Fuel tank dilemma, help please

Folks that cant afford real Monel custom made real tanks and go for second choice plastic fuel grade boxes remember they install differently.

The plastic tanks will expand and grow when first filled with fuel.

So they must first be placed in the boat , filled for 48 hours and then , usually foamed in place, with straps too.

I too am really curious how the inside of the hull gets glassed with the new tank in in the way of access. Maybe they just don't worry about any cuts or seams visible.

Ragin Cajun......Which yard is doing your work? We had a similar issue on a sportfisher back in the 80's. An aluminum tank, actually both, split on the underside where the baffles were welded in. The manufacturer used continuous welds instead of stitch welds and cracks developed necessitating R/R of both. Fortunately access was by cutting out the entire cockpit sole and reglassing in place. When finished we could not tell a difference by appearance (awlgrip texture was different than OEM but better) but we could feel less vibration in the sole underway. I think the repair was more solid than original. The work was done by Shubert's Marine at West End in N.O. Good luck with the repair. I think you are making the correct decision.

Glassing on the interior I don't think is necessary.


While double bevels are common and may be preferred in many repairs....they can build up a lip on the inside first then do pretty much what they want... overlaps or reverse bevels.

I'm sure there is an obvious answer but why couldn't bladders or, blivets, as we called them in the Army be used as permanent tanks?
Framed, secured, collapsible when empty.

http://http://atlinc.com/rangeextender.html

"Glassing on the interior I don't think is necessary."

Unless you are going into water that would be over your head for walking to shore.

The problem is , even a proper construction that has a 400% safety margin on strength will still flex in a sea way.

To assure a proper bond to keep water out is not hard ,

but engineering a patch that will flex as the hull works far beyond most boat yards skill set or engineering ability.

ktdtx said:

I'm sure there is an obvious answer but why couldn't bladders or, blivets, as we called them in the Army be used as permanent tanks?
Framed, secured, collapsible when empty.

http://http://atlinc.com/rangeextender.html

Click to expand...

Not out of the question, for sure, and often used as temporary tanks for added range, but then usually not mounted somewhere where there might be sharp protuberances to puncture them on. Down in the ER, and carrying your only precious fuel supply I would be less happy. I have a bladder holding tank safely PVC and carpet cocooned in my boat under the ER floor, but have had the water supply bladder the PO had installed develop a leak, just from moving and rubbing on a slightly gritty surface. Hence replaced by food grade plastic - much better.

FF said:

"Glassing on the interior I don't think is necessary."

Unless you are going into water that would be over your head for walking to shore.

The problem is , even a proper construction that has a 400% safety margin on strength will still flex in a sea way.

To assure a proper bond to keep water out is not hard ,

but engineering a patch that will flex as the hull works far beyond most boat yards skill set or engineering ability.

Click to expand...

I agree that most yards aren't that trustworthy for major glass repairs...in fact few do it that I know of...they farm out glass worth to glass guys.

That still doesn't mean you have to have access inside the boat for the whole process of patching the hull.

I heard that Zimmerman was good for glass repairs. I have no experience with them. Anyone?

Not understanding exactly where/how the tanks are placed inside your boat... without moving engines, can't they be cut out piece by piece from their original position and then a group of different dimension (location fit-able) tanks installed as replacement? I've even heard of, but not seen, account of tanks being collapsed enough for tight location removal by high-volume suction process.


Personally, with diesel as fuel, I might opt for the sectional cut out method.


Looking forward to see pictures. Current, undisturbed tank photos might help posters here provide recommendations.


Best Luck! - Art

I've seen that video of cutting the bottom on the GB. My question is how do they get to the inside to reGlass it?

motion30 said:

I've seen that video of cutting the bottom on the GB. My question is how do they get to the inside to reGlass it?

Click to expand...

Based on my reading and experience with glass work...you don't need to, it can be done from the outside, either building up a flange first if that's your method...or not...with just relying on the scarf joint.

Man - My mechanically appointed mind simply cannot fathom how huge holes can be cut into hull sides or bottoms without severe structural integrity issues... ongoing. That said; It may be that IF both sides of the hole could be thoroughly tended to during side or bottom replacement efforts that the area could again become substantially strong.

If at all possible I'd surely opt to somehow/someway remove and replace the tanks from inside without cutting cavernous holes in the hull.

My 25 cents on the issue (inflation ya know - 2 to 10 cents no longer works - lol)... YRMV!

Happy Tank-Removal/Replace Daze - Art

I had the tanks in 'Angelina' replaced about 20 years ago. The boatyard had no problem pulling the engine and trans up through the saloon sole and out the side door. They do this for a living. They have massive articulating hydraulic lifts and decades of experience. They removed the tanks intact and sent them to a tank maker for exact duplicates. It was all in a day's work for them. You need to find a boatyard that does mechanical work for a living. Unfortunately, this one is no longer in business. Not because of their work or prices but because of the personality and appetites of the owner's daughter. That's another thread.

Al: of course that is the preferred approach IF the engines can be removed via cut-outs in the saloon floor. The point about the cut-the-hull-side/bottom approach is that this is viable in situations where thru-the-saloon just cannot be done. Experienced shipwrights/fibreglass guys are saying there is NO loss of structural integrity with this approach, if the 'glass work is properly carried out

Perhaps it isn't the yachty thing to do and you have suggested you wouldn't consider welding the tank, but I would at least ask around about it. Go to some of the commercial tie-ups and ask around. I'll bet there are a lot of commercial vessels that take a different approach to fuel tank repairs. Perhaps this approach won't work but you won't know if you don't ask.


Jim
Sent from my iPad using Trawler Forum

JDCAVE said:

Perhaps it isn't the yachty thing to do and you have suggested you wouldn't consider welding the tank, but I would at least ask around about it. Go to some of the commercial tier-ups and ask around. I'll bet there are a lot of commercial vessels that take a different approach to fuel tank repairs. Perhaps this approach won't work but you won't know if you don't ask.


Jim
Sent from my iPad using Trawler Forum

Click to expand...

I agree with the premise of Jim's post.

Might I add... go back to my post # 36. I'm confident there must be some way to locate/pinpoint the exact location of leak. If through careful inspection tanks are otherwise deemed to be in generally OK condition then the point-of-leak should be able to be somehow accessed via minor hull intrusion and repaired-in-place. If tanks generally taint OK condition... well, then............

Again I say: Best Luck!

Remember most composite work is about bonding.... like gluing scarphs in plywood....not mechanical like screwing and bolting.


Hope I am not insulting anyone...but maybe the reason that some think inside access is absolutely necessary.

Many have their doubts and yes there had been many failures in composite work...but many more successes when done correctly.

Rajun Cajun
Sorry to hear of your problem. Did the yard start the replacement? Can't imagine the worry being caused by cutting out the sides. But, one must do what one has to do. Which yard is doing the work? Hope all goes well.

I've got to admit the "cutting a hole in the side of the boat" made me pause. But building a flange on the inside, as some have suggested, and bonding the cutout to the flange shouldn't be a big deal.

This also made me think about visiting a naval yard with my brother-in-law, a submariner. The sub went in for a major refit, which required removal of components that had been built-in to the sub. At the refit, the yard cut big holes in the side of the sub so that the components could be accessed.

As I remember, replacement of each patch panel required nearly 2 weeks of specialized welding.

Compared to a nuclear sub hull, your patches should be a piece of cake!

Seriously, I doubt that the boat hull is very highly engineered. The safety factor is probably very high- that is, the boat is much stronger than necessary for the expected loads. Repair by a competent glass shop should not be a big deal.

Greetings,
Welcome aboard.

On two occasions I've had crash damage on carbon fiber race car tubs repaired by an outside in approach using a large external only scarph with NO internal scarph or overlay. One repair done by the chassis manufacturer in Georgia and the other done by a company out of Canada. Both chassis re-certified by the sanctioning body for use. Both used by my son (If I or his engineer had any concerns I would have ponied up the 50K for a new tub) and both chassis performed as new. As noted above...if done properly with proper bonding of materials I would not hesitate to have the side of my boat cut open. There lies the caveat...if done properly. I have personal experience, which I related in a prior post, in having tanks cut out of the cockpit sole and it was re-glassed with an outer scarph only as the underside was inaccessible once the new tanks were laid in. The deck was definitely as solid as before.

rardoin said:

On two occasions I've had crash damage on carbon fiber race car tubs repaired by an outside in approach using a large external only scarph with NO internal scarph or overlay. One repair done by the chassis manufacturer in Georgia and the other done by a company out of Canada. Both chassis re-certified by the sanctioning body for use. Both used by my son (If I or his engineer had any concerns I would have ponied up the 50K for a new tub) and both chassis performed as new. As noted above...if done properly with proper bonding of materials I would not hesitate to have the side of my boat cut open. There lies the caveat...if done properly. I have personal experience, which I related in a prior post, in having tanks cut out of the cockpit sole and it was re-glassed with an outer scarph only as the underside was inaccessible once the new tanks were laid in. The deck was definitely as solid as before.

Click to expand...

...many have a hard time with "glue"....

FF said:

So they must first be placed in the boat , filled for 48 hours and then , usually foamed in place, with straps too.

Click to expand...

You are not going to foam in place tanks in a large trawler like you would under the floor of a center console. It's just not feasible. Plus it would make a big mess.

In this case you would have to build the proper supports and braces to hold it in place and retain the expansion.

FF said:

"Glassing on the interior I don't think is necessary."

Unless you are going into water that would be over your head for walking to shore.

The problem is , even a proper construction that has a 400% safety margin on strength will still flex in a sea way.

To assure a proper bond to keep water out is not hard ,

but engineering a patch that will flex as the hull works far beyond most boat yards skill set or engineering ability.

Click to expand...

True it takes a reasonably skilled yard to do this kind of repair. But I fail to see why or how a properly done "patch" would have to flex as the hull works?

If done properly the "patch" is fully integrated into the hull. The patch should not be moving around in any independent way that I can see. But maybe I'm missing you point?

If it doesn't wind up ending over a natural hard point like a structural member...it needs the same coefficient of expansion (same material of the hull...often to the dismay of epoxy only types) and similar flex.


If interior members are providing the hard point to a degree and the patch isn't huge....then it doesn't need to mimic the rest of the hull as much.


I'm sure a specialist can explain it better...but that is my take on the research I have done.

The business of cutting holes in the hull, removing and replacing the tanks, and then putting patches on the hull has been discussed at length several times on the GB owners forum over the years. There are companies which do this and claim successful results.

However it is the view on the forum among the members who have had professional careers in the boat maintenance and repair business, including the founder of the forum, Bob Lowe, who used to own Oak Harbor Boatworks on Whidbey Island and who has extensive experience with removing and replacing tanks in GBs that this is not an ideal solution.

In their view a patch of this size compromises the integrity of the hull, and while it may be fine for years of service, the hull strength is still compromised. Better, they feel, to cut the tanks up in place if this is possible and then replace them with a system of smaller tanks that can be installed without removing the engine(s). This is what was done on our boat the year before we bought it.

Or, if there is a reason not to do this, then remove the engine(s) and then change out the tanks.

When there are these alternatives available, cutting the hull to remove and reinstall tanks, while it may be "simpler" than removing the engine(s), it's not a smart solution in the long run in their view.

If simple little things like a hole compromise a hull, what about full extensions???


I find it hard to believe that insurance companies would approve of so many vessel extensions, insure the places that do them...and in all my years monitoring search and rescue.....I don't think I have ever heard of a boat lengthened or had a properly done hull patch for engine or tank replacement that sank from the repair. Not saying it hast happened but certainly not common enough to make a difference in the industry.


Hard to believe other pros would think holes only violating a flat panel would be a major compromise if done well.


A poorly done patch is bad.... but so is a poorly installed thru hull. I have salvaged a few boats at the dock because "professionals" left hoses off or caulking out, etc...etc...


So if you worry about if the patch is done correctly...you have to worry about a lot of things others may do to your boat too.


Like I said...a lot of even old timer pros have a hard time with "glue"....

"In their view a patch of this size compromises the integrity of the hull, and while it may be fine for years of service, the hull strength is still compromised."

Hmmm..it may be fine for years of service but the hull strength is compromised?

If done right, I don't buy it. I've seen massive fiberglass repairs done and they go through complete surveys and pass with flying colors. In many cases they have to pass class surveys.

We had a 42' GB that a charter ran up on the breakwater into Keywest. The only thing that kept it from sinking was that it was to well hung up on the rocks. Once the hull was repaired it was stronger than new due to the fact they added stringers during the repair. It passed an after the fact insurance survey no problem. This was like 30 years ago. And it's still out there running around.

One point I recall being talked about was the fact that in order to make the patch strong enough the repair technique is such that it adds weight to the boat. Not a big deal in the case of cruisers like GBs--- the heavier they are the better they ride -- but it was a drawback to this particular process in the view of the folks discussing it, as I recall.

This is not my area of knowledge so I can only repeat what was discussed. But to my way of thinking the big advantage of a fiberglass boat over wood is that the hull is one integral piece. No individual components to loosen over time, need refastening, have seams that can open up, and so forth. Sure, a holed hull can be repaired and obviously repaired for the long term as Capt. Bill points out. But the advantage of that one-piece hull has been lost to a degree.

We chose to "roll" the 787's composite fuselage sections to make each section a one-piece, integral piece, as opposed to Airbus' decision to make their A350 fuselage out of multiple composite panels attached to a frame. Our fuselage shells don't have or need a frame. Where a plane like the 777 has literally thousands of parts that make up each fuselage section shell, each fuselage shell in the 787;s fuselage is a single part number because it is just a single piece. Even the stringers are integral to the shell; they are not separate components.

This has all sorts of advantages until you put a hole in it. It can repaired, of course. We spent a lot of time and money developing repair processes that don't alter the safety of the structure. But the repairs add weight, much more of a big deal in an airplane than in a boat.

And as soon as you make a hole and then patch it you open the door to risk. Is the job done right? Did the materials cure up properly? Was the patch itself designed effectively? There are, of course, ways of testing the integrity of a composite structure (fiberglass is a composite). With our airplanes the primary means of non-destructive composite testing is ultrasonic. But the fact remains that where you had a nice, one-piece, uncompromised hull (or fuselage) now you don't.

So the view of the GB experts seemed to be why open the door to risk when there are methods of removing old tanks and installing new ones that don't disturb the integrity of the hull at all? At least with GBs. The discussions did not branch out into changing out tanks in other makes and models.

Their view makes sense to me, but as I say, it's not an area I have any experience in whatsoever.