Does anyone have any direct experience with how well 5200 sticks to
old but cleaned up fiberglass?

I have to put a new backing block in for a through hull in a very
awkward location. Since it’s a Signet Knotlog, it has to be flush and
there isn’t much back up in the taper for a direct hit on some
floating object. I’d like the back up block to be actually backing it
up.

Building up with fiberglass and epoxy working through a hand sized
opening is going to be tough. I’m wondering if a larger than normal
sized plywood backing block done with 5200 might not be nearly as
strong.


--

Roger Long

On Mon, 27 Mar 2006 20:12:44 GMT, "Roger Long"
wrote:
Does anyone have any direct experience with how well 5200 sticks to
old but cleaned up fiberglass?

I have to put a new backing block in for a through hull in a very
awkward location. Since it’s a Signet Knotlog, it has to be flush and
there isn’t much back up in the taper for a direct hit on some
floating object. I’d like the back up block to be actually backing it
up.

Building up with fiberglass and epoxy working through a hand sized
opening is going to be tough. I’m wondering if a larger than normal
sized plywood backing block done with 5200 might not be nearly as
strong.

I had a pair of Signet transducers on my old Cal-34 with no backing
blocks at all. I'd estimate the fiberglass thickness at about 3/8 in
or perhaps slightly greater, taper was about half the thickness as I
recall. Never had any strength issues.

That said, 5200 is tough stuff and would probably be fine.

Roger Long wrote:
Does anyone have any direct experience with how well 5200 sticks to
old but cleaned up fiberglass?

I have to put a new backing block in for a through hull in a very
awkward location. Since it’s a Signet Knotlog, it has to be flush and
there isn’t much back up in the taper for a direct hit on some
floating object. I’d like the back up block to be actually backing it
up.

Building up with fiberglass and epoxy working through a hand sized
opening is going to be tough. I’m wondering if a larger than normal
sized plywood backing block done with 5200 might not be nearly as
strong.



Talking about putting holes in your hull.
I'm trying to decide if I should buy a thru hull transducer.. or an
in-hull transducer for a depth sounder.
If I could feel sure that accuracy is similar, the in-hull might be
better for a trailerable sailboat...re all that loading & unloading over
rollers/bunks (& occasional beaching).

The in hull transducer on my boat works great. It's just slapped on
the inside of a fairly thick hull.

I can't imagine putting a hole in a hull if you don't need to.

--

Roger Long



"Don White" wrote in message
news
Roger Long wrote:
Does anyone have any direct experience with how well 5200 sticks to
old but cleaned up fiberglass?

I have to put a new backing block in for a through hull in a very
awkward location. Since it’s a Signet Knotlog, it has to be flush
and there isn’t much back up in the taper for a direct hit on some
floating object. I’d like the back up block to be actually backing
it up.

Building up with fiberglass and epoxy working through a hand sized
opening is going to be tough. I’m wondering if a larger than normal
sized plywood backing block done with 5200 might not be nearly as
strong.



Talking about putting holes in your hull.
I'm trying to decide if I should buy a thru hull transducer.. or an
in-hull transducer for a depth sounder.
If I could feel sure that accuracy is similar, the in-hull might be
better for a trailerable sailboat...re all that loading & unloading
over rollers/bunks (& occasional beaching).

Roger Long wrote:
The in hull transducer on my boat works great. It's just slapped on
the inside of a fairly thick hull.

I can't imagine putting a hole in a hull if you don't need to.

I experimented with shooting through the hull, and directly by
dangling the transducer over the side prior to permanent installation.
Shooting through the hull reduced the maximum range of the depthsounder
by about 25%. The solid FG hull thickness was about 5/8". A yard guy
said experiment with exact placement if you do shoot through the hull,
as a void or dry spot in the laminate directly below the transducer can
reduce the maximum range by a lot.

One good thing you can do with a shoot through the hull setup is orient
the transducer so it points straight down on a curved hull surface, by
using an adjustable mount (available from manufacturer) which immerses
the transducer in mineral oil. The gizmo is a tube with an angled
flange on the bottom which is glued (with 5200) to the hull, and a
sealing threaded top for the transducer.

My through hull mounted transducer is flush on a curved part of the
hull, about 20 degrees out of plumb, so I get greater range on the
tack which plumbs the transducer. When heeled 30 degrees on the "bad"
tack, the maximum range drops by over 50%. This is with a high
frequency 200khz trandsucer which has a fairly narrow emission cone;
the effect should be less with a 50khz transducer, as its emission cone
is wider.

Oh, and it's an inexpensive depthsounder with a rated maximum range of
200 feet.

Excellent point on the range. I'd forgotten that might be important to
many people. I only worry about the last few feet, myself.

I checked mine with a sounding line for some bottom survey work I was
doing as Harbormaster and it was as accurate as I could determine when
upright.

--

Roger Long



"Mark" wrote in message
oups.com...
Roger Long wrote:
The in hull transducer on my boat works great. It's just slapped
on
the inside of a fairly thick hull.

I can't imagine putting a hole in a hull if you don't need to.

I experimented with shooting through the hull, and directly by
dangling the transducer over the side prior to permanent
installation.
Shooting through the hull reduced the maximum range of the
depthsounder
by about 25%. The solid FG hull thickness was about 5/8". A yard
guy
said experiment with exact placement if you do shoot through the
hull,
as a void or dry spot in the laminate directly below the transducer
can
reduce the maximum range by a lot.

One good thing you can do with a shoot through the hull setup is
orient
the transducer so it points straight down on a curved hull surface,
by
using an adjustable mount (available from manufacturer) which
immerses
the transducer in mineral oil. The gizmo is a tube with an angled
flange on the bottom which is glued (with 5200) to the hull, and a
sealing threaded top for the transducer.

My through hull mounted transducer is flush on a curved part of the
hull, about 20 degrees out of plumb, so I get greater range on the
tack which plumbs the transducer. When heeled 30 degrees on the
"bad"
tack, the maximum range drops by over 50%. This is with a high
frequency 200khz trandsucer which has a fairly narrow emission cone;
the effect should be less with a 50khz transducer, as its emission
cone
is wider.

Oh, and it's an inexpensive depthsounder with a rated maximum range
of
200 feet.

On Tue, 28 Mar 2006 10:19:09 GMT, "Roger Long"
wrote:

Excellent point on the range. I'd forgotten that might be important to
many people. I only worry about the last few feet, myself.

The range effect comes into play in other ways. I used to sail in a
shallow bay where the bottom was mostly very soft mud, which doesn't
return a particularly strong signal. With an internal transducer, I
often lost the signal entirely until I got back over hard sand. To be
sure, it was a crummy installation: one of those plastic bubbles
filled with mineral oil and the transducer monted at the top. I think
the transducer mounted directly to the hull would have been better.
__________________________________________________ __________
Glen "Wiley" Wilson usenet1 SPAMNIX at world wide wiley dot com
To reply, lose the capitals and do the obvious.

Take a look at cpRepeater, my NMEA data integrator, repeater, and
logger at http://www.worldwidewiley.com/

Mark wrote:
Roger Long wrote:

The in hull transducer on my boat works great. It's just slapped on
the inside of a fairly thick hull.

I can't imagine putting a hole in a hull if you don't need to.


I experimented with shooting through the hull, and directly by
dangling the transducer over the side prior to permanent installation.
Shooting through the hull reduced the maximum range of the depthsounder
by about 25%. The solid FG hull thickness was about 5/8". A yard guy
said experiment with exact placement if you do shoot through the hull,
as a void or dry spot in the laminate directly below the transducer can
reduce the maximum range by a lot.

One good thing you can do with a shoot through the hull setup is orient
the transducer so it points straight down on a curved hull surface, by
using an adjustable mount (available from manufacturer) which immerses
the transducer in mineral oil. The gizmo is a tube with an angled
flange on the bottom which is glued (with 5200) to the hull, and a
sealing threaded top for the transducer.

My through hull mounted transducer is flush on a curved part of the
hull, about 20 degrees out of plumb, so I get greater range on the
tack which plumbs the transducer. When heeled 30 degrees on the "bad"
tack, the maximum range drops by over 50%. This is with a high
frequency 200khz trandsucer which has a fairly narrow emission cone;
the effect should be less with a 50khz transducer, as its emission cone
is wider.

Oh, and it's an inexpensive depthsounder with a rated maximum range of
200 feet.


I'm thinking..for coastal cruising/daysailing I'm really only concerned
with accuracy between 0 and 100 feet max.

Don White wrote:

I'm thinking..for coastal cruising/daysailing I'm really only concerned
with accuracy between 0 and 100 feet max.

I'll add my support for mounting inside the hull - I had no trouble
seeing down 100+ feet shooting through a sold hull. Being plumb helps
but is not essential (within limits).

And I can't let it pass without mentioning, a fishfinder is vastly
superior to a simple digital sounder, and often even cheaper. Even if
you never plan to fish, its really helpful to have a history of your
depth. Some of them will give a good reading of the nature of the
bottom for anchoring.

yeah, I agree. if an "in hull" transducer works, why put extra holes in
the hull? Also, what about 3M 4200? it is supposed to be bedding
rather than bonding, it's what I used to install my two through hulls.