The basic technique involves both chemically bonding and mechanically fastening
the C-Flex to the wooden hull. The C-Flex is applied vertically from gunwale to keel so that the rods in the C-Flex run perpendicular
to the wooden planking. The mechanical fastening is accomplished with heavy staples, and the chemical is done with an elastomeric
The C-Flex is then saturated with resin and covered with chopped strand mat (CSM).
A fairing compound is applied to the exterior, and the compound is sanded and painted.
The Adhesive - The adhesive used to bond the C-Flex to the wood
is a moisture-cured elastomeric polyurethane which was developed for marine use. It has several characteristics, which make
it an excellent material for the bonding agent. First is that it bonds ferociously to both the C-Flex and the wooden planking.
Secondly, it will bond to wet wood, treated wood, and virtually all the various types of woods used in marine planking. Add
thirdly, being an elastomeric, it will stretch (300%) and compress without breaking its bond. This is essential in preventing
the delamination, which might otherwise be caused by the expansion and contraction of the planking and by the “working”
of the hull.
C-Flex – C-Flex is a fiberglass planking that was developed
for “one-off” fiberglass boatbuilding. It is a high strength (67,000 p.s.i. tensile) material, which contains
fiberglass rods and continuous fiberglass rovings.
The C-Flex is applied perpendicularly
so that the strength of the C-Flex will directly withstand the expansion and contraction of the planks. The Sheathing is securely
fastened to the planking with bronze staples.
Chopped Strand Mat
– CSM is a relatively low strength (11,000 p.s.i. tensile) omnidirectional fiberglass material. It is not a woven fabric,
but rather a composite of randomly oriented strands of fiberglass. It is used in laminates to assist in bonding between layers
CSM is well suited to sheathing because it can be easily applied overhead.
Occasionally multiple layers of CSM are required, depending upon the size, design, use and condition
of the vessel.
Fairing Compound – To smooth the exterior surface,
a fairing compound composed of polyester resin, industrial talc and glass microspheres is used. This compound is easily applied
and dries to a hard, resistant surface. It is sanded to the required smoothness and then painted
The C-Flex Sheathing System may
be applied to large wooden boats that cannot be turned over.
– The hull is sandblasted and/or sanded (24 grit) to remove all paint. Any weak or rotten planks should be replaced,
holes should be patched and any necessary fairing work should be done to create a uniform surface.
Applying the Adhesive – The adhesive is a one-part adhesive, which is worked similar to a plaster.
It is applied with a notched trowel (1/4” teeth) held at a 45-60 degree angle. The adhesive has a four-hour working
time before it begins to cure.
Applying the C-Flex –
The C-Flex is applied directly over the uncured adhesive so that the adhesive is squeezed up into the C-Flex. The C-Flex is
held in place by small wooded battens that are stapled across the C-Flex using steel staples. These battens hold the rods
evenly in place.
The C-Flex is then permanently stapled into the hull with bronze staples.
These are applied 12 per sq.ft.
Saturating the C-Flex –
Once the adhesive is cured, the battens are removed and the C-Flex is saturated with general purpose laminating resin.
Finishing the Hull – The application of the CSM, fairing
compound and paint is similar to the method used on “one-off” boats. The amount of time required for this step
depends on the surface finish required.
General Notes on Application
Procedure – There are several minor variations on this system which are dependent upon the conditions under
which the boat will be sheathed. In general, fiberglass work should be done in a sheltered area. If this in not possible,
we have developed techniques for working in the open. Please consult with us at the time of your purchase so that you are
property informed of these details.
The technical advantages of the C-Flex Sheathing System are: 1) that it can be easily applied to boats without
turning them over, 2) the extremely high strength of C-Flex means that much less material and time is required, 3) the fiberglass
is mechanically fastened and chemically bonded to the wood to prevent delamination, 4) the chemical bond is an elastomeric
polyurethane which will expand and compress without breaking the bond, thus preventing delamination, and 5) the adhesive will
adhere to wet wood, treated wood and virtually every variety of wood used in boat planking.