Alberg 30 Chainplates

[Cruiser2B]

I have a couple of questions regarding Alberg 30 chainplates, I am getting ready to remove the mast and replace the standing rigging. I was hoping to get new beefier chainplates made as well as replacing and upgrading the harware. Are all the chainplates for liner and non-liner boats the same. Mine is a liner boat#457, i know someone who has a non-liner boat that just replaced his chainplates that I may be able to use as templates. I am trying to cut down on the down time. if I had chainplates built and ready to go back in this would keep it from getting dragged out.
also do the chainplates actually need to be replaced? i do not see any corrosion, i keep reading that just the hardware should be upgraded. I do someday " plan" on sailing across the atlantic in this boat so I want the chainplates to be up to the task.. If i do end up replacing them, what material? 316? silicon bronze?

Thank you

Jason

[Cruiser2B]

Doing them one by one is not a bad idea,one i had thought of but did not think was very safe. i was going to pull the stick and replace windex and all standing rigging while I was at it. Is it safe to go up the stick to remove the upper shroud one at a time? i dont see much of a problem with the lowers....i guess i just dont trust a halyard that far up! I would rather do it this way as it would save me 300 bux in fees for pulling and reinstalling at the local yard.

[Rachel]

For myself, I would be suspect of any 30+ year old stainless chainplates, mostly because of possible crevice corrosion. If it were me replacing I would go in with bronze, because I like that it does not fail "sneakily."

I'm not familiar with the chainplates on a "liner" A-30, but are you asking because there are size constraints in the boat itself? If not you could use a formula, such as in Skene's, to determine what size they should be.

As far as "beefing" up a rig, I would say tread carefully*. That's because, like an anchoring system, it's all connected and it can be easy to make "weak links" that can actually be detrimental. For example, say you decided to "upsize" the shrouds. Well, you need to tune them to within about 10% of their breaking strength (no matter what size they are), only now the breaking strength of the larger wire is more, so you are putting more load on the chainplates, tangs, and other rigging parts. If you upsize such that you need larger clevis pins, you may need enlarge the holes in your tangs, and then there may not be enough "meat" left, etc. And so it goes.

*Of course that actually doesn't apply to chainplates, because you could, theoretically, make them HUGE and it would not cause extra load on anything else. But it sounded like you were considering "upsizing" other parts of the rig.

That's not to say that nothing should be upgraded; but just that "upsizing" doesn't automatically make things better.

Back to the chainplates, here is an example of information from Skene's Elements of Yacht Design, by Francis S. Kinney, regarding chainplate sizing. I had this in my A-30 notes, but of course do double check it - this is just go give you an idea of what you can find:

Based on 1/2" pin and 1/4” wire.
Headstay and backstay tangs are 5/16” thick
Chainplates for shrouds are 1/4” thick
Width in both cases is 1 3/8”
Center of hole for pin is 13/16” from the end and the end is round with an 11/16” radius

The figures are the same for silicon bronze or stainless (not sure if 304 or 316 at the moment, but essentially just saying that they are about equal in strength for this purpose).

One note that pertained to at least the first- and transitional-generation A-30's is that the forward shroud chainplate bolts were deficient. I think they were too small, and also were threaded the whole way through (i.e. there was no shoulder).

[Rachel]

i was going to pull the stick and replace windex and all standing rigging while I was at it.

Speaking of which, if the second-generation A-30's use the same cast-aluminum masthead fitting as the first-generation ones, that is another thing you might want to look over. Several of them have developed cracks (including the one I had), and there have been some "group replacements" made. Yours may be fine, but if you are going to take the mast down it is something you could take a close look at.

Rachel

[Paulus]

Well, you need to tune them to within about 10% of their breaking strength (no matter what size they are).

Why? I have a deck stepped mast and if I were to follow this rule, I would certainly have deck compression...

[Rachel]

I'm no rigger (which is probably obvious), but I believe it is to "stretch" the wire rope to an appropriate amount so that it is tight but not too tight, and "loose," but not too loose. That way it stays "stable," if that makes sense. I have a Loos gauge but I think pros can do it by feel or sound or something more intuitive than a gauge.

Everyone may not use the 10% figure [see edit below], but I believe the concept still holds, which is that wire rope rigging needs to be tightened to within X percentage of its breaking strength, and the larger the rope, the more pressure that figure would represent. So, say you "went up" two sizes of wire rope to make your rig "bombproof," now you would be putting much more tension on your chainplates, tangs, etc. and could overwhelm their design parameters (not to mention having extra weight aloft, etc.).

Edited to add: I'm not sure where I got the 10% figure (it may be valid for some rigs, or I may have mis-remembered it), but here is a selection from Selden's rigging guide that confirms the "X percent of breaking strength concept. They advise 15-20%:

It is a fundamental requirement for all rig types that the cap shrouds are correctly tensioned. The cap shrouds are adjusted at the dockside, but final tuning is done while sailing. The table beside applies to standing rigging using 1 x 19 stainless wire. This is the most commonly used material for standing rigging.
Your aim should be to tension the cap shrouds to 15-20% of the breaking load (the final check on tuning should be left until you are under sail). Then you know that the lateral staying is optimal both for the security of the rig and for sailing performance.

My point was just that the same percentage of tension will be a lot more force with a larger wire rope as compared to a smaller one.

Here is a link to the Selden guide:

http://www.seldenmast.com/_download.cfm ... -540-E.pdf

Rachel

[Cruiser2B]

[quote="Rachel"]As far as "beefing" up a rig, I would say tread carefully*. That's because, like an anchoring system, it's all connected and it can be easy to make "weak links" that can actually be detrimental. For example, say you decided to "upsize" the shrouds. Well, you need to tune them to within about 10% of their breaking strength (no matter what size they are), only now the breaking strength of the larger wire is more, so you are putting more load on the chainplates, tangs, and other rigging parts. If you upsize such that you need larger clevis pins, you may need enlarge the holes in your tangs, and then there may not be enough "meat" left, etc. And so it goes.

Thank you for all the good info. I was intending on staying with 1/4" stays and shrounds, was only going to upgrade the inner lower stays to 1/4". i was going to beef up the chainplates, mounting hardware and adding backing plates. I was also thinking of adding hardware to the mast for a storm trisail and a removable inner forstay. again just the harware for future mods. i appreciate all info.

as far as tuning goes...the physics are beyond me but i do not current think my shrouds are adjusted anywhere near that tight....actually seems a bit loose...... I may get a rigger involved when putting it all back together.

thanks again to all, keep the info coming if you've got it

[Rachel]

Thank you for all the good info. I was intending on staying with 1/4" stays and shrounds, was only going to upgrade the inner lower stays to 1/4".

That is probably totally reasonable. It would seem that you could double-check by looking over the tangs, turnbuckles, etc. (presuming you are re-using them). I may have over-reacted to your first post, but if so it's because I have so often read about people "beefing up" their rig by going to oversized wire (or using such as a selling point) to make the rig "bombproof" when I suspect they have not gone over the "system" as a whole.

i was going to beef up the chainplates, mounting hardware and adding backing plates.

I think those all sound like good ideas. Backing plates are something that was often skipped or undersized in much of the the "classic plastic" I have seen. And 30-year-old, through-deck, stainless chainplates.... I don't think you can go wrong in replacing them or at the very least removing them, thoroughly inspecting them, and going forward from there.

[Paulus]

I don't want to be a stickler, but the difference between...

"Your aim should be to tension the cap shrouds to 15-20% of the breaking load (the final check on tuning should be left until you are under sail). Then you know that the lateral staying is optimal both for the security of the rig and for sailing performance."

and

"you need to tune them to within about 10% of their breaking strength (no matter what size they are)"

Is huge...

I am sure you meant "to" 10%, no?

[Rachel]

I am sure you meant "to" 10%, no?

Yes - thank you for pointing that out. I'm really sorry about the mistake - that's embarrassing! It looks like you were onto it with your previous post, and trying to help me out with your question, but I missed the subtlety.

I was trying to illustrate a concept and clearly I should have stuck with my "I'm not a rigger" status and not used any actual numbers. Next time I will generalize if I'm not positive.

Rachel

PS: Nothing wrong with being a stickler; I encourage it!

[Paulus]

The concept is correct and makes sense - the 10% (or whatever number) of breaking strenght correctly, as you pointed out, creates a correlation between wire size and preloading to overcome stretch problems.

A friend of mine got dismasted in a big powerboat wake. The root cause analysis was that the shrouds were too loose, allowing sufficient slop to have the expected mast pumping action gain sufficient momentum to snap it at the spreaders. The idea is to have tension on the shrouds at all time - a preloading with resultant stretch would do just that.

[Cruiser2B]

Thanks for all the useful knowledge. I have set of A30 chainplates being send to me to duplicate before taking mine out. Once I have mine out I will simply drill the holes in the new units to match mine. I have read and been told told that the holes in the knees and chainplates probably vary from boat to boat. I was aboard another A30 this weekend 8 hull numbers older than mine and the chainplates were mounted on the opposite sides of the forward knees than mine...go figure!

[Rachel]

I have read and been told told that the holes in the knees and chainplates probably vary from boat to boat.

See, now I wasn't even thinking that there was any chance the actual holes would be the same... (but of course there have been times in the past when I did...) Sounds like you have a good plan now.

I was aboard another A30 this weekend 8 hull numbers older than mine and the chainplates were mounted on the opposite sides of the forward knees than mine...go figure!

Welcome to the Wide World of Plastic Classics :D (Well, I don't know if they all have such variation, but some certainly do.) (All part of the "fun" once you get used to it - which I guess you are now!)

The first time I looked around belowdecks on an early Triton (I was used to seeing slightly later ones), imagine my surprise to see that the chainplate knees weren't even in the same places, fore-and-aft. I had to look for them.

[Cruiser2B]

been thinking and reading and have decided to use 316- 1 1/2" x 1/4" for the chainplates. boat has original 3/16" x 1 or 1 1/4 now. I am gonna replace the lower and then the upper chainplates and the backstay last before unstepping the mast. I think this will make for less down time once mast is down. i will use 3/8 SS bolts instead of 1/4 machine screws. I will also make new backing plates as there is none now. I pulled a couple of bolts from each fordward chainplate knee and wood inside seems solid. i poaked around in the holes with the pointy end of a 12v test light....seemed solid.i will document the process in the projects section. I am gonna order the material Monday

[David VanDenburgh]

Looking forward to following your progress. One of these days, I will be doing chain plate work on my A30.

By the way, here's an interesting interview with Yves Gelinas, designer of the Cape Horn self-steering gear, who sailed his A30 around the world in '82 or so. In addition to several details about his trip, he talks about his chainplate failure and details his fix. He modified his chainplate knees to extend down through the forward shelf to increase the bonding area. You might be interested in watching.

http://youtu.be/OGpcKRL9dP8

[Rachel]

You may already be planning this, but from what I understand it's important to get them as polished as possible if you are using stainless, to help keep crevice corrosion at bay.

[Cruiser2B]

You may already be planning this, but from what I understand it's important to get them as polished as possible if you are using stainless, to help keep crevice corrosion at bay.

yeah planned on it, i have been asking around town about a local place to do it(polishing) everyone says they do it themselves. so..... i have a pretty heafty bench grinder and will try it myself. I will keep you guys posted on progress. I have heard of a coating that also helps that is sprayed on them once polished....not sure what it is or where to get it.

As far as extending the knees...not this time around, the knees seem in pretty good shape and will be doing abunch of other upgrades. I do not want to turn this into a complete refit. I figure what was there has lastest this long. My upgrades and carefull planning will for sure be better than whats in place now. I do plan on a complete refit in 4-5 years from now. i am just doing some upgraded maintenance, if you will, this time around.

I have come to the conclusion from research and talking with other Alberg 30 owners that my standing rigging is orginal. My upper shrouds have a thimble with a clamp on it at the top attachment tang....YIKES! from talking with another Alberg 30 owner this is how it was done...i am not impressed..... i guess it cant be that bad as it has lasted some 40+yrs, but i will replace the uppers, fore and back stay this winter as well.

While the mast is down, i will put a wind index, replace mast head anchor light and place a piece of conduit on mast to keep wires from "clanging" all efffffffin night long at anchor! All these mods with the V-berth upgrades will set me back some, as i have a limited budget......with that said I feel I will have piece of mind with the upgraded chainplates that will have new /larger hardware as well as some new standing rigging.

I appreciate everyones inputs about upgrades. but this is a bare bones operation......on top of above upgrades/maintenance, I am also sending our sails to sail loft.... i think they are almost 15yrs old. They will be cleaned, examined and repaired as necessary. my bank account is limited and everything is cash basis...no credit ever! so i am doing what i think is nesssary and manditory at the this time....and eating Ramen noodles:)

Wife will feel more comfortable with living conditions and i will feel more comforatble with rig/safety. After we have a few more years cruising on the Ches Bay and maybe a trip to New England we will have a better idea of how we will refit her for extended/offshore cruising.

[Cruiser2B]

not exactly, McMater-Carr has a 6ft piece for 85 bux....

[Cruiser2B]

Have you decided where you are going to purchase your SS stock??

http://www.onlinemetals.com/merchant.cf ... &top_cat=1

Looks like your suggested place has it for 52bux....THANK YOU! for the info. I will see if they are open on SAT. if not we'll order it monday....Thanks again

I love this site and all the available knowledge!!!=Priceless

[Rachel]

Since you are trying to keep the budget and effort in line, one note on your proposed re-wire and replacement of the top-of-mast anchor light.

I'm not a huge fan of top-of-mast anchor lights, because I find that if I am anchored it is usually in a "close in" type of situation vis-a-vis other boats. That is, I'm not worried about ships seeing me from five miles away, like I would be if I were out sailing. I'm worried about a quarter or a tenth of a mile, or a few hundred feet away seeing me. And to see my mast top they would have to crane their necks and possibly try to pick it out amongst the stars. So, I prefer a lower anchor light, not at deck level but much closer to it. I usually hung mine from the forestay, somewhere around 10' above the deck (I like to have it in the forward part of the ship for the information it gives people, i.e. they expect the rest of the vessel to be lying abaft the light).

Just a thought since you are re-fitting the anchor light, and the closer-to-deck version may have the added advantage of being cheaper/simpler/easier.

Rachel

[Drew]

I used bronze for my new chainplates, However:

Practical sailor has an interesting article about Titanium for chainplates this month. I had never considered Ti for this purpose due to cost but the folks in the article stated that they were under $300 for ten Valiant 40 chainplates fabricated. That seemed fairly reasonable considering the machining time involved. I believe the company was Allied Titanium.

Titanium is very corrosion resistant and not subject to crevice corrosion. It would be a good choice for chainplates.

Drew

[Cruiser2B]

Drew,


thank you, i just recieved the 1.5"x.25x 6ft piece of 316L today. I am hoping to remove lower shroud chainplates tomorrow to begin fabricating the new ones. i will post picks

[mitiempo]

Drew

That is most likely $300 each.

[Cruiser2B]

the 6ft piece of 316 was $70.02 to my door! premade generic stainless chainplates were about $100 each. i have plenty of metal working tools so making them should not be too bad. heading to the boat today to remove some of the old ones.

[Drew]

On second reading you are right, $300 each. I was going from memory and it was late when I read the article. Wow that is expensive! 316 is an excellent choice. Your new chainplates will work out great.

Drew

[Cruiser2B]

I removed the port side lower chainplates, i took some pics but have just been too lazy to load them. they did not look to bad at all. but better safe than sorry. i will have the new lower ones done by next weekend!

[Cruiser2B]

Speaking of which, if the second-generation A-30's use the same cast-aluminum masthead fitting as the first-generation ones, that is another thing you might want to look over. Several of them have developed cracks (including the one I had), and there have been some "group replacements" made. Yours may be fine, but if you are going to take the mast down it is something you could take a close look at.

Rachel[/quote]


Do you have a source for these? mine is not cracked but it surely does not look in very good shape. it is cast and does look like it could be replaced. My mast base plate is cracked and broken. i think i have a pan for a new one of those. Thank you

[Cruiser2B]

I am glad to report i restepped my mast today. i replaced all the chainplates, mast tangs, standing rigging, fabricated mast base step, and blocks. I also fabricated a mast base plate for turning blocks. I will post pics this week. thank you all for all the help.