Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 01-12-2014, 23:19   #1
Registered User

Join Date: Oct 2012
Posts: 19
Replacement of the Chainplate System

Hello,

I removed one upper chainplate from my 29' boat. The original setup had the chainplate embedded in fiberglass. The chainplate would make a couple of near 90 degrees turns (reinforced with a welded steel at at the bend) and exit through the deck.

My original plan was to reinforce the hull a bit, make a G10 knee and strongly attach it to the hull (heavy tabbing + bolting every 2 inches).

I did most of the prep work including filling the slot on the deck and drilling at a 90 degree angle from the original slot for the new chainplate (1/4"x1.5")

However I am now worried that the system might be undersized for the upper shroud even though the length of the new chainplate is slightly longer than in the original setup. I am concerned about the moment of force on the knee.

Anyone has an idea?

Thanks.
Florent
Attached Thumbnails
Click image for larger version

Name:	chainplate.jpg
Views:	264
Size:	19.6 KB
ID:	92720  
__________________

__________________
flo617 is offline   Reply With Quote
Old 02-12-2014, 04:39   #2
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,018
Re: Replacement of the Chainplate System

Why did you want to change from what the builder had done originally?
__________________

__________________
transmitterdan is offline   Reply With Quote
Old 02-12-2014, 08:47   #3
Registered User

Join Date: Oct 2012
Posts: 19
Re: Replacement of the Chainplate System

Because I was not sure about the state of the original chainplates since I could not inspect them. In order to pull one out I had to cut it.

The original chainplate had a sharp "S" shape and welding to reinforce it. Making an exact copy might be a little difficult.

I have not heard of anyone replacing a glassed in fiberglass chainplate with another glassed in fiberglass chainplate and I was under the impression fiberglassing chainplate had been abandonned because of the issues of water getting trapped, corrosion, fiberglass delam etc...

By the way, the original design had a different main bulkhead position and a different set of attachement (with chainplates onto knees and the upper on the bulkhead)
__________________
flo617 is offline   Reply With Quote
Old 02-12-2014, 09:13   #4
Registered User
 
Suijin's Avatar

Join Date: Feb 2013
Location: Annapolis MD; currently in Oriental NC
Boat: Valiant 40
Posts: 2,880
Re: Replacement of the Chainplate System

Can you expand a little bit on your new construction? As I understand it, you fabricated a new G10 knee and glassed and bolted it to the hull. From your diagram it looks like the new plate is oriented fore and aft, and that you plan to through bolt it, through the knee, to the hull. Is this correct?

I'm not an engineer but I'll hazard a guess that a 14" chainplate bolted every 2" is going to be more than adequate for a 30' boat, provided that the hull and knee are themselves sound/thick enough.
__________________
Suijin is offline   Reply With Quote
Old 02-12-2014, 09:28   #5
Registered User

Join Date: Jun 2006
Posts: 558
Re: Replacement of the Chainplate System

Depending on your hull thickness at the attachment point adding glass to relieve the localized stresses makes sense! Our boat if a GulfStar 37, and that is what GulfStar did. If you have the thickness you can use carriage head bolts at the attachment points. You would drill your holes for the shank diameter of the bolt, then file in the square for the head. I just replaced ours after 35 yrs. and found only 2 out of 30 that had any corrosion under the heads. This appeared due to lacking the needed amount of polysulfide bedding compound. As to the thickness of the plate 1/4 by 1.5 is more than adequate, I would think, as our lowers are the same as what you intend to use. Also note GulfStar only used 4 bolts per plate for a 12 inch exposure under the deck. If you have ceiling going over the plates it would be advisable to put inspection plate cutouts over the plates.
__________________
mike d. is offline   Reply With Quote
Old 02-12-2014, 09:56   #6
Registered User

Join Date: Oct 2012
Posts: 19
Re: Replacement of the Chainplate System

I have not glassed any piece yet. When I said I was done with the preparation, I merely meant that I had sanded the paint off a considerable section around the area and ground the corner around the pocket where the chainplate was glassed in in order to smooth it out.

I want to do all the fiberglassing in one or two days in order to get the best bonding possible.

I did get a piece of G10 roughly cut to fit (need to get a better cutting tool) but have not ordered the chainplate yet, just made a wooden mock version.

I'm assume "fore and aft" means the chainplate is essentially parallel to the hull but actually what I was thinking of doing is to glass in the knee perpendicular to the length of the boat (like a stringer or a bulkhead). That way the position of the shroud attachement would match the original one exactly while the chainplate would remain straight.

In other word the diagram I have uploaded shows a transversal cut of the boat, with the interior on the right and the endless blue ocean on the left.

I would be happy to consider other solutions. I have thought of going external, especially since the spreader is basically an aluminum tube with a probably standard size but I would rather consider an option that keeps the sheeting angle range intact.
__________________
flo617 is offline   Reply With Quote
Old 02-12-2014, 18:12   #7
Registered User

Join Date: Jun 2006
Posts: 558
Re: Replacement of the Chainplate System

I agree with you on the shroud, chain plate, G10 angle!. When I did mine, new chain plates, I talked to people in the know at the yards, you can bend the exposed chain plate to match the shroud angle, as it clears the deck surface. This relieves the shear forces on the pin, as the angles all line up. Full contact. Make sure you fill the cavity around the plate well with polysulfide. If you have beauty rings that go over the top of the plates, I would put some butyl tape under the covers, and let it squeeze out on top. this will stop any water intrusion of the poly.
__________________
mike d. is offline   Reply With Quote
Old 03-12-2014, 11:54   #8
Senior Cruiser
 
roverhi's Avatar

Cruisers Forum Supporter

Join Date: Aug 2005
Location: Kona, Hawaii, Carlsbad, CA
Boat: 1969 Pearson 35 #108 & 1976 Sabre 28
Posts: 6,003
Send a message via Yahoo to roverhi
Re: Replacement of the Chainplate System

Use epoxy to laminate/bond the knee to the hull. Would make the length of the knee bonded to the hull about 1 1/2 times the length of the chain plate. Run the bonding out about a foot from the knee and taper successive layers. Probably at least 4 layers. That's the way my chain plates were done by the mfg 45 years ago. Seems to worked fine.
__________________
Peter O.
'Ae'a Pearson 35
roverhi is online now   Reply With Quote
Old 03-12-2014, 12:10   #9
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,342
Re: Replacement of the Chainplate System

So you are saying the original builder bent the chainplate nearly 90 degrees and then welded it? (Probably because it started to crack at the bend...?) Good thing you are re-doing them!
I'm not sure I totally understand what you are doing. But your pic indicated to me that you are putting the new chainplate inside the hull and spacing it out with G10 between the hull and the chainplate...?
I see no problem with that. 1.5 x 1/4 chainplate is probably a bit smaller than I would go on a 30 foot boat.... but is likely big enough... I've seen bigger boats with smaller cross section. The weak point is the amount of material from the edge of the bolt hole to each side.
So if you are using 3/8 bolts; 1.5 minus .375 = 1.12 x .25 thick = .28 cubic inches cross section outside the hole. If the yield strength of the SS is say.... 35 ksi, then the chainplate is good for about 9800 lbs force with no safety factor.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 05-12-2014, 02:04   #10
Registered User

Join Date: Oct 2012
Posts: 19
Re: Replacement of the Chainplate System

9800 That's 1400 more than the official displacement.

Here is the chainplate, I cut it just before it angled out through the deck. There is a 45degree steel plate welded to reinforce the chainplate at the bend.

The anchors are smaller squares welded to the sides of the plate.
Attached Thumbnails
Click image for larger version

Name:	chainplate_pic.jpg
Views:	122
Size:	41.2 KB
ID:	92995  
__________________
flo617 is offline   Reply With Quote
Old 05-12-2014, 10:16   #11
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,342
Re: Replacement of the Chainplate System

ahh... I think I understand... so the little squares were glassed to the hull and the gusset/90 degree turn was up under the deck...?
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 05-12-2014, 11:01   #12
Registered User

Join Date: Oct 2012
Posts: 19
Re: Replacement of the Chainplate System

Correct
__________________
flo617 is offline   Reply With Quote
Old 13-12-2014, 11:34   #13
Registered User
 
Boatyarddog's Avatar

Join Date: Nov 2014
Location: Olympia, wa.
Boat: Mariner Ketch 32- 1979- hull 202
Posts: 632
Re: Replacement of the Chainplate System

Beef up the attachment point before placing the chain plate, and dry fit the piece you're going to fabricate in place.


Sent from my iPad using Cruisers Sailing Forum
__________________
Boatyarddog is offline   Reply With Quote
Old 13-12-2014, 11:41   #14
Registered User
 
Boatyarddog's Avatar

Join Date: Nov 2014
Location: Olympia, wa.
Boat: Mariner Ketch 32- 1979- hull 202
Posts: 632
Re: Replacement of the Chainplate System

Chainplates glassed to the hull aren't going to be the best in terms of holding power.
I'd do a build up of the areas of attachment, the hull.
And through bolt the Chainplates to the hull.
If the tang of the new Chainplates extends through the deck, be sure to install a crib plate around the tang.
Or it will break the seal to the deck as everything flexes with stress and temp.variations.



Sent from my iPad using Cruisers Sailing Forum
__________________
Boatyarddog is offline   Reply With Quote
Old 13-12-2014, 11:51   #15
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 17,032
Re: Replacement of the Chainplate System

Actually I believe if it's done properly glassing into the hull is the strongest possible way, of course the drawback is possibly very difficult to impossible to inspect and difficult to replace. I believe a glassed in Ti chainplate is the best possible?
__________________

__________________
a64pilot is offline   Reply With Quote
Reply

Tags
chainplate

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Chainplate Replacement Advice tominny Deck hardware: Rigging, Sails & Hoisting 18 25-01-2014 22:38
Source for Chainplate replacement Kindle Deck hardware: Rigging, Sails & Hoisting 1 04-06-2012 08:01
Luders 33 Chainplate Replacement nv5l Deck hardware: Rigging, Sails & Hoisting 19 05-07-2011 12:46
Chainplate Replacement sabray Construction, Maintenance & Refit 23 25-03-2010 19:21
Chainplate Replacement Material? malbert73 Deck hardware: Rigging, Sails & Hoisting 3 02-05-2009 05:33



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 18:42.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.