Backing plate
Distributing the load.
The backing plate is bonded or fastened against the inner hull face, distributing the clamping load of the backing nut across a wider area to prevent localised hull distortion or delamination. Without a properly sized backing plate, the point load from the nut can crush or crack the hull laminate over time.
Material selection should be matched to the hull construction — GRP or marine plywood for fibreglass hulls, aluminium for metal hulls. The bore diameter must match or clear the skin fitting spigot diameter, and the surface finish must be compatible with both the hull laminate and the bedding compound.
| Property | Description |
|---|---|
| Material | GRP, marine ply, aluminium, or carbon fibre matched to hull construction |
| Length / Width | Plan dimensions of the plate |
| Material thickness | Load-bearing thickness |
| Bore diameter | Must match or clear the skin fitting spigot diameter |
| Surface finish | Compatible with hull laminate and bedding compound |
Backing plate condition should be assessed at each haulout. In fibreglass hulls, look for delamination, cracking, or water ingress around the plate edges. A compromised backing plate undermines the entire through-hull assembly — even if the skin fitting and seacock are in perfect condition.
Data points
Status Values
| Value | Type |
|---|---|
| Service events | |
|
Last Inspection date
Date of the most recent inspection performed.
|
Lifecycle |
Property Values
| Value | Type |
|---|---|
| Construction | |
|
Part No.
Part Number.
|
Attribute |
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Surface Finish
Surface treatment or finish type.
|
Attribute |
| Dimensions | |
|
Length (L)
Length of item.
|
Measure |
|
Width (W)
Width of item.
|
Measure |
|
Diameter (D)
Diamater of the item.
|
Measure |
|
Material thickness
The thickness of construction material of an item.
|
Measure |
|
Bore diameter
Internal diameter of the fitting — critical for flow calculations of water, air or other gases and fluids.
|
Measure |
| Lifecycle events | |
|
Disposal Date
Date when the item was permanently removed or decommissioned.
|
Lifecycle |
|
Purchase date
Date item was purchased.
|
Lifecycle |
|
Decommissioning date
Date item was decommissioned.
|
Lifecycle |
|
Installation date
Date the item was installed. Note this may be a different date to the commissioning date.
|
Lifecycle |
| Other | |
|
Material
Material
|
Attribute |