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 TB 55-1900-201-45/1
rough surfaces glue better. This is not true. Water proof glues are poor fillers. Thus, the surface should be as smooth
as possible.
2-20. Wood Preservatives. Wood preservatives used for protection against decay fungi and marine borers either kill
the organism or pre- vent if from growing. For marine use the preservative must offer no toxic hazard to the crew, and
must be able to remain in the wood and do its work in the presence of moisture.
SECTION VII. Fiberglass Hulls
2-21. Hull Deficiencies.
a. Trouble areas in fiberglass hulls usually are found in wood- work, hull attachments, engine foundations and
keel (where the keel is wood and covered with reinforced fiberglass), shaft logs, cracks in the transom area, and cracks in
flare of the bow.
b. Reinforced fiberglass structures do not exhibit ductility or ability to take to permanent deformation as steel
does. Therefore, if a supporting structure deflects or deforms, stresses are introduced into the fiberglass structure which
will add to any stresses due to service loads. If any damage to the supporting structure is permitted to remain in stress,
the fiberglass will not revert to its normal shape. To prevent locked-in stresses when making repairs, all metal and/or
fiberglass mating surfaces must be smooth and fit closely. The fiberglass structure must never be sprung or "pulled in" to
meet the mating surface, or otherwise deformed.
c. Fastener or connection areas. Failures may occur in these areas due to improper design, such as insufficient
distance allowed between adjacent bolt holes, insufficient distance between the bolt hole and the edge of the laminate, or
insufficient bearing area under the bolt heads. Failure also may be caused by the applied loads exceeding design loads,
loose or missing fasteners, stressing the laminate at assembly, or allowing an excessive bolt hole clearance. The resul-
tant defects may appear as elongated bolt holes, fasteners pulled through the laminate, fastener heads sheared off,
cracks, fractures or delaminations.
d. Secondary bonded stiffeners. Separation or peeling action may occur in these areas due to inadequate sur-
face preparation, in- sufficient flange areas, poor adhesive or poor application. (Fasteners are commonly used at ends
and center of a stiffener to prevent peeling action.)
e. Areas around openings cut in a laminate. Such areas shall be inspected for cracks, fractures and delamina-
tions. These areas may have increased thickness incorporated and the edges either covered with a glass tape or a metal
channel to prevent such damage.
f. Other laminate areas. In addition to the critical areas previously described all areas shall be examined for pos-
sible laminate failures, especially at hard spots where localized stress
2-17
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