Boat design / strength question

[Augoose]

I'm planning on replacing my deck in my 1989 20' Caravelle bowrider this winter as there are a few soft spots. From what I can see from inspecting at least the ski locker area, the stringers seem sound. However, until I pull the deck up its hard to know the condition of all the others.

Here is my question - it might be tough to answer.....
How dependent upon the structural integrity of the deck is the remainder of the hull?

On another forum I was told that there is a high potential for failure in the integrity of the hull by operating a boat with soft spots in the deck. In other words, the person was suggesting that the hull would/could crack in half.

I can see where a solid deck would provide lateral strength across the boat and would keep the hull from flexing in, but I would expect that the strength of the hull would be more dependent upon the stringers rather than on the deck correct?

If I were to have rotten stringers and soft spots in the deck could I be at risk for cracking the hull? Stringers aside, does a fiberglass hull itself weaken over the course of a couple decades?

I've run the boat hard for two summers now and not taken on a drop of water nor have I noticed any cracks or integrity issues in or around the hull, but now I'm paranoid that if I hit a wave a little too hard she'll break in half and we'll all be swimming for it while our possessions sink to davy jones' locker.

Hopefully someone can relieve me a bit and let me know that the hull of a boat is stronger than that.

 

[oops!]

Re: Boat design / strength question

If I have rotten stringers and soft spots in the deck could I be at risk for cracking the hull? Stringers aside, does a fiberglass hull itself weaken over the course of a couple decades?

the deck is the sole of the boat.
it provides structural integrity to the entire hull.
the integrety is not dependent on the deck, but rather, the whole boat, stringers, foam and transom. this is held togeather by the deck.

chances of ripping in half?.....not likely unless the whole thing (strings, deck. transom foam) absolute mush.

should you worry?....not really. doews it need repair to be properly seaworthy.....yes !

in the restoration section of the forum, there are a thousand threads that can guide you.
lots for boats being brought back from farmers feilds and the whole shabang is toast.

in the link in my siginature, is everything you need to know in the first 15 pages.

cheers
oops

 

[oops!]

Re: Boat design / strength question

oh,,, btw....the glass itself will not weaken over time....unless there is impact or water intrusion.,.....and then only in that area.

fiberglass hulls have an indefinate lifetime

 

[Augoose]

Re: Boat design / strength question

That's good to hear. I'm pretty confident that I don't have mush, but there are some soft spots that certainly warrant attention and I have every intention of restoring her back to what she was -or better!

The other forum just introduced a bit of doubt regarding the integrity of the hull so every wave now I'm overly cautious - not that I go hammering about anyway....just want the peace of mind.

Thanks for the links and I've been lurking around the restoration threads for about a year now - I think I've got a pretty good idea how to tackle it, just a matter of time and the proper materials.

 

[Augoose]

Re: Boat design / strength question

Wow, I just looked at your thread- TREMENDOUS amount of work!

 

[oops!]

Re: Boat design / strength question

lol....yeah....but what a boat !...i love it

the process gave me a whole new trade ! (as in boat reapir person)

 

[Chris1956]

Re: Boat design / strength question

Stringers run bow to stern. The structural strength side to side is provided by the frames(AKA bulkheads). Remember the deck only provides side to side strength at a single point on the hull(maybe 3/4" thick), fairly high up from the keel. The frames support the hull all the way to the keel, and are joined to the deck.

 

[pmillar]

Re: Boat design / strength question

From reading plenty of threads here on iboats I'm pretty comfortable stating that if you have soft spots on the deck there's a better than even chance your stringers have some rot issues as well. (note, I own a tinny so no first hand experience - just lots of reading)