Chainplate discussion; type material, repair,,,

[CapnK]

Soon I'll be installing external chainplates, getting away from the original thru-deck installation (yay).

Anyone have suggestions on a source, for either pre-made plates, or flat bar stock so I could make them myself?

Post-posting this, I'm off to wander through the virtual aisles of McMasters-Carr. :)

I've seen the Schaefers sold by many online outlets, was just wondering who else might be/have a good alternative...

[CapnK]

This place has the best prices for bar stock that I've seen:

OnlineMetals.com

Buy a length for $8-17, cut it to length (if needed), drill 5-6 holes in it, and bend the top slightly (take it to a local machine shop for this?), and presto - you have a chainplate that retails for more than 4X the cost of the raw material...

Seems to be the thing to do!

[CharlieJ]

I've dealt with Online several times - good people, good prices

[CapnK]

That's good to know, CJ - Thanks!* :)






*(or "hanks", as I originally typo'ed it, relevantly, it would seem...  ;D :D )

[AdriftAtSea]

Capn K-

Make sure you get at least 316L stainless steel.  The L stands for low carbon content, which is a bit better for marine use.  The 304, which is much more common, has serious problems with chloride stress cracking in  a marine environment.   Nitronic 50 would be an excellent choice, but is a bit more costly, if you can get it. :D

[Fortis]

I would actually disagree witht he 316L...The chainplates are going to be around 6mm and have no welding or major heating done to them...thus overhardening because of the carbon is not an issue. Plain 316 will do fine.

Have you got the internal ribs to support the external chainplates? If not, or in doubt...then a strip of 316 in 2mm or so on the INSIDE to act as a very long washer and sandwitch the rib or hull in between is much better then using individual round washers. A peice of marine ply in between is added by some people as a "pad" that can absorb inperfections of shape.

Don't forget to buy bolts and nuts that are the same type of stainless as your chainplate material. A good reason to go with 316 instead of 316L...The steel is almost the same price if you can find it...but 316L nuts and bolts are about 8 times the price of regular ones....At least on this side of the pond.

Other characteristics to consider is that the 316 has a somewhat higher tensile strength then 316L...in exactly the "pull" direction that chainplates are subjected to.

If you sail in warm waters, consider the rarer but nifty 317 or 317L stainless...This is designed for imporved corrosion resistence in a chlorine environment (warm seawater). It is annoyingly hard to find...but has the same strength and welding characteristics as 316 when you do mange to get hold of it.

As a last word, get the highly polished version and not the 300grit. It will cost more, but you will have less crevice and pock corrosion. You can get buffing wheels that fit small angle grinders, I would suggest giving the plates a nice polished finish after the holes are drilled and before they go on the boat...


Sasha

[Captain Smollett]

Kurt,

FWIW, I'll add my endorsement of onlinemetals.  I've ordered from them and have had good service.  They were about the only source I could find of some aluminum round tubing I needed, and they cut to length (or 1 ft increments or some such).  Good prices, too.

JR

[CapnK]

316 sounds like the ticket, though I wonder why Schaefer et al use 304...? (Price?)

Seems like most bolts and such are 316, as well.

The original chainplates mounted via thru-bolts to knees glassed to the hull. I'll be glassing (on the inside of the hull) horizontal members that span the chainplate area which will act as the backing plates, tying all the chainplates into a 'web' of sorts.

Ever seen how Island Packet does their chainplates? They use a horizontal bar that tucks up into the toerail, the bar has 3 tangs that fit up through slots in the deck. The chainplate itself is bonded to the hull, and then there are large loops of glass rope that go over each tang, and are extended down along the hull interior 2-3 feet, spread out flat to 6-8" wide at their bottom end. Very tough, nice load spreading.

[Fortis]

304 is a very little more then half the price of 316 and is still sold a lot in marine apllications because many older boats use 304 as their entire stainless component. If you wish to bolt somethingonto a piece that is 304...it is better if it is 304 too. And of course, some poeple just like to keep it simple by only having one form of stainless on board to worry about (means not having to keep two types of screws and bolts).

Most bolts are NOT 316...they are whatever you ask for, so make sure you ask for the right thing or you will get corrossion form dis-similar metals in a salt environment.

I have not seen the island Packet system you mention...we do not get them out here, and all I know about them is that their rudders are as deep as their keels, so they snap them off in a grounding quicker then other boats. I have to say that based on your description I am not a huge fan of the system you lay out. From my perspective it leaves a lot to be desired in terms of inspection, servicing and allowing the steel to breathe free. It actually sounds a bit like a factory short-cut to get the same amount of strength as by doing it "properly", but for less money by saving time and such.

I could be entirely wrong or have totally mis-visualised what you were trying to describe to me.

I can tell you that there are more BAD ways of installing chainplates then I ever thought possible before I started working on other people's boats. My favourite for "what were they thinking?" design is on one brand of boat which uses a steel frame that allowed them to move the proto-boat around the workshop, it then got more or less glassed in to the hull proper and was a sort of all-round stringer system that also became the framework for the bunks and settees...A few boats are made this way...But this brand then attached its chainplates by taking a 3/8 bit of bar-stock, bending it into a loop around this GALV STEEL frame and tack welding it back on itself, and then having the long end come up through the deck where it had a thread cut into it. The terminal, or top, of the chainplate was then SCREWED ON to this stubb????!!!???

Forty years after the first boat rolled off the rpoduction line, and with a fleet of around 600...All the ones that were not replaced due to having sane owners or insurance claims or whatever are all starting to fail within about a three to five year period.

If I was working for an Insurance company I would just suspend issuing policies to this brand for the next few years so that we would nto HAVE TO pay the literally inevitable cost of rig replacement...

Oh well...I am sure your system will be far better than that one!

Alex.

[s/v Faith]

Soon I'll be installing external chainplates, getting away from the original thru-deck installation (yay).

Anyone have suggestions on a source, for either pre-made plates, or flat bar stock so I could make them myself?...

  If you decide to have them fabricated, let me know if the unit cost for 12 is less then for 6.  I would like to do this as well.  (I have re-caluked my through deck plates a few times... they are the first things to leak.).

  Let me know what you find.

[Fortis]

I am not sure what "fabrication cost" you are seriously looking at.

You buy the flat bar in the correct width and thickness for what you want.
the place you buy it will cut it to length for a small number of dollars.

All you need after that is a drill press and two sharp drill bits (an oil bottle also helps).

You can get a 1-2HP drill press nowadays for less then $60 on ebay.

Just buy the bright polished flat stock to begin with.



Alex.

[psyche]

My original chainplates on my Columbia 8.7 were a special aircraft aluminum. When I refit my boat I replaced all the chainplates with stainless flatbar which I had a friend who had a machine shop make. I had them made  a bit longer to add a few additional holes to extend them further down the bulkheads where they were attached. We cut the holes through the deck a bit larger and filled with epoxy to prevent any intrusion of water into the core. After installing and sealing I have had no leaks in 3 years. Dan

[Gerald A. Gotts]

I'm new here.  Actually I'm new to the forum idea.  I have a 1968 Bristol 24 that was given to me.  [ I know, no such thing as a free boat,right?]  I'm finding that out.  I've been told that the  badly rotted wood on the starboard side of my cabin has to do with a chainplate and it is a pretty important piece of equipment.  My question is: can I just use something like "git rot" or do I need to drop the mast etc.  The boat is at anchor right now.  The plywood is in pretty bad shape.  As you can probably tell I am new to sailing as well. 
     I will have more questions in the near future.  Thanks !!!

[AdriftAtSea]

GIT ROT is not a proper repair to this type of damage. 

Is the chainplate attached to the cabin bulkhead?? If so, scarfing in a good piece and then re-attaching the chainplate is a possibility.  Replacing the bulkhead would be a better idea IMHO, since it would be a much stronger repair.

You may not have to drop the mast, since you can run a halyard to the starboard toe rail to support the mast while you're repairing the bulkhead.  However, you shouldn't be sailing the boat until this problem is thoroughly and completely repaired.

[Gerald A. Gotts]

Thanks Adrift..  Yes it is attached to the bulkhead.  Due to some really beautiful handcarving on the bulkhead I don't want to replace it but I will tear it out and somehow strengthen it by adding support and perhaps some thickness to the  mahogany bulkhead.  I have not sailed her yet as  it came sailless.  I won't be sailing her  until all repairs are done  and done well.  I thank you very much for the almost instant response. Jerry

[AdriftAtSea]

If you're committed to keeping the existing bulkhead, and I can understand why you would be given your description of it, I would recommend you scarf in a repair and then sister an additional layer of plywood to one side of the bulkhead over the repaired area.

Also, make sure you repair any leaks in the area.  The leaks are what caused the bulkhead to rot...and fixing them is a necessity in the long-run.

Good luck and I'd love to see photos when you can post some.

[Gerald A. Gotts]

Thanks once again Adrift.  I will get some photos on here as soon as I can.  I had thought that perhaps adding some plywood might strengthen the bulkhead.  I'm also wondering if replacing the chainplates is  required as well.  They appear to be in pretty good shape.  I am nearly ready to start the work right after I replace the entire rub rail.  By the way I read somewhere [ maybe on this forum] that there was an artificial wood called "nexwood" [I think].  It showed how you could cut this and bend it around to fit the shapes needed.  Ever hear of it ?  I am working on a very strict retirees budget.

[AdriftAtSea]

As for the chainplates, the area to inspect most closely is that area that was covered by the deck.  This area is often subject to crevice corrosion effects, due to being surrounded by wood. Never heard of nexwood, but I wouldn't use any artificial wood that is soft enough to bend for an area subjected to the stresses and loads that chainplates are.

[Shipscarver]

The 1968 Bristol was built like a Sherman Tank. But, be sure you are not getting leakage at the joint. And, be sure to check around the holes on the chainplate for tiny cracks or bends. If they are there you are better off replacing and resetting the chainplates.

[okawbow]

Hey Gerald,

I sail a 1976 Bristol 24. If I can help in any way; let me know.

The chain plates are under a lot of stress, and should be well secured. If you have problems with the bulkhead that they are presently bolted to; I would suggest overlaying new, marine plywood on the opposite 1 foot or more of the bulkhead. The chainplates could then be re-bolted, using backing plates, or at least, fender washers, to the re-inforced bulkhead.

My bulkhead was replaced with new mahogany plywood, and glassed to the hull sides, in the area the chainplates attach.

Some Bristol 24 owners have installed new chainplates to the hull it'self, similar to a Pacific Seacraft 24, and even added an extra lower stay for offshore sailing.

While you're at it; check the "strongback" arch over the main bulkhead for stress cracks that indicate the wood beam inside is bad. I re-inforced mine with two solid mahogany boards, cut to fit the arch. I glued them on with 3m 5200, and through bolted them to the archway with stainless carriage bolts, nuts, and washers. It looks real nice, and adds lots of strength. My stays have remained tight for 1200 or so miles of sailing, this spring. I carry a full main and a 150 genoa in up to 25 mph wind while racing. The rig gets lots of stress, but shows no weakness now. However; sometimes water shoots up through the cockpit drain during gusts. (: