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  #1  
Old 06-09-2010
jct jct is offline
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Tayana 37 Bobstay Bolts

To Rich Hempel, wherever you are: miss you on the TOG forum! Thanks to an old post of yours, I just pulled my bobstay bolts and found some very serious corrosion. Now the wrinkle: the yard did not follow your directions and they simply unscrewed the slotted carriage bolts. The shaft hear the head is very corroded, but the threads that were enclosed in the nuts look very good. I think I want the yard to follow your procedure to remove the nuts and use new ones with the new bolts. Do you agree? Anybody think I should just put new bolts into the old nuts?

Assuming you think I should replace the nuts: what did you do about the new hole in the chain locker? Did you leave the nuts exposed for future replacement/ease of examination? Did you fill the hole back in like it was? If you left the hole/nuts exposed, how did you keep the hole from turning into a mini-bilge with no drain outlet?

Thanks very much in advance!

John
SV G'Ride
T37 #82
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Old 06-09-2010
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I believe the Baba/Panda/Tashiba boats have a similar rigging where the bobstay fitting is outside the the anchor locker. I believe the earlier models had the nuts buried in glass like your boat. I know a few owners cut/dremeled/dug out the old nuts, filled with epoxy, drilled new holes, then used a backing plate in the anchor locker. If this would work for you, it would probably be your best option. This site might help:
bobstay
PS- Where are you getting new bolts for the bobstay fitting? Are they 5/16 x6''ish round head? Mine are also suffering from crevice corrosion.
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Tayana 37 Bobstay Bolts-dsc_0333.jpg   Tayana 37 Bobstay Bolts-dsc_0315.jpg  

Last edited by mrybas; 06-09-2010 at 11:20 PM.
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Old 06-10-2010
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Quote:
Originally Posted by jct View Post
To Rich Hempel, wherever you are: miss you on the TOG forum! Thanks to an old post of yours, I just pulled my bobstay bolts and found some very serious corrosion. Now the wrinkle: the yard did not follow your directions and they simply unscrewed the slotted carriage bolts. The shaft hear the head is very corroded, but the threads that were enclosed in the nuts look very good. I think I want the yard to follow your procedure to remove the nuts and use new ones with the new bolts. Do you agree? Anybody think I should just put new bolts into the old nuts?

Assuming you think I should replace the nuts: what did you do about the new hole in the chain locker? Did you leave the nuts exposed for future replacement/ease of examination? Did you fill the hole back in like it was? If you left the hole/nuts exposed, how did you keep the hole from turning into a mini-bilge with no drain outlet?

Thanks very much in advance!

John
SV G'Ride
T37 #82
The Bobstay is a VERY important component of the rig .... ie. if you lose the bobstay, you usually see the whole rig come down.
The OEM bolting, etc. is probably 'some' hardware store 18-8 alloy, not the more sea-water compatible 316 Stainless Steel.

I feel your really have to *visualize* the embedded nuts - for material condition, to be sure that the torque that you apply is 'bolt vs. nut threads' and NOT the bolt 'dead heading' against some 'unknown' when you are torquing. I dug out and replaced the nuts because I couldnt see their condition and couldnt truly validate the torque without such visualization; PLUS, I dont like using an unknown 18-8 series nut with a 316 stainless bolt. I want 316 to be in contact with 316; and, 316 is much better in sea water. The OEM bolts are probably just a common 18-8 SS, thats probably why the corrosion.

I chiseled out all the 'mush', etc. that covered the nuts and washers (really isnt a 'bad job' if you have looooooong arms and sharp chisels, etc.), inserted new bolts/nuts/washers. I Torqued them accurately, added an additional locknut with chemical thread locker and then re-covered them with epoxy mush and then covered with several layers of FRG cloth, etc. to make a totally watertight 'seal' - as was the OEM. With a full cruising load, the bobstay fitting is mostly under water most of the time anyway.

The Baba/Panda way is better because there is nothing that approaches the simple uncomplicated 'purity' of stress transmission from a 'clevis' .... but that means a major alteration working inside of a very narrow space, a totally new connector, etc. .... and why I simply 'renovated' what I had using better sea water compatible - **316 stainless**. .... I found it simpler just to imitate/upgrade the OEM Ty37 design. Why change what works, when all you have to do is change/upgrade to a better material - 316 SS ?

best regards
RichH

Last edited by RichH; 06-10-2010 at 01:30 AM.
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Old 06-10-2010
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Nuts & bolts ?

Good question. The last reply was awesome.

I don't know exactly the original design or details of the exact setup.

It could be there are several things worth considering.
Your deal:
yes, replacing the nuts makes sense. Mostly checking them is smart. If your gonna check em, you might as well renew em?

The condition of the bolt??
Poor quality, wrong grade, electrolysis. Lots to discuss there - 'nother time.
In general, unless you know more than you've said, now would be the best time to dig in to it.
Get the old hardware off. Access the bolt holes. Check the deck for water saturation.
Check it out ( and check out what to check out), reseal the FB, confirm the structure (original design too) is cool. Get rid of the old (or at least check it), replace it with new. Good idea - in general.

Learn about sailboat decks, hardware, maint.
To me, checking out the whole deal (backing, All fasteners, integrity of the deck) would be the next step after pulling those bolts. Many reasons -.I'll skip for now.

What the yard said they'd do, how much for what, changed their story - is a problem? Save that for another day
Max
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Old 06-10-2010
jct jct is offline
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Thank you!

Thanks for the responses - I appreciate the confirmation of my "gut" instincts!

MRYBAS: the yard couldn't find replacement slotted carriage bolts so I'm switching to hex heads. I'll have to get back to you on where they came from, and maybe with the extra work involved I'll have time to find some carriage heads.

Thanks again Rich!
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Old 06-10-2010
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I used hex heads, easier to torque.

A fast internet supplier for 316 and other 'exotics' in small quantities is Stainless Steel Fasteners at Manasquan Premium Fasteners Manasquan Fasteners, Brick NJ.
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Old 06-10-2010
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Max
The Ty37 is a Taiwanese built boat ... the yard probably used mostly 'hardware store' grade of 18-8 stainless fasteners on many such applications - as do 'most' boat builders. This connection on a Ty37 holds the bobstay (end of bowsprit to near bottom of the bow at the waterline, not decks.

18-8 is VERY subject to fatigue and crevice corrosion (simultaneously). 316 is somewhat better especially for corrosion resistance. 316 is common to the chem process industry but in my mind for 'boat applications' should be mirror polished then electropolished for enhanced corrosion resistance.
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Old 06-12-2010
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Oops, thanks

Thanks. I didn't get the whole deal.
I get that I missed the boat. I get some stuff about materials (metals) and boats.
I don't get the "pollish" deal.
So....
I wanna know more.

Is the idea to treat the SS? Plate it?

To save you effort: I do get a lot about metals, boat construction, electrolysis, etc.

Thanks
Max
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Old 06-12-2010
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Most common stainless steels are prone to crevice corrosion when used in 'wetted' applications. Crevice corrosion 'starts' or propagates in 'surface irregularities' such as small cracks, machining scars, weld areas, etc. A surface that is FLAT to almost macroscopic dimensions will vastly retard the possibility of crevice corrosion.

In industry, the technical descriptions of the accepted surface 'flatness' is *5 micro-inches-Ra* and in 'laymans terms' would be a surface that has absolutely NO visible blemishes or even teeny scratches - a perfect mirrored surface.
In industry to enhance corrsion resistance stainless is finished to a VERY HIGH Quality 'mechanical buffing' to the mirror quality .... then the component is electropolished. This results in a surface that is FLAT almost to 'molecular dimensions'.

Last edited by RichH; 06-12-2010 at 10:02 AM.
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Old 06-13-2010
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Thanks

Thanks about the polish stuff.
It makes sense. Except, electropolish?
What is that? I'd like to know more.
How is it done?
Normal sailboat stuff?
Like shackles, fittings?

Question is:
when does electropolish make sense?
Is hardware sold - pre treated?
What standard is this?
Is it something to consider when buying SS hardware? Fitting manufacturer step?
I don't get it.
Thanks
Max
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