On Fri, 10 Jun 2005 04:23:57 +0000, Bill McKee wrote:

One piece is much better. Those joints in the wood have little strength.


I don't think the joints in the core NEED much strength. I mean, you can
use Styrofoam as a core, and that can be broken easily by hand. Also,
balsa core is not very strong laterally, but it is an excellent core
material (unless it gets wet).

With cores, the important thing is that it adhere well to the skin, and
that it have good compression strength. Butted plywood with, say, epoxy
filler at the joint, should make a good core.

But then I am not a mechanical or structural engineer or naval architect,
so take my opinion for what it is worth.

--Mac


"Chris" wrote in message
...
So replacing wood with new plywood means I can cut out a shape of any size
and replace it with a close to equal piece of plywood correct? Just glass
the old plywood to the new plywood, right? No concern over how big a
piece of plywood is, etc? I could use two pieces of plywood for one hole?
etc


It appears I've got more rot than I had expected (although the transom
feels strong otherwise).

I've pulled out about a 1 foot x 1 foot section around the drain plug and
am evaluating whether there will be anymore to go too.. Have drilled a
bunch of holes in the lower inner part of the transom to see how far it
spreads and allow all the wood to dry up before my final decision



wrote in message
ups.com...
It's too late to do any more than slightly slow the problem by sealing
the exposed wooden surfaces of the drain hole.

If you like this boat and plan to keep it, you will want to cut the rot
out of the transom. Be sure to go a few inches beyond the point where
you "think" the rot ends when scarfing in the new piece. You should be
able to cut away part of the fiberglass on the outside of the transom
and spoon out the punky wood, cut a new piece of the best marine ply
you can find, and then glass up the exterior again.

This is a great chance to learn from the bad practice of the original
builder. Any hole drilled through a wooden member- transom, stringer,
etc for the purpose of draining water should have the edges sealed up
to prevent water from wicking into the surrounding area and promoting
rot. If it were my project, I would cut the drain hole large enough to
accept a drain plug with a bronze collar fitting. Seal the edges of the
hole with a layer of glass and resin, and then bond the bronze collar
into the sealed hole- perhaps using epoxy.

One rot gets a foothold, it is relentless. Transom rot on small boats
is fairly common, and as most are outboard powered it is double
trouble.

Mac wrote:
I don't think the joints in the core NEED much strength. I mean, you can
use Styrofoam as a core, and that can be broken easily by hand. Also,
balsa core is not very strong laterally, but it is an excellent core
material (unless it gets wet).

You can use Styrofoam but you shouldn't.

With cores, the important thing is that it adhere well to the skin, and
that it have good compression strength. Butted plywood with, say, epoxy
filler at the joint, should make a good core.

With cores, the most important property is the shear
strength. Obviously if it doesn't stick to the skins it
isn't core... Transoms should have a higher compressive
strength - balsa is good, plywood is o.k., high density foam
(= 120 kg/m3 is ideal)

But then I am not a mechanical or structural engineer or naval architect,
so take my opinion for what it is worth.

--Mac

I am a m.eng. and naval architect

Evan Gatehouse

On Sat, 11 Jun 2005 21:10:47 -0700, Evan Gatehouse wrote:

Mac wrote:
I don't think the joints in the core NEED much strength. I mean, you can
use Styrofoam as a core, and that can be broken easily by hand. Also,
balsa core is not very strong laterally, but it is an excellent core
material (unless it gets wet).

You can use Styrofoam but you shouldn't.

With cores, the important thing is that it adhere well to the skin, and
that it have good compression strength. Butted plywood with, say, epoxy
filler at the joint, should make a good core.

With cores, the most important property is the shear
strength. Obviously if it doesn't stick to the skins it
isn't core... Transoms should have a higher compressive
strength - balsa is good, plywood is o.k., high density foam
(= 120 kg/m3 is ideal)

As long as it is not polystyrene? ;-)

But then I am not a mechanical or structural engineer or naval architect,
so take my opinion for what it is worth.

--Mac

I am a m.eng. and naval architect

Evan Gatehouse

Thanks for chiming in! It's always nice to have people who actually know
what they are talking about.

So, to come back to the OP's question, if a transom is originally
constructed with fiberglass skins and a plywood core, and some of the
plywood is rotten, would it be OK to replace the rotten parts with several
pieces of plywood butted together? Or would it be better to scarf in one
piece of plywood to replace the rotten area?

I guess another way of asking the question is, would butt joints in the
plywood core significantly weaken the transom?

I am thinking that they would not weaken the transom.

--Mac

Thanks for chiming in! It's always nice to have people who actually know
what they are talking about.

So, to come back to the OP's question, if a transom is originally
constructed with fiberglass skins and a plywood core, and some of the
plywood is rotten, would it be OK to replace the rotten parts with several
pieces of plywood butted together? Or would it be better to scarf in one
piece of plywood to replace the rotten area?

I guess another way of asking the question is, would butt joints in the
plywood core significantly weaken the transom?

I am thinking that they would not weaken the transom.

--Mac

If they are relying on the core for stiffness and strength,
then butt joints would be weaker. I wouldn't do it on my
boat for example.

I would cut off the outer skin near the transom corners,
chisel and then grind out all the plywood and rebuild the
transom

Evan Gatehouse

On Mon, 13 Jun 2005 21:44:06 -0700, Evan Gatehouse wrote:
[I wrote]

Thanks for chiming in! It's always nice to have people who actually know
what they are talking about.

So, to come back to the OP's question, if a transom is originally
constructed with fiberglass skins and a plywood core, and some of the
plywood is rotten, would it be OK to replace the rotten parts with several
pieces of plywood butted together? Or would it be better to scarf in one
piece of plywood to replace the rotten area?

I guess another way of asking the question is, would butt joints in the
plywood core significantly weaken the transom?

I am thinking that they would not weaken the transom.

--Mac

If they are relying on the core for stiffness and strength,
then butt joints would be weaker. I wouldn't do it on my
boat for example.

I would cut off the outer skin near the transom corners,
chisel and then grind out all the plywood and rebuild the
transom

Evan Gatehouse

Thanks. From elsewhere in the thread, it sounds like the OP is going to
get serious about the job and replace just about all the plywood in the
transom.

Also, the OP mentioned somewhere else that there is almost no fiberglass
on the inside of the transom near the top. This leads me to believe that
it is essentially a plywood transom which uses overlapped glass as a
means to attach the transom to the hull. This is a lot different than,
say, a cored deck.

--Mac

That's correct. On both the right and left sides (inside) you can see the
original plywood near the top of the boat. Almost looks like they didn't
finish the job.

"Mac" wrote in message
news
On Mon, 13 Jun 2005 21:44:06 -0700, Evan Gatehouse wrote:
[I wrote]

Thanks for chiming in! It's always nice to have people who actually know
what they are talking about.

So, to come back to the OP's question, if a transom is originally
constructed with fiberglass skins and a plywood core, and some of the
plywood is rotten, would it be OK to replace the rotten parts with
several
pieces of plywood butted together? Or would it be better to scarf in one
piece of plywood to replace the rotten area?

I guess another way of asking the question is, would butt joints in the
plywood core significantly weaken the transom?

I am thinking that they would not weaken the transom.

--Mac

If they are relying on the core for stiffness and strength,
then butt joints would be weaker. I wouldn't do it on my
boat for example.

I would cut off the outer skin near the transom corners,
chisel and then grind out all the plywood and rebuild the
transom

Evan Gatehouse

Thanks. From elsewhere in the thread, it sounds like the OP is going to
get serious about the job and replace just about all the plywood in the
transom.

Also, the OP mentioned somewhere else that there is almost no fiberglass
on the inside of the transom near the top. This leads me to believe that
it is essentially a plywood transom which uses overlapped glass as a
means to attach the transom to the hull. This is a lot different than,
say, a cored deck.

--Mac

If the transom is suspect, check out http://www.transomrepair.com, they
have a whole system for removing all of the wood in the transom and then
filling the space with a pourable resin/chopped filler system. I was going
to use this in my 21' Mako (the Mako factory approved), but sold the boat
before it needed the work (just had a few rotten spots, but the majority of
the transom has still been strong).

Cheers,

--
Steve (remove anti spam XYX in return address for correct email)
http://www.gulf-stream.net/patandsteve

I'm trying to dry the transom out a bit before I dig further into it.
Clearly several days won't be enough, and who knows if weeks will ever as
long as it is outdoors. So, I may have to get digging into it sooner,
regardless of the still wet wood.

To recap, I've got almost 1 foot square cut out around the drain hole (drain
hole and up), which was the really punky stuff. I've also got 1/4" holes
drilled in various places on both sides to checkout the wood. (note that
pouring something in won't likely help here with it exposed and open now).

The outer hull is thick, really thick (fiberglass), but the inner side is
almost done 3/4 the way up and pretty thin, I don't even think it adds
strength.

Currently the motor is still mounted (however many pounds of it).

To visualize the transom on this boat, consider the typical outboard
transom, but on a V type hull. Inside under where the motor mounts
(centre), there looks like there is a big timber there, such as a rough cut
2" x 4", or maybe 2x6 or 2x8. Its hard to tell as I suspect it may go all
the way through to the outer hull and be glued in. Below this timber about
2-3 inches down are the other motor engine bolts that tie it in lower. And
below this for the next 1.5 feet perhaps is the area of the drain plug. To
each side of this the floor is elevated clearly due to the V, as well the
solid wall (inner/outer fiberglass) goes up higher to the full length of the
transom. I can actually see plywood near the top as it wasn't covered in
glass.

I suspect so far that the wood beneath the timber is rotten, and likewise
straight across from there on both sides. Above that things appear strong
and solid, and a few drill holes have proved that there's nothing punky
there.

So, I either take the outboard off now, or leave it on. My guess is to
clear the wood from under the timber level all the way to both sides, and
then put new wood in right across. Glass it in, and to finalize it, glass a
2x4 or 4x4 to the outside of this new area (to the inner transom, and
floor).

Now it'll be strong. What do you think?


"Steve Weingart" wrote in message
.. .
If the transom is suspect, check out http://www.transomrepair.com, they
have a whole system for removing all of the wood in the transom and then
filling the space with a pourable resin/chopped filler system. I was
going
to use this in my 21' Mako (the Mako factory approved), but sold the boat
before it needed the work (just had a few rotten spots, but the majority
of
the transom has still been strong).

Cheers,

--
Steve (remove anti spam XYX in return address for correct email)
http://www.gulf-stream.net/patandsteve

- Fixing transoms is not an area I'm involved in, but looking at it from a
long way away I'd say you can't do a proper job with the outboard still in
place. My experience in cutting out rot is that it's easier to cut out a
complete piece of wood and replace it rather than cut out 10% and try to fit
something to fill up the hole. Wish I'd known this a while back.
- Any time you spend in removing and replacing the outboard will be saved
several times over by the time you are done.
- you need to do ALL the demolition before you start to do the repair (
it's true of most things ) It's no more work to patch a little more area
than it is to fill several more holes.
- with the motor off and the demo done, try a small electric fan heater
under a cheap tarp - 24 hours at 30 degrees C does a lot of drying. But
control the temperature, too hot and it will be too dry. It takes time for
moisture to migrate to the surface where it can evaporate.
- read and believe the info from the epoxy suppliers
David

"Chris" wrote in message
...
I'm trying to dry the transom out a bit before I dig further into it.
Clearly several days won't be enough, and who knows if weeks will ever as
long as it is outdoors. So, I may have to get digging into it sooner,
regardless of the still wet wood.

To recap, I've got almost 1 foot square cut out around the drain hole
(drain hole and up), which was the really punky stuff. I've also got 1/4"
holes drilled in various places on both sides to checkout the wood. (note
that pouring something in won't likely help here with it exposed and open
now).

The outer hull is thick, really thick (fiberglass), but the inner side is
almost done 3/4 the way up and pretty thin, I don't even think it adds
strength.

Currently the motor is still mounted (however many pounds of it).

To visualize the transom on this boat, consider the typical outboard
transom, but on a V type hull. Inside under where the motor mounts
(centre), there looks like there is a big timber there, such as a rough
cut 2" x 4", or maybe 2x6 or 2x8. Its hard to tell as I suspect it may go
all the way through to the outer hull and be glued in. Below this timber
about 2-3 inches down are the other motor engine bolts that tie it in
lower. And below this for the next 1.5 feet perhaps is the area of the
drain plug. To each side of this the floor is elevated clearly due to the
V, as well the solid wall (inner/outer fiberglass) goes up higher to the
full length of the transom. I can actually see plywood near the top as it
wasn't covered in glass.

I suspect so far that the wood beneath the timber is rotten, and likewise
straight across from there on both sides. Above that things appear strong
and solid, and a few drill holes have proved that there's nothing punky
there.

So, I either take the outboard off now, or leave it on. My guess is to
clear the wood from under the timber level all the way to both sides, and
then put new wood in right across. Glass it in, and to finalize it, glass
a 2x4 or 4x4 to the outside of this new area (to the inner transom, and
floor).

Now it'll be strong. What do you think?


"Steve Weingart" wrote in message
.. .
If the transom is suspect, check out http://www.transomrepair.com, they
have a whole system for removing all of the wood in the transom and then
filling the space with a pourable resin/chopped filler system. I was
going
to use this in my 21' Mako (the Mako factory approved), but sold the boat
before it needed the work (just had a few rotten spots, but the majority
of
the transom has still been strong).

Cheers,

--
Steve (remove anti spam XYX in return address for correct email)
http://www.gulf-stream.net/patandsteve

"David Flew" wrote in
:

I agree with what David is saying here... Remove the O/B if you are
going to do major work... But, that said... On my Mako, I had a similar
circumstance where the wood in a triangle about a foot tall and 2 feet
wide at the bottom of the transom was completely rotten. The upper 18"
of the transom was completely solid. I drained the water and sealed the
leaks, then watched it closely for flexing for two years prepared to do
the repair job. It was still solid when I sold the boat.


BTW, that pourable stuff is not for putting in through small holes...
You remove the skin at the top of the transom and dig out ALL of the
wood. You are left with the two skins. You plug all of the holes and
put some plywood on the outside of both sides as a temporary support
then fill up the transom with the sea-cast material. It sets, then you
have a permanent wood-free transom. Redrill the engine mounting holes
and remount the O/B. Check out the website, it's got a ot of useful info
(just for truth in advertising's sake: I have no relatoinship with
those folks whatsoever, I just did a bunch of research on that product
and it looked like a great thing).

- Fixing transoms is not an area I'm involved in, but looking at it
from a
long way away I'd say you can't do a proper job with the outboard
still in place. My experience in cutting out rot is that it's easier
to cut out a complete piece of wood and replace it rather than cut out
10% and try to fit something to fill up the hole. Wish I'd known this
a while back.
- Any time you spend in removing and replacing the outboard will be
saved
several times over by the time you are done.
- you need to do ALL the demolition before you start to do the repair
(
it's true of most things ) It's no more work to patch a little more
area than it is to fill several more holes.
- with the motor off and the demo done, try a small electric fan
heater
under a cheap tarp - 24 hours at 30 degrees C does a lot of drying.
But control the temperature, too hot and it will be too dry. It takes
time for moisture to migrate to the surface where it can evaporate.
- read and believe the info from the epoxy suppliers
David

"Chris" wrote in message
...
I'm trying to dry the transom out a bit before I dig further into it.
Clearly several days won't be enough, and who knows if weeks will
ever as long as it is outdoors. So, I may have to get digging into
it sooner, regardless of the still wet wood.

To recap, I've got almost 1 foot square cut out around the drain hole
(drain hole and up), which was the really punky stuff. I've also got
1/4" holes drilled in various places on both sides to checkout the
wood. (note that pouring something in won't likely help here with it
exposed and open now).

The outer hull is thick, really thick (fiberglass), but the inner
side is almost done 3/4 the way up and pretty thin, I don't even
think it adds strength.

Currently the motor is still mounted (however many pounds of it).

To visualize the transom on this boat, consider the typical outboard
transom, but on a V type hull. Inside under where the motor mounts
(centre), there looks like there is a big timber there, such as a
rough cut 2" x 4", or maybe 2x6 or 2x8. Its hard to tell as I
suspect it may go all the way through to the outer hull and be glued
in. Below this timber about 2-3 inches down are the other motor
engine bolts that tie it in lower. And below this for the next 1.5
feet perhaps is the area of the drain plug. To each side of this the
floor is elevated clearly due to the V, as well the solid wall
(inner/outer fiberglass) goes up higher to the full length of the
transom. I can actually see plywood near the top as it wasn't
covered in glass.

I suspect so far that the wood beneath the timber is rotten, and
likewise straight across from there on both sides. Above that things
appear strong and solid, and a few drill holes have proved that
there's nothing punky there.

So, I either take the outboard off now, or leave it on. My guess is
to clear the wood from under the timber level all the way to both
sides, and then put new wood in right across. Glass it in, and to
finalize it, glass a 2x4 or 4x4 to the outside of this new area (to
the inner transom, and floor).

Now it'll be strong. What do you think?


"Steve Weingart" wrote in message
.. .
If the transom is suspect, check out http://www.transomrepair.com,
they have a whole system for removing all of the wood in the transom
and then filling the space with a pourable resin/chopped filler
system. I was going
to use this in my 21' Mako (the Mako factory approved), but sold the
boat before it needed the work (just had a few rotten spots, but the
majority of
the transom has still been strong).

Cheers,

--
Steve (remove anti spam XYX in return address for correct email)
http://www.gulf-stream.net/patandsteve








--
Steve (remove anti spam XYX in return address for correct email)
http://www.gulf-stream.net