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View Full Version : plywood on frame boat - epoxy or 5200 for attaching planking to frames?



SScoville
11-14-2010, 05:25 PM
I want to to glue and screw my plywood planking to my frames. The boat is Harry Bryan's Shantyboat. Other than less cost and easier application, what are the advantages/disadvantages of using 5200, or something similar, to epoxy here? From my experience with both, it seems the main difference would be that the caulk would be more flexible. I'm not sure flexible is desirable, however.

MiddleAgesMan
11-14-2010, 06:41 PM
Epoxy is so strong you could remove the screws once it cured. Point loading would not be a factor if you left them in. In other words, the epoxy is doing all the work and the screws are superfluous.

On the other hand, 5200's flexibility might cause the fasteners to work and loosen over time. I doubt you would save any money either--a tube of 5200 is probably more per ounce than most of the name brand epoxies.

I'd say use epoxy with drywall screws, removing them when the 'pox is 80-90 percent cured. You run the risk of breaking one now and then but there's a little trick to making sure they aren't locked in by the epoxy: when the cure is about 80 percent, back out each screw a half-turn to break the bond then drive it back hard. Do this one screw at a time. The screws can then be removed at leisure when you are sure the 'pox is at full strength.

Mike Vogdes
11-14-2010, 09:05 PM
What do the plans call for?

chuckt
11-14-2010, 09:50 PM
What kind of wood are the frames and what kind is the ply?

SScoville
11-14-2010, 10:03 PM
The plans do not call for any adhesive between the first layer of planking and the frames - just screws and then glue between the 2 layers of planking (double diagonal cedar, alt. plywood). The frames are longleaf pine and the plywood will either be Hydrotek (meranti) or Ocumme.

wizbang 13
11-14-2010, 10:08 PM
Use either, I would lean towards epoxy.Glueing together 2 layers of ply will use lots of epoxy.

cap'nRod
11-14-2010, 10:42 PM
PL400 would do a fine job. Much like epoxy in its holding strength, but unlike epoxy it retains just a hint of flex that allows it to move with the wood. Plus you can buy it in big tubes for cheap, and its readily available.

Thorne
11-14-2010, 10:44 PM
Epoxy is the Gold Standard of adhesives, although the higher quality ($$) non-blushing stuff far excels the cheap off-brand blushing epoxies (like TAP Plastics).

The only alternative I'd consider would be PL Premium used between the frames and the ply. Almost any good glue will be stronger than the wood, but waterproof glues with some gap-filling qualities are the best. Stick (ar ar ar) with epoxy for coating surfaces, gluing ply together, and any exposed fillets or seams -- PL Premium will bubble badly when not used between faying surfaces.
http://ecx.images-amazon.com/images/I/41THOyEu%2BWL._SL160_AA160_.jpg

Don't glue over paint (even red lead), as you're only gluing to the paint instead of the wood. If you want to seal the edges of the ply, use CPES or unthickened epoxy.

David G
11-14-2010, 10:50 PM
PL400 would do a fine job. Much like epoxy in its holding strength, but unlike epoxy it retains just a hint of flex that allows it to move with the wood. Plus you can buy it in big tubes for cheap, and its readily available.

I agree that you could use PL Premium or some other polyurethane glue that comes from a caulking gun. Realize, though, that Rod is - once again - incorrect on the details. This type of product is NOT "Much like epoxy in its holding strength..." In fact, my own rough and ready testing would put it at between 50 and 75% of epoxy strength. I think John Welsford did some more rigorous testing and came out somewhere in that same ballpark.

In this case, there's enough surface area that the reduced holding power would probably not become an issue. What will be an issue, though, is making sure to spread only the amount of material that you can quickly cover. This type of goop wants to skin over fairly quickly, and this can present an ever spread/squeezout. Can even result in a lumpy surface, as the thicker spots telegraph thru.

john welsford
11-14-2010, 10:52 PM
PL400 would do a fine job. Much like epoxy in its holding strength, but unlike epoxy it retains just a hint of flex that allows it to move with the wood. Plus you can buy it in big tubes for cheap, and its readily available.

I dont believe that Rod is correct here and would not recommend it. In part because I've never had what I consider a satisfactory test for a strutural join with any polyurethane ( and I've tried a lot of them) and partly because trying to get a thin film on each of the two faying surfaces with cartridge polyurethanes is going to be very difficult as it skins over very very quickly.
I'd build per the plans with no glue between the frames and skin, and epoxy in between the skins. Second choice would be recorcinol and third would be MUF

John Welsford

James McMullen
11-14-2010, 11:19 PM
I would follow the plans to the letter. Harry Bryan has built quite a few wooden boats, and he's widely considered amongst his peers to be someone who knows exactly what he's doing.

This is in rather sharp contrast to our dear cap'n, who hasn't actually built any known wooden boat himself, nor ever offered a single bit of advice on this forum that has been endorsed or agreed upon by any actual shipwrights.

Mike Vogdes
11-14-2010, 11:46 PM
Just wondering if Titebond ultimate three would be an alternative between the laminations? Titebond claims its waterproof but after reading their data it says not recommended for continuos submersion. WTH.... But if the hull is glassed with epoxy in the end anyway, maybe it could be a way to save of few bucks. I have never used Titebond for laminating.

James McMullen
11-15-2010, 12:19 AM
Titebond III wants clamping pressure which is going to be hard to provide evenly and thoroughly. You're probably best off with gap-filling epoxy which needs nothing other than contact, more or less.

JimD
11-15-2010, 12:35 AM
Epoxy.

SScoville
11-15-2010, 07:54 AM
Maybe I'll call Harry. I'm going to use epoxy between the layers of planking and I'm going to epoxy the exterior of the hull. It just seems it would add so much strength to glue the planking to the frames instead of relying only on screws.

erster
11-15-2010, 08:38 AM
Sealing seams with even chewing gum and proper fasteners goes a long ways to increase the life of any hull no matter what shape or size or even use. Wood with the multiple grains does not allow two pieces to seat and mesh with zero tolerances in any way. The decision that you need to decide is what you personally feel comfortable with along with what you wish to invest for each hull too when choosing products.

Black-Jack
11-15-2010, 08:46 AM
SScoville-

if I may ask- where are you getting your hydrotech ply and what is the price youre paying?

thanks

chuckt
11-15-2010, 08:50 AM
I went with epoxy on my restoration using Douglas fir frames epoxied to meranti. I do not know if the pine presents any issues being glued to ply. Suggest you call the West System (Gougeon) tech guys on that question. 5200 maintains some flexibility so, the theory goes, will keep doing its job despite some movement of the wood. I've heard in mentioned many times on this forum that 5200 requires some clamping pressure which could be accomplished in your application by screws. My 18' runabout was glued to frames using 5200. the first layer was screwed on. This is Don Danenburg's method too. You may want to get his book if you go that route.

SScoville
11-15-2010, 09:29 AM
Harry says 5200 is probably best in this case, but not necessary. Also, he's presently building his first boat to this plan for a client. As for the cost of the 5200, it should not take much as there are only about 10 sets of frames. I have more experience with epoxy than with fasteners and other glues as I have built 2 stitch and glue boats and no others yet. Boat builders around here seem to think that 5200 is God's gift to boats and so almost always recommend it. Learning to use the right tool for the job is one of the best lessons I've learned in boatbuilding.

I'll take some pics once I get all the frames set up. It's just not much to see right now.

Bob Smalser
11-15-2010, 10:35 AM
Titebond III wants clamping pressure which is going to be hard to provide evenly and thoroughly.

Further, 5200 requires even more clamping pressure than Titebond for it to continue sticking under wet conditions.

Let that boat fill up with rainwater at the dock for weeks at a time like many of us do here, and you may be in for some unpleasant surprises when you can pull ropes of it from beneath your frames..

http://pic20.picturetrail.com/VOL12/1104763/7738131/103956088.jpg

Chris Coose
11-15-2010, 10:52 AM
I don't know why people don't follow directions and then I'm really baffled by those that would second guess and think to improve.
Ain't there enough to do as directed?

Peacefuljourney
11-15-2010, 11:28 AM
The plans do not call for any adhesive between the first layer of planking and the frames - just screws and then glue between the 2 layers of planking (double diagonal cedar, alt. plywood). The frames are longleaf pine and the plywood will either be Hydrotek (meranti) or Ocumme.

I would stick to the plan, or ask strongly the designer before doing anything there. Also for the long run, I would prefer to put red lead there and screws like the plan have asked (Or copper rivets as I love those). Also for later repair not having adhesive there is a good idea, if rot go there because of the glue failling, imagine taring apart half of the frames trying to remove the epoxy where it did stick to repair the framing or the planking...

SScoville
11-15-2010, 01:05 PM
One of the problems in this case is that the plans are incomplete, really just study plans.

Peacefuljourney
11-15-2010, 01:12 PM
One of the problems in this case is that the plans are incomplete, really just study plans.

Are you not helping the rare wood boat designer so they can survive? They are disapearing fast with the fast production, I want it today and nothing to do, boat industry that we are living in...

SScoville
11-15-2010, 02:57 PM
Are you not helping the rare wood boat designer so they can survive? They are disapearing fast with the fast production, I want it today and nothing to do, boat industry that we are living in...

I think you're asking if I ordered study plans and am now trying to build from them instead of paying for the full plans. If that's the question, the answer is no. Bryan just has not finished the plans and hence they only cost $20.

And it's not just the boat industry.

Peacefuljourney
11-15-2010, 03:18 PM
I think you're asking if I ordered study plans and am now trying to build from them instead of paying for the full plans. If that's the question, the answer is no. Bryan just has not finished the plans and hence they only cost $20.

And it's not just the boat industry.

Sorry my bad then, misunderstanding ;)