Good afternoon, I read with interest the comments from Mr. Hall regarding the practice = of replacing fuel tanks by cutting a hole in the sides. I do not know if = he refers to us specifically but I offer the following for = enlightenment. I recognize that there are many ways to repair yachts and = good men are allowed to disagree without being disagreeable. I agree with his statement that a blind, one sided patch is a totally = unacceptable method of repair although I have seen these performed for = many years by reputable yards on transom additions, hull repairs and = other work. Though I have seen no problem with the "one sided repair = method" I would not use it in our yard or factory. We have been = building and repairing frp yachts since 1966 and thus far have never = suffered a minor fracture in any frp work done so we feel confident we = understand the technology involved. Our work is done on both sides of the scarf. In order to assure = reasonable tapers we use a shaving tool set to progressive depths as the = area shaved gets further from the cutout. We typically laminate to a = ratio of 30-1 on the outside of the hull and in some cases as much as = four times that on the inside. In order to put the yacht back together = the new tanks and assorted parts are moved to one side of the machinery = spaces to have access to the inside of the repair. We occasionally lift = the engines and generators from the bilge to provide room to carry out = the work required. In the majority of the yachts on which we have performed this surgery we = find typically 3-4 laminates of woven roving, and 5-6 laminates of csm. = In loaded areas we occasionally find a csm-fabric combination which may = be as much as 2 additional laminates. These are uniformly done with = common polyester resin. If you visit the university of Delaware website = and dig through the minutia you will find a very complete guide to = composite construction, carried out at various intervals by the = university for the US military. An important note in their research = relates to the relatively poor characteristics of polyester as an = adhesive. In fact it is awarded no MILSPEC rating as an adhesive. We do = not consider it adequate for a repair of this type. We laminate with MILSPEC epoxy and we use engineered fabrics, specific = for the load and stresses encountered. A typical inside laminate is 14 = layers of multi axis engineered fabrics. We progress with each laminate = so that the finished work has no lumps or odd appearance despite being = hidden under the tanks. When we cross a stringer or frame we radius the = junction of stringer-hull so that the fabric conforms easily to the = changing angle. We typically "die out" the last laminate on the inside = of the outboard engine stringer which is approximately three feet from = the chine. In the majority of our installations we can remove and = replace the fuel tanks by making a cut in the side of the hull, downward = perhaps as far as 5-7" into the bottom. In the cases where we have been = require to remove an engine stringer section, we laminate the new = stringer using the same approximate.=20 schedule as above. Since stringers are a secondary lamination in the = boats original building technique I fail to see any significance in = removing and relaminating them if done properly. Since we are operating in a potentially contaminated environment with = oily residue present, we first use an industrial degreaser once the plug = is removed from the yacht. When clean we do not grind the edges of the = frp due to concern for spreading any contamination that could remain. We = use a carbide shaving tool with vacuum attached which simply cuts the = frp to the required depth. In this way we avoid grinding any = contaminates into the frp to which we will laminate and we can precisely = prepare the hull for the staggered laminates to come. The workers love = the fact that they do not have to live in an environment of clouds of = fiberglass dust.=20 On areas such as the chine we laminate a linear foam triangle shaped to = fit the angle of the hull side and bottom section. This foam is by a = reputable supplier to the marine industry. This triangular foam overlaps = the repaired area fore and aft and is tapered away to zero for a neat = look. This of course increases the strength of the chine by multiples. = We normally use peel ply between laminates to provide a very smooth = laminated surface and this of course provides a perfectly clean new = surface to laminate to, insuring the best possible bond. We then epoxy pigment the area until all the grain of the fabrics are = filled and replace the components, repairing and doing general = maintenance while the opportunity presents itself. This procedure was originally done by us in 1977 on a 42' Grand Banks = that had broken loose in a storm at sea on board a ship while being = delivered from the factory. The yacht was badly damaged with several = Volkswagen sized holes in the hull and superstructure. Though totaled by = the insuring company we were given the job to rebuild it to new = specifications. In order to effect repairs a great deal of equipment was = moved for access. I am happy to report that a dear friend of mine = purchased the yacht when we completed rebuilding it and the yacht has = roamed the Atlantic, Gulf and Caribbean Sea from Nova Scotia to = Venezuela since. It has not developed a single crack or other sign of = distress despite its rugged life. Since that time I have lost track of = the number of repairs we have done in this fashion however it is a large = number. My engineering tells me that the repairs carried out in this manner = exceed the original manufacturer's specifications by more than 4 times. = I am quite comfortable with this safety margin as are the many = customers. Some of the extra benefits of this method are:=20 1. Avoiding the inevitable damage to the yacht interior. 2. An opportunity to access areas of the yacht otherwise inaccessible. 3. The opportunity to do a complete cleanup and refit of the machinery = spaces with free access. 4. The yacht ends with a familiar fuel system, exactly as original = instead of multiple valves, hoses etc. 5. The original tankage is maintained and occasionally enhanced. 6. The original root causes of the failure can be addressed due to open = access to engine room vents, fuel fill areas etc. 7. The new tanks can be perfectly coated with MILSPEC primers and paint = products outside the yacht in a much friendlier environment. 8. The new tanks can be built by "braking" a large sheet of iron which = eliminates a great number of welds. 9. The new tanks can be fabricated to shed water from the tops rather = than allowing it to fester on a flat top. 10. When fairing the exterior we typically compound and buff the = repaired section to a high state for a perfect finish. This mandates = that we do the hull sides to match so the result is a yacht that looks = new inside and out with fresh bilges, clamps, hoses and buffed exterior. 11. The avoidance of the rust plague which comes from sawing up the = massive iron tanks in place. I have observed yachts done by sawing the = tanks into pieces small enough to handle and the rust from filings = observed would be enough to make me consider other methods. This is to = say nothing of the damage I have seen caused by lugging jagged, oily = heavy chunks of iron through the accommodations area. There are more benefits than the short list above but I believe it = illustrates the benefits of taking a fresh look at this problem which = ultimately may affect nearly all Grand Banks and several other brands. We build very high technology yachts in Asia at two factory locations so = frp construction is no mystery to us. As our frp crew says, it's just = fiberglass, not rocket science. Regards, David E. Marlow, President Composite Structures Inc. Marlow Marine Sales Division Snead Island, Florida

Wow I am impressed. If that was a snow job it was about the best I have ever heard. And I have heard Steve Jobs sell. I would let him cut my hull. Jim > -----Original Message----- > From: owner-trawler-world-list@samurai.com > [mailto:owner-trawler-world-list@samurai.com]On Behalf Of David Marlow > (by way of Georgs Kolesnikovs) > Sent: Wednesday, August 09, 2000 7:33 PM > To: Trawler World List > Subject: TWL: Discussion regarding the replacement of rusted fuel tanks. > > > Good afternoon, > > I read with interest the comments from Mr. Hall regarding the practice = > of replacing fuel tanks by cutting a hole in the sides. I do not know if = > he refers to us specifically but I offer the following for = > enlightenment. I recognize that there are many ways to repair yachts and = > good men are allowed to disagree without being disagreeable. > > I agree with his statement that a blind, one sided patch is a totally = > unacceptable method of repair although I have seen these performed for =<snip> to = > > David E. Marlow, President > Composite Structures Inc. > Marlow Marine Sales Division > Snead Island, Florida >