Fractures in stringers in a Swan 40: Question for Lars
Hi Lars et al.,

A puzzle for you!?

We were looking at a Swan 40 yesterday that has some structural problems. The bulkhead at the front of the saloon is separated and has been re-glassed and it has minor cracks in the stringer at the chart table in the corners next to the settees, as well as some cracks in the non structural fiberglass structures around the battery box. There is about 2-3 mm of movement side to side seen between the bulkhead and stringer at the head when tacking so the hull is flexing. Note it is one of the more "modern" hulls with fiberglass stringers not like mine and Opelia with the wood glass construction.

The rig is identical to mine and Ophelia. i.e. an interior strut has been installed to support the elbow where the shrouds are attached. So we suspect that the problem is not due to the rig.

Cracking all the way back to the engine makes us think this is not due to the rig but the only other large force in the boat. So by process of elimination we rule out the rig out as the cause and suspect the keel. Also, the hull was fine up until a few years ago making us think that some modifications done recently had contributed to the problem.

So for the suspect. One of the half stringers on each side (not the right name) under the settees in the saloon has been compromised/removed in order to remove the two SS water tanks and put in one large water tank on each side.

Now to the question. Is this the source of the flex of the hull. By removing this structural component is the keel now able to move slightly when heeled over causing the hull to flex and resulting in the stress fracturing and movement at the head bulkhead??

We, Kaj from Opelia, Richard from Moksha and Mike from Storm Storm Svale are trying to figure out the problem. The yards that have been involved are focused on the rig and patching cracks and have been patching the head bulkhead problem which has not been successful. WE need to figure out and fix the cause and not repair the symptoms!!

Wish you could see it but from a distance what do you think?? Are we on the right track?

Thanks in Advance!!!!

Mike et al.,

Dear Mike,

would it be possible to know hull # (at least in a private message) and see some pics?

Fair winds!

Matteo (38/067 Only You)

Mike

I am willing to contribute towards solving the problems, but pictures and exact location of the damaged areas are required.

You may decide whether to present this on the Forum or not, unless Matteo has a differing opinion.

Best regards

Lars

Perhaps you gents are carrying this conversation off list -but it has occurred to me from reading this post the first time that if the longitudinal load carrying structures were in fact 'broken' at any point, perhaps worst at midships, then it would be expected to see excessive twist and flex in the hull (now no longer properly stiffened), which in turn would cause the transverse stiffeners to displace excessively and give the results you describe. A rectangular box can carry a lot of torque (in this case, the box is the frame structure of stringers and transverse members acting to resist hull twist/flex) but if you break the box, it's over. I would be inclined to try and restore the compromised longitudinal stringers, then effect repairs at all the effected transverse members - reglassing them to the hull and bulkheads as appropriate - as long as the hull laminate hasn't cracked too much anywhere, this should bring her back if well done - but a job for experts, and probably not cheap.

Yes, this discussion has been going on in the background. Lots of head scratching but I think we will soon due to the Professor have sorted out the cause. Once we know one of us will be back to you with the answer so that we can avoid this problem in our ladies.
Mike