So, after looking at the plans and going to the local lumber yards including lowes and home depot, it brought up a question that I wanted to ask here.
What is the purpose to the 2 layer keel? It calls for 2 - 1" x 12" but 2" x 12" are more readily available. Is there a specific strength or designed purpose for the 2 boards instead of using a single piece?
I belive you misread the plans, it should say three 1 X 12s so that they interlock with each other. Go back to the cd and watch them as they bond the THREE 1 X 12 s together.
I agree that the video shows 3 layers, but, if I'm not mistaken, is for the weekender not the Pocket Cruiser. I am building the pocket cruiser and it talks about 2 layers, one with a horizontal joint and one with a vertical joint for the stem, but doesn't speak of a third. That is why I was asking if using a single 2"x12" would work.
Ryerson Clark built his weekender with only one layer for the keel. I'm not sure how he joined the joints at the front but his deviation from the standard three-ply keel didn't change the structural strength of the boat, and his keel is slimmer and less prone to rot than a normal laminated one. I think it was a wise thing to do. If you strengthened the single joint with some cookies or something, I'm sure it would be fine on the pocket cruiser also.
Cookies don't strengthen anything, though they do help with alignment as the goo cures. I dislike a 2x keel, you're just asking for warp and the timber is too big to expect epoxy to hold. The best thing you can do to a 2x12 is rip it down the middle, so you have quarter sawn 2x6's, then resaw on edge to a 1x6. This creates stable, quarter sawn stock. Of course resawing 2x stock requires a hefty saw.
Creating a 4-piece keel with 1x6 would make it that more of a chance for water to get in and rot. You don't think a solid 2"x12" work for the PC? I'm just trying to find out why a 2-piece (2-1"x12") is called for in the plans when a 2"x12" is available.
I built a Triad and it called for a 2 layer keel/ As Paul stated if you rip one 2x12 you can flip them, glue them back together and eliminate most warp. You can do about the same by finding 2 1/12s and aligning them with opposing grain. The two layer build allows you to join the stem to the keel by cutting one keel board short the width of the stem and cutting one stem board long the width of the keel where they connect. It makes for a very solid joint. I figured the best way to keep water out of the joint was to use enough epoxy with wood flour filler to coat the joining boards and ooze out. I always wet boards with epoxy with no fillers, to ensure maximum penetration, then spread epoxy with fillers on the wetted out boards and join them. I do it as a two step process but I think you could even take an hour or two between wetting out and spreading the epoxy with filler as long as the wetting epoxy is still green (not fully hardened). Paul what do you think on the waiting to part?
A can't speak to the plans as they aren't the typical approach most designers take toward large assemblies of wood. I can tell you that a 2x12 is much more unstable naturally, then 2 layers of 1x stock, glued and screwed together, especially if you oppose the grain orientation and avoid "smiley faces" in the end grain. By this I mean most folks will select a flat sawn board (slash cut), which will have a crescent shape in the end grain. This crescent shape will cause the board to cup or warp, with the natural tendency for the board to "relax" it's smiley face shape over time. Anyone with a pressure treated deck knows full well what this looks like.
To avoid these types of issues, the best thing you can do to flat sawn stock, is rip it down the middle, halving the crescent, which removes the internal stresses (most of them) in the lumber, making it more stable and less likely to cup, warp or other wise make you cuss a few years down the road. In a perfect world, all wood used in these bigger timbers would be quarter or rift cut, which has the end grain crossing the end of the plank at mostly the same angle.
Secondly, large pieces of wood, like 2x12's have natural internal stresses, captured inside the wood. If you've ever run a piece of stock through a table saw, just to have it come out the other end as a giant wishbone, you have seen these stresses being "released". There's a lot of reasons these occur and different species are worse then others, but it's mostly because trees don't just grow straight up, they twist as they grow, which places these stresses in the fibers of the wood as it matures.
Lastly, epoxy doesn't handle thicker pieces of wood well. Again it's these internal stresses that will continuously test the joint, until it fails or the wood splits. As an adhesive, epoxy is best used on 1" thick stock if softwood and 3/4" stock if hard. This serves a few purposes. First it creates a glue line to fight these internal stresses in wood and they're spaced close enough to be effective. The epoxy glue line also serves as a moisture stop. Water can penetrate only as far as the closest glue line, then is halted.
Ever seen a delicate lapstrake row boat? Dozens of dainty little ribs, on closely spaced centers, with thin planking attached? They could have simply used thicker planking and much more widely spaced ribs, but it wouldn't be as strong and more importantly as light. I know it seems counter intuitive, but lots of properly sized little pieces, make for a stronger and lighter structure then fewer, but more massive structural elements.
The deadwood assemblies on all the Stevenson designs have been a common source of displeasure for many. Delamination, warping, cupping, rot, you name it. Most of this can be eliminated with good epoxy techniques, instead of the crap glues the plans recommend. Just do a search for delaminated keels and you find dozens of cases. The usual fix is epoxy.
Part of the problem is most builders are just learning how to work with these materials and the keel is one of the first places mistakes get made. If you took a poll of all the people who built, used plastic resin or PVA glues on their keels, then some time later wished they could go back and do it again with epoxy, you'd be surprised.
In short, use epoxy and save the cheap glues for stuff that will not be immersed. Since you'll be using epoxy, think in terms of lamination, rather then glued assemblies and keep the lamination thicknesses below my recommendations (which are the same as all the major epoxy formulators). It's hard to screw up using epoxy, but it's really easy with the other adhesives and glues. For example if you use TiteBond III (a PVA) you need well fitted joints and at least 120 PSI of clamping pressure to insure you have a joint stronger then the surrounding wood. If you use epoxy, your clamping pressure needs to only enough to make the two parts touch the adhesive and best of all, the joints don't have to be well fitted, they can be cut with a hatchet and it'll still work!
The plans were written 40 years ago, when finding a reasonable piece of 1x12 was possible. Not any more. Trust me, rip it into a 1x6 and adjust your deadwood assembly to suit the smaller pieces. Yep, there's more joints, but I can show you plenty of boats with dozens of exposed and immersed joints. The key is technique and material use, not religiously adhering to the BOM.
Terry, you don't have to wait, if the wood isn't "drinking". Some species suck up epoxy like I do beer on a hot afternoon, while others are like my better half and just get wet right away after touching her. It's a feel thing, you can usually tell by looking back at previously coated areas. You'll see if it's dry or not. If it is, you should wait, apply a little more goo then go with the thickened stuff. It also depends on if you don't want parts sliding around. Epoxy is slippery when fresh and this can make alignment a pain in the butt joint, so sometimes it's best to let it get tacky, so you don't have to fight with the assembly. This is especially true on vertical and overhead work, when you might actually need something to stick, while you arrange clamps or need to get a fresh beer or something.
Boat building isn't so much about the plans, as it is about problem solving. Engineering on the fly as we say and you'll be much better at it when you're done.
That makes more sense now. My plan all along was to just use epoxy. I had read several of your postings about epoxy and decided I would rather use that then any other glue especially on submersed pieces. Thanks again for your advice Paul and Terry.
Ken, log onto West System and System Three web sites and download their user's guides. It will cover the basic procedures and techniques. Naturally they'll focus on their own products, but ignore this, as the techniques are the same for all epoxy. Also log onto the bateau.com site and watch some of the application videos. Glen-L's site is also a place you'll find useful information about using epoxy.