Osprey marine (and RV) composites logo header
osprey logo bullet

Home

osprey logo bullet

About Us!

osprey logo bullet

Services

osprey logo bullet

What's In House

osprey logo bullet

Osmotic Blister Repair

osprey logo bullet

Burn Blister Repair

osprey logo bullet

Awlgrip Paint System

osprey logo bullet

Collision Repair

osprey logo bullet

Deck/Core Repair

osprey logo bullet

Custom Fabrication

osprey logo bullet

Open Console HardTops

osprey logo bullet

Keel Repair

osprey logo bullet

Fuel Tank Pull

osprey logo bullet

Customer Inquiry Form

osprey logo bullet

Contact Us

osprey logo bullet

Testimonials

osprey logo bullet

Links




    OSMOTIC BLISTER REPAIR

    THE PROBLEM

    If yacht hulls spent most of their lives in air rather than water, the Water Soluble Materials (WSM), which composes them, would be saved from the blight of blisters. However, the majority of vessels are simply not adaptable to high and dry storage facilities. So, understanding how water permeates a hull is crucial to grasping the osmotic process.

    Hydrolysis is the ability of water to break down and alter the chemical bonds of polyester resins. It is through permeation that water comes into contact with WSMs suspended in the laminate layers. Professional Boat Builders Magazine in its February 1992 issue lists several known WSMs: MEKP, Silica compounds, PVA, styrene, and the binders in chopped strand matt, just to name a few. It was further noted that a reaction of the water and WSMs left behind a corrosive material, which created ?fiber whiting?. Fiber whiting occurs when resin surrounding the fiber has been hydrolyzed or has totally dissipated. In many older vessels you may only see crazing or cracking of the gelcote. You may never see a blister. In this scenario, the gases created by water reacting with WSMs simply escape through the lesions in the gelcote.

    A blister forms when the permeation of water into the laminate exceeds the flow of hydrolyzed fluid trying to escape. The solution, now increased in molecular size, cannot readily pass through the laminate structure. The WSMs are hydroscopic and this absorbing capability attracts more fluid into the same void. It is the continuous attraction of the additional WSMs and their chemical reaction in a limited space, which creates the blister. This usually occurs more rapidly in gelcote with a tight molecular structure. The accumulation of a large number of blisters will, in turn, create a serious hull delamination. The degree of structural damage will increase as the blisters fracture and penetrate deeper into the layers of the hull.

    THE SOLUTION

    Osprey Marine Composites, Inc. always begins the blister repair process with a laminate profile. The profile consists of four steps. First, high-speed grinders remove a sample of material at selected sites. Second, depth calipers record the thickness of each layer that is removed. Third, a moisture meter determines the amount of moisture in each layer. Fourth, a Barcol Impressor determines the amount of resin deterioration. This information determines the repair procedure, i.e. how much material has been damaged and must be removed and replaced with new material.

    The next step is to remove the damaged material. The hydraulic peeler is set to the appropriate depth, and the damaged material is removed evenly over the entire hull. A hard sanding of the hull follows this procedure.

    The next phase of the repair is to dry the hull. It is our opinion that the vessel must be dried to a reading of less than 10 on an Electro physics moisture meter. With a low reading, only a minimal amount of moisture is trapped in the hull and a higher degree of secondary bonding between the original resin and the new material will occur. Some hulls dry very quickly after the peeling process. Others may be force dried with propane heat alternated with moving air.

    If more than 80 mils of material had to be removed, the vessel will usually require a new laminate. OMC uses Knytex 1808dbm structural fabric for all re-laminations. This is a state of the art boatbuilding fabric which adds strength to the hull. Unlike chop strand matt, this fabric contains no WSMs. If less than 80 mils of material is removed, usually a barrier coating is all that is required. In either case, the hull is faired to original shape before the barrier coating is applied.

    FAIRING AFTER LAMINATE

    OMC uses a Dow Chemical vinyl ester resin for both re-laminations and barrier coatings. This is a top of the line vinyl ester resin which is considerably more expensive than commercial v.e. resin, and has excellent moisture barrier properties.

    All OMC warranty barriers are applied to a thickness of 50 mils of vinyl ester resin. OMC gives a three year warranty to boats with barrier coat only, and a five year warranty with re-laminations. One coat of anti-fouling paint is included with both repair packages.


© 2017 Osprey Marine Composites® ®