Is it recommended to coat whole sheets of plywood with epoxy before any cutting?

[Building Wharrams]

More specific, should I first coat with epoxy the 18mm sheets that I am using for the backbone parts? I have read this recommendation on Neil's blog in a comment by Thomas Nielsen ( http://thegledaproject.com/non-productive%C2%A0night/) and I just wanted some more opinions about this.

Thank you :)

[Budget Boater]

The primary difference will be that when you go to put the epoxy fillets/glass, will you have a mechanical bond or a chemical one? That is your ultimate choice, not just for the backbone, but for your entire build.

[Building Wharrams]

Thank you very much for your answer. I did not think about it in that way. Now it is clear to me. Thank you

[patrick lennon]

I would think I would do the drawing on the plywood tape all the edges were you will be gluing the components together apply the epoxy 2 coats and then remove the tape and cut out the components. . You would get a stronger bond.

[Axel]

I pre-coated most of my plywood on the theory it would give me a nicer, thicker finish when applied  flat and save time messing about at funny angles and in confined spaces putting on multiple coats on later. You can do a single flow-coat on a whole, level sheet that gives you a thicker and smoother finish than you can achieve with multiple coats afterward. If you have the space you can lay out a number of sheets of ply and coat them all quickly and easily.

For joints, mark out the area to be glued once the pieces are cut and sand where the glue and filet will go. Given the surface area of the joints/filets, I don't believe that the difference between chemical and mechanical bonding is going to be of any significance. And here I based my choice on the research and recommendations of the Bros. Gougeon, who wrote the book that inspired Wharram's development of the newer designs. The book provides a method for testing filets/ply joints. I did a few samples and invariably broke the ply with the recommended filet size. 

Where I do disagree with the Gougeon's is in the exterior panels. I pre-coated the exterior of the hull panels as well and then spent an inordinate amount of time sanding them once installed, as preparation for the glass. I think that leaving the exterior surfaces bare saves time and effort. 

If you plan on painting the interior of the boat, the pieces can also be prep-sanded after cutting. Again, I reckoned it would be easier to sand panels flat and level on a table than when part of the boat. Overall, I can't compare this method to the alternative in terms of labor time as this is only my second boat and the first was not a ply/epoxy structure. YMMV!

[Building Wharrams]

Hello Axel, thank you for your extensive answer. I am going to need some more time to think about what I am going to do. I am also going to read the book that you mentioned. You mean the The Gougeon Brothers on Boat Construction right ( http://www.westsystem.com/wp-content/uploads/GougeonBook-061205-1.pdf ) ? Thank you for bringing that book to my attention. And again thank you for your comment. 

[Björn]

This book is the bible!

[Budget Boater]

I have never read this book and rebuilt one Wharram, built two other Wharrams, starting my third, and assisted on three foam core e-glass boats.

I do not believe it is a "bible." It is just another reference for learning. Not to mention, West System epoxy is personally my last choice for epoxy in boat building (I have used hundreds of gallons of it over the years.)

Björn said:

This book is the bible!

[Axel]

SV Satoshi, yes, that is the book I was referring to. If you have never built anything out of wood/epoxy, I recommend it as a resource. I have an older copy but I believe it has been edited several times since then. Downloading it would ensure you get the most recent version. I have a copy of Simpson's book you're welcome to have if you want another viewpoint. 

Your work space looks great. But having watched your first video, perhaps it's a good idea to get a table saw? If you're going to be machining your lumber yourself it might make things a bit quicker and easier. I found a table saw invaluable for cutting big sheets of ply too. That and a planer. 

Are you building the boat alone or do/will you have help? 

[Building Wharrams]

Axel said:

SV Satoshi, yes, that is the book I was referring to. If you have never built anything out of wood/epoxy, I recommend it as a resource. I have an older copy but I believe it has been edited several times since then. Downloading it would ensure you get the most recent version. I have a copy of Simpson's book you're welcome to have if you want another viewpoint. 

Your work space looks great. But having watched your first video, perhaps it's a good idea to get a table saw? If you're going to be machining your lumber yourself it might make things a bit quicker and easier. I found a table saw invaluable for cutting big sheets of ply too. That and a planer. 

Are you building the boat alone or do/will you have help? 

Hello Axel,
Today I made a good start at the Gougeon Brothers book. Thank you for your offer on Simpson’s book. I would love to borrow it from you for a couple of weeks. I would like to learn more and get more viewpoints and information at this early stage of my build.
I love my work space, it really feels good to me. I feel very comfortable and safe there.
Yes I think the next thing I will probably add is a table saw.
I am building alone, but I have several friends who have offered their help and I will most likely ask friends to help me when I need to position large pieces of plywood or at other stages in the build where extra hands are better.

[Building Wharrams]

Budget Boater said:

I have never read this book and rebuilt one Wharram, built two other Wharrams, starting my third, and assisted on three foam core e-glass boats.

I do not believe it is a "bible." It is just another reference for learning. Not to mention, West System epoxy is personally my last choice for epoxy in boat building (I have used hundreds of gallons of it over the years.)

Björn said:

This book is the bible!

Hello Budget Boater,
Which brand of epoxy is your favorite and can you explain why?
Thank you, Marcel

[Budget Boater]

For the last 10 years I have been using Progressive Epoxy's No Blush marine epoxy which is a 2:1 mix ratio. I use it because it less caustic, does not need amine blush to cure, it is far less expensive than most other epoxies, and you can recoat within 24 hours without sanding and still get a chemical bond.

Building SV Satoshi said:

Budget Boater said:

I have never read this book and rebuilt one Wharram, built two other Wharrams, starting my third, and assisted on three foam core e-glass boats.

I do not believe it is a "bible." It is just another reference for learning. Not to mention, West System epoxy is personally my last choice for epoxy in boat building (I have used hundreds of gallons of it over the years.)

Björn said:

This book is the bible!

Hello Budget Boater,
Which brand of epoxy is your favorite and can you explain why?
Thank you, Marcel

[Stewart Coates]

I support Axel post wholeheartedly. We always built our racing dinghies (extreme loads) using WEST, pre coated sheets, 2 coats, sanding between, and applied with high quality sponge roller, then marked and sanded the glue and fillet joints. The bond becomes both mechanical (sanding) and chemical and will break the ply first as stated. One dinghy I am aware of still racing competitively after 30 years and not a screw or nail in her. Cleaning up fillets is a whole lot easier and cleaner too (if clear finish is intended) over previously sealed ply. You will save epoxy, despite coating extra area that will become waste, as you will apply it evenly. And you will save a whole lot of time too while guaranteeing all difficult to reach areas post build, will have been sealed.