Best fasteners in a mast -- Titanium?

[sailingharry]

Well, I was all set. All new machine screws, same size/type, installed with the goosneck raised 3/4 so the new holes are split between the old ones. Simple plan -- and drilling/tapping aluminum is dead easy.


Unfortunately, I made a tactical error. The mast was built by Offshore Spars, who are still in business, and have been very responsive in the past. I reached out and asked them. They responded with a phone call! They ran the question through their engineering department. Great support! BUT!


They want me to drill out the existing stainless remains in the aluminum mast (ugh!) and insert helicoils. Drilling the remains will be a challenge (but I can possibly use the holes in the gooseneck to keep them on center). I'm not fond of helcoils, but they may well be as strong/stronger than the original.


They caution against my plan, as they worry about "changing geometry" (huh, it's 3/4" in the rig of a 43' boat!). They also worry about additional perforations in the mast.


Their response is great customer service, but I do have one small reservation (beyond the challenges of doing what they say). He mentioned that they haven't built an aluminum mast in a decade -- they are all carbon fiber now. Makes me wonder how familiar they are now with a repair to aluminum.


I'll refocus on their suggested repair. But I won't drill a hole for at least another day, so I hope maybe someone will give me some brilliant advise....


Harry

[thinwater]

I think the odds of drilling out that many fasteners in aluminum, free hand without a press, without the drill wandering off-center and ruining one hole completely, at approximately zero. I'm also not clear on how new holes are so much worse than larger (helicoil) holes.



The geometry thing seems like a red herring. Either up or down could be better. I might opt for lower if there is no conflict (having the gooseneck higher than the the clew is generally bad).



Go with your original plan, IMO. I like helicoils just fine, but I doubt it can be done.


The problem with Rivnuts IMO, is that they are not flush. That changes how the force bears. I have used them.

[sailingharry]

Thin,


I agree with you 100% on the challenge of drilling stainless out of aluminum without making a terrible mess. It's been my primary reason for resisting the helicoil solution. But color me amazed. Beyond amazed.


I have a Harbor Freight tool for woodworking, designed to drill a hole neatly in wood in the center of hinges. It is a spring loaded "nose" with a desired drill in the center. Despite being a HF tool, the drill was remarkably sharp in stainless.


I re-mounted the gooseneck with the 6 screws that pulled out. They tightened up snug, so not completely stripped, and gave me a very solid alignment tool. I then used the hinge tool to align, support, and drill a hole. The bit was about 1/8". The tool did a remarkable job of making my hole centered. I then drilled with a 3/16 (just undersized for a 1/4-20 tap drill). Of 6 holes, 3 were centered enough that the remains popped out while drilling. The remaining were very close and I was able to break off the remains with a center punch. All holes are "good enough" that a 1/4-20 screw cleanly threads in and is fairly snug. I think the holes are sufficient to align a helicoil. I'll be hopefully using the helicoil drill through the gooseneck, further aligning the holes.


Frankly, I'm beyond amazed at how well it went. At this point, I've made no further damage, and can re-mount 3/4" further up. But given the fact that I can currently mount it "securely" with original fasteners in original holes, the helicoil answer has gained a huge step up in the analysis. Among other things, a helicoil should make future repairs (I hope not!) more possible.

[Bowdrie]

Originally Posted by sailingharry

I have a Harbor Freight tool for woodworking, designed to drill a hole neatly in wood in the center of hinges. It is a spring loaded "nose" with a desired drill in the center. Despite being a HF tool, the drill was remarkably sharp in stainless.

Bravo.
That's called a "Vix" bit.
Many companies make them, the originals come from the "S.E. Vick Co."
Everybody should have a set, they're the cat's meow.

[MWGDVC]

You probably should wet install the helical inserts using zinc chromate primer to isolate the dis-similar metals.
Helical inserts are available in locking or free running, as well as tanged or tangless.
Tangless means you wouldn't have stray bits of stainless steel accumulating in the bottom of your mast, if access is limited/impossible while your mast is up.

[thinwater]

Originally Posted by sailingharry

Thin,


I agree with you 100% on the challenge of drilling stainless out of aluminum without making a terrible mess. It's been my primary reason for resisting the helicoil solution. But color me amazed. Beyond amazed.


I have a Harbor Freight tool for woodworking, designed to drill a hole neatly in wood in the center of hinges. It is a spring loaded "nose" with a desired drill in the center. Despite being a HF tool, the drill was remarkably sharp in stainless.


I re-mounted the gooseneck with the 6 screws that pulled out. They tightened up snug, so not completely stripped, and gave me a very solid alignment tool. I then used the hinge tool to align, support, and drill a hole. The bit was about 1/8". The tool did a remarkable job of making my hole centered. I then drilled with a 3/16 (just undersized for a 1/4-20 tap drill). Of 6 holes, 3 were centered enough that the remains popped out while drilling. The remaining were very close and I was able to break off the remains with a center punch. All holes are "good enough" that a 1/4-20 screw cleanly threads in and is fairly snug. I think the holes are sufficient to align a helicoil. I'll be hopefully using the helicoil drill through the gooseneck, further aligning the holes.


Frankly, I'm beyond amazed at how well it went. At this point, I've made no further damage, and can re-mount 3/4" further up. But given the fact that I can currently mount it "securely" with original fasteners in original holes, the helicoil answer has gained a huge step up in the analysis. Among other things, a helicoil should make future repairs (I hope not!) more possible.

Good tip! I didn't think of that possibility.

[sailingharry]

Originally Posted by MWGDVC

You probably should wet install the helical inserts using zinc chromate primer

Now there's an old guy! I do have zinc chromate primer....but try and buy it today. Prices start at around $200/qt. You can buy 10ml bottles for an affordable price. EBay has quite a selection of new-old-stock. Unfortunately, like TSP, most products that have the word in the label contain none of it in the can....

[Talbot]

I have read all the opinions here and i am not aligned with many of the views expressed. I really dislike SS screws into aluminium - great initially and the the corrosion sets in (despite whatever you add to the mix, and you have a very thin aluminium mast trying to retain a small screw thread. I would really distrust helicoils for the same reason. Riv nuts do at least have a much better grip on the mast, but most types dont allow the fitting to make a very close attachment (unless you dent in the attachment point before adding the riv nut - not a very good idea).
Personally I would have insisted on monel rivets. No problems with corrosion, very strong, and neat.

[barnakiel]

In my experience monel is good material for in-mast fasteners.


The surface needs to be prepared very well - preferably by anodizing.


I would also imagine welding is an option too. The weld can be anodized afterwards too.



b.

[vpbarkley]

Use Rivnuts.

[Cheechako]

Originally Posted by sailingharry

So yesterday, I broke off my gooseneck. No drama, didn't even know it until the main came down. The rigid vang mostly supported the boom.


It seems of 12 5/16 screws holding it in place, about 7 broke off and the remainder pulled out. The broken ones won't move with a punch, and drilling them out will be challenging with limited chance of success. The pulled out ones have suspect threads. My intent is to raise it 3/4"and redrill.


I have an opportunity to consider attachment solutions. The original stainless lasted 26 years and at least 25,000 nm, so it's a good first solution. A friend suggests structural aluminum rivets, but I'm not convinced. And then I thought of titanium screws, available for about $4 each (see https://maps.app.goo.gl/G6ztYV4iWJsqmDoM7 ) -- not all that expensive if I get an upgrade for my money.



Any thoughts about titanium in this application? Any thoughts about any other alternative?

I'm not sure Ti will solve the aluminum corrosion issue. It may corrode and seize up as it's the aluminum that's the issue as far as seizing goes. Eventually they can pull out from disintegrated threads again. But the Ti portion would stay good itself I suppose as it doesn't suffer from crack crevice corrosion like SS.
I'd probably go with SS or monel rivets, or either in screws with plenty of Tuf Gel or Lanolin on the threads. But if Ti is reasonably priced... maybe.

If your gooseneck portion that attaches to the mast is aluminum just have it welded on.

[P3sailor]

As stormalong mentioned "rivnuts" should work very well, particularly if the wall thickness isn't enough to tap. If riveting is on your mind, I would consider something called a "Hi-Lok" they're used in the aviation industry, they're a close tolerance fastener but very stout and when installed properly, fantastic fastener.

[nmccubbin]

Agreed on sealing with 5200, or perhaps some more flexible guk
Instead of masking tape, we bolt the item in place then Vaseline all around the places the guk squeezes out
Slice with a knife when dry and cleanup is easy
No guk working under tape

[JonJG]

Originally Posted by hlev00

My us spar cast aluminum goose neck is riveted with either Stainless or Monel rivets to the aluminum mast. Use tef-gel. Don’t use aluminum rivets.

I agree- definitely not aluminium - insufficient shear strength. Monel rivets is the way to go. Just get a large leverage pop rivet gun.

[P3sailor]

I stated previously that Hi-Loks would be a good fastener but to install them you'd need access to the interior side of the structure, so they most likely wouldn't work out for the operator. So a person may want to try Cherry or Cherry
Lock rivets instead.