Bulkheads

[Sabre27Admin]

Iain C
United Kingdom
181 Posts

Posted - 13/11/2011 : 10:02:03
I am currently beefing up the port and stbd cap shroud chain plate attachment as per the handbook. One issue was that the main bulkhead at the aft end of the heads and hanging locker was very poorly bonded to the hull with very dry CSM that I could remove with hand tools only.

So I spent yesterday bonding the bulkhead back in with a mix of epoxy and colloidal silica, a generously radiused fillet and glass tape. I then picked up a book in the sailing club bar and read with horror that the gap between the bulkhead and the bull is supposed to be just that...a gap to prevent hard spots on the hull.

Oops...I'd spent a day filling it all in! However a bit of digging on the Internet did hint that on older cruising boats you are ok to fill this gap in...and if the gap is filled with epoxy/colloidal rather than foam it should be fine. To be honest, the thought of this bulkhead, with the rig loads, NOT bonded as securely as possible to the hull seems a bit scary.

I think the key here is the fact that I have filled an existing gap ins complete finished boat, rather than having installed a new bulkhead tight against the hull in a boat yet to get her deck glued on. I also think it seems to be more critical in larger, more lightly built, more modern craft.

Can anyone confirm before I finish glassing it it? The thought of taking a grinder to all my good work hurts a bit but I'd rather do it now than later!

Thanks
sabre27
178 Posts

Posted - 13/11/2011 : 18:13:39
Hi Iain,
You have it well sussed out and have no need to back track. Just keep an eye on the glassing around stress points as part of your routine inspection regime.

There is no need to stress the rigging to modern yacht racing specs, any possible tiny gain would be outweighed by the increase in the likelyhood of bonding damage.

Paul Howard. S27OA Technical Officer.

Iain C
United Kingdom
181 Posts

Posted - 14/11/2011 : 17:15:30
Paul

Thanks for the advice and for your time on the phone. All of the professional types at my club agreed...bond it all inp properly!

Some of the bits on my boat are a bit scary when you get digging! The port capshroud is joined to the chainplate, which is a stupid cranked design. This chainplate is then bolted to the bulkhead, with fairly small fully threaded bolts, and a reinforcement pad was, erm, placed onto the end of the bolts before the teeny weeny washers and nuts were put on and done up hand tight! All this lot is of course attached to the bulkhead which was no longer attached properly to the hull. Great. Oh, and the chainplate seal peeling off the deck meant that water was perfectly channeled down the 45 degree crank of the chainplate and making it's way into the bolt holes in the bulkhead which was slightly damp in the actual holes themselves.

So, the chainplate is now removed and will have a large s/s fillet welded to it to stop it deforming under load. The bulkhead is now properly bonded to the hull and underside of the deck with large epoxy fillets, two staggered layers of 50mm glass tape and one layer of 75mm bi-axial glass tape. I will be epoxying/glassing in a solid oak backing pad to the bulkhead inside the hanging locker, and I will then bolt the chainplate in place properly with decent coachbolts/washers sitting in oversized epoxy filled holes that have been drilled out to the right diameter.

The stbd size was not much better and most of the cave locker is now ripped out pending installation of the steel reinforcement bracket as per the handbook.

I know the Sabre is a solid boat however with my dodgy rudder and dodgy shroud plates I will be much happier in a blow with these modifications!

yerffoeg
United Kingdom
48 Posts

Posted - 16/11/2011 : 18:18:28
Iain,

Although the Sabre is a great boat, one design weakness in my view, is the attachment of chain plates in the Mark 2s. In my boat there was serious ingress of water through starboard chainplate deck fitting. This tracked through the small bulkhead, to which the chainplate is attached, and then through to the heads aft bulkhead and had and seriously weakened it. This was not picked up in the original survey. Part of the problem, was that the chain plate was bonded in and invisible (out of sight and therefore out of mind).

It took me a good few months, and industrial quantities of thickened epoxy, to fix the problem. I kept things pretty much the same, but rebuilt and slightly repositioned the smaller bulkhead with thicker ply and then covered the whole area with (excessive!)layers of matting and epoxy. The chainplate is now bolted to this, with much more substantial bolts, but is not bonded in as before, so that it is accessible and amenable to inspection. I have been sailing the boat hard over the last 5 years and no problems so far.

Geoff