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