Backing plates

tsmyth

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From time to time there is a discussion involving the use of backing plates. Is there a rule of thumb for how large a backing plate should be? For instance, U bolts often come with a small backing plate, and penny washers are sometime used, but are thees adequate?

Ray
 

William_H

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And how long is a piece of string anyway?
Hi ray
You have to consider the thickness and strength of the material (fibreglass) you are attaching to. Probably for most applications where you are trying to stop a nut pulling through the glass the penny washer is fine however while it may stop the nut pulling through, the whole area of deck may still flex and require additional support right out to the gunwhale or at least over a large area.
You should be out on the LBG today or is it too cold? We have last scheduled summer race today ( a bit sad).
Winter arrived on Thursday with 18 max. Was out twilight sailing the night before it was warm and pleasant. In fact only 10 days earlier we had a 42 max I hate winter. regards olewill
 

boatmike

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Depends entirely on what loads you intend to apply and what the hull section is. If its a thick cored laminate its more important to have spacers to stop the core collapsing. A thin laminate will require more reinforcement that a thick one. There is no general rule.
 

dickh

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I always use ply backing boards of about ½" to ¾" thick. Foe example, I will be fitting 'U' bolts for harness points in the cockpit and replacing the jackstay 'U' bolts(they are only about 5mm Ø). I have made up pads about 5" x 3" x ¾" thick with a couple of coats of varnish. I also use penny washers under the nuts.
 
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