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Random Quote: There are no dumb questions on this board, but there does seem to be a lot of inquisitive idiots.
As my project progresses, I am faced with the challenge of which material to use in fabricating my new deck. I like the idea of having a deck that would be free of any future water intrusion problems by using Divinicell. However, the lower cost of marine ply (or even exterior grade) makes good economic sense. My concern is that I only plan on doing this ONCE, therefore I want to do it right. My queston is, if any of you forum members out there were going to redo your deck, which route would you take? Thanks in advance!
Ringleader is replacing the wood in his deck with Kledgecell or Divenacell, then again maybe he said Nidacore. His boat has wood in the deck from the fuel tank back. The rest is a PVC foam core. We can't figure that one out.
In mine I'm going to replace it with the 3/4 marine ply. That's what was there. In both cases it's from the back side of the fuel tank to the transom.
I think Daytona Plastic's has panels already with the laminate schudle you desire. If not you can get the Kledgecell or Divecell from Fiberglass Coatings Inc. www.fgci.com and do the layup yourself.
Both of our's will be done with epoxy resign.
To give you an idea on the laminate layup. I saw some test panels that were done by Dawson Boats here in P'cola. They were done with 3/4 Nidacore.One layer of 1808 and one layer od 1 1/2oz matt each side and vacuum bagged. The panels were then sent to a local test lab. When Robert at Dawson got them back they gave him a bunch of numbers, bla-bla-bla. He said put it in laymans terms. Can 30 people stand on this stuff with the panel being made X By Y deminsion? He was building large hardtops for 35ft's. They said you can put 300 people on it.
If you plan on mounting a console, chairs/leaning post, and possibly a t-top to the floor with screws - I would go with Marine Plywood. Just remember to laminate both sides!
Don't cheap out and use exterior grade plywood. Marine Plywood has no voids and is a better core material.
3/4" AB Marine plywood is usually 9-ply. 3/4" CDX plywood varies from 5-7 ply, depending on the mill. I would definitely use the Marine Plywood as it will be a straighter, flatter product to start with over exterior grade sheeting plywood. 3/4 CDX costs about 17 bucks, AB Marine runs around 45 bucks, but is worth it.
I like the NIDA core. Trayder is using it on his Sea Craft project. He said the stuf is so light that it scares you, but at the same time he said it is strong as hell.
I am looking at the 1/2" NIDA from FGCI. It comes in 4x7 sheets without any glass on it yet. (Trayder bought his with a layer of 18oz RW already on both sides) The stuff I'm getting will cost about $50 per sheet (not much different than Marine plywood!) and a sheet will weight 5.7 lbs without the glass laminates. Thats probably 1/6 of the weight of a 1/2" piece of marine ply of the same size!
The weight is my biggest concern. Since I'm going with a full transom/bracket, I'm trying to remove as much weight from the ass end of the hull as possible.
Now if the rain will only stop. Its my first day off in a month. I went out to the boat to get started again and it immediately began to rain! What a pisser!
this is a very interesting issue!....while it
looks like good marine ply (NOT exterior) will
give good service,indeed, if encased in epoxy,
the attractiveness of klege or divinyl or other
synthetic core materials is strong for me....
if i was building from scratch, would i use
any ply????....i havent worked with any core
but ply, so what strength, construction, or
deterioration problems could occur with these...
if I have to redo MY deck ever, given the care
i have taken with bedding, i will have given up
on wood. dan
We just redid the deck on the seacraft. We used Corecell in some parts and coosa in others. Coosa is the new kid on the block - it is a closed cell foam with fiberglass cloth already molded into it. You can't screw things into regular foam coring, and you really can't thru bolt through it either because it will compress when the bolts are tightened. With Coosa you can do all this.
The difference in stiffness of the coosa sections vs the corecell sections is unbelievable. I am getting ready to redo a 1965 Formula 233 and the whole thing will be Coosa, and stiff as a mother f'er. No ply or corecell for me
go to this website to get their contact info: COOSA
Most of this info is good but, Nidacore does not have the shear properties of Divinycell and weighs more. Coosa has the stiffness properties and compressive strength but weighs as much as plywood. Plywood will eventually get water in it and rot. For a very strong and lightweight laminate use H-80 or H-100 divinycell. For areas you need screw retention add some Trevira or the Coosa board. With a 1 1/2 oz mat and covered with a 2415 +/- 45 fabric, you will have a great laminate that will last forever.
Marine plywood is pretty foolproof core material and will last longer than you will ever care about -- as long as you do the lamination well, and use care when mounting hardware. All of the synthetic core materials have their uses, but there are so many variables to consider, I'd be inclined to stay with plywood for lamination done by anyone other than a skilled professional. If you insist on synthetics you need to consider loads, panel lengths, and balance core thicknesses and density with fiberglass skin thicknesses to prevent poor laminate design -- from cost and durability standpoint. Plywood has similar physical properties to traditional fiberglass laminates and, consequently, is much easier for most to figure out to make plywood cored laminates strong and stiff enough.
If you'r only going to do this once and believe in doing things right, why even consider marine ply or mention "exterior grade"...
reasons for Divinycell; 1) weight 2) easier to work with 3) strenght 4) no rot
If cost is an issue, then use plywood and polyester, just budget doing it three times in 10 years, - that equals the cost of doing it right the first time.
Plan the locations of leaning post, console, t-top, etc, and glass in backing plates or tapped 1/4" aluminum plates. Use quality epoxy, and don't skimp on the fairing compound when you've got it all buttoned up. Get the panels already layed up with 1808 or such and then lay down a final laminate of 18 oz biax and some lighter finish cloth. If you can work it out sizewise, cut all your pieces, and "glue" them together in the boat, then take the whole floor as an intregral unit out, laminate both sides on a flat surface before dropping it back in.
Great responses with much needed information, thanks! My layout consists of a console, leaning post and t-top (baitwell is already in the transom cap). Only the console will be glassed to the deck, therefore density will be needed for the leaning post and top. Will I be able to cut out the sections where these are going to be through bolted after the deck installation (replacing divinylcell with coosa or similar) when these pieces are ready to go in, or is proper planning needed before I glass in the deck. The deck will be glassed all the way to the hull sides, so access will be limited to only two small (fuel sender and bildge) access hatches, and an opening for the rigging tube. Am I on the right track here or am I going to end up tearing it out because I "jumped the gun" on the deck installation?
Seabird, you are well ahead of the game in the planning. Glass the console to the floor fromt the inside. When you pull up the old floor, and after verifying that your stringers are good, then plan where you want the base for the leaning post, and glass in a piece of 3/4" marine ply to the stringers, then glue the floor to that as well as the stringers. The force from the leaning post will be transmitted directly to the wood and the stringers. The compression characteristics of the divynicell will be OK and you can simply use self-tappers bedded in epoxy. For the t-top, why not use a design that attaches to the console. With it being glassed to the floor all the way around, it WON'T come up. If not, then do the same for the t-top bases as for the leaning post. I did one that way and after two years, and VERY VERY hard running I have never had an issue. My t-top is mounted on the console, and there is all sorts of stuff on the t-top. Leaning Post has never moved, its in there with #12 self-tappers.
Just a word of caution. The use of synthetic cores should not cause you to forget about the need for good construction methods for the prevention of water intrusion. Some cores will certainly absorb water. Just because you don't use wood doesn't mean your cored deck can't delaminate.
Synthetic Cores seem like too much work. Other than the weight difference . . . Can anyone point to stats where foam cores outlast properly sealed Marine Ply?
Please don't refer to the late 80's Grady White boats.
Why not consider treated ply like XL Greenwood. Dense, haven't found any voids in it yet and it doesn't rot. Marine ply seems overrated, uses the same glue as exterior. Using ply cuts down your lamination schedule a lot, if it's thick enough for stiffness all it needs is a layer of glass on top for appearance.
Another reason I would prefer synthetic over marine ply is the weight. I could probably loose a good 150-175lbs (same as fishing by yourself when you actually have two people) in going with divinylcell. I still have a week or so before I end up ordering my material. More than likely, I will end up ordering around 6-8 sheets (4x8) of divinylcell for my project. I will make sure I post some progress pics so you guys can tell me if I am doing anything out of the ordinary. Thanks again for your input!
Divinicell vs. Marine Ply 
