Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 22-05-2007, 16:48   #16
Registered User
 
Thermal's Avatar

Join Date: Jul 2005
Location: Honolulu
Boat: S2 11.0C 36' Puka Wai
Posts: 157
Images: 1
Quote:
Originally Posted by Ex-Calif
As far as the side loading, don't all designs have to transfer the lateral loading into the structure somehow? I am having a hard time visualizing and "external" chain plate but I am guessing it is attached to the side of the hull and the attach point for the shroud sticks up above the deckline?
This is true, but the chainplates are usually attached to some sort of bulkhead or reinforced area of the hull, that way the side load is spread out over a much larger portion of the hull.
Refabricating the failed piece is of course feasible, but you have to have confidence in the skill of the welder since all of the shroud tension is going through the weld, and the weld is also the first place corrosion will start.
__________________

__________________
In theory, Practice and Theory are the same. In practice, they are not.
Thermal is offline   Reply With Quote
Old 22-05-2007, 19:11   #17
Senior Cruiser
 
delmarrey's Avatar

Cruisers Forum Supporter

Join Date: Mar 2003
Location: Now in Blaine, WA
Boat: Modified Choate 40
Posts: 10,702
Images: 122
Just to add more info to the discussion.

If one attaches chain plates to the side of the hull, it'll need to be a solid glass hull. A cored hull, the holes will elongate without some extra work to the hull.

If it were mine and wanted to put bolts thru the hull I would have backing plates secured to the hull and/or carbon-fiber/Kevlar laminated to the hull to strenghten the thru holes.

You were lucky to get 25 years out of that design. Mine have been in place for 26 years. I do an inspection on mine at least once before the first sail of the year.

BTW some of the smaller trailerable sail boats the chain plates are only secured to the deck.

Gord, you are right! A clevis would not be the cheapest. I keep forgetting we're not all Machinists with the tooling.
__________________

__________________
delmarrey is offline   Reply With Quote
Old 22-05-2007, 20:31   #18
Registered User
 
Terra Nova's Avatar

Join Date: Apr 2007
Location: Marina del Rey, California
Boat: Freya 39 cutter- Terra Nova
Posts: 3,645
Quote:
Originally Posted by Ex-Calif
Thanks for all the inputs. I have received a reply back from someone I have been told my several sources is a "maxi expert" and he advises the chain plates are not stocked as spare parts by anyone and so they have to be made.

BTW - At least one person has told me not to use stainless but to use high alloy/high tensile steel.

Thoughts?
Yo Ex,

at least one person has suggested having a professional do this. This is just not an area for a do-it-yourself experiment.

best, andy
__________________
1st rule of yachting: When a collision is unavoidable, aim for something cheap.
"whatever spare parts you bring, you'll never need"--goboatingnow
"Id rather drown than have computers take over my life."--d design
Terra Nova is offline   Reply With Quote
Old 22-05-2007, 23:30   #19
Moderator Emeritus
 
Ex-Calif's Avatar

Cruisers Forum Supporter

Join Date: May 2007
Location: Singapore
Boat: Maxi 77 - Relax Lah!
Posts: 11,514
Images: 4
"at least one person has suggested having a professional do this. This is just not an area for a do-it-yourself experiment."

Thanks for the tip. Actually any change to the existing design is an experiment I would say. Don't worry I don't plan on welding these up myself although in my hands on days I was a decent welder certified in oxy acetylene and TIG.

Actually, there has been several bits of conflicting advice. From external chain plates to carbon fiber ones. As an engineer with 25 years experience it would be dumb of me not to ask questions and get some opinions.

There have been a lot of opinions for which I am very grateful. At the end of the day, I have to take all the inputs and make the decision myself.

The failure point is clearly the ring that is welded to the chain plate. Corrosion was a significant factor. The deck and hull are in perfect shape. No signes of stress or cracking. If I have a new chain plate built with a thicker ring and get 30 years out of it, that'll do me ;-)

Delmarrey & Thermal - Regarding the hull strength take another look at the cross section drawing. The rail is solid and is about 1 inch thick. There are 4 through bolts and a backing plate. I could extend the backing plate or improve the connection to the deck but in reality I probably want that fitting to fail before the deck lifts off the boat...

Thanks again for all the great input. I called my mechanic and he is started on the new plates. I told him to upsize the rings one size and let me see the pieces before welding.
__________________
Relax Lah! is For Sale <--- Click
Click--> Custom CF Google Search or CF Rules
You're gonna need a bigger boat... - Martin Brody
Ex-Calif is offline   Reply With Quote
Old 23-05-2007, 00:06   #20
Senior Cruiser
 
delmarrey's Avatar

Cruisers Forum Supporter

Join Date: Mar 2003
Location: Now in Blaine, WA
Boat: Modified Choate 40
Posts: 10,702
Images: 122
I think the real culprit was the fact that the lower bracket was sealed in glass and from the air. Lack of air is one of SS worst enemy. Add a little water and it's off and running. You may want to keep it exposed to keep an eye on it. Have you check for cracks in the upper bracket?

As far as the upper bracket, making it any bigger wouldn't make any difference IMO. It would be nice if it were a "T" rather then an "L". It would give it more surface area against the under side of the deck.

I'll bet everyone now is running out to check their own chain plates!
__________________
delmarrey is offline   Reply With Quote
Old 23-05-2007, 04:57   #21
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,579
Images: 240
Chainplate Scantlings:
This table, from ”Skene’s Elements of Yacht Design” is a handy reference for sizing chainplates and tangs:
Goto:
http://www.cruisersforum.com/gallery...1325&catid=500
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 23-05-2007, 05:47   #22
Moderator Emeritus
 
Ex-Calif's Avatar

Cruisers Forum Supporter

Join Date: May 2007
Location: Singapore
Boat: Maxi 77 - Relax Lah!
Posts: 11,514
Images: 4
That is a very handy reference. Thanks!

I am hoping we end up with something as nice as this.
Attached Thumbnails
Click image for larger version

Name:	ronstan deck eye.jpg
Views:	131
Size:	57.0 KB
ID:	1180  
__________________
Relax Lah! is For Sale <--- Click
Click--> Custom CF Google Search or CF Rules
You're gonna need a bigger boat... - Martin Brody
Ex-Calif is offline   Reply With Quote
Old 23-05-2007, 07:24   #23
Registered User
 
capt lar's Avatar

Join Date: Feb 2005
Location: Cape Cod
Boat: currently "on the beach"
Posts: 729
Images: 12
__________________
Larry

We have met the enemy and he is us. - Walt Kelly
capt lar is offline   Reply With Quote
Old 23-05-2007, 07:28   #24
Registered User
 
capt lar's Avatar

Join Date: Feb 2005
Location: Cape Cod
Boat: currently "on the beach"
Posts: 729
Images: 12
Hey ! My PhotoBucket talents are improving !
Above is a photo of the config on my Bristol. To get the extra berth, same condition with change of angle. Note the transfer of loads down, but inward. The hardware is heavy and no sign of cracks, but it is a spot to watch. Most common issue is leaks where passes through deck since it is not a straight pull.
__________________
Larry

We have met the enemy and he is us. - Walt Kelly
capt lar is offline   Reply With Quote
Old 23-05-2007, 18:33   #25
Registered User

Join Date: Jun 2006
Posts: 559
i would agree with Gord May. and move the plates through bolted to the outside. if your plates/half round rods are located at or near the toe rail, and your hull is not cored that is what i would do. all you would have to do for the shroud and stay angles is bent the upper part of the plate to match the shroud/stay angle, through bolt to the hull sides and you are done. this also allows you to keep an eye on every part of your plates and bolts to a lesser degree. any rust stains and you know you have to get to work. from the pics from what i can see they should have been attended to some time ago. i see alot of rust stains on the glass surrounding to hole in tohe deck.
__________________
mike d. is offline   Reply With Quote
Old 24-05-2007, 22:01   #26
Senior Cruiser
 
delmarrey's Avatar

Cruisers Forum Supporter

Join Date: Mar 2003
Location: Now in Blaine, WA
Boat: Modified Choate 40
Posts: 10,702
Images: 122
Here's a sample of strong inboard chanplates secured with 1/2" bolts.
Attached Thumbnails
Click image for larger version

Name:	chainplate1.JPG
Views:	126
Size:	67.5 KB
ID:	1188   Click image for larger version

Name:	chainplate2.JPG
Views:	126
Size:	76.2 KB
ID:	1189  

__________________
delmarrey is offline   Reply With Quote
Old 04-06-2007, 22:21   #27
Moderator Emeritus
 
Ex-Calif's Avatar

Cruisers Forum Supporter

Join Date: May 2007
Location: Singapore
Boat: Maxi 77 - Relax Lah!
Posts: 11,514
Images: 4
New chain plates are installed and we are back in business. I will post photos next week for anyone interested. Went a size up on the plate and the u-bolts and it is "much" beefier loooking now.

Backstay brackets are being manufactured as we speak.
__________________
Relax Lah! is For Sale <--- Click
Click--> Custom CF Google Search or CF Rules
You're gonna need a bigger boat... - Martin Brody
Ex-Calif is offline   Reply With Quote
Old 06-04-2016, 11:36   #28
Registered User
 
Tuxie's Avatar

Join Date: Apr 2016
Location: NJ/NY
Posts: 13
Re: Failed Shroud Deck Plate

Sorry for reviving old thread but do you happen to have those promised photos? (:

I bought Maxi 77 which happens to be my first sailboat and when I bought it it had half a meter snow on top of it so didn't get to see the deck... Now that snow has melted I transported the boat to my home town I was able to inspect the boat better and found interesting surprise. The chain plates have been converted so that there's no connection to the hull anymore but rather somewhat bigger chain plates.. However they happen to be made of normal iron which has rusted almost completely through.. It seems to be have something like 3cm thick metal originally but now it's at most 1cm thick.

It would be interesting to see what's the original and designed setup for Maxi to restore that. Especially as another side of the deck around the chain plate seems to have fractures in the fiberglass meaning I'll have some fun fiberglass work to look forward to.
Attached Thumbnails
Click image for larger version

Name:	20160405_191527.jpg
Views:	49
Size:	404.1 KB
ID:	122091  
__________________

__________________
Tuxie is offline   Reply With Quote
Reply

Tags
shroud

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
Characteristics of a Circumnavigating Cat Stella Polaris Multihull Sailboats 562 07-12-2015 13:56
Teak Deck Mercator Construction, Maintenance & Refit 10 26-05-2011 21:01
What is the Advantage of a Keel Stepped Mast? 44'cruisingcat Monohull Sailboats 44 01-12-2006 19:18
Missing Chainplate Deck Covers alanperry Construction, Maintenance & Refit 1 02-08-2006 15:45



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 21:57.


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.