1967 48' ChrisCraft Constellation Restoration

Hummm since when did you know what I have done? is it because I have mentioned epoxy and 5200? funny, but hey you guys know it all, I forgot

 

Hi Robster,
I am betting on your 3m5200 over cotton; that stuff is more than tenacious. What does concern me is the possibility of the epoxy eventually locking in moisture. Any tiny little bit of a crack or fracture in the epoxy layer will let in the wet; when that happens how will it breath out?
Interesting that the rot was above the waterline. How do you explain that?

 

Yes that is a valid point only if you are using untreated wood. I pressure treat every piece of wood I put on the boat with penetrating epoxy until it has soaked most of the way through the wood, then before I fasten it to the boat, I saturate the joining wood with west system epoxy. let it dry and then glue each joint with 5200, making sure I leave enough room for movement and flex.
I use the fasteners to position the wood in place until the adhesive cures. I also go on the inside and double seal everything with 5200 and epoxy.

I don't think anyone has gone to this measure when working with wood and epoxy, at best they usually just coat the wood with epoxy and then when it stress cracks, it will do as you mentioned.

 

The rain water was the cause of all the rot above the waterline. Rain has all kinds of organic deposits in it that creates fungus and mold, therefore exponentially spreading rot. unlike salt water preserves wood because of the salt content in the water

 

Rob, you do realize that all penetrating epoxies (yep, every single brand) aren't not water proof, right? They let in huge volumes of moisture vapor, in fact shellac is actually better at preventing water vapor ingress then penetrating epoxies!

You also realize that 5200 will permit the planks to dance on their fasteners, because they're not driven solidly home, but floating on a bed of flexible goo, right? 80% of the longitudinal stiffness of your yacht, comes from the plank edge set and structure/planking interface, being rock solid from tight fasteners and frictional fits of the adjoining planks and frames.

Lastly, you do realize that 5200 is a polyurethane and absolutely will not remain stuck to wet wood, right? It pulls off like a big, long, rubbery piece of string, but you'd know all about this, being the new age kind of boat repair kind of guy you are, right? You don't really think you're the first guy to have tried this treatment do you? Pleeeease, 3M-5200 and penetrating epoxy have caused more yachts to be dragged to the land fill than about anything else, especially carvels with goo'd up seams.

 

Thanks for the info, I am not trying to act like I know everything, in fact the reason why I try new things is to learn better systems of boat building. I consider everything people say, and that is also my main source of learning. But I also know that this boat was built exactly the way you would advise me to repair it, and was the reason why it was being sent to the burn pile before I rescued it. So the old cotton caulking and soaked wood didn't help it much.

We have to come up with a better way of wooden boat building that never lets the wood get wet. If you have a better idea that would have that result then I would be very interested.

 

Yah, that's "batten seam" construction. 5200 is the RECOMENDED method of caulking. All the modern runabout restorations follow the same method. Batten seam Sport fishers do the same. Not sure about epoxy sealing above the waterline. Below the waterline epoxy is well proven , both outside and inside surfaces have a high moisture content and live in a stable temperature range. . Above the waterline is a good question ? Only time will tell. Sunlight and heat cause wood to Breath , move and subject the wood to a wide range of moisture. Make sure you paint your boat white !! to minimize this thermal wet dry influence. Boat looks great...keep up the good work !!

 

Michael, you are absolutely nuts. Why do you speak of things you haven't a clue about? Why do you repeatedly say ridiculous things like this? It's something that occurs with you nearly every other post. How about this, speak what you know, not what you think you know. Not a single restorer that I know (I personally know dozens) uses 3M-5200 on these rebuilds. Everyone has seen the testing results (except Michael) for both non-cyanoacetate reacted polyurethanes and penetrating epoxy. There are a few hold outs, especially on penetrating epoxies, but not the folks doing repairs on boats repaired or restored with these goo's. Hell, I was a hold out for a while there too, but the jury is in folks.

Both the moisture cure polyurethanes (single and two part) and penetrating epoxies (A and F molecules) have their place and uses, but these have been dramatically curtailed in recent years with the advent of testing and long term trials.

Interestingly enough, what has been found out is the old timers that designed these systems, actually knew a lot more about what was going on, then we gave them credit for and the traditional repairs (with modern materiel and technique updates) work the best. For example the best system for carvel repair is pounded caulk or wedges, which is precisely the approach the old timers would have taken.

Batten seam is a self sealing technique and usually doesn't need "bedding" to work effectively. Most manufactures went away from this building technique once other building methods took hold, namely developed plywood hull shapes and building techniques. What most batten seam boats suffer form is loose fasteners, which permits the planks to move, which erodes the plank edges and "eggs" out the fasteners holes. All of this movement lets water force it's way past the seams and into the boat. The usual fix is to restore the fastener holes and refasten the boat. This assumes the plank edges haven't been ground to pulp, waiting on the owner to do something about the fasteners. Good fastener holes permit the planks to be drawn down tight against the battens and bingo, assuming good plank edge fits or a cheater or two, the boat is tight again.

A very similar situation is true with carvel builds. If the movement is addressed early, you can just restore the fastener holes and refasten the planks down with few worries. Naturally, this assumes the boat will be properly caulked, which edge sets the planking and turns the hull from an assembly of loosely fitted boards to a homogeneous hull shell. Unlike many other building methods, carvel relies heavily on other structural elements to share in load bearing and strain transfer. This means if a carvel is permitted to "work" against her fastenings, she'll tear up a lot more of her structural frame work. A carvel is easier to fix, but usually requires more things to fix, while a batten seam is more difficult to repair, but the repairs are usually limited to specific areas.

To answer Robster's questions, yep, there are repair strategies in place, though most are application specific, though each will have similar approaches. For example, underwater seams on wood, the modern goo of choice is polysulfide, not polyurethane, because it will stick to wet wood. Another reason to use polysulfide is because it can be repaired, which is a big deal breaker for most modern goo's. If a goo works, that's great, but if it tears out a bunch of wood, when you try to remove it, then it's the wrong goo to use, because now you've got to repair the plank edges too, not just fix what ever the original problem was. Repairability is a huge consideration for the reputable builder/restorer. If you can't repair you efforts, you've done a great disservice to the yacht as a whole.

 

Robster, as a guy who works with fiberglass and all sorts of resins every day, I am very intrested in your above reference to a penetrating epoxy that "soaked most of the way through the wood". If true, this is a truly remarkable product. Would it be possible for you to prepare a test piece, say something like a 1" x 3" plank, then saw a couple inches off the end and post a photo of this saturation? Thank you very much, I would really like to get my hands on such a product.

 

I'd like to see that too!

 

Wow, this is a great thread. I especially like PAR and fg1inc's contributions. Interesting how pissy and righteous we can get sometimes; it's almost as if we were discussing politics or religion.
Now that I am re-reading the various posts it occurs to me that much of the critique focuses on the fasteners being stationary and not moving with the various loads and flexing of the hull, resulting in the fastener holes widening.
Would it make sense to use no fasteners and use polysulfide goo instead of polyurethane?

 

NO, The cotton makes the plank a rigid panel. Any "goo" will let the planks move and will not create a structural panel. People that do that are amateurs with no knowledge of boatbuilding. PAR knows what he talks about. This has nothing to do with politics or religion but facts and technology that was developed through millennia of experimentation. Making a square wheel may be novel, but it will just be crap and not turn. That is the equivalent to what you are trying to re-invent in a boat.

 

I get what you are saying about the cotton making a unified rigid panel; but when I look at Robster's pics I can see that he is glueing to the frames and stringers; can't help but thinking that if the longitudinal stingers and frames are unified with the planking that the result will be a unified society of parts that will move in concert, much in the same way as the cotton would. Maybe I'm missing something, but it seems that Robster is creating a rigid grid; possibly better than a rigid panel?
Maybe 5200, as PAR points out isn't the best choice, but I'm not really sure what a square wheel has to do with this.
I have heard people say, "If that was a good idea it would have been thought of before".

 

It is not that it would've been thought of before, but that is has been tried of before and failed. He is making a hermafrodite hybrid of methods that will not work well. He is also spending a lot of time and money on something that will not be worth it.

 

3M-5200 is an adhesive/sealant, with a lot of adhesive qualities. It also cures much harder then most folks think, but it still has huge permissible distortion and elongation properties, which make it completely unacceptable in this application. If you want a bonding and bedding compound under a winch stand base, that will remain in service for the next 20 years, then 3M-5200 is a good choice. Of course when you remove the winch stand for replacement or service, it'll tear up what ever it's attached to.

What's needed in this application is a very rigid faying surface to faying surface interface, not a flexible one, such as that provided by a sealant like 3M-5200. If you use a flexible interface on the faying surfaces, then the planks will move. With this movement the first thing to go will be the planking fastener holes, followed by bent and broken fasteners, followed by egged out fastener holes in the frames or battens, followed by smashed faying surfaces, followed by failing local load bearing neighboring structural elements, that have to absorb the additional loads, no longer carried by the failed fastener holes, faying surfaces and other assorted "issues". Did I mention the leaks? It's a vicious circle and it all needs to be addressed in a logical fashion or you're just trying to piss up a rope.

It would be nice if there was a miracle goo in a can that could rescue old boats, but not for trying about every sort of goo and resin system available, there just isn't one.

It's absolutely false to believe he's "gluing" anything with 3M-5200, he's not. Will it be attached, maybe, assuming it doesn't get very wet (imagine that on a boat under the LWL), but with several hundred percent (yep, that's right several hundred percent) elongation of 3M-5200 gluing isn't the term I'd use. In other words if the planks want to move in a mini elliptical orbit, then this type of "adhesive" will happily let it move in this motion. How long do you think the fasteners holes will last with this going on. BTW, this is precisely the motion you can expect from a powerboat, as a result of the many different types of machinery vibrations aboard.