Bulkhead Stress Crack Repair

[iaff284]

Hey all, we have a new to us 2007 Cobalt 282 with twin 6.2s. The interior is in great shape but the hull has some wear and tear that needs attention. I have done some gelcoat and fiberglass repairs on our other boat but this issue is new to me. On the hull in the same spot on both sides there are stress cracks. Directly behind them are a bulk head that runs across the back of the boat in front if the engine compartment. I am 99% sure that the bulkhead is sitting on the hull causing stress cracks. What is the best way to fix this? My initial plan was to cut back the bulk head 1/2” on each end where its making contact, leaving the tabbed glass behind it and fill the gap I cut out with 5200 and reglass and gelcoat over everthing. This would be from inside the engine compartment. Any thoughts or a better way to do it? TIA!

 

[cyclops222]

Are they truly just stress cracks ? Like doing WOT from a dead stop ? Pictures are really needed. If the cracks are AHEAD of the engine bulkhead area ?
First guess is a structural stress crack from improper sling lifts. If yes ? I vote several layers of glassed in strong cloth on both sides of the bulkhead.

 

[MikeSchinlaub]

The bulkhead SHOULD be attached to the hull. It's part of the structure of the boat, along with the stringers. Cracks can happen for lots of reasons. As cyclops said, need pics.

 

[iaff284]

I’ll post pics tomorrow

 

[iaff284]

 

[iaff284]

These are pics from when we bought the boat. At first I thought they were impact cracks but then a fiberglass guy was looking at our neighbors boat and I asked his opinion and he said it looks like the bulkhead is setting right against the fiberglass on the back side and creating a hot spot on both sides of the hull. When I looked inside there is definitely a bulkhead exactly where the middle of the cracks are. When I researched it on some of the forums the pictures match how the cracks present for that issue. There should be a gap between the end of the bulkhead and the fiberglass hull thats filled with a softer material like balsa or epoxy putty then tabbed in.

 

[MikeSchinlaub]

I've never seen a bulkhead gapped like you describe. The purpose of the putty is so there isn't a gap. When we replace them, putting them same as factory, we get as tight of a fit as possible. The putty is to attach the edges to the hull, and to prevent air voids behind the glass.

 

[Scott Danforth]

post a pic looking down the side of the boat.

sometimes when foam gets saturated with water and freezes, it will push the hull outward, however where the bulkheads are, it doesnt move and you end up with a slight pucker at the location of the bulkhead.

 

[iaff284]

Sorry for the delay in the reply, it will be a few days until I can get back to the boat for the additional pics. Mike, everything I had read recommended the bulkhead is cut to fit with a slight gap everywhere it meets the hull. When it's attached there is a softer material placed such as putty, balsa, or foam against the hull then the bulkhead is set and tabbed in. This supposedly allows the fiberglass to flex some and prevents the bulkhead from creating hard spots against the hull? Scott, where would the foam be in a that could freeze? Maybe in the stringers?