Hulls should be be permanently attached to their decks - not with self tapping screws alone.

Transient momentary forces typically encountered at the junction of fiberglass hulls with their decks or top halves are too great for the tiny surface area of the number 8 self tapping stainless screws typically seen joining large production yachts. The amount of deflection occurring during normal operation from 3 foot seas encountering the surface of approximately 1/4 of the diameter of the already tiny threads of number 8 self tapping stainless screws will cause the edges of the fiberglass panels at the point of the screw holes to exert sheer forces on the threads of the screws and by doing so disrupt the integrity of the fiberglass reinforced plastic matrix at that point of those sheer forces. But it is during adverse conditions such as hurricanes where a vessel may encounter a dock or other vessel we see results of this situation and learn why joining the decks and tops of boats with their hulls with self tapping screws alone is a bad idea.

Evidence of these excessive forces can be seen upon extraction of these self tapping screws from the rubrail line where the decks typically join with the hulls of vessels. Often these screws are bent into slight squiggles making them difficult to extract. These bends in the screws occur when the sheer force of each half of the vessel encountering even just normal momentary forces, caused that section of the joint to deflect enough to force a greater amount of the total weight of each side of the joint (the entire top half weight momentarily flexing against a greater amount of the hull weight below) to bear down on the small diameter of the threads of the screw or screws which will be absorbing that deflection during that momentary force. The hole that the screw encounters becomes elongated and can eventually lose grip on the now squiggly screw. It matters little if you are a nice person, or mean or happy or sad - a very predictable diminishment of the structures within and around that number 8 screw (or series of screws) will occur, and over time will worsen.

But in adverse conditions where a hurricane has caused your vessel to slam against a dock, the difference between your vessel surviving these impacts with minimal damage or with substantial damage depends on whether or not this joint is made correctly. In vessels which have encountered these types of forces (repeated slamming against a dock) the bending of the screws and elongation and failure of the screw hole is a prominent feature. If that joint was permanently affixed, the combined material could have adequately absorbed the impact.
(With the combined interleaving of the upper lip of the shoe box joint and bottom sides combined with the proper joining material injected in between the two halves at time of construction, manufacturers have a perfect opportunity to make this joint (and vessel) a very strong impact absorber indeed - and in the process, the vessel much more sea worthy. But by simply joining such large pieces of a vessel with self tapping screws alone and with no adhesive epoxy, methacrylate or polyurethane adhesive, the perfect opportunity is lost and it can create further problems should your vessel get caught in emergencies as described above.

If a boat is made correctly, though, it can withstand some pretty tough punishment and survive in great shape, but if the wrong corners are cut those corners fail and the boat sustains damage it ordinarily wouldn’t have had to - and worse could sink (when it oughtn’t have had to).

Recommendation for manufacturers: Production vessels of 32 feet and above should make the design of this joining of the top to the bottom halves of the vessel such that the joining of these parts (arguably one of the most important joints in the boat) can be easily and properly facilitated by the labor force employed in performing this function. In other words the design of the vessel must match with the capabilities and sense of understanding that the workers have about that vessel (and vessels in general) that they are working on. Many of the failures occur at this point between the normally good designs but improper execution at time of construction by either inadequately trained workers or workforces that have high turnover rates thus precluding the possibility of acquiring this vital necessary understanding of each particular designed vessel and its construction needs. (Note to manufacturers: Investigate a possible way to improve the inside of the top half joint in the typical “shoebox” joint style design. It is this inside of the top half which is often irregular and provides irregular meeting with the smooth exterior of the lower edge of the shoebox joint formed smoothly on the hull molded part. If the interior edge of the top half can be improved to be more uniform during the design phase, the joining can be simplified even for less skilled workers to accomplish adequately during production)

Recommendation for new boat purchasers: Ask if you can supervise aspects of the construction of your vessel or request that this proper adhering of the two halves of the vessel be performed. Inquire as to how the company joins these two halves. many use only screws and a thin bead of silicone caulk underneath the rub rail to prevent water intrusion. This is inadequate for large vessels for either structural stability, impact resistance or water intrusion prevention. a solid fill between the halves guarantees all three of the above desired design goals. It is possible to request to have specific procedures performed at the time of manufacture, this proper joining is one that should not be too expensive and the upsides are that you will have a more seaworthy vessel.

Recommendation for refit or restoring: This upgrade (which should have always been a standard not an upgrade) can be performed if one has access to the insides of the hulls, but can be time consuming if furniture and interior panel removal presents itself as a difficult task so it all depends on access. With access it is a relatively easy job to rough up the insides of the laminates of the two sides, clean them with acetone and wet them with epoxy and lay up several strips of epoxy impregnated fiberglass cloth along the inside perimeter of the vessel (overlapping at least 4 inches on each side) to permanently attach the top of the boat to the hull. Naturally this would be the time to remove the rubrail and inject either epoxy or epoxy based adhesive of the plexus type of methacrylate type adhesives or polyurethane types of adhesives into the thoroughly cleaned and preferably roughed up surfaces between the shoebox style joint typically employed in the design of modern production yachts.

The Northeast is constantly getting battered by hurricanes and I've seen a lifetime of vessels which have failed at this particular location. And every time I inspect the damage I'm always astonished at how insufficient the joining technique was. And every time its the same - squiggly bent screws which had to endure the sheer forces of fiberglass panels bearing down on them and elongated and torn holes in the fiberglass layup where the screws abraded and broke it down.


Solution: More attention needs to be paid to this joint at time of design and construction (mostly construction)

Tiara solved the hull/deck joint leaking issue years ago. Essentially the company uses a shoe box lid design with a strip of wood between the deck and hull. The joint is held together with copious amounts of polyurethane construction adhesive and robust screws every 6". Their newer boats do not leak and they don't break.

Funseeker, I noticed you posted back in 2013 your purchase of a 390 that needed engine removal, is this the same boat? If so how did you eventually get the engines out? Great write up about the joining of the deck to hull practice. I’ve always thought that was a cheesy way to build a boat. I assumed that since the engines and associated equipment in the bilge is mostly installed prior to installation of the top of the boat, the manufacturers figured they need to allow for possible future disassembly and permanent FRP scarf joinery would add exponential labor to split the vessel. Somewhere between #8 screws and full FRP joining lies the solution.
Carpe Diem

Sea Ray did a lousy job of sealing my hull to deck joint. Dropped on, drove in screws, then put some superficial caulk.

After I found a gap where the screws had pulled out I make a proper fix. Completely disassembled the rub rail and joint, and used 3M 5200 adhesive to bond the hull and deck together. Then replaced the screws. That joint is never separating now.

Carpediem44DB said:

Funseeker, I noticed you posted back in 2013 your purchase of a 390 that needed engine removal, is this the same boat? If so how did you eventually get the engines out? Great write up about the joining of the deck to hull practice. I’ve always thought that was a cheesy way to build a boat. I assumed that since the engines and associated equipment in the bilge is mostly installed prior to installation of the top of the boat, the manufacturers figured they need to allow for possible future disassembly and permanent FRP scarf joinery would add exponential labor to split the vessel. Somewhere between #8 screws and full FRP joining lies the solution.
Carpe Diem

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It probably is more related to access and assembly than anything else. Any boat under 40' would have assembly issues where many of the components were set in place before the deck was fitted. Sure it is a cost issue but it will become a refit issue if you can't get the deck off to deal with mechanical issues without cutting the deck or the sides of the hull. I'm not sure glassing the deck to the hull is a practical answer. I'm all for better joining materials but I would need a marine engineer to tell me that converting a flexible joint into a solid joint wouldn't create a different set of problems.

PlayDate said:

It probably is more related to access and assembly than anything else. Any boat under 40' would have assembly issues where many of the components were set in place before the deck was fitted. Sure it is a cost issue but it will become a refit issue if you can't get the deck off to deal with mechanical issues without cutting the deck or the sides of the hull. I'm not sure glassing the deck to the hull is a practical answer. I'm all for better joining materials but I would need a marine engineer to tell me that converting a flexible joint into a solid joint wouldn't create a different set of problems.

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David Pascoe who was a long time yacht surveyor (and critic of current manufacturer laxity) wrote many times about how bad it is to affix the decks to hulls of large vessels with self tapping screws. Here is one article: https://www.yachtsurvey.com/Screwit.htm He and most marine engineers will agree - self tapping screws alone is a bad idea.

There's not too much concern that the kind of permanent tabbing of the deck to the hull as I described above would present an engineering problem. It will not appreciably alter the overall flexion (torsional twist) of the vessel being so far out on the perimeter. Also the idea that such permanent affixing of the deck to the hull would be contraindicated because it would preclude the removal of the deck from the hull is not really an issue. I have never seen or heard of an attempt to separate a 40 ft Sea Ray in this way. Most of these manufacturers have engine removal access methods and procedures involving the removal of the helm or deck panels that facilitate engine removal so there would be little need to remove the entire deck from the yacht. If for some rare reason that would be required, running an ablative cutoff saw along any tabbed joint would be the least of the issues in such a colossal operation.

The twisted shaped screws that often are seen in vessels which have not even slammed against docks is evidence that even during normal operations the forces on these small screws are too great. Fiberglass laminates are simply not designed for the kind of tensile strength required to withstand pounding momentary sheer forces at such small points - so what occurs is that during such momentary forces as two fiberglass panels exert force against each other, the tiny screw threads holding the two opposing panels dig into the fiberglass laminate matrix and essentially pulverize it a tiny bit. And then with the next momentary force (wave) it happens again, ever so small each time. Over time though the fiberglass laminate becomes fatigued at the point of entry of the screw by the sheering forces of the opposing fiberglass edges. And the screw by receiving repeated sheering forces - also shows signs of fatigue via the telltale squiggly bends often found in screws along the rubrail line. The bent screw now grinding more of the already elongated screw hole until the screw hole is just a loose powdered large elongated hole no longer able to perform its function.

There is zero downside to making this a solid joint - strength, impact resistance and waterproofness are all improved if care is taken to make this joint as good as it could be. Strength at this important junction is also critical to surviving encounters with docks or objects that may occur during hurricanes or other adverse conditions. The only downside is that people are not demanding this proper construction methodology so manufacturers are happy to not provide it. It would literally take no more than a half hour of time at the factory and a relatively incremental increase in material cost to achieve significant improvements in strength, impact resistance and waterproofness at this vital junction. I like to design and build for when conditions are at their very worst - you'll thank yourself should you ever get caught in fierce conditions. Hopefully articles like this will encourage robust boatbuilding techniques and more seaworthy vessels.

funseeker said:

David Pascoe who was a long time yacht surveyor (and critic of current manufacturer laxity) wrote many times about how bad it is to affix the decks to hulls of large vessels with self tapping screws. Here is one article: https://www.yachtsurvey.com/Screwit.htm He and most marine engineers will agree - self tapping screws alone is a bad idea.

There's not too much concern that the kind of permanent tabbing of the deck to the hull as I described above would present an engineering problem. It will not appreciably alter the overall flexion (torsional twist) of the vessel being so far out on the perimeter. Also the idea that such permanent affixing of the deck to the hull would be contraindicated because it would preclude the removal of the deck from the hull is not really an issue. I have never seen or heard of an attempt to separate a 40 ft Sea Ray in this way. Most of these manufacturers have engine removal access methods and procedures involving the removal of the helm or deck panels that facilitate engine removal so there would be little need to remove the entire deck from the yacht. If for some rare reason that would be required, running an ablative cutoff saw along any tabbed joint would be the least of the issues in such a colossal operation.

The twisted shaped screws that often are seen in vessels which have not even slammed against docks is evidence that even during normal operations the forces on these small screws are too great. Fiberglass laminates are simply not designed for the kind of tensile strength required to withstand pounding momentary sheer forces at such small points - so what occurs is that during such momentary forces as two fiberglass panels exert force against each other, the tiny screw threads holding the two opposing panels dig into the fiberglass laminate matrix and essentially pulverize it a tiny bit. And then with the next momentary force (wave) it happens again, ever so small each time. Over time though the fiberglass laminate becomes fatigued at the point of entry of the screw by the sheering forces of the opposing fiberglass edges. And the screw by receiving repeated sheering forces - also shows signs of fatigue via the squiggly bends often found in screws along the rubrail line. The bent screw now grinding more of the already elongated screw hole until the screw hole is just a loose powdered large elongated hole no longer able to perform its function.

There is zero downside to making this a solid joint - strength, impact resistance and waterproofness are all improved if care is taken to make this joint as good as it could be. Strength at this important junction is also critical to surviving encounters with docks or objects that may occur during hurricanes or other adverse conditions. The only downside is that people are not demanding this proper construction methodology so manufacturers are happy to not provide it. It would literally take no more than a half hour of time at the factory and a relatively incremental increase in material cost to achieve significant improvements in strength and waterproofness at this vital junction and that is the purpose of this article - to encourage robust boatbuilding techniques and more seaworthy vessels.

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There is a zero downside if you consider the problem can be solved, and has been solved, with a simpler technique that does not make a solid joint necessary.

funseeker said:

David Pascoe who was a long time yacht surveyor (and critic of current manufacturer laxity) wrote many times about how bad it is to affix the decks to hulls of large vessels with self tapping screws. Here is one article: https://www.yachtsurvey.com/Screwit.htm He and most marine engineers will agree - self tapping screws alone is a bad idea.

There's not too much concern that the kind of permanent tabbing of the deck to the hull as I described above would present an engineering problem. It will not appreciably alter the overall flexion (torsional twist) of the vessel being so far out on the perimeter. Also the idea that such permanent affixing of the deck to the hull would be contraindicated because it would preclude the removal of the deck from the hull is not really an issue. I have never seen or heard of an attempt to separate a 40 ft Sea Ray in this way. Most of these manufacturers have engine removal access methods and procedures involving the removal of the helm or deck panels that facilitate engine removal so there would be little need to remove the entire deck from the yacht. If for some rare reason that would be required, running an ablative cutoff saw along any tabbed joint would be the least of the issues in such a colossal operation.

The twisted shaped screws that often are seen in vessels which have not even slammed against docks is evidence that even during normal operations the forces on these small screws are too great. Fiberglass laminates are simply not designed for the kind of tensile strength required to withstand pounding momentary sheer forces at such small points - so what occurs is that during such momentary forces as two fiberglass panels exert force against each other, the tiny screw threads holding the two opposing panels dig into the fiberglass laminate matrix and essentially pulverize it a tiny bit. And then with the next momentary force (wave) it happens again, ever so small each time. Over time though the fiberglass laminate becomes fatigued at the point of entry of the screw by the sheering forces of the opposing fiberglass edges. And the screw by receiving repeated sheering forces - also shows signs of fatigue via the squiggly bends often found in screws along the rubrail line. The bent screw now grinding more of the already elongated screw hole until the screw hole is just a loose powdered large elongated hole no longer able to perform its function.

There is zero downside to making this a solid joint - strength, impact resistance and waterproofness are all improved if care is taken to make this joint as good as it could be. Strength at this important junction is also critical to surviving encounters with docks or objects that may occur during hurricanes or other adverse conditions. The only downside is that people are not demanding this proper construction methodology so manufacturers are happy to not provide it. It would literally take no more than a half hour of time at the factory and a relatively incremental increase in material cost to achieve significant improvements in strength, impact resistance and waterproofness at this vital junction. I like to design and build for when conditions are at their very worst - you'll thank yourself should you ever get caught in fierce conditions. Hopefully articles like this will encourage robust boatbuilding techniques and more seaworthy vessels.

Click to expand...

"Article"

techmitch said:

"Article"

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I did read the article. If David Pascoe is your go to guru, you should read his post of 5/20/1999. It is on his blog along with numerous others concerning boat manufacturing practices. The post is titled, "Tiara: The new quality leader?" Among the things he singles out about Tiara boats is the hull/deck joint. It's a shoe box design using screws. There are lots of 20 year old high hour Tiaras around that have never had joint failures. The design is robust and well executed. It's also pretty simple and easier to build than a solid deck/hull design.

funseeker said:

David Pascoe who was a long time yacht surveyor (and critic of current manufacturer laxity) wrote many times about how bad it is to affix the decks to hulls of large vessels with self tapping screws. Here is one article: https://www.yachtsurvey.com/Screwit.htm He and most marine engineers will agree - self tapping screws alone is a bad idea.

There's not too much concern that the kind of permanent tabbing of the deck to the hull as I described above would present an engineering problem. It will not appreciably alter the overall flexion (torsional twist) of the vessel being so far out on the perimeter. Also the idea that such permanent affixing of the deck to the hull would be contraindicated because it would preclude the removal of the deck from the hull is not really an issue. I have never seen or heard of an attempt to separate a 40 ft Sea Ray in this way. Most of these manufacturers have engine removal access methods and procedures involving the removal of the helm or deck panels that facilitate engine removal so there would be little need to remove the entire deck from the yacht. If for some rare reason that would be required, running an ablative cutoff saw along any tabbed joint would be the least of the issues in such a colossal operation.

The twisted shaped screws that often are seen in vessels which have not even slammed against docks is evidence that even during normal operations the forces on these small screws are too great. Fiberglass laminates are simply not designed for the kind of tensile strength required to withstand pounding momentary sheer forces at such small points - so what occurs is that during such momentary forces as two fiberglass panels exert force against each other, the tiny screw threads holding the two opposing panels dig into the fiberglass laminate matrix and essentially pulverize it a tiny bit. And then with the next momentary force (wave) it happens again, ever so small each time. Over time though the fiberglass laminate becomes fatigued at the point of entry of the screw by the sheering forces of the opposing fiberglass edges. And the screw by receiving repeated sheering forces - also shows signs of fatigue via the telltale squiggly bends often found in screws along the rubrail line. The bent screw now grinding more of the already elongated screw hole until the screw hole is just a loose powdered large elongated hole no longer able to perform its function.

There is zero downside to making this a solid joint - strength, impact resistance and waterproofness are all improved if care is taken to make this joint as good as it could be. Strength at this important junction is also critical to surviving encounters with docks or objects that may occur during hurricanes or other adverse conditions. The only downside is that people are not demanding this proper construction methodology so manufacturers are happy to not provide it. It would literally take no more than a half hour of time at the factory and a relatively incremental increase in material cost to achieve significant improvements in strength, impact resistance and waterproofness at this vital junction. I like to design and build for when conditions are at their very worst - you'll thank yourself should you ever get caught in fierce conditions. Hopefully articles like this will encourage robust boatbuilding techniques and more seaworthy vessels.

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Are you a marine engineer?

I appreciate your feelings on the subject but quoting others and expressing your thoughts is not the same as actually building boats and taking them apart for a living. Sea Ray has been building boats for a long time and has long been considered the gold standard for the size boats they produced. Call me crazy .....but I would take any Sea Ray engineer's decisions over what David Pascoe wrote. Why? Because Sea Ray had to stand behind their product. David just complained on the web and walked away. Additionally, David was a Surveyor not a marine engineer which aligns him more closely with being a professional critic.

funseeker said:

Recommendation for manufacturers: Production vessels of 32 feet and above should make the design of this joining of the top to the bottom halves of the vessel such that the joining of these parts (arguably one of the most important joints in the boat) can be easily and properly facilitated by the labor force employed in performing this function.

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This is a build concept ive seen employed by a number of boat manufactures, for better then 10 years now. More interestingly, 80% of the boats I see built this way, are sub-32' trailer boats.

This reminds me of a conversation I had with the daughter of the inventor of Sea Cast.
He took it to a prominent manufacturer of boats that we are all very familiar with, and proclaimed that his product would end the use of structural wood products, making their boats last virtually forever, with zero rot. They laughed him out of the board room. "Why would we ever want to make a boat last forever?!" Bottom line, buy your production boat and do whatever you need to do to be satisfied with it for as long as you can.

sbw1 said:

View attachment 76382
I did read the article. If David Pascoe is your go to guru, you should read his post of 5/20/1999. It is on his blog along with numerous others concerning boat manufacturing practices. The post is titled, "Tiara: The new quality leader?" Among the things he singles out about Tiara boats is the hull/deck joint. It's a shoe box design using screws. There are lots of 20 year old high hour Tiaras around that have never had joint failures. The design is robust and well executed. It's also pretty simple and easier to build than a solid deck/hull design.

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You mentioned that Tiara uses "copious amounts of polyurethane construction adhesive" - Thats called a permanent solid joint and was one of the recommendations I made in my article alongside tabbing.

David Pascoe had a lifetime of experience, not only in using and surveying boats, but also building and refitting them, and he was not affiliated with any particular boat manufacturer.

I have owned three Sea Rays over the course of 40+ years. I have also read most of what Pascoe has written on the subject. You don’t have to be a professional engineer to understand what he is saying. Much of it is simple mechanics or even just common sense.

Many of Pascoe’s criticisms of Sea Ray boats are reasonable, including the deck-hull joint issue. In each of my boats, I have found that Sea Ray has an unfortunate tendency to use short sheet metal screws and caulk to hold things together that should be through-bolted or glassed, and I have spent a lot of time on my boats correcting these deficiencies. I have come to accept this as part of owning a Sea Ray. So have many Sea Ray owners, judging from the content on this forum.

Sea Ray makes great boats. They are fun to operate, have nice lines, and have a generally decent design and build, but they are not the highest quality. If there’s a gold standard for US production pleasure boats, it’s Hatteras and some others, perhaps including Tiara. But I would not apply that term to Sea Ray.

PlayDate said:

Are you a marine engineer?

I appreciate your feelings on the subject but quoting others and expressing your thoughts is not the same as actually building boats and taking them apart for a living. Sea Ray has been building boats for a long time and has long been considered the gold standard for the size boats they produced. Call me crazy .....but I would take any Sea Ray engineer's decisions over what David Pascoe wrote. Why? Because Sea Ray had to stand behind their product. David just complained on the web and walked away. Additionally, David was a Surveyor not a marine engineer which aligns him more closely with being a professional critic.

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I built my first hydroplane racer at aged 13 and have had 6 boats in the intervening years since then and worked on many others. I come from a family of engineers (my father working on the Apollo Program.) I will take you up on the offer and call you crazy, firstly for the claim that Sea Ray is the "Gold Standard". It most certainly is not. I know that is not going to be a popular opinion on a Sea Ray boat owner's forum but if you've ever dismantled a large Sea Ray you would not make that claim. They are very definitely NOT the Gold Standard - not even close. And secondly you'd be crazy for taking a "Sea Ray engineers" decisions over a Yacht Surveyor. Sea Ray "engineering" is driven by accountants my friend not marine engineers. The bottom line is profits - NOT exemplary marine engineering. They're cocktail party boats not Nordhavn's. They are basically Bayliners with nicer aesthetic lines and interiors but they are Bayliners at heart.

funseeker said:

They are basically Bayliners with nicer aesthetic lines and interiors but they are Bayliners at heart.

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What are you basing that statement on? I walked the production line at the Homecoming. Bayliners on my left and Sea Rays on my right. The hull construction difference between the two was substantial.

lawndoctor said:

David Pascoe had a lifetime of experience, not only in using and surveying boats, but also building and refitting them, and he was not affiliated with any particular boat manufacturer.

I have owned three Sea Rays over the course of 40+ years. I have also read most of what Pascoe has written on the subject. You don’t have to be a professional engineer to understand what he is saying. Much of it is simple mechanics or even just common sense.

Many of Pascoe’s criticisms of Sea Ray boats are reasonable, including the deck-hull joint issue. In each of my boats, I have found that Sea Ray has an unfortunate tendency to use short sheet metal screws and caulk to hold things together that should be through-bolted or glassed, and I have spent a lot of time on my boats correcting these deficiencies. I have come to accept this as part of owning a Sea Ray. So have many Sea Ray owners, judging from the content on this forum.

Sea Ray makes great boats. They are fun to operate, have nice lines, and have a generally decent design and build, but they are not the highest quality. If there’s a gold standard for US production pleasure boats, it’s Hatteras and some others, perhaps including Tiara. But I would not apply that term to Sea Ray.

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Agreed. Pascoe's writings are an invaluable resource for marine engineers and boat builders, always thoughtful and always correct and thorough.

Also agree that you don't need to have a degree in Marine Engineering to observe failures, gain an understanding in how those failures occurred, gains an understanding about the properties of the materials involved, have a lifetime of experience in working with these materials, to understand proper marine engineering. At least aspects of proper marine engineering. I chalk up the naysayers here as being in the category of "owners of vessels not wanting to hear about deficiencies in said vessels".

I wish them the best of luck should their vessel crash into bulkheads during a hurricane, I surely do but I prefer solid, correctly manufactured vessels.

Its not a difficult concept to understand that fiberglass layups are not designed to be screwed into. Fiberglass just doesn't work that way. No degrees are required to know the basic properties of fiberglass, its actually pretty simple. Why anyone would take the position that screws into fiberglass is good idea just because a profit driven corporation has decided to cut corners in this way is baffling. And these people seem adamant that it is wrong to suggest the obvious, long standing, well known, FACT that fiberglass is not a good screw holder. You don't have to be a marine engineer, you just have to know the basic properties of fiberglass panels and this information is capable of being grasped by high schoolers (even jr high schoolers).

So to finish this: Number 8 self tapping screws to join the hull to deck of 40 foot yachts is a bad idea. It is a bad idea if you have a degree in marine engineering, or if you flunked elementary school. It is a bad idea if you are Steven Hawkins or Jimmy the village idiot. It is a bad idea if you are happy or sad, if the weather is nice or bad. It is a bad idea in the morning, the afternoon and all the live long day. Screwing together fiberglass hulls is AGAINST marine engineering. Why people feel it necessary to defend unsound poor marine construction techniques is astonishing.

ZZ13 said:

What are you basing that statement on? I walked the production line at the Homecoming. Bayliners on my left and Sea Rays on my right. The hull construction difference between the two was substantial.

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Basing it on experience. I've dismantled them to fix the many manufacturing problems therein. Hence my recommendations that they make incremental improvements on their hull to deck fitting. Its not the end of the world that someone dares to suggest that a profit driven corporation adhere to sound marine principles. And its not really that far of a stretch to make the comparison of Sea Rays (and most other production boats for that matter) to a Bayliner. They are all driven by accountants and profits and much less by the passion to build quality boats.

Hence my comparison to Bayliners, but to be fair most production boats are byliners at heart because it's ACCOUNTANTS who are in charge - not marine engineers.

the fiberglass is not being screwed into, The screw head is seated into the SS rub rail and the threads are into the plywood strip inside. The upper and lower fiberglass shoebox are sandwiched between the 2.

scoflaw said:

the fiberglass is not being screwed into, The screw head is seated into the SS rub rail and the threads are into the plywood strip inside. The upper and lower fiberglass shoebox are sandwiched between the 2.

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Incorrect. It's not plywood, its a composite fiberboard. (also not a good screw holder) In my article I described the sheer forces from the panels (of the shoe box) exerting sheer forces against the screws causing greater or lesser degrees of failure at the point where the screw threads meet with the sheer forces of the panel. Screwing hulls to decks with number 8 self tapping screws is a bad idea and incorrect marine engineering, and there is not a single marine engineering recommendation in the literature that would recommend screwing boats together in this way. Hope this helps with your confusion on this matter. Happy motoring!