Date: Thu, 03 Feb 2000 16:28:01 -0500
From: Tech Support
Subject: Re: Technical Question
Ken.
1. Filling the cavity without air entrapment. Work from the outside
of the boat. Drill a 3/16 inch hole at an angle downward so it
intersects the 1 inch cavity near the top. Don't worry about the
looks of the hole--it will be covered by the chainplate. The 3/16 inch
hole is used to insert a syringe into the cavity and inject epoxy into
it. Because the 3/16 hole is drilled at the top of the cavity, it
will provide a vent for the trapped air. Inject epoxy until the
syringe is forced out of the hole by the hydraulic action of the
epoxy.
The epoxy should be filled with 404 High Density Filler and you should
use the 206 Slow Hardener. You do not want the epoxy to cure too
rapidly. Thicken the mixture so it will flow like ketchup.
2. Maintaining the hole alignment. Insert a waxed 3/8 inch metal
dowel through the 13/32 holes. Seal around the dowel so epoxy will
not flow around it. Fill the cavity with thickened epoxy as described
above. Allow the epoxy to cure then remove the dowel.
To complete the project, slightly ream the 3/8 hole. Coat the
chainplate bolt with epoxy as you install it. This coating will
provide an absolute tight fit. If the bolt cannot move under load,
the hole will not elongate again. If you really want to do an
overkill job, chamfer the outside of the hull laminate with a
countersink. Fill the countersunk area with epoxy thickened with
milled carbon fiber. The largest load on the bolt is where it exits
the hull. With the carbon fiber reinforcement in this area, the load
from the bolt trying to shear will be distributed more effectively
into the hull skin.
I hope this gives you some ideas that will help with the project.
Sincerely,
Gougeon Brothers, Inc.
Brian Knight
Technical Service
Gougeon Brothers, Inc.
100 Patterson Ave., PO Box 908
Bay City, MI 48707-0908 U.S.A.
tel: 517-684-7286
fax: 517-684-1287
URL: www.gougeon.com or www.westsystem.com
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The submitted values are:
Question: We are in the process of repairing chainplate attachments on
a 1978 FRP sailboat. The bolts pass through (outside to inside) 1/2
inch laminate, 3/4 inch plywood core material, and 1/4 inch
laminate. Over time and poor bedding, the holes have enlarged and
water intrusion has caused some rot in the wood core. I've removed the
damaged coring using a drill and a bent-nail (actually an old allen
wrench cut down to about 1/4"). Looking from the side, you would see a
13/32" hole 1/2" deep, expanding to an almost 1" hole 3/4" deep,
changing to a 13/32" hole 1/4" deep (see cheezy diagram).
( ______ \
(------\ \--\ S/S chainplate
\--3/8" S/S bolt---\\\-
(------\_____\--\
( LAM CORE \
LAM
It is now time to fill the hole with thickened epoxy, then redrill to
the proper size: 3/8" x 1.5" deep
My questions are:
How can I fill a horizontal hole so that there are no voids? Would it
be easier/ better/ safer/ to remove that interior 1/4 of laminate,
thus exposing the enlarged hole in the wood core material. If so,
should I build up a new laminate on the interior, or simply fill with
thickened epoxy. Access on the interior side is not great.
Any hints on drilling a 3/8" hole that matches a pre-existing
chainplate would be greatly appreciated. Trying to line up
the new drill hole with the chainplate seems to be almost impossible
given just a power drill.
Regards,
Ken Mayer