[Dave_E]

Hi All,

Never thought much about this because it's never been something I needed to do. I want to put a pretty good load bearing piece of hardware onto a 1/4 inch thick fiberglass structure which has no back side access. Is there anything besides screws that we use in the marine community for such applications? Thank.

Dave

 

[Sailormon6]

Could you cut an access hole in the structure, so you could use nuts and bolts and washers to mount the hardware, and then, when the job is done, close the hole by installing a Beckson plate?

 

[knuterikt]

Hi All,

Never thought much about this because it's never been something I needed to do. I want to put a pretty good load bearing piece of hardware onto a 1/4 inch thick fiberglass structure which has no back side access. Is there anything besides screws that we use in the marine community for such applications? Thank.

Dave

If you can give us some more details it would be easier to give good advice.
Location, type of hardware?

 

[davidh52]

stainless toggle bolt.

 

[mdidomenico]

Hi All,

Never thought much about this because it's never been something I needed to do. I want to put a pretty good load bearing piece of hardware onto a 1/4 inch thick fiberglass structure which has no back side access. Is there anything besides screws that we use in the marine community for such applications? Thank.

Dave

i have a similar project coming up as well. mine isn't overly load bearing, so i was going to use these

McMaster-Carr

 

[rugosa]

Hi All,

Never thought much about this because it's never been something I needed to do. I want to put a pretty good load bearing piece of hardware onto a 1/4 inch thick fiberglass structure which has no back side access. Is there anything besides screws that we use in the marine community for such applications? Thank.

Dave

I have a policy when it comes to fastening, in this order -
weld, through bolt, drill and tap machine screw, screw, rivet - all in stainless. I haven't used a rivet since the mid 70's when I really didn't know any better. Velcro and space age adhesives have their place, but there is a pecking order there too.

 

[VallelyJ]

Knowing the kind of structure and load you're talking about would help. And the nature of the strain on the fasteners--shear, compression, tension?

 

[aloof]

Pop rivets if the load is between .5 and 1.5 "pretty goods." If more you must cut an access hole nearby and slide in a tapped backing plate. Using toggle bolts just defers the headache originally caused by the amateurs who designed and built a boat without access to both sides of every structure.

 

[hpeer]

There are also rivit nuts.

Rivet Nuts | Threaded Inserts - Rivnuts For Sale

 

[zz4gta]

What's the load? And how is it applied? What kind of safety factor are you looking for?

 

[RichH]

If the fastening is of 'critical' strength need, cut a small 'working hole', install with backing plates, etc. then repair the hole to perfection with fiberglass, epoxy filled silica, and new gelcoat + sprayed on finish gelcoat.

This is how its done with new boats that have blind hollow bulwarks, etc. For repairs, etc. this way you will know the strength/thickness of material your 'penetrating'.
Kep-nuts, butterfly toggles, and other 'expanding' fasteners etc. etc. can 'loosen' or easily pull out of fiberglass if they provide 'point' contact. If this is a strength fastening, you really should consider backing plates, etc. and there's only one way to insert such in a 'blind' panel. For backing plates shoved into quite small 'working holes', I prefer to use drilled and tapped/threaded holes in barstock. To position/align, I 'tape-on- a wire coathanger to the barstock, and simply pull the wire loose when done. This is kind of like building a ship inside of a bottle .. a 'strong' ship, inside that bottle.

For the gelcoat repair, consider: "Professional Gelcoat Repairs Without a Mess" - John Gabriel (DVD) Boatrepairvideos.com | Fiberglass and Gel coat Repair To 5 Star Quality

 

[Dave_E]

What's the load? And how is it applied? What kind of safety factor are you looking for?

I want to install a jack line. The "load" would be me if I ever went overboard. There is an area just fwd of the traveler that would be perfect, but as mentioned it's hollow.

 

[knuterikt]

I want to install a jack line. The "load" would be me if I ever went overboard. There is an area just fwd of the traveler that would be perfect, but as mentioned it's hollow.

Probably not hollow, how do you think the traveller was installed?
Can't you drop the headlining to get access from below.
That's what we had to do when we replaced our traveller.

 

[Stumble]

This demands a backing plate. You cannot use blind fasteners for something like this. Life safety gear requires a MINIMUM of a 10:1 safety margin which for a 200lb man would require 2,000lbs static load. Since jack lines deal with shock loads the forces could be substantially higher. You need a big backing plate, and plenty of bonding surface to do this correctly.

Since the traveler also has a backing plate there must be some way of accessing the area, even if it isn't obvious.

 

[miatapaul]

I want to install a jack line. The "load" would be me if I ever went overboard. There is an area just fwd of the traveler that would be perfect, but as mentioned it's hollow.

Well figure that they say to use at least 6000 # test webbing, so it should be a strong fitting with a backing plate. I think you would end up with leaking if there is not sufficient backing plate anyway. So best practice (and we are talking about your life here so best practice should be adhered to) is going to be cut a hole in the headliner, and put in a backing plate and bolt. You should be able to find a plug to cover the hole. I would want to be able to access it so I would not fiberglass over it. Personally think you might want to find the plug first, that way you don't end up with a hole bigger than you can find a plastic plug for.