Unveiling the esoteric secrets of epoxy resin works. /PART 5

in this part we will deal with big areas lamination works , this is going to be a quite long chapter !

In modern wood & epoxy constructions there is sometimes the need to laminate a whole big area with glass fabric , normally hull or deck/cockpit surfaces or both; the reasons for doing this go from serious structural reasons in strip planked construction , to chafe protection in radius planked and stitch and glue boats , or protection of the working areas like decks and cockpits; the working sequence is more or less the same in any case, although in the first one (strip planked boats) we will probably have to laminate more than one single layer of glass fabric, while chafe protection is normally achieved with a single glass layer (with local doublers in critical areas like chines or centerline)

  • Preparation preparation preparation !!! the better way to do a work like this in a small-medium boat is to make it in a single shot , and the better way to make it in a single shot is to have a bomb proof preparation: a properly sized and organized crew to do the work, and all the stuffs ready before starting the work.
  • Crew: for smaller works, kayak, small dinghies, a crew of two is fine ; working alone requires a good amount of skill handling the glass patches , a crew of two will make handling the glass patches much easier ; for bigger boats up to 28 feet a crew of three-four people is a good sized one , they are not required to be skilled laminators as long as the working sequence is clear to everybody and each one have his own task to do;
  • preparing the materials: that means mainly cutting the glass patches, take measures on board (or unroll the glass directly on the hull), cut patches on a table (or on board), roll them properly , place them temporary on the hull in their final position , mark each of them with a sequence number form transom to bow and two arrows, one pointing up and one to the bow ; you can also mark their position on the hull with a marker ; re-roll the patches , place them on a table following the lamination sequence , so that you will not frantically look for the “next patch” during the lamination work
  • overlapping the glass patches : this is required in each glass fibers work, to have a continuity in the glass layer mechanical properties, for small project and thin glass layers a 2-3 cmoverlap is fine, for bigger boats and thicker glass layers 6-7 cm is ok ; in case you have to laminate more layers, stagger the second layer so that the overlapping are quite far aprt and they will not make a an excessive step in the glass lamination
  • overlapping on the centerline: for the big projects, I prefer to split the patches on the centerline, making a 10 cm overlap on this area ; remember to mark the patches for port and starboard side (1P and 1ST, 2P and 2ST and so on may be a good marking system)
  • avoid supersized patches: they are a mess to handle and impossible to presoak , for decently sized boast my advice is to take advantege of the glass roll height , start form centerline (remember the overlap here) go down the hull topsides and cut

  • how much resin is required for the work ? This is a capital question because its answer will make you sure that you have the right amount of resin (and the right amount of proper hardener) for the task ; general thumb rule working with biaxial and wave roven is that you will use around one kg of resin for one kg of glass fabric , add some more because you will wet the hull face before applying the patches ; let us make an example: IDEA21 hull is about 23 square meters ; we want to laminate a light glass layer only for chafe resistance, a 300 g/square meter wave roven will be fine; this means we will use 23×300 g = about 7 kg of glass ; we will need 7 kg of resin plus another 20% for wetting all tha area , that is to say about 8.5-9 kg of resin ; we will check to have at least 10-11 kg of resin+hardener available for the whole process ; in tech literature you will find much more precise numbers for the so called Glass/fiber ratio , that will explain why that unidirectional fibers requires less resin than biaxial that requires less resin than wave roven , but for our purposes a 1:1 ratio is enough to organize the process
  • Chopped strand mat : or the so called “mat”, is a kind of “non fabric” made by few inches log glass fibers pressed together ; this stuff is the base material for most of cheap fiberglass works, it soaks a huge amount of resin and has poor mechanical properties , it is required to form intermediate layers among multiaxial fabrics when laminating with polyester or vinylester resin; it is totally useless for our purposes, forget it.
  • what glass fabric will we use ? First , in case the lamination has a structural meaning follow strictly the plans , contact the designer in case you think that the plan solution is not feasible or optimal (it may happens) ; in case we need only a chafe protection layer we may have more freedom to choose:
    • wave roven or biaxial ?: this a field in which previous experiences and personal tastes play a big role ; I would go for a light (200g/square meters or less, down to 90 g/m2 for light kayaks) wave roven glass for small boats, dinghies and kayaks for chafe protection , its only drawback is that it is quite delicate to handle ; it is easy to soak with resin, gives a really good finish surface, it adapt easily even to complex curves and tight corners; my preference goes for biaxial for structural works on bigger projects, but it has one big drawback that has to be managed to do a good lamination: resin tend to flow away form vertical faces much more easily then when we use wave roven fabric; what we can do to manage this problem is:
      • work with slightly thickened resin
      • presoak the fabric on a table (see chapter 4), which is always recommended with biaxial
      • work the resin taking it form the bottom to the top with spatulas, rollers and bubble breaker until it start to gel

  • and now let us finally talk about the working sequence (I normally do this work with hull upside down su here “up” is the centerline and “down” is the sheerline):
    • several hours before: put the required resin and hardener for the whole operation in the hot/cold storage to take/keep them at the right temperature , see chapter one
    • mix the resin you will use for the next two patches or so
    • wet the hull surface for the first patch
    • pre-soak the first patch on the big cardboard you prepared (and wetted with resin), you can avoid this with light wave roven
    • roll the soaked glass patch , place it on board , start from the top
    • unroll the patch on the hull, check position marked previously on board
    • push the glass fabric on the hull using spatulas, if there is any area where resin is missing add resin and soak the fabric with paintbrush or small roller
    • keep on working the patch on the whole surface with spatulas, remove the excess of making it flow down to the floor (cardboard, cardboard everywhere !!!)
    • wet the area for the next patch with resin
    • note on the patch sequence: I prefer to work starting form the bow or from the transom, which is easier for your logistic, and going from one patch to the symmetric one, that is to say for example, first patch bow starboard, second patch bow port, and so on .
    • Repeat the sequence : soak the new patch with resin on the table, roll it, unroll it on board starting form the top, pay attention to have a correct overlap with the previous one , work the patch
    • Do not cut he patches too “tight”: leave a 12-15 cm length in excess on the lower edge (sheerline) , you will cut it during the lamination process before the resin set
    • pay attention to lower edge, fabric tend to detach form the surface, forming wrinkles and bubbles
    • curved areas: in the bow you may find hard to drape the fabric in the final section, in case make small cuts on the glass edges to release the tension
    • “nose” area: I normally prefer to laminate it with one patch covering the bow and 20-30 cm on each side of the hull ; avoid overlapping on the very bow
    • cutting the glass fabric protruding out of the sheerline at the end of operation before the resin set is a good idea, it helps to have a clean lamination edge
    • covering lamination with peelply, put a layer of peel ply on rthe glass once you have ended the lamination works, the amount of resin normally on the lamination surface is enough to soak the peelply properly, in case add a little bit of resin, do not worry abot overlapping or suing small patches or clippings ,it’s fine ;using peelpy is recommended for several reasons:
      • it will give you a perfect surface for the final fairing operations that it will take place after the glass lamination , no need to sand all the surface or wash it to take away the ammines (they are responsible of the soapy sensation of epoxy laminated faces)
      • you can leave it in position and peel it away when you decide to fair the hull
      • it slightly helps to keep the lamination a little bit more compact
    • in case you have to do the work in more than one session: avoid to wet with resin the areas where you are not going to laminate, cover every laminated area with peelply with , when you you will restart the operation simply remove a strip of peelply 50 cm wide and to start the work of the second session.

a small gallery of pictures from my archive , you can see: the effect of wet resin o a sanded hull face, the single glass patch required to glass the kayak’s hulls, working on a hull, and several pictures of glassed hull