Plywood vs GRP

[Curmudgeon]

Yes, sorry I used the wrong word. But in a Devlin boat all would surfaces are sealed throughout the construction process. It is not a wood boat that is subsequently coated over.

[capn_billl]

I wouldn't see a plywood epoxy boat being any higher risk than a balsa cored frp. In fact it should be stronger.

I have used a simular technique to repair fiberglass boats, taking a peice of plywood precut to fit, and soaking it in fiberglass solution until saturated, before glassing it in place. I have seen this done on a boat built 1964 with no rot.

[sarafina]

Personal experience on plywood coated or encapsulated with glass/epoxy is that it's a BAD idea. Uncoated plywood, if a section fails, you remove it and replace it. A PITA and it makes haul outs dreaded and expensive when panels needed replacing, but you could do it pretty easily.

Once it was encased we might as well have just shot her... and put her and us out of the misery of a slow death... because where the epoxy failed it was impossible to replace the rotted sections without cutting thru the shell and the trying to repair and seal the hull again was impossible...

It was painful to watch.

This was NOT a purpose built ply epoxy hull where it was part of the process, this was an attempt (that failed spectacularly and terminally) to escape the constant replacement cycle of the failing ply sections.

[Wotname]

Originally Posted by sarafina

Personal experience on plywood coated or encapsulated with glass/epoxy is that it's a BAD idea. Uncoated plywood, if a section fails, you remove it and replace it. A PITA and it makes haul outs dreaded and expensive when panels needed replacing, but you could do it pretty easily.

Once it was encased we might as well have just shot her... and put her and us out of the misery of a slow death... because where the epoxy failed it was impossible to replace the rotted sections without cutting thru the shell and the trying to repair and seal the hull again was impossible...

It was painful to watch.

This was NOT a purpose built ply epoxy hull where it was part of the process, this was an attempt (that failed spectacularly and terminally) to escape the constant replacement cycle of the failing ply sections.

Sarafina,

Could you provide more detail with the actual problem you encounted; I am intrigued as to why the encapsulated section was more difficult to repair. I am assuming you must have had a significant thickness of glass and epoxy that you refer to as a shell.

Also if I am reading between the lines correctly, this "shell" may have been placed over already rotted ply or at least over a section of ply that conrained some rotted matterial. If so, that is a fault more of bad boat repair practices rather that a failure of concept.

To my mind, an encapsulated piece of ply (that is one coated with epoxy of all surfaces - with or without a lightweight covering of glass material) should be no more difficult to repair that a piece of painted ply.

OK one has to sand back the epoxy around the remaing sections of ply and re-apply epoxy (and the glass if it was there) on the new section and sure this a little more difficult than doing the same with a painted surface but it should not be a show stopper.

The ply boats I am familiar with do not exhibit "a constant replacement cycle of the failing ply sections". This leads me to think that your example may have a had a poor build quality from day one.

[Cheechako]

I have only seen the Devlin powerboats. I guess my concern would still be where there are penetrations through the wood. Especially underwater bolts holding a keel on...how is that done on the Devlins? Still ...done well I'm sure they (and others are fine boats) Heck...I still occassionally see Owens Plywood built powerboats surviving. I still think resale is tough unless you have a boat like a Devlin which has somewhat of a following.

[Nateman]

Originally Posted by Cheechako

I guess my concern would still be where there are penetrations through the wood. Especially underwater bolts holding a keel on...

My Dad is building a small stitch and glue 19' sailboat. The keel is bolted on with 5200 sealing it. It's not going to leak! When building your own boat, or being a manufacture of this type boat these area's are concentrated on more thoroughly than with GRP craft. I had concerns with the plywood rotting as well, but after witnessing the boat being built, it's not likely...

[Kapena]

I owned a plywood power boat many years ago. It was not glassed over or epoxy coated. Teredo worms ate the boat just as it was starting to rot in a big way, from standing water in the bilge. Just my experience. I think epoxy coated would be okay but it wasn't available back then and the cost of glassing the hull, inside and out, precluded me from the attempt.

[Curmudgeon]

My Devlin was full keeled with encapsulated lead ballast. I do not believe there were keel boats at all.

[sailronin]

Having owned a variety of boats including plywood/glass, cold-molded, carvel planked, and fiberglass I prefer the cold-moulded (with epoxy and glass), followed by fiberglass. A wood boat just feels more alive than 'glass and I'm more comfortable with repairs. I feel that I can work with wood (for minor repairs) better than a pure 'glass boat.

[sarafina]

The boat was a Chris Craft Cavalier. As I understand it flexing along seams resulted in steady degradation of the ply panels around the edges. Every 5 years or so there would be some part that needed to be pulled and replaced. I guess the problem was when it was coated with the shell of glass and epoxy it created a hard (less flexible) coating over the wood. It didn't stay tight to the subsurface of ply. When water got into the bilge it was very hard to get it to dry out. Once it needed a repair and the shell and bad ply was cut away and the new ply was put in place then the shell had to be replaced as well and that seems to have been problematic as well.

The boat only lasted about 5 years after the shell was put on before it was pretty much beyond help.

I suspect there may have been a way to do it that would have been successful, but the yard that did the Rose 'n Roo didn't know it I guess.

There may have been ways to remove it and put a whole new hull on but I think at that point there was damage to the skeleton.

Hope this helps a bit.

[Kettlewell]

I owned an epoxy/ply catamaran for over 12 years. I was the second owner. The orginal owner built the boat and did a good job in terms of strength, even if it was somewhat lacking in finish. The French plywood used was amazing stuff. There were no gaps or fill ins of any sort in the very thin veneers. Each veneer was furniture quality, so you could sand it down and varnish to make a really beautiful finish if you wanted to. I believe there were six layers making up the average panel which was just about 0.5 inch thick. Strength was excellent, but as always water penetration points could cause problems and we ended up with some small rot spots here and there that were easily repaired. In fact, with some spare ply and epoxy onboard you could fix just about anything yourself, which I found to be a real plus on a cruising boat. I don't think the rot issue on a well built ply boat is any worse than the rotted core problems you find on just about every fiberglass boat older than 10 years or so, and the ply problems are generally easier to solve.

[Cheechako]

"The boat was a Chris Craft Cavalier." Yep pretty common story in ply powerboats. Also, how many times have you heard about ply cabins and decks etc needing a total removal and reconstruction in sailboats? Early Ct's , Formosas and other US boats with Ply cabins and decks with a thin layer of boat cloth over.... "holds the moisture in real good!"

[Wotname]

Originally Posted by sarafina

The boat was a Chris Craft Cavalier. As I understand it flexing along seams resulted in steady degradation of the ply panels around the edges. Every 5 years or so there would be some part that needed to be pulled and replaced. I guess the problem was when it was coated with the shell of glass and epoxy it created a hard (less flexible) coating over the wood. It didn't stay tight to the subsurface of ply. When water got into the bilge it was very hard to get it to dry out. Once it needed a repair and the shell and bad ply was cut away and the new ply was put in place then the shell had to be replaced as well and that seems to have been problematic as well.

The boat only lasted about 5 years after the shell was put on before it was pretty much beyond help.

I suspect there may have been a way to do it that would have been successful, but the yard that did the Rose 'n Roo didn't know it I guess.

There may have been ways to remove it and put a whole new hull on but I think at that point there was damage to the skeleton.

Hope this helps a bit.

Thanks Sarafina, it does help.