Before laminating the hull it is necessary to round off the corners because the fiberglass fabric cannot bend around sharp edges. I also sanded the plywood to make it clean and smooth prior lamination.
Choosing a transducer modell for the echo sounder gave me some headaches. The ClassGlobe 5.80 class rules allowing a simple depth gauge. A log / speedometer or other multi-sensors are not permitted. I decided to assemble an Airmar P79 in hull transducer. It can`t be placed on the wooden hull structure and must be cast in a layer of epoxy directly to the glasfiber hull construction. So I had to drill the hole for this transducer before laminating the hull. To do this, I drilled a 10cm hole with the circle cutter in the floor plank directly in front of frame D. I closed this hole again with 20mm thick foam and secured it from below with a plate and a support.
Installation scheme for the Airmar P79 in hull transducer.
Transducer hole with foam block from the inside of the hull.
Support of the foam block while laminating the hull.
I have done the lamination in 2 steps:
- Laminating the edges and plank connections
- Hull lamination
Step 1: Laminating the edges and plank connections
I laminated the edges with 600g/m² roving glasfiber according to the plan. I covered the area of the bottom plank, the stem and transom with 2 layers of 600g/m² (first layer 10cm and on top of that a second layer 15cm width).
I covered the plank connections with 15cm 600g/m² roving glasfibermat. I also attached 2x 600g/m² roving fabric in the area of the dagger board holders. Finally I applied peel ply for surface conditioning.
After some days of curing, I sanded and filled the transitions to avoid possibly air bubbles when laminating the glassfiber fabric.
Step 2: Hull lamination
According to the building regulations, the hull must be covered with 1000g/m² fiberglass fabric. Due to the easier handling, I decided to make the fiberglass structure in 3 layers and used woven glassfiber fabric 345g/m² and 1 meter width. I laminated wet-on-wet in one pass with overlappings of 5-10 cm. After applying the first layer I added reinforcements with 600g/m² roving fabric in the area of the skeg, the keel plate and a band round the hull to strenghen the hull in the position of the shroud chainplates. I used epoxy from the brand R&G which I knew from my previous boat building so far. Namely it was the resin L and the slow-setting hardener GL 2. This epoxy resin is thin flowing and slowly curing. It soaks the fiberglass fabric very well.
I built a rolling scaffolding that was moveable along the hull from the transom to the bow. I pre cut the fiberglass mats a day before. The order of applying the fiberglass fabric was starting at the transom as follows:
- layer fiberglas fabric.
2. layer fiberglas fabric
3. layer fiberglas fabric
4. layer fiberglas fabric
5- layer fiberglas fabric
5. layer fiberglas fabric overlapping the transom
6. layer fiberglas fabric
7. layer fiberglas fabric
8. layer covering the transom with peel ply
9. layer fiberglas fabric
10. layer fiberglas fabric
11. layer fiberglas fabric
12. layer fiberglas fabric
After applying these 12 coats, I planned to take a break to eat and drink. Then i was able to proceed with this 3-layer system to the bow.
The advantage with this method is that I can stop the laminating process at any time and simply cover the laminate with peel ply and continue the next day or after a few days. For example, if you are a small team and you have to take a break or there are problems with the resin etc. you`re able to stop and continue later.
Time for the big day.
Christian (CG #103) and Thomas, a friend of mine from sailing club, came on a saturday to my workshop. We worked great as a team. I mixed the epoxy, added the pre cut fiberglass mats from above, applied the epoxy and vented while lying on the scaffolding.
Christian laminated the starboard side while Thomas took care for the port side. I mixed each 1 kg of resin and 300 grams of hardener in a 3 liter bucket. I took control portion of each mixture. This way i was able to check the curing later.
In total we used 26 kg of epoxy resin. Laminating 4 layers (3x fiberglass + 1 layer of peel ply) takes time. Time was flying so fast. With a short break, the three of us took 12 hours and bravely held out until early morning. Very good job guys. The result is excellent.
General tips for laminating:
A few days before the laminating day it is time to check and control the material. Then there is still enough time to order missing things. Calculate is there enough resin / hardener? Are there enough tools (brushes, rollers, mixing sticks and containers, venting rollers, a second scale to be on the safe side if the usual scale is defective, protective material such as gloves, suits, respiratory protection, etc.).
Maybe it gives you confidence when you mix the epoxy and check if it is curing and that all materials are compatible. There’s nothing worse than finding out that the resin doesn’t work!
I laminated the raw Okoume plywood planks. They was not prepainted with some epoxy layers. Keep in mind that the wood could pull out the epoxy of the fiberglass fabric. You have to apply a liquid epoxy layer to the wood about half an hour before. Immediately before placing the fiberglass mats, apply another good layer of epoxy. Always make sure that each layer of glassfiber fabric is well soaked with resin before applying the next layer. If the fiberglas becomes translucent then you can be sure that is well soaked with epoxy resin.
When putting on the peel ply, don’t apply too much epoxy resin. Otherwise waves could form. It’s not a big problem to sand them down later, but it’s better to avoid this.
After the lamination is done and the peel ply is on it is best to continue working with the ventilation rollers for about half an hour and press the fiberglass fabric down to the surface while it becomes more and more sticky.
I personally got some tips from Joachim (CG# 165) who also wrote a very good blog about laminating the hull. Thank you Joachim!
Some more impressions from laminating the hull ClassGlobe #66:
Trolley with fiberglass and peel ply rolls.
Epoxy mixing bar.
My co-wokers Christian and Thomas.
Thank you so much guys for your great effort and the unforgettable moments when laminating hull ClassGlobe #66.