Mast bracket falling off my carbon mast...

Zonker

Super Anarchist
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Yeah but it's not a mast track - it's a little tiny carbon bracket with a few displays weighing a few kg. Few blobs of glue will work

 

George Dewey

Super Anarchist
2,071
118
Charleston, SC
I'll do one or the other thanks! For now I just need it to hold a few more days until I got her home. I have some orange Loctite (or some thread locker) and I'm hoping that will hold the tiny screws in until I can get somewhere with actual tools.

 

George Dewey

Super Anarchist
2,071
118
Charleston, SC
Yeah but it's not a mast track - it's a little tiny carbon bracket with a few displays weighing a few kg. Few blobs of glue will work
The glue option is probably best, but my concern is that I have plans to swap the bracket and instruments in the short to mid term future. I realize 4200 will come off but not easily. Helicoils seem to tap into the whatever they are out into, will they hold? Might something like rivnuts be a better option? And there is still that galvanic corrosion issue, so coat them with Teff Gel or maybe use an adhesive? 

 

George Dewey

Super Anarchist
2,071
118
Charleston, SC
Looking at rubber well nuts, they seem like they would hold well and can also be removed and replaced. If I were to go with something like that, how long do they need to be to grip well? I have no idea how thick the wall of my carbon fiber mast is. 

 

Zonker

Super Anarchist
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Thin carbon masts are not the best to drill and tap into, even with Helicoils. How big is your boat George?

 
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weightless

Super Anarchist
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583
Looking at rubber well nuts, they seem like they would hold well and can also be removed and replaced. If I were to go with something like that, how long do they need to be to grip well? I have no idea how thick the wall of my carbon fiber mast is. 
I think all the "blind" fasteners will need a bit more length than the wall thickness plus the mandrel head or nut or whatever gets pulled. So, I think you'll need to get some idea about the mast thickness. Here are some examples from McMaster:

image.png

 

Zonker

Super Anarchist
9,714
5,668
Canada
You could also use "Christmas tree" fasteners. Plastic, cheap and made to fasten auto body trim.

image.png

Not super strong so if a stray rope grabs the bracket it would might tear it off though. They work well with all sorts of thicknesses of thin panels.

These style are more secure. Again, all plastic.

image.png

 

George Dewey

Super Anarchist
2,071
118
Charleston, SC
Thin carbon masts are not the best to drill and tap into, even with Helicoils. How big is your boat George?
The boat is a J/111 so 36 feet.

For a non-structural bracket maybe this kinda thing?

https://en.wikipedia.org/wiki/Well_nut
I finally did this job today and it went better than I expected. I went to a Tru Value and got the smallest well nuts I could find, which were a little over 1/4 inch in diameter with 6/32 screws. They were about half an inch long, and I would have preferred longer in hindsight. I got brass screws and washers to go with them, hoping to avoid galvanic corrosion issues. I drilled the mast, making the smallest holes they would fit into, pushed them in and screwed the screws hand tight. I didn't use any thread locker because I think the force of the rubber will pull the screw tight. Also I think the rubber will prevent the holes from leaking. I also checked a bit later and the screws were loose, so I tightened them again. I'm hoping this is just the rubber setting. 

Now if i want to remove or switch the bracket later, it should be easy enough to remove. I'm a little concerned that I should have used longer well nute, but I was careful to make the hole just big enough to squeeze the thing in, so it will probably stay put. I guess I'll see in time.

Thanks for the comments everyone!

 

George Dewey

Super Anarchist
2,071
118
Charleston, SC
You could also use "Christmas tree" fasteners. Plastic, cheap and made to fasten auto body trim.

View attachment 453883

Not super strong so if a stray rope grabs the bracket it would might tear it off though. They work well with all sorts of thicknesses of thin panels.

These style are more secure. Again, all plastic.

View attachment 453884
The hardware store had these too, but I think the well nuts will hold better.

 

overdraft

Anarchist
what was the nature of the well nut failure? well nuts are used extensively on motorcycles which jiggle around a helluva lot more than boats. I thought it was going to be the perfect solution because of the insulating factor... cf and ss are not friends... 

 

George Dewey

Super Anarchist
2,071
118
Charleston, SC
what was the nature of the well nut failure? well nuts are used extensively on motorcycles which jiggle around a helluva lot more than boats. I thought it was going to be the perfect solution because of the insulating factor... cf and ss are not friends... 
The well nuts have been pulling out of the holes. They fit in snugly at first, but eventually pull out. I think the nuts that you tighten against (that squish the rubber) are breaking or falling off or something. I have tried several different sources of well nuts and they have all failed. I have noticed that sometimes the crew falls against the bracket, or else leans on it temporarily, or whatever in the heat of battle. 

Tomorrow I'll measure the mounting hole diameter to see what size heli-coils to get. Even then I'm not sure this will work; the mast wall is thin, and I am having trouble sourcing 316 stainless coils. I may need to pull the mast and install some kind of backing plate. I need to replace the VHF feedline anyhow. 

 
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Overbored

Anarchist
711
59
So. Cal
 never seen a 316 helical and have been looking for 40 years. I have used Nitronic 60 and Titanium on a few applications. Iif it is thin carbon then a hell coil will not work well. you could bond in a thread insert like a Rosan used for wood aircraft. if it were me I would make brackets out of carbon and bond them on where the existing ones are over the holes

 




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