Attaching a Scoop Strainer

jverl · Post by **jverl** » Tue Apr 24, 2007 3:32 pm

I want to attach a bronze scoop strainer on the outside of my raw-water thruhull. I guess there are three ways to do it: 1) screw into the fiberglass with small SS sheetmetal screws. 2) Screw thru the fiberglass into the wood thruhull backing board with bronze wood screws and 3) thrubolt the strainer into the wood thruhull backing board with bronze machine screws and nuts. I assume I will have to caulk the strainer to prevent water ingress thru the screws as it will be underwater. Any opinions?
Thanks,
John

Post by **Tim** » Tue Apr 24, 2007 4:06 pm

There's really no need to throughbolt something like an external strainer. I would suggest drilling and tapping for machine screws that you can thread into the holes, rather than sheetmetal screws or wood screws. Neither sheetmetal nor wood screws have a very long-term bite in fiberglass.

You'll need sealant regardless of the method you use to secure it, of course.

jverl · Post by **jverl** » Wed Apr 25, 2007 7:28 am

Thanks for the prompt reply, Tim. Is tapping into fiberglass (about 7/16") strong enough or is my method 2 where I drill thru the fiberglass and screw into the wood backing plate better?

Post by **Tim** » Wed Apr 25, 2007 7:41 am

I think a 7/16" thick hull is plenty to allow for adequately deep tapped holes for something like a 3/8" long machine screw (bronze, to match the strainer). The strainer probably takes a #4 or maybe a #6 fastener size. It doesn't take much to hold on one of those little strainers. Plus, the sealant will also add some adhesive qualities.

jverl · Post by **jverl** » Wed Apr 25, 2007 7:48 am

Thanks again, Tim. I'll go the tapping route.