Laminated tiller or not?

[gone2ddogs]

I am planning on making a new tiller to replace the wheel steering om my Triton. My plan was to laminate 2 pieces of mahogany with a piece of maple in the middle to make up the thickness I would need to fit the tiller head then band saw the profile and shape. I just happened to have some 1x material left over to make this with. My question is would a 3 piece lamination in the vertical plane be strong enough? The old stump in my tiller head is on solid piece, but I see a lot of tillers made from many thin laminations in the horizontal plane. I would hate to be tooling along at 6kn to have my new tiller snap off in my hands. My thoughts are that to make the tiller of thin horizontal laminations I would need to cut them from the edge of some 2" or thicker material.

Thanks
John
Triton Yawl #15

[Hirilondë]

There are 2 advantages to laminating. One is that it is stronger, and the other is that it is more stable, hence less likely to change shape. The tendency to change shape is increased when you cut wood on a curve as you create run out of the grain which releases strange loads within the wood. This run out also weakens the resulting piece. The strongest solution is to laminate many thin pieces to the general curve you are looking for (laminating to a mold), then mill to the final shape. This would mean laminating horizontally. Many thin layers captures any grain run out of all layers except the outside ones, bends the grain to the shape instead of cutting across it, is extremely stable, and is much more resistant to torsion loads which is what broke your last tiller.

[Quetzalsailor]

Another way to see what Dave is saying about 'stronger' is that care with laminations tends to disperse faults in the wood, such as the grain runout. Thus, the laminated part will not be as strong as a perfect example of the wood (unless the veneers are themselves perfect) but it will be much stronger than less than perfect examples of the wood. This is the whole idea behind 'Microlam' beams which are basically laminated of wood veneer of the same species as the timber beam you might have chosen. Since the defects are dispersed, that is splits and knots no longer extend through the piece, the resulting timber is quite good and effectively cheaper since a poorer grade of wood made into veneer gives results better than the run of solid timbers.

The trick is to use and choose an assembly of veneers that disperses the runout or whatever defect you note. People like Thomas Moser, who build wonderful furniture, often laminate the curved components. Since they don't want to see the laminations, they slice a piece of wood and then laminate it back together in the same order it grew in. The grain crosses the laminations and you can hardly see 'em. (From the Moser website: Our signature piece, the Continuous Arm Chair, remains a unique, trademarked Moser design. To form the arms eleven knife-cut slices of the same board just one-tenth of an inch thick, called flitch, are laminated together. Then each continuous arm is painstakingly rasped, filed and sanded to a perfect smoothness.)

Depending on the curvature, you could steam a very nice piece of wood and not laminate at all.

[Ric in Richmond]

DIY BOAT says 5 layers.

http://www.diy-boat.com/content/view/180/36/

Tiller 4/29/96
GETTING STARTED
The shop-tested projects detailed in the WINTER ISSUE have been grouped together in five categories: canvas, woodworking, King StarBoard, laminating techniques and fiberglass. Some of the projects apply only to powerboats; others are only for sailboats. Our instructions assume that you have mastered basic skills and techniques.

Once you've selected a project, you need to plan and organize everything carefully. This involves a number of steps: develop a materials list; purchase materials; make the necessary patterns; cut and assemble; and install.

You'll need to consider the suitability of a particular project, quality, durability and cost. Make a list of materials, tools everything you require before you start. For some projects, you'll have a choice of materials, color and design. After deciding what materials to use, determine how much you'll need. If you can afford it, purchase a little extra. (Remember the last time you got partway through a job and discovered you didn't have enough material to complete it?)

There are several methods for making patterns and care should be taken to avoid mistakes, because they can be costly: measure twice (or three or four times) and cut once. Pattern making is somewhat of an art and frequently means the difference between a sloppy and professional-looking result. Make notes: don't trust anything to memory. Take your time and do it right.

After you have checked measurements and patterns carefully, transfer cutting lines and all necessary marks from the pattern to the material, arranging the pattern to keep waste to a minimum. After a final check of the marked lines, you're ready for cutting and assembly.

Although we have given the most common method for doing these projects, our ways are not the only ones. You may come up with a better method for your particular purposes. This is the creative part of doing it yourself!

LAMINATING TECHNIQUES -- BUILD A TILLER

For a few dollars and a bit of elbow grease, you can easily produce wooden components such as hatch frames, deck beams, bunk boards, a dinghy rudder, tiller, frames for a dodger and boom gallows. Multiple strips of hardwood, laminated with epoxy glue, are bent to shape in a custom form. Layers of wood and glue, much like plywood, make an extremely strong part, certainly much stronger than one made of solid wood.

Laminated wood and epoxy components will withstand most forces, except maybe an old willow tree that crash-lands during winter storage, which is exactly what prompted me to build a replacement tiller. The following assembly instructions are for a laminated tiller, but can be easily adapted to any woodworking project.

To make the tiller, you'll need five strips of hardwood, such as oak or mahogany, cut to the desired length and milled to a thickness of 12mm (1/2"). Working with wood that is ripped and milled to a finished size saves a lot of time and labor.

Make a pattern using the old tiller or customize a new shape; either way, you need to make a laminating form. Draw an outline of the desired shape onto a piece of heavy plywood. Cover with heavy, clear plastic or wax paper to prevent the glue from sticking to the wood. Fabricate seven or more square blocks from scrap wood 3.8cm (1-1/2") thick, and screw or nail them securely along the outside perimeter of the line drawn on the plywood.

Lay the hardwood strips face down and apply epoxy glue, thickened to the consistency of mayonnaise (see page 31 for mixing details), to one side (Figure A). Stack the pieces and tape the middle and ends to hold them in place (Figure B). It's a good idea at this stage to wrap the bundle in plastic or wax paper. This prevents bonding of the stock to the laminating form. Turn the bundle on its side, lay it on the laminating form and clamp it with C-clamps to the blocks, beginning with the center block and working out to each side. Attach additional C-clamps directly to the wood bundle to provide extra pressure (Figure C). Place scraps of wood or cardboard between the clamps and the stock to protect the wood from the clamps' jaws. Remove excess epoxy with a putty knife, then wipe with a clean rag. Let the glue dry, remove the clamps, then scrape or sand off any excess epoxy. Use a belt sander or hand tool, such as a jack plane, spoke shave or block plane, to form the desired shape.



Now drill a hole for the tiller bolt, give the tiller a final sanding with 120-grit paper and apply three or four coats of epoxy to waterproof the wood, followed by seven to 10 coats of marine varnish that's compatible with epoxy. (TIP: Thread a piece of string through the bolt hole and suspend the tiller from the ceiling when coating.)

Attach stainless straps on the sides to provide lateral support for the tiller and prevent it from breaking at the rudder head (Figure D). Make a paper pattern of the finished profile of the tiller from the outboard end extending about 30cm (12") forward. Radius the forward edge and mark hole placements for the tiller bolt and a 1/4" bolt at the forward edge. Have a metal shop fabricate two 4mm- (3/16") thick stainless-steel pieces from your pattern. Thru-bolt these to the tiller with hex bolts and cap (or acorn) nuts, making sure to line up all outboard edges.

While you have everything set up, consider making a second tiller. You never know when you might need a spare.