Grand Banks 42 Classic (fiberglass) - Keel Question

[Mac G]

Does a fiberglass Grand Banks 42 have a hollow keel?
Is there a keel drain someplace?
If so, where?

Was investigating the deep center bilge space under the aft cabin sole and found a 1" diameter vertical pipe going straight down into the deepest, most aft section of the keel.

What is that pipe for?

Please advise

Thank you

 

[Cigatoo]

There should be a Garboard drain plug on the (outside) keel. Usually starboard side about 3/4 aft. Not 100% sure if they came from factory or if they have been added after the fact. Maybe just northern boats? Regardless you should have one being in Mystic. Not sure about the pipe.

 

[garbler]

The early run of the glass 42’s were hollow box style keels with no thru hull drain. I surveyed one years ago in Maine where during hammer testing it felt solid but that didn’t figure so I looked closer inside found an area around the forward head where the keel cap looked looked raised or distended. I asked the owner about this and he didn’t know anything so I asked if we could drill a small hole through this cap where it was swollen and explained we could easily patch it. He agreed and water squirted out, very stinky water but not gray or black water. I couldn’t find any damage from ice expansion anywhere but suggested he have the yard install a drain plug in the Spring. Since then it seems most of these hulls I’ve looked at had drain plugs fitted not sure if American Marine started doing this or they paid commissioning crews over here to do so. I could never find out where the water came from and didn’t taste it but the yard said the boat was slightly down in the bow when blocked and it drained out in about twenty minutes so it wasn’t full.

The cap is a way to keep water out of the bilge and interior plus provide a flat smooth surface inside. Sort of a secondary flooding skin. Problem is if you do ground and penetrate the box keel and take on some water you can’t tell. I’m guessing the pipe you found is a way to sound this void and/or pump out. It’s possible that American Marine now fills the keel with foam but just a guess.

Rick

 

[Comodave]

Hollow keels can cause a stink even inside the boat through the fiberglass. We had a Trojan that had a smell in the cabin. Not the head because I had the complete head system out of the boat in preparation for a new head. I finally came to the conclusion that it was the hollow keel. I very carefully drilled a small hole and the stinkiest water imaginable came squirting out. I enlarged the hole and used a shop vac to suck all the water out. Still stunk. Went aft and drilled another big hole and flushed soapy water in the aft hole and sucked it out the forward hole. Still stunk. I finally ground off all the thin cap of fiberglass and scrubbed the keel out with a lot of soapy water and the stink was gone. The cap was only cosmetic because you could push on it and it would flex very easily. Then I could flush clean water into the keel and pump it out to keep it clean. I installed a Whale pump with the remote pickup to scavenge the water out of the keel.

 

[garbler]

Yes it’s true old standing water in a fiberglass void really stinks I’ve run into it many times before. Usually the keel envelope or box is the bottom of the mold and never gets finished off so lots of strands and porosity. Did you ever figure out where the water was coming from Dave ? When I inspected the GB in Maine it was frozen except water on top where we drilled. Therefore I couldn’t find any leakage outside and never re-attended the boat again so the source was never discovered. Lots of possibilities of course, both exterior and interior, but I never resolved it. I usually have a small saltwater freshwater aquarium test kit I use but didn’t have it with me.

Rick

 

[Comodave]

I think it just leaked through the fiberglass cap. The glass wasn’t finished too well and probably over the years it leaked in little by little until the keel was filled up. It stunk worse than a holding tank.

 

[garbler]

You’re probably right about that but I could never prove it nor was I too keen to get real personal with my inspections

Rick

 

[Nick F]

Following with interest. I recently purchased a 1974 fibreglass GB42.

 

[Mac G]

Do you also have that vertical pipe in your bilge?
It is under the hatch in the sole in the center of the aft cabin.

 

[Nick F]

Do you also have that vertical pipe in your bilge?
It is under the hatch in the sole in the center of the aft cabin.

I will look

 

[garbler]

Nick I wouldn’t worry too much about this but if your boat doesn’t have a bilge drain plug I’d install one. As I mentioned before if the keel void does fill with water and during your next haul out you see water weeping or leaking from the keel then you’ll know it’s been punctured or fractured and you can repair it. The pipe that MacG mentioned sounds like a good idea since it allows you to take a stick and sound it to determine if water has filled the void. If you find water it would be smart to test it and know if it’s saltwater or fresh of course if you’re on the lakes it’s hard to tell if the source is from inside or outside. But a sounding tube will let you monitor the rate of flow so if you have keel damage it’s probably fairly fast. I’d certainly have a cap on the pipe. If you elect to install such a sounding tube or pipe it should be located aft in the deepest bilge sections.

Dave mentioned how stinky the water was in his boat and this is pretty typical of old standing water in a void. I would consider cutting and installing several inspection and clean out hatches in the keel cap. As I recall the GB 42 I drilled in my previous post this cap was about 1/4” maybe less thick which is plenty of material to cut, and screw fasten a glass panel hatch or similar making sure you properly bed it properly. This gives you the ability to use a pressure washer or something to hose out and clean this void from time to time letting the water drain out of your bilge drain fitting. The only problem I can think of are any floors or transverse stiffeners in the void but I doubt they are tabbed all the way to the foot of the keel so drainage should be okay. And of course you will need to cut your hatches between floors. Something to think about

Addendum: thinking about this further I seriously doubt that the interior keel cap is 100% watertight so it’s probable that a punctured keel would flood above the cap. Therefore the sounding tube should be sized and constructed so that a pump intake hose or fitting could be used in an emergency.

Rick

 

[Nick F]

Thanks Rick - this is not top of my list at the moment, but it is something I would like to do. I will be looking for further intel on the keel construction from other GB42 owners first.
I envisage at least a couple of sealable holes into the keel box, so that I can flush and dewater and then monitor. Not sure if I want an external plug for draining during liftout.

Regards,
Nick

 

[GB42-424]

Tube under aft cabin sole

I have that tube in my 1974. DO not have any external drains. Been wanting to unscrew the cap to see where it leads for some time. One of many things on my to-do list. I'm staying in the water this winter, so don't anticipate checking any time soon.