Plywood canoe

A couple of thoughts about using wire, if you go that route.

1. Make sure your wire holes are spaced a decent distance from the panel edge. I found 1/4" to be about minimum and 3/8" was great in those places that really needed convincing. I only ever had problems with tear out with too little hole edge margin.

2. Pre-bend your wires. I put two 90 deg. bends in my wires to match the atticipated spacing between hole pairs. This sits the stitch fairly flat inside the hull and twisting now concentrates more on pulling the panels together and alligning them rather than trying to straighten out a curved stitch. It also holds it's tension better because there is no where for the stitch to relax.

Do you plan to roll the hull over before fillet and glass? That would be my plan. Sitting upright, you can lay straight edges across the sheer edge in multiple locations to check for twist in the hull before you start glueing and glassing.

 

I would not dare move it without fillet and glass taping the chines. You have given me an idea, I can throw ropes over the hull and pull the straight edges tight to the sheer to check for twist.
The shape of the sheer line is not fixed. I have left some extra freeboard in the middle and intend reducing the height of the bow/stern to give a flatter sheer. Reasons being, reduce windage, it looks too banana shaped to my eye, fitting the gunnels will be easier and as I will be cartopping, it would be nice to see where I am going.

Regarding shaping the bow, the drawings show the probable shape of the plank ends but the note says "cut curve on ends & trim fair later" so I have left some excess wood which is why the bow looks so lumpy at the moment.

 

if you cannot roll it to the right way up then you dont have the panels fastened together well enough...it only a light canoe......you will make a lot of work if you tape the joints on the outside.....

 

I would not roll it with just adhesive tape, so that would mean covering it in ties which defeats the object.
I appreciate that the outside tapes will involve extra work but using 4mm ply on a canoe this size is pushing it and I will not be glass clothing. Had it been 6mm, a good join with internal fillet and tape is considered adequate for light duty.

 

You have to be very carefull if you want to force a profile or section on an S&G bow or stern that is being finished bright.

If you glue the planks in place, and then force a shape, its easy to sand past the top veneer and reveal the hidden plys. Not a structurally bad mistake, but not a 'traditional' look if you want a continuous normal plank effect.

 

Don't worry too much about a little twist in the hull; even with the planks assembled it will be so floppy that it is easily straightened. The time to get seriously precise is when the gunnels and decks are installed, at which time the whole thing will start to gain strength and stiffness. A couple of long levels across the sheers will tell you everything you need to know at that stage, but make sure they agree first!

 

But dont you FG the chines well before you turn over and do the gunnels and and deck ? That makes the hull shape permanent well before the deck goes on.

 

the problem is latestarter that you are doing it arse about face.....you glass the inside first with everything in place ..if the bottom is flat you stand on it and do the glassing....what does it say at the bottom of all my posts.....

 

No you dont - no one does it that way at all.

You have to get the upside down hull aligned, chines glassed and the outside fibreglass.

read up any youtube 'how to' from the major builders.

 

Well crap! That why all of my kayaks float upside down.

On a boat this size, I would build it right side up. I wouldn't begin to know how to begin to built it upside down. Everything that I'm going to assemble and glue in the beginning is going to be on the inside. That said, you give 100 people the same set of boat plans and tell them to build it, it's going to get built 100 different ways.

"no one does it that way at all."

"You have to get the upside down hull aligned, chines glassed and the outside fibreglass."

I do and no you don't.

I fillet and tape and glass and install bulkheads and install frames and install shelves/clamps/sheerrails/inwales/gunwales all right side up and before I touch the outside. Why? Because it's easier. Because by the time I flip the hull over, it's nice and rigid and fixed. Because now when I glass and tape, I'm only concerned about fill and fair and I'm not concerned about whether the hull is going to shift on me. My two most recent kayak builds.

http://www.boatdesign.net/forums/wooden-boat-building-restoration/11-kayak-loggerhead-42099.html

http://www.boatdesign.net/forums/wo...ration/mysticshore-12-gets-started-39315.html

But, just because I do it this way doesn't mean another way is wrong. It just means it's different. If I was doing this project, I would build it right side up. At least until I figure out a different way was better. But, I'm not building it. I have made the subtle suggestion that flipping it might make it easier, but it's up to the OP to decide which information is useful and the information that isn't. It's his build and it's our job to give him the best possible and correct information to help him out where he wants it and needs it.

Enough of my rant. I'm off to make a YouTube video.

 

I am with LP if its held with cable ties tightened on the outside (or wire) then you fix on the inside ..much easier to measure on the inside for square etc than around the outside...but as you say everyone to there own

 

On taped seam builds, the most important portion of the seam is the inside corner. This is where most of the strength and stiffness comes from, so these need to be fairly solid before doing much moving around. This said, all tape seam builds will be very floppy, until the structure is in. This usually means considerably more then a few temporary molds or bulkheads. You can move the boat (roll it, what ever), just remembering you'll have to "square" her up again. This usually means just putting her in an accurate cradle or some braces to remove twist until the seat boxes, bilge partitions, soles and remaining bulkheads are installed and fully tabbed into place against the hull shell. Even then many boats are still floppy, until the decks get installed. Again, no big deal, just be aware that you might have to tweak the hull a tad to get things square. The best choice is to have a set of measurements to check against. Bow height off the floor, transom corners from the floors, diagonal measurements at the transom corners, etc. It's usually pretty easy to see any twists and shove a wedge under a cradle support to lift a wayward corner, before the goo cures.

 

It's like PAR said. I find fastening the seams gives considerable strength but only modest stiffness. Stiffness - especially torsional stiffness - increases greatly when decks, floatation boxes, thwarts etc are added. It's like a shoe box: lid off = floppy: lid on = stiff. I'm not saying build accuracy doesn't count of course, just that a small twist in the incomplete hull requires only a small force to correct, and when the structure is completed it will hold the new shape because it is so much stiffer.

 

This discussion is very helpful, despite the lack of agreement, in refining the method I am using.

I can see merits in upside down and right way up. People have used either method so they both work.

As of today the position is that the canoe is sitting on 3 frames cut, near as I can manage it, to the dimensions provided by the designer. I have checked them for twist and the flat bottom plank of the hull for level side to side and the difference between the middle frame and the outer ones set at 9mm to give the required rocker. The bow and stern have been set up with a plumb line.

Is there anything more I could have done to get the shape accurate with the boat the right way up?

I am reconsidering glass clothing the outside. Talking to someone experienced in stitch and tape he said it was simpler than I had feared. The main issues concerning me, are increased weight, risk of messing it up, the amount of sanding needed and resultant dust. I would be grateful for your opinions.

I was originally going to just tack the chines before turning over for the internal fillets and tape. Once set it should be stronger than using ties, so should not be a problem turning it over. I now think I might as well complete the filleting of the chines at this stage.

The problem of lack of fit near the ends was cured by tucking the tops of the middle plank inside the top planks then taping the top planks into position so a line could be drawn on the middle plank to trim down to. I think the issue is due to the inability of a curtain rail and nails at 305mm centres to create a local reverse curve.
I released the middle plank, (easy to do with adhesive tape) used the surform to trim down to the line and took the opportunity to bevel the chines to let the epoxy in as they are almost butt joints.

I have used copper wire to get the alignment of the ends. It was easier to adjust than adhesive tape.

 

The whole concept of stitch and glue is to reduce the amount of internal framing required. With Kayaks, there is little internal framing in the finished product.

If you build 'right way up' you have to have accurate female moulds to ensure alignment.

To do that, you need the stations dimensions.

I have never come across a Kayak plan that provided female station dimensions (we are not talking dinghies, boats here. )

Please provide name of a single Kayak design or kit that has the female stations provided.