Hybrid Construction

Curly Chips with your Ribs?

Well, at last I have a set of ribs that are close enough to identical that I can use them. They match within 1/8" so I can fair them within 1/16" which is about 1/3 of the curvature between ribs, so the hull should come out fair. The trick to getting the ribs that repeatable is to wet the strips and leave them 1/2 hour or so before gluing, and leave them in the bending jig overnight, taking the same time at each stage for each set of ribs. Pernickety! I was only working every other day so it has taken a while; things would have been much faster with the ladder jig but I got the curve wrong on that and didn't feel like rebuilding it, so I just built a 4-station jig on a piece of ply.

The ends on the right will be glued to the ply bottom plank and some need to be trimmed, the ends on the left will be trimmed to the sheerline later. The ribs took 13 hours including the jig. Now I can get on with the build!

 

The bottom plank has been cut out and attached to a strongback, and the ribs have been added. I clamped the stems and ribs to the bottom initially so I could align them for fairing, but the hull came out fair first time! dimensions are spot on except she is almost 1" longer than intended; I think the stems are a hair long.

The temporary gunnel keeps the upper ends of the ribs in line and the stems on center during stripping; there was very little force required for that - only ounces - and I found that clothes pegs were enough to hold everthing in position. I am surprised how stiff it is at this stage in the build.

The hull has now been flipped for stripping. More info at Rose Lee Blog

 

Since inverting the hull I have been slowly adding WRC strips around the curve of the bilge. They seem to be going on well, no assembly problems, but the time for cutting, scarfing, thickness planing, trimming, bevelling and gluing is more than I anticipated. I'm glad I am not strip-building the whole thing!

I am not using staples so I have to wait for the glue to set between each pair - arthritis in my hands makes it difficult to work much harder anyway I figure another week to complete the stripping - about 48 hours actual build time to that point. I will post a pic when I get to that point ... I sincerely hope nobody is holding their breath

 

GASP . . . . . GAsp . . . . . gasp . . . . . . .

 

The strips around the turn of the bilges have been completed and the hull is off its strongback and flipped over so I can clean the glue and sand the strips on the inside while they are easy to get at. I have just realised that I made the boat about 2" too long: the sheer planks have to be fabricated and I forgot to allow for the scarf joints, so the ply pieces I put by for the sheer planks will not quite be enough. Fortunately I have some ply off cuts from previous work.

The ribs radiate outwards across the edge of the bottom planks so they do not run at right-angles to the centerline as usual, however it does not show very much. It will probably be more evident when the boat is photographed on the ground or in the water. I am looking forward to people noticing - or not noticing.

BTW the "stain" near the bottom of the pic is the camera's fault, it's not really there (I don't drink coffee in the workshop)

 

No coffee!!

No coffee in the work shop? Blasphemy!

Looking good build. You have probably said and I missed it, but did you edge nail the strips? With your use of ribs and the length error, I would be tempted to suggest txriverrat's method of strip-planked panels.

I have to say that there is something visually appealing about a repeating pattern. I'm eager to more of your progress.

 

The strips are glued to each other and to the ribs. I have never used nails and only rarely use screws, although I often use trenails - wooden dowels.

Earlier I was considering covering the ribs with waxed paper and screwing them to the bottom plank so I could remove them to sand the inside of the planks. The glue is very hard and I am now wishing I had done that, and glued the ribs on afterwards. Ah well ...

The river rat's system is visually appealing and a very fast build for a stripper but it won't do a round bilge, which is part of this experiment. most of my boats tend to be trials of some crazy idea or other.

 

I was thinking in terms of doing the upper planking with the TX-strips since that portion is already developable. Just a idea that busted out.

Woulda, shoulda, coulda.... I get bit with that one, too.

 

- Good idea, some strip builders do that because it allows them to create attractive patterns and motifs along the sheers.

 

What are you using for glue?

I've got a strip built boat in mind for a future project, but I'm thinking about using epoxy to put it together so that by the time I get one strip done, the previous one on the other side will be dry.

 

I used Titebond III. It is supposed to be waterproof. I have found sometimes if the wood is soaked it's grip can weaken, but it seems to be restored when the wood has dried out again. I don't plan to use glass, but it will be stroed indoors and dried out between trips so it would be OK. I shall take extra care to seal it!

I used Titebond III because it sets faster than epoxy but with this method I found I could only hang one or two strips levels a day anyway, so I might as well have used epoxy, but if you plan to use glass and epoxy over the wood you can use virtually any glue betwen the strips. If you go the conventional route and use ply station forms it will be rigid enough to permit use of stapling which will allow you to hang several rows of strips at a session.

 

TiteBond III requires a minimum of 100 PSI clamping pressure and finely matched joints to work. It also has a fairly short working time and suffers from "creep" as do most PVA's. As far as TiteBond III being waterproof, well, it just barely passes the type 1 WBP test and does soften with immersion. Both the creep and just barely waterproof issues have the manufacture hedging their bets and declaring it a non-structural adhesive and not for immersion. With these points noted it's a great glue . . .

 

Strip to strip I doubt if I get anywhere near 100 psi clamping pressure, but good strip to rib pressure is easy to achieve and they are all good flat to flat surface fits. Those joints should be as good or better than the copper tacks of 100+ years ago. Strip to strip joints just need sealing on a ribbed boat, although mine are fairly decent fitting beveled joints. The design approach yields a more or less constant bevel angle which helps.

The strip to rib joints can only get soaked from the inside at which point a leak is academic. I have never had a TB-3 joint let go without the wood failing except when it was soaked well beforehand. TB-3's "waterproof" rating is questionable, but it does recover if the joint is still attached when it dries out. Better to not let it get wet! I've not noticed any creep problem, but any joint that has a lot of constant stress (due to construction) gets dowelled on my boats, which may explain why I get away with it.

However this is just an experiment to evaluate a combined design and construction technique, I didn't intend to build it when I proposed the idea. So it's not a boat for which a long life is planned; once I've determined how it handles in the water I will be able to test and report the impact of the constant radius bilge design constraint on performance, then it will probably become either furniture or firewood - I need the space more than I need another canoe!

Dace - the wee sailboat - is stored outdoors in all seasons and is fine after 2 years and counting. Like my other canoes she was constructed with TB-3 on all joints that could be glued flat and easily clamped, epoxy was only used for joints directly exposed to water or that were difficult to fit and clamp well.

 

I use Gorilla glue which is a polyurethane for most of my joints. It has quirks of it's own (expands 3-4 times as it dries), but I don't have to worry abut it coming apart in water. The polyurethane sealants I use dissolve it a little around the edges, but this hasn't turned out to be a problem yet.

I'm not using any metal fasteners in my current build, so everything has been glued and pegged. For certain joints where there is a stress pulling the joint apart I use wooden axle pegs which have a head on them and so hold things together. It also gives a cool "riveted" look.

 

An entire month has gone by with no progress on the boat. At least my breathing has returned to normal and I am trying to just work through the rotator cuff injury and arthritis in the hands. I got physio and massage therapy but the problems just came back however lots of work in the garden seems to be helping things to loosen up . Hope to return to the boat in a few days . Thanks for the support and ideas and I will post progress when there is some