glue or epoxy plywood together?

[kaptainkoz]

Hello All.
Lets say I wish to double up 2 pieces of plywood, face to face for example, a pair of 3/4 sheets to make an 1 1/2 inch transom. I know enough to use marine plywood or at least exterior so it is made with waterproof glue. I also know that I should thin epoxy and coat the boards on all sides to seal them. heres where my dilema come in. The two faces that are being joined.... it is better to:

A) Seal both faces with resin, let dry, then waterproof wood glue and clamp?
B) Just use waterproof wood glue on the two faces, clamp and dry (no resin sealing)?
C) coat both faces with resin, clamp and let dry (no glue at all)?

Im in the planing stages for a design for a pilot house/phone booth type enclosure built right on the existing center console of my 200CCP. im thinking the roof will be 1/2 inch over my head then taper to 1/4 for the roof overhang over the seat (dont need it to be 1/2 all the way to save weight). Also, I will be joining plywood at different places for reinforcement so there will be some plywood ends connected to plywood faces. The whole thing will be glassed  and gel coated but im just curious what will make my unions the strongest AND most rot resistant.
Any advice will be appreciated!

[saltfly]

Well  all resins are bonding agents. So I guess most will use what they think is best. But I don’t mix bonding agents. As for me, any time I’m piecing plywood in a transom. I always use glass in between each layer and make sure it overlays the joint. I want that extra strength. I feel the transom can never be to stronger. So far none of the transoms I’ve done. Have never cracked or broke in any way and some are 30 years old. Also Its not recommended to mix polyester, vinylester or epoxy. Also I only use vinylester or epoxy. I don’t like polyester resin.
Also It sounds like you are bonding before installing in the boat. That will cause you  big problems. Most transoms are carved. So I use ¾ inch and screw each piece to the other to pull it together. I start by screwing the first pieces from the out side of the transom, so it is pulled tight against the out side skin, if you did it that way. You didn’t explain if you took out the hole transom and you are completely open. Or did you leave either the out side skin or the inside skin?

[Blue Agave]

I vote for option C.

[GoneFission]

I like option C as well, but also agree that a layer of glass between the plywood is a very good idea.

[dirtwheelsfl]

epoxy all the way for gluing 2 pieces together. the wood will rip apart before the bond between them does. like saltfly said if its a transom id put glass between the layers, if not just wet both sides out and let that penetrate a good half hour then take a notch trowel and spread some epoxy glue thickened with cabosil and clamp together. i would use epoxy for everything, but at least use it for bonding the 2 pieces. youll not have any bonding problems for the other resin because its all between the wood.

id just use 1/2" all the way for the hardtop. im not sure what you mean by  

"Also, I will be joining plywood at different places for reinforcement so there will be some plywood ends connected to plywood faces"

if its what im thinking (like joining the top to the sides) theres a few ways to do it do you have any pics?

well epoxy will be strongest and most rot resistant, but you wont be able to gel over it,  youll have to paint...

[kaptainkoz]

Thanks for the input everyone. To answer one posters question, I am not actually doing a transom in ply (I will pour it) i was just using that as an example because its easiest for most to understand what I was getting at, altough I like the suggestion of glassing inbetween the pieces. As far as the roof of my project pilot house goes, I want to make the roof out of 2 layers of 1/4 inch ply, however I dont think the stern half over my head needs to be 1/2 inch and I want it light because I do not intend on having any rear supports. I will also be doubling up the plywood at key points next to the windows where there will not be much ply left after windows are cut in. It will be a plywood shell with plywood bracing and skeleton so I was concerned with bonding and waterproofing. I will be using minimal screws to pin it together but I intend on it being 100% glassed.
Epoxy resin sounds the strongest but by one of the comments it seems you cannot gel coat it? can you gelcoat vinylester? i dont want to paint, I like the look of gelcoat.
What resin is my 200ccp made with? And if im doing stringer repair can I use different resins (for example epoxy on polyester or vinylester)
Thanks again for your help and advice. Of course I will post pics when the project takes place but im thinking its going to be an over the winter project.

[dbiscayne]

gelcoat won't stick to epoxy, at least in most cases.  Supposedly West has a gelcoat system that will work with epoxy but I haven't ever seen it first hand or known anyone that did it.  Definitely better off using vinylester.  Polyester resin would be my last choice though I think it'll work with this project mainly because none of your parts will be subject to standing water/trapped humidity/below the water line for a long time.

You're boat is probably made with vinylester resin, could be poly?  I'm sure someone here will know.
General rule of thumb is epoxy will bond to any of the types of resin & will bond the best.  Epoxy would be the best choice when doing repairs, attaching new fiberglass to old, because it's bonding properties are that much better.
Vinylester & Polyester will stick to each other but won't stick to Epoxy.  They'll work OK as long as you prep the cured surface, you need to wash & scuff up the old surface before sticking anything to it, and end up with a mechanical bond.  Read up on Amine Blush if you can.  They're fine for new construction when you're laying wet glass onto wet, getting a chemical bond, the layers will stick to each other very well.

Someone mentioned using thickened epoxy & spreading it with a notched trowel, thats the ticket for getting two things stuck together forever & ever, wether using vinylester or poly or epoxy, & don't use so much clamping pressure that you squeeze all the resin out you want to leave a layer in there.  Just coating the two pieces with regular non-thickened resin & laying them on top of each other won't work too well.

[dirtwheelsfl]

what do you mean by plywood skeleton and bracing? if its done right youll have nothing but the shell (walls and roof) glued and glassed together. no need for anything else...

any repairs youre not gelcoating over (stringers) ought to be epoxy. what are you fixing exactly?

[kaptainkoz]

dirt Wheels... i guess the easiesr way to explain what I have in mind is similar to framing a house. It will basically be a 3 walled box with a really big roof. However I will need to "frame" or as I called it, "skeleton" the inside to add rigidity. This will also allow me to use lighter materials (1/4 and 1/2 inch ply instead of 3/4) and allow me to multi task some of the bracing as shelves and mounting points for the canvas enclosure. I am thinking of making aluminum framed side panels that will hinge at the pilothouse and swing to the gunnel to make it more imprevious to the october/november spray in your face on a choppy day. Yes, I will be fine in the phone booth as the driver but I want to shelter a passenger or two as well. Heres a rough sketch of where im going with this



As for exactly what I am fixing, I am thinking that I will use epoxy resin when I pull up the floor to fix any delamination of the stringers or anything sub deck that needs attention. I will have to cut acess holes in the stringers to get the wet foam out so I will need to close off those cuts. Im thinking I will go through the sides to not disturb the tops or height of the stringers. I think a side repair with a suitable number of layers can be as thick as it needs to be without getting in the way of anything. I also plan on cutting out the keel board and refilling it with a pourable transom material. That will also get a coat of epoxy and glass.

[dbiscayne]

I'd ask the maker of the pourable stuff about using it to fill the keel stringer before you go too far with that, as a transom material it works because there generally isn't any flexing at all back there, you've got a nice thick rectangular shape that resists flexing.
Along the keel is a different story, it's eventually going to flex a little, as designed, and I believe the pourable material will crack before it flexes.  If you put something that stiff next to fglass that flexes you'll either end up cracking the poured stuff or more likely getting a crack in the fglass along the poured keel.  Basically super stiff next to flexible without just the right amount of gradual reinforcement is a bad idea.

[GoneFission]

Koz - don't know if you've seen it, but you might get some ideas from Pacific Pilothouse:

http://www.pacificpilothouse.com/index.html  

Good luck!!

[saltfly]

GF is right take a look at pacific pilothouse. And then I wouldn’t use any wood at all. I would make a wooden  mold and make it out of nothing but glass.

[dirtwheelsfl]

are you building onto the console or taking it out and making one unit?

if it was me id build the whole thing out of 1/2". mock it up as all bare wood with screws and cleats, take it apart and laminate like an 8oz cloth on each side of the wood. then mix up some epoxy/cabosil and glue and screw it all back together. take all the screws out and use biax tape on all the corners outside and inside.
THEN add shelves and whatever you want to the inside. easy quick and clean looking...it will be plenty strong, especially with that vertical piece on the bottom sides of the top extending back

[kaptainkoz]

Wow! Thanks guys. I appreciate the ideas and brainstorming.

DBiscayne - good point on the flex. Didnt think that far into it. I think I saw something somewhere where someone poured one. Doesnt mean it was right and what you say will definitely be looked into. I do want to go with a synthetic so I never have to worry about rot ever.

GF... yes, I have seen Pacific Pilothouses site and they look cool. They have helped reinforce my idea a bit, and my idea looks a bit like one, but my design is mostly based on the contours of the existing center console and how far back I want the roof to extend. I also heard they are super expensive and I will need to make some sort of a removable mounting point for the side curtains I am thinking about. I want the canvas to be able to swing out and attach to the gunnels to blast through the november wind driven spray and keep more people than myself in the booth somewhat non drenched before we even drop lines.

yes, Dirtwheelsfl, I plan to bolt it right to the existing center console. Even if the 246 project happens, I will definitley want to use my 200CCP's center console. I set it up really well for what I need and I would not want to re-rig all that I have done to it as its set to my needs and liking. the 1980 246CCP is the same exact center console as my 78 200ccp, except it seems to be one tier higher featuring a storage area under the dash board cluster. I definitely do not want a higher center console to try to see over as I sit and pilot the boat. I have also ruled out Pacific Pilothouse because I do not want to add a fraction to the width of the center console's footprint. The beam width is a bit narrow for me so even a few inches off of each side to bolt down the Pacific Pilothouse will not be acceptable to me. I want to go way too custom for a pre made. The CCP's center console has this great, almost 2 inch recession about a foot up.... thats where my design will sit, start from and bolt to. And yes, I will flip the CC over and glass in reinforements from the mounting flange on up. Also, call me strange, but I do not have a tach nor a trim gauge. I do not feel I need them... especially the trim (***I do have a tach set up on a bullet connector and a 12V adapter for temporary use when dialing in motor diagnostics... other than that it is too big of a gauge for my liking). I went very simple on the guages - head temp, fuel, voltage and amps. Yes, two guages for battery health being I do alot of fall night striper action which uses alot of juice for my lighting. Full LEDs would be great and im getting there (bow, anchor, gunnel and storage lights) but the quality LED deck floods are like $170 each! They will wait. As cool as they are I just cant justify the cost.

Saltfly, true. Maybe. Weightwise im not sure if it would be an advantage to go only glass. If it wasnt so much of a work in progress and if had a proven finished product or detailed layout then yes, a mold of a 100% glass unit would be possible and a better looking finished product than glass over wood. 1/4 to 3/8 ply with 2 coats of mat on each side is probably lighter and stiffer than a 1/4 inch of glass alone...maybe??? Chime in someone if im way off the mark. I want to be able to hold the grab handles aft of the side windows in a strong roll without the entire booth flexing. I think the glass lay up would have to be massive for an purpose that isnt that critical. Hell, im not even going to use marine ply. Exterior AB will suffice. If I had a blank check I would probably go Coosa. I like that stuff. Nidacore is a bit too creepy to me with the heat expanding honey combs and the lack of screw holding (im not looking for a fight... i have samples of both and I have used neither... just an observation based on toying with the samples and what I read)

I really cant wait to get started and post the madness with pics, but its definitely a winter project. Even if I do not get the 246CCP I think it is going to happen this winter on the 200CCP's center console.... where this center console gets mounted in the spring is still up for grabs.

I am taking reservations for (potentially, if I get the 246CCP) the following items for sale:
246 CCP center console ( I will use the 200ccp's)
246 CCP 6 ft coffin box (I will use the 200CCP's and slide the center console up 2 feet for more room in the aft)
The custom mahogany splash well bench that I made and have on my 200CCP (tramsom will be closed and a bracket installed)
200CCP original dashboard panel (I have this NOW for sale if anyone needs... I redid my dash a while ago)
200CCP fuel tank tub (Cover? depends. The 246's cover is shot! IF its the same size then im taking it from the 200. IF not your in luck)
200CCP under deck in floor bow bin
200CCP splashwell/livewell - bin, cover with hatch
the entire aluminum factory grab bar and the stainless lightbar set up I added on my 200CCP (all the hardware would be gone to accomodate the pilothouse) Includes 4 lights and the anchor light
200CCP windshield which is in fair to good condition. Its clear but get the sun to hit it right and it shows its age

When it becomes a reality I will post them in the correct forum with pictures. make offers...Im not going to be a pig about prices. When will this all happen? I have a restored 1988 150 Evinrude on Craigslist for sale ( http://longisland.craigslist.org/boa/2511530717.html ). As soon as I get that cash in my hand it off to buy the 246 and the sawzall will send glass flyin!