A few quick questions about chainplates

[cyrano138]

I am thinking about switching all the shroud attachments (on deck) on my Cal 20. It has three sets, two uppers and one lower (or maybe vice versa but in any case three altogether), all of which attach to the deck via padeyes.

I would like to attach them to chainplates bolted through the hull, and I will use sizing recommendations in Vigor's "Seaworthy Offshore Sailboat" although I don't know yet what size I will need exactly.

What is the general method for sourcing chainplates? Do people typically buy bar stock and drill it themselves? What materials do they use? I would think stainless, but there's 316, 304, and maybe others I don't know about. How do you get the right bend? How do you bend them?

Or, do folks generally just buy them premade? If so, is there an economical source for quality chainplates? I looked at a few sites and they seemed to be somewhere in the neighborhood of 80/ea, meaning my project would be a $500 project right out of the box.

Thanks for any help or insight you all can provide. My apologies as I'm sure this has been asked before -- my search didn't turn up anything quite as specific as I hoped to find.

[cal40john]

Maybe talk to this guy - Seal's Spars and Rigging

From - Untitled Document

"Other weak areas are the headstay fitting and the aft lower chainplates. These chainplates are only supported by the deck of the boat and though the design is sound, tend to weaken with years of racing. Both problem areas are relatively easy to fix or reinforce. The headstay can be attached to a stainless steel strap or tang, fastened directly to the hull of the boat, at the bow. The aft lower chainplates can be supported from below decks inside the boat with the addition of custom chainplates and turnbuckles (I have kits for both of these areas that can be easily installed)."

[cyrano138]

Originally Posted by cal40john

Maybe talk to this guy - Seal's Spars and Rigging

From - Untitled Document

"Other weak areas are the headstay fitting and the aft lower chainplates. These chainplates are only supported by the deck of the boat and though the design is sound, tend to weaken with years of racing. Both problem areas are relatively easy to fix or reinforce. The headstay can be attached to a stainless steel strap or tang, fastened directly to the hull of the boat, at the bow. The aft lower chainplates can be supported from below decks inside the boat with the addition of custom chainplates and turnbuckles (I have kits for both of these areas that can be easily installed)."

Thanks for the response!

I've spoken to Steve a few times, and had purchased a chainplate from him for the headstay, which is why I'm focusing on the other shroud attachments for now (I can do the headstay later). I want to size up all of the rigging eventually, though, and so it seems prudent to size up all the chainplates eventually.

The kits for reinforcing the upper and lower shrouds are basically a padeye mounted to the bottom of the deck beneath the ones on top (same bolts, holes), that then attach to chainplates mounted to the inside of the hull via turnbuckles. I figure if I'm going to go through all that and still end up mounting chainplates to the hull, it seems like a better idea to just use one chainplate on the exterior hull and get the hardware off the deck for good. Then, I don't have to worry about bedding the deck hardware and possibly rebedding it down the road, checking for rot (it's a cored deck), backing plates, etc.

For an extra bit of trouble and expense at this stage, I think the strength and ease of inspection, diminished risk of deck rot, etc. that I would get from exterior chainplates seem like a good idea.

Also, after doing a bit of research it seems like aluminum bronze is the material to use. Please correct me if I'm wrong.

[cal40john]

What is your goal? To cross oceans?

Did Seal recommend all these upgrades? Seems he races in San Francisco which is pretty hard on boats.

Adding weight aloft degrades performance.

I can't find my copy at the moment, but have you looked at Black Feathers? I think I recall that he went over the modifications for doing the SHTP

https://www.amazon.com/Black-Feather.../dp/1440191964

[stormalong]

IMO backing up the padeyes would be better than adding chainplates. Reason: maintain water tight integrity - chainplate cutouts through the deck will move under load. It is difficult to keep them watertight. By adding padeyes or brackets under the deck you still have watertight integrity.

Brackets would be just as good as padeyes and turnbuckles for reinforcement. First glass in some knees under the padeyes. Then attach a L shaped straps (brackets) to the bottom of the padeyes. Then drill through the knees and bolt the brackets to the knees.

For a 20 footer the straps would not need to be very heavy.

If you are going to cut slots in the deck for chainplates be sure to cut out the core around the slots and fill with thickened epoxy.

[cyrano138]

Originally Posted by cal40john

What is your goal? To cross oceans?

Did Seal recommend all these upgrades? Seems he races in San Francisco which is pretty hard on boats.

Adding weight aloft degrades performance.

I can't find my copy at the moment, but have you looked at Black Feathers? I think I recall that he went over the modifications for doing the SHTP

https://www.amazon.com/Black-Feather.../dp/1440191964

I guess I'd like the option to go offshore at least a bit.

Your point about water-tightness is well taken. I think I'd still consider it a fair trade for getting some hardware out of the cored deck and being able to seal that up for good. Mr. Seal didn't recommend going up a size, but I have to replace it anyway and I figured there's no harm.

Definitely not interested in racing it. It wouldn't be class legal anyway as someone's glassed over the inboard engine well.

Originally Posted by stormalong

IMO backing up the padeyes would be better than adding chainplates. Reason: maintain water tight integrity - chainplate cutouts through the deck will move under load. It is difficult to keep them watertight. By adding padeyes or brackets under the deck you still have watertight integrity.

Brackets would be just as good as padeyes and turnbuckles for reinforcement. First glass in some knees under the padeyes. Then attach a L shaped straps (brackets) to the bottom of the padeyes. Then drill through the knees and bolt the brackets to the knees.

For a 20 footer the straps would not need to be very heavy.

If you are going to cut slots in the deck for chainplates be sure to cut out the core around the slots and fill with thickened epoxy.

Do you have any references I could use to see what the knees look like?

Also, the chainplates would be on the outside of the hull, not through the deck.

[stormalong]

Originally Posted by cyrano138

Do you have any references I could use to see what the knees look like?

Also, the chainplates would be on the outside of the hull, not through the deck.

A knee is an approximately triangular piece that is perpendicular to the hull and deck. In a fiberglass boat it in usually cut from plywood and glassed to the hull and deck. It is a way to spread the load along a portion of the hull and deck.

I am not familiar with a Cal 20 but to move the chainplates outboard will change the angles of the shrouds and limit how close you can trim your jib.

Also, do you really want to poke bolt holes in your hull, how strong (thick) is the hull and will you need to reinforce it to take the stress of the rig being applied to it.

The Cal 20 is a 1960's boat. It has a lot of history. Apparently the present attachment scheme has worked for about 60 years. Doesn't it make more sense to strengthen the already proven attachment points than to abandon them and start over?

[thomm225]

Originally Posted by cyrano138

Do you have any references I could use to see what the knees look like?

Also, the chainplates would be on the outside of the hull, not through the deck.

Older boats like my Bristol 27 have fiberglass knees.

I have two on each side and the third shroud is bolted to the main maybe 2 inch bulkhead.

Like was mention above I wouldn't reengineer a Cal 20 just maybe beef up the existing setup or just be sure it's all in good shape.

A Cal 20 Black Feathers did the 2100 mile Single Hand Tranpac Race from San Francisco to Hawaii back in the day so you might want to research that boat.

That race though is usually a nice broad reach run all the way

Even beefed up a bit you are going to take a beating in a Cal 20 on certain days.

I got pretty beatup in my boat, a Bristol 27, the last two days sailing up and down the Lower Chesapeake Bay and it weighs in at 3X the weight of a Cal 20 and about 2' more waterline plus deeper draft.

Example Cal 20 ballast is 900 lbs. Bristol 27 ballast 2575 lbs

https://www.sfbaysss.org/archive-sht..._feathers.html

https://www.amazon.com/Black-Feather.../dp/1440191964

Pearson 10M chainplate / knee upgrade.

http://dan.pfeiffer.net/10m/chainplates.htm

[Benz]

The best material for chainplates is silicon bronze, aluminum bronze is a close second. You can put in bends by clamping the strap in a vise and levering hard on it: I bent 3/8" bronze bar stock this way.
Unlike some others above, I approve of moving the chainplates out to the hull; just be sure you have good structure where they go.

[Wotname]

You can have a read of this long thread - lots of opinions about the best chainplate materials on the last few pages. Jury is divided between bronze (silicon bronze and Ti).

https://www.cruisersforum.com/forums...me-269241.html

It really depends on how long you want them to last and how easy is it to remove and inspect for crevice corrosion. If you plan a DIY job and they are easy enough to access and replace every (say) 10 - 15 years, just make them from common SS316 and polish well. If you want longer lasting ones or if they are inaccessible, go for more longer lasting materials - bronze, Ti, more exotic SS etc.

Back in the day, galvanised steel was the way to go and regal as needed.

[TrentePieds]

Cyrano said: "I am thinking about switching all the shroud attachments (on deck) on my Cal 20. It has three sets, two uppers and one lower (or maybe vice versa but in any case three altogether), all of which attach to the deck via padeyes."

Why would you bother for a Cal20??

Lovely little boat in many ways, but after all she is no more than a dinghy with a deck. Sez I, having taught some hundreds of people the basics using Cal20s half a century ago.

Your existing pad eyes are perfectly fine for anything you should ever ask of a Cal20. If you mean to go off soundings or even going coastwise to any extent, you should probably be thinking about another six or seven feet minimum. So put your money into something like a Columbia26 which, these days, you can get, ready to go, for the same money as fabricating and installing chainplates on a boat that won't be much improved by doing it.

The Columbia26 sails very well indeed. MUCH better behaved than, say, a Catalina27 IMO! And MUCH more commodious than a Cal20. You can actually cruise in a Columbia26, rather than just play at it. Sez I, having done it four up :-)

TrentePieds

[cyrano138]

Originally Posted by stormalong

A knee is an approximately triangular piece that is perpendicular to the hull and deck. In a fiberglass boat it in usually cut from plywood and glassed to the hull and deck. It is a way to spread the load along a portion of the hull and deck.

I am not familiar with a Cal 20 but to move the chainplates outboard will change the angles of the shrouds and limit how close you can trim your jib.

Also, do you really want to poke bolt holes in your hull, how strong (thick) is the hull and will you need to reinforce it to take the stress of the rig being applied to it.

The Cal 20 is a 1960's boat. It has a lot of history. Apparently the present attachment scheme has worked for about 60 years. Doesn't it make more sense to strengthen the already proven attachment points than to abandon them and start over?

Well, if I have to strengthen them, and that's coming from lots of Cal 20 owners, it seems easier to reinforce the hull (just laying up some glass on the inside) and put them outside. The recommended procedure is to put chainplates on the hull anyway, just on the inside, and then turnbuckle those to an additional set of padeyes. I'm not being contrary but it just seems like the simplest way. I could just leave the whole lot alone and trust the original design, and I may, but I have to replace all standing rigging and set up the mast, so this seems like a more prudent time to do this if I'm going to.

Originally Posted by thomm225

Older boats like my Bristol 27 have fiberglass knees.

I have two on each side and the third shroud is bolted to the main maybe 2 inch bulkhead.

Like was mention above I wouldn't reengineer a Cal 20 just maybe beef up the existing setup or just be sure it's all in good shape.

A Cal 20 Black Feathers did the 2100 mile Single Hand Tranpac Race from San Francisco to Hawaii back in the day so you might want to research that boat.

That race though is usually a nice broad reach run all the way

Even beefed up a bit you are going to take a beating in a Cal 20 on certain days.

I got pretty beatup in my boat, a Bristol 27, the last two days sailing up and down the Lower Chesapeake Bay and it weighs in at 3X the weight of a Cal 20 and about 2' more waterline plus deeper draft.

Example Cal 20 ballast is 900 lbs. Bristol 27 ballast 2575 lbs

https://www.sfbaysss.org/archive-sht..._feathers.html

https://www.amazon.com/Black-Feather.../dp/1440191964

Pearson 10M chainplate / knee upgrade.

Pearson 10M Chainplates

I know it's a small boat and not really suited for offshore work, but what can I say I -- it's the boat I've got, and I'm 2/3 of the way through a total refit. I kind of just want to finish it (sunk cost notwithstanding). I do have a budget for a larger boat, but I want to take my time and use the cal 20 in the interim to get more experience at the helm. Or tiller as the case may be.

Originally Posted by Benz

The best material for chainplates is silicon bronze, aluminum bronze is a close second. You can put in bends by clamping the strap in a vise and levering hard on it: I bent 3/8" bronze bar stock this way.
Unlike some others above, I approve of moving the chainplates out to the hull; just be sure you have good structure where they go.

Thank you! I am going to call a place tomorrow and price some bar stock. Is it harder than SS? Hardened steel? I never seem to have much of an easy time drilling hardened steel and that might be reason enough to leave things be.

Originally Posted by Wotname

You can have a read of this long thread - lots of opinions about the best chainplate materials on the last few pages. Jury is divided between bronze (silicon bronze and Ti).

https://www.cruisersforum.com/forums...me-269241.html

It really depends on how long you want them to last and how easy is it to remove and inspect for crevice corrosion. If you plan a DIY job and they are easy enough to access and replace every (say) 10 - 15 years, just make them from common SS316 and polish well. If you want longer lasting ones or if they are inaccessible, go for more longer lasting materials - bronze, Ti, more exotic SS etc.

Back in the day, galvanised steel was the way to go and regal as needed.

10 to 15 years would be fantastic.

Originally Posted by TrentePieds

Cyrano said: "I am thinking about switching all the shroud attachments (on deck) on my Cal 20. It has three sets, two uppers and one lower (or maybe vice versa but in any case three altogether), all of which attach to the deck via padeyes."

Why would you bother for a Cal20??

Lovely little boat in many ways, but after all she is no more than a dinghy with a deck. Sez I, having taught some hundreds of people the basics using Cal20s half a century ago.

Your existing pad eyes are perfectly fine for anything you should ever ask of a Cal20. If you mean to go off soundings or even going coastwise to any extent, you should probably be thinking about another six or seven feet minimum. So put your money into something like a Columbia26 which, these days, you can get, ready to go, for the same money as fabricating and installing chainplates on a boat that won't be much improved by doing it.

The Columbia26 sails very well indeed. MUCH better behaved than, say, a Catalina27 IMO! And MUCH more commodious than a Cal20. You can actually cruise in a Columbia26, rather than just play at it. Sez I, having done it four up :-)

TrentePieds

Like I said above, it's the boat I've got. I appreciate the input, for real, but I think I'm stuck with her for now at least, while I look for a nice Bristol 27 or something like that.