G10/FR4 Fiberglass Board vs Steel marine enviroment

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SUMMARY

The discussion focuses on the suitability of using 1/2" G10/FR4 fiberglass board as a replacement for decaying 1/4" low carbon steel backing plates in a 28-foot sailboat hull. G10/FR4 offers superior resistance to decay compared to carbon steel, making it an ideal choice for marine environments. The material's bonding capabilities to the fiberglass hull enhance load distribution, while its mechanical properties, such as tensile strength of 40,000 PSI and compressive strength of 60,000 PSI, provide structural integrity. Concerns regarding the potential for bolts to rip through the G10 material compared to steel are discussed, with suggestions to increase thickness for added strength.

PREREQUISITES
  • Understanding of G10/FR4 fiberglass properties
  • Knowledge of marine construction materials
  • Familiarity with load distribution principles in boat design
  • Basic understanding of tensile and compressive strength metrics
NEXT STEPS
  • Research G10/FR4 fiberglass specifications and applications in marine environments
  • Explore bonding techniques for G10/FR4 to fiberglass hulls
  • Investigate mechanical load calculations for backing plates in boat construction
  • Learn about alternatives to G10/FR4 for marine applications, such as other composite materials
USEFUL FOR

Boat builders, marine engineers, and DIY boat repair enthusiasts looking to enhance the durability and performance of their vessels through material upgrades.

sweeneyman
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I was wondering if anyone knew of the potential downsides of using this material to replace a piece of 1/4 low carbon steel that is decaying and is a backing plate inside a hull of a 28 foot sailboat. I would be replacing it with 1/2" G10/FR4 fiberglass board minimum and could go to 3/4 inch if necessary. The size is a triangle approximately 2 feet on all 3 sides. This would be a backing plate to a bowsprit with anchor roller and attachment for the fore stay. This material will bond nicely to the hull which I believe will help distribute the loads. Any help would be appreciated. I was trying to compare on matweb.com but I'm out of my league on this.
 
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I have seen and heard of many uses like this for transoms and critical parts of boats in the past. G10 fr4 materials are a good fit in this application, IMHO, because the materials itself is made up of layers of fiberglass as most boats are. I don't think the the g10 material will decay as much as the carbon, the carbon does have a higher " organic " content whereas g10 seems to be completely synthetic ... however, I am no expert, just an observation. I did a little research and this site http://www.g10fr4.com actually has a chemical resistance chart on it that lists salt water as " no effect on this material " . I hope that helps.


Schrödinger's cat is live and dead ...
 
I agree with Schrödinger's point about decay which is G10 best asset as I can bond it to the rest of the fiberglass hull quite easily. This will increase its bond to the hull over that of the steel. My other concern is would a bolt and washer be more likely to rip through this material than 1/4 steel or is it more likely to bow or snap and would doubling or tripling the thickness make up for any loss? Thanks for the help


PROPERTY
DATA AREA OF
DATA G10 FR4 SHEET,
PANEL, BOARD MATERIAL
PER MIL I 27648 / 27 TPE GEE F
TENSILE LENGTH-WISE 40,000 PSI
CROSS-WISE 35,000 PSI

COMPRESSIVE
STRENGTH FLAT-WISE 60,000 PSI
EDGE-WISE 35,000 PSI

FLEX
STRENGTH CROSS-WISE 45,000 PSI
LENGTH-WISE 55,000 PSI

MODULUS OF
ELASTICITY IN FLEX LENGTH-WISE 2,700,000
CROSS-WISE 2,200,000
SHEAR STRENGTH 19,000

IZOD
IMPACT NOTCH 7
NOTCH 5.5
ROCKWELL HARDNESS (M) 110
SPECIFIC GRAVITY 1.82

WATER
ABSORPTION .062 " THICK .25 % OVER 24 HOURS
.125 " THICK .15% OVER 24 HOURS
.500 " THICK .10 % OVER 24 HOURS

DIELECTRIC CONSTANT .062 " THICK 500 VOLTS PER MIL
.125 " THICK 400 VOLTS PER MIL

DISSIPATION
FACTOR CONDITION A .025 MEGACYCLE

INSULATION
RESISTANCE 96 HOURS AT 90% RELATIVE HUMIDITY 200000 MEGA OHMS
FLAME RATING UNDERWRITER LABS UL94V-0
OPERATING
TEMPERATURE CONTINUOUS 285°F TO 210° KELVIN
COEFFICIENT of THERMAL EXPANSION CM/CM/DEG C X -5 0.9
BOND STRENGTH GREATER THAN 2,500 LBS
 

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