Refitting cast Iron keel

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Mike Brown
Posts: 29
Joined: Sat August 5th, 2006, 11:35 am
Location: Auckland, New Zealand

Refitting cast Iron keel

Postby Mike Brown » Sat December 18th, 2010, 7:17 am

Hello Team

I am just about at the stage to refit the cast iron keel to my 24ft Eventide. When I removed it, it appeared that it had originally been fitted using damp proof course and putty as the sealant. Would this be correct as if so I will do the same. Any advice would be greatly appreciated.

Kind regards
Mike Brown
New Zealand

Billaboard
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Joined: Thu October 5th, 2006, 9:48 pm

Re: Refitting cast Iron keel

Postby Billaboard » Wed December 22nd, 2010, 8:26 pm

When we built the Wild Duck, this was something I worried about and got few answers to. All I can say is what we did.

We cut canvas to match the iron and wood mating faces and doped it liberally with red lead paint. Then we painted the surfaces with red lead and put Sylglas (which I used to use to waterproof aerials) where there looked like being imperfections or where it looked as if a bit more squidgy mess would help. I notice now there are many varieties of Sylglas, but I presume this was "original". It came on a roll, was a green/khaki colour and looked like fibreglass in some sort of mastic.
We put the whole lot together as much as we could while the paint was still wet.

I still worry about this and the state of the keel bolts, but the original surveyor 25 years ago and the one last year seemed happy.

Mike Brown
Posts: 29
Joined: Sat August 5th, 2006, 11:35 am
Location: Auckland, New Zealand

Re: Refitting cast Iron keel

Postby Mike Brown » Thu December 23rd, 2010, 6:31 am

Many thanks for your reply. Yes I am a bit stuck here is we don't have a lot of products for this type of application apart from the DPC and putty and red lead paint. I have 6 keel bolts to fit with the keel so have to work with a product that is going to give me ample time. I haven't seen any other MG yachts in New Zealand so not able to seek much advise. I think I may have to try the DPC and putty and then bolt up tight. I guess after all I am only trying to prevent water entering and all the carvel planks on the hull bottom and sides are chaulked with putty and this keeps the water at bay so same concept.

Kind regards
Mike

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Kevan
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Joined: Sat June 26th, 2010, 9:10 am

Re: Refitting cast Iron keel

Postby Kevan » Sat December 25th, 2010, 11:58 pm

Hi there. This forum is to "ask the experts" so I wasn't intending to put my two cents worth in(!) but there isn't much feedback and I have been doing some reading of late in prep for my own build and had some ideas/comments. I am further emboldened by Billaboard's and your initial work mirroring my intended approach.

I concur with Billaboard about bedding the keel. Michael Verney recommends something as simple as that - canvas and lead paint - in his book(s) however Robert Steward (silent on "bedding" the interface) notes that the keel washers are the most likely point for water ingress and recommends "caulking" the bolt with a wrap of cotton.

Looking pragmatically, the metal ballast keel is founded on a wood keel and will have to transfer lateral forces to each other the hull. Waterproofing this connection isn't the aim so as I see it the key would be to have a secure interface that isn't going to deteriorate with these forces, hence loosning the keel bolts and inviting water in. Well mated surfaces (unlikely with a metal cast ballast keel pressed against a wood keel) would be ideal. I will be aiming to use a thin (where well mated) or strong and non-deteriorating (where not so well mated) bedding material with the keel bolts tight.
Cheers and best of the season!

Mike Brown
Posts: 29
Joined: Sat August 5th, 2006, 11:35 am
Location: Auckland, New Zealand

Re: Refitting cast Iron keel

Postby Mike Brown » Mon December 27th, 2010, 6:03 pm


Thanks also Kevan for your comments which are most appreciated. It certainly has given me something to think about. I have also been speaking to a traditonal boat builder who says he has used epoxy before as well an states that it will part quite easily if you need it to. I think I will put the keel fixin on hold for the time being and dwell a little more on the options.

Kind regards
Mike

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Fiddler's Green
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Re: Refitting cast Iron keel

Postby Fiddler's Green » Sat January 15th, 2011, 1:14 pm

Hello there I thought I would add a note here re the keel.

There is a lot on the site proper about this too.

The Eventide 24 ballast keel should now weigh a minimum of 1020lb. If the keel is still off and it weighs less, (measure it, cast iron it could be 5" deep and 560lb, 8" deep and 780lb or 10" deep and 1020lb.)

If it weighs less, add some weight, for an iron keel steel 25mm thick, flame cut plates to make up the difference, the boat will thankyou and so will the crew. OK you may need longer bolts, but believe me it is the best thing you can do for the boat at this stage. i have done it twice a 24 and a 26.... (you can bolt on extra galvanised to the bilge plates for now, make them longer and neater another day! They should be just 1.5" less deep than the ballast keel.

To refix.....

Today, although you can still go the traditional route with red or white lead putty, if the Health and safety boys will let you... It is far better to use a modern sealant. Sikaflex 291 will do the job 100%.

A good 5mm layer of this in place and gently lower the boat onto keel, do not over tighten bolts at first. wait a few hours for it to cure, it needs moisture in the air to do so.... The weight of the boat on keep will squeeze a lot of the mastic out... there is a case for a layer of glass fibre to absprb it, but most use the Sikaflex on it's own.

Do ensure the keel bolts are mild steel, galvanized preferably, for Iron or steel keels, (Bronze or Monel for Lead) . Not many of us can afford lead/monel, but years ago it was easier to cast a lead keel miles from civilisation. If you have lead it can be supplimented with more lead, sealed with sikaflex.

Never use stainless of any grade to secure anything beneath the waterline.

Hope this is not too late to be of assistance.

Regards,
John
Proud owner and builder of 'Fiddler's Green'

Mike Brown
Posts: 29
Joined: Sat August 5th, 2006, 11:35 am
Location: Auckland, New Zealand

Re: Refitting cast Iron keel

Postby Mike Brown » Mon January 17th, 2011, 5:50 am

Hi John

Many thanks for your reply and it is not too late as I am still pondering over this issue. My cast keel is 5'' deep so I was going to plan on fixing 25mm thick plate steel to the bottom for extra ballest. I did want to use the traditional fixing method of mastic damp proof course (DPC) and putty. I know this sounds a little old fashioned but that is how it was initially bedded and also this method will allow me a lot of time to fit it. I have talked to a traditional boat builder here and he says that he sometimes still uses this method. He said that on each surface to apply a layer of putty, then a layer of DPC, then another layer of putty so infact the DPC has a layer of putty on both sides. This would have to be done between the bottom of hull to keel block which is 75mm thick, between keel block and casting and again between the casting and the extra 25mm steel plate that I will fix to bottom of keel. Can you see anything negative with this method or any problems that I could encounter. The bolt holes I was also going to pack with putty.

Kind regards
Mike

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Fiddler's Green
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Re: Refitting cast Iron keel

Postby Fiddler's Green » Mon January 17th, 2011, 10:25 am

Hi Mike,

I would sandwich the extra 1" thick steel plate between the cast iron and the deadwood.

You can gently lower the plate (s) onto the ballast keel, locating the holes with dowels. Use Sikaflex between layers.

I would aim to make the keel over 1,020lb, just. the boat will sail so much better for it. This is the modern plan keel weight for a 24. Extending the bilge keels too is a good idea, or she will heel over a long way when dried out! You can always bolt on a gavanised extension for now, or use 'Zinga' or another Zink rich paint.

If the bilge keels have a flat bar bottom, grind off one side (at least), so you can bolt the new extension to the inside face. Make the shoe on the bottom 1.5 to 2" shallower than the main keel. If the bilge keels are corroded this might be the time to make new ones.. another tip is to make the aft edge vertical, to add more area aft, to off set Weatherhelm....

You will have to fair the front of the keel into the old dead wood with a block or two of wood and some epoxy putty, easy to sand it down smooth. also the sides of the new extra ballast...

I would use modern materials today, they are easy to use and do work.

Hope all this helps,
Regards,
John
Proud owner and builder of 'Fiddler's Green'

Mike Brown
Posts: 29
Joined: Sat August 5th, 2006, 11:35 am
Location: Auckland, New Zealand

Re: Refitting cast Iron keel

Postby Mike Brown » Tue January 18th, 2011, 7:58 am

Thanks John it is all starting to make sense now and I can picture the process. Just one more question if I may, between the 2 contact surfaces should I use a layer of mastic (DPC) and sikaflex or just use the sikaflex to bond and seal.

Many thanks
Mike

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Fiddler's Green
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Re: Refitting cast Iron keel

Postby Fiddler's Green » Tue January 18th, 2011, 9:50 am

Today I would just stick to the Sikaflex, if you exscuse the pun!

Wife helped me fit bilge keels (over 20 years ago), she still talks about how long it took to get the stuff of her hands!

Regards,
John
Proud owner and builder of 'Fiddler's Green'


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