Mooring Cleat Backing Plate Installation - SailNet Community
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post #1 of 12 Old 06-19-2013 Thread Starter
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Mooring Cleat Backing Plate Installation

Planning on adding backing plates to the bow cleats on my Catalina 27. Bought some stainless steel stock (1 1/2 flat bar 3/16 inch thick) and had a friend cut, drill, bevel, and grind into some pretty nice and heft backing plates. Current plan is to:

1. Wax backing plate (hull side) with mold wax or similar
2. Apply 3M 4200 to the waxed (hull side) backing plate to provide an even surface to distribute load in lieu of bumpy/uneven fiberglass
3 Seal cleat/deck joint with polysulfide (LifeSeal/LifeCaulk), etc.; interior joint remains unsealed so leaks can be seen
4. Join with stainless screws, washers, and locknuts


Is 4200 a reasonable backing material for the backing plate where it means the somewhat uneven hull? 5200 seems to permanent as does the microballoon filled epoxy recommended by the Practical Sailor article.

Josh
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post #2 of 12 Old 06-19-2013
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Re: Mooring Cleat Backing Plate Installation

4200 is a pretty flexible adhesive and will not alleviate point loading. A better approach would be using something like West epoxy instead. Make sure you clean the bonding area really clean with acetone. You can use either mold release agent (wax) or bond the SS directly to the boat. I’ve done this but using G-10 instead of SS. Caulk in the regular fashion or use butyl rubber.

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post #3 of 12 Old 06-20-2013
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Re: Mooring Cleat Backing Plate Installation

The thing I don't understand about bonding the backing plate to the boat, is that it is then is part of the deck. So if my deck was orignally built twice as thick as another guy's deck, would I even need to use backing plates? I guess I assumed that the function of backing plate requires just a little bit of movement.

I agree, epoxy with a releasing agent would be my choice (if an uneven surface).

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post #4 of 12 Old 06-20-2013
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Re: Mooring Cleat Backing Plate Installation

Definitely use thickened epoxy to bed the plates. Simply wrap the backing plate with packaging tape - the clear stuff. It releases very well and when you peel it off - voila, the plate is as it was when you started.

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post #5 of 12 Old 06-20-2013
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Re: Mooring Cleat Backing Plate Installation

Seems thickened epoxy would level it very well, and release agent on the backing plate would keep it from permanently attaching the backing plate. As far as sealing the top side, I would go with butyl tape as the seal will last and easy 40 years before it will need to be redone. I am all about doing it once and then sailing, not having to do it again. Also Butyl is likely cheaper than caulk anyway.
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post #6 of 12 Old 06-20-2013
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Re: Mooring Cleat Backing Plate Installation

First

3) Great - definitely don't seal on the inside! But why not use butyl tape?

But second, why a backing plate at all?

When there are excess forces something's got to give. If the deck is sound decent sized trailer washers, 1.5" for example (perhaps with a smaller washer in addition), are going to transfer the load adequately. I'd be shocked to find that good trailer washers couldn't transmit enough force to deform the entire fordeck deck structure. Once you've reached that point what's a backing plate going to add?

Not to mention that the forces on a cleat are sideways, not up (I assume you're not lifting the boat with your cleats!). In this case the adhered backing plate makes a little bit of sense - it will actually resist the shearing force - but it's on the wrong side of the deck to do this properly. The bolts could still, under excess force, drag through the top fiberglass layer.

Personally the reasoning behind backing plates has just never checked out in my mind. I can't say a backing plate can hurt (unless it covers up existing problems), but I don't see it making anything better, and it comes with a lot of excess work.
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post #7 of 12 Old 06-20-2013
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Re: Mooring Cleat Backing Plate Installation




My large mooring bit was hollow with perhaps a 3/8 lip around the edge and it was compressing the glass and cutting into the deck

After the plates no issues at all with movement

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Re: Mooring Cleat Backing Plate Installation

Quote:
Originally Posted by tommays View Post

My large mooring bit was hollow with perhaps a 3/8 lip around the edge and it was compressing the glass and cutting into the deck

After the plates no issues at all with movement
In a cleat application the top plate makes a lot more sense to me. And clearly with that type of height there is a lot of leverage for an edge or corner to dig in.

But for example in your case I see little to be gained by adding a plate on the back. Did you have one?
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Re: Mooring Cleat Backing Plate Installation

Yes i just made a few drawings and gave them to the waterjet guy






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post #10 of 12 Old 06-20-2013 Thread Starter
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Re: Mooring Cleat Backing Plate Installation

Thanks for all of the input.

If the underside surface of the deck isn't too irregular, could one get away with not using epoxy at all?

SloopJonB: The packing tape idea is pretty clever and easier to source than mold wax

BTW, the rationale for the addition of the backing plates is:
1. A bow cleat is loose and I have to remove the v-berth cabinetry anyway

2. Catalina recommends adding backing plates as their 1.5" washers originally used can sometimes cause spider cracking

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