How much deflection is normal in Fiberglass Deck

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halsteadmorris

Seaman Apprentice
Joined
Mar 10, 2021
Messages
41
Hello, all!

I purchased a wellcraft 2002 22WA about 6 months ago. This is my first fiberglass boat, but I have been around boats for years.

I’ve noticed a small amount of bounce in the middle of the floor by the stern. It’s not noticeable unless you are feeling for it. I do not see any support underneath this section.

I know what is too much flex/sponginess in a boat, but I’m not sure what would be considered normal? Absolutely solid as a rock no give whatsoever? Or is a slight amount of deflection in the center of the floor normal on some models?

The stringers on this boat are foam so I am not worried about damage to them.

I appreciate all the input. Thanks
 
M

MikeSchinlaub

Senior Chief Petty Officer
Joined
Jan 14, 2025
Messages
787
If it's a deck like this internet pic...
wellcraft-22wa-1597147-330882986.jpg

Then I would expect it to be pretty solid. Is this soft spot in the panel over the gas tank?
 
Texasmark

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,975
Probably, being over the tank, and being a cover probably some flexing would be assumed as there probably isn't much reinforcing. The question I would ask myself would be: Does it matter if it caves in a little under weight? Probably not. Maybe you would stand on the cover and bend your knees and then straighten out your legs rapidly a few times in succession. Listen for cracking noises. If it doesn't flex that much...3/8" for a number, and doesn't make a crackling noise when you exercise it then I wouldn't worry about it. If it does deflect/crackle, I'd glass in some reinforcing horizontal multiple ply plywood (cabinet grade) strips, 2 or 3 and be done with it.
 
H

halsteadmorris

Seaman Apprentice
Joined
Mar 10, 2021
Messages
41
Texasmark said:
Probably, being over the tank, and being a cover probably some flexing would be assumed as there probably isn't much reinforcing. The question I would ask myself would be: Does it matter if it caves in a little under weight? Probably not. Maybe you would stand on the cover and bend your knees and then straighten out your legs rapidly a few times in succession. Listen for cracking noises. If it doesn't flex that much...3/8" for a number, and doesn't make a crackling noise when you exercise it then I wouldn't worry about it. If it does deflect/crackle, I'd glass in some reinforcing horizontal multiple ply plywood (cabinet grade) strips, 2 or 3 and be done with it.
Click to expand...
It’s definitely not 3/8”. Maybe 3/16” at the most. Sometimes I will hear a pop - but it’s hard to get it to do so. That definitely concerns me.

Would you glass in the reinforcement from underneath? Not sure I have enough access to do so. Ill take a look into that when I replace the rotten coffin box hatch and have material laying around.

Thank you for the advice
 
Texasmark

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,975
halsteadmorris said:
It’s definitely not 3/8”. Maybe 3/16” at the most. Sometimes I will hear a pop - but it’s hard to get it to do so. That definitely concerns me.

Would you glass in the reinforcement from underneath? Not sure I have enough access to do so. Ill take a look into that when I replace the rotten coffin box hatch and have material laying around.

Thank you for the advice
Click to expand...
"Would you glass in the reinforcement from underneath?" That ought to work and if there is room, install "ribs" of some sort to get some height prior to installing the glass mat. Height in the "deflection" equation goes up as the cube of the parameters, making it your most effective dimension.
 
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