Osmosis
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Liftout_on_04_December_2005

   

At the end of 2004 a quick check of the hull, below the waterline indicated signs of osmosis by the fact that very small 'bumps' had formed in various places across the hull. A moisture meter check confirmed that the relative moisture content between the hull above and below the waterline. I got a general reading of 15 upper hull and >30 lower hull.

After researching the many sources of information I decided to call the experts at International, having once worked in their aviation paints division. I spoke to Richard Jerram, Technical Manager for yacht paints richard.jerram@internationalpaint.com
My next course of action was to skim off the gel coat to reveal any voids and to open the blisters.

At this stage I decided not to remove all of the gel but to get to the worst of the osmosis and treat that with International's Gelshield Solvent Free Epoxy treatment as per the advice sheet provided by International. See extract pdf.
These images were taken after blasting off the hull using an industrial high pressure washer at close range to open out any voids.

The image on the left shows osmosis damage worse than I expected; three layers of fibre matting were removed. Indications are that part of the problem was caused by having voids in the layup.  Once the decision was made that the problem was worse and needed sorting I considered all the options of forced drying under cover, dry ice blasting and other options but chose natural drying after gel planing, grit blasting and hot power washing. I contracted Advanced Osmosis Treatment (Adrian Baker & Paul Baker) to do the job with a self help plan. The estimated cost ~ £2450.00 plus ~ £400.00 for Copperplus antifouling.

All skin fittings that could be removed were and the yacht supports moved well above the waterline. I was a little concerned that the boat could force the cradle to open up so decided to put scaffold cross members in to help prevent any problem. The 14' scaffold poles cost  £0.60 per foot and the swivels  £1.50 each from RBS Scaffolding in Hedge End enquiries@rbsscaffolding.co.uk

Gel coat peeling was carried out by Advanced Osmosis Technologies. Adrian Baker is an expert in the art of gel coat removal and can be contacted on 07885 175 534. I managed to keep costs down by agreeing a joint effort between he and I. The cost of gel coat removal, including rudder, was < £500.00. This part of the project took 1 day. I was impressed by the standard of work.

On the left is shown the rudder. This was found to be suffering badly from osmosis and water ingress. Holes have been drilled in the rudder to assist draining of any liquid.

The picture on the right shows the galley sink / fridge heat exchanger outlet in place. This was deemed too difficult to remove. The area was ground out to remove the gel coat using a 4inch grinder.

The picture above shows the boat covered from end to end in scaffolding sheet on the upper part and a temporary dust screen on the lower part for the purpose of the surface blast cleaning. This process removes any softer material and roughens the remaining surface to aid drying out and keying.The scaffold sheeting was ideal to make the cover as it comes in a 45m x 2m roll for ~ £90.00 from  RBS Scaffolding enquiries@rbsscaffolding.co.uk.

The sheets were joined by 'stitching' through the holes provided with plastic washing line.In the picture on the right Paul Baker of Advanced Blast Cleaning Tel: 02380 620493 or mob: 07970 407911 can be seen blast cleaning the hull. I also had the keel blasted to bare metal and treated with 'Fertan'. http://www.fertan.co.uk/

 Cost ~ £400.00 Process time 1 day.
It is vital to screen the process to prevent dust from collecting on other yachts, however, Paul spent considerable time in the preparation and cleaning up operation.
I was very satisfied with the work. Once all the blast material was cleared 5m lengths of 10mm fibre glass rod were threaded through the lower edge of the scaffolding sheet to spread any load from high winds and to allow guy ropes to be attached from the sheet to the cradle. 

Sunday 6 February 05 the yacht hull below the waterline was pressure washed with the water temperature set to 85oC. This removed any dust from the blast cleaning and any residual chemicals related to the osmosis that had been exposed by the peeling and blasting.  The images to the right show the effects of the blasting on the hull. The keyed surface is now in the process of drying out naturally with the temperature on the inside of the boat at approximately 28Celsius.
The keel images show the effect of using the Fertan treatment. The white patch is filler used by Westerly to cover casting cosmetics. The images below show the method used for drying out the rudder. The heater is a Clarkes Model 360 Infra Red heater drawing 2.4KW. The advantage of using this type of heater is that even when the airflow (wind) or environment is cold the target will absorb the heat.
The image below shows the filler applied around the waterline. This will be faired off to produce a step free interface above and below the peel line.
     
     

Left - Adrian Baker keys the waterline filler ready for the first coat of epoxy primer. Epoxy clear primer applied by roller, making sure all the pores are wetted ready for the next coat.

Note that the masking tape is the type that can be left on, without the problem associated with trying to get the stuff off on completion of coating the hull.

On the left, the primer coat is applied. note that the surface is relatvely smooth but will require further work at a later stage.

 Image on right shows 1st coat of epoxy applied over primer. Note that care is taken to fill any voids. To make it easier to apply further coats each coat is a different colour - in this case dark grey and light grey.

 

   

A good tip is to use a bin liner for containing the paint tray. On completion of the coating you just ditch the liner and off you go again. Each coat was allowed to become 'tacky' prior to commencement of the next coat.

Once the hull was covered with three coats of epoxy the next mixing was made up using 1/3rd of microspheres to make the mixture the consistency of whipped cream. we prepared 'plaster tables' for each side of the boat and three of us, Adrian, myself and Christine took our applicators in hand.

The picture on the right shows the method of applying the 'paste' which is relatively easy to apply but needs a little skill to produce an even coating.

 

 

 

After considerable 'huffing and puffing from the 'apprentices' and a little prodding and guidance from the specialist (Adrian) the days work was completed at 7:30 pm - a long day from 08:30am.

The cover was finally drawn at 7:30 as shown on the right.

The next stage in the process is to fair and flat off the surface. Adrian recommended using a 6inch random orbital sander with 40 grit paper followed by the use of a half sheet sander using 40 grit paper.

It is important to use an effective face mask, eye protection and coverall with hood for this work. I also used gloves and fitted the dust extraction bags to the sanders which were frequently cleared.

The sanding process took 2 full days to complete and was an arm aching task. The most important sander to use is the 1/2 sheet orbital, the finish will be noticeably better than with other sanders.

 I managed to get an old adjustable office typists chair to sit on in order to 'attack' the underside. I covered it with bin liners to protect it from collecting too much dust.

To identify any low spots I used a flexible 'straight edge', marking off any low areas with a marker for filling at the next stage. Another way to assess the surface finish is to view it with the light striking the surface at a shallow angle and look across the surface.

On the left is a picture of the rudder which shows the low areas to be filled prior to applying fibreglass weave and subsequent epoxy coatings.

On the right the picture shows that the fairing off process will work through to the epoxy coatings of a different colour. This is quite normal to expect. Date 14 April 2005. 

The penultimate operation! First a coat of primer followed by three coats of epoxy. Judging the thickness to roll on the epoxy required a bit of training from Adrian, but then it went fine. I have to say that the job is not for the weak; trying to get four coats on in a day and my shoulders feel like I have been hanging by the arms!

On the right the picture shows a lighter coating of epoxy antifouling tie-coat primer. Fairly easy job similar to putting ordinary antifouling on, and took about 1.5 hours plus the time to get a short pile roller that did not disintegrate when used with the coating.

 

Once the coating was finished the tent was secured to prevent any rain getting on the surface and tight enough not to blow onto the surface. This coating will be left for at least three days before the antifouling coating process is started. The rudder will have a layer of glass fibre layed up prior to antifouling too.

The antifoul will be left for about ten days before the boat can be launched. This should enable all the skin fittings to be re-fitted using new pads.

1st week of May. Above images show epoxy primer applied and subsequently faired off and also show the rudder laminated with 40grm/mtr fibre weave, filled and faired off.

Images on the left and right show first application of CopperPlus followed by the second coating below left. Note the rudder on left has an application of light blue epoxy primer prior to the CopperPlus being applied. more to follow...

 
     
     
 
     

Lift-out Sunday 10 sep 2006

Inadee was launched in May 2006 after the bottom was refinished with CopperPlus by Adrian Baker. The following photographs show the condition of the bottom after only 3 months in the water.

Lift-out Wednesday 6 Dec 2006

After 3 months since 10 September, Inadee was again lifted out and, as the photos show, the fouling is quite unacceptable.

Removal of the fouling using conventional pressure washing is in fact a little harder that when conventional anti foul coating have been used. The white worm deposits have to be removed mechanically. There are areas of dark fouling where it proved impossible to get back to the hull coating with just the pressure washer. Adrian Baker has copies of the images and requested to comment at his earliest opportunity. I will report here.

The image on the left shows the epoxy coating lifting from the keel with fouling under the coating.

Both sides of the keel show the same problem. The pictures were taken after the hull and keel had been pressure washed.

The moisture readings taken after lift out are very good and indicate that the epoxy coating is working very well.

Sunday 6 Feb 2007

Since December 2006 Inadee has benefited from work on the hull, below the waterline. The whole of the underside was cleaned using a hot water scrub, a devil of a job undertaken by Adrian Baker of Advanced Osmosis Technology. The damaged finish on the lower part of the keel was repaired and a primer used in preparation of coating with Seajet Emperor antifouling. The pictures below show the finished work done by Adrian, and I am very pleased with the results so far.