Instruction for use Pikanto hull made by Robert Grubiša
Care of moulded items - excess heat
Epoxy resins offer significant advantages in strength, stiffness and adhesion to fibre reinforcements, over the more commonly used polyester resins. Like most resins they attain 90% of their ultimate strength relatively quickly but curing continues, dependent on temperature, for days, weeks and even months. Distortion is resisted by epoxy mouldings until the temperature exceeds the original curing temperature (normally 20 to 30 degrees C) when further curing takes place leading to minor distortion. Larger distortions will occur if the moulding is loaded when it is heated, for example, if the full weight of the yacht is being taken by the slings of a stand onto the hull rather than onto the keel.
A large proportion of heat damage to our mouldings has occurred in the back of cars when, even on overcast days in the summer, sufficiently high temperatures can be reached. A thin white cloth laid over the hull in sunny weather gives good protection. Do not place thick blankets over the yacht.
The thinner and lighter weight mouldings will heat up and distort far quicker than heavier mouldings. Darker colours are affected more as they absorb ultra-violet light better. If the long term appearance of the surface finish is important to you, pay particular attention to keeping the hull cool.
Take the following precautions:
Preparation
• specify a lighter coloured gel coat
• spray the fin and rudder with grey primer or, even better, white primer
On hot or sunny days
• keep out of direct sun whenever possible
• avoid placing the hull on hot surfaces
• support the fin and ballast evenly when the boat is placed on its side
• remove the rig and place boat in a stand between races
• slacken rigging loads if there is a long time between races
• do not leave the boat in the car without adequate ventilation
Care of moulded items - excess moisture
The very fine glass fibres absorb moisture very quickly if they are not protected by resin. Hand laminated hulls have a very thin gel coat to keep weight to a minimum and this gives very little protection against moisture absorption.
The inside of mouldings are not given a further coat of resin (as are most mouldings intended for marine use) as this would have a serious detrimental effect on the stiffness/weight ratio. Indeed reinforcement cloth usually has as much resin removed from it as is possible to lighten the lay up. This tends to create small air voids in the lay up which further increases the likelihood of moisture being trapped in the reinforcement cloth.
Cases of osmosis have occurred from time to time when storage conditions have been ideal for this to happen. It is of paramount importance that hulls are not left with water inside after sailing. Hulls should be stored between use in a dry condition and with the servo/winch patches removed to allow ventilation. Moisture will be trapped between the fin box and the fin (and the fin and the ballast) for some considerable time after sailing and will lead to osmosis on the matching surfaces. Where possible you should dismantle fin and ballast after use. Do not trap moist air in the yacht by
covering with a cloth between use.
Take the following precautions:
At events
• avoid laying a hull on warm damp grass
Between events
• remove the centre deck patches to allow ventilation
• store hull in a dry condition
• do not leave damp cloths resting on the hull
• dismantle fin from fin box
• dismantle ballast from fin if possible
Leaks
Unfortunately it is almost certain that boat WILL take water on board when sailing. They are tested before leaving the workshop to see that the hull itself does not leak but there are several other areas where water gets in:
• winch sheet exit and return tubes
• rudder trunking
• sheet post trunking – not a leak source if the post is locked properly
• small holes under deck patches especially at joins between the hull shell/deck
• possibly through the deck patch material itself – tests have not indicated that it leaks
All of these factors are accentuated when a warm boat is placed onto the water and the air inside it is quickly cooled thus creating a suction.
The sheet post trunking has to have a small hole drilled near its lower end so that pressure created when the sheet post is pushed in does not force the sheet post back out of the trunking to foul the main boom.
Maintenance
After sailing on salt water it is important to flush out the hull with fresh water. Note the precautions to be taken to avoid osmosis. Clean dirt and grime from the hull using soapy water, methylated spirits and/or acetone.
The colour restoring polishes intended for cars are quite good at restoring the gloss where this has been scuffed.
If the surface finish of a hull develops the print of the backing reinforcement you can restore the original hydrodynamically smooth surface by rubbing down with 600 grade wet or dry abrasive paper. Use masking tape to delineate the waterline
(there is little point expending energy on the topsides unless their appearance is critical) and use a small block of smooth wood or plastic to mount the abrasive paper on. There is probably very little point in using a finer grade paper than 600 on the hull, but if you are keen, use 800, 1000 and 1200 grades in sequence on the forward 50% of the fin, hull and rudder in order of priority.
Expect to repeat this process every year at least. Do not apply any wax or other surface treatment in an attempt to reduce skin friction - the only ones that work are not permitted under RRS 53. The commonly available static friction reducing polishes only increase the likelihood that you will drop your yacht.
Minor cracks in the gel coat where the hull structure behind is not seriously damaged are normally best ignored. More obvious cracks are normally associated with failure of the backing reinforcement. In these cases the material along the crack should be ground or filed out to allow the hull to return to its original shape at the earliest opportunity. This ensures the repair will not be so noticeable when it is made. Having done this you have two basic choices a) send the boat to us to repair and b) repair it yourself as below. In either case it may be as well to put tape over the hole and race
until the end of the season when you can deal with all the damage at the same time.
Maintain as follows:
After sailing in salt water
• drain water from hull, wash out inside with fresh water
• wash outside of hull with fresh water
• remove the centre deck patches to vent the hull
• wash/spray all rigs and sails with fresh water
After sailing
• clean off any dirt with warm soapy water, methylated spirits, alcohol or acetone
• remove the centre deck patches to vent the hull
After damage
• cover minor cracks of the gel coat with tape
• cut away the fractured fibres of more obvious cracks and cover with tape
• repair damage at end of season
Repairs
For minor cracks in the gel coat where the hull structure behind is not seriously damaged
The area inside the hull surrounding the damage should be abraded with coarse abrasive paper. Depending on the position and seriousness of the damage, use a patch of reinforcement wetted out with the minimum of epoxy resin to patch the hull
inside. Overlap the damage by 20 mm in all directions.
When cured, and if it is large enough, the crack in the gel coat should be filled with resin pigmented to the correct colour. When this has cured mask off the surrounding area and carefully rub down the new gel coat with 600, 800, 1000 and 1200 abrasive papers. Finally buff it with metal polish to restore the original finish.
For more serious damage where complete failure of the backing reinforcement has occurred
In these cases the material along the crack should be ground or filed out to allow the hull to return to its original shape at the earliest opportunity. This ensures the repair will not be so noticeable when it is made. The area inside the hull surrounding the damage should be abraded with coarse abrasive paper. Use self adhesive tape as necessary on the outside to hold the pieces of hull in their correct alignment.
Depending on the position and seriousness of the damage, use a patch of reinforcement wetted out with the minimum of epoxy resin to patch the hull inside. Overlap the damage by 20 mm in all directions. Avoid allowing resin to fill the crack. When cured, fill the crack in the gel coat with resin pigmented to the correct colour. When this has cured mask off the surrounding area and carefully rub down the new gel coat with 600, 800, 1000 and 1200 abrasive papers. Finally buff it with
metal polish to restore the original finish.
For blisters caused by osmosis
These should be pricked with a sharp point to allow the moisture to escape. Allow the moulding to dry thoroughly. If the blisters are on external surfaces and it is necessary to repair them, the loose gel coat should be broken out and thoroughly
cleaned with solvent before each hole is filled with a spot of pigmented gel coat. When this has cured it should be rubbed down and polished as described above. If the blisters are on internal surfaces and pose no cosmetic problem they can be sealed with a spot of cyano-acrylate glue.
Damage to a hull caused by excessive heat
This can usually be restored, at least partly, by gently heating the whole hull to a temperature exceeding the temperature at which the damage occurred. This allows the whole hull to soften and return to its original shape.
Conclusion
You need to be aware that there are a number of pitfalls into which you can fall and which will result in damage to your boat.
There is no guarantees concerning the long term quality of the surface finish of the hull moulding.
Parts of SAILSetc Document Miscellaneous information MI02a SAILSetc Boats Notes, December 2008 have been used in these Instructions by permission of SAILSetc and remain copyright of SAILSetc.
Prepared by Robert Grubisa
Rijeka, January 2009
For PDF file click HERE
