IMPORTANT SAFETY ISSUE

[Troy Scott]

Folks,

After reading about issues with embedded and rusted steel in our boats, I worried for a while, then I contacted Dave Perry at Robinhood. The folks at RMC are, of course, the most knowledgeable folks around when it comes to our aging yachts. He replied very promptly with these remarks:

Hi Troy,

It is great to hear from you, Troy, and I think of you often with your sizable project of bringing the Cape Dory back to life! I have seen some of your posts on the CDSOA site, too, and others have offered good information.

The smaller Cape Dorys and the early 36's had steel chain plate reinforcements that had sections welded onto them that were glassed into the hull laminates. Also, steel was used in the mast support area of the small boats. Of course water and steel are not a good mix, and when the bedding around the chain plates, or the toe rails or life line stanchion bases begin to give out, the chain plates are affected. We are starting to see cases where the steel is rusting badly and the chain plate area is compromised. Even to the point where the area in the laminate will expand and cause a problem. Everyone with these earlier or smaller boats should inspect these areas and be sure their deck fittings are tight.

Good news is that in 1983 the chain plate reinforcement on the larger boats changed to aluminum. Also, the reinforcement down the side of the hull became strictly fiberglass, with multiple layers of uni-directional laminate running between the waterline area and curving up under the "shelf" of the deck joint. Then the aluminum plate is placed under the entire area. In the case of the "36" there are two sections on each side. This is the same way we do it today on the
R36. There is no steel in the construction of your boat, other than the steering supports. Also, all stanchion bases have aluminum backing pieces.

The Cape Dory 36 continues to be one of the most popular cruising boats available so she will be well worth all of your efforts. I hope that this is helpful and reassuring!

My very best regards,
Dave
Robinhood Marine Center
340 Robinhood Road
Georgetown, ME 04548
207-371-2525
David Perry, CPYB
Broker

[Matt Cawthorne]

I have CD 36 Hull number 79. It was initially laid up in 1982, but completed in 1983. I thought the backing channels were Stainless, but it could be that they are aluminum. They are not mild steel for certain. Are the owners of #78 or #77 reading this board? It might be informative to know by hull number whether the boat has the mild steel backing plates.

The motor mounts in my boat are mild steel.

Matt

[Troy Scott]

Matt,

I can't say for sure, but I believe I remember an owner saying that even though his shrouds were backed by aluminum angle, there was a steel weldment under the forestay and sprit. This suggests to me that the changeover to aluminum may have happened in stages.

Here's a thought for those of us who have the aluminum structures: Owners of older airplanes have, for the last 20 years or so, been treating the interiors of their aluminum fuselages and wings with a spray/fog treatment for corrosion proofing. I think the stuff they used on my old Bonanza was called ACF-50. It does seem to work. It might not be a bad idea for us to treat these aluminum pieces similarly.

Hopefully the majority of the affected boats have had no leaks and the steel is still OK. I would hate to think I had to remove and replace embedded steel backing plates from the hull-to-deck joint. Removing the mild steel engine bed was pretty hellacious. But I'm glad I persevered. I'm happy with the new bed. While I was at it I had the steering braces, the mount for the coolant overflow, and several other pieces blasted, spray galvanized, and epoxy primed. All these parts will also get bilge paint when I paint the bilges. Another thing I want to do before I get much further along is test the fuel tank. It's a green painted welded metal thing under the cabin sole. I hope it's OK. With regard to other tanks... I hope to install a LectraScan and plan to never use the holding tank unless I go somewhere where absolutely NO discharge is allowed. I'd rather just sterilize that thing, dry it out and forget it's there. I had a LectraSan in my last boat (the one Katrina ate) and it worked very well. We used to say that we were slowly cleaning up the marina, one flush at a time.

[Duncan]

Hopefully the majority of the affected boats have had no leaks and the steel is still OK.

I'd be inclined to doubt this, Murphy's Law and all.

Nothing lasts forever: water infiltration is a given, and then so is corrosion.

Thanks for digging this one out.

Bronze external chainplates are as good a solution as I could think of.

.

[Russell]

I too doubt that there would be many boats out there who have the mild steel would be okay. Considering the condition of everyone who has pulled any mild steel out of their bow or chainplates has found it to be in horrid shape. I dont recall ever seeing anyone who has actually inspected their finding it to be okay.

I am glad to know my boat is a post changeover boat. But I am still not entirely impressed with the entire chainplate system on the CDs. If I ever find the slightest problem my plan is to eventually change my chainplates to traditional external chainplates.

[Mark Yashinsky]

do you have any stainless fasteners going into the aluminum? That is a big issue, if left untreated.

[Matt Cawthorne]

Yes they are stainless fasteners on my boat. So far, I can find no evidence of leaking in this area and I just had the cabinetry out of the boat on the starboard side this winter. I hate to start disassembling the chainplates to replace bedding compound. It is a huge job, and so far there is no evidence of a leak. The system that Cape Dory used for the chainplates that use a through bolted fitting is one that is supposed to be excellent for preventing leaks while remaining protected from issues arising from collision with the dock or another boat.

[Russell]

Stainless into aluminium will seize, but will it fail? I am asking because I do not know. We all have stainless screws in our mast fittings, etc.. I have had to drill such fittings out, but in no way did they give the impression that they were going to fail and we are talking about something far more exposed here.

[tmsc]

I really enjoy this issue.

Our boat also has steel channels for support of the shrouds. The port structure looks brand new. We did have an issue with the starboard one in an area where a previous owner had installed a padeye for a boom brake. Apparently it had been leaking at one time.

Speaking of the shrouds, I personally don't have a big problem with the use of steel. There are a lot of steel boats out there that are old and in good shape. Just a maintenance thing. Sure stainless or aluminum would be nice, but I am not a big fan of encapsulating SS either. Cut the oxygen off cut your head off, I say. I am curious though, how many of you have substantial glass over the tie straps? The ones I have seen are not all that heavily glassed over IMHO. I'm not a naval architect or engineer, but I wonder how much of the load is carried by the straps glassed to the hull and how much is carried by the channel? I suspect that the channel may be sufficient in and of itself. I partially base this hypothesis on the the construction of some Euro boats I have seen. For instance, an Albin Vega that I had used U-bolts for the shrouds. Fairly common practice with Euro's. These U-bolts went through the hull to deck joint and were backed by an aluminum channel that extended approx. 1 foot beyond the fore and aft lower chainplates. Pretty strong structure given that I have seen a picture or two of the boats being picked up by the U-bolts. Moreover, many of the older Contests and Camper Nicholsons used similar arrangements. Sure the hull to deck joint itself is supposed to be extremely strong, but some of the U bolts on the Contests are slightly inboard of the hull to deck joint and do not have the heavy backing we do. Furthermore, the older Contests such as the 31 and 33 have solid frp decks and being without core they are a bit more flexible than a Dory. However, with all of these differences, the only major problem I have come across with them is crevice corrosion of the stainless steel U-bolts which Contest glassed over on the interior side.

With all this said, I wonder if it would really be worth the effort to change the chainplates to external ones. Admittedly, I am a big fan of external chainplates, and some bronze ones would probably look darn good on a Dory. However, the engineering for the original set up has been done and stood up to the test of time. Changing over to externals also raises a lot of questions in my mind, and I wonder if it would be worth it. Off the top of my head for instance:

1. If the boat is going to be used hard, would the hull structure be sufficient without adding additional laminate thickness in the attachment area to prevent hole elongation or oil canning?

2. If additional laminate is necessary, how difficult would this modification be for the uppers since they are often inline with the primary bulkheads? Would this be more difficult than just replacing the original structure?

3. How much effect would moving the shrouds outboard have on pointing ability since the angle would change?

4. Modification of the toerail.

Well its getting late and everyone is probably getting tired of my rambling, so I am going to shut up and rest up in preparation of the cannon fire. Let me have it. I look forward to y'alls thoughts and insight.

[Matt Cawthorne]

The bolts pass through the aluminum and have nuts and washers on the back side. Also, not all aluminums are equivalent. For instance, some of the high strength aluminums used in aircraft are subject to corrosion, sometimes with serious exfoliation characteristics. Other grades, while not as strong, have far better corrosion resistance. The aluminum used in the mast is subject to continual exposure to moisture and salt. Even so, after 25 years, there are very few examples that I have seen where the mast is corroded completely through. Actually I have never seen one. The backing under the deck is much thicker than the mast wall. My self steering device is made from aluminum, not painted or anodized and after 5 years looks like new.

Matt

[Troy Scott]

Russell,
Aluminum and SS are not that far apart on the galvanic scale. It just doesn't make a very good battery. Unless there is moisture combined with stray electrical current, there will probably not be a problem. At least that's what they taught us with airplanes..... At any rate, the corrosion block stuff I mentioned penetrates and insulates. It is, I suppose, a "can't hurt and would probably help" thing. You can brush it or spray it. I'll do mine. I'm replacing all the hardware, so I'll have a good opportunity to coat the parts of the stainless that would otherwise be in contact with the aluminum. I'll have to do some more investigating to learn exactly what would work best. Sometimes effective preventive measures can be surprisingly simple: I remember David Glover, a Cape Dory dealer and knowledgeable service guy in Fairhope, Alabama in the 70s and early 80s, would put plastic tape on the bottom of the mast base where it sat on the SS deck fitting. This stopped the corrosion that sometimes happened when salt water would get a battery going there.

[Mark Yashinsky]

anyone remember a certain older Aloha 737, operating in the Hawaiian islands, and the issue it had with corrosion? The aircraft was 19 years old, at the time, in the area of many of our boats. Please dont be complacent about items that are highly stressed, thats all.

[Troy Scott]

Mark Yashinsky,
You're referring to the incident where a large section of the fuselage came off in flight, right? I believe the plane was later landed safely, but there were deaths.

[M. R. Bober]

anyone remember a certain older Aloha 737, operating in the Hawaiian islands, and the issue it had with corrosion? The aircraft was 19 years old, at the time, in the area of many of our boats. Please dont be complacent about items that are highly stressed, thats all.

No doubt we need to be aware, but the airplane analogy seems unwarranted in this instance. Just like running aground, airplane failures are much more dramatic than those of ships, but then so are their stresses and design restraints (think weight of materials).

Mitchell Bober
Sunny Lancaster (where I didn't invent ultracrepidarianism, but none-the-less...), VA

[Troy Scott]

Weeeeellllll...,
Sorry about starting this boat-airplane analogy thing..., it's a bad habit I guess. But.......
I'll have to add that if I were in a small Cape Dory well away from land and my chainplates came loose, I think I might be in just as serious a fix as someone in a failing airplane at 30,000 feet. (Of course I'm talking about a failure of something other than a major control surface or a wing.) Especially if the failure happens in a storm (that's probably when it would happen) and more especially if the mast fell on my head! All this written respectfully and while smiling.... In other words, a dismasting at sea in a storm is about like losing the engine in a single-engine airplane. It's survivable, but only if you act quickly and don't panic. It is serious. And corrosion really doesn't know whether it's in an airplane or on a boat, especially if it's a seaplane!