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Depth of aluminum sheet or plate below deck of Catalina 30

Tpoo

.
Jun 15, 2020
5
Catalina 30 MKII Tall Rig Kemah
Hi all,

I'm planning to install a double clutch on the port side of my 1989 Cat 30 MkII tall rig. It will be mounted on the same raised platform where the clutch for the main halyard and the clam cleat are mounted on the starboard side (next to the hatch top). I understand that I can expect to encounter an aluminum block or plate when I drill the mounting holes. I'll need to use a tap to cut threads in this plate so that clutch can be secured with machine screws. I believe this is the reason Catalina put the plate there to begin with...helping to avoid having to drill holes all the way through the cabin top.

Anyway, simple question: does anyone know the depth of this aluminum plate below the gel coat/fiberglass? Just want to know what to expect when I start drilling and also the length of the screws I'll need for the job.

Still learning the ropes,

Tpoo
 
Oct 22, 2014
13,136
CAL 35 Cruiser moored EVERETT WA
does anyone know the depth of this aluminum plate below the gel coat/fiberglass?
When faced with such a dilemma I usually with draw a screw from something already there and look in the hole. Measure the screw. Poke a pick tool into the hole like a dentist and use the pick tool to help judge the depth.
 

Tsuru

.
Sep 4, 2019
2
Catalina Catalina 28 Hood River
When faced with such a dilemma I usually with draw a screw from something already there and look in the hole. Measure the screw. Poke a pick tool into the hole like a dentist and use the pick tool to help judge the depth.
I did this exact same job on our Catalina 28 and used the method as suggested above. Although, I ended up marking one of the existing bolts with a sharpie to determine the depth.
 

Tpoo

.
Jun 15, 2020
5
Catalina 30 MKII Tall Rig Kemah
Thanks Tsuru...great suggestion and that is what I plan to do.
 

Ward H

.
Nov 7, 2011
2,720
Catalina 30 Mk II Barnegat, NJ
In the spring I replaced the double clutch with a triple clutch on my C30.
I’m thinking the plate was about 1/2” below the surface of gel coat and I used 1 1/4 or 1 1/2 inch 1/4-20 machine screws.
Probably worth a trip to the boat to pull a bolt from the existing clutch to measure.
Nice upgrade.
 
Jun 2, 2004
3
Catalina 30 Mk II Charlevoix, MI
After determining your depth, and diameter, thread, etc., obtain the proper tap for threading the hole, then cut the tap tip off to a shorter length so it does not bottom out into the fiberglass below the 1/4 " aluminum plate.