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Old 19-12-2010, 12:45   #1
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Cut a Hole in Ferro Cement

I am considering buying a Hartley Tahitian. Looks like a good deal but it has a chemical toilet. As I would really need a marine toilet and holding tank I would need to cut one or two holes below the waterline. How does one do that? I could probably get through the cement by drilling a ring of small holes with a masonry drill(s) but how would I cut the armature if necessary?
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Old 19-12-2010, 12:58   #2
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Go to a tile supply store and get a diamond abrasive hole bit similar to the type they make for wood and plastic and lubricate with water as you use it. They are made for cutting clean holes in ceramic tiles, marble, and granite for faucets. Use it in a slow speed heavy drill like a hole hawg. It should easily cut through the wire mesh up to 1/4 inch thick.
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Old 19-12-2010, 13:02   #3
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Just use a diamond hole that is loose fit to the skin fitting, when you fit the shin fitting mix a stiff epoxy fill mix and place the fitting in the centre so it does not touch the metal armature I put an oring around the the base of the fitting to achieve this.
Greg
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Old 19-12-2010, 13:05   #4
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I do this dry as you do want to get keep armature dry.
Greg
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Old 28-06-2011, 14:51   #5
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Re: Cut a Hole in Ferro Cement

Hi All,
I just purchased a 1974 20' ferrocement Ryan Marine Flicka, a gaff rig cutter.
I am flying to Baltimore tomorrow to pick her up with the intention of sailing her down the Chesapeake to the ICW at Norfolk with my final destination Port Aransas Texas via the ICW. A 3+month adventure! She has a 9.? Yanmar inboard.
I need to install a holding tank to the Grocco head, so a vent through hull fitting is needed requiring that a hole must be drilled in the hull along with a pump out fitting on the deck. Also I purchased a Garmen 441s and need to install a transom mounted transducer. I had her hauled Monday so she is on the hard now to have the hull pressure washed for my inspection and to make these installations if they are practicle.
1. Any current advice for the instillations?
2. Are any of you familiar with Ryan Marine and the Ryan Marine Flicka?
3. Any and all positive advise will be appreciated.
The boats new name is Wren as she had no name when I bought her!?!
Thanks,
Kevin
The proud owner of the RM Flicka, "Wren"
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Old 28-06-2011, 17:05   #6
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Re: Cut a Hole in Ferro Cement

Quote:
1. Any current advice for the installation?
Cutting a hole in ferro cement is not to be done lightly (I suggest considering a water cooled diamond saw), nor is the installation of a holding tank.
As you have just brought the boat why not remove the existing toilet, cap off the through hulls and use a porta potty? I doubt if any holding tank of useful size could be fitted.
Searching for information on the Flicka I found this article on installing an air head toilet, but this would be a major undertaking that you may care to consider after you have owned the boat for a while.
The Flicka's draft is listed as 3'3". If this is the case with your boat it may not be totally necessary to have a depth sounder. I suggest contacting the "Home of the Flicka 20" website below and asking for their suggestions. If you must have a depth sounder I'd suggest attaching a transom mount one to a stick down from the stern. This may be possible with the one you have brought or it may be possible to exchange it.

Quote:
2. Are any of you familiar with Ryan Marine and the Ryan Marine Flicka?
I have no knowledge of Ryan Marine. The ferro cement Flicka that I remember is a Bruce Bingham design that was published as a series of articles in Rudder Magazine - March 1972 -August 1973. Apparently Louisiana State Library has the issues so you may care to contact them if you need detailed information.
I would consider it very likely that your Flicka was constructed by an amateur from the Rudder magazine plans. Many ferro boats were professionally plastered so it may still present very well.

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3. Any and all positive advise will be appreciated.
An overview of the Flicka 20 may be found here.
There is a website devoted to the Flicka 20 "Home of the Flicka 20" which has much information that may be of interest, though its main focus seems to be on the fibreglass production versions.

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The boats new name is Wren as she had no name when I bought her!?!
A lovely name. There is a facility on the "Home of the Flicka 20" website above for owners to register their boats so you may care to register your boat with them if you do determine that it is a Bruce Bingham Ficka.
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Old 28-06-2011, 17:33   #7
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Re: Cut a Hole in Ferro Cement

They make carbide tipped hole saws for concrete that will chew through rebar as well so a ferro hull would be no problem. A contractors rental store should carry them
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Old 28-06-2011, 18:00   #8
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Re: Cut a Hole in Ferro Cement

Make sure you use a dry drill and then seal the opening very well as the biggest problem with ferro cement construction is water intrusion into the armature. Water will migrate along the substrate and cause rust and electrolysis. As iron expands 800 per cent with rust this causes the plaster to crack, allowing more water intrusion and more rust, repeat process until hull is scrapped due to the plaster popping off in big chunks.
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Old 28-06-2011, 21:52   #9
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Apres drill...

Maybe I should have mentioned that after drilling you need to treat any rust (phosphoric acid?), seal the exposed ferro with epoxy resin and build up as applicable with epoxy putty.
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Old 28-06-2011, 23:35   #10
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Re: Apres drill...

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Originally Posted by Boracay View Post
Maybe I should have mentioned that after drilling you need to treat any rust (phosphoric acid?), seal the exposed ferro with epoxy resin and build up as applicable with epoxy putty.
Do not put phosphoric acid any near a ferro cement boat,it eats lime and destroys cement
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