cp 23 oil canning ???

[JF AIR]

I posted last year about stress lines both sides of the hull , starting near warerline from a hard spot and spreading and opening crescent like and running aft along the outside of the hull
It has grown further aft both sides this year...
I looked inside the hull but the pattern goes unnoticed although it made me observe the edges of the bulkhead and I noticed it is not following the curvature of the hull by aprox 1/4 inch , is unbedded , untapered
That would be the bulkhead corresponding to the wall running fwd of the portapotti pit
Although , a minimal part of the bulkhead edge contacts the inside hull almost exactly where, from the outside , the cracking is noticed
That led me to inspect other bulkheads and most are sitting free from any contact or bedding with the hull

Has anybody ever encountered such situation???
Is the installation of the bulkhead any different in your 23s
jf air

[edbuchanan]

Hi,

About ten years ago I found one crescent shaped gel-coat crack below the waterline at the main bulkhead.  A surveyor found no water infiltration with his water absorption meter.

He suggested tabbing the hull/bulkhead joint with fiberglass, but thought that might be rather extreme ("do it if you are going to cross an ocean").  The bulkhead is quite accurately cut and is in direct contact with the hull for about 80%(?) of its length.  The worst gap is about 1/16".  The surveyor also suggested that it would be easier to add a bit of a fiber glass bulge to the outside of the hull, but the hull is faired so well it would be a shame to do so.  No action was taken, so far so good.

Ernie (Molly 23/II, 1984)

[Paul]

JF Air:

For what it's worth (I'm a CP-16 owner with very small bulkhead), I am inclined to think that the stress cracks are coming from a hull that is flexing.  Something the hull is not intended to do.  One job of a bulkhead is to add stiffness to the hull.  However, if the bulkhead is in direct, firm contact with the hull, it can cause a hard spot on the hull, which may lead to stress cracks.  I understand that the bulkhead is meant the be tabbed in place.  Sometimes with a little cushion between the bulkhead edge and the hull.  A wide tab sufficiently spreads the load to avoid the hard spot problem.

I haven't seen the bulkhead of a CP-23, so I don't know how it's supposed to be attached.  As for the CP-16, mine was rotten, so I replaced it with a generous fillet and tabbing.

Here's a good online source for classic fiberglass boat repair.  They are a friendly bunch and may be able to help further. 

http://www.plasticclassicforum.com/

Hope this helps,

Paul