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Old 08-12-2009, 16:37   #16
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Or, as an alternative, go ahead and build one with plywood and epoxy and test it, instead of listening to "experts". Make up your own minds rather than accept the opinions of folks who haven't actually explored the medium. Anyone can criticize without cause or actual experience. And remember, it's really scary to be one of the first to venture over the horizon, but if you survive, you become legendary. Or don't. Forty years ago, multihulls were considered to be death traps. Funny how things turn out over time.
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Old 08-12-2009, 17:50   #17
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SS on my boat. Black steel on my friend's. No problems on either boat.

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Old 08-12-2009, 20:13   #18
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My alum tanks developed acidic spots in the bottom (think cavity) . went in with a dremel and played dentist . The bad spots were very soft like the alum had went to mush. Cleaned and brightened all bad spots then filled with JBweld. Then went in with a sander and sanded all the bottom and 2 inches up on the sides. Applied a thin layer of JBweld to all sanded areas . Hope this will provide an interface to protect the alum. Yr and a 1/2 in and no leaks. Knowing what I think I know now, if I were to have the tanks built today I would definitly have a protective coating put on the bottom 1/2 of the tanks. This should extend their lifetime well beyond the 10 yr average. The exterior was in like new condition, as it had been installed correctly.
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Old 08-12-2009, 20:21   #19
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Dumb question here...how do you fully lay up fiberglass/epoxy inside a wood tank? How do you fiberglass where you cannot be?
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Old 08-12-2009, 20:31   #20
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Quote:
Originally Posted by David M View Post
Dumb question here...how do you fully lay up fiberglass/epoxy inside a wood tank? How do you fiberglass where you cannot be?
Presume you leave a big enough inspection port? Although there's still the health issue of poking your head inside a big underventilated tank with all that epoxy - nasty stuff!
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Old 08-12-2009, 21:27   #21
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Besides having built a Roberts 38 many years ago, I've also built 2 composite airplanes, a Longez and a Cozy Mk IV. The airplanes had fiberglass and foam tanks in the wing roots and cruised at 200+MPH with no leaks. In the Longez, I often did rolls and would ocassionaly pull 3 or 4G's. Epoxy and wood or a good closed cell foam is absolutely un- beatable for fuel tanks.

How to close one up is easy. Build the bottom and 4 sides to include all of your baffeling glassed in. If you are using say 3/8th ply to build your tank then lline the vertical walls about 3/8 down from the top with a triangle strip that has the inside facing edge rounded to about a 3/16 radius. Screw the triangles to the walls with an epoxy fill behind. Then lay several layers of Uni cloth (looks like pinstrip material) on the 45 degrees bias so that it will wrap around the radius side of the triangle. While it's still green (set but not fully cured) cut the end level with the top of the inner tank wall. The triangle strips should be tied into the wall and the baffels with glass and resin. Then fit you top section with a little space all the way around. Make sure you have designed access ports into the top. Now glass the inside of the top and let it cure for an hour or two. Now put a couple of strips around the edge and push the top into the opening so that joins onto the triangle section with the just applied wet strips. Don't use screws as they will destroy the continuity of the wet glass by wrapping it around the screw. Put some weight on it to keep it in contact wtih the traingles and reach inside and wipe off and dripping resin and smooth the glass strips onto tank walls . When that has curred, radius the corners and glass the exterior. The end result is a tank that will last a long long time.

Just some other thoughts.

If you want to have nice straight lines on an overlay of glass. Put a row of duct tape on the adjoining piece. When the new layup is green, use the duct tape edge as a trim line and then remove the duct tape.

If you want a good surface to attach a second layup to cover the first with some old but smooth dacron cloth while the first is still wet and roll it right into the wet epoxy. Make sure to leave a big pull tap to grab hold of later. When the epoxy (this works on epoxy only) is full cured, grab the pull tab and pull off the dacron. This leaves a great weave pattern for future layups to attach to.
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Old 08-12-2009, 22:03   #22
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Glass (if you must) all flat surfaces. Assemble bottom, sides, and baffle plates with epoxy and finish nails, not fully driven home. Pull nails when cured. Install fillets with epoxy putty on inside. Sand fillets when cured, then, glass if you must. Sand and epoxy one more time to get a glass smooth interior surface. Install top of tank, which has had inspection plate holes cut, eased and fastener holes completed, using same technique as rest of the box. When cured, sand where the fillets go and install fillets along top, inside edges, via the inspection plate. Glass if you must. Sand, epoxy balance of interior to get an easy to clean surface. Grind the exterior edges to a nice radius, seal with epoxy (and glass if you must). Sand, epoxy to a cosmetic finish and install plumbing fittings. When the tank is installed in place, hook up plumbing. Pour in measured amounts of diesel to calibrate the fuel gauge and dipstick. When all is done, seal in the inspection plates. Secure the tank. It's really quite easy, strong, light and cheap, and best of all, more durable and safe than the metal tanks.

The foam tanks are an even better idea to improve strength to weight ratios. Just don't make tanks that can't be removed in a boat, should you suffer a penetrating rupture of the hull. I used wood because it was cheap and available, but foam would have been way cool.
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Old 08-12-2009, 23:10   #23
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You know...one of the really nice things about a good closed cell foam like Kegelcel, is that you can heat it up to about 150 degrees in a plywood heat box and it will melt onto the curves of the hull so that there is little lost space and still have the ability to pull it out if required.
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Old 09-12-2009, 08:32   #24
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04 Marine, that is a very cool idea. I want to build a hard dodger, using this technique, if I can pump the size of the "oven" to fit it. How long does it take for the foam to adapt to its curve form? Can you do it on a small scale with an industrial heat gun?
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Old 09-12-2009, 09:29   #25
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I'm very grateful for the ideas and techniques you guys are posting. Very interesting stuff.

Getting back to the fuel tanks issue for a second, it seems to me the only real disadvantage of plywood/foam/epoxy tanks is the insurance issue, which also translates into an issue for sale of the boat in the future.

Do I have that right, and if I do, how can it be addressed?
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Old 09-12-2009, 11:53   #26
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Quote:
Originally Posted by speedoo View Post
Getting back to the fuel tanks issue for a second, it seems to me the only real disadvantage of plywood/foam/epoxy tanks is the insurance issue, which also translates into an issue for sale of the boat in the future.

Do I have that right, and if I do, how can it be addressed?
Spray it a nice rust color, spill some diesel in the bilge and tell the insurance folks it's stainless.
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Old 09-12-2009, 12:06   #27
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"04 Marine, that is a very cool idea. I want to build a hard dodger, using this technique, if I can pump the size of the "oven" to fit it. How long does it take for the foam to adapt to its curve form? Can you do it on a small scale with an industrial heat gun? "

Roy M,

The oven only needs to be a sheet of plywood cut in half with a 2x8 all the way around. Use the heat gun to heat up the interior and a deflector and fan to move air around inside the oven. How long depends on the size of the oven...thickness of the foam and outside air temperature.

However there is another way. Build a one off frame that will emulate your dodger's shape. Tack 1 X 2 furring strips onto the frames to fill in the shape. Then use someting like Airex foam (closed cell PVC) as it will lay over most shapes cold. Then punch holes at the required spots over the frurring strips and draw heavy string through the foam. Put a little slit in the top of the foam so that the string will sit into it and then tie it off from the inside. This holds the foam tight against the form until the exterior is glassed. Then just cut the strings, might be a hundred or more and it pops off the form for inside glassing. Window locations require a little different treatment as airex does not sand or cut to shape easily.
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Old 09-12-2009, 12:15   #28
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Roy,

How big are you making your inspection ports? Sounds like they are big enough for a head and an arm? Also, what is the spacing you use for the fasteners on the ports? What specific sealer are you using?

Sorry for all the questions but I am hoping to get this right the first time and really appreciate learning from the experience of others.

Mike
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Old 09-12-2009, 17:56   #29
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Quote:
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Getting back to the fuel tanks issue for a second, it seems to me the only real disadvantage of plywood/foam/epoxy tanks is the insurance issue, which also translates into an issue for sale of the boat in the future.

Do I have that right, and if I do, how can it be addressed?
OK, now that I have the smartass reply out of my system let me try again. To be honest I don't know if composite tanks would be an insurance issue but have never heard of insurance being denied because of tank material. Here is some info lifted from another forum:

"U. S. Coast Guard (USCG) regulations, Food and Drug Administration (FDA) regulations, American Boat & Yacht Council (ABYC) standards, and insurance restrictions should be carefully considered by anyone, professional and homebuilder alike, planning to build a composite tank. Tank construction material and construction processes have been investigated thoroughly over the years, and the lowest grief option is choosing a certified tank from a manufacturer. Certified fuel tanks have already been tested in accordance with strict fire and flame regulations, and have proven themselves in the field. Certified potable water tanks have been made to minimize or eliminate extractives.

While professional builders are bound by tough USCG regulations and ABYC standards regarding tanks, back-yard-boat builders have the option to follow or disregard them. If the back-yard-boat builder chooses to disregard the regulations and doesn't sell the boat, the builder meets the intent of the federal regulations. However, once the builder decides to sell the boat, the federal regulations become applicable and must be followed because he/she has built the boat for the purposes of sale. A good reference for individuals building boats for their own use and not for the purposes of sale is the publication, Safety Standards for Backyard Boat Builders, COMDTPUB P16761 3B. This may be obtained from USCG Headquarters or on the Internet; addresses, phone numbers, and web sites are noted in the reference section. "


References and Resources:
Safety Standards for
Backyard Boat Builders,
COMDTPUB P16761 3B
Commandant (G-OPB-3),
US Coast Guard,
2100 Second Street, SW,
Washington DC, 20593-0001,
(202) 267-0984
USCG Infoline: (800) 368-5647
http://www.uscg.mil/d8/mso/louisvill...bp16761_3b.pdf

Recreational Boating Safety,
U. S. Coast Guard Headquarters:
Commandant (G-OPB),
US Coast Guard,
2100 Second Street, SW,
Washington DC, 20593-0001,
(202) 267-0984
USCG Infoline: (800) 368-5647
www.USCGBoating.org

Code of Federal Regulations:
Government Printing Office
Credit Card: (202) 512-1800, M-F, 8-4
Fax Order: (202) 512-2233 24 hours
Payment by check:
Superintendent of Documents
Attn: New Orders
P. O. Box 371954
Pittsburgh, PA 15250-7954
Customer Service: (202) 512-1803
Free on World Wide Web
Fuel Tanks: http://www.access.gpo.gov/nara/cfr/w...cfr183_00.html

Marine Sanitation Devices:
http://www.access.gpo.gov/nara/cfr/w...cfr159_00.html

Fuel tanks for USCG Inspected Vessels (<100 GT)
http://www.access.gpo.gov/nara/cfr/w...cfr182_00.html

Food and Drug Administration:
5600 Fishers Lane
Rockville MD 20857-0001
http://www.access.gpo.gov/nara/cfr/w...cfr175_00.html

NSF International
PO Box 130140
789 N. Dixboro Road
Ann Arbor, MI 48113-0140, USA
www.nsf.org
Tel: (734) 769-8010
Toll Free (USA): (800)-NSF-MARK
Fax: 734-769-0109

American Boat & Yacht Council
3069 Solomons Island Road
Edgewater, MD 21037-1416
Tel: (410) 956-1050
Fax: (410) 956-2737
info@abycinc.org
www.abycinc.org
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Old 09-12-2009, 18:00   #30
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Inspection ports really don't need to be that big. If the tank is tightly baffeled, you wont be able to go that far in ony one direction anyway. You'll need one in each baffeled area...so 6 to 8 inches should be fine. use a mirror and flashlinght vice sticking your head into the tank.

Make the base of your inspection ring retainer out of plywood donuts. When you decide on spacing drill out some of the plywood but not all and take a bolt with a section welded to the top so that it stick out an inch on eah side, this prevents turning. Mix some epoxy and flox (cotton fibers) and bed the bolt head into the hole with epoxy flox then galss over them to make a tight seal. Your actual lid if it's diesel could be out of heavy plexiglass in which case you can visually inspect the tank for quality and quanity.
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