So I have been reading the thread about foaming under the deck to stiffen it and got to thinking, could be bad
With a cored deck you want glass on top to protect it but the glass on the bottom is the glass under tension and is what makes the deck stiff. If this is correct then it seems to me the bottom glass is more important than the top glass. If this is wrong please explain to me what I have missed.
Since you asked, I think this is where you went wrong.
Fuzz wrote: ↑Tue Nov 14, 2017 4:19 pm... and got to thinking...
Everything else make sense.
My already completed 'Lil Bit'. A Martens Goosen V12 set up to sail me to the fishing holes.
Currently working on making a Helms 24 our coastal cruiser.
“Mark Twain/Samuel Clemens” wrote:Eat a live frog first thing in the morning and nothing worse will happen to you the rest of the day.
Jaysen wrote: ↑Mon Apr 29, 2019 3:44 pm
I tried to say something but God thought I was wrong and filled my mouth with saltwater. I kept my pie hole shut after that.
Until she wins the lotto I still have to do this thing called "go to work". Luckily for me that is mostly just sitting around looking at BBC forum for new opportunities to harass you.
My already completed 'Lil Bit'. A Martens Goosen V12 set up to sail me to the fishing holes.
Currently working on making a Helms 24 our coastal cruiser.
“Mark Twain/Samuel Clemens” wrote:Eat a live frog first thing in the morning and nothing worse will happen to you the rest of the day.
Jaysen wrote: ↑Mon Apr 29, 2019 3:44 pm
I tried to say something but God thought I was wrong and filled my mouth with saltwater. I kept my pie hole shut after that.
I don't think any cored deck is designed to be used under real tension, and needs to be properly supported to eliminate flex. The glass on top is required to protect it, the glass underneath is optional in a lot of builds. The best scenario is the deck is resting on foam meaning no flex at all, if so no bottom glass is really needed I would think. That being said, I always glass both sides as checkin seems to happen even with great plywood.
Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe, and an FS17.
As I understand it the glass on top of the deck (or any surface taking traffic or gear) is there to create a barrier for the wood. Ding the glass and you still don't have penetration into the wood - i.e. water in the wood. Underneath, no traffic, no gear, no dings, no need for glass. When people talk (including me) about the foam stiffening up the boat, it's the hull, not the deck. The bond that stuff makes between the stiringers and bulheads, and to the bottom is very strong and ties everything together.
The ply for the deck should be stiff enough in and of itself to not flex significantly, especially when glued to the stringers and bulkheads. In another thread here I advised against using 1/4" for the deck because of that.
Like I said...As I understand it...
The world always seems brighter when you've just made something that wasn't there before - Neil Gaiman
For stiffness when you walk on it, the bottom layer is the most important. That will work in tension.
Now, the decks are designed to be stiff enough without any glass on either side but many like to put a thing layer of glass on top for protection. It adds very little stiffness.
I don't have much choice; have to glass both sides of the foam or it'll get real saggy.
But you are pretty much correct. The better support would be from underneath; only plywood doesn't need that much xter. So, a top layer gives you abrasion protection. The other thing is if you want to avoid ingress; putting fiberglass on top also helps you create the bathtub effect.
The hardtop I am building is 5x8 out of 3/4 inch nidacore. With one layer of 1708 on one side it would bow a ton just from its own weight. Put a layer on the other side and it is a whole different story.
