I’m in the process of building a HWS and am after a bit of advice on deck strength.
I have managed to source 4mm thick panels of Californian redwood (sequoia) and am at the point in the build where the frame is done, bottom section is laminated onto the frame and I’m about to join and laminate the deck.
Im after advice in the best way to ensure deck strength (without getting too heavy handed as I’m not wanting to add excessive weight). From my testing of the strength of the 4mm timber, I’m fine with it for the bottom but feel it will need a little more strength in the deck. The frame does have strips running parallel to the stringer of the frame for strength already.
Without pics or any measurements on the frame & spacing it’s a pig in a poke to me. I suggest you glass both sides of the deck, top & bottom. Other than that I dont have enough information to comment.
Everywhere your feet will be on the deck, add at least 1 layer of 4oz cloth on the inside panel, and consider reinforcing those areas with wood too.
Strip the wax off a similar dimension board youride and notice where the worst footwells are.
The glass on interior panels if two layers can be in an X pattern. the wood will try to split along the grain on impact and interior glass makes this much much less likely to occur.
I’ve used 5 mm plywood for both decks with only using 4 oz cloth on the outside and poly resin. I think 4 mm will be fine if your joints are good and tight. Your rib spacing looks to be about 6 inches which should help support a thin deck. All of my 5mm decks were 8 inch ribs. If you are worried about the deck, test fit it with clamps or temporary glue. Then carefully apply weight, step on it, and see if/where you need to reinforce.
Take the advice of people here, most of the people here know from experience. Glassing inside and out can seem tedious, but it helps with strength and watertight integrity. If you don’t want to do that use more cloth on the outside to add more deck strength.
I also wouldn’t be too concerned with weight. It is a wooden board not a high performance short board. Any extra weight is usually only felt between the car and the beach.
Go with Hucks advice! Take your deck, flip it around, apply a very thin coat of resin onto the future decks inside with a roller. This helps sucking excessive amounts of resin in the next step.
Laminate a layer of glass onto the entire inside. Depending on your resin, mix a batch of resin and some thickening stuff like thyxo… or microballons and apply onto all ribs and stringers of the frame. The timing is important, you want the resin of the deckpanel to be tacky or harder, but still flexible enough to be able to follows the decks contour when you press the deck onto your frame, where the glass and resin touch the thickened epoxy.
When you lateron finish the decks outside apply a cheater coat too and glass it. If your ribs distance is about 6 inches or 15 cm, the deck should finally be solid as a rock. I do exactly this with 5mm balsa and never had an issue…
I single layer 4oz. inside the deck… The spacing can be widened to 12" apart… Between the ribs, on the underside of the deck, I add wood and/or glass/carbon deck stiffeners in the areas where I stand…
I use a different build method with HWS with multiple stringers and rails cut out of a 1x12 and tapered and stacked, but my deck and hull panels are glassed on the interior, before being attached to the structure.
Both hull and deck panels are trying to reduce nose rocker when clamped into place. This can flatten the nose rocker and induce unwanted concaves in the nose and middle of the board, which cannot be shaped out.
When glassing my deck and hull panels, I would somewhat mimic the nose rocker and deck doming, so less clamping forces were required to later attach it to the frame. The deck panel once cured would rest on my flat table with teh nose lifted two inches, and I built a jig to hold it like that while I completed the frame structure, which was something like 15 months in the making
I was not doing the attachment in one stage, and would be relying on epoxy’s mechanical tooth for the bond. I never use wood glue.
My latest HWS has a lot of fiberglass inside and added structure where my Knee pounds the deck on every pop up, but the WRcedar started getting crushed with ~5oz of cloth on the deck in that spot, and I added a bunch more, and IF i were to build another HWS, that specific area would likely be a harder wood like Mahogany.
But I love how my latest HWS rides, and it is built to last, so it is unlikely I will build another.
