The first layer of your laminate should be a light chopped strand mat, either 1 or ½ oz per square foot [300 or 450 g/sq.m].   These are easy weights to work with and will provide a good key between the core material and the bulk of the laminate that follows.   This first layer is very important as the bond between it and the core material must be as perfect as possible.   If in doubt, make up some sample pieces using scrap core material as a base.   For the bulk of your hull laminate, you should use only unwaxed general purpose laminating resin.   The final layer of the outer laminate should also be a chopped strand mat and the resin should be waxed to facilitate the sanding that will come next.  

WHICH DIRECTION?

There are at least five directions you may use to apply the various layers of the glass laminate.   The first layer of mat should be laid in the most convenient direction.   You need only butt the joins in the mat.   Most fibreglass mats have a slightly braided edge that will blend and make a clean join, if carefully rolled, and this join will not be visible after the resin has cured.

   You should apply a layer of the resin to the core before laying the mat. The first layer of CSM must be carefully wet out and rolled to remove any bubbles.    Do not over saturate the mat, but roll out the excess resin, with a steel roller.   If you work from the top then the resin will flow down through the laminate.

TWO LAYERS AT ONCE

It is good practice when laminating a hull to apply a layer of the mat and a layer of roving simultaneously – mat always first.   The method is to lay up the mat and use the roving to help soak up the excess resin, which the mat often holds.   The roving and mat are rolled out at the same time.   If you become proficient, you will find this method of installing your laminate offers the smoothest finish and the best resin/glass ratio.  The object of the exercise, when laminating, is to have the correct resin to glass ratio. The strength is in the glass so you do not want a resin rich laminate nor do you want your laminate to become resin starved - you will soon recognise a good laminate.

LAMINATING WITH A TEAM

Another method of applying your laminate is to have a team of helpers, so the laminating can be completed without any interruptions, over a few days.   You should have enough help to apply at least one full layer (mat and roving) over the hull per day.   Do not apply more than two layers per day as the curing process will generate too much exothermic heat and may distort and damage your laminate.   Using this method, you will apply one layer all over the hull before starting the second layer.   Some of your team may be installing the second layer a few hours behind you, while the others are still completing the first layer.   Four people are the maximum who can be gainfully employed on one hull, one mixing the resin and pre-cutting the lengths of fibreglass fabric and three applying the laminate. Within reason, the faster you build up the laminate, the better the bond will be between each succeeding layer. Technical data can be obtained from your materials supplier and, in most cases, they will be happy to visit during lamination to see that everything is being done in a proper manner. 

NOTES ON LAMINATING – ALL METHODS

For ease of handling, try to obtain mat and other fibreglass materials that are about 30” [760mm] wide.   When laminating, always overlap the joints of the preceding layer and if you are using a unidirectional roving, change the direction for each layer.   Never allow the edges of one layer to lay over the edges of the previous layer. Not only will this weaken the laminate, it will also cause a high spot.

Wherever possible, always tear edges of the mat to blend in to the surrounding laminate and always start and finish with a mat layer - never laminate roving to roving without a mat between.   It is a good idea to trim the sheer as each layer of laminate cures.   It is easy to trim around the sheer and anywhere else where trimming is required, when the laminate has just cured and before it reaches its final hardened state.   A sharp trimming knife will do the job nicely.   If you let the laminate set really hard before trimming the sheer, you will need to use a jig saw or diamond saw to cut off the excess laminate.  

   When you have completed the design laminate for hull or deck, do not be tempted to add extra layers to “make it stronger”.  If you have any queries about the laminate, please consult your designer.   Do not, under any circumstances, just add a little more because you believe you will improve the strength of you hull, you are adding unnecessary weight and wasting money.  

   The extra laminations needed for the keel and other areas below the waterline can be added once the full hull laminate is complete.  If you have used an isothalic resin, for increased resistance to water permeation, it is advisable to coat all areas below the waterline with several layers of vinyl ester resin and fiberglass tissue.