is fiberglass hull flex a problem?

[james scott]

I have a 1986 ScanMar 33 in good condition. Recently, pounding across the alenuihaha channel in heavy wind and seas, as I rested in the forward cabin trying to get some sleep, I noticed quite a bit of flex in the fiberglass hull each time that we crashed down the back of a wave. As far as I can tell, there are no structural problems and the hull seems to be in good shape but the glass certainly does seem to be a little thin up there. I am wondering if this flex can be a problem. Could it crack or break? How much pressure would it take to damage the glass and create a leak?

 

[alldodge]

Re: is fiberglass hull flex a problem?

I have a 1986 ScanMar 33 in good condition. Recently, pounding across the alenuihaha channel in heavy wind and seas, as I rested in the forward cabin trying to get some sleep, I noticed quite a bit of flex in the fiberglass hull each time that we crashed down the back of a wave. As far as I can tell, there are no structural problems and the hull seems to be in good shape but the glass certainly does seem to be a little thin up there. I am wondering if this flex can be a problem. Could it crack or break? How much pressure would it take to damage the glass and create a leak?

:welcome: to iboats

Howdy and Aloha

Most boats do flex, it's kind of it either bends or breaks. Looks like it is typical for Scanmar. Here is a link and starting on page 39 is a good article

https://cld.pt/dl/download/c3e13e84...ia Nautica/Revistas/Sailing.Today.2013-04.pdf

 

[tpenfield]

Re: is fiberglass hull flex a problem?

Sailboats do not have as rigid a structure as do power boats. So, you will get some flex. If it is a problem, you will probably notice cracks or heavy crazing in the gelcoat on the outside of the hull.

I'm not sure that you would get a simple leak upon failure . . . something more catastrophic.

 

[james scott]

Re: is fiberglass hull flex a problem?

Sailboats do not have as rigid a structure as do power boats. So, you will get some flex. If it is a problem, you will probably notice cracks or heavy crazing in the gelcoat on the outside of the hull.

I'm not sure that you would get a simple leak upon failure . . . something more catastrophic.

Thanks for the replies, I will look closer for crazing or other signs of problems. If I decide I want it to be stiffer can I simply lay some fiberglass and maybe a stringer running horizontally between the bulkheads on the inside of the hull to stiffen that area up?

 

[jbcurt00]

Re: is fiberglass hull flex a problem?

Stiffening up 1 area may telegraph the flex onto another adjacent area that is then overstressed. If it's supposed to flex, let it, IMHO.................

 

[Tail_Gunner]

Re: is fiberglass hull flex a problem?

Fiberglass flexing would be a very bad thing...it ends in glass. You might PM Ondarvr who is qualified to answer such a question

 

[Bondo]

Re: is fiberglass hull flex a problem?

Thanks for the replies, I will look closer for crazing or other signs of problems. If I decide I want it to be stiffer can I simply lay some fiberglass and maybe a stringer running horizontally between the bulkheads on the inside of the hull to stiffen that area up?

Ayuh,.... Welcome Aboard,..... Unless ya find a serious flaw in the lay-up,....

Like jbcurt00, I think tryin' to fix a non-issue will create real problems,...

Lotsa things are Supposed to flex, within their design parameters,...

 

[greenbush future]

Re: is fiberglass hull flex a problem?

My first boat was a 1978 Larson (I think) 23 footer ( very heavy boat) with a Ford V-8, and when on plan in heavy sea's the sides of the boat would actually flex in and out, enough to physically see it. It scared the crap out of me, and I chalked it up to just being an old boat that had lots of use. When I sold the boat the price reflected the fact that it was a 1969 model and was a parts boat for the most part. While it did function well getting on plane and all that, I personally didn't feel comfortable using the boat.