Holes in bilge bulkheads...how big?

[Sabre27Admin]

Iain C
United Kingdom
181 Posts

Posted - 13/02/2013 : 11:49:22
My boat is a fin keeler, and has a fairly deep bilge under the hatches on the saloon floor. This bilge is cross braced with fairly substantial members that run athwartships and are about 5" deep. They effectively divide the bilge into about 4 compartments, and the bilge pump intakes are in the aft compartment.

Something that has always bothered me is that the holes connecting these compartments are very small...I can't even get a finger through them. This would obviously be a major issue if there was a serious water ingress forward...the boat would end up with bow down attitude before the water ever reached the pumps, and the aft compartment would be pumping dry far faster than the water forward would flow through the holes back to the pumps.

I think the holes need enlarging. What size do people have on their boats? I guess something slightly bigger than the diameter of the pump inlet would make sense?

Also, what are these bulkheads made of? Are they a solid GRP laminate or is there a wood core? If so, I need to make sure it stays dry...I was thinking of drilling a hole and gluing in a piece of GRP or carbon mast tube with epoxy...any advice?

Thanks
Edited by - Iain C on 16/02/2013 17:44:03
ianfr
United Kingdom
104 Posts

Posted - 15/02/2013 : 13:36:07
Iain

The little bulkheads on Apogee have no holes at all.

I guess that is the design.

Regards

Ian

Kind Regards

Jo and Ian
Apogee, Tollesbury

sabre27
178 Posts

Posted - 16/02/2013 : 15:43:23
On twin keeled Corsair, the ‘floor supports’ have a plywood core and GRP sheath. I also, didn’t like the small size of the drainage apertures so I cut an ‘arch’ into the supports and glassed them over, awkward. A ‘core drill’ would have been easier but wasn’t to hand at the time.

I have two Henderson Mk 5 bilge pumps, The main pump is in the side of the port cockpit locker and is operated by the Helmsman as he steers his course. The other one empties the ‘Head holding tank’ and has a ‘switch-over’ valve, if and when required, to pump the bilge ‘in extremis’. They pick up back-to-back from the same place under the floor with good access to keep the strum boxes clear.

It all works a treat and has actually, once been used in anger! But that’s another story.

I find that I cannot keep the rather shallow bilge dry, as a small amount of water enters from the anchor locker, drips from my Blakes sea-cocks and a small amount from condensation.


Paul Howard. S27OA Technical Officer.

Iain C
United Kingdom
181 Posts

Posted - 16/02/2013 : 17:50:33
Thanks chaps.

What got me thinking was the pictures of the fin keel removal on Stroma. It's always been a concern, and Stroma seems to have bigger holes.

Rapidly coming to the conclusion that the easiest thing will be to bog in some carbon fibre tube I have going spare...job done.

Up until last year I had two bilge pumps...an electric one on a float switch, and a whale gusher, handily mounted under the nav seat! Obviously both far from ideal, so I now have a third mounted within reach of the helm.

keith
United Kingdom
118 Posts

Posted - 24/02/2013 : 21:28:25
On our boat the limber holes are approx 35mm dia, floors are 25mm ply heavily glassed in. To enlarge them you might use a tank cutter in a right angle drill or a coarse rotary rasp.