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S&S Swan Maintenance - Hull
30 September 2016 - 21:48
#1
Join Date: 03 February 2011
Posts: 39

Hull

The boat has been in water two winters now and underwater polyester materials is soaked even well coated.

Plan is to haul boat  this year. It might well be only few weeks from hauling to temperatures get to below zero.  then likely few days above before dropping below again.

so ask what would be the better;  keep hull in water and undertake general maintenance in spring and then haul early september next year.  Are there any specific recommandations to such care taking?  

 

Ravn 411/36  Thorbjorn

30 September 2016 - 22:05
#2
Join Date: 03 February 2011
Posts: 39

The boat has been in water two winters now and underwater polyester materials is soaked even well coated.

Plan is to haul boat  this year. It might well be only few weeks from hauling to temperatures get to below zero.  then likely few days above before dropping below again.

so ask what would be the better;  keep hull in water and undertake general maintenance in spring and then haul early september next year.  Are there any specific recommandations to such care taking?  

 

Ravn 411/36  Thorbjorn

water is very rarely below zero,  South Norway.  if so, hull can be kept free with in-hull heater,

this  a polyester concern.  

Few years back  it was a freezing temperatures for six months,  at the time Climate Conferende collapsed in Copenhagen.  Environmental protection gets to carry wooden fuel to the fire place some times.  Ravn 411/36  Thorbjorn

 

02 October 2016 - 20:25
#3
Join Date: 02 January 2008
Posts: 1547

Dear Thorbjörn

If you want to have a dry interior in the winter it is necessary to avoid moisture condensation inside the yacht. To keep the air dry take care that there is absolutely no water in the bilge, and also do not cook or stay on board. 
 
The moisture content in the air inside must be low enough, so the dew point is never reached even when the temperature drops to winter readings. A psychrometric chart is required for assessing the situation in detail, but if you are not familiar with such things you can leave it to me to explain what is needed in terms of humidity and temperature.
 
One way to approach this is to replace the moist inside air with dry outside air when the cold weather arrives. If you have an air borne heater which can be run in ventilation mode this is sufficient for replacing the air, pls note that using heating mode does not change the amount of moisture, only makes it more pleasant inside.
 
The other possibility is to dry the air inside the boat, i.e. remove moisture with a dryer, for this subject pls look for example here
 
For this answer I consulted with Swan 411 owner Daniel, who is THE authority on these things.
Kind regards
Lars

03 October 2016 - 10:59
#4
Join Date: 30 January 2007
Posts: 461

Dear Lars, you are too kind!  I am not an authority in these matters and when we discussed them, it was very clear that you know as much as I do. It is always interesting and useful to discuss technical aspects together and I am very glad that we agree most of the times!

...when we do not agree, it is very likely that I am wrong! :-)

Daniel, 411/004

08 October 2016 - 13:07
#5
Join Date: 03 February 2011
Posts: 39

Many thanks Lars and Daniel, for good advise.  There is a problem keeping bilge entirely dry when boat in water over winter, since some water seem to get through halyard exits on mast when rain/wind.  When taking out cushions etc and keep a small fan with heat running, it gets pretty dry.  Since cold air normally gets drier, its less moisture below deck in wintertime than in summer.  (Summer normally 70%, winter sometimes down to 30 according to an instrument there)

Even when no damages to hull below waterline, some water gets into its gelcoat/polyester materials? when hull is in water over long time. Isn`t that right? If one then puts boat in dry lay-up and temperature drops to say minus 10 deg C for weeks, can that give any damage to hull-materials.  Some winters we have steady north-easternly wind from Siberia, dry and cold, like in Finland (?) so very much look forward to hearing your view to this Lars and hopefully also Daniel.

Thorbjorn/Ravn 411-036

 

09 October 2016 - 20:24
#6
Join Date: 02 January 2008
Posts: 1547

Dear Thorbjörn

You are right that some rain water enters through the mast. This can be prevented by covering the mast openings, or building a watertight dam inside the mast.
If you have a hygrometer on board you can easily determine the dew point using relative humidity and actual temperature as input for a dew point calculation. You can find a calculator for example here  http://www.dpcalc.org/
 
If the bottom has a proper barrier coat on the outside, the moisture slowly coming through it migrates to the inside and evaporates faster than coming in, provided there is dry air above the dew point inside, and good ventilation of the bilge. Then the laminate is not saturated with water, and does not suffer from freezing. Keep floorboards open and the yacht well ventilated.
 
Yes, we have Siberian winter now and then in Finland, but I am not aware of any laminate damage to bottoms ashore, except for cases where there has been water standing in the bilge in freezing conditions. In order to prevent this just open the bilge drain plug.
If the bottom has developed blisters - I believe there are not any - they contain a mixture of water and glycol or acetic acid, and this prevents them from freezing.
Kind regards
Lars

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