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Author Topic:   Fiberglass Hull Construction Methods
menahaunt11 posted 03-06-2012 05:32 PM ET (US)   Profile for menahaunt11   Send Email to menahaunt11  
I'm fairly unfamiliar with boat building, but came across a construction description from a custom boat builder in the Caribbean that grabbed my attention and curiosity. It is as follows:

Each boat is manufactured with solid hand laid fiberglass (no core). The lapstrake construction process used for over 100 years adds to the torsional stiffness, preventing twist and flex...hand laid manufacturing process is overlapped at the chines, keel and transom using only top quality materials.

I've only had my 22' Outrage for a couple years now and have a very basic understanding of how the boat was built. My curiosity stems from the "no-core" aspect of this description. What does this mean? Isn't foam generally the "core" of the boat? What does the lapstrake process entail?

Also, please correct me if I'm wrong, but didn't the classic whalers have hand-laid fiberglass as well? What are the benefits of this process?

Appreciate any enlightenment you all could provide, I'm always interested in learning more about my whaler and its storied history/reputation, particularly with regards to its construction and the resiliency of its components


Jessielove posted 03-06-2012 06:40 PM ET (US)     Profile for Jessielove  Send Email to Jessielove     

I believe they are referring to a solid glass boat compared to a boat that may have a sandwich construction method (if you will) where the bread of the sandwich is fiberglass (hand laid or chopper gun applied), and the meat between the bread is foam, balsa, or another material like wood or plywood. Each has its advantages and disadvantages. A lot of fiberglass deck hatches and cabin tops, for example, are constructed this way. They appear to be one solid layer, but if cut will reveal an interior core of balsa, foam or plywood). The combinations of materials provide strength, weight savings, impact and abrasion resistance, and the glass seals the core from moisture. Cores are not a bad thing is used and executed correctly in the design and building of a boat. They tend to be easier damaged by poorly sealed fastener holes - water gets in and can't get out. The closed-cell foam in a whaler hull tends to be more resistant to water intrusion than say a plywood core on a hatch cover.

This is not to be confused by BW's Unibind construction which essentially are two layers separated by a varying distance that creates the shape and varying thickness of the hull and then bonded together with closed cell foam under pressure.

I suspect the builders you refer to have a mold that results in a fiberglass hull that resembles lapstrake constructed wood boats. Lapstrake construction of wood is sort of like siding on a house. To create this profile shape, they probably build up fiberglass in the areas that represent the overlap areas and thereby create ridges of added thickness, sort of like the idea of folding a piece of paper and the seam makes the paper stiff enough to stand up into the air if set on a flat surface.

The closed cell foam core of a BW is not the same thing as a core (think sandwich again) that makes up a layer of laminates.

Binkster posted 03-06-2012 08:13 PM ET (US)     Profile for Binkster  Send Email to Binkster     
Lapstrake fiberglass boats offer no structural advantages over a smooth sided glass hull. In the beginning, back in the '50's lapstrake glass boats were fairly common as builders used existing wooden boats for plugs, and many of these plugs were wooden lapstrake boats. There are no stiffeners in the sides of these boats, its only cosmetic. Back in the day, lapstrake wooden boats were common. and the laps were usually copper riveted or brass bolted together. You can only do so much, design wise, with plywood, and smooth planked(carvel) construction means that all the flush seams needed to be caulked. It took very experienced craftsman to build these wooden boats. Then for a short time in the late fifties glass boat builders realized that they were not confined to reproduce traditional boat shapes, and boats began appearing that looked like cars of the day with giant tailfins.
I don't know of any boatbuilder today that builds glass lapstrake boats, I guess its a styling thing. This builder you speak of may have an old lapstrake mold or made one from a wooden lapstrake boat.
As far as hand laid, I guess its in the translation of the term "hand laid". It actually means cutting pieces of mat and roving, and laying them in the mold by hand and glassing the pieces in. Years ago while on a tour of the Dusky (Mako Knockoff) plant in Miami, our tour guide mentioned that the boats sere "{hand 'aid") while actually there was an operator shooting a chopper gun, while a couple of helpers rolled the glass against the mold. I mentioned that the method was not hand laid, and the guide said that the chopper gun was operated buy a person. Oh, well.
Jefecinco posted 03-07-2012 09:44 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     

In my memory Penn Yann (spelling???) was the last quantity builder making lapstrake "looking" fiberglass boats.

I liked the boats "look" and recall they made some smallish inboard powered boats with propeller pockets. I can almost sort of remember a 30ish footer they also made.


andygere posted 03-07-2012 12:40 PM ET (US)     Profile for andygere  Send Email to andygere     
There are plenty of modern fiberglass boats built today with faux lapstrake hull forms. Here's a very popular example, the C-Dory:

The fiberglass strakes do provide some benefit for deflecting spray, and also provide some additional stiffness.

From the C-Dory website: "Heavy plank lines along the sides contribute to the C-Dory’s classic, salty appearance. They also stiffen the hull and serve as spray knockers, making the boat pleasantly dry running."

Stevebaz posted 03-07-2012 06:38 PM ET (US)     Profile for Stevebaz  Send Email to Stevebaz     
A chopper gun and guys rolling out the material to consolidate and remove air pockets is concidered hand laid.
As opposed to using a chopper gun and vacum molding or pressing between molds to consolidate and cure.
Binkster posted 03-07-2012 10:16 PM ET (US)     Profile for Binkster  Send Email to Binkster     
So the the term hand laid fiberglass only relates to the guys with the rollers, rolling the glass into the mold. In the old expression of hand laid, the guys cutting the mat and woven roving into manageable pieces and laying it into the mold and wetting it out don't have anything to do with that term. Of course there are guys with rollers in that operation too.
I guess as long as humans are involved in some way in the manufacturing of a product, it can be considered hand made.
pete r posted 03-08-2012 08:33 AM ET (US)     Profile for pete r  Send Email to pete r     
Basically if you want a structure to be strong and light then hand laid glasing is the only way to go.
This method achieves a constant uniform thick fibreglass skin which is strong and light weight. The skin or shell is great for race boats, sail boats, surfboards, canoes etc.

Sheets of fibreglass fabric up to 1.2m wide and are spread neatly hand laid over a mould and carefully worked to copy the exact moulds shape.
When a number of glass layers are applied and cured correctly between sessions. This time consuming method can achieve an amazing strength to weight characteristic.

The chop matt process I think is a more crude method of fibreglasing and commonly used in mass produced craft where strength to weight ratio is not a huge consideration.

Equivalent strength in this process is cost effectively achieved by simply making the shell thicker, but unfortunately that means heavier. I imagine the repair of this of construction to be more straight forward than the laid method.

Both construction methods have their merits however I reckon it makes better sense for fishing boats to have the later method of construction.
The idea of having a chunky heavier boat when you hit something in the water or bounce across that shallow bar you weren't expecting worries me.
These days I prefer that dull thud noise as apposed to that slapping/ring sound of the lighter boat.

The down side of a heavy boat is the larger motor required to get her on the plane. Then there are the towing issues.

jimh posted 03-11-2012 02:40 PM ET (US)     Profile for jimh  Send Email to jimh     
[Changed the TOPIC. It was "Whaler Construction," but the discussion was about everything but Whaler construction.]
jimh posted 03-11-2012 02:42 PM ET (US)     Profile for jimh  Send Email to jimh     
Bends or ridges, such as might appear in a faux-lapstrake fiberglass boat hull, tend to add rigidity and strength to a panel. A smooth and even panel tends to flex.

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