Cruisers Forum

Join CruisersForum Today

Thread Tools Rate Thread Display Modes
Old 21-07-2015, 00:28   #1
Senior Cruiser

Cruisers Forum Supporter

Join Date: May 2012
Location: Hailing Minny, MN
Boat: Vancouver 27
Posts: 633
Images: 1
Your Guide to Building Integral Watertanks

My old water bladders had reached the point where bleach and clean hoses weren't up to the task against some pretty funky business, and there was no way to get in there and properly clean the things, so I set about constructing integral tanks. Going into it, I wasn't able to find much info on the web, so I'm hoping this might help someone else.

I'm not aware of any certification I hold through any reputable organization in any way shape or form. That said, the process is pretty straight-forward given basic fiberglassing skills (wow, easy!) and a few power tools.

The process of making roughly two 30 gallon tanks took me over a week, made a complete mess of the boat, and cost about $700. Probably $1000 if I had to buy everything from scratch. But it probably could have been done a good deal cheaper if you're the typical crafty boat owner.

The one source that was very helpful was this: Atom Voyages - Integral Watertank Construction

He describes the process in excellent detail, better than I'm about to do, so I'll just build on that with my experience and some pictures.

Originally, there were two 30 gallon bladders under the cabin sole. After disposing of them, the old bilge paint was sanded away and the area thoroughly cleaned with water and acetone in prep for epoxy and fiberglass. I had some off cuts of 3/8" plywood that wasn't going to any other use, so those formed the baffles, end walls and tank tops. 1/2" plywood probably would have been more suitable, but I had lots of biaxal cloth left over from another project which I'm sure added plenty of strength in the end. Fiberglass tape would be preferable in terms of how easy it is to work with.

I used cardboard templates to cut the ply into rough-fit shapes. Small voids between the plywood and hull were filled with epoxy thickened with colloidal silica before a couple layers of medium weight biaxal cloth were used to bond and reinforce it all to the hull. The end walls were doubled up with two pieces of 3/8" plywood. Don't forget to cut little holes in between the baffles for water migration
I also glassed in short runs of small pvc pipe under the tanks to allow for drainage.
looking forward..
Click image for larger version

Name:	IMG_20150707_024509_117.jpg
Views:	179
Size:	387.0 KB
ID:	105719
looking aft..
Click image for larger version

Name:	IMG_20150707_024005_340.jpg
Views:	166
Size:	405.4 KB
ID:	105720
sanded and ready for final coatings of food-grade epoxy..
Click image for larger version

Name:	IMG_20150711_184903_557.jpg
Views:	176
Size:	401.6 KB
ID:	105721
The black strips are leftover bits of carbon fiber tape I had from another project.

For the inspection ports, I used sheets of 12" x 12" g10 placed over the intersection of the baffles such that I could get an arm well into each corner for future cleaning.
To start, I epoxied in fiberglass bolts to the underside of 1/16" g10 sheets. I then cut out holes in the plywood tank tops corresponding to the placement of the bolt heads and epoxied the g10/bolts flush to the plywood. In the end, there's roughly a 9" x 9" opening to get in there and inspect things in the future, and a solid 1 1/2" sealing lip. TO seal the tanks, I used food-grade buna-n gasket material and 3/16" g10 covers.
Click image for larger version

Name:	IMG_20150710_194027_984.jpg
Views:	176
Size:	403.3 KB
ID:	105722
Click image for larger version

Name:	IMG_20150712_193442_265.jpg
Views:	177
Size:	362.6 KB
ID:	105723
Click image for larger version

Name:	IMG_20150712_193554_981.jpg
Views:	168
Size:	302.4 KB
ID:	105724

All these materials were bought from mcmaster-carr. I bought fiberglass bolts and nuts because I didn't want to use metal that would eventually corrode. The 1/4" bolts that I bought ended up being a bit tender for my liking and I ended up shearing a few of the threads off the first time I torqued the nuts down. Had to cut out and rebed some. If I did it again I might just settle on quality stainless bolts, or perhaps upgrade to 5/16" fiberglass bolts.

Also, in the states, is a great source for all things fiberglass. It's basically free compared to buying cloth at west marine and is good quality.

Finally, 3 coats of fda-grade epoxy (brewcoat..Low VOC, FDA rated epoxy coating for brewery tanks linings, potable water tanks and food processing.)
Click image for larger version

Name:	IMG_20150712_033809_312.jpg
Views:	174
Size:	309.9 KB
ID:	105725
Click image for larger version

Name:	IMG_20150712_033822_111.jpg
Views:	182
Size:	264.8 KB
ID:	105726
Click image for larger version

Name:	IMG_20150713_012444_181.jpg
Views:	202
Size:	278.8 KB
ID:	105727

The brewcoat came in a 2 gallon kit and cost $220. I had a bunch leftover after doing the interior of the tanks, so I decided to use it on the outside of the tanks as well. It's great stuff..totally non-toxic, very durable, good potlife for applying, and a nice smooth finish. All in all easy to work with and should readily stand the test of time.

Click image for larger version

Name:	IMG_20150714_205609_649.jpg
Views:	181
Size:	331.0 KB
ID:	105728

The brewcoat is specifically certified for potable tanks but does use a bpa-resin, if that's not something you're into. They recommend a solid 2 coats which would be enough for a couple hundred gallons worth of tankage. I had a lot leftover. They also recommend wiping the pre-coated surface with white vinegar to give it the right pH (this according to Kathy, the nice lady you'll talk to when you buy the stuff).

Finally, attaching all the pickups and such. When epoxying the nylon fittings to the tank, I cut little teeth into the nylon with a plunge saw bit on my multimaster tool to give something extra for the epoxy to grab onto. Otherwise, you may find epoxy doesn't adhere super well to the nylon, and there would be a risk of fitting failure down the line, particularly in the process of prying off old hoses and such. I also made a point to bed all the lower pickups in large mounds of epoxy so there would be no risk of them breaking off.

Attached Thumbnails
Click image for larger version

Name:	IMG_20150720_235557_774.jpg
Views:	151
Size:	298.3 KB
ID:	105718  
laika is offline   Reply With Quote
Old 04-08-2015, 18:42   #2
Registered User
dolfin93se's Avatar

Join Date: Jul 2010
Location: Beaufort, NC, US
Boat: Jouet 950, 32 feet
Posts: 19
Re: Your Guide to Building Integral Watertanks

Great article. Have you found food grade silicon or other sealant? My water tank tops are removable with a lot of screws. I would have to bad it with some sort of sealant. I can not use gasket because the surface is not flat and has curves.
dolfin93se is offline   Reply With Quote
Old 04-08-2015, 18:56   #3
Registered User

Join Date: Dec 2013
Location: Anacortes
Boat: Sea Ray,SundancerDA,30
Posts: 65
Re: Your Guide to Building Integral Watertanks

Hi try this site Best Sellers - Top Secret Coatings and google for military paints. they have every thing you'll need
good luck
CC45 is offline   Reply With Quote

tanks, water

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Cleaning an integral keel diesel tank stillbuilding Engines and Propulsion Systems 21 30-04-2014 03:29
Youth PFD with Integral harness? Families, Kids and Pets Afloat 1 28-11-2013 23:00
Converting Integral Fiberglass Water Tank to Diesel sv.Crake Plumbing Systems and Fixtures 10 19-04-2011 07:46
Problem with Navtech-22 Hydraulic Integral Backstay Adjuster RJV Deck hardware: Rigging, Sails & Hoisting 6 30-07-2009 04:20
Our Refit Begins! Step 1 Integral fuel tanks Yachts66 Construction, Maintenance & Refit 19 14-04-2009 11:30

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 22:34.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.