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Construction methods (and their trade offs)

43K views 354 replies 45 participants last post by  Shockwave 
#1 · (Edited)
Let's try this again. Leaving behind the crud that other threads have devolved into, let's actually talk about construction methods and design limitations. Try to keep it civil and non personal. Try not to brand bash. Try to realize that certain boats have to hit certain price points, but that doesn't mean they can't be seaworthy.
 
#4 ·
Thanks. If this fails, it will prove people are really only interested in pissing at each other and not interested in the real design elements. I'd like to have an intelligent conversation about some of these design elements. Some of them are done to be 'good enough' and save costs, but I'd like some more info on the trade offs. Bob's book is great, but it's only one perspective, and approaches the question a bit differently.
 
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#5 ·
I'm certainly watching. And I'll state this: From everything I've seen, liners are not evil. In fact, I think they make a lot of sense from a structural perspective if done correctly. It's simply a more holistic approach to strength that's been a part of architecture for a very long time (skin and structure working together). There's absolutely no inherent reason it should be inferior to overly thick layups.

And as I've also said before, and I'll say it again: I think the real question that people should be focused on is that of longevity. If the used boat market's mentality is that 40 year old boats are the strongest - I think we're in for a world of hurt in a decade. We should have SOME kind of idea from ALL manufacturers what the "half life" of a new boat is in given conditions.
 
#6 ·
I fear we don't have enough of the kind of experts we'd need for a good discussion on these topics, Sean.. but lets hope for some good dialogue.

One very amateur observation. On a variety of fronts I bemoan the disappearance of the once-deriguer 'slotted aluminum toe rail. It's convenience is obvious, and I recall seeing a video of an excavator trying to crush an old C&C for disposal. The rail's tenacity in holding the joint together under that attack was impressive. I can only believe that it also tremendously strengthened that whole structure as well.

Our friends currently cruising the Caribbean on a Bene 36.7 always comment that they wished that boat had such a rail, as ours does.
 
#7 ·
This is doomed to fail.

Every one will defend what they have as the best.

Very few people even know the difference between hull and deck joints or the advantages and disadvantages of stick built versus pan.

I really believe the best you can do is research the model and the maker of the boat you're interested in. Then decide if it fits your sailing plans.
 
#8 ·
This is doomed to fail.

Every one will defend what they have as the best.

Very few people even know the difference between hull and deck joints or the advantages and disadvantages of stick built versus pan.

I really believe the best you can do is research the model and the maker of the boat you're interested in. Then decide if it fits your sailing plans.
I don't disagree, but enough of us got sick of the production boat thread that I hope we can do better here.
 
#10 ·
I would like some insight on how my Boat is constructed. I have a CS 30 with a full liner, I think its one of the best built floors I have seen especially the mast step there has to be 5 or 6" of solid FG right there. It is part of the main grid then the liner sets on top of that as opposed to the grid and liner as one piece.
On these flat bottom designs how else are you going to get the strength needed in the bilge that you get with a deep keel and all those curved sections to add strength.
 
#11 ·
Ok- I still want to talk about deck to hull joints, but I'll go for the two things that have been thrown out so far.
The perforated toe rail- no doubt it adds longitudinal stiffness to the deck to hull joint as well as an easy way to attach stuff. Aesthetically, I like teak, but it's not as utilitarian. I'm guessing they got rid of these in search of a 'cleaner' look, and as a cost savings measure. Much like pop up cleats, which I think are asking for trouble.

Regarding liners, nothing wrong with them from an engineering standpoint. It's like a hollow core door. Skin carries the loads. The problem is that they are done so that all the systems are either inaccessible (esp plumbing and wiring) or they are broken into prefab compartments, which reduces that efficacy of load sharing and then on top of that they have no accessibility.
Properly done, with multiple access ports, with reinforcing bars around them and proper adhesion to the hull, they would be fine. I've yet to see one done that way. Maybe someone has pics of one done 'right'?
 
#34 · (Edited by Moderator)
Ok- I still want to talk about deck to hull joints, but I'll go for the two things that have been thrown out so far.
The perforated toe rail- no doubt it adds longitudinal stiffness to the deck to hull joint as well as an easy way to attach stuff. Aesthetically, I like teak, but it's not as utilitarian. I'm guessing they got rid of these in search of a 'cleaner' look, and as a cost savings measure. Much like pop up cleats, which I think are asking for trouble.

Regarding liners, nothing wrong with them from an engineering standpoint. It's like a hollow core door. Skin carries the loads. The problem is that they are done so that all the systems are either inaccessible (esp plumbing and wiring) or they are broken into prefab compartments, which reduces that efficacy of load sharing and then on top of that they have no accessibility.
Properly done, with multiple access ports, with reinforcing bars around them and proper adhesion to the hull, they would be fine. I've yet to see one done that way. Maybe someone has pics of one done 'right
Compared to the longitudinal stiffness given by your hull topsides and the deck , both the equivalent of longitudinal bulkheads, the toe rail contribution is tiny by comparison.
The best hull deck joints I have seen on stock plastic boats are those used on Fraser 41's and Rawson 30's. They consist of the hull continued up , against the deck molding edge, also turned up, the two sandwiched together to form the bulwark. This gives you a strong enough bulwark ( far stronger than the deck) to let you bolt the stanchion bases to the bulwark, leaving no bolt holes in the decks.
 
#12 ·
Our boat is nearly completely 'stick built'.. the only liner-like moldings are the galley module and the head compartment, which is a complete top to bottom side to side molding typical of Nicholson. Makes the head very easy to keep clean but almost completely hampers access to the hull in that area (a large removable shower sump is there, but clearance is thin elsewhere) that's the only part of the hull I can't get to from inside easily.

This enabled me to do some significant work in the floors area, both settees came out with a screwdriver, both tanks came out and went back in in one piece and all this without damage to the original pieces.

Our deck joint is a typical inward hull flange, overlapping deck throughbolted with said toerail. After 31 years there's no leaks, as far as I can tell it was originally set in Butyl.

We have friends with Hunters (80s/90s) and others with a Mirage 33 - both outward flanges with toerail throughbolted. I can see the advantage assembly wise (all outside hull) and the waterproof integrity must be easier to maintain too. It's the widest part of the boat by several inches and my biggest concern is when rafting up with these boats that we manage to get the fenders aligned with the protruding deck edge...
 
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#14 ·
Actually, I think it's probably the opposite. The waterproofing would be more likely to fail for at least three reasons-
1. The outward flange would wet out and allow rainwater or shipped green water to ride around under the deck lip, similar to the reason that a relief channel is cut under window sills. Can't happen on the other methods.
2. The repeated stresses of docking and rafting are translated at an angle to the protruding flanges and deck and the vector forces are not dispersed ideally. The 'lip' that is created is fairly weak compared to either internal flange or shoebox and more prone to upward flex, more likely compromising the sealant/adhesive used.
3. The sealant/adhesive is really what is holding these together, and application of adequate amounts of this without significant squeeze out takes skill.
 
#13 ·
Flanges.

Inward turned flanges, glassed and through bolted are generally considered the best. The advantage of an inward turned flange is the width of the flange can be increased to match the size of the boat. If the boat is 50 foot its possible to have a 5 inch inward turned flange.

With an outward turned flange the width of the flange is limited but aesthetics. There are 50 for boats with 1.5~2" flanges, there isn't a lot of strength there for a boat that size.

More later...
 
#18 · (Edited)
Take a look at the promo literature for PSC. Always liked the way they did the hull deck joint.
However for practicality prefer the slotted Al rail with inward flange through bolted and glued that I currently have It works great with the winchard attachment points.
Loved my T37 but hated the teak toe rail. Varnish would wear on the top and lift from the bottom. Even when going through the exercise of wooding it, the 1/2 strength Epiphanes then build up to 7 coats. Interestingly varnish elsewhere on the boat would last much better just needing a touch up and light sanding.
Can't convince me a liner is a good way to make a boat. There's still a grid which you can't see. In fact you can't see most of the structural elements. Beyond simple maintenance and improvements see boats suffering major deconstructive surgery to deal with tanks and such. Tracing a fresh water leak is problematic at best.
There was a truly unsinkable boat made in Belgium(?) much like a whaler. Forget the brand. Then it made sense as that space was filled with foam.

Another thing I think cruising boats should have is a rub rail. I'm surprised when it's an option or just unavailable. With the outward flange the flange is the rub rail. That can't be good over time.
 
#21 ·
Can't convince me a liner is a good way to make a boat. There's still a grid which you can't see. In fact you can't see most of the structural elements. Beyond simple maintenance and improvements see boats suffering major deconstructive surgery to deal with tanks and such. Tracing a fresh water leak is problematic at best.
Geez, you really don't get it, do you? "Having to deal with tanks and such" is a sure sign that the boat has reached its "HALF-LIFE", and it's time to move on, and pawn off those problems to some other poor sucker...

;-)

There was a truly unsinkable boat made in Belgium(?) much like a whaler. Forget the brand. Then it made sense as that space was filled with foam.
You're thinking of Etap, I presume... The couple that I were aboard seemed like pretty nice boats, and I was surprised how little the interior volume seemed to be compromised by the floatation. Friend of mine sailed one for awhile, he loved the boat and how it performed under sail. I almost got to deliver it a couple of years ago, and was disappointed when that deal didn't happen...

I believe Sadler also made some 'unsinkables', another boat that looked like a nice design, to my eye... Not sure if they're still in business, or not...

Another thing I think cruising boats should have is a rub rail. I'm surprised when it's an option or just unavailable. With the outward flange the flange is the rub rail. That can't be good over time.
"Rub Rails ???" Damn, you Scared Old Excitable Hens want EVERYTHING !

Rub rails have truly become an anachronism, just look what those Industry Leaders are putting out these days... What do you think bow thrusters, Joystick 360 Docking Systems, and fleece-covered fenders are for?

C'mon, out, this is the 21st century, time to get with the program...

;-))
 
#22 ·
Yup
It was ETAP. They made a 39' and briefly a 46' with an exotic African wood intererior as an option. They sailed quite well. Was a 39' in buzzard bay for a few years saw him up there and at Sopers so guess seaworthy too.

Have a thing about dark blue or black hulls. Be the first to admit they look great when new or if done well with a fresh coat of Imron or Awlgrip. Understand how they improve the lines and looks of some boats but:

A few years of tropical sun they fade. That's OK I like a faded look but they fade unevenly so look like they are ill and in pain.

They are hot. Bad for us humans but the heat/cooling cycle every day can't be good for the boat.

They show every little ding, scratch or imperfection in the paint job. Even the minute swirls from buffing the wax job.

I understand black coal tar epoxy on a steel hull but not on pleasure craft.

I see them much more frequently now. I wonder is it" I've arrived-money is no object". Or "Gee Harvey wouldn't it look nice in blue - I have towels in blue".

Think the Wizard was right "white or the wrong color".

bitching because I hate trying to match gelcoat.
 
#33 ·
Yup
It was ETAP. They made a 39' and briefly a 46' with an exotic African wood intererior as an option. They sailed quite well. Was a 39' in buzzard bay for a few years saw him up there and at Sopers so guess seaworthy too.

Have a thing about dark blue or black hulls. Be the first to admit they look great when new or if done well with a fresh coat of Imron or Awlgrip. Understand how they improve the lines and looks of some boats but:

A few years of tropical sun they fade. That's OK I like a faded look but they fade unevenly so look like they are ill and in pain.

They are hot. Bad for us humans but the heat/cooling cycle every day can't be good for the boat.

They show every little ding, scratch or imperfection in the paint job. Even the minute swirls from buffing the wax job.

I understand black coal tar epoxy on a steel hull but not on pleasure craft.

I see them much more frequently now. I wonder is it" I've arrived-money is no object". Or "Gee Harvey wouldn't it look nice in blue - I have towels in blue".

Think the Wizard was right "white or the wrong color".

bitching because I hate trying to match gelcoat.
When I go south of Cabo I paint my topsides white. Much cooler. In northern latitudes ,while I had white topsides, the lockers got musty in winter. When I went back to dark green ,they dried out and the mustiness left quickly. When frozen in ice at minus 12 degrees celcius, my hull feels warm to the touch, in bright sunlight.
So I go white for the tropics, and dark green for northern latitudes.
Painting over epoxy tar is no problem. You have to get your top coat on the epoxy tar while it is still wet, or it wont stick. The epoxy tar will bleed thru , and it will look like hell. Give it another colour coat, which it will also bleed thru. Leave it for several weeks or more to harden. Then you can paint it any colour you like, with no more bleed thru.
 
#23 ·
My primitive understanding of the tradeoff in hull/deck joints:

The outward flange is limited in contact area (size) by how far you are willing to have it protrude from the hull without damaging esthetics.

The inward flange can be as big in contact area as you want it to be, sized to get the right hull/deck joint integrity, but more work to build because extracting the product from the mold implies additional steps (multi-part molds).


My primitive understanding of drop pan liners vs stick built:

The drop pan liner provides strength by bonding an additional structural liner to the hull built of more FG. This is less work and less costly than stick built.

Stick built boats use bulkheads and furniture tabbed to the hull to provide the same.

Either could provide the structural strength required in theory. An unfair generalization, but IMHO mostly true, the drop pan boat is harder to repair and can be problematic if systems are buried beneath the liner, the stick built boats tend to be heavier.



These are consumer level opinions from someone who's owned a variety of boats with these features, I would appreciate someone on the inside of the business offering insights.
 
#24 ·
Any handsome boat with a dark coloured hull will stand out in the crowd of white.. Black, Flag Blue, British Racing Green, with eye-catching contrast in boot, cove and maybe canvas all combined with a sweet sheerline - a 'Wow' moment for sure.

But Out's right about all the downsides, and in the tropics esp I'd imagine the heat issue is a major one.

As mentioned elsewhere (CCA thread?) a nice grey is enough to separate you from the crowd, and yet doesn't really suffer from those issues. Not to the Battleship grey level, but we liked the Awlgrip Whisper grey on our last boat. We also went with a fairly bright white on deck, despite 'glare' fears; everyone wears (or should) good UV blocking eyewear, and the coolness underfoot in summer was appreciated.
 
#25 ·
Forgot to mention others colors.
Faded red is just an eye sore.
In the bucket saw a mega yacht in hi viz yellow. Had to turn away and gag. OMG beautiful boat but what were they thinking.

Now with that off my chest let's talk about tankage. For a cruiser there is never too much. Often wondered why you never see water ( or fuel) ballast. Loved how the Besteavers do their tankage.
Understand we are not racers so losing interior volume to large salt water tanks makes no sense but on the plus/minuses multiple integral tanks for stuff we need anyway seems a good idea. It's rare a cruising boat has enough people on board to make for meaningful rail meat.
Multiple tanks means less sloshing around even with baffles so less foam in the fuel. Multiple tanks means redundancy and safety. If one is contaminated or leaks not the end of the world. Multiple tanks means they're easier to stick in amidships so trim won't change as much as they are emptied.
But on small boats you see one big tank under the forward berth or under the quarterberth. On new boats, given the absence of slack bilges or volume under the ceilings you see them in weird places.
Any thoughts beyond saying it's the money honey. Thinking about this you are not talking about a big jump and it would distinguish the boat from the pack for many sailors.
 
#26 ·
My four carbon cutters have all their tankage in the keel. This helps to give us a VCG 1.67' below the DWL This is unheard of in most cruising boats. The tanks will not be integral but will be custom. form fit fuel cells.

As for rub rails: I like them. My new cutters have composite rub rails with a stout teak cap. Rb rails also give me an additional aesthetic element to play with.
 
#27 ·
Agreed. Really like grey. Even shows the tannin mustache less than white. Particularly like well done, seamless looking Al hulls. Especially when there's no hungry horse look to them. Keep my boat white and shiny because I want to preserve the gelcoat but that flat grey look seems very businesslike and masculine.

Saw a Gunboat in grey. Very striking and beautiful.
 
#42 ·
Agreed. Really like grey. Even shows the tannin mustache less than white. Particularly like well done, seamless looking Al hulls. Especially when there's no hungry horse look to them. Keep my boat white and shiny because I want to preserve the gelcoat but that flat grey look seems very businesslike and masculine.

Saw a Gunboat in grey. Very striking and beautiful.
Gray makes a boat extremely hard to see at sea, or even in some anchorages, making you far more likely to get run over.. Any gray is exponentially hotter in the sun than white. Bare aluminium gets hot enough to burn the soles off your feet. I had to paint the bottom of my aluminium dingy white , while in the tropics, to stop that problem.
 
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#29 ·
Out:
On the later Valiants the rail was molded as an integral part of the hull, foam filled and them glassed over on the inside. A teak or s.s. cap was added according to owner choice. The idea was to make it a stringer type structure. It does add stiffness to the topsides. It's the perfect shape for the job.

On the carbon cutters the rub rail is external to the topsides laminate so it definitely will add some stiffness but we did not design it as a required structural member, just a rub rail.
 
#35 ·
Out:
On the later Valiants the rail was molded as an integral part of the hull, foam filled and them glassed over on the inside. A teak or s.s. cap was added according to owner choice. The idea was to make it a stringer type structure. It does add stiffness to the topsides. It's the perfect shape for the job.
That rubrail has always been one of my favorite features on the V-42, it's damn impressive...

I've suggested to the owner of VALHALLA that he add some short sections of nonskid tape on the top of the rail at both the lifeline gates, and up by the shrouds... When climbing back aboard from either a low floating dock, or a tender, it's actually wide enough to serve as a step - at least if your feet aren't too big, and you exercise some caution... If it were my boat, I'd even add in some teak 'leveling' strips, to make it truly horizontal in those 2 spots...

Now, THAT is a proper rubrail...

;-)
 
#32 ·
I have no particular bias regarding the hull to deck joint construction but I do have a boat that shows some wear. Please see the link to a short video I put together for this thread...



So what do you think?
Looks like you need some sealant, re fastening and a new rub rail. That out-turned flange is a good example of what's wrong with that method.
 
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