Bimini Question

[hhcribbs]

Hello again, thanks for all the previous help.

We just setup the bimini on our sailboat. There was a bit of a blow this past Friday night and upon arrival Saturday morning we noticed that the port bimini frame was collapsed in the front. Upon inspection the mounting bracket was pulled loose from the deck. Here's the interesting part...the mounting bracket (and we have a total of four) is only secured to the deck with a 1" stainless steel screw (looks like a wood screw). Is this appropriate for a large bimini? Seems it should be through bolted with a backing plate. There are no exit holes in the stern lazarette or stern berth beneath this hardware. Just checking to see what is typically recommended (besides remembering to fold up the bimini when leaving the boat).

Thanks and have a great week!

 

[Mike B1026]

I would guess most are attached the same way because of the difficult access underneath on most boats. Of course bolted would be better but some holes and access panels might be needed for that.

The other issue may have been that the holes were not properly sized for the screws that were used.

 

[larryw]

It's difficult to screw a screw into fibreglass because of its structure and the hold is usually not that secure compared to wood or metal. Those types of screws pull out all the time, it's the nature of the beast. Try filling the hole with epoxy and turning the screw back into it. Keep stress off it until the 'poxy cures. There's other things. Subscribe to Good Old Boat or Woodenboat mag, they're full of fixes for things.

 

[jibes138]

Additional option for strength

I installed my own bimini and through bolted the mounts. If you do not have access to through bolt then I strongly recommend that you bond an insert into the fiberglass to take the loads of the threads and to spread the stress over a much larger area. This can be a prethreaded insert or you can bond in an insert and then drill and tap into it for a machine screw. Wood or self tapping screws should be banned from boatbuilding. Fiberglass is not an appropriate material to put threads into and expect to hold anything that is stressed. Think about what it is, fiber reinforced PLASTIC. The fiber reinforcement is to give it outstanding tensile strength, this resists the bending of the boat when getting smashed by 50 foot breaking waves, but the point contact stress of a wood screw trying to shear out the material is not what it is designed to resist.
If you go to McMaster Carr or similar distributor and look up screw thread inserts you will find a variety available, it would be best to drill out a large area, insert the insert, then layup over the top of it.