Osmosis

Osmosis from the Perspective of Builder and Naval Expert Sergio Boghi, a Master!

What is OSMOSIS? … Like asking who Carneades is?

Premise:

• Since 1970, I have built and inspected for various reasons over 14,000 sail/motor hulls.
• None of these vessels have ever sunk due to the presence of the osmotic process.
• The only ones that sank or were seriously damaged were solely due to impacts against rocks (Zirri, etc.).

Therefore, defining osmosis as the “cancer” of fiberglass is not correct, or at least not as it is intended.

To make a physical comparison, we can say that “proper” osmosis is like a rheumatism problem. If symptoms appear after the age of 60, it will be diagnosed as physiological. However, if the problem appears at 20 years old, the doctor would say it is a pathological issue requiring examinations/treatment.

Translated: a) – If osmosis affects a fiberglass hull after 15 years of use in water, we can classify it as physiological. b) – If osmosis affects the boat within the first 5 years, we are faced with a pathological process.

Having addressed:

• the process that was triggered in a),
• let’s now examine the “drama” of b).

Osmosis in fiberglass is a process that is triggered:

• in the presence of materials and/or SEMI-permeable barriers that, when immersed and/or in contact with liquid/saltwater/freshwater, absorb it.
• in the presence of a fiberglass composite, water, thanks to Archimedes, travels inside the laminate starting from the gel coat and then affecting subsequent layers.
• if the gel coat is of good quality and thickness ≥ 40µ/0.4mm, and if lamination has been done properly, meaning there are no spaces/voids between the various layers of the laminate, it absorbs minimally and then dries when the hull is out of the water. All this without the formation of “blisters.”
• If, on the other hand, the laminate was not correctly laminated, thus presenting pockets/voids/poor resin impregnation, combined with a gel coat of poor quality and inadequate thickness, saltwater or freshwater (the latter being worse) carries into the laminate (simple skin), filling voids, dissolving the resin through hydrolysis, and increasing volume and pressure. From here comes the formation of blisters, which must be “circular” (otherwise, it is something else), and based on:
• the diameter of the blisters.
• the depth of the “crater”/affected layers.
• the color of the liquid from clear to caramel.
• the density of the liquid.
• the pressure at which the liquid exits as “splash.”

You can determine +/- the period of onset of the phenomenon. Many of us have seen hulls both sail and motor where the former are more numerous due to greater time spent in the water.

Returning to point b), we can say that we are dealing with a boat that was not built correctly, and the immediate sudden appearance of osmosis has only highlighted a laminate affected by delamination between the various layers. This phenomenon can be attributed to a deficient construction phase by the builder, due to various causes:

• Construction of the hull within unconditioned environments/structures.
• Use of poor-quality materials such as poorly stored orthophthalic resins, etc.
• Use of low-quality gel coats and inadequate thickness.
• Use of Mat/styrol fiber/tissues stored outdoors in unsuitable environments (humidity).
• Construction of a hull on a pre-laminated mold: gel coat + 2/3 layers of lining, left waiting for sale.
• Resuming new lamination on a pre-laminated mold must be preceded by a correct preparation of the last state of the outer lining/Mat with careful sanding, perfect cleaning, and a coat of styrol to facilitate optimal lamination/adhesion of the next layer.
• If the described work presents flaws/detachments/faulty adhesion/poor resin impregnation/new interruptions in the lamination process with intervals exceeding eight hours without recourse to new preparation, it is normal for the laminate of the produced hull to be technically/chemically deficient.
• The osmotic process will only be the “indication” of a much more serious problem.

Construction Example:

• The plaster of building A) remains intact and free of issues after over 30 years.
• The plaster of building B) presents falls, detachments, and swelling of plaster to the extent of being cordoned off after 8 years!

What conclusions can be drawn? Poor-quality materials, poorly prepared support, and incorrect application. At the center of ALL this is man.

Further phenomena/behaviors that can anticipate the development of osmosis. Having discussed semi-permeable