Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 12-06-2019, 03:40   #16
Registered User

Join Date: May 2019
Location: Slidell, LA
Boat: ‘69 Mariner 31
Posts: 8
Re: To core or not to core?

Quote:
Originally Posted by Rex Delay View Post
You did say 1" plywood, right? To me that implies a structural member, probably a mast support bulkhead. Be very cautious in modifications, it may be a very significant structural member!
The forward section of the roof over the V berth does provide main mast support, thereís a springboard spanning the area but the plywood in that area is in decent shape and since itís separated by both head bulkheads I donít think the salon wall is contributing to the integrity of that component. My Mizzen mast is aft of the salon and separate from the salon roof. The only rig component present in the vicinity of the repair area is the main sheet anchor which is a 1/2Ē eye bolt. I will have to look a little deeper this weekend to see if there are any structural ties providing anchor support to that bolt.

The timber Mariners are an older vintage than mine, they switched to a solid hull and plywood decking after only a few of the timber versions.
__________________

SwampSailor is offline   Reply With Quote
Old 12-06-2019, 08:48   #17
Registered User

Join Date: Aug 2015
Location: Southern MD, Chesapeake Bay
Boat: Catalina & Maycraft
Posts: 970
Re: To core or not to core?

Quote:
Originally Posted by coopec43 View Post
Lots and lots of fiberglass factories have gone up in smoke!


I wouldn't dump the water on it. I have a rag as well as the bucket of water so I wet the rag in the bucket of water and lay the rag on the glassing to cool it down well before it bursts into flames. I would not do any glassing just before I knocked off for the day as I like to be there as it is curing. (maybe I am a bit too careful)


Oct 17, 2015 - A Melbourne suburb has been blanketed in toxic black smoke by a fibreglass factory blaze. The fire, which erupted on Saturday afternoon, is now under control but residents in Heidelberg West are being adv....

Oct 16, 2015 - Fibreglass factory fire in Heidelberg West. Print Email Facebook ... Black smoke billows out of a fibre glass factory ablaze in Melbourne's north.

Firefighters are dampening down hot spots after a fire at a fibreglass factory in Dunedin ...


Just do a search on "factory fire fibreglass"


https://www.heraldsun.com.au/news/na...e190167cbef230

Thanks - I'm glad you mentioned the actual fire danger of epoxy kicking off in such a way - I never knew it was possible. Very important to know...

That heavy black fiberglass smoke would make one hell of a boat fire at sea.
__________________

Hardhead is online now   Reply With Quote
Old 12-06-2019, 08:52   #18
Registered User
 
OS2Dude's Avatar

Join Date: Nov 2014
Location: Atlanta, GA
Boat: Catalina 30
Posts: 352
Images: 5
Re: To core or not to core?

From other posts I've read, they use a core between fibreglass not only for strength and lightness, but for a bit of flexibility. Solid fibreglass that is thick will break before it bends, and since a boat flexes as it goes thru a seaway, this may be an issue. Depending on size having a difference in flexibility between the cored/non-cored area may result in cracks at the interface as well.

Not to mention any differences in expansion/contraction as the boat goes through the seasons.

Good Luck.

(I'd re-bed the windows as well, silicon is at best a stop-gap for a leaking window.)
OS2Dude is offline   Reply With Quote
Old 12-06-2019, 09:58   #19
Registered User

Join Date: May 2011
Boat: Hitchhiker, Catamaran, 40'
Posts: 855
Re: To core or not to core?

1' thick ply with glass on one side is not plywood core. It is plywood with a protective glass covering. Grind out the rotten ply until you have a nice bevel (scarf) on the good ply. Make a pattern and glue (with thickened epoxy) the new ply into place. It is ok to use two 1/2", or a 3/4" and 1/4" to get your inch of thickness. The repair should be constructed just like the original only this time well coated in epoxy, No need to re-engineer one small part of the boat. It will be lighter, easier, cheaper, and correct. Any other method is just plain wrong (unless you replace the entire cabin top). You will have a nice flat plywood surface to glass onto. Check those other portlights and make sure there is no unsealed plywood endgrain anywhere. Buy a cheap Harbor Freight moisture meter and check the rest of the cabintop. Chances are that you have similar problems around all of the portlights but if you catch them in time they won't be as big of an ordeal.
Thumbs Up is offline   Reply With Quote
Old 12-06-2019, 11:26   #20
Registered User

Join Date: Dec 2014
Location: New Franklin, Ohio
Boat: Homebuilt schooner 64 ft. Sold.
Posts: 1,175
Re: To core or not to core?

You could do multiple layups spaced Three or four hours apart with no worries.
captlloyd is offline   Reply With Quote
Old 12-06-2019, 15:25   #21
Registered User

Join Date: May 2019
Location: Slidell, LA
Boat: ‘69 Mariner 31
Posts: 8
Re: To core or not to core?

Quote:
Originally Posted by Thumbs Up View Post
1' thick ply with glass on one side is not plywood core. It is plywood with a protective glass covering. Grind out the rotten ply until you have a nice bevel (scarf) on the good ply. Make a pattern and glue (with thickened epoxy) the new ply into place. It is ok to use two 1/2", or a 3/4" and 1/4" to get your inch of thickness. The repair should be constructed just like the original only this time well coated in epoxy, No need to re-engineer one small part of the boat. It will be lighter, easier, cheaper, and correct. Any other method is just plain wrong (unless you replace the entire cabin top). You will have a nice flat plywood surface to glass onto. Check those other portlights and make sure there is no unsealed plywood endgrain anywhere. Buy a cheap Harbor Freight moisture meter and check the rest of the cabintop. Chances are that you have similar problems around all of the portlights but if you catch them in time they won't be as big of an ordeal.
This was my original plan (two layers of 1/2Ē) and still the one Iím leaning towards, but had the brain storm (or other more smelly brain function) and wanted some other opinions before deciding on final path. I do like keeping things original for aesthetic purposes but if hidden by a veneer thought this might give me best of both worlds...
SwampSailor is offline   Reply With Quote
Old 12-06-2019, 20:09   #22
Registered User
 
Boatyarddog's Avatar

Join Date: Nov 2014
Location: Olympia, Wa
Boat: 1979 Mariner Ketch 32-(Oberly build) - Hull 202
Posts: 1,067
Images: 2
Re: To core or not to core?

Quote:
Originally Posted by SwampSailor View Post
The forward section of the roof over the V berth does provide main mast support, thereís a springboard spanning the area but the plywood in that area is in decent shape and since itís separated by both head bulkheads I donít think the salon wall is contributing to the integrity of that component. My Mizzen mast is aft of the salon and separate from the salon roof. The only rig component present in the vicinity of the repair area is the main sheet anchor which is a 1/2Ē eye bolt. I will have to look a little deeper this weekend to see if there are any structural ties providing anchor support to that bolt.

The timber Mariners are an older vintage than mine, they switched to a solid hull and plywood decking after only a few of the timber versions.
And again in newer versions, no plywood in cabin tops, side decks, cockpits.
Glass is laid up thick and horizontal struts glassed in under decks, handrails, ect.
Mine is a 1979, built after Far East moved to the USA.
Clair Oberly brought molds from Japan, and manufactured them in Long Beach CA.
The Mast support, transfers weight to the structural bulkheads, as well the 4 corners of the v berth, hanging locker and head.
No compression post, means these structural bulkheads must be in good shape to support the weight and tensioning of the rig.
They are pretty well made, I wouldn't want a cored deck Mariner as most of them have issues.
Also, avoid the wooden spars, unless your a shipwright, or have deep pockets.
A very seaworthy vessel for sure.
Boatyarddog is offline   Reply With Quote
Old 13-06-2019, 15:01   #23
Registered User

Join Date: Sep 2013
Location: Alert Bay, Vancouver Island
Boat: 35ft classic ketch/yawl.
Posts: 1,844
Images: 4
Send a message via Skype™ to roland stockham
Re: To core or not to core?

Yes the people who noted that 1" ply may imply that it is structural are spot on. Before deciding you need to get info about the boats design and what that peace does. 5yrs ago plywood was probably lighter, stronger, cheaper and more stable than composite that may not now be the case but you need to know the engineering requirement of the section before being able to replace it with a different structure.
__________________

roland stockham is offline   Reply With Quote
Reply

Tags
core

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
To balsa core or not to balsa core? fbchristo Multihull Sailboats 135 04-02-2009 15:13
different core types (foam pvc, divinicell vs balsa) schoonerdog Multihull Sailboats 56 22-07-2008 09:56
Bowsprit area core delamination / rot / wet MV Construction, Maintenance & Refit 5 26-09-2007 07:27
Cape Lookout via Core Sound ??? Kokomo36 Sailor Logs & Cruising Plans 2 10-10-2006 05:46

Advertise Here


All times are GMT -7. The time now is 11:09.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.