|Topic Review (Newest First)|
|08-09-2010 05:27 AM|
Sorry if this is a hijack, but I have two questions about rivet nuts.
First, does anyone make them in stainless? I was just looking all over and can only find them in steel and one type in rubber.
Second, for them to work properly, does the surface of the hardware being mounted need to be in contact with the outter surface of the rivnut? I am thinking of mounting a Harkin cam cleat with a riser, for example. The riser is hollow, meaning the bolts come through the cleat and down through the riser, into the surface being mounted to. There would be no pressure on the outter surface of the rivnut.
I realize toggles might be a better choice here, since they would be pulled snugly against the back of the mounting surface, but I can't find togles in 10-24, which is the size the bolts must be to mount the Harkin cam cleat. :-(
OOPS - I found the stainless ones. Way too early for me to be posting...
|08-08-2010 09:59 PM|
However, the togglers will spread the load out over a greater area of the cabintop or deck and IMHO are better suited for higher load applications than Rivnuts.
Originally Posted by GaryHLucas View Post
|08-08-2010 09:37 PM|
You can get those togglers in stainless, I was surprised to see them in West Marine! However my choice would be to use a RivNut. A Rivnut works like a pop rivet. It has a head on it and internal threads. You use a threaded mandrel with an inexpensive tool that you tighten up to expand the back end of the rivnut. Then you unthread the mandrel and put your bolt it. Rivnuts work very well in fiberglass. If it ever gets damaged you use the same size drill to drill through it, and just install a new one. McMaster Carr among others sell them.
For lighter loads than a cleat I also recommend SwellNuts. Similar to a RivNut but made from rubber with a brass insert. They seal completely and won't crack the fiberglass, tolerate lots of vibration, and can be replaced at any time. Great for fastening interior hardware to fiberglass liners inside the boat, especially if foam filled.
Gary H. Lucas
|08-08-2010 09:35 PM|
|PaulDolan||A good secure way of handling the cleat is to remove the existing cleat, create a new base out of fiberglass reenforced plywood and glass the whole assembly in place. No worries about the ability to take a strain.|
|08-08-2010 09:18 PM|
|sailingdog||Using something like that will at least spread the load out a bit more than the screws would, and not be dependent on just the strength of the threads biting into brittle fiberglass.|
|08-08-2010 08:24 PM|
|BlueWaterMD||Thanks for the advice everyone. Never thought about toggle bolts before - that may do the trick.|
|08-08-2010 03:41 PM|
Why not use something like a toggle bolt to fasten the cleat. It isn't ideal, but it is a hell of a lot better than relying on screws in relatively brittle fiberglass. I'm thinking of something like this:
Which would be relatively easy to install, and if you wanted more security with it, you could always inject thickened epoxy around it to secure it to the hull and prevent any water intrusion.
It is essentially retrofitting a tapped metal plate into the hull as JRP mentioned builders sometimes do.
|08-08-2010 12:55 PM|
What about getting a 1/2" drill bit, and drilling completly through that section of the cap rail/deck edge? Then, using good old ziplock baggies (epoxy doesn't stick to them) you could 'plug' each end and fill it with epoxy. Let the epoxy dry, then you could drill/tap it for screws. The better plan would be to throughbolt the cleat, but there again, you could just drill right through that epoxy plug with no mess and no concern about crushing the foam.
Of course, using a 3/4" bit or larger is always good.. it's rather dependent on what amount of space is available in your work area.
Hopefully I did at least a halfway decent job of explaining that whole thing.. it's really quite simple.
|08-08-2010 11:15 AM|
No need to apologize for liking stinkpots. They have their place -- especially the fishing variety.
Sorry, but I don't like the idea of re-attaching that cleat with screws into the fiberglass. Despite how you expect to use it, it will only be a matter of time before it gets a good yank and tears out again -- maybe making things worse than they are now.
Some builders do use screws for attaching deck hardware, but they normally will have a backing plate with tapped threads that the screws set into, rather than relying on grabbing into the fiberglass (which doesn't really work well).
There has got to be some way to minimize the invasive procedure of getting access to the back side of that cleat. Or, could the cleat be re-mounted in a somewhat different location, where access is better? Whatever you end up doing, be sure to add a backing plate.
Hopefully MaineSail or another savvy maintenance guru will come along and offer some better suggestions. Good luck!
|08-08-2010 10:49 AM|
Lots of options. Hard to say for sure but I would probably try to fill inject some thickened epoxy in the holes trying to get a blob under the deck. Then put in the screws and allow to harden. Use microfibers to thicken the epoxy. You might need to open the holes a bit and use a wire to remove some of the foam under to create a cavity for the epoxy. You probably wouldn't be able to ever remove it again however. Cleats should have backing plates but hard to say whether a 17 foot power boat was built with them.
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