Hi guys,
Summary of my plastic anchor test:
Plastic masonry anchors can be installed into epoxy plugs to accept wood
screws, and they hold the screw very well.
Screws driven into pilot holes in epoxy plugs (Dennis C recommendation) are
much stronger. The plastic anchors add great shear strength and cushion
impacts but can slip out of the smooth hole under 15# to 20# of tensil force.
Now since I did this to find a way to attach my sea hood to the cabin top,
plastic anchors may offer a good method as it allows the sea hood to expand
separately from the cabin structure plus they cushion the impact of crew
walking on the hood. My plastic anchors are meant for #10 screws, so I'll have
to try #10s instead of #8s.
Test method:
I made my test panel from a small scrap piece of balsa cored deck and drilled
five 3/4" diameter holes and one 1/2" hole into it, primed those with neat
epoxy 105/206 and then added 404 filler to four holes and THIXO flexible epoxy
to the last two holes. After they cured I sanded the epoxy plugs flush to the
surface and drilled 7/32" and 1/8" pilot holes into plugs 1 and 2. Plugs 3 and
4 got drilled for plastic anchors. Plug 5 is Thixo and got drilled for plastic
anchor while Plug 6, a 1/2" Thixo plug got a small pilot hole, 7/32". I drove
in the #8 wood screws using a drill driver with the clutch set very low at 3.
I left the heads high enough to get a blue pry bar under each one to test for
holding strength.
Correctly sizing the pilot hole for the chosen screw is critical. I tried
three size drills based on internet advice and found they all work but 1/8"
seemed best fit for my brand new #8 wood screws.
https://drive.google.com/file/d/19kVrTvC49DPhH05pj9JHUmz2iW_uqsEg/view?usp=sharing
Chuck Scheaffer Resolute 1989 C&C 34R, Pasadena Md
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