Hi Wolfaroo, I enjoy seeing your project
boat and wish you well in completing the project. My husband and I re-did a smaller boat (54' on deck) in a complete rebuild
2007-2009 timeframe. You can see some boat pics here
and some projects in our older blog posts here
We used a splined Alaskan Yellow Cedar structural overhead 3/4" thick and then two 3/4" layers of BS1088 atop the deck beams. Very stiff which is great for a sailboat.
Our oak deckbeams had enough rot
in them (from iron fasteners the white oak was ruined) that we decided to re-do all the deckbeams. This link has a lot of deck beam pics
The overhead going down here
The last look at the overhead before putting on subdeck here
The BS 1088 ply can be seen here
Ah, a better pic of the BS1088 ply here
We used an elastomeric roofing system (Metacrylic) to waterproof the deck and that could have been the final finish but we added canvas
for grippyness and traditional look. We could always epoxy
down a thin (teak decking systems type 3/8" teak) over the Metacrylic if we wanted that yachty look but it doesn't really appeal to us. The Metacrylic can be seen in that pic above showing the 1088 ply. Before painting, the canvas
stapled to the edges can be seen in this pic
1> How would you recommend I fix the ply subdeck to the oak deck beams? (screws + marine sealant)
Skip the word "marine"
We used something called PL Premium which is a construction adhesive. There are a couple different versions to this adhesive but it was the waterproof one that we used. I see with google
that the company is now owned by Locktite, so not sure if you can speak with their engineering staff (as I did) anymore.
We used bronze screws from the AYC overhead into the deck beams. We then used a Raptor nailgun with plastic Raptor nails (no corrosion) to nail the first layer of BS1088 to the AYC and of course, lots of PL Premium construction adhesive. Then the next layer of plywood
laid perpendicular to the first, plenty of PL Premium between the two and plastic nails holding it together.
On top of that, the waterproof and flexible elastomeric and on top of that the anti-skid of traditional painted canvas.
2> What fixings and/or adhesive/sealant would you recommend I use between deck & beams? (silicon bronze full body wood screws + sikaflex 291 or similar)
3> Should I treat the beam top surfaces prior and if so, with what? (metallic wood primer or red lead primer)
We use white lead paste stirred into a white primer or red lead primer on mating surfaces, yes. However, the deck beams were sanded of all primer so they could be adhered nicely to the AYC overhead.
4> Should I treat/paint the underside of the deck prior to laying and if so, with what? (metallic primer)
If painted, yes that is easiest but you have to not paint
the mating surfaces where the deck beams are if you're going to be using any adhesive. Othewise you're just gluing paint
5> What type of cloth? (2 x layers 300gsm woven roving)
I would not use epoxy in this application. As stated, we used a paint on elastomeric and it had a polyester scrim that goes down first. The end result is a sold sheet of rubber that won't crack (as resins can) or leak.
If you do go with a epoxy, choose one that is more flexible than WestSystem and try to use something like Dynel (polyester) rather than glass. This is not structrual for you, it is simply water proofing. Your structure is in the ply.
6> What adhesive should I use to secure the sacrificial deck atop the subdeck? (epoxy, although it’s also been recommended I use a more flexible sealant such as sikaflex)
As mentioned, we used PL Premium construction adhesive as the best product for gluing.
I think it's kind of hinky to do as you plan with the grooved wood deck--If I were you I'd just put down a straight laid (but thin essentially a veneer) wood deck of white oak, AYC, fir, or another material you can PAINT for a workboat deck. If you do a veneer type wood deck, you may be stuck using an epoxy adhesive with it and you may be stuck using fasteners that will penetrate your plywood
. That is largely why I wouldn't do it.
I typically don't like it when people veer away from traditional methods and materials for wood boats. Especially when using layers of resin/epoxy to prevent water ingress to hull
and/or deck. Think carefully about it. Traditional methods work well, are repairable, and maintainable.
Our deck, canvas painted completed looks like this
All just my opinions. Enjoy your project! If you should need (US based) materials please feel free to contact me via the Schooner Chandlery
or PM. We have a seller in the Chandlery
who has great pricing on the larger diameter silicon bronze screws and bolts for example and he will ship abroad just charging
. After we used the Metacrylic successfully on our boat for some years, we've contacted the company to distribute the product. We're not advertising it (yet) because they don't offer the smaller quantities that most boats would need and we're working with them on that as well as a few other matters. We just purchased a large quantity ourselves and then gave the left-overs to a fellow who was needing some roofing materials for his house and wanted to use Metacrylic.