Glassed In Bobstay Chainplate

[benjiwoodboat]

I just removed my bobstay chainplate. It is a Y shaped, welded piece, that's glassed in... was a bit of a pain to remove, but doable. I'm wondering what the general thought is on that installation. I was considering redesigning and using two seperate bars on either side of the bow, bolted in, like a more traditional chainplate. But I don't want to get into redesigning the wheel if this glassed in approach is considered to be a decent approach. I'm going to have to do glass work either way, so it doesn't matter to me. But NEXT time, avoiding the glass work and difficult removal/installation would be a nice bonus.

http://lh6.ggpht.com/BenEriksen/SESd...JPG?imgmax=512

http://lh6.ggpht.com/BenEriksen/SESb...JPG?imgmax=720

http://lh3.ggpht.com/BenEriksen/SESb...JPG?imgmax=512

[Brian Duff]

Ben ,
As you can see from the condition of the fitting, being buried in the hull was not healthy for the stainless steel

On all custom fittings we design they are bolted outside the hull with heavy backing plates

Also, being so close to the waterline you probably should not use stainless anyway, the stuff sucks in wet enviroments.... consider bronze for longevity, or at least use a zinc to protect the stainless from corrosion.... or paint the stainless that helps too...

fun fun

[benjiwoodboat]

Thanks Brian,

I'm consdering Bronze for all my chainplate replacement. Still undecided.

[Brian Duff]

Bronze
Ulitmate Tensile Strength 85000psi
Yeild Strength of 55000psi
elongation at failure 20%
rockwell hardness B90

316 Stainless
Ultimate Tensile Strength 89,900psi
Yeild Strength 60,200psi
Elongation at failure 45%
rockwell hardness B91

As you can see bronze is only about 5% weaker ultimate... as far as maintaince goes it is much better as long as you don't mind the green patina it will get... if you do then powdercoat clear after polishing.

Skene's charts for chainplates have identical dimensions for stainless and bronze, and thats how we;ve been making stuff...

[benjiwoodboat]

Brian, thanks again. Where are these numbers from? Did you get my email?

[Brian Duff]

onlinemetals.com

[benz]

Hi Ben,
The boat I'm assembling, a Cape George 31', is supposed to have a glassed-in bobstay chainplate similar to yours, only done in bronze. The owner's brother makes them custom to order, and they are beautiful. You might give him a call and see if he can make you one--Google "Cape George Marine Works" for the phone #.
In spite of that, I opted to fabricate my own chainplate and bolt it on with backing plates--it was cheaper that way, since I was buying bronze for all my other chainplates anyway. I just purchased a plate of 3/8 silicon bronze and a smaller plate of 1/4, (I found Atlas Metals to have the best price, still about $10 a pound), and cut out all my shapes with a borrowed plasma cutter. My saber saw can chew through the 1/4" plate OK, but the 3/8" was too much for it. Starett or Lenox brand blades seem to work best. The edges can be finished with a grinder, and sanded to any polish you desire.
If you'd like, email me: benz@yosemite.net and I'll send along some pictures of my bobstay chainplate.
Best,
Ben

[Brian Duff]

another great option is to draw up your pats and send a .dfx (if i remember right, I have a guy that does all the drawing for me...) file to a waterjet shop. THese machines do a great job of making parts, cheap and fast !