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CharlieCobra
06-26-2012, 10:15 AM
Folks, we have Kettenburg 50, hull number 6 "Happy Talk" in for a restoration. Mainly seams, paint and fasteners, along with some wood work topside. The issue is that a huge number of the fasteners are pink and wasted. We cannot even get them to turn, much less come out. I've tried everything but the unscrewem's that I ordered yesterday, without much success. She has never been refastened so there's plenty of room to just run new screws alongside the old but I'd rather pull the old ones and use the existing holes. The real issue is that we have to have her done by August first for the Wooden Boat Festival. Any ideas?

pcford
06-26-2012, 10:19 AM
Folks, we have Kettenburg 50, hull number 6 "Happy Talk" in for a restoration. Mainly seams, paint and fasteners, along with some wood work topside. The issue is that a huge number of the fasteners are pink and wasted. We cannot even get them to turn, much less come out. I've tried everything but the unscrewem's that I ordered yesterday, without much success. She has never been refastened so there's plenty of room to just run new screws alongside the old but I'd rather pull the old ones and use the existing holes. The real issue is that we have to have her done by August first for the Wooden Boat Festival. Any ideas?

Did you try easy outs...with a hull that big the fasteners are, what #12s? Might be able to bring them out...if the percentage of bad fasteners is not too great. Otherwise, putting new screws alongside will not cause you to go to everlasting perdition. It's been done before.

Chip Chester
06-26-2012, 12:58 PM
Have you tried the old stand-bys of: Impact driver (battery powered, so torque is somewhat limited), with maybe a few shots to tighten before attempting to loosen? Then there's always heat... slow... and August isn't that far away. I'll assume slotted head, so fit is key. And maybe sacrifice a cheap chisel, ground appropriately, and dedicated to complete slot clean-out/square-up before first attempt. Again, slow, and August. Chip

CharlieCobra
06-26-2012, 06:55 PM
Yep, 50% failure rate so far. Waiting for my unscrewem's. Last chance before I siamese the damned things.

SchoonerRat
06-26-2012, 08:05 PM
Are the screws not turning, or are they twisting off. If they aren't turning, try a brace and bit; make sure the bit is sharp and square. A brace and bit gives you lots of torque and lots of control. I find it's usually necessary to grind the profile of the bit to fit in the countersink of the wood so you can turn the screw without damaging the surrounding wood. You might be able to replace the fasteners with the same size if they aren't too far gone and come out clean.

CharlieCobra
06-26-2012, 09:03 PM
They are flaming pink through and through. I'm doing resets on the slots with a chisel because they're usually gone. Some will turn out, some will spin but most just crumble. Every fastener from the Garboard turn to the waterline is toast.

Tom Freeman
06-26-2012, 09:06 PM
Sorry to hear of the trouble. We had the chance to sail on Happy Talk with Captain Charlie a couple of summers ago. Nice guy and a wonderful boat. Best of luck with the resto.

chuckt
06-27-2012, 07:16 AM
By "crumble" do you mean the bit breaks the head as you try to turn? In other words, the head disintegrates--as opposed to the bit walking out of the slot?

CharlieCobra
06-27-2012, 10:38 AM
The head shatters, crumbles or just falls apart. All of the zinc is gone from the bronze and what's left is brittle.

SchoonerRat
06-27-2012, 11:30 AM
If the screw heads just crumble and twist off, the "only" way to get them out is with the Unscrew Um, or something similar.

I've always gone the home made route. Short piece of steel tubing with an id that is just tight on the busted end of the screw. File teeth into one end of the tube and tap a left hand thread into the inside of the tube. Remove the screw head by trying to back it out then chuck the tube in a slow speed high torque drilling device, place the teeth in the screw's bung hole and go.

Best case: You'll grab the busted screw and back it out.
Worst case: The screw will continue to crumble, you drill out the wood around the screw to nearly the depth of the screw and it comes out with the tube or you can grab it with a needle nose pliers.

Don't go any deeper than you have to and go up a size or 2 with the replacement fastener.

or

just leave the bad screws and refasten next to them.

chuckt
06-27-2012, 01:25 PM
A case to leave them in and add new screws? I dont envy you.


http://www.sailaway.net/html/images/AboutBoat.jpg


|:(

Jay Greer
06-27-2012, 01:25 PM
I have had good luck with "Unscrewems". But, there is another easy out tool sold by Snap-On that, consists of a drill guide and a fluted stem shank that can be hammered into the body of the screw after drilling same. Then one can draw out the fastening with both reverse turning using their special hex collet and gentle pull at the same time. Until the advent of "Unscrewums" I used and still use this keen tool from Snap-On. It, normally comes as a set of various sizes of drills, shanks and collets but the parts can be ordered seperatly to fit specific sized screws.
Jay

CharlieCobra
06-27-2012, 02:39 PM
We started using a custom ground Fien blade to clean up and shape the slots first, this morning. The success ratio has risen.

boattruck
06-27-2012, 08:08 PM
Charlie, If you can get em out, it is obviously better, although there are many, many boats out there with a second set of fastenings that are holding up well. We have good luck with the battery impact, the rattle/bang helps get 'em going, I clean the slot with a dental tool or ice pick or the like, the driver bit is custom ground to fit your slots tight and hammered in to each slot before slipping the impact driver on and gingerly bumping forward and reversed, the ones that will come will come on out, the ones that do break, you can go after with the tubular type screw extractor, it is slow, but do-able, whether you can reasonably bill for it is the burning question... Good Luck, Hutch/BT

CharlieCobra
06-27-2012, 08:15 PM
Both the billing and the schedule are the main concerns. While a certain budget is there for this, every single fastener being rotten was NOT anticipated. However, I found some really good Irwin bits and ground some to different blade thicknesses and my success ratio has reached 80%. The spinners are taking the time though. Having to get a curved pick under them while backing them out is taking too much time. Thanks for the assist Folks. Appreciated as always.

SchoonerRat
06-28-2012, 03:48 AM
Glad to hear that things are going better.

You seem to be taking good care of a lot of our transplanted So Cal boats. This seems like the 3rd or 4th Kettenburg you've breathed new life into.

holzbt
06-28-2012, 05:04 AM
I make unscrewums from roll pins available at the harware store. About $.20 a piece. just file left hand teeth with a saw file. Takes a few minutes to make. File teeth on both ends and just flip it over when dull.

For spinners that are loose I use an electricians split shank screwdriver. These will tighten in the slot and usually pull the spinners out.

johngsandusky
06-28-2012, 09:03 AM
When I refastened my Friendship, I had a hell of a time getting the old screws out. Some spun, some slots stripped, some frozen. I tried easy outs (not so good) and Craftsman screw extractors (better, but got dull) on the frozen ones. For the spinners I used tiny needle nosed pliers with the tips bent together to form a slight hook. I found them easier to get out if the slot and bung hole were completely clean, no glue edge locking them in. I used a chisel with the tip ground flat to scrape the hole. By the time I reached the stern I was just doubling up where they couldn't be removed. Removing the screws took many times longer than refastening. Pull those out that come easily, double the rest.

seo
06-28-2012, 09:13 AM
On bigger screws I've used a pneumatic impact hammer, the kind of thing they use to destroy old exhaust pipes under your car. Like this:
http://www.eastwood.com/air-hammer-with-chisel-set.html?srccode=ga220010&utm_source=google&utm_medium=cpc&utm_campaign=zzproduct_ads&gclid=CKiMnMWL8bACFUHf4AodrTEggg
Then I use a grinder to shape the chisel with a square profile so it will clean out the slots and forge a nice new slot profile.
For spinners, I've modified cheap screwdrivers so that they have a short, thin, curved "pry bar" tip that can be used to exert an outward pull. Or grind down the tips of a needle nose pliers, and drive them in (along the plank grain). They chowder up the plank, so that you either have to put in a bigger bung, or put in a regular bung and putty the chowdered spots up. Or just use putty...
I've also taken a piece of steel round stock and center-drilled it to the diameter of the shank of the screw I'm trying to take out. The O.D. of the round stock is the same as the diametr of the screw head (or the bung diameter), so it holds the drill right centered on the screw. With a very fast drill speed and low pressure, it's often possible to drill right through the heat, and down the shank. Then refasten with larger diameter, longer screws.
If the screw persists in spinning, I've also tried having on hand one of those syringe sets of 5 minute epoxy, and shoot a little epoxy around (and hopefully under) the head, the glue (hopefully) has a good enough bond to hold the head still while it's being drilled out.) I have an old 1/4" Rockwell corded drill that turns at 1,800 rpm, which I use for this purpose.

CharlieCobra
06-28-2012, 09:42 AM
Glad to hear that things are going better.

You seem to be taking good care of a lot of our transplanted So Cal boats. This seems like the 3rd or 4th Kettenburg you've breathed new life into.

I seem to have been appointed the Kettenburg "Guru" for the PNW. I'll take it....

CharlieCobra
06-28-2012, 09:43 AM
I make unscrewums from roll pins available at the harware store. About $.20 a piece. just file left hand teeth with a saw file. Takes a few minutes to make. File teeth on both ends and just flip it over when dull.

For spinners that are loose I use an electricians split shank screwdriver. These will tighten in the slot and usually pull the spinners out.

Now THAT'S an idea I haven't heard of and will try...

CharlieCobra
06-28-2012, 09:44 AM
When I refastened my Friendship, I had a hell of a time getting the old screws out. Some spun, some slots stripped, some frozen. I tried easy outs (not so good) and Craftsman screw extractors (better, but got dull) on the frozen ones. For the spinners I used tiny needle nosed pliers with the tips bent together to form a slight hook. I found them easier to get out if the slot and bung hole were completely clean, no glue edge locking them in. I used a chisel with the tip ground flat to scrape the hole. By the time I reached the stern I was just doubling up where they couldn't be removed. Removing the screws took many times longer than refastening. Pull those out that come easily, double the rest.

Yeah, we'll pull as we go and mark the issue next to the stubborn ones. We'll revisit them IF we have the time.

holzbt
06-28-2012, 11:48 AM
Electicians split shank screwdriver. Works pretty well on spinners.


http://ecx.images-amazon.com/images/I/21PNHS8fVwL._SL500_AA300_.jpg

http://ecx.images-amazon.com/images/I/21WBUrMaW-L.jpg

http://ecx.images-amazon.com/images/I/11GSDUrNVfL.jpg

http://ecx.images-amazon.com/images/I/11YK2XUK2iL.jpg

SchoonerRat
06-28-2012, 01:19 PM
I seem to have been appointed the Kettenburg "Guru" for the PNW. I'll take it....
Those boats, more than any other, just say So Cal to me. They're designed for, and built here, most of them started here and we've still got a lot of them.

I hate losing boats...but if that's how you're gonna treat our girls, I could find enough boats down here to keep you busy for the rest of your life.

CharlieCobra
08-22-2012, 11:56 PM
Electicians split shank screwdriver. Works pretty well on spinners.


http://ecx.images-amazon.com/images/I/21PNHS8fVwL._SL500_AA300_.jpg

http://ecx.images-amazon.com/images/I/21WBUrMaW-L.jpg

http://ecx.images-amazon.com/images/I/11GSDUrNVfL.jpg

http://ecx.images-amazon.com/images/I/11YK2XUK2iL.jpg

These things just kick ass. I now own six of 'em.... Forty one hundred fasteners later, we have color on the boat.

chuckt
08-23-2012, 06:23 AM
I'm a little dense. These are good for screws that just spin and won't come out? I am encountering a lot of that myself. Not sure I see how they work. What makes the split expand?

Chip Chester
08-23-2012, 08:53 AM
When you push the collar down toward the screw, the offset blades expand and grip the slot from the inside, pushing out. The grip is often enough to allow some pull to be exerted on the screw as you're spinning.

(The design intent is actually to hold the screw on the end prior to installation.)

If there's a little room at the side of the screw head, I've been known to take a splinter of bamboo (bbq skewer perhaps) and shove it down alongside the screw, allowing it to grip enough to withdraw... Or grind a pair of cheap wirecutters so the last 1/4" of the jaws are very thin, but still sharp, and dig 'em in around the head as it's spinning. Some damage occurs, but it's less than core-drilling out the screw.

Chip

Peter Malcolm Jardine
08-23-2012, 09:08 AM
I have a couple of Snap on spring loaded screw starters in my tool box as well... I find they work well for holding and starting screws in bad places, as well as spinners.

Feazer
08-23-2012, 01:13 PM
To my way of thinking this is a no brainer. You have badly dezinced bronze screws and you want to still try and figure out how to withdraw them ? No percentage in this chase since you will gobble up as much time as it takes to re-plank half of her and if not and you continue trying to remove these wasted screws you will inadvertently do a lot of damage to the counterbores and the customers check book. Those screw are gone and even if you could attach to the heads and they miraculously remained intact they will spin due to both diminished wire or screw body size and decayed or deteriorated oak circumferentially around the screw hole. Pull a few and put a gimlet to the frames and see but I can almost guarantee that is what you will find.

Even if you get them out now you have to go oversized which means rebore ( enough to get to sound oak ) re-counter which can be dicey if the guy lets the bit chatter and causes more plank surface damage. All of this will soon make the job upside down especially on a K-boat. Kettenburg's are lightly framed and built so there is not a lot of extra frame meat to work with but, in my opinion, you need to get on with the job and treat it like it is — a semi custom production wood hull that needs refastening and since the owners let her so far you now have to shoot new screws into the planks and leave the old ones there. It is just a job that requires some finesse since the frames are so light.

Good luck

chuckt
08-23-2012, 04:10 PM
Good points Feazer. For me, the extra time is not important because mine is a DIY project. But your'e right, the spinners (and screws that are too deteriorated to come out) take an inordinate amount of time. Since I am replacing frames, I can almost always go inside with teh multimaster and cut the screws. I do have to get them disconnected most of the time in order to get the old frame out.

Dannybb55
08-23-2012, 08:00 PM
If the screws are that fried then I bet the frames are gone too. How many screw, 5,000?
Danny

johngsandusky
08-26-2012, 05:39 PM
Charlie knows what he's doing, he's a pro.

CharlieCobra
08-26-2012, 07:28 PM
If the screws are that fried then I bet the frames are gone too. How many screw, 5,000?
Danny

Very few of the holes wouldn't take fasteners. We were going from 12's to 14's with the new ones. Those few loose ones took 16's. Less than 300 out of the entire job.

seo
08-27-2012, 10:51 PM
#12 screws in a 50' outside ballasted hull seems very light.

chuckt
08-28-2012, 06:35 AM
In my case, yes, if there a several spinners in a frame, it has been a good (bad?) sign the frame is in poor condition

Feazer
08-28-2012, 07:26 AM
In my case, yes, if there a several spinners in a frame, it has been a good (bad?) sign the frame is in poor condition

this is not always the case but it is pretty easily checked by using a small gimlet tool which can penetrate and withdraw samples from the frame interior.

Wasted or dezinced sil-brz screws do not always cause problems with the wood they are embedded in. If you can withdraw a screw and find the threads, or what is left of them , caked with a dark crumbly material that has a strong almost compost like smell this indicates a problem. I would drill a couple of them oversize and see what the bit brings out. If the wood chips are bright and firm then do some more testing and find out just how much oversize will work for refastening. This of course must be done reasonably since you would not want to shoot a number #20 screw in a 4/4" x 3" strake.

If the screw spins and you can get a small tool under the head and get it out and find the what remains of the threads clear of decayed oak but there are small amounts of dry dusty like brown wood residue with none of the musty composted oak smell then chances are your frame is sound enough for a proper refastening job. Again I would drill and test with the next size screw to insure they will pull up hard. The process of a bronze screw wasting or dezincification means that there is almost always a small amount of electrical current generated around the surface of the screw. After years and years of this it will break down or leach out the lignin in the oak leaving a whitish residue that is tinted with the copper in the fastener making it brown. Most of the time this condition is so minor that it should be no concern and I only mention if because I have seen yards make a big promotion out of it dredging for work.

As I noted before Kettenburgs are built light and # 12 screws is not unheard of. I recall watching a surveyor one time pulling plank fasteners during a purchase survey while at Merrill Stevens in Miami. This guy was very highly regarded in South Florida. He would pull the screw then take a caliper and measure the root or wire size and diameter of the screw threads. I heard him say at least four or five times that the screws were only about 15 or 20% wasted and not to worry ? Think about that sometime and think about what percentage of the screw is actually engaged into the wood. Then think about removing 20% of the screw or most of the threads and then tell me this is a screw and not a tapered nail .

Your nose can tell you volumes about the condition of wood especially around fasteners. Unless the boat is seriously consumed with stray current or an aggravated case of electrolysis chances are the frames should be workable. I have found that seriously decayed frames around fasteners are usually the result of either electrolysis/stray current or slack seams from weak fasteners allowing seawater to work in around the screw holes.

Garret
08-28-2012, 07:35 AM
#12 screws in a 50' outside ballasted hull seems very light.

Neoga is 1.75" AYC on 2x2.5 oak frames. All # 12's - though a few replacements have been 14's. In Neoga's case, the frames are about 14" apart (& closer in the bow & near the horn timber), so there are a lot of # 12's......

I realize that compared to a workboat she is built lightly, but compared to east coast boats I've seen, she looks far heavier built.

Dannybb55
08-28-2012, 04:24 PM
It is always fun to find various screws in a new-to-the-yard yacht. The one that I am working on now had mostly bronze 16 flatheads everywhere with a random and numerous shotgun blast of stainless flathead, phillips and reed and prince bronze 16 and 18s. Now that the refastening is done they are all # 16 by 2 1/2 inch flat head Si Bronze screws. We removed the screws, doweled the frames with oak dowels and epoxy, plugged the planks with plugs to give the new screws something to hold and refastened the hull.
If you have a row of spinners then the frame is usually shot and needs replacing. Often the planks turn out to be too thin from really stupid fairing and have to be replaced. A refastening job is a realy good surveying job and leads to critical repairs to often neglected parts of the hull.
If your screws are made of red bronze dust then your frames are not much better, especially if the screws aren't staggered.
You are liable to find oak flavored potting soil inside and the cheapest way to them is to remove some planks unless she is a Viking long ship.
Danny Nye

Dannybb55
08-28-2012, 04:30 PM
Garret,
Frames do not rot because salt water gets to them, salt is a preservative. They rot from poor ventilation and stagnant fresh water..... deck and port leaks, plumbing, ac drains shower and sinks and open ports/ broken seals. I see this ever day at the yard.
Danny Nye

Garret
08-28-2012, 06:04 PM
Garret,
Frames do not rot because salt water gets to them, salt is a preservative. They rot from poor ventilation and stagnant fresh water..... deck and port leaks, plumbing, ac drains shower and sinks and open ports/ broken seals. I see this ever day at the yard.
Danny Nye

Oh - I am all too familiar with what made her frames rot. Floors too.....

Feazer
08-28-2012, 06:49 PM
It is always fun to find various screws in a new-to-the-yard yacht. The one that I am working on now had mostly bronze 16 flatheads everywhere with a random and numerous shotgun blast of stainless flathead, phillips and reed and prince bronze 16 and 18s. Now that the refastening is done they are all # 16 by 2 1/2 inch flat head Si Bronze screws. We removed the screws, doweled the frames with oak dowels and epoxy, plugged the planks with plugs to give the new screws something to hold and refastened the hull.
If you have a row of spinners then the frame is usually shot and needs replacing. Often the planks turn out to be too thin from really stupid fairing and have to be replaced. A refastening job is a realy good surveying job and leads to critical repairs to often neglected parts of the hull.
If your screws are made of red bronze dust then your frames are not much better, especially if the screws aren't staggered.
You are liable to find oak flavored potting soil inside and the cheapest way to them is to remove some planks unless she is a Viking long ship.
Danny Nye

Hey Danny that is quite an unsual approach to the problem. Here I go and I know I am going to piss off somebody but honestly I don't want some of the less experienced here trying this. Let me explain why

Have you ever tried to split oak, ash or any of the long grained hardwoods. Well it ain't hard with something piercing it at right angle to the grain and then give it a wedge of sorts. I am not sure where you are working and if this procedure is something you do a lot of but it is nothing I have ever heard of and if it was a sound and proven technique I am sure the better builders and yards would be doing this a lot. It may even work on big sawn frames and somewhat tolerable on laminated frames but not one piece bent frames.

Drilling and driving a dowel, that is an oak dowel, with the grain running parallel to the length of the dowel since that is what differentiates a dowel from a plug or bung, into a frame with the grain at 90 then running a tapered screw into this dowel is in effect building a cylindrical wedge. The dowel inserts and is somewhat benign while everything is static in the boatyard but then you force a tapered screw into the heart of this dowel, and you do have to force a wood screw in, and the dowel splits and then expands which in turn splits the poor frame. This poor frame has already been abused by the wasted fastener but this new alien dowel does her in. Down the road you will end up with a split frame, a split dowel and a screw on vacation. To tell you the truth the whole concept is upside down. You are inserting a long grain dowel into a frame at 90 and then shooting a screw into essentially end grain of the dowel —what have you accomplished other than bill out for some exotic sounding cure to an unsuspecting boat owner ? This is the way I see it and it is nothing personal just something that you shouldn't do.

Doweling adrift or loose fasteners is a furniture trick that works marginally on tables and the like that don't live the same life as a bent oak boat frame. I had a furniture builder or two in my shops and it took them several weeks to figure out that their squares were a bit too foreign and unuseful for the business.

Dannybb55
08-28-2012, 08:25 PM
Your right, It is much better to replace the frame when the inside is soft. We keep the Oak repaired with Oak and the Mahogany with Mahogany and don't try to trunnel the two together. Your are right about splitting firewood. We wait til the glue dries first and counter sink the screws first. We also butter the screws with Dolfinite and don't overtighten. The goal is to get the screws to bite, not spin. We can replace the frame some other time. When there are 80 frame stations it is better to replace frames over time as the money is available. we have gravered frame with one inch splnes if the plank is off. A lot of our work is repair FIXES from those other big yards with repairs. A repair being defined as returning the structure to the state and form that she was in when new. Fixes are patches that look wrong and need repairing later.
I splice in 5 frames these last 2 days and a floor with 4 more in the bow and 4 more in the shaft logs. 9 to 1 Lloyd's approved with epoxy, bedding compound and new fasteners. New inner planking and planks on top. That is how we do it when we get the ok. The refastening was to solve the eletrolysis problem and she will be ready for more work next year. We can't repair everything at once with our time limit and budget but we are getting her back to where she was once. Those dowels are only for spinners where we couldn't get the frames replaced.
Danny

Rich Scheffer
08-28-2012, 08:54 PM
After you finish and launch her, take a hull potential and look for electrical leakage. Maybe even check the shore power at her dock for stray current. no sense in ruining all that work in another couple of years. Rich

Feazer
08-28-2012, 09:00 PM
Danny

You sound like a crew that does a lot of creative repair work and busy both of which says something positive. Always more than one way to do job and more than once I have been told I was stuck in the past. Good luck to you and continue to do what you think is right and most of time you won't be far off

pcford
08-28-2012, 09:57 PM
You have badly dezinced bronze screws

Dezinced bronze screws?

CharlieCobra
08-29-2012, 09:58 AM
Yep, pink bronze shows that the zinc has been leached out by electrolysis. Funny thing about cross grained sets on bungs. I gave a lecture to my bung setters about that not long ago...

Feazer
08-29-2012, 11:37 AM
Dezinced bronze screws?

I assumed everybody knew that sil-bronze contains certain percentages of zinc. Zinc is added for machinability since without it the bronze is too soft to cut threads or whatever. Good high quality REAL sil-bronze should not have more than 2-5% zinc, or near that, however there are so many so-called silicon bronzes out there with much more that you have to be careful. In fact bronzes like maganese bronze or cheap propeller bronze may have 30% or more and technically it is really a brass but the powers of marketing are great at muddying the waters.

I was involved many years ago with the USN who actually tested a number of sil-bronze fin headed bolts that were in the supply system and they found a couple of lots with 15% and more zinc which explained the short life of these for underwater and deck machinery applications.

Marketing agents and their lawyers have been able to push the real truth about products right over the cliff in the past twenty to thirty years. I know in the furniture industry the term 100% Wood or Solid Wood can mean a legal percentage of solid wood particles or manufactured panels or a mysterious percentage of solid wood parts in a furniture piece. Think about HP ratings of electric motors. A small motor that used to look like 1/2 HP can now be called a 3 HP motor which it may develop at speed with absolutely no load on it but touch your finger to the shaft and the sustained HP may be a fraction of the labeled rating. How about ' All Meat ' ??
or ' fresh crab ' which is always really fresh frozen crab. You could spend your life on this trend.

pcford
08-30-2012, 09:17 AM
[QUOTE=Feazer;3517391]I assumed everybody knew that sil-bronze contains certain percentages of zinc. /QUOTE]

I don't know about "everybody" but I did. What prompted my note is your implied point that "dezincing" is the obvious cause for wasting of bronze fasteners. While I am certainly no metallurgist, but I think there may be other causes. A quick Google confirms this. Somewhere in the midden is a copy of Nigel Warren's book on the subject of metal corrosion in boats; I suspect he may suggest other causes.

And I might add, a rude and condescending attitude may impress in the short run, but eventually it loses its charm for your audience. Also, posting with your real name will add to your credibility. As things are, one can't help but wonder why you withhold this information....the mind does wander.

added: I have always wondered about the causes of bronze degradation obviously there are many (and ways to prevent it.)...I can't remember if Nigel Warren's book addresses this specifically. If anyone has a pocket survey I'd appreciate it....