Hi All:

I did a search regarding custom built epoxy/glass lined plywood waste
holding tanks. The jurry says that the plastic roncho tanks are the
only way to go............ but that option simply wont work for me
becuse of the compound weird space I have.

So my question is .................. given I can not use "the best"
tank material availible, I am looking seriously at plywood and epoxy
for a 25 gallon tank. What I have read from our experts is it will
either crack or start to smell becuase epoxy just does that. Okay, so
how do you keep it from smelling. I am running out of options here.

So for the folks who recomended epoxy in the 1999 posts are you still
happy with them 7 years later?

Anybody out there acually use a plywood/epoxy tank that has worked fine
for 10 years?
Bob

The wood/epoxy tank will work if done right... I will assume that you
can build the tank on the workbench and then install... The key is to
have a stiff tank to keep the epoxy from cracking due to the tank walls
flexing, encapsulate the flanges of the hose connectors, and to have
every millimeter of plywood heavily encapsulated in glass...
The method is to use multiple fiberglass layers lining the tank... A
tank built from half inch plywood with a quarter inch of fiberglass
liner will work, along with adequate bulkheads to stiffen the tank and
control sloshing... Vacuum bagging the fiberglass gives the best
physical properties... Use WEST SYSTEM 105 resin and slow hardner...
Slow hardner gives you the best physical properties in the cured
epoxy... Rapid hardner is less good and 5 minute epoxy is not
considered water proof... Vacuum bag it and apply heat during the
cure... 90 degrees F for the first 4 hours then 130 F for another 8
hours.. Do not overheat during the first 4 hours...
Be sure the fiberglass/epoxy liner wraps the raw edges of the wood at
the access hatch... After the internal tank is cured, then trim the
glass at the hatch opening as necessary and put a layer or two of
fiberglass on the exterior, including lapping down over the hatch edges
so it is doubly covered and will leave the wood totally encapsulated...
While the external epoxy is curing, put the hatch cover in place, wrap
it in plastic so it doesn't stick, and weight it down so that the fiber
glass forms to the mating surface of the hatch... Use a neoprene
gasket for sealing the hatch...

All hose barb connections have to be installed at the time of glassing
and the flanges buried in the glass internally and externally,
including saturating the raw edges of the holes for the hose
connectors...

Done correctly the tank will be servicable for the life of the boat...

denny

Bob wrote:

Hi All:

I did a search regarding custom built epoxy/glass lined plywood waste
holding tanks. The jurry says that the plastic roncho tanks are the
only way to go............ but that option simply wont work for me
becuse of the compound weird space I have.

If you can't find a molded tank that'll fit, these companies make
excellent quality custom welded plastic tanks for a reasonable price:

http://www.seafabtanks.com/

http://www.triplemplastics.net/

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://shop.sailboatowners.com/books...ku=90&cat=1304

Bob wrote:


So my question is .................. given I can not use "the best"
tank material availible, I am looking seriously at plywood and epoxy
for a 25 gallon tank. What I have read from our experts is it will
either crack or start to smell becuase epoxy just does that.

Huh!

Done properly, epoxy/glass tank works just fine.

A 25 gallon tank is relatively small. I wouldn't waste time with a
plywood core.

I built a 65 gallon tank for my boat using 4 layers of 24 Oz double
bias glass and epoxy.

You could use 17 OZ double bias glass for your tank.

Build with a clean out port in top of tank (mine is about 12x16), held
in place with screws.

Line the interior of the tank with two (2) coats of "tank resin".

Build the tank with two (2) dip tubes for pump out. It simplifies the
plumbing.

Good luck.

Lew

Lew Hodgett wrote:

Bob wrote:


So my question is .................. given I can not use "the best"
tank material availible, I am looking seriously at plywood and epoxy
for a 25 gallon tank. What I have read from our experts is it will
either crack or start to smell becuase epoxy just does that.

Huh!

Done properly, epoxy/glass tank works just fine.

A 25 gallon tank is relatively small. I wouldn't waste time with a
plywood core.

I built a 65 gallon tank for my boat using 4 layers of 24 Oz double bias
glass and epoxy.

You could use 17 OZ double bias glass for your tank.

Build with a clean out port in top of tank (mine is about 12x16), held
in place with screws.

Line the interior of the tank with two (2) coats of "tank resin".

Build the tank with two (2) dip tubes for pump out. It simplifies the
plumbing.

Good luck.

Lew

I built a small foam cored tank for an airplane wing tank.
Urethane foam glassed inside and out.
about 3/8" thick foam - for the sides for the box and 1/8" thick foam
cored top and bottom.

The sides and the bottom skin were assembled with small amounts of
5 minute epoxy. Then glassed inside and out with 1/2 ounce fabric.
Inside got 3 layers, outside 2.

Then the top panel (already glassed and cured (and prepped) was taped on
with glass tapes.

We didn't use it because the dang thing weighed a ton (aeronautical ton,
folks).

But we all agreed it was for sure strong.

Vynalester resin is prefered for all fuel and water systems.
I use epoxy for laminating everything else.

Urethane foam was used here, but PVC would be better.

Urethane can not be hot-wired to shape, as it emits a cyanide gas
when burned (!).


Now, for a really low bucks approach, I've always wanted to use
corregated cardboard (prep with West Epoxy like plywood) and glass.

Kind of an industrial size version of Molt Taylor's TPG system?

In article .com,
"Bob" wrote:

So for the folks who recomended epoxy in the 1999 posts are you still
happy with them 7 years later?

A qualified "Yes". Our tank's worked flawlessly (after correcting an
initial fault), but if I were to do it again, I'd put the tank in the
bow. There are tanks that will fit properly.

See Peggie's book for how to do it right.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

Hello All:

Thank you for taking the time to share your advice. I love this place!
Where else can somebody ask a dumb question and get decades of
experienced and knowledgeable answers.

I contacted two of Peggy's recommendations for a plastic tanks but
after all the custom do-dads I wanted I think I will be best suited
with a "proper" epoxy ply tank.

So to Denny, Peggy, Lew, Cavelamb, and Jere a BIG thank you for your
advice. I will most certainly heed it all.

Also I ran across this link that describes how to use West epoxy for a
tank fab. Not exactly the same standard mix, wet, and lay up. Which may
be the cause of more casually built epoxy waste tanks

http://www.westsystem.com/ewmag/18/tanks.html

Bob

Bob wrote:

Anybody out there acually use a plywood/epoxy tank that has worked fine
for 10 years?
Bob


A tale of two ****ties:

About six years ago I boat my boat from a friend of mine (fellow
engineer) who had built his own plywood epoxy tank. Like yours it was
an odd shape and needed a custom job. He used standard 1/4" plywood and
covered both inside and out with one layer of glass. He used iron nails
to attach the lid to the box, sealing it with silicon window sealer.

I did not know this when I bought the boat, as the price was so cheap it
didn't warrant a survey. We moved on very shortly after that and
everything was fine with the holding tank for another six months. Then
we began accusing each other of farting.

I turns out that one layer of glass is micro porous. It took about 8
months for the sewage to seep through the inner layer, rot the plywood
core and then seep through the outer layer. It was not a pretty job to
remove this tank (which was 1/3 full at the time) and clean up the bilge.

I built a new tank from epoxy and glass mat using stiff cardboard as a
template. I used many layers (the final wall thickness was 3/8") and
added a powder to the epoxy (recommended by West Systems) specifically
for creating vapor/liquid barriers.

We have had no problems with it since, save for the inadequate job I did
venting the tank, but that was minor, providing we regularly add some
sort of sewage treatment.

Given all the options, this probably wasn't the cheapest or easiest, but
it did fix the problem.

Hope this helps.

Robb

AMPowers wrote:

A tale of two ****ties:

He used iron nails
to attach the lid to the box, sealing it with silicon window sealer.

Oh my gosh!!!

I used many layers (the final wall thickness was 3/8") and
added a powder to the epoxy (recommended by West Systems) specifically
for creating vapor/liquid barriers.

Ahh, this sounds more like what most advise strongly.

Given all the options, this probably wasn't the cheapest or easiest, but
it did fix the problem.

Yes, exactly what I've been thinking. Stuff a palstic tank under the V-
berth and foam it in sounds like an inexpesive and quick
way................ I only wish I had that option. After an eight year
remodel on a house built in 1905 my wife cringed when I got the boat.
Her reply when I asked her thoughts on getting a sailboat were, " I
dont want to whittle a mast before we can go for
sailing...................................."

Time to go whittle a waste tank.
Bob



Hope this helps.

Robb