Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 01-02-2014, 17:24   #1
Registered User
 
RainDog's Avatar

Join Date: Jun 2009
Location: Varies
Boat: Pacific Seacraft 34 #142
Posts: 1,183
Plywood for core

I am rebuilding cockpit locker lids. They are about 41 x 17 inches. Thick fiberglass with a plywood core. The core got completely saturated. Is there any reason to use marine, or even exterior, ply for such an application? Or is any old 3/4 inch ply adequate. In theory it will never get wet and only needs to support the wight of a human. The glass on either side is 1/4 inch thick.
__________________

RainDog is offline   Reply With Quote
Old 01-02-2014, 17:30   #2
Marine Service Provider
 
boatpoker's Avatar

Join Date: Nov 2008
Location: Toronto, Ontario or Bahamas
Boat: Benford 38 Fantail Cruiser
Posts: 2,593
Re: Plywood for core

Quote:
Originally Posted by RainDog View Post
I am rebuilding cockpit locker lids. They are about 41 x 17 inches. Thick fiberglass with a plywood core. The core got completely saturated. Is there any reason to use marine, or even exterior, ply for such an application? Or is any old 3/4 inch ply adequate. In theory it will never get wet and only needs to support the wight of a human. The glass on either side is 1/4 inch thick.
If the plywood will never get wet, how did the old plywood get saturated ?
__________________

__________________
That hysterical laughter you hear as you sail a way in your "new" boat ..... is the seller.
boatpoker is offline   Reply With Quote
Old 01-02-2014, 17:34   #3
Registered User
 
Nicholson58's Avatar

Join Date: Jan 2011
Location: Live aboard
Boat: Camper & Nicholson58 Ketch - ROXY Traverse City, Michigan No.668283
Posts: 3,466
Images: 83
Re: Plywood for core

I use epoxy and microballoons as filler. Us Composites for both. 635 thin resin. The strength is around 3000 psi compressive and the density is about 23#/ft^3.

Fiberglass , Epoxy , Composites, Carbon Fiber - U.S. Composites, Inc.

I used this for wet deck repair of balsa and for the entire filled core of my rudder with carbon fiber skin. Rudder photos here.
Member Galleries - Cruisers & Sailing Photo Gallery

I vowed never to have to repair the same area twice
__________________
Nicholson58 is offline   Reply With Quote
Old 01-02-2014, 17:34   #4
Registered User

Join Date: Nov 2011
Location: Montegut LA.
Boat: Now we need to get her to Louisiana !! she's ours
Posts: 3,421
Re: Plywood for core

Seems to me if it got soaked once bad enough to need replacement, it will probley get soaked again! But Minuret(spl) had a real good way to make up fiberglass boards for just this type of use! look back at his rebilding post and see what he did ! sure worked for me on the deck and locker lids on the ketch we just sold!!
__________________
Bob and Connie
bobconnie is offline   Reply With Quote
Old 01-02-2014, 17:46   #5
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,365
Re: Plywood for core

The small additional price for exterior ply is worth it. I think the only difference is the glue and you want moisture resistant glue. All ply has some moisture in it, trapped in there it could be an issue.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 01-02-2014, 17:47   #6
Registered User
 
RainDog's Avatar

Join Date: Jun 2009
Location: Varies
Boat: Pacific Seacraft 34 #142
Posts: 1,183
Re: Plywood for core

Quote:
Originally Posted by Nicholson58 View Post
I use epoxy and microballoons as filler. Us Composites for both. 635 thin resin.
Sounds expensive, but I guess it is still cheaper than buying a whole sheet of marine ply.
RainDog is offline   Reply With Quote
Old 01-02-2014, 17:56   #7
Senior Cruiser
 
bletso's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Louisville, KY
Boat: Globe, cutter/ketch,38
Posts: 546
Re: Plywood for core

Quote:
Originally Posted by Cheechako View Post
The small additional price for exterior ply is worth it. I think the only difference is the glue and you want moisture resistant glue. All ply has some moisture in it, trapped in there it could be an issue.
No marine ply, in addition to the glues, has no voids between the layers. Regular exterior or interior ply can have some rather large voids between the layers. Here is a site which has some info. Marine Plywood by Homestead - Douglas Fir

Some technical specs can be found at http://plywood.boatbuildercentral.com/help.php

You should certainly be able to source marine ply in your area or up in Houston.
__________________
www.sailboatvigah.com Boats don't like being neglected, but then neither do significant others!
bletso is offline   Reply With Quote
Old 01-02-2014, 18:02   #8
Registered User
 
RainDog's Avatar

Join Date: Jun 2009
Location: Varies
Boat: Pacific Seacraft 34 #142
Posts: 1,183
Re: Plywood for core

Quote:
Originally Posted by bletso View Post
marine ply has no voids between the layers
My understanding is that is what you are paying the very steep premium for. I just cannot imagine it matters in this application, but perhaps I am wrong?
RainDog is offline   Reply With Quote
Old 01-02-2014, 18:10   #9
Senior Cruiser
 
bletso's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Louisville, KY
Boat: Globe, cutter/ketch,38
Posts: 546
Re: Plywood for core

You still haven"t answered bobconnie. How did water get there in the first place? If it happened once, chances are it will again, just maybe with the next owner.
__________________
www.sailboatvigah.com Boats don't like being neglected, but then neither do significant others!
bletso is offline   Reply With Quote
Old 01-02-2014, 18:23   #10
Registered User
 
Idylles15.5's Avatar

Join Date: Dec 2006
Location: Northport NY
Boat: Idylles 15.5
Posts: 262
Send a message via Yahoo to Idylles15.5
Re: Plywood for core

To replace core use Meranti BS 1088 marine plywood. It is made for underwater use and will not rot. It is lloyds rated and stamped. Another product would be Sapelle marine grade which also has no voids and the glue lay up used is both water proof and Boil proof. You could also try divinycell foam board, but you would have to use a thick piece to get the same rigidity. You need a rigid core in the application you are attempting to repair. Layer upon layer of glass with eventually split and crack unless you make it a half in thick, which in not only a waste of your time and materials but money too. You look at the price of a quart of West hardner and epoxy. You'll get plenty of Ideas on here, but please listen to me. You can buy a 4x8 sheet and have the remainder for future projects.
__________________
Idylles15.5 is offline   Reply With Quote
Old 01-02-2014, 18:29   #11
Senior Cruiser
 
bletso's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Louisville, KY
Boat: Globe, cutter/ketch,38
Posts: 546
Re: Plywood for core

If you use meranti, you can get partial sheets from http://www.boulterplywood.com/MarinePlywood_4.htm a 3/4 X 2 X 4 is only $44.00. I found their shipping to be very reasonable. A 2 X 4 sheet will ship UPS. They are great people to deal with.
__________________
www.sailboatvigah.com Boats don't like being neglected, but then neither do significant others!
bletso is offline   Reply With Quote
Old 01-02-2014, 18:34   #12
Registered User
 
Idylles15.5's Avatar

Join Date: Dec 2006
Location: Northport NY
Boat: Idylles 15.5
Posts: 262
Send a message via Yahoo to Idylles15.5
Re: Plywood for core

Hey Bletso
__________________
Idylles15.5 is offline   Reply With Quote
Old 01-02-2014, 18:37   #13
Registered User
 
Idylles15.5's Avatar

Join Date: Dec 2006
Location: Northport NY
Boat: Idylles 15.5
Posts: 262
Send a message via Yahoo to Idylles15.5
Re: Plywood for core

My bet would be a hinge screw hole not properly sealed or some other hardware not sealed properly
__________________
Idylles15.5 is offline   Reply With Quote
Old 01-02-2014, 18:47   #14
Registered User
 
nimblemotors's Avatar

Join Date: Apr 2011
Location: Sacramento, California
Boat: Solar 40ft Cat :)
Posts: 1,557
Re: Plywood for core

They sound very heavy. What shape, just flat rectangle? Epoxy coated wood can last a long time, but foam core can be easy to shape and lighter.
__________________
JackB
MiniMPPT Solar Controller
nimblemotors is offline   Reply With Quote
Old 01-02-2014, 18:51   #15
Registered User
 
Idylles15.5's Avatar

Join Date: Dec 2006
Location: Northport NY
Boat: Idylles 15.5
Posts: 262
Send a message via Yahoo to Idylles15.5
Re: Plywood for core

It's sold in MM thicknesses from 3mm 1/8th" to 18mm 3/4" usually 4x8 sheets, but as mentioned above you can buy partial sheets
__________________

__________________
Idylles15.5 is offline   Reply With Quote
Reply

Tags
core, plywood

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




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 01:05.


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.