Bonded fastenings

[Jack Heinlen]

Situation: Stemhead fastening, bronze machine screw, sheared off, self-tapping stainless screwed in next to, also sheared off, fiberglass stem. Away from vertical in direction of the hole.

Plan: Dig around with a small drill till I can get the bronze and stainless out. Drill out maybe a 3/8 hole, an inch and a half deep. Mix up some googe and structural filler till as thick as "natural" peanut butter. Work into hole well then cover with tape. Drill and tap for new machine screw.

Thoughts, problems?

[Ken Hutchins]

I would probably tap it to something like 7/16-14 to give mechanical strength to the googe.

[Canoeyawl]

If this “stemhead fastening” is holding the headstay fitting, I would consider going all the way through the stem using a bolt or machine screw w/nut and washer. Then we are not relying on some structural goo to hold up the mast...

[ssor]

The stem head fitting was fastened with screws into fiberglass? :eek: I wouldn't consider anything less than through bolts at least as large as the stay.

[Jack Heinlen]

The stem head fitting was fastened with screws into fiberglass? I'm not much up on the engineering but the way this was constructed, near as I can figure: The stem is a solid glass laminate, hefty as hell, and the screws into the laminate are 3/16 by inch machine screws, tapped in.

I believe this is very acceptable practice, and is likely just fine; tough as hell. 19 foot boat BTW.

What I suspect is that the person putting this screw in overtightened it and broke it. The boat has likely been sailed this way for twenty years. But I'd like to make it right.

I would through bolt it, but there is no access.

[ssor]

There is another approach that you could take, Drill the hole out to allow you to install a threaded bronze bushing or plug and drill and tap that plug for your new screws. If you choose to fill the hole, use milled glass filler not micro balloons. The stresses on a 19 foot boat are more easily handled than on a larger cruising boat.