Page 1 of 1

GH31 - plans for bilge plates ?

Posted: Fri March 16th, 2018, 10:56 am
by SWpacific
I'm the proud new owner of GH 202 in Auckland NZ. She's in a very run down state having been left on a mooring for about 10years, but about to get a major refit and continue her cruising life.

A past owner has unfortunately removed the bilge plates, so I'm planning to build some and fit them. Apparently she has done some extensive pacific cruising without them, but I would prefer to have the ballast back on the boat.

Is anyone able to help me with some plans?
What's the plate thickness?
How is the keel bedded onto the hull?

Any assistance would be really appreciated. Thanks !

Re: GH31 - plans for bilge plates ?

Posted: Mon March 26th, 2018, 5:59 am
by SWpacific
If anyone also has information or a photo showing the jig used to hold the bilge plates when fitting that would be great.
I'm assuming that the plate thickness might be 25mm ?

I found a photo of the brand new? GH202 - with keels still attached, presumably just having been lifted off the ship in Florida.
They appear to have been removed in the Pacific Islands, and she apparently arrived in NZ without them.

When I discovered GH202 on her mooring, there was a fern garden starting up in the cockpit !
And also a mussel farm below. Fortunately the rot is confined to the cockpit area.

Re: GH31 - plans for bilge plates ?

Posted: Mon April 9th, 2018, 11:05 am
by GHM

I built the Hinds for nearly 10 years, after completing two for myself. Re the bilge keels, I had a drawing and the original plywood template, both of which are sadly no more. However, there is a lot I can offer to help with the design and fitting techniques. They were 1/2" or 12mm mild steel, galvanized, although, with modern epoxy finishes I would now go for that rather than galvanizing. I found years ago that many galvanizers were closing down because of the increasingly severe environmental requirements, and also you need to find one with a bath large enough to take them. There may well also be a logistics (Cost!) problem if you have to transport them miles between fabricators and galvanizers.

Fitting can be very difficult. They are heavy and difficult to manoeuvre delicately and you need to be precise and quick when you have a sealant going off. Eventually, I developed a simple system using a timber jig to hold one at the correct angle, mounted on a pallet truck which Could be inched up and hold the keel securely in place while the bolts are fitted. I even fitted one pair single handed although it helps if someone can hold the bolt heads outside of the boat while someone on the inside tightens them up! You can get round that too, with a little imagination, but you need to be fit because you will be running up ladders, jumping down into the boat and then out again, as fast as you can go.

They were fitted with a wooden pad between the keel flange and the hull to take up any gap and to prevent crushing the gelcoat. Sealing was always done with Sikaflex (you are risking a lot if you use anything else - silicone never!!). A lot of caulking cotton was used in various places to retain the sealant and prevent it all squeezing out. There were steel pads (washers) inside the boat for each pair of bolts, bedded on sikaflex/caulking cotton, etc, etc. Don't try to "improve" things by fitting bolts of dissimilar metals. The keel will probably eventually fall off

As you can see, there is a lot involved, and there is too much to write here but, if you really are going to get round to it, I am happy to help with sketches, tips etc. If that happens it would be easier if we had each others emails and John will pass a message on to me. Good luck.

Mark Urry

Re: GH31 - plans for bilge plates ?

Posted: Sat April 14th, 2018, 9:57 pm
by SWpacific
Hi Mark,
Thanks very much for that useful information.
Yes, I see it will involve a few logistics. As I'll be using the boat a lot in a tidal estuary it will be really good to have the bilge keels back, so I'm sure it will be worth the effort.

I was planning to make a wooden template first (laminate 2 or 3 strips of 4mm plywood) to get the exact hull curvature, then make up a pattern for each keel in some cheap 12mm plywood based on the side-profile drawings shown on this website. I think I can get the correct angles from the front profile drawing. I assume these drawings are pretty accurate, with the correct difference (2") in height shown between the deeper main keel and the bilge keels?

So after making up a pattern, the current plan is to buy two sheets of 12mm steel plate (thanks for the thickness), and have them cut to the exact shape - as I can't do this myself. They charge about NZ$40/metre for cutting.

Then I should be able to transport the keels (maybe one by one) in my car trailer to the welder for the next stage.

Is the flange at the top of the keel 12mm steel flat ?
I'm assuming the keel bolt holes need to be marked, then drilled. Then the flat bent to shape (using the laminated ply template).
Then the pre-drilled flat needs to be welded onto the top of the keel plate.

Then a foot for each keel with an L shape profile - also out of 12mm flat.

What wood type did you originally use between the hull and the keel flange ? Or can I use the laminated ply template - covered in west system ?

Yes, pallet loader sounds like a good idea. I was also thinking about knocking up a frame in 20mm plywood to hold the plate at the correct angle, then jacking it up into position with four car jacks.
Even getting the heavy keel into the frame will be a bit of a struggle I imagine.

Yes, Sikaflex and caulking cotton sounds like a good idea.

What diameter bolts ? I assume everything in steel (non-galvanised bolts) to avoid galvanic action.
Then paint everything in a 2-pot steel coating system, like Interprotect, and attach a couple of anodes.

Can you please let me know if you think there are any flaws in the plan !
Thanks very much,

Re: GH31 - plans for bilge plates ?

Posted: Sun April 15th, 2018, 9:48 am
by Eventide Owners Group
Hello Matt

I will pass this on to Mark, but I can add my three pennies worth too.

The bilge keels are best galvanised, then they can be later epoxy coated. Sure someone is galvanising in N.Z. Not expensive but the best protection…. Mine have survived 28 years this way and when I stripped the epoxy off two years back, the galvanising was like new! Re epoxied…. 3 coats… Fit an anode to each plate to protect them….

Use Galvanised 12mm coach bolts to secure, so the holes in the top 12mm flange have to be squared. (We did ours with a long square tapered punch). That way they seat well and offer only a domed head for less resistance and nooks and crannies for barnacles to cling on!

The timber piece between the bilge plate and the hull should be good quality hardwood, iroko or similar best. Can also be epoxy coated and glued and screwed to hull. Use Sikaflex to seal the plates to the hull packing piece. The top steel plate is flat steel but you can slightly profile the edges.

The bottom plate or shoe just squared 2 inch wide x 12mm flat steel welded on.

Yes the bilge keel must be approx. 1.5 to 2 inches shallower than the main keel. So hopefully you ground on the main keel first….

Where did you get the bilge keel drawing from? Is it on the Forum?? Have not yet looked….

Good luck bringing her back to spec.


Re: GH31 - plans for bilge plates ?

Posted: Sun April 15th, 2018, 10:04 am
by Eventide Owners Group
We have a member here Nick, who has a GH 31 that lost one bilge keel. (It is still at the bottom of a nearby creek!)

I have suggested he measure the remaining one up then take a photo and put the measurements on it for you and anyone else wanting to replace a keel, or two!

Hopefully Nick will get back to me should not be a very difficult task to measure the one he has left.... He is going to have to do it anyway, to have a new one made!

Whilst I under stand Marks comments about the difficulty of finding a galvanisers, if you are intending to keep this boat for more than 5 years and do not want the job of shot blasting and re epoxing every now and again, it has to be worth finding a company that can galvanise tham. In the UK galvanisers still have huge galvanising tanks, large enough for the steel, commercial waste bins. Popular still as these are far more durable than the plastic or polythene bins seen about.

Suggest at least two strong people outside the boat with a purpose made frame and trolley jack to carry and move the plate and two inside with the nuts, loads of Sikaflex, loads of rubber gloves and do not tighten fully until it has set for several hours or you squeeze it all out! the excess can be removed, sugest one preson doing just that or everyone gets covered in the stuff, and it does not come off easy!!