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 25-03-2019, 16:10   #1
Registered User

Join Date: Jun 2018
Location: South East UK
Boat: Prout Snowgoose 35
Posts: 18
Ply or grp for cleat backing plates

Hi, the backing plates for my cleats are currently plywood which is then glassed over underneath, making it totally encased. Over the years some of the bolts have leaked and the ply has gone soft around these bolts.

Getting them off is going to be a pig of a job so am considering what to put back. I was thinking of buying fibreglass sheet and maybe sticking a few layers together then to the hull underside but is there any advantage to using ply? I mean, itís not as if the builders were short of fibreglass supplies when they built the boat so why go to the trouble of using ply at all, particularly as they then glassed over it anyway. Is using straight GRP a bad idea? Thanks
__________________

Pugcat is offline   Reply With Quote
Old 25-03-2019, 16:30   #2
Registered User
 
zboss's Avatar

Join Date: Sep 2011
Location: On a boat
Boat: 1987 Cabo Rico 38 #117
Posts: 3,839
Re: Ply or grp for cleat backing plates

G10 FR-4 Backing plates
__________________

zboss is offline   Reply With Quote
Old 25-03-2019, 16:35   #3
Registered User
 
Spot's Avatar

Join Date: Jan 2019
Location: Minnesota, USA
Boat: 21' trailer sailor & 8' sailing dinghy
Posts: 107
Re: Ply or grp for cleat backing plates

We have 6.35mm(1/4") G10/FR4 board at work. The scrap is lovely for stuff like this...
__________________
Big dreams, small boats...
Spot is offline   Reply With Quote
Old 25-03-2019, 16:36   #4
Registered User

Join Date: Oct 2015
Posts: 1,250
Re: Ply or grp for cleat backing plates

Quote:
Originally Posted by Pugcat View Post
Hi, the backing plates for my cleats are currently plywood which is then glassed over underneath, making it totally encased. Over the years some of the bolts have leaked and the ply has gone soft around these bolts.

Getting them off is going to be a pig of a job so am considering what to put back. I was thinking of buying fibreglass sheet and maybe sticking a few layers together then to the hull underside but is there any advantage to using ply? I mean, itís not as if the builders were short of fibreglass supplies when they built the boat so why go to the trouble of using ply at all, particularly as they then glassed over it anyway. Is using straight GRP a bad idea? Thanks
Don't use fiberglass sheets, especially in a stack. They will be soft and flexible, and can crush when bolts are tightened down hard.

The BEST material by far for backing plates is called G10. It is a VERY hard glass epoxy matrix. It will not crush or rot like plywood, not corrode like metal. 1/2" thick should be about right.

It's not the cheapest stuff you can use, but you don't need a lot either.
billknny is offline   Reply With Quote
Old 25-03-2019, 18:00   #5
Registered User

Join Date: Oct 2015
Posts: 1,250
Re: Ply or grp for cleat backing plates

It's unanimous! When does that EVER happen here?
billknny is offline   Reply With Quote
Old 25-03-2019, 18:37   #6
DoÖ or do not
 
s/v Jedi's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 9,383
Re: Ply or grp for cleat backing plates

Quote:
Originally Posted by billknny View Post
It's unanimous! When does that EVER happen here?
but we can still add to it :-)

-> round the corners and taper the edges of the G10 backing plates (grind them sharp from the underside) to avoid hard spots

-> glue them with West System epoxy, filled with microfibers to a peanut butter consistency, then put a layer of fiberglass cloth and a layer of pull-ply on, wetted out with un-thickened West System.

-> if there is a plywood or balsa core, remove that around the bolt holes and cast epoxy thickened with high density filler to replace it (prevent crushing the core and prevent water getting into the core)

s/v Jedi is offline   Reply With Quote
Old 25-03-2019, 19:31   #7
Registered User

Join Date: May 2011
Boat: Hitchhiker, Catamaran, 40'
Posts: 510
Re: Ply or grp for cleat backing plates

How long did they last that way? Do this and it will be fine for the next 20 years or so: You will have to grind it all flat from underneath which will be a nasty job but quick. G-10 , can you get it where you are? Get some treated plywood scraps, (it will have a greenish tinge, find the thickest stainless steel washers that you can get, make sure that the wood is dry, over drill the holes a little, mask everything off really good, install the cleat The bolts, and the plywood backing plate all at once, smear epoxy mixed with cabosil all over everything, assemble and tighten the bolts, remove the tape. Don't forget to buy rubber gloves. As for the advantage, It is lighter and cheaper
Thumbs Up is offline   Reply With Quote
Old 25-03-2019, 20:07   #8
Senior Cruiser

Cruisers Forum Supporter

Join Date: May 2012
Location: Hailing Minny, MN
Boat: Vancouver 27
Posts: 982
Images: 1
Re: Ply or grp for cleat backing plates

Quote:
Originally Posted by s/v Jedi View Post
but we can still add to it :-)

-> round the corners and taper the edges of the G10 backing plates (grind them sharp from the underside) to avoid hard spots

-> glue them with West System epoxy, filled with microfibers to a peanut butter consistency, then put a layer of fiberglass cloth and a layer of pull-ply on, wetted out with un-thickened West System.

-> if there is a plywood or balsa core, remove that around the bolt holes and cast epoxy thickened with high density filler to replace it (prevent crushing the core and prevent water getting into the core)

Order it from McMaster Carr if you can't source it locally. It's not expensive for the amount you need.
laika is online now   Reply With Quote
Old 25-03-2019, 21:09   #9
Registered User

Join Date: Feb 2018
Posts: 320
Re: Ply or grp for cleat backing plates

Using GRP only is not a bad idea, but I would drill-fill (milled fiber)-drill.

If given the options of:
1) 1/4" G10 6in x 6in $15.85
2) 1/2" G10 6in x 6in $31.70
3) 1/2" hand layed-up fiberglass/epoxy stack, holes oversized drilled then filled with epoxy/milled fiber slurry then final hole drilled ~+/-$10

I'd choose #3 all day unless someone gifted me thick G10. With the cost savings make the plates a little larger. If you can compress a 1/2" column of hardened epoxy/milled fiber then you are doing something wrong to your bolt threads.

Let's not lose perspective and develop groupthink such that we insist that the only way to do things is the most expensive way. Stacked glass is far superior to ply and ply works (until it gets wet etc).
Singularity is offline   Reply With Quote
Old 25-03-2019, 22:06   #10
Registered User

Join Date: Apr 2007
Location: Australia
Boat: Island Packet 40
Posts: 2,328
Images: 7
Re: Ply or grp for cleat backing plates

Alloy flat bar. Cheap and easy and you don't need to glass it in.
RaymondR is offline   Reply With Quote
Old 25-03-2019, 22:26   #11
Registered User
 
Fore and Aft's Avatar

Join Date: Jan 2015
Location: Gympie
Boat: Volkscruiser
Posts: 517
Re: Ply or grp for cleat backing plates

How about the bottom of a plastic margarine container or some other disposable rectangular/circular plastic container? Whenever I had left over resin I would pour it into a plastic conatiner along with some fiberglass matt and when its cured you have a nicely moulded fiberglass backing pad that can be as thick or thin as you like. Another firm I worked at had a peice of fiberglass that was always being laid up with leftover resin and fiberglass. When it got to around half a meter square a new peice was then started again. That fiberglass sheet was always getting used for backing blocks.
Cheers
Fore and Aft is offline   Reply With Quote
Old 25-03-2019, 22:44   #12
Registered User

Join Date: Jan 2018
Posts: 409
Re: Ply or grp for cleat backing plates

Aluminum plates also work. I have marine ply and it's working fine too.
Chotu is online now   Reply With Quote
Old 25-03-2019, 23:24   #13
Registered User
 
ausnp84's Avatar

Join Date: Mar 2010
Location: UK
Posts: 405
Re: Ply or grp for cleat backing plates

Iím about to fit midship cleats and will be going down the 1/4 G10 route. Seems like solid stuff and has the advantage of not rotting anytime soon!

N
ausnp84 is offline   Reply With Quote
Old 26-03-2019, 05:28   #14
Registered User

Join Date: Jan 2018
Posts: 409
Re: Ply or grp for cleat backing plates

Quote:
Originally Posted by Chotu View Post
Aluminum plates also work. I have marine ply and it's working fine too.
Expanding on this.

The idea is you want something that will take the compression loads of the bolts and huge washers. Your backing plate is essentially an even bigger washer spreading the load out onto a greater area of the deck.

It just has to be good with compression forces. Should not be easily crushed.

It doesn't really matter if it's water resistant because you should be installing your cleats better than that.

I used untreated marine plywood 5 years ago. Not a drop of water comes in. Ever. So it's not an issue.

Use butyl tape under the cleat and tighten it down into that. You'll never have a drip.
Chotu is online now   Reply With Quote
Old 26-03-2019, 06:08   #15
Registered User
 
Bill O's Avatar

Join Date: Jul 2015
Boat: Bruce Bingham Christina 49
Posts: 542
Re: Ply or grp for cleat backing plates

Another vote for aluminum plate. Never used G10 but seems somewhat expensive compared to the 1/4" plating I can pick up as inexpensive scrap.

Don't know how long G10 has been around, but the aluminum plating has worked well for decades as backing plates for cleats, sheeting tracks, etc.


Bill O.
__________________

__________________
Bill O.
KB3YMH
http://phoenixketch.blogspot.com/
Bill O is offline   Reply With Quote
Reply

Tags
backing plates

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
Considering buying a Ply / Ply-Glass boat. What do I need to look for? PQDC Construction, Maintenance & Refit 26 25-02-2019 01:03
Grp over ply nalinjay1974 Multihull Sailboats 9 13-10-2015 11:11
The Strength of Marine Ply and Cold-Molded Ply alanvdh Monohull Sailboats 50 11-02-2011 14:42
Cleat backing plates - sturdy enough? Safari Tu Construction, Maintenance & Refit 3 26-01-2009 22:56
Marine ply VS Pressure treated ply easterly Construction, Maintenance & Refit 12 09-09-2008 11:26



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 08:09.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.