J/70 Owner Guide
Page
© Copyright 2013, J Boats, Inc. All Rights Reserved
9
Getting to Know Your J/70
Hull, Deck & Structure
The engineering and construction of the J/70 Hull, Deck, Rudder, Keel and Structure meet the
requirements of ISO Standard 12215 1-‐5 titled Hull Construction & Scantlings for Category C. These are
International minimum standards required for all new boats.
Hull: The J/70 hull is built with E-‐glass and balsa core sandwich construction with white gelcoat finish
and VE resin in the outer layer for osmotic blister protection. Bi-‐axial and unidirectional glass fabrics are
used on both sides of the balsa core and are combined with local reinforcements in key highly loaded
areas including the hull centerline, keel trunk, transom, bow stem, bow sprit housing and hull flanges.
The hull is designed with an inward turning hull flange trimmed to match the finished deck edge allowing
for a significant overlap at the glued hull/deck joint. Interior hull surfaces in the cabin areas are finished
with a brushed on “air-‐dry” gelcoat finish.
Deck: Deck construction is E-‐glass and Core-‐cell foam sandwich construction with white gelcoat finish.
Hi density Airex Pxc core blocking is used in place of Core-‐cell in areas of deck hardware penetrations.
Additional E-‐glass reinforcements are specified for areas of deck hardware, mast step, rudder hardware,
jib furler, keel recess, toerails, as well as edges and corners as necessary. The deck is bonded to the hull
flange with Plexus MA 550, a proven, strong, watertight and lightweight method approved by ABS.
Interior deck surfaces in the cabin areas are finished with a brushed on “air-‐dry” gelcoat finish.
Interior Structure: J/70 interior structure includes several transverse bulkheads, a V-‐berth platform,
reinforced keel trunk and longitudinal hull support members. Each of these is built with e-‐glass, gelcoat
and in some cases foam core. The layout and construction are specifically engineered to best distribute
the sailing loads of the boat per ISO. All fiberglass internal members are glue bonded and/or tabbed with
glass tape directly to hull and deck surfaces. The mast compression post is anodized aluminum and
engineered to transfer mast compression loads to the hull. This post is fastened mechanically through
the deck and at the fiberglass base support. Two plastic access inspection ports are installed at the aft
bulkhead and on top of the aft end of the V-‐berth. It is advisable to inspect these areas periodically for
moisture or condensation build up and dry out prior to extended storage.
J70 Lifting Keel
The J/70 is equipped with a lifting keel that enables owners to easily ramp launch and store their boat on
a trailer without the need to rely on boat yards or yacht clubs. The keel system and the boat are designed
with stability to operate in open water and under sail ONLY with the keel in its fully lowered position
with keel safety plate properly secured in place.
Keel Construction
J/70 keel weighs 630 lbs. (285k) and is built with a complete molded fiberglass shell surrounding
internal structure/ballast composed of a fabricated 316SS spar and lifting bolt cast into a lead bulb.
Internals also include structure to support the leading edge and kelp cutter installation. Four wedges are
through-‐bolted at the head of the keel assembly to support and position the keel within the boat. Top of
the keel is finished with a keel lifting eye positioned inline with the keel CG.
