Can anyone give me an idea where a person can get replacement chainplates for my Hunter that won't kill me in the pocket?
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Do you have one of the originals? Take it to a sheet-metal guy and have him use it as a pattern to make some up for you. They should be 316 stainless. Don't change the thickness, width, or depth of 'meat' round the mounting and clevis holes or you might as well redesign the whole rig. If the sheet-metal guy just says, 'Oh, they're just 5/16 stainless' without seeming to know or care about what KIND they are, turn round and go right to the next shop. If they are not 316, you might as well use cold-rolled steel. Type 303 is for speedboat stuff (Perko deck vents). Type 304 is for stanchions and railings, NOT for rigging fittings, which are always 316 (and use 18-8 pins). JC 2
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Doug T.
304 vs. 316
I'm curious why 316 is so vital. I know it is more resistant to corrosion, but isn't it also weaker than 304? Are there other attributes of 316 that make it important for use in chainplates? Are there other places where 316 "must" be used??
I'm curious why 316 is so vital. I know it is more resistant to corrosion, but isn't it also weaker than 304? Are there other attributes of 316 that make it important for use in chainplates? Are there other places where 316 "must" be used??
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Tom Hadoulias
316 is...
less suseptable to crevace corrossion than 304SS and chainplates are very prone to this anomaly due to the extreme stress they see and constant exposure to water. I had one cracked chainplate on my 37C, the starboard upper was cracked below deck at the top bolt hole location. The angle of this chainplate is not in line with the pull of the upper shrouds causing a bending moment at the top bolt hole as that is the last support before the deck plate. The deck plate will lossen over time with hard sailing causing some leaks and more stress on the chainplate at the top bolt hole. Mine never failed, although I have a friend with a 84 37C that had the same chainplate fail under extreme conditions on a Bahamas crossing. He was fortunate and responded quickly and thanks to a very strong rig and running backstays in place he altered tack and secured the upper to the toerail where he was able to sail on and effect repairs later. I personally have replaced all of my chainplates. I took the thickness of the existing chainplate plus the added thickness of the doublers on the ends for a final thickness of 5/16". I purchased 316SS barstock and cut each chainplate to match the existing length and match drilled the holes as well. I rounded the end radius of the existing plates being carefull not to overheat and de-temper the metal. I polished each using a grinder and sucessively finer emory cloth to a mirror finish. I had to do a lot of enlargement on the deck holes to accomodate the new thicker replacements, but as a result everything ends up at the same spot except the rigging attach points move forward the amount of extra thickness of the chainplate over the stock units, about 1/8". This has not caused any problems in rigging and really is un-noticeable and the ultimate gain in strength is about 50% over the stock units. I also replaced my standing rigging and up-sized to 9/32" from 1/4" with all Sta-Loc terminal ends. I sleep much better as a result! At the very least, check those chainplates often for cracks, especially the uppers. They can be removed and checked by a competent metal lab for cracks at a nominal cost and while your at it, dry out and epoxy the deck access holes as they will almost surely leak at some point and can rot out your deck if left unattended. Tom Hadoulias S/V Lite Chop
less suseptable to crevace corrossion than 304SS and chainplates are very prone to this anomaly due to the extreme stress they see and constant exposure to water. I had one cracked chainplate on my 37C, the starboard upper was cracked below deck at the top bolt hole location. The angle of this chainplate is not in line with the pull of the upper shrouds causing a bending moment at the top bolt hole as that is the last support before the deck plate. The deck plate will lossen over time with hard sailing causing some leaks and more stress on the chainplate at the top bolt hole. Mine never failed, although I have a friend with a 84 37C that had the same chainplate fail under extreme conditions on a Bahamas crossing. He was fortunate and responded quickly and thanks to a very strong rig and running backstays in place he altered tack and secured the upper to the toerail where he was able to sail on and effect repairs later. I personally have replaced all of my chainplates. I took the thickness of the existing chainplate plus the added thickness of the doublers on the ends for a final thickness of 5/16". I purchased 316SS barstock and cut each chainplate to match the existing length and match drilled the holes as well. I rounded the end radius of the existing plates being carefull not to overheat and de-temper the metal. I polished each using a grinder and sucessively finer emory cloth to a mirror finish. I had to do a lot of enlargement on the deck holes to accomodate the new thicker replacements, but as a result everything ends up at the same spot except the rigging attach points move forward the amount of extra thickness of the chainplate over the stock units, about 1/8". This has not caused any problems in rigging and really is un-noticeable and the ultimate gain in strength is about 50% over the stock units. I also replaced my standing rigging and up-sized to 9/32" from 1/4" with all Sta-Loc terminal ends. I sleep much better as a result! At the very least, check those chainplates often for cracks, especially the uppers. They can be removed and checked by a competent metal lab for cracks at a nominal cost and while your at it, dry out and epoxy the deck access holes as they will almost surely leak at some point and can rot out your deck if left unattended. Tom Hadoulias S/V Lite Chop
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Gene Gruender
replaced mine, too
I also replaced my chainplates. Like Tom, I went to thicker ones, 3/8". I had 3 develop cracks at the top bolt. They really aren't hard to make, I did mine with a cordless drill on the back bumper of my rv. I'm sure there are many places to buy the stock, but if you can't find it locally (and I couldn't in Austin, Tx, a town of half a million) you can get it through www.onlinemetals.com. If you haven't checked them, I'd stongly recommend you peel back the carpet, remove the top bolt and look closely. Use some scotch brite to polish them up and the cracks, if any, will show up. Good luck, Gene Gruender Rainbow Chaser
I also replaced my chainplates. Like Tom, I went to thicker ones, 3/8". I had 3 develop cracks at the top bolt. They really aren't hard to make, I did mine with a cordless drill on the back bumper of my rv. I'm sure there are many places to buy the stock, but if you can't find it locally (and I couldn't in Austin, Tx, a town of half a million) you can get it through www.onlinemetals.com. If you haven't checked them, I'd stongly recommend you peel back the carpet, remove the top bolt and look closely. Use some scotch brite to polish them up and the cracks, if any, will show up. Good luck, Gene Gruender Rainbow Chaser
J
JC 2
Type 316
Tom H seems to know what he's talking about; but I think I would not change the thickness no matter what. My dad was a great lover of flying and designed several dozen small lightweight airplanes and seaplanes that most people have never known about. I was at the drawing board one day as he was calculating rigging specifications for a particularly nifty little biplane and I asked him how he knew what size of everything to use. He responded with the idea that it is all in scale-- the wire, the pins, the rods of the turnbuckles, the amount of 'meat' round the holes in the chainplates (which is half as much on an airplane as it is on a boat), the thickness of the chainplate stock-- EVERYTHING is in proportion to everything else. I have the formulae all here and could calculate it; but growing up with this stuff as I have I know it's easy enough to just rely on what The Master specified. The strength 'fault' with type 316 SS is that it tends to be brittle. The worst sort of fatigue you can put this stuff through is constant loading and unloading in tension-- which is why your mainsheet line wears out so quickly. My brother the aircraft designer says that the best thing is to CORRECTLY tune the rig once and only maintain it as needed (which should not be too much if you have got it right first), and in this way the whole thing will be under constant tension all the time. This will alleviate most of the potential for 'shocking' (best way to put it) the rigging with constant changes in load, which is where the 316 will get accused of being 'weaker' than 304. But yes, the short answer is that the corrosion resistence of 304 makes it undesirable for anything that important on a sailboat. The higher the number the harder the stainless-- but there is a positive correllation among corrosion resistence, hardness, and brittleness. JC 2
Tom H seems to know what he's talking about; but I think I would not change the thickness no matter what. My dad was a great lover of flying and designed several dozen small lightweight airplanes and seaplanes that most people have never known about. I was at the drawing board one day as he was calculating rigging specifications for a particularly nifty little biplane and I asked him how he knew what size of everything to use. He responded with the idea that it is all in scale-- the wire, the pins, the rods of the turnbuckles, the amount of 'meat' round the holes in the chainplates (which is half as much on an airplane as it is on a boat), the thickness of the chainplate stock-- EVERYTHING is in proportion to everything else. I have the formulae all here and could calculate it; but growing up with this stuff as I have I know it's easy enough to just rely on what The Master specified. The strength 'fault' with type 316 SS is that it tends to be brittle. The worst sort of fatigue you can put this stuff through is constant loading and unloading in tension-- which is why your mainsheet line wears out so quickly. My brother the aircraft designer says that the best thing is to CORRECTLY tune the rig once and only maintain it as needed (which should not be too much if you have got it right first), and in this way the whole thing will be under constant tension all the time. This will alleviate most of the potential for 'shocking' (best way to put it) the rigging with constant changes in load, which is where the 316 will get accused of being 'weaker' than 304. But yes, the short answer is that the corrosion resistence of 304 makes it undesirable for anything that important on a sailboat. The higher the number the harder the stainless-- but there is a positive correllation among corrosion resistence, hardness, and brittleness. JC 2
J
Jim Ory
chain plates
Thanks guys for the info. You all seem to be going in the same direction. There fore I am going to get some 316 in San Antonio and do the job shortly. I believe I am going to stay with the original design though. The extra tid bits of info will help me do a quality job. Thanks again....OrysGlory 3
Thanks guys for the info. You all seem to be going in the same direction. There fore I am going to get some 316 in San Antonio and do the job shortly. I believe I am going to stay with the original design though. The extra tid bits of info will help me do a quality job. Thanks again....OrysGlory 3
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