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Old 06-16-2015, 04:42 PM   #81
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Old 06-16-2015, 05:37 PM   #82
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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.
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Old 06-16-2015, 05:43 PM   #83
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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.
...many have a hard time with "glue"....
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Old 06-16-2015, 07:25 PM   #84
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So they must first be placed in the boat , filled for 48 hours and then , usually foamed in place, with straps too.
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.
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Old 06-16-2015, 07:31 PM   #85
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"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.

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?
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Old 06-16-2015, 08:19 PM   #86
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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.
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Old 06-16-2015, 09:36 PM   #87
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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.
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Old 06-16-2015, 10:12 PM   #88
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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"....
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Old 06-16-2015, 11:27 PM   #89
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"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.
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Old 06-16-2015, 11:56 PM   #90
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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.
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Old 06-17-2015, 12:24 AM   #91
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Marin`s post reminds me of a certain "subcontinent" airline, keen to depart Sydney, unable to close a door, pushed it shut with a forklift tine, "repairing" the resulting punched hole with a pop riveted patch.
Personally I`d avoid cutting holes in sides of boats unless unavoidable. (Should builders include removable side panels to accommodate inevitable tank replacements?)
Anyone doing it ought disclose to their insurer, if the work failed and a claim resulted the insurer could (here at least) rightly deny for non disclosure. Providing a survey certificate when disclosing would help, all the more if the surveyor checked the work at multiple stages, not just the faired painted polished stage.
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Old 06-17-2015, 01:15 AM   #92
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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.
Bad boat builders may not be engineer conscious. Good boat builders are.

Cut a major hole in any piece of support structure (all portions of boat hulls are at a sort of cooperative support structure)... especially a flexing support structure (all boat hulls are flexing support structures) and you have a BIG problem for trying to reinstall the same structural integrity as was previously in place.

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Old 06-17-2015, 03:18 AM   #93
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On the other hand, Vestas Wind, the around the world Volvo 65 racing yacht, wrecked & severly gutted on a reef near Madagascar, has now been repaired and is back in the race. It had a huge chuck of rear hull and stern replaced, yet they are allowing it to go and re-enter an ocean race when it will be pounded much more than a GB cruiser. So if it comes to that, I think it will be ok, although peronally I would exhaust all other possibilities, like others have said.
I would still have gone for cutting out the old tanks and replacing with several interlinked & smaller fuel grade plastic ones, that could have been got around the engines without their being moved at all, myself.
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Old 06-17-2015, 07:19 AM   #94
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Smaller and multiple tanks, in my opinion is a very poor option. Less fuel capacity is never good for resale value. Bladders are considered temporary only. Personally, I would pull the engines if at all possible. But cutting a big hole in the hull wouldnt bother me at all. I would do it myself, it aint rocket science. A 1/2 inch by 6 inch inner flange to reset the removed cutout on, glued and screwed in place then the aforementioned peice glued and screwed to that. Remove the screws after the goop has set. Use at least a 12 to 1 scarf completely thru to the flange and layup the new 'glass. Another point mentioned was foaming in tanks. Its not unusuall on big boats. In this case I would use a 4lb foam between the tank and hull. And normal mounting methods, straps, neoprene, etc. Absolutey coat the tanks with a good epoxy, I prefer coal tar epoxy.
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Old 06-17-2015, 08:19 AM   #95
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Smaller and multiple tanks, in my opinion is a very poor option. Less fuel capacity is never good for resale value. Bladders are considered temporary only. Personally, I would pull the engines if at all possible. But cutting a big hole in the hull wouldnt bother me at all. I would do it myself, it aint rocket science. A 1/2 inch by 6 inch inner flange to reset the removed cutout on, glued and screwed in place then the aforementioned peice glued and screwed to that. Remove the screws after the goop has set. Use at least a 12 to 1 scarf completely thru to the flange and layup the new 'glass. Another point mentioned was foaming in tanks. Its not unusuall on big boats. In this case I would use a 4lb foam between the tank and hull. And normal mounting methods, straps, neoprene, etc. Absolutey coat the tanks with a good epoxy, I prefer coal tar epoxy.
If it is a fact that a large cut-out hole in FRP pleasure boats can be fully re placed (repaired) back into the same structural integrity as the original hull section (your description does sound convincing for a layman in major FRP repair... such as myself). Then, it seems to reason that replacing engines in good ol" FRP pleasure cruisers could (maybe should) mostly be accomplished in the same manner. Especially in twin screw models and with alongside the motor tanks next to the hull it could be a double x 2 whammy for decades worth of valuable improvements! By cutting a hole in one side it would be tank/engine/engine/tank removal and exact same in reverse for installing the four new units. Besides, what a great access hole to reconfigure all items in bilge and repaint!
Sounds like a virtual slam-dunk to me...

I've got to wonder why we don't hear more of this apparently simple and cost effective method for tank and engine replacements. Is it simply because there are not enough FRP specialists available that understand how to correctly refasten the cut out back into/onto the hull??
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Old 06-17-2015, 08:26 AM   #96
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I'm not going to question the integrity or methodology of replacing tanks via the side of a boat but after the tank(s) have been replaced and the side patched, you still have the finish the hull. What's the cost of a quality paint job? $15K for a 40 footer? vs what's the cost of removing and reinstalling 1 or 2 engines? Maybe the boat needed a paint job anyway?
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Old 06-17-2015, 08:39 AM   #97
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I'm not going to question the integrity or methodology of replacing tanks via the side of a boat but after the tank(s) have been replaced and the side patched, you still have the finish the hull. What's the cost of a quality paint job? $15K for a 40 footer? vs what's the cost of removing and reinstalling 1 or 2 engines? Maybe the boat needed a paint job anyway?
How about cutting hole in roof, open up salon sole and using boom lift?

"Simple is as Simple Does!
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Old 06-17-2015, 08:48 AM   #98
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Generally, painting below the rub rail is not the big expense that painting above it is. And, gel coat is not that difficult to match if the rest of the hull is gel coated. Same with paint, so unless you just want to or need to a total repaint/gel coat is not neccessary. As for removing machinery from the side, same procedure. Non of this is "new". Its been done for years and is accepted "best practice" in a lot of situations. Its common place. Its kinda like years ago if you needed major engine work done on you ford truck the mechanic leaned, crawled, contorted himself to do it, now they just pull the cab. Its faster, easier and better.
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Old 06-17-2015, 10:25 AM   #99
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Generally, painting below the rub rail is not the big expense that painting above it is. And, gel coat is not that difficult to match if the rest of the hull is gel coated. Same with paint, so unless you just want to or need to a total repaint/gel coat is not neccessary. As for removing machinery from the side, same procedure. Non of this is "new". Its been done for years and is accepted "best practice" in a lot of situations. Its common place. Its kinda like years ago if you needed major engine work done on you ford truck the mechanic leaned, crawled, contorted himself to do it, now they just pull the cab. Its faster, easier and better.
absolutely the red...and the rest too...

The info is out there...just not all that much in small boat circles.

Funny some accept the Grand Banks video where they cut the bottom out and yet above the waterline except for cosmetics is worse?
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Old 06-17-2015, 12:36 PM   #100
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Our boat has a rectangular section of the flying bridge sole "pre-cut" to allow it to be removed for full direct-down access to the engine space for removing/replacing engines. The manufacturer did this on the original wood versions of the boat and continued the practice for a few years after the line was switched to fiberglass before eliminating this feature. Hopefully we'll never need to use it....
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