3rd layer of epoxy over glass cloth
It took approximately 3 hours to coat the first layer of UV “resistant” epoxy resin above the glass cloth. The resin: SR 5550 – SD 5504.
Fiberglass reinforcements
Before the high coating I reinforced the hull with 194 g/m2 2/2 fiberglass cloth. It was not necessary according to the plan – I just wanted to achieve more strength and thickness. Be sure that enough resin covers the fiber glass. I used the next method: first I covered the hull with low density epoxy resin before spreading the glass cloth. Just right after this, I covered the glass cloth onto the resin-wet surface without a pucker. After covering the glass, I lubricated the top of the glass coat with resin using a painting roll and plastic spatula. Very important to avoid the air bubbles under the glass. It needs pretty much force, but be careful not to make the coat ropy.
Reinforcement mast step area and backbone
Before 3rd coating of epoxy I apply a special glass tape reinforcement from bow to aft over the backbone, outside of the hull. I use 100 mm wide glass tape in one layer, because I’ll coat the whole hull with glass cloth. Dudley Dix suggested 450 g/m2 biaxial glass cloth for the mast step area, but it could be purchased only in 100 m length roll for outrageous price. However I could buy carbon cloth in the quantity I really need. The resin I use (SR 5550 by Sicomin) is perfectly suited for both the glass clothes and the carbon clothes also.
Also reinforced the bow
Second epoxy coat on hull
More layers give you more strength and a better surface. Later I am going to laminate glass clothes as well – it will need more epoxy layers – all together with the inner layers the thickness reaches 12 mm.
Sanding first epoxy coat
Now, I can realize that actually sanding is the hardest job during the whole construction. Must be admitted that the more time you spend sanding the hull perfectly the better result you are going to get. You can get as good quality a surface as the GRP hulls.
First epoxy coat
First coating with low viscosity epoxy resin
Fairing hull before first epoxy coating
After filling all holes with epoxy you can realize that the surface is actually much more worse than you first thought it would be. The hull surface is full with spots – holes and humps. They must be filled up, and another sanding have to be done.
You can use softer filler mixed into epoxy for easier sanding, however, I have chosen hard ones because the mechanical properties fit better for the hull even if they are below more epoxy layers.
Sugar scoop structure
Rudder will be profiled below the hull. The top of the rudder will be made of 25X4 mm stainless steel A316 tube.
Hull works before finishing with epoxy
Before turning the hull upside down all painting jobs have to be done. At least 4-to 5 layers of epoxy covers are needed before the final polyurethane painting can be sprayed on. The last layers – directly under the outer painted layer – must be UV resistant or at least have some UV stable ingredients if available.
Before starting the final epoxy layers (gluing & sanding & gluing & sanding) all rough faults must be repaired.
Backbone stich will be cut before epoxy fillets.
Sheer clamp capping
After planning the hull skin plywood sheet to reach the shorter base of the trapeze cross sectioned sheer clamp the capping has to be jointed between the deck and the hull skin must be prepared. It is made by 12 mm plywood.
Radius skin fitting 2nd layer
After four months of rest it is time to continue the construction of the Didi26. The second layer is missing, so do the bow cap. Well, I started working with fitting the bow cap and continue the hull work setting the radius skin. Before setting the second curved layer of plywood to install the second diagonal layer of the radius skin area the skin must be sanded. The point is not to sand the surface of the plywood itself, but to the glued junctions and the filled-in holes screwed. Sanding the solid epoxy resin is very hard work, you need to be very careful during sanding not to scarf the surface of the plywood with a hard sander directly next to the mound of epoxy glue. If you are not careful enough you can easily make deep holes into the plan surface of the skin. It must be avoid.
Bow cap was installed by mahogany. It is screwed and glued onto the edge of the bow as a cap. Sides of cap are planned the same even as the flat area of the hull from the upper tangent to the sheer clamp.
If you want to avoid the breach or slit of the thin plywood layer when you bend it, you may apply some tricks: use much more longer plywood piece of band than you have to as longer grains have higher bent resistance.
