TomW wrote: ↑
Mon Aug 31, 2020 9:57 pm
Don't get too wrapped up in all these complex descriptions. For a 130 cm foam core board there are some simple principles.
Aways use same laminate top and bottom. Symmetrical.
With high foam density around 60-80 kg / m3 you can get away with thinner laminates.
With thicker blank , over 35mm , thinner laminates.
The lower density foam requires thicker laminates to resist heel dents.
If you post what density foam and thickness you are thinking, I can recommend a laminate schedule.
heel dents are an issue in hydrofoiling boards.
Deck laminates are super important because of both heel dents and the fact that you have body weight plus power of kite through the top laminates.
Bottom laminates resist crushing/ compression forces at mast plate and slams upon grounding.
600g cf on 80 kg foam is overkill, but ok, board will last 50 years.
Thanks for the advice. I am thinking of the following:
- 20 kg/m3 EPS 4 cm thick, this is what I have here already and what sparked the idea for the project,
- 80 kg/m3 1 cm high density foam in standing area (replaces 1 cm of EPS so total thickness still 4 cm). Strap inserts and foil track box are also in HD foam,
- Lamination symmetric, for sure
- Bottom to top: 20 cm uni carbon stringer 200 g/m2, 240 g/m2 carbon/kevlar twill reinforcement above foil box, 240 g/m2 carbon/kevlar twill full board, 200 g/m2 glass full board. Rails wrapped double.
-> I chose the carbon/kevlar twill because I liked how it looks and for the impact resistance of the kevlar.
-> Glass on top so that I won't have to sand any carbon (unhealthy) or kevlar (difficult because of fraying). I do understand that from a structural viewpoint the glass on the inside would be better.
-> Shaping blank with hot cutter. Want to shape the rocker in the foam.
-> Vacuum inside a clothing storage bag.
-> Wanted to do the deck first with peel ply to get a rougher finish for bonding next layer on rails and deck pad.
-> Then bottom with perforated release film to get a smooth finish.
? Is there a particular reason the bottom is usually laminated first? On surfboards it makes sense since the deck is doubled but not the bottom, but with symmetrical lamination I don't see why I shouldn't do the deck first?
? Also wondering if a hot coat is normally necessary after vacuum bagging. I would guess not, but experience here is appreciated.
? Recommendations on the rocker for a 125-130 cm board are also appreciated. Was thinking of something like 8 cm, but I've seen and read that even more is better?