Corrosion on boomkin stainless

Several months ago I noticed some cracks in the tangs on the bottom stainless boomkin plate. That area gets some spray when we’re motoring as the exhaust is slightly submerged so exhausty spray blows up. I wasn’t that surprised to find the cracks, as about 7 yrs ago I replaced the tangs on the other end of the whisker stays that are attached to the hull just above the waterline due to cracks. It’s easy to overlook the bottom boomkin plate–it’s awkward to get a good look at, and I didn’t keep it polished up.

I finally bit the bullet and removed the plate (after removing the lift-up Aries and undoing the jib stay, backstay and whisker stays), and confirmed after polishing it up with a 3M red abrasive pad that the cracks were extensive. The stainless fabrication shop found that a light hammer tap broke one tab off! The picture shows that it broke above the weld. The welder thought the tabs, unlike the plate, were probably not 316 stainless.

I know that several of you have expressed a strong dislike of stainless steel and some are replacing it with silicon bronze fittings. I understand, but decided to stay with ss on this one. The upper boomkin plate appears to be OK. Shaula is 30 yrs old and has spent about half that time in the tropics or near-tropics. I guess I’d suggest that the lower boomkin plate and the tangs on the hull should be inspected for cracks, especially on older BCC’s.
Dan Shaula BCC #59, 1981

2 boomkin tang cracks after cleaning.JPG

Hi Dan , Thanks for the “Heads-Up” , so this is the reason why good marine surveyors, recommend changing out all SS structural fittings, that spend their life in the tropics, every 10 years !

The cracks look similar to the cracks I found around the toggle pin holes on the midship chainplates, and of course on the lower Bob Stay Chainplate.

FWIW , I had my exhaust thru-hull moved 3" higher on the transom, for the reasons you mentioned.

BTW , good marine surveyors agree that is bad practice to hang anything structural on a SS welded fitting.

While visiting the Mystic Seaport Wooden Boat Show in 2008 , I saw all kinds of bronze and copper structural ,“strap” fittings, that could be good replacements for our BCC’s SS welded Structural fittings.

port townsend foundry made all the pieces i needed in bronze. whisker stays, new bob stay fitting. i expect it will last me a lifetime. fwiw, 316 stainless is not immune to crevice corrossion.

That’s a bit alarming! I replaced my boomkin plates with silicon bronze ones cast by Port Townsend. My plan has been to replace all the critical stainless steel fittings with silicon bronze, but I will have to find another source, as Port Townsend has been totally non-responsive to any requests I place with them, notwithstanding that I have literally spent thousands of dollars with them over the past number of years. Strange way to conduct business!

PT Foundary could close it’s doors to the public and only do wholsale work and probably be fine with that. They are deffinatly NOT hurting for business which makes them a little hard to work with, must be nice. If you can get in contact with Pete’s wife (sorry forgot her name) she will make sure you get what you need.

Also another option is to call up Todd at CGMW and have him order the parts through PT Foundary. This is the method I used until I got a hold of Pete’s wife. Todd is very helpful that way and knows that working with PT Foundary can be difficult at times.

Thanks for the feedback - I have dealt with Pete’s wife in the past (I too have unfortunately forgotten her name), but more recently without success. Good suggestion to talk to Todd at CGMW. I believe PT Foundry produces quality products, but they are not easy to deal with.

Dioscouri (#064)

Hi Guys, Pete Langly at PT Foundry does his foundry work as a hobby, and is not so interested in production.

Pete and his parents built a sailboat in Morro Bay, when he was just a kid, they then sailed it to the south pacific, but eventually lost it to a lee shore during a typhoon, and steering failure, at least that is the story he told me.

A Big Yes, he gets way more work than he can handle, but his bronze’s are “lifetime fittings”, and will outlast your boats.

As an alternative I suggest to those in need, to look for suitable design replacements, that can be made or fabricated from flat and plate stock silicon bronze.

I am away from my photo files at present, but will attach some examples in the future, like cranze irons made from strap brnz, chainplates made from strap brnz, ect., ect.

So, you don’t really have to wait and wait and wait for Pete’s bronzes, and save $ at the same time.

And other people do fine bronze casting as well…

Here are some creative examples of using Silicon Bronze plate, strap, and flat stock, to fabricate structural fittings without using welded SS or welded, or cast bronze parts.

There are many other examples of non cast and non welded structural parts, but sorry that I don’t have more examples in my files.