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Old 11-10-2018, 19:24   #31
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Re: Filling Old Rivet Holes

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Originally Posted by RaymondR View Post
I have repaired them using an aluminium rod which I used a thread die to put a thread on, then tap the hole the same size thread. Screw enough threaded rod into the hole to reach right through and cut the rod off with about 1 mm projecting then peen it until it swells tight in the hole and file it back flush. If you get it right and polish the scratches out the repair can be almost invisible.
I like this. Except you can buy aluminum screws or all-thread, rather than threading a rod.
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Old 12-10-2018, 03:30   #32
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Re: Filling Old Rivet Holes

I would go with aluminium closed end rivets. Albany fasteners
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Old 12-10-2018, 05:04   #33
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Re: Filling Old Rivet Holes

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Iím no saying you have to, but itís not a bad idea.
Like I said I donít think the mast actually carries much of the load in a mast with wire rigging, the wire does.
However there are of course internal chamfering tools. Here is a picture of one, stick it through the hole and the cutting edge sticks out, chamfer, retract the cutter and go to the next hole.
Attachment 178828

Drilling a hole and then running a reamer through it to remove any tooling marks (stress risers) and the deburring is just good practice.
Anyone wondering exactly what a stress riser is, look at a candy bar wrapper, those cut edges that concentrate the force when you open it and cause the paper to tear, those are stress risers.
How small of a hole can you do with these? I agree that stress risers can develop from round holes as I have seen this with cracks radiating out from fastener holes in the internal sleeve in the highly loaded gooseneck area of an old one tonner. Welding was not practical so we repaired it with composites.


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Old 12-10-2018, 07:05   #34
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Re: Filling Old Rivet Holes

In South Africa we have two products Prately steel epoxy and Prately steel putty which would fill a small rivet hole and will look like aluminuim. If one can get it to hold and cure it is exceptionally strong.
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Old 12-10-2018, 07:28   #35
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Re: Filling Old Rivet Holes

Blind aluminum rivets, leave them as holes, or JB Weld should do it. It's cosmetic. I wouldnt grind the holes or anything if filling with JB Weld or something similar, while it may adhere better you are just causing damage.
You could tap the holes and put in aluminum headless set screws, (if you can find them!) but they would still have the hex indent. Aluminum threaded rod, with loktite? Cut off and grind flush?
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Old 12-10-2018, 07:44   #36
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Re: Filling Old Rivet Holes

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How small of a hole can you do with these? I agree that stress risers can develop from round holes as I have seen this with cracks radiating out from fastener holes in the internal sleeve in the highly loaded gooseneck area of an old one tonner. Welding was not practical so we repaired it with composites.





Steve.


I donít know, pretty small, Iíve seen #10 ones, but in many itís two pieces of cutting bits, that look like triangles.

However I wouldnít bother on a mast, just a simple de-burr that takes just seconds is all you need, in my opinion.
JB Weld, Metal Set and other names is almost always nothing more than epoxy and aluminum powder, but for things like this assuming you can get it thick enough to hold in, it ought to work well.
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Old 12-10-2018, 10:14   #37
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Re: Filling Old Rivet Holes

" cracks radiating out from fastener holes in the internal sleeve in the highly loaded gooseneck area of an old one tonner"
I would suspect those reflect the greater stresses, and the greater side-loading from those holes, compared to the light and infrequent loads where the mast steps were riveted.

I've been told that anodizing used to be (basically) a matter of dropping things in a vat of acid, which of course could mean a 60' long half-pipe full of liquid for a mast. But that the EPA long ago decided those chemicals need to be handled specially and disposed of specially, making "anodize" a dirty expensive word.

Meantime, the "coatings" companies have been busy figuring out coatings that will adhere better to aluminum, back in the 70's and 80's painting aluminum wasn't so good.
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Old 12-10-2018, 16:14   #38
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Re: Filling Old Rivet Holes

Anodize isnít so bad EPA wise, itís Cadmium plating that gets em going, and yet, there is still a whole lot of cad plating done.
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Old 12-10-2018, 16:46   #39
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Re: Filling Old Rivet Holes

Anodizing tanks long enough to do 60+ foot mast tubes are not so commonplace. Doubtless they exist, but shipping a big mast extrusion around the country for access to them is pricey and often impractical. Thus, not so many anodized masts...

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Old 12-10-2018, 17:10   #40
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Re: Filling Old Rivet Holes

I have used a tiny piece of aluminium foil tape ...was actually duct tape....trimmed in a circle.....stuck over the hole after painting the rivet hole with an etch prime paint suitable for aluminium.....smooth down well.....etch prime over tape.....to enable paint to adhere.....and paint over......done.
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Old 12-10-2018, 17:12   #41
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Filling Old Rivet Holes

So all these new boats I see with unpainted masts, are bare aluminum?
Iím not doubting you, but it does seem odd, I would have thought the extruder would also alodine.
I donít know if mast manufacturers actually extrude the metal, or buy extrusions and finish them.
If they just buy extrusions, then it would seem that there isnít much to being a mast manufacturer
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Old 12-10-2018, 17:33   #42
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Re: Filling Old Rivet Holes

There is an anodizing shop in Oakland, CA that does the spars for the local mast maker. It's just a bio degradable acid and electrons. 10 times better than paint or powder coating.
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Old 12-10-2018, 17:45   #43
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Re: Filling Old Rivet Holes

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Originally Posted by a64pilot View Post
So all these new boats I see with unpainted masts, are bare aluminum?
Iím not doubting you, but it does seem odd, I would have thought the extruder would also alodine.
I donít know if mast manufacturers actually extrude the metal, or buy extrusions and finish them.
If they just buy extrusions, then it would seem that there isnít much to being a mast manufacturer
Well, I just had a look at Selden's website and they do indeed supply anodized sections. They are a huge manufacturer who supply rigs for many production boat mfgs, so they likely have their own anodizing setup.

Smaller custom spar makers here in Oz buy extrusions from China, mostly, and they are made into finished masts, but in my personal experience, most are sold un-anodized. IIRC, when we had a new mast made here, anodizing was offered, but was VERY expensive, mostly due to transport costs. We chose to use a clear product called Tectyl. Easy to apply by brush, spray or simply wiping on with a cloth. And cheap... about 75 bucks for the spar maker to apply vs 2000 bucks for LPU paint and more than that for anodizing.

So, I suspect that in the main, many of the masts you see on production boats from the big 3 (or whatever) are indeed anodized, and I was wrong.

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Old 12-10-2018, 17:54   #44
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Re: Filling Old Rivet Holes

Anodizing is commonplace, the place I have mine done (in minneapolis) has a vat around 60ft so can do good sized masts. Its actually not expensive either when compared to a paint job. I was also led to believe that hot dip galvanizing was difficult to have done but my son and I had 300 lbs of fabricated steel parts done last year, no problem and again, what we considered to be reasonably priced at $1/lb. They had a 300lb minimum charge. Anodizing is also charged by the weight of the component with a 50lb minimum.
Regarding stress riser, obviously the example I gave was much more highly stressed than the OPs, just pointing out that they do occur with round holes, not just square corners. As I mentioned earlier I would fill the holes with a thickened West systems G- flex epoxy.
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Old 12-10-2018, 18:13   #45
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Re: Filling Old Rivet Holes

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...If they just buy extrusions, then it would seem that there isnít much to being a mast manufacturer
They still have to taper them, weld them back together, fabricate and weld on winch and spreader bases, boom fittings, etc.
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