I'm having a few parts made, including an new backstay chainplate, and on page 152 of the manual I can't read the bend angle. It didn't copy too well. Someone with a better copy able to read it? Thanks!
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I'm having a few parts made, including an new backstay chainplate, and on page 152 of the manual I can't read the bend angle. It didn't copy too well. Someone with a better copy able to read it? Thanks!
We must have the antiquated first edition here for there is no page 152 in this beat-up and tattered manual. There is, however, a spec sheet that has an angle of 57 degrees and 113's back stay chain plate was fashioned to that angle and seems to have worked for the previous owner and will suit my needs I suspect. Tony G.
Thanks.
I looked really hard and it appears the second number is a seven! Thanks for the first number.
If you're replacing the backstay chainplate, I'd recommend using thicker stock than Pearson used. They seem to bend a bit. Here are a couple of examples:
Or, this one:
The 2nd chainplate came out of #76. I had no idea it was anything other than perfectly straight, until I tried to remove it. Could not understand why it would not pull straight down . .
The first chainplate came from #312. It got that shape because of a collision with a piling! The sudden stop pulled the backstay chainplate half way through the lazeratte hatch!
Additional anchoring bolts near the top of the chainplate would appear to be in order. Or, do as Ebb is planning and go to a split backstay.
Good night!! 113 had a couple of boxes of 'junk' that the previous owner threw in with the deal and the original chain plates were among the parts and pieces. They looked pretty thin but that scares me! 'Sure am glad he replaced them with 1/4" and moved the backstay over the stern. I can deal with a little stainless showing better than mangled boat parts. Now I'm gonna have to look at the chain plates on my other boats just outta paranoia.
Bill,
Your photos have convinced me to go with a thicker piece of stainless. As they say, a picture is worth a thousand words. Very convincing!!
Today, as we were measuring for a replacement backstay chainplate, my machinest friend and I discovered that the "bent" original may have come that way from the factory :confused:
It seems that the knee to which the chainplate is attached, is located dead center of the boat. To get the chainplate centered so the backstay would be centered, it appears Pearson gave it the double bend shown in the above photo of the chainplate from #76. We varified this by peeking through the chainplate slot in the deck.
Given the way these boats were put together, your results may differ :p:
OK, I give up. I thought I knew what I was doing. My brand new 304 stainless steel extra-thick backstay chainplate backstay chainplate fits flat against the knee, and slides ever so nicely up through the slot in the deck. It was made by the same shop that made an identical chainplate, using the original very thin and very tired original backstay chainplate on hull #330 as a model. I did not use the earlier version made by that shop since my contractor subsequently drilled some extra holes in it that in my opinion made it less than sound.
The contractor removed and disposed of my old chainplate, so I never saw it out of the boat. I do know that before it was removed, the original factory-installed chainplate showed sings of metal fatigue at the very top from twisting by the backstay tension adjuster, but I do not recall a bend.
I have been sailing around in the ocean all fall happily with my new staright-as-an-arrow backstay chainplate installed, and it seems to work just fine. I did add a couple of extra bolts through the knee above the three factory-drilled bolt holes. I cannot conceive of why one would need to bend the backstay chainplate, since the backstay chainplate slides right up through the deck slot, and bolts securely to and flat against the knee, and since the backstay wire rises ever so nicely from the top of the chainplate at the center of the transom to the mast head.
My last boat, a Catalina 22 had a single backstay that was tied to a chainplate set deliberately off center to keep it out of the way of the transom-mounted traveler. Bending the backstay chainplate seems less structurally sound than an ever-so-slightly off center backstay attachment point.
So my question is: Why bend the thing at all?
:confused:
Scott, good question :confused: Our analysis may be faulty and it may be just happenstance that the bend in ours takes the cp through an out-of-line hole above the knee. Your extra thick, 304 ss chainplate sounds good to me. I think I better take another look through that hole in the deck . . . :)
Bill,
If you would make your eagle eye inspection and post what you think is going on I'd appreciate it! I haven't had anything fabricated yet--- this is one of those things that has three chapters to it, and by my count, we're probably at chapter two, one more to go to get sanity!
Ok, took another sighting down the chainplate hole today and saw the knee filling in the view, but not all of it :confused:
Next, used a straight edge poked down the hole, and yes, it did fit . . . :mad:
So, I guess you should ignore my original post, although I still think Pearson bent my chainplate a little to fit . . . :p
Ebb has the right idea, go to a split backstay . . . :cool:
Bill
I've been watching the backstay chainplate story unfold. I believe you when you say Pearson bent your chainplate. I'm young but I've seen weirder things done on the job and maybe that's why I choose to be self employed and away from that sort of time clock mentality. But I am interested in why you think that a split backstay is the way to go. Is it more performance that you're seeking by tuning the mast? Or maybe it's the additional security of spreading the stress over a larger area? If it's tuning why not go to a hydrolic adjuster? Tell me anything other than it's just deep pockets of west coast money:p
Tony G
Yikes, talk about cost. An hydraulic adjuster runs about $1,000 so it's not a consideration. :) A wheel adjuster runs about $325 and a turnbuckle adjuster about $185 for our wire size. A split backstay adjuster, however, is only $30 ;)
My reason for going to a split backstay is primarily race related - makes adjusting the backstay easy and is cost effective (see above). The shrouds are due for replacement (1988) so the marginal cost of splitting the backstay cable will be low relative to the total. The "only" added expense is getting the chainplates fabricated and installed.
A secondary consideration is what appears to me to be the under engineered backstay attachement (that little knee in the lazarette). It's lasted only 40 years, but still . . . :p
Bill,
I wonder about whether the lamination in the transom is sufficiently strong to take the load of the backstay without reinforcement. Perhaps someone who has done this will comment. It would seem to be a simple matter to glass in a set of reinforcement panels on the inside of the transom to accommodate a split backstay, but this would increase both the cost and complexity of the modification if such reinforcement were required.
I opted for two more bolts through the knee and a new thicker single backstay chainplate. I figure that if the original lasted 37 years this one ought to last awhile. I do have a turnbuckle type backstay adjustment device, that in it's current location requires backstay adjustment wrench that I made out of PVC pipe and a few miscellaneous pieces of hardware, but it all works just fine.
Also I like the look of the nice clean transom sans external chainplates. See photo
Scott,
As I recall, extra reinforcement was added to Gene's backstay mounting knee when the backstay was replaced (see photo of blue painted backstay above). I need to take a look the next time I'm aboard his boat (#312).
Bill,
I apologize for being other than clear. When I referred to reinforcement of the transom in my lasty post, I was referring to reinforcement for a split backstay. The manual already refers to the need to reinforce the knee for an externally mounted single backstay if one is installed.
There are a couple of boats out there with split backstay setups. One local boat has the chainplates externally mounted on the transome and through bolted to major backing plates.
The second boat of which I'm thinking, has internally mounted chainplates that protrude in the same manner as the stock single chainplate arrangement. How this setup is fastened, etc., I have no idea as I've only seen a photo. Not sure where the boat is located. May have been a photo on our forum . .
Ebb's planned installation has externally mounted chainplates at the outer edges of the transome. The shape of the chainplates matches the curve of the hull and then sweeps up behind the end of the toe rail. Very impressive looking. Ebb plans to install very substantial backing plates, one side of which will be curved to fit the shape of the hull. At least I think that's the plan:)
External manganese bronze (East Coast) plates - w a y out on the edge so that the tangs come up aft of the end of the toe rail. You'll hardly know they are there.
Because the hull "falls away" from the transom there is plenty of space inside for the washers and nuts to seat well - especially if you create a pad of mishmash (epoxy, chopped strand, cabosil) and mold it in with a piece of plywood with mylar stuck to it (two sided carpet tape sticks it.) You want to have the build up parallel to the outside of the transom.
I'll reply if anyone's interested how to acheive this miracle. By the way I can get one arm and a head up in 338's OB well from outside to work on the inside of the lazarette - no grease and no mirrors. There is a West Coast patent on this process.
Ebb
Of course we want to see it! I mean, a grown man hanging out of the bottom of a boat? Who in their right mind wouldn't?
All humor aside, when you say ' build up parallel to the outside of the transom' are you implying an even thickness of laminated backing material(epoxy, chopped strand, carbosil in your case)that would be parallel to the chainplate and perpendicular to the mounting hardware? Or is there some inherently quasi-nautical, planer geometric engineering religious thing here I'm not gettin here. Are your chainplates going to be square to the transom or will they be square or with the line created by the back stay running from the mast head to the chainplate? Which brings up another question-two separate back stays running from mast head to chainplate kind of like a running back stay or one that is split into two somewhere along its length? Can they even do that? Around here we have to use a couple of pieces of bailing twine knotted together to make a back stay. Sorry to read about the tent mishap. We hope it doesn't set you back. Tony G
wait wait wait a minnit Tony....
Parallel in my speak means only that the mishmash pad is of one thickness and in the same plane as the transom. Like a piece of plywood or mahogany. The chainplate holes are drilled thru the transom and epoxy pad allowing the washers to seat flat against the pad. It's just that no wood is used. It isn't a place that can be easily inspected.
The plates are tangs that are bent inward over the toerail ends and twisted slightly more inward so that the split single backstay triangle plate is about 5 feet off the deck. Twin backstays are frowned upon on the West Coast, mainly up in Pot Townsend
Here is the Port Townsend denunciation of double backstays.
http://briontoss.com/education/archive/miscapr99.htm
On the knee in the lazarette where the single backstay chainplate goes, I think the plywood is susceptible to water damage. The top end of the plywood is open. If the chainplate cover is not well bedded, water can leak down straight into the plywood. Can also run down into the screw holes.
Not something that you would notice happening.
Mine was good. But I still sealed up the top of the plywood with epoxy. I also ground off the paint on and around the knee and added four or five overlapping layers of biaxial tape and cloth, out to about 6 inches on each side.
Very interesting article on split backstays. Guess what I'm considering is a "forked" backstay. The article indicated that the forked backstay is not held in such low esteem as the split backstay, but nothing further was said. My question therfore becomes, should we use a single backstay with an(expensive) adjuster, or fork the backstay with a (inexpensive) backstay adjuster? :confused:
Carl Alberg and a pretty good idea. He was a designer to whom we all trust our lives. The question is how long did he intend the knee and chainplate to last before replacement, reinforcement etc?
maybe the point got smoothed over with the aquavit and beer chasers they toasted our sweet little boat with? Maybe that i/2aft knee and strap backstay anchor point was an afterthought that they never thought about again. After. Just too far 1/2aft.:D
But what do I know?
I would like to hear you SAILORS go a few rounds over the forked block arrangement or the single backstay wheel johnny. And I'm not even a racer. What are the pros and cons here?
(by the way, if you are interested in the split backstay idea (NOT the dual) Bill's first photo on the ebb gallery page shows the two cast manganese tangs (chain plates) that I had been trying to carpet tape to the transom to get a look at these things just received.....when Bill arrived that day with his forensic camera.)
Here are a couple of examples of deck reinforcement for the backstay chainplate:
And this:
Has anybody here made the modification to a split backstay? That is something I have been considering.
We're considering it, but need to discuss the details with a rigger. Ebb is also considering and has a pair of cast bronze backstay chainplates ready do go. I believe there may be a photo of them on the thread "Ebb's Photo Gallery."
There is also more discussin of this in earlier posts.
In the midst of what is becoming an accident-caused rig re-fabrication project, I figured that I might as well pull the chainplates given that the rig is down and all. Pulling those forty-year-old suckers was all that pulling chainplates is promised to be. About half the bolts twisted apart when I as removing them. A view of the first photo below will show you why. Most of some of the bolts were pink. This occurred mostly on my aft lowers, which must be removed and reattached twice per sail due to the tabernacle, and so they probably have leaked more water than the other chainplates.
The chainplates themselves seem to be in pretty good shape although beneath the green corrosion is a layer of reddish metal (colloidal copper I presume). In the second photo you can see that red color. The top and bottom chainplates in the second photo have been buffed up a bit with a nylon drill brush and the middle chainplate is it looked upon removal. You can still see the polysulfide band where the chainplate passed through the chainplate cover.
You can see some bright spots where the bronze is shining through. A wire brush head did not get this red stuff off, but for some reason the nylon brush head did to some degree. These appear to be original chainplates, and if so, they are forty years old or thereabouts. I don't see any cracks or excessive wear, but the condition of some of the bolts and the fact that about 25% of the bolts that were bronze in color throughout sheered off upon removal, I think that I may replace the chainplates as well as the bolts.
Removal time was four hours from start to finish working alone. Don't do it that way. It's a pain to be workign alone when the bolt head is on one side of the closet bulkheads and the nut is on the other.
Now the questions:
1. If these bronze 3/16 chainplates lasted forty years, why not have new bronze chainplates fabricated?
2. Would it be better to used stainless steel chainplates for strength even though stainless tends to degrade in wet oxygen-deprived environments, like sometimes-leaking deck cores?
3. If stainless steel is the way to go, should I go with 304 for strength or 316 for corrosion resistance? My backstay chainplate is 304 stainless.
I did do a search on “chainplate” and “chainplates” on this forum but found that the discussion on the various links provided in the search did not address these questions. By the way, the search function is working very well now. Thanks Bill and Bill II.
I intend to grind a bit of damaged wood from the deck core surrounding the chainplate slots and screw holes and fill the deck voids, chainplate solt and screw holes with epoxy. I will then drill and cut new holes before mounting my new chainplates or the current refurbished plates in the event that after final clean-up and inspection by a rigging wizard, the existing chainplates still appear to be serviceable.
I have received two quotes for new 316 chainplates and they range from $60 to $80 each. Ouch!
So does anyone have a source of bronze or SS chainplates in the Bay area? Or is any manufacturer anywhere still making the plates installed in our Ariels/Commanders?
Here are the chainplates. Again, the top and bottom plates are buffed up a bit: The Bottom one more than the top. The shiny areas on the bottom plate are bronze-colored in real life, but the red-colored areas are just as red as they appear in the photo. Hmmmmm.
I do like bronze for this applicattsion. The chainplate covers are bronze and servicable, and replacing them with stainless would add to the expense of the project, although I suppose I could use stainless chainplates with bronze plate covers. They are separated pretty well by polysulfide bedding compound.
Any thoughts?
Found this thread whilst "searching" and thought I'd add another pic of another woefully inadequate Backstay Chainplate. The knee looks OK, but as CP pointed out, inside the lazaret it is open on the top and subject to water coming in from the chainplate opening in the toe rail.
Here's the bugger that was keeping me from removing the chainplate...
best you could have hoped for is what happened with that retired bolt (twist in half)
I replaced the bent over backstay chainplate on my Commander with one that I had made from thicker stock marine grade stainless steel(Navy scrap).A Pearson Tritan had rode up the backstay bending over the chainplate and also destroying the pulpit during Isebel which sank or damaged many boats at the yard. Just think about how strong that single backstay is to take that much damage. I had the new chainplate made an inch or so longer with an extra bolt hole. There are some pictures of the damaged stay and of the new one on this site somewhere. Why go to a split backstay? In addition the old insulator is still good as new. The 26 Pearson that I now have has a split backstay because of the motor well. When I get around to it I plan on replacing the backstay on my Commander with one that has an adjustable tensioner. I will try and keep the old insulator it seems to be stronger then the new ones that I have looked at. :o
Anybody else have a larger (7/16 vs 3/8 inch) turnbuckle on the backstay? Not sure why my boat did.
Nice rig tuning here
What were you doing on a Hunter ?
Saw the same thing on Bluenose II foremast .
I think he was going for that high tech sail shape . . . :rolleyes:
I just got this back. This is the replacement for the one in post #28. The original was flattened to make the template for the new one. I'm confident in saying, my Backstay Chainplate will no longer be the weak link back there. It was made with 316 stainless. A couple of more holes were added as per the manual also...
Mike, looks like the one I had made, real beefy!!
Hey Kent, you got any pictures/pointers on your installation?
PS. The heat up here this week reminds me why I moved from Austin a few years back - only there's no AC to retreat to up here! Yuck! :mad:
Here is a question on the backstay chainplate. I had a new backstay chainplate made and I installed in 2002. It was made from 304 stainless and is pretty beefy. The argument for 304 at the time was that it was stronger than 316 stainless, which is true apparently, until it corrodes. I want to eventually replace it with 316 stainless, since the darn thing seems to be rusting in the salty lazarette environment. To date, the rust seems to be superficial, so I have not been in a hurry.
All seemed well for four years, but after a couple of days of heavy wind (30-35 mph) last month, I noted that the backstay chainplate cover had risen somewhat at the forward end. I removed the screws, cleaned the chainplate cover and chainplate of old polysulfide caulk and superficial rust and rebedded the cover. The cover slipped very nicely back over the chainplate, but the screws that hold the cover to the fiberglass deck now seem to be somewhat forward of the original holes in the fiberglass deck. They fit in the holes, but at an angle sloping aft from top to bottom.
So this is a concern to me. I took the boat back out on a 30- 35 mph day and sailed lose hauled and on a broad reach in four foot swells both unreefed and later double reefed, and the plate popped up in front again slightly. The front screws are loose in their holes, so they are not really holding in the deck, but there must still be some upward or forward pressure to pop the plate up, and to have moved the plate forward slightly so that the screws are no longer vertical. I can't recall for sure whether the screw holes were actually vertical in 2002, but I can say that the cover has never popped up before. If the width of my (new in 2002) backstay chainplate was slightly greater than the original, the screw holes would not have aligned.
Inspection below tells me that the backstay chainplate still seems to be well secured to the knee with the original three bolts and two additional bolts that I added at the time of installation in 2002. One of these additional bolts runs through an extension that I glassed on to the top of the knee. The extension seems to be solid. So all seems well below, but yet the chainplate must have somehow bent forward or slipped forward slightly. For four years this was not a problem. Now I seem to have a problem. Or do I?
In intend to remove and inspect the chainplate and then order new one made from 316 stainless and of thicker stock, but I am curious about why this might happen, as the thickness of my 304 stainless steel chainplate is substantially greater than what was there originally.
I replaced the original based on the experience of others on this forum and the recommendations of the Ariel Manual. A thicker chainplate seemed to be in order. My original chainplate, scrawny though it was, was not deformed in any way. The new chainplate was supposedly cut out of 304 stainless using the original as a template, so the width, length and forward to aft sloping angle of the top section should be the same as the original. Any thoughts?
From our experience tuning the boat for racing, I've found that the tightened backstay will pull the chainplate forward. I don't believe it's moving where attached to the knee. The bolts and all are fine. Rather, the stern portion of the hull may actually be "bending" a bit from the stay's pulling force against it. As noted in the manual, probably the real fix is to reinforce the weakest part of the boat -- its stern.Quote:
Originally Posted by Scott Galloway
I was looking at the A286 on ebay and noticed his back stay,
On the single backstay chainplate, imco, just the way the system is designed it has to loosen up. The chainplate is pulled forward (as well as Up) above the deck. Below, the bolts are being pulled by the plate in those two directions. The plate is attached to One side of the knee. And the knee is wood. There has to be Some movement in this scenario. How can it be avoided when the boat is sailed?*
The original thin backstay plate could easily twist in its attempt to straighten itself to the loads on it. Result being a loose stay. The same may be happening to an upgrade that somewhat duplicates the original system.
In 300 series s.s, a problem occurs when you get a small active area attacked by a large passivated area. When salt water gets into a tight place like thru a rubbered hole in the deck or under a washer behind a nut, oxygen is kept away from the steel so it can't maintain its passivation.
These steels have a small amount of carbon in them that will combine with the chromium and make carbide. In cloride water an electrical reaction occurs between the combined areas and the uncombined areas. Pitting and crevise corrosion is what's happening when the boundarys break down.
It's impossible to know what steel you have and how it has been worked. Bending drilling heating welding may change properties. 304 has more carbon it it than 316. Carbon is the problem in salt water, so in 316 it is held to a specific minimum and molybdenum is added to keep those grain boundarys together. Guess it holds the chromium in check? That's why highly polished 316L (passivated) is not as sensitive to partial encapsulation, or oxygen starving. (It's still not trustworthy, imco.) The trouble with pit and crevise corrosion is that it may not be caught or noticed befor the metal just lets go.
__________________________________________________ _____________________________
*imco, An external backstay chainplate on the transom is the best way to go. With the top bent at the proper angle and four 1/2" bolts (bronze), there is no stronger connection. It is also my opinion that there is no force that is going to bend the stern of the Ariel in way of the backstay. One might, as a test, spring a batten between the coamings, fore and aft in the rear hatch, and see while sailing if there is any change in the bow of the batten. It's a huge hole in the rear deck there. But I'll bet NO change in dimension will be observed! :eek:
Very interesting idea Bill. I'll have to think about that one, but I do agree with Ebb in that flexing of the stern would not seem to me to be consistent with the movement of the cover plate forward to the degree that the screw holes are out of alignment. (cover plate holes now forward of fiberglass holes that once aligned). If the transom (and aft rail) was flexing forward and the knee with it, the whole assembly would move in unison, would it not?
For four years there was no movement of the backstay chainplate cover plate, but now there is. If the transom were deflecting, then this should have been a problem all along. It wasn’t. I am interested to see when I remove the chainplate if the bolt holes have elongated to any degree in the wooden knee. This would allow some slippage, although the chainplate seems solid as a rock when I put pressure on it at the dock.
As far a Ebb's crevice corrosion issue, that is correct Ebb; crevice corrosion will be worse for 304 than for 316 stainless. That is why I plan to replace my 304 backstay plate with 316 eventually. You can find a nice discussion of this phenomena and a lot of other cool stuff in “Dan Spurr's Boat Book.”
After I pull the chainplate, I'll let you know if there has been any crevice corrosion, but based on how the chainplate looks and after only four years, I strongly doubt it. Leaking from above through the polysulfide caulk is the least of your worries when your chainplate is in the floating aquarium of your lazarette locker. The salt water splashing up from below will probably do a lot more damage than the fresh water leaking in from above in the long dormant winter months.
The issue here is that not everyone wants a chainplate or two on the outside of their transom. Carl Alberg and Pearson decided to put the backstay chainplate on a knee in the lazarette locker with a heck of a long unsupported neck that bends forward. As strange as that seems to us all, it also seems to have worked just fine in most cases for forty plus years. Refining that system in a retrofit with modest moifications is a reasonable thing to do without having to re-engineer the transom or slap external chainplates on the transom. Also, despite the fact that we are all bronze lovers at heart, the yards and rigging shops these day are making their chainplates from stainless steel and not bronze.
The question remains: What factors, absent corrosion of the chainplate, would cause the chainplate to pull forward and or up in the direction that backstay forces would tend to pull given the fact that the chainplate is bolted to what appears to be a solid knee. Perhaps all that is happening here is that despite the width of the unsupported “neck” of this backstay chainplate, there is enough pressure to gradually bend the neck forward. That is a scary thought, but not inconceivable, in as much as Bill's chainplate pulls forward when he tunes his rig for racing. if that is all that is happening and the flexing is not enough to cause metal fatigue, then perhaps there is no problem. It's till a bit spooky though to see that little chainplate cover pop up under sail.
In 2002, some work was done to my standing rigging by a professional rigger. At that time the rigger installed a 3/16 inch backstay chainplate made of #304 stainless steel. This chainplate was thicker than the original, but one of the bolt holes left a bolt partially exposed at the top of the knee, and another bolt hole was drilled in the wrong place, and had been re-drilled, leaving an unfilled hole.
In 2002 I removed and replaced that chainplate and had a new chainplate, which was identical, except that the boltholes were where I wanted them. I also glassed a small extension at the top of the knee. The fifth (topmost) bolt passed through this knee. I cut the professionally installed chainplate into two pieces intending to use the lower portion as a backing plate, but this proved infeasible. I kept those two pieces.
Do to circumstances described in an earlier post above, I removed this “new” backstay chainplate on August 13, 2006. With the exception of a small amount of what appears to be crevice corrosion adjacent to the cover plate (See Photo), and two areas near the bottom bolt hole and the bolt hole third from the bottom, no corrosion was evident with the exception of superficial rust that removed easily with bronze wool. The pits near these two boltholes may have not been caused by corrosion at all, but may instead have been preexisting imperfections in the metal at those two locations. The stainless steel looked like it had been etched at those locations. No rust was evident. In all of the above cases, the corrosion was minor and did not result in any significant weakening of the chainplate.
The chainplate installed professionally in 2002 was installed, but never used. The rig was under tension then, but I did not sail the boat before replacing that chainplate. The chainplate that I had built to replace it was installed by me and used under sail on approximately 150 days between 2002 and August 13, 2006, when I removed it for inspection. Photos C and D show that the chainplate has a definite bend in it laterally. This bend was caused at the time the chainplate was bolted into place, since the chainplate slot in the deck (taffrail) is slightly to the starboard side of the knee. The chainplate must be inserted through the slot in the taffrail and then pulled back against the knee in the bolting process.
Photos D and E demonstrate that this bend is identical to the bend that was in the chainplate that was installed but never used under sail. It is also evident from photo D that the two chainplates have identical outlines when laid flat with the professionally installed plate on top of the plate that I installed and used over a four-year period (150+ sails). Since these two plates are identical in outline and in lateral bend, there has been no observable distortion either laterally or longitudinally.
Photo F shows the entire chainplate with its cover plate in place. The angle of the transom and the angle of the longitudinal (Aft to forward) bend in the plate make the Ariel backstay chainplate operate essentially as a lever, where the backstay forces are operating on the handle of that lever, pulling it forward and up. I loosened the nuts on the bolts, and experimented by placing forces on the top of the backstay chain plate. The evidence that I found on my boat (hull #330) is that this lever will take advantage of any disparity between bolt size and bolt hole size in either the chainplate or the knee. Although I found no evidence that the bolts had enlarged the drilled holes in the wooden knee, I had no trouble wobbling the bolt in most of the holes. This was also the case in the chainplates themselves. Observation led me to believe that the holes in both the chainplate and in the knee were drilled slightly larger than the bolt diameter, as could be expected.
Photos G and H show the degree to which the bolt will work in the chainplate hole. A similar degree of motion was possible in the boltholes through the knee. I believe that under sail with higher wind loads (30+ mph) this potential for movement permitted the backstay to rise and pull forward sufficiently to push against the forward edge of the chainplate slot in the deck causing some minor gelcoat cracking in the deck, and also against the cover plate, which raised the front edge of that cover plate, and causing the cover plate screws to elongate their holes in the fiberglass deck.
Observation tells me that the knee is solid, no corrosion of the chainplate or bolts is evident, and no knee failure is evident. I do not believe that the transom is pulling forward. I believe that the lever arm of the chainplate is merely pulling on the bolts and that is causing some slippage due to sloppiness of the boths in their drileld holes. Of course this is just a theory. I invite other perspectives and ideas.
In attempt to remedy the problem, I removed the chainplate, filled all cover plate screw holes with epoxy, and I will re-drill them. I coated all boltholes in the knee with West System epoxy and then I added a thin coat of the same epoxy thickened with colloidal silica. I will file the holes to permit a tight fit of the chainplate bolts using a round file. I also did this with my shroud chainplates when I installed them in 2004. Finally, I sanded a slight forward slope from top to bottom in the forward edge of the fiberglass deck chainplate slot so that if there is still some motion of the plate in the slot, it will not put pressure on the fiberglass taffrail and cause more minor gelcoat cracking. I was thinking about replacing the #304 chainplate with one made from #316 stainless steel, but it does not appear that this will be necessary in the short term. Removal and inspection of the chainplate took about one hour. Reinstallation should take a second hour including re-bedding the cover plate. #304 stainless is stronger than #316, but more susceptible to corrosion.
Any thoughts?
Scott, thanks for the very thorough inspection and photos. I like the "beauty" cover for your chainplate - I've been wondering what I'm going to do about that and wishing I had one made too.
I'm wondering about the setup you describe below:
Just a couple of thoughts for discussion. I would think enlarging the slot in the taff rail to allow the chainplate to freely exit without being forced to bend would accomplish at least three things:Quote:
Originally Posted by Scott Galloway
1. Reduce unneeded lateral stresses on the knee and on the chainplate itself.
2. Allow the chainpate to be bolted snugly to the knee, which would eliminate any "play" the bolt holes may have, and I would think you don't want.
3. Eliminate unneeded stress on the taff rail.
Are bigger bolts out of the question for your chainplate? I'd think "play" is a bad thing.
An anternative improvement to the Pearson backstay on the Ariel would be to have a chainplate on both sides of the knee. IE TWO chainplates of exactly the same pattern.
The plates would be flat with no kink in them.
You could toggle between the plates for the turnbuckle.
The stress on the plates would be more even and you probably could keep the hole(s) through the sternrail caulked.
You probablly could use the same miserable BBQ tong material since you have now doubled the specs and evened the forces. :cool:
That is exactly what I have on #226. Prior owner's 'beter idea' that seems quite a bit stronger then the original.Quote:
An anternative improvement to the Pearson backstay on the Ariel would be to have a chainplates on both sides of the knee. IE TWO chainplates.
Nothing new under the sun, ehhhh, Craig? :rolleyes:
Isn't it wierd that the A/C has that nice stem casting, bronze shroud plates
and that dinky backstay strap?
Almost an afterthought. "Oh, hey Carl, we forgot the backstay this time. Wudowedonow?"
An UPgrade would be to keep the theme going from the front end of the boat.
Use some bronze plate. Just an opinion.
In answer to MDB,
"I would think enlarging the slot in the taffrail to allow the chainplate to freely exit without being forced to bend would accomplish at least three things:
1. Reduce unneeded lateral stresses on the knee and on the chainplate itself."
Pearson simply put, the knee or the slot in the wrong place. This is also the case for some of the shroud chainplates. They also had to be slipped through the slot at an angle and then pulled back to the knees or bulkheads. I can just imagine a guy at the Pearson factory with a saber saw taking a wild guess from above at where to cut a chainplate slot to align that slot with the knee.
So unless you want to cut a new slot or have a humungous hole in the taffrail, which is itself a structural element, The bend (or kink as Ebb calls it) is a reality. This necessarily means that the chainplate may not be snug against the knee at the top most chainplate hole, which is probably not a good thing. Ebb's idea of having backstay plates on both sides of the knee is an interesting idea, and I thought about that, but it is probably overkill for limited coastal cruising and day sailing applications. The governing issue here is how strong is the knee attachment to the transom in relation tot eh strength of the chainplate assembly. I thought about twin chainplates with a teak or synthetic spacer in between them above deck, but decided not to do that. Again in four years of use there has been no observable corrosion of stress deformation of my 3/16 inch #304 stainless steel backstay chainplate.
"2. Allow the chainplate to be bolted snugly to the knee, which would eliminate any "play" the bolt holes may have, and I would think you don't want."
Yes it would certainly do that. I believe, however, that the play in the bolt holes is due to the size of the holes. I also noted this with my shroud chainplates, so for the shroud chainplates, I reinforced the bulkheads and knees and then lined all of the bolt holes below with epoxy. Ithen filed them to the perfect diameter in a one-by-one laborious process. This will be even more fun in the difficult to reach spaces of the lazarette.
The difference between the shroud chainplates and the backstay chainplates is that although the sides of the hull do slope and the forestay knees slope inward, the shroud chainplates are straight and more or less (except die to slot placement errors) rise vertically though the deck. So the forces imposed by the rig on the shroud chainplates are primarily vertical. The backstay chainplate on the other hand, is fabricated so that the top portion rises (slopes) forward after the last bolt hole. This in combination with the aft sloping installation on the knee creates a very powerful lever, and the forces imposed by the rig are both vertical and forward to a very significant extent. The forward slope and the length of the backstay between the top bolthole and the deck insures that the forward component of those forces will be very significant.
"3. Eliminate unneeded stress on the taffrail."
Yes it certainly would do that also, but I am not sure that the lateral force of the chainplate against the starboard side of the slot is a problem. It may be, but I have been more concerned with the longitudinal force exerted by the chainplate on the front edge of the slot. That is why I filed underside of the front edge of the slot to create more room for the chainplate to "work". A previous owner also must have tried this, because the slot already extends forward of the cover plate, leaving less taff rail before the fiberglass taffrail drops to the deck level.
"Are bigger bolts out of the question for your chainplate? I'd think "play" is a bad thing."
The boltholes were drilled to the correct size, but the correct size still allows play given the forces “at play”. This was also the case with the shroud chainplates. In other words, the next larger size bolt appears to be too big for the hole, and the next lower size drill bit appears to be too small for the current bolts.
Note to Ebb who wrote: "An upgrade would be to keep the theme going from the front end of the boat. Use some bronze plate. Just an opinion."
Yes I agree with you a complete set of silicon bronze chainplates would be a wondrous thing. I however after checking in with two riggers and three boat yards, elected to use #16 stainless for my shroud plates because,
1. They have it in stock, and I had a mast down waiting for completion of the chainplate project
2. Stainless steel is what the professionals are mostly using use these days, or so it appears at least locally.
3. #316 stainless is pretty good stuff
4.It appears to be less expensive than silicon bronze
5. As I recall both #316 and #304 are stronger than silicon bronze...but I haven't verified this recently with a reliable source, so don't rely on this statement.)
6. The bronze shroud chainplates and bolts that I removed were pretty much gone. So bronze ain't perfect. Of course, who knows what sort of bronze that was... and it was probably original (forty years old). Most of the bolt diameter had transformed to colloidal copper (like a red penny), and this was also the case with the plates. I didn’t cut the plates in half, but I could not strip through the copper. Some of the bronze bolts snapped in two when I was removing them. (See photos of these bolts elsewhere on this forum.)
I am still contemplating ordering new backstay chainplate not because my current one is damaged or corroded, but because my current #304 is a different alloy than the #316 bolts, washers and nuts, and therefore in the wet, salty environment of the lazarette locker, the system seems to shed a fair amount of rust as evidenced by the streaks leading downward from the chainplate, nuts and washers. Most of these streaks were actually coming from the #316 nuts and washers. The rust is unsightly and troublesome, even if pretty much hidden in the locker...and by the way the rust stopped above the splash zone. In other words there was little rust at or above the top hole, where the salt water from the well does not normally reach when under sail.
Yes, but think of the wonderful protection they offered as anodes for the backstay.... :rolleyes:Quote:
Originally Posted by Scott Galloway
:)
Scott,
Consider using silicon bronze bolts for the 316L plates.
Avoids stress corrosion that will occur even with 316 nuts and washers. imho
My guess is that you would tear the knee off the transom and tear a big hunk out of the transom before a chainplate assembly consisting of a 3/16 inch thick #304 chainplate and 3/8 inch bolts, locknuts and washers would fail. Now, it may pay to remove and inspect any chainplate periodically, but in four years of sailing there was no significant corrosion on my backstay chainplate, despite the stresses that it endures and the salty, wet environment in which most of it is housed. I finished cleaning the chainplate today, filed by epoxy lined bolt holes to fit 3/8 inch bolts with a round file, bought some new 3/8 inch bolts nuts and washers for good measure, slathered all of the above with Lanocoat, and put it all back together. There had been no deformation of the #304 stainless steel chainplate in four years of sailing, and almost no corrosion.
I did take my four-year old #304 stainless steel chainplate to the boatyard to get an estimate for a replacement chainplate to be made of 3/16 inch #316 stainless. After hearing the estimate, and conferring with the yard people, I decided to reinstall my #304 chainplate. The estimate for a new one made of #316 stainless was approximately $250.00, including material and labor. The yard concurred with me that the #304 chainplate that I already have was in good condition, and not in need of replacement, either now or in the foreseeable future. It would have been in their economic interest to tell me otherwise.
It would seem to me from what little I know about galvanic action on dissimilar metals that a #304 stainless chainplate and #316 stainless bolts would be more compatible than #304 stainless chainplates and silicon bronze bolts, or #316 stainless chainplates and silicon bronze bolts...or am I missing something here?
Of course in the best of all possible worlds we would be using silicon bronze plates and bolts or #16 plates and bolts.
Here is another question for you guys: If as C Amos says, depending on the metals we use, our backstay chainplates in the frequently saltwater-filled lazarette may be serving as “anodes for the backstay”, would it make sense to put a zinc on the backstay chainplate?
:eek: Holy mackerel! Mine cost about $100 and I thought that was expensive!Quote:
Originally Posted by Scott Galloway
Put any 300 series stainless together (304 with 316, for example) under compression/tension, you will get corrosion. It happens, it's not an opinion.
Larry Pardey. "A tip for those who get bleeding or rust marks running down their hull where stainless bolts go through stainless steel fittings - use a silicon bronze bolt or screw and there will be no electrolysis if the fitting is above the waterline. There will be no more bleeding and there will be no electrolysis if the fitting is above the waterline. In fact it is common practice to use bronze turnbuckles with stainless steel wire for rigging."
August 1999 on the 'Lin & Larry Pardey site.
In fact stainless parts are screwed into bronze bodies to prevent galling. Bronze screws would certainly stop the rusting if used in the 1/2 round rubrail on the A/C.
The shroudplates taken off 338 are in good condition despite being 40 years old. It's entirely possible different bronze plate was used over the years by Pearson. Entirely possible some bronze plate was in fact brass.
Thanks for the quote Ebb. That sure was interesting. I've never had any rusting screws in my rub rail though. I do trust the Linn and Larry Pardy’s judgment. I also like Dan Spurr as a reliable source of lots of information. Spurr’s Boat Book “Upgrading the Cruising Sailboat” is a nice thing to own. He features the restoration and modification of his Pearson Triton and also to a lesser degree of his Pearson Vanguard. The illustrations by Bruce Bingham are worth the cover price. Dan Spurr included a discussion of stainless steel options in the appendices, and a galvanic series table also, but I find that table to be a bit confusing.
In your quote, Larry Pardy referred to electrolysis, and we are talking primarily about galvanic action in the backstay chainplate are we not? …unless of course our electrical systems are grounded to our rigs? Mine isn't.
Galvanic action being that process that causes two dissimilar metals in contact with one another to exchange ions with the resulting effect of corrosion of one of the metals, and electrolysis being the loss of ions resulting from the flow of an electric current through metal from an external source. In either case, in an Ariel we would have the entire backstay, its fittings, the tangs, and mast etc. all connected together.
So in the case of electrolysis, if there is electricity flowing through the standing rig, and to the chainplates, I am still wondering about the advisability of a zinc on the backstay chainplate, given he fact that it spends so much of its time in salt water. In the case of galvanic action, a bronze or #304 stainless chainplate would be in contact with the #316 pin and shackle or toggle above, and cover plate above, and whatever fasteners you use to tie the chainplate to the knee. We need to look at this as an entire system do we not? So in the case of galvanic action, which is unrelated to an external current, don’t we still have a problem with the contact with the rig above and the backstay chainplate below?
Also, does anyone have any thoughts on printed sources with tables listing the relative nobility of metals and particularly bronze vs. stainless steel?
By the way, I paid about $50.00 for my #304 stainless steel backstay chainplate in 2002. That price covered materials and labor for fabrication. The plate was not polished. In four years there has been no significant corrosion to the bolts, or chainplate. However, there were rust streaks, and in a small area where the chainplate came into contact with the deck-mounted cover plate, a tiny spot of crevice corrosion was observable, so that means that corrosion is indeed happening. I imagine that if the #304 chainplate were completely isolated from all other metals, and just hanging in the lazarette by a Dacron line, it would also corrode to some degree, as would all metals eventually. When I replaced them in 2004, my bronze shroud chainplates with their bronze bolts, washers, and nuts were also badly corroded. Unless you have been the sole owner of your boat, there is no telling whether the chainplates on your boat have or have not been changed at some time in the past. My boat #330 was only eight boats in the Pearson production line ahead of Ebb's #338. So it is probable that the same order of bronze was cut for chainplates on both boats...but maybe not.
I think Ebb's concept of going with bronze is a good one if you have a reliable, reasonably-priced source of bronze chainplates, but stainless steel seems to work just fine.
My bronze shroud chainplates probably lasted for forty years, provided that a previous owner didn't replace them at some point. So who is to complain about bronze? Certainly not me? But frankly after seeing the degree to which the bronze bolts on my shroud chainplates were corroded as demonstrated in the photo below, I no longer believe that bronze is corrosion proof.
I am comfortable with #316 stainless steel shroud chainplates with #316 bolts, nuts and washer, and for now at last I am satisfied that a #304 stainless steel backstay chainplate has strength and will hold up over a reasonable period in the wet salty environment of the lazarette locker, with #316 fasteners.
I guess the moral here is whatever metal you decided to choose for chainplates and fasteners, it is wise to remove and inspect your chainplates periodically, and when you do remove a chainplate it would also be wise to replace your fasteners, even if they still do look spiffy. For the backstay chainplate, new 3/8 inch #316 stainless steel fasteners cost me $15.83. Removing all of your shroud chainplates at once is a daunting task. I have done it with the mast down of course, but you could pull and inspect the chainplates on a rotating schedule. For either bronze or stainless steel, that should probably be on a more regular schedule than once every forty years.
The photo below is of the bronze shroud chainplates and bolts that I removed in 2004. I replaced these with #316 polished stainless steel chainplates. Note the bright pencil-lead-thin core of remaining bronze in the bolts. The red stuff is copper toast. I did not saw through the chainplates to see what a cross section would look like, but I could not strip through the red layer. I still have the old bronze plates. So I could cut through one and take a photo of the cross section if anyone is interested.
Tha Galvanic Table refers to electric conductivity. It grades metal alloys from most cathodic (platinum) to most anodic (magnesium.) You will find the 300 series (passivated) cheek by jowl with silicon bronze. In an attempt to help designers putting metals together in certain 'environments' there is an anodic index which assigns voltage separations to alloys.
Offshore sailboats are considered in a 'harsh environment' ie seawater. 300 series passivated stainless steel is right next to silicon bronze in the anodic index, with a separation of no more than .15V. More than ,15V in a cloride soup will cause electrical corrosion to kick in. "Electrolysis" is maybe the wrong word but it's the right idea. [ Might assign the word observation to the Pardey quote rather than opinion.]
Check out >the corrosion doctors< on the net
Hmmm...The problem is that some galvanic series charts, or electrolytic tables (as some sources refer to them) show different relationships between the various metals and alloys, or at least it appears to me that they do.
For instance, one of my printed source books, a publication of the USCG Auxiliary, lists the most cathodic metals in that order as Mercury, Monel, nickel, and bronze (silicon) in that order, whereas stainlesss steel is way down on that list behind, copper, brass (red), bronze (aluminium), gun metal, brass (yellow), bronze (phosphor) and lead. Trailing stainless steel are iron, mild steel, aluminium , cadmium, galvanized iron and steel, zinc, and magnesium.
I don't have a copy of the 64th edition of Chapman, but I took a brief look at a similar table in that edition the other day, and I recall that it showed different relationships than the above, or at least it appeared to me that it did.
Then when I consulting Dan Spurr's “Upgrading the Cruising Sailboat” I was perplexed by the relationships shown in the "Galvanic Series of Metals in Seawater" table. If someone has that book, check out Appendix B and explain the table. It has two columns that appear to run from anodic or least noble to cathodic or most noble, in otherwords from magnesium on the anodic end to graphite (above platinium) on the cathodic end. Silicon bronze is listed once on that table, but (18-8 Stainless Steel, Type 304) and (18-8 3% Mo Stainless Steel Type 316) are listed twice, once as being more cathodic than silicon bronze and once as being more anodic.
At Ebb's suggestion, I consulted the "Corrosion Doctors website at: http://www.corrosion-doctors.org/Def...es_in_Seawater
In their "Galvanic Table", the Corrosion Dotors do indeed list passive 304 and passive 316 stainless steel right next to silicon bronze. Their source appears to be: the galvanic series of metals in sea water from Army Missile Command Report RS-TR-67-11, "Practical Galvanic Series."
So: That is a long list, but the relevant part of that list reads:
#70 Silicone Bronze 655
#71 Stainless steel 304 (passive)
#72 Stainless steel 301 (passive)
#73 Stainless steel 321 (passive)
#74 Stainless steel 201 (passive)
#75 Stainless steel 286 (passive)
#76 Stainless steel 316L (passive)
With the higher numbers like 304 stainless steel (passive) (#71) and Stainless steel 316L (passive) (#76) above being more cathodic than the lower numbers like silicon bronze (#70). So that would be a good thing if you were a piece of passive #316 stainless steel sitting next to a piece of silicon bronze, and not quite so good for the bronze.
But Stainless steel 304 (active) also appears on that list in position #40, some thirty places away from silicon bronze, (and thus much more anodic). Stainless steel 316 (active) appears in position #67, three places more anodic than silicon bronze. So that would be a bad thing if you were a piece of passive #316 stainless steel sitting next to a piece of silicon bronze, but a good thing for the bronze.
On that same web page and from a different source, the Corrosion Doctors provide a table titled "Galvanic Series in Seawater" about which they say,
"A galvanic series has been drawn up for metals and alloys in seawater, which shows their relative nobility. The series is based on corrosion potential measurements in seawater. The relative position of the materials can change in other environments. The further apart the materials are in this series, the higher the risk of galvanic corrosion."
The Corrosion Doctors are using "The Handbook of Corrosion Enginnering" by Pierre Roberge as a source.
This how that table reads:
Begin Quote from that source
"Most cathodic, noble, or resistant to corrosion
Platinum
Gold
Graphite
Titanium
Silver
æ Chlorimet 3
è Hastelloy C
æ 18-8 Mo stainless steel (passive)
ç 18-8 stainless steel (passive)
è Chromium steel >11 % Cr (passive)
æ Inconel (passive)
è Nickel (passive)
æ Silver solder
ç Monel
ç Bronzes
ç Copper
è Brasses
æ Chlorimet 2
è Hastelloy B
æ Inconel (active)
è Nickel (active)
Tin
Lead
Lead-tin solders
æ 18-8 Mo stainless steel (active)
è 18-8 stainless steel (active)
Ni-resist
Chromium steel >11 % Cr (active)
æ Cast iron
è Steel or iron
2024 aluminum
Cadmium
Commercially pure aluminium
Zinc
Magnesium and its alloys
Most anodic or easy to corrode"
End Quote from that source
In this list you also see stainless showing up twice with active stainless steel scoring worse than silicon bronze and passive stainless steel scoring better in the degree of nobility or cathodity.
So does the key to understanding the relationship between silicon bronze and stainless steel in these charts depend on the definition of the words "active" and "passive" related to 304 and 316 stainless steel?
I was feeling much too passive to look this definition up for myself, so I asked my chainplate, but it didn't answer. Does that mean that it is passive?
Anyone know the definition?
Passivation is about steel alloys. The ones that concern us are the 18-8 or 18% chromium 300 series stainless steels. Metalurgy is still close to the alchemical experiments of the middle ages. imco. Like turning lead into gold, stainless steel is an attempt to turn iron into bronze. Alloys and methods are always being tweeked - and I just know I will never GET IT! Either my beard or my white coat are too short.
There are various 'galvanic' lists from different sources generally agreeing BUT also showing important differing placements around iron alloys. I think we should gather our intelligence from sources specific to bluewater. {How come we take greenwater over the bow???}
Passivating stainless steel involves soaking fabricated pieces (usually) in acids at certain temperatures that remove minute carbon machining and milling debris from surfaces. Dilute and very toxic nitric acid is used - followed by equally nasty dilute alkaline baths - otherwise the acid would keep eating the steel. Followed by much plain water to neutralize both. Environmental laws hamper the process. Some manufacturers use citric acid (lemon juice?) to avoid the heavy duty chemicals. But this has not been entirely succesful. It means that there could be 316 passivated on your ship that will flash rust. Nice, huh?
Passivation is also selfcreated by stainless steels (and metals in general). It is a chromium oxide film so thin it can't be seen that forms in the presence of oxygen. A warehouse can destroy the passivation by dragging a sheet over another.
The industrial passivation process is evidently an attempt to perfectly clean the surface so that the selfcreated film is perfect. There's a lot of buffing and electro-polishing goin on around here. That's why you don't want to ever scratch or even clean stainless with scrubs and solvents and scotchbrite pads, etc. Even so, it can in the presence of oxygen repair itself, but has to have that airy opportunity.
What is peculiar to me is that soaking a metal in acid can radically change its position on the anodic index. That's alchemical to me. There is a problem with the help too - eg, I ran into a professor who was saying you coat dissimilar metals with siomething to keep them separate, you know like rubber - but WE all know full well that you need air for the passivation process to work right on our stainlesses. Who is the ultimate authority remains to be revealed. It's obvious steel alloys are a bit unstable - even hysterical. This country boy wants good ole uncomplicated silicon bronze ever time! :D
Thanks for the book report on passivity, Ebb. I am feeling much less passive now... but much more in favor of passivity than I ever was.
Well actually, as I understand the tables above, the passive 18-8 stainless steel in either #304 or #316 stainless would be more cathodic than silicon bronze. Their evil twins over on the active side of the stainless family would be more anodic. So it would appear that passive 18-8 steel ain't a bad choice. Now the question is how does one know whether the stainless one purchases for ones boat is passive or active?
The components of this discussion that are missing, or underrepresented here are relative strength of the materials, cost, and availability. So here are five more thoughts about the virtues of bronze and steel respectively from one who is unschooled in metallurgy:
1. The prime reason given to me by certain riggers and other marine professionals for using #304 stainless over #316 stainless is that #304 is stronger than #316.
2. The prime reason given to me by certain riggers and other marine professionals for using #316 stainless over #304 stainless is that #316 is less subject to corrosion. I chose #316 for the shroud chainplates and stayed with #304 for the backstay.
3. The prime reason given to me by certain riggers and other marine professionals for using either #304 stainless or #316 stainless over bronze is that stainless steel is stronger than bronze.
4. The prime reasons that I went with stainless steel on all of my chainplates are:
a. The professionals told me that steel was stronger than bronze, and the literature that I have read backs this up. (Yes I know, if it corrodes then it isn’t as strong as it used to be, but you need to do preventive maintenance on any system on your boat, whether mechanical or structural.)
b. The bronze shroud chainplates and their fasteners on my boat were badly corroded, so no metal is impervious to corrosion. (see earlier photo)
c. None of the above sources even carried bronze stock suitable for making my chainplates, and I would have had to pay for an entire sheet of bronze, although I needed only part of that sheet, since the above sources had virtually no market for bronze stock. The yards and other suppliers to whom I spoke simply aren’t making bronze chainplates anymore except by special order. So price and time to complete the order were certainly factors in my decision.
5. Despite all of the above, them bronze cannons on them ol' Spanish galleons shine up pretty nice after being in the bottom of the ocean for a few centuries. Stainless steel would not fare so well. So it all depends on your application, your intended use, and whether you intend to remove and inspect your hardware from time to time. All the stuff that goes below water on my boat is bronze, and all the stuff that stays above water is stainless. Of course my backstay chainplate can't make up its mind whether it is above or below water.
I really do think that either choice (stainless or bronze) for chainplate stock is acceptable. A sound maintenance schedule is prudent in either case.
Time to go sailing!
Quote:
Originally Posted by ebb
Found a picture. Nice. A-226 Aft ChainplateQuote:
Originally Posted by c_amos
Uh, don't see it . . . :confused:Quote:
Originally Posted by mbd
Bill, I think what what we see in the photo posted by MDB is the tops of two separate chainplates protruding thorugh two separate slots in the taffrail separated from one another by a distance equal to the width of the knee, with a single coverplate with two matching slots set down on top of those two chainplates. The turnbuckle is attached to a pin run between the two chainplates.
If that is not what we are seeing, then whatever we are seeing looks like what we might see if we were looking at an installation similar to the double chainplate installation described above.
Ok, guess I was looking for a couple of "seperate" chainplates . . . such as are on one of the Bay Area boats (which is temporarily "lost"). We may soon have the backstay chainplate setup suggested by Ebb. Photos will follow.Quote:
Originally Posted by Scott Galloway
Sorry,Quote:
Originally Posted by Scott Galloway
Not sure how I missed this discussion of the twin chainplates aboard 'Faith', I must have not been paying attention.
THis mod was done by Herb Tucker, prior to my purchasing the boat.
Hope these pictures make it a little more clear (did not have a good one).
http://sailfar.net/gallery/albums/us...aithStern1.jpg
http://sailfar.net/gallery/albums/us.../Chanplate.jpg
There are twin chainplates, bolted to either side of the knee. That was not enough, there are two angled pieces of stainless that attach to the middle hole on either side and then are throughbolted to the transom with 4 5/16" bolts (in case the knee should fail). Pretty solid set up.
Even so, I had spoken to a rigger about going with a dual backstay....
Commnader Pete posted this;
This link makes sense to me, and I think I will stick with what I have.Quote:
Here is the Port Townsend denunciation of double backstays.
http://briontoss.com/education/archive/miscapr99.htm
.......