal the gaps and calking. Do plywood boats swell much?? I'm
thinking they don't?

Is it OK to use this nylon transducer or should I send it back and pony up
the bucks for the bronze one?

Thanks,
Gary