How thick? Glass?

[epresutti]

Folks,<br /><br />Does anyone know how thick a piece of glass (epoxy resin) needs to be to equal the strength of a 3/4 in. piece of plywood?<br /><br />Thanks in advance.<br /><br />Safe boating to all.<br /><br />Cheers.<br /><br />emp.

 

[Capt. Bob]

Re: How thick? Glass?

It would be helpful if you stated the use of whatever you are trying to fabricate. I don't think you can compare the two materials based on "equal strength" alone. I'm no engineer but I know frp is brittle and plywood isn't.

 

[epresutti]

Re: How thick? Glass?

Capt Bob,<br /><br />I am building a platform that is in the shape of a trapazoid that will be 48" wide at the front, 60" wide at the back and 30" in deep. I intend on creating "ribs" on the underside made out of glass to act as cross beams. The platform will be fitted into the bow section of the boat and will be used for standing for fishing. It was formally made out of 3/4" plywood with glass on 1 side, I would like it to be all glass.<br /><br />Thanks in advance.<br /><br />Safe boating to all.<br /><br />Cheers.<br /><br />emp.

 

[Capt. Bob]

Re: How thick? Glass?

I think the glass on one side is what failed.<br /><br />Again, I am no engineer but if it were my project, I would build it out of plywood for strength and then encapsulate it with epoxy (both sides and edges). Whole boats are built this way. Then you would have the best of both worlds...plywood for strength and plastic for durability.<br />I am sure the experts will have ideas also.

 

[JB]

Re: How thick? Glass?

Hi, Ed.<br /><br />I would go with Capt. Bob's suggestion. <br /><br />I am no expert on structural engineering But I would bet that the guy who designed the original was.<br /><br />I would make the replacement with the same materials, but improved. . .Like Capt. Bob said.

 

[epresutti]

Re: How thick? Glass?

Guys,<br /><br />Thanks very much, plywood it is, pieces are cut, getting ready to "goop".<br /><br />Safe boating to all.<br /><br />Cheers.<br /><br />emp.

 

[Bob_VT]

Re: How thick? Glass?

You can bet that the engineering was based on strength and cost versus purpose. You can manufacture a stronger platform at a lesser weight with superior durability but the cost would not be worth it. A simple Aluminum sheet with extruded ribs would be far stronger. <br /><br />I side with JB and try to stick to the original design. Price out 3/8" marine grade plywood and laminate two sheets together. If it is a fishing platfrom you can mix sand with the top coat for added traction.<br /><br />The only other consideration would be to estimate why the old sheet failed? Poor drainage, poor ventilation, inferior grade original wood, and so on.<br /><br />Bob

 

[epresutti]

Re: How thick? Glass?

Bob_vt,<br /><br />Took all into account in this post, used 3/8ths, two layers with a layor of 1.5oz glass in the middle.<br /><br />Thanks again guys, this is part of my rebuild (which I have been asking about in these forums when I started April, 2 years ago!) I am getting down to the short strokes and will post progress pics on my web site, I will post the link when I have completed the project, I have been taking photo's from the start so hopefully I have a good history.<br /><br />Safe boating to all.<br /><br />Cheers.<br /><br />emp.