Fixing to fiberglass

[Palmtree]

Hi,

A number of lift-the-dot studs where the canopy fits to the hull are broken or missing so need to be replaced. Is the best way to fit them drill, light countersink and tap the screw thread into the fiberglass or some other way?

Ian

[Guest]

If there's easy access to the inside, I'd always use a small stainless bolt and locknut.

I say that because even under extreme loading, they'll never come loose.

The alternative, where access to the inside is difficult, is to use self tappers, as you thought. That can be very firm, providing the hole through the fibreglass is drilled to exactly the right diameter. If it's a fraction too big, the screw will easily lose it's grip, and if it's a fraction too small, the screw will shear off. Fibreglass is not compressable like wood, so it's almost like tapping metal.

If anyone ever does end up with a "sloppy" screwed fitting in fibreglass, I found the simplest solution was then a stainless pop rivet.

[diesel falcon]

I have this problem at the moment,instead of the poppers i intend to change them to the toggle type of fastening as in a gale the poppers keep springing off because of the movement in the wind, don,t know if i can do it myself if not it,ll have to be a canopy guy!!

If you fill the old hole with bridging fiberglass, the stuff with chopped strands in (from halfords!!) then redrill normaly works

[Antares_9]

Without some kind of backing self tappers have no place in GRP skin, even then there is no substitute for proper through bolts, again, with a backing to spread the load. If you are using self tappers with a backing then it is worth countersinking slightly to prevent gel coat cracks, the countersink has another advantage as the sealent has somewhere to sit instead of being sqeezed out.

[Palmtree]

Hi,

I try to avoid self tappers and prefer normal threads drilled and the thread cut into the base material with a tap. Putting a backing plate or some penny washers and a nut will spread the load however I think they will be hard to get to.

Thanks for the feedback

Ian

[Jim]

Hi Ian,

Are they all to be fitted to GRP? I replaced all of ours way back in 2004 and bought the replacements and screws from Sea Screw in Eastbourne. When Falcon built the boat, they had fitted a threaded version of "poppers" to the alumnium screen surrounds and fixed the others with stainless screws to the GRP. When I replaced the ones on the ally, I used pop rivets to fix the new fittings which have been fine.

Looks like you're going to be busy