Watertank
We are in the process of cleaning the watertank. By doing so we noticed some dimples on the walls. Osmosis? Does anyone have noticed something similar?
These dimples are likely signs of osmosis in the internal fiberglass water tank. This is a known problem in many Nic 31's. I know of one owner who cut the entire top of his tank open, ground out the blisters , faired and epoxied the inside of the tank much as you would do an external blister repair on the hull.
Re: Watertank
Thank you for your comments. Do you know if the watertank is part necessary of the keel structure (contributing to the hull strength) or is it a separate item?
peter foston
Unregistered User
(15/7/05 10:36 am) Reply
water tank
Hi I had the same blisters when I bought Khamis 9 years ago.
She also had exterior osmosis "in spades'. My surveyor said do the main osmosis but so long as the blisters do not start to burst I would leave them.
I haul her out every winter and dry the water tank out completely leaving the cover loose to allow air to circulate and they do not seem to have got any bigger or increased in number.
I have whale water filters on both the galley and heads water taps which are changed annually.
In the event of trouble I intend to measure up aand fit a flexible tank.
Re: water tank
Thank you Peter. I have now also emptied the tank and left the 2 access lids open. I will see if the number of dimples increases with time and if some will burst.
aahshowa
Unregistered User
(26/7/05 6:28 am) Reply
water tank
The water tank was made separately and then installed in the hull. There are supports underneath the tank to allow any water from the chain locker to drain aft to the sump. I know of several Nicholson 31s with blisters in their water tanks. One owner had a brown substance leaking from the blisters and was told by Camper & Nicholson not to drink the water. Several owners are planning to install a liner to go inside the tank. One owner was going to have a plastic liner made by Hovercraft Consultants Ltd. Tel +442380871188. Remember though, that the Nicholson 31's original water tank held 75 Imperial Gallons but when Camper & Nicholson went from a lead keel to part lead and part iron, the tank was reduced to 62 Imperial Gallons. If you have further questions, I recommend you contact Jeremy Lines as I have. He has been an excellent source for information. Annette
I am currently looking into acquiring a Nicholson 31. Do you know what the hull number was when the lead keel to lead / iron keel change occured? This was a very interesting detail I had not been aware of.
Thanks,
Thomas
aahshowa
Unregistered User
(28/7/05 4:02 am) Reply
Change of metal in Keel
Hi Thomas,
I don't know when that changed. I suggest you go to the Technical Section and get the information to contact our Voluntary Archivist, Jeremy Lines. He is a wealth of information as I believe he was in charge of the production of the Nicholson 31.
As the owner of hull #5 and knowing owners of several other Nicholson 31s, there were a number of changes made as this model was produced. The type of metal for the keel was not the only change.
Annette
Tony Irwin Regular crewmember
Posts: 37
(3/10/05 12:12 pm) Reply
Re: Change of metal in Keel
I spoke to Jeremy Lines at the Meet in September about the lead/iron change. He said that only a part of the keel was changed, making no alteration to trim. The ballast is and always was in three pieces. The foremost part, under the mast, remained lead, but the two parts further aft were changed to iron. reducing the space available for water from 65 to 54 gallons.
Tony
Water Tank, Lead to iron ballast
With due respect for Jeremy ( he's been very helpful to me on several issues), I don't know that this information is 100% accurate. My Nic 31 has the original water tank. It holds approx. 92 US Gallons which is much higher than the capacity you noted on earlier models ( even if you convert from US down to Imperial gallons). I have filled it from empty many times at metered filling stations when purchasing water and am sure the 92 gallon capacity is accurate.
An interesting issue is the increase in ballast weight and displacement that occurred during the production of these boats. The ballast increased, displacement weight increased, and water tank capacity decreased. I believe that the tank capacity had to be decreased to accomodate additional ballast in the form of iron instead of lead; the iron would require more space. Also, the masts on later models appear to be of lighter construction than the earlier models.
Tony Irwin Regular crewmember
Posts: 38
(3/10/05 5:09 pm) Reply
Re: Water Tank, Lead to iron ballast
You may well be right; however, he did emphasise strongly that while the ballast volume increased because of the change from lead to iron, the displacement and trim remained unaltered; the centre of gravity did not rise higher than it had been before. I have never measured my tank, but I will do so at the next opportunity to see exactly how much it holds. He showed me drawings of the ballast arrangement and these are available from the Association.
Tony
Water tanks, Ballast
Tony,
I am looking at a Nicholson 31 Spec sheet from C&N entitled: Specification Mk II. Displacement is listed by C&N as 5898 kg or 5.8 tons. It also shows the tankage as approx. 282 gallons ( 62 Imperial Gallons or 74 US gallons). I also have the same C&N brochure for the Mk IV. In it , C&N lists the displacement as 6700 kg or 6.6 tons; water tankage is listed as the same.
I also have a reprint of a Yachting World article ( from Dec. 1976) that reviewed the Nic 31 when she was introduced in 1976. In the article, they state that " the keel consists of 2180 kg (4800 lb) of lead,encapsulated in GRP". they show the original diaplacement to be the same as listed for the Mark II above.
It's all a little confusing. My boat (hull 00 is either a Mark I or Mark II version; I'm not sure which one, but I am certain that my water tank holds the 92 US gallons (76.6 Imperial Gallons). I used to complain when I purchased water from metered filling stations when I would be charged for 90-92 gallons and I was sure that I held less than that. After numerous fillings at many different metered locations, I changed my tune. The C&N spec sheets are wrong.
It would be interesting to find out how the displacement
increased in any way other than eliminating tankage and adding the lead. I've always been curious about this issue. Maybe Ray Wall could clear this up. I believe he actually headed the C&N design team for this boat.
Re: Water tanks, Ballast
Tony,
I've got the drawings and I'm no engineer, however:
Here's something I find interesting.
1. The difference between the stated displacement of the Mark II ( 5898 kg) and the Mark IV (6700 kg) is 802 kg or 1768 lbs.
2. The volume difference between my actual tankage ( 76 Imperial gallons) and the stated tank capacity ( 62 Imperial Gallons) is 14 gallons.
3. 14 Imperial gallons equals 2.247 ( let's round up to 2.25 to make the math easier) cubic feet.
4. 2.25 cu. ft of fresh water weighs 140 lbs; 2.25 cu. ft of cast lead weighs 1593 lbs & 2.25 cu. ft of cast iron weighs 1013 lbs.
5. If you exchange the same 2.25 cu. ft of water tank capacity by reducing the tank size and adding 2.25 cu ft of cast lead instead, the added difference in weight is 1453 lbs.
6. This is close to the displacement discrepancy between the Mark II and Mark IV as stated in the C&N specs.
7. If the displacement on a boat like ours increases by between 1453 and 1768 lbs and the hull shape doesn't change, it would seem that the heavier boat would definitely sit lower in the water all other things being equal.
Harrison
Tony Irwin Regular crewmember
Posts: 39
(4/10/05 9:27 am) Reply
Re: Water tanks, Ballast
Yes, I am sure you are right; however, I understood that the original displacement figure was merely a designed, calculated figure, while the later figure was an actual measurement, the difference being the heavier lay-up etc resulting in a heavier boatthan had been intended. The drawings listed in the Member's Area of this website show details of the constructional changes when the ballast was changed. The reason for the change was the unpredictable movement of the price of lead in the late 1970's and early 1980's, which cost C & N a lot of money.
Tony
Water Tank & ballast
Tony,
Thanks for the info. I've always wondered about the change in displacement numbers on the spec sheets. I also can understand the change in ballast from lead to iron to save costs as time passed. I guess that my larger than specified water tank capacity comes from the yard building the tank to fit into the keel area and not necessarily from the design drawings. As often is the case, production doesn't always rigidly adhere to design.
I consider the larger water tank a plus, especially as I use my boat for liveaboard cruising in the tropics. Since I have the larger tank and my boat is an early edition, I also must have the all lead ballast. Jeremy sent me the actual production notes for my boat;however, these notes don't address these issues.
Harrison
Re: Water Tank & ballast
Good info many thanks.I'm considering grinding out the blisters in my tank and making good with plastic padding gel repair I can see its going to be a dirty messy and extremely awkward job but it needs to be done as some of the blisters are weeping an amber fluid.
Tony Irwin Regular crewmember
Posts: 42
(18/10/05 4:48 pm) Reply
Re: Water Tank & ballast
My tank has blisters but no amber fluid. Instead of trying to stop the blisters, I fitted a really high quality water filter and a separate tap for drinking water. The water is better by far than tap water and we use it to add extra flavour to our Malt whiskies! The ordinary filters are OK for other use.
Tony
bobvitaliusstroudwatercom
Unregistered User
(30/11/05 3:20 am) Reply
Watertank Blisters
I have a contract on a Nic 31. We do have some problems with blisters in the watertanks. A few are open. Can they be ground out and coated with epoxy? Any thoughts?
Bob V.
aahshowa
Unregistered User
(7/12/05 11:10 pm) Reply
Watertank repair
Hi Bob, When I was cruising I did hear of an epoxy type material sold in Canada that can be used for painting the tank. I was told it was toxic in it's liquid form but non-toxic when it dried. It was not a concern of mine so I didn't get anymore info. Wish I had! Maybe you can surf the net and check. If you do find it let us know. And congratulations! Alex owned Anadromous from the time it was built and took good care of it. Annette
Re: water tank
I had the tank liner made by Hovercraft consultants. It's a very substantal construction specifically in a material for boat watertanks. It's been in now 3 years and I'm very satisfied. Along with replacement of pipework it makes for a really "fresh" installation with no risk of any progression of blisters from the "inside, out".
I don't think it made much of a difference to tank capacity for general cruising though if you were planning a really long cruise you'd need some extra water anyway.
is either a Mark I or Mark II version; I'm not sure which one, but I am certain that my water tank holds the 92 US gallons (76.6 Imperial Gallons). I used to complain when I purchased water from metered filling stations when I would be charged for 90-92 gallons and I was sure that I held less than that. After numerous fillings at many different metered locations, I changed my tune. The C&N spec sheets are wrong. 
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