Soggy Floor - help needed

[aldo]

The core of my hatches were done the same way so I'm guessing that was the manufacturing procedure back then. Not sure why-maybe all the direction changes helped strengthen the fiberglass?
This is a little bigger than doing the hatches though. I did them with mahogany squares set in West System & filler. So far so good on those.
I have some time to figure this out while do some mindless cutting and scraping. I'll post progress. Appreciate any input from guys who have been there-done that.

[Caymanboy]

The reason they used the plywood squares was A) Thats what they had at the time. B) Cost. C) Intalling small squares was easier. If you used Divinicell or some other core material it will be lighter and stronger and will not rot, you will have to intall the bracing for stength, although they might not need to be as many or as large. it would also pay to use a vinylester or epoxy resin. IMHO of course!

[deepsushi]

Fred,

I did not put the ribs back in. I did get a little bounce / deflection without them so I am going to pull the hatch back out this spring and glass in some stiffeners. I think I am going to use some 1 1/4 " pvc pipe ripped in half as the stiffener "base" and glass over it with some 1708.

I considered using one of the composite products as a core. However, the composites are a lot more expensive than plywood. Th original plywood lasted 30 years and it only failed due to the exposed plywood edges that allowed water to penetrate into the core.

Cutting the plywood into squares accomplishes two things:

1.) it eliminates any warpage in a full sheet of plywood.
2.) it is a much more efficient use of material. I recored the whole hatch with 2/3 of a sheet of plywood. If I utilized larger pieces I would of needed at least two sheets of plywood using large "whole" pieces.
3.) the theory of the alternating grain orientation is that it will prevent water intrusion between individual core pieces ( I am skeptical of this as every square was fully water saturated in the hatches I have done in both my 18 footer and the 23 footer.)

[strick]

The reason that all the squares got wet was because the factory just butted the ends of the squares next to each other...rather then leaving a gap and filling that gap with cabosil. The picture above is a very common sight on this board Leave a space and fill the gap and that wont happen. Also it will be stronger.



As far as composites go...they are supposed to be waterproof and we know at least temporarily they are but I've seen water trapped in foam over time... they are expensive and you cant just go down to Home Depot and pick up a sheet for 30 bucks. Another thing to think about is that this is new technology that has not stood the test of time...whos to say that boats with composite coreing will not crumble apart in 30 years? at least we know what plywood is capable of. That said I do like composits for some things and I have several sheets of corecell sitting in my shop waiting for something special to attach themselves to.

strick

[hermco]

Manufacturing with composites has been going on at least since the 1980s. If my memory serves me right every Contender and Intrepid built was a composite boat. I know for a fact the Contenders were.

[dmese]

I just went back and review pics of my inboard project and here's what I remember. When recoring I asked about the squares as well and did not go that route. I used Peske board (which is good IMO) and did not cut it into squares. What happened was I would get small air voids no matter how hard I tried to evenly squeeze the pieces together. Then I cut a grid pattern 3/4 the way through the material to make it shape better. If I were to do it again I would consider the grid or squares. With the squares you are more likely to get the air out and form better to the shape of your skin (like tiling). Mine had mahoganney~ strips laying over the fuel tanks for struts. It did not go back together this way! P.S. Check your tanks.

[Caymanboy]

What Strick says in entirely correct. The coring probably will absorb moisture over time. No matter what you use it should be properly sealed. I look at it in a different sense, weight to strenght ratio. That same hatch in wood or coring is probably a 30-50 difference, do that around the boat and it adds up. All comes down to how much you want to spend and how light you want it, Truth be told, if done properly, either way will outlast how long you or someone else will own the boat.

[hermco]

What happened was I would get small air voids no matter how hard I tried to evenly squeeze the pieces together. Then I cut a grid pattern 3/4 the way through the material to make it shape better. If I were to do it again I would consider the grid or squares. With the squares you are more likely to get the air out and form better to the shape of your skin (like tiling).

Exactly why the core is cut into squares! One of my first jobs at Sea Vee Boats back in early 80s was to reduce 4x8 sheets of 3/4" ply to 5" squares on the table saw.

[Islandtrader]

Here is a picture of Penske type board scrimed an scored ready to be put down.

I used this on my front deck.







The squares are smaller for more contour. But I think you get the idea.

[aldo]

Plenty to digest while I cut and grind. Also got some input from my local boat builder. He suggested using pvc pipe, cut in half and glassed in place for the ribs.