There will be no class on the 13th March. This session will now be added on to the end of the course, the last lecture of the course is now on the 19th June.
I know that this was to be the first session to have one case study completed and to receive feedback. we will cancel that feedback until 27 March when you should have 2 case studies completed
I will post an overview of information that will help you with study for this week.
Dave Pascoe discusses the replacement of leaking windows in an article on his website.
www.yachtsurvey.com/WindowRepair.htm
Aluminum window frames for boats usually have the window sealed into the frame by the manufacturer. The boatbuilder or repairer would normally expect to seal the frame into the window recess. At some point in the boats life the glass itself may need re-sealing into the frame but its more likely with good quality window frames that the aluminium into the recess is the problem. This is the scenario I had imagined for the case study.
Windows are sealed into rebates by the builder or Repairer. What is the most successful method? There are different ideas for the shimming of windows to retain a sealant thickness, I like to use 4mm x 6mm dam rubber which is a rubber tape that has a sticking surface on two sides (the 4mm side) which holds the window away from the surface its being bedded to. This method holds the window 4mm away and allows sealant of that thickness to be applied. The rebate needs to allow the correct depth
Some builders/repairers prefer to remove sealant with a blade when it has cured. the other way is to mask the clean up surfaces, this can also be successful
Take note of the importance of movement, it could be expansion and contraction, or structural
Wednesday, February 29, 2012
Monday, February 27, 2012
March 6 Field Trip
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| These pictures shows a copper tank which has been in contact with timber What is the cause of the problem? |
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| The rotten timber has been cut away from the planking, it still remains in the area of the keelson |
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| The exposed planks show that the inside skin is laid diagonally, the outside skin is fore and aft (carvel), this is not a glued structure |
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| The top of the keel and keelson |
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| The rotten timber has no strength left it must be totally removed. Think about how new timber could successfully be attached to the undamaged planking |
We travel to Brin Wilson Boats next week, they are the only boatbuilding yard that is permanently situated in the marina area at Gulf Harbour. They are experts in the repair of glass laminate and wooden boats, much of their work is for insurance companies, this work is handled by a loss adjuster (assessor) representing the client and the insurance company.
They also undertake repair and alteration work for pleasure and commercial boat owners. To be successful in attracting insurance work they must be able to work to a fixed price, complete the jobs to a high standard, and be able to salvage damaged boats as required. the Travel lift operates directly into their factory, however they do move boats around without the aid of the lift which is a necessary part of a successful operation.
They also have a company which operates independently in the yard at Gulf Harbour which is Osmosis Solutions, they are responsible for the repair of the problem known as Osmosis.
What you can expect to gather information on are hardstand support systems, the operation of a Travel lift and a low loader, Osmosis repair, various jobs that will be taking place in the yard
You will be expected to photograph or video useful and interesting information, and participate in group discussion during the following lecture session
We leave outside the Marine Workshop at 12:30
Tuesday, February 21, 2012
Welcome Aboard Shipmates
This is my blog which I would like you to follow, comment on, and use as another method of collaborating with me and your classmates, if we can all learn together that is the aim, don't leave anyone behind and if you are unclear on something you need to ask.
The first session is Tuesday the 28th of February 2012 12:30 to 4:00 we will talk about what the assessment is all about, the Field trips we do, your expectations and mine from the course
This is the opportunity for you to understand what the assessment instruction is telling you to do
Osmosis avoidance, detection, treatment
Osmosis-Is a problem with fibreglass hulls built from polyester resin... The problem is that water is, able to make its way through the gel coat and in to the fibreglass laminate. Gel coat is not completely waterproof, water penetration does occur. If the water is able to find its way into any air bubbles or small voids that have been left behind from the laminating process it will mix with chemical residue (styrene, MEKP, etc) to form a dense acidic liquid. Because that liquid is more dense than the seawater on the outside of the hull water is drawn from the outside into the void in an effort to equalise the pressure difference, the result is that the void pressurises and forces the outside layer into a blister which shows on the outside of the hull often when the hull is removed from the water a dark liquid can be seen forcing its way back out through the laminate, or gel coat. The blister is actually a small delaminated section of hull, sometimes just under the gel coat but often into the outside layers of CSM depending on the lay up. The process of water penetration is called osmosis and is the same process used in nature by plants to transmit water from roots to leaves.
Avoidance-FRP boats these days are not as prone to osmosis as they were some years ago. Boat builders have realised that they put their product and company name in jeopardy by using cheaper materials and taking shortcuts in production. Hulls that don’t have osmosis problems have a sealed laminate, they use vinyl ester, or isothalic polyester resin rather than orthothalic Quality control the temperature, the humidity, and take good care to lay up using proven techniques. The underwater surface should be sealed with a good thickness of epoxy paint prior to antifouling
Detection- Is not always straight forward, the best way is to view the bottom of the boat when it is first hauled out, and by looking along the wet surface the raised blisters will show up and should be marked. Often as the hull dries the blisters quickly disappear. This is because the surface has been softened and the liquid is allowed to escape as the water is no longer pressuring on the outside of the hull. This will happen quite quickly as the hull dries and often only one hour after haul out the blisters have disappeared. The problem is still there it’s just difficult to individually locate them. Sound tapping with a hammer will find the blisters as they are just small delaminated areas. Often so small that it’s difficult to cover the entire surface with a hammer and feel confident all the blisters have been located. Antifouling should be removed to be sure of finding the full extent of an osmosis problem.
Repair-There are only two proven methods of repair. The first is to remove the affected area of each blister individually, dry out and epoxy fill which is considered as damage control rather than repair. Or the second method is to plane the surface of the hull down to a level where the laminate is healthy (sometimes that is not possible), dry out and re laminate with a resin rich matrix back to original thickness. This is often done with vinyl ester resin and sealed on the outside with a good thickness of epoxy paint.
The first session is Tuesday the 28th of February 2012 12:30 to 4:00 we will talk about what the assessment is all about, the Field trips we do, your expectations and mine from the course
This is the opportunity for you to understand what the assessment instruction is telling you to do
Osmosis Repair
Osmosis-Is a problem with fibreglass hulls built from polyester resin... The problem is that water is, able to make its way through the gel coat and in to the fibreglass laminate. Gel coat is not completely waterproof, water penetration does occur. If the water is able to find its way into any air bubbles or small voids that have been left behind from the laminating process it will mix with chemical residue (styrene, MEKP, etc) to form a dense acidic liquid. Because that liquid is more dense than the seawater on the outside of the hull water is drawn from the outside into the void in an effort to equalise the pressure difference, the result is that the void pressurises and forces the outside layer into a blister which shows on the outside of the hull often when the hull is removed from the water a dark liquid can be seen forcing its way back out through the laminate, or gel coat. The blister is actually a small delaminated section of hull, sometimes just under the gel coat but often into the outside layers of CSM depending on the lay up. The process of water penetration is called osmosis and is the same process used in nature by plants to transmit water from roots to leaves.
Avoidance-FRP boats these days are not as prone to osmosis as they were some years ago. Boat builders have realised that they put their product and company name in jeopardy by using cheaper materials and taking shortcuts in production. Hulls that don’t have osmosis problems have a sealed laminate, they use vinyl ester, or isothalic polyester resin rather than orthothalic Quality control the temperature, the humidity, and take good care to lay up using proven techniques. The underwater surface should be sealed with a good thickness of epoxy paint prior to antifouling
Detection- Is not always straight forward, the best way is to view the bottom of the boat when it is first hauled out, and by looking along the wet surface the raised blisters will show up and should be marked. Often as the hull dries the blisters quickly disappear. This is because the surface has been softened and the liquid is allowed to escape as the water is no longer pressuring on the outside of the hull. This will happen quite quickly as the hull dries and often only one hour after haul out the blisters have disappeared. The problem is still there it’s just difficult to individually locate them. Sound tapping with a hammer will find the blisters as they are just small delaminated areas. Often so small that it’s difficult to cover the entire surface with a hammer and feel confident all the blisters have been located. Antifouling should be removed to be sure of finding the full extent of an osmosis problem.
Repair-There are only two proven methods of repair. The first is to remove the affected area of each blister individually, dry out and epoxy fill which is considered as damage control rather than repair. Or the second method is to plane the surface of the hull down to a level where the laminate is healthy (sometimes that is not possible), dry out and re laminate with a resin rich matrix back to original thickness. This is often done with vinyl ester resin and sealed on the outside with a good thickness of epoxy paint.
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