Laminating wood? It’s not that difficult!
I have frequently been asked about how to make something by laminating wood. A simple thing like making a new tiller is one question that often crops up, or sometimes other bigger curved timber structures, particularly with reference to the curves that are commonly associated with boats. After all, there are very few straight lines in their construction.
People often feel intimidated and think the task may be beyond their capabilities. For most people with a reasonable level of handicraft skill, nothing could be further from the truth. Laminating is actually quite an easy task, although rather a messy one. The key as with most things is the preparation.
Let’s look at some of the reasons for laminating timber:-
- Laminating is a tried and tested construction method in wood that has been around for many years. Modern glues have made the joints on laminated timber virtually foolproof. The best of these glues are stronger than the wood itself. A classic example of laminating that everyone will be familiar with is plywood, in particular marine plywood.
- . It’s a method that allows the construction of curved (or flat) timbers to be carried out economically. For example, a plank of wood cut into strips and used to laminate the stem of a wooden boat uses far less timber than a stem cut from solid sections as seen on the older traditional methods of wooden boat construction.
- Much of the stress is taken out of the timber by laminating compared to a non-laminated curved section. This reduces the likelihood of structural failure, a big consideration to bear in mind. Photo 1 shows the author clamping the gunwales of a Drascombe Lugger which is made from two laminates.
- There is no need for steaming to bend the timber to shape. As a general rule, modern adhesives mostly require kiln dried timber to be completely successful.
- Quite complex curves, even multiple curves that retain their shape, are possible to construct with relative ease.
- Laminating wood can look very attractive if contrasting timbers are used and the finished item varnished to show them. For example, using ash, which is a pale whitish yellow/brown, against the reddish/brown of mahogany. Of course, if only one type of timber is used it can almost look like one solid piece of wood, particularly if clear adhesives, such as epoxy resin, are used.
- Laminated sections are stronger than a similar size section of solid timber. Thin laminates can accommodate very tight curves that can be manufactured with relative ease. Thicker laminates are more suited to gentler curves
- The extra strength of laminated sections can in some instances allow for a slightly less heavy and bulky section of wood to be used. This can be a considerable benefit where less weight is an important consideration.
So we have at least eight good reasons to consider the use of laminating when building with timber. Now let’s look at the method that is, probably, of most general interest. This method requires the construction of a simple jig or former to hold the laminates to the required shape while the glue cures. It can be used to make such items as a curved tiller.
- First you need to determine what type of wood, hardwood or softwood? Also the thickness of the laminates you will use. The thinner the laminates, the easier they are to bend and the less likelihood of ‘spring back’ occurring. With thinner laminates more glue is used and of course more laminates. With thicker laminates there is almost certain to be a bit of ‘spring back’ where the wood tries to return to its original straight nature. Because of this it is advisable to add just a little extra to the curve when constructing the jig or former. It’s difficult to predict exactly how much to add but a little common sense usually suffices to aid the guesswork. Flexing the laminates by hand might help you to determine the amount. For something like a curved tiller made from hardwood, laminates of approximately 6mm in thickness would be quite suitable. Typically this size of wood will need about 6mm added to the curve to allow for ‘spring back’ but it’s not a precise science. If an exact curve is required, unless you have the experience to judge the extra curve needed, using thinner laminates would be a better option to ensure success. Thinner laminates and more glue will add to the materials cost which might be something you need to consider.
- Let’s assume we are making a jig for a tiller with a couple of curves in it to clear an outboard motor, similar to the set up for a Scaith, Peterboat or Scaffie. (See photo 2)We would need laminates a bit longer than the required finished length and of course slightly bigger/wider overall to allow for finishing to the final size. So add at least 100mm to the overall length. Make sure you also allow the length to follow the curves, don’t just measure a straight line length. Use a piece of stiff cardboard or hardboard to make a template to get the correct shape or profile desired.
- Using the template as a guide, mark the shape of the curves onto a suitable size of flat board.
- Chipboard, plywood or MDF are suitable for the base board of the jig, but must be thick enough and stiff enough to remain flat when the laminates and cramps are in place. At least 12mm or more in thickness would be adequate.
- (Advisory: Do not use the kitchen work top, it will not make you popular in your house!)
- When you have transferred the shape from the template to the base board, remember to add the little extra to allow for ‘spring back’ if needed and adjust the marking of the curves accordingly.
- The next stage is to cut some blocks of wood to fasten to the base board. These blocks will act as a spine or backbone that the laminates will be cramped to. The blocks should be substantial enough to take the pressure of the cramps and the bend of the laminates. In this instance, blocks of approximately 50mm (H) x 50mm (W) x 60mm (L) would be adequate enough. They must be spaced 50mm apart if using 6mm laminates (closer if using thinner laminates) accurately following the curved line marked on the base board. The blocks must be firmly and securely fastened to the base board. Screwed and glued would be best. If they moved or broke away during the laminating process, it would spell disaster and be a costly mistake. The blocks and the base board must be covered in masking tape or plastic sheet to prevent the laminates adhering to the jig.
- With the jig assembled, the next step is to prepare the laminates. Assuming the laminates have been cut to size, each surface to be glued must be roughened to give a good mechanical key for the adhesive. If they are sawn surfaces they may well be adequate as they are but if they are smooth surfaces, such as a planed surface, they will need to be abraded with coarse sandpaper (60grit) on all the mating surfaces between the laminates. Another good method for providing a mechanical key to a surface prior to gluing is to drag the teeth of a tenon saw across the grain at 45 degrees to create a cross hatched pattern.
- When this has been done the adhesive must be applied to all of these roughened surfaces (not just one side). It is advisable to wear disposable gloves. The best way to apply the glue is to start with the first two laminates laid on a flat surface. Then, when the mating surfaces are well coated in adhesive, put one on top of the other, repeating this process to end up with a ‘sandwich’ of laminates. The ‘sandwich’ will be quite slippery so handle with care.
- It should now be turned on its side and placed against the blocks on the jig and one of the cramps near the centre of the jig applied first to hold them in place. Continue to apply more cramps to squeeze the laminates together by each block, working alternately to right of centre then left of centre. (See diagram 3)Sometimes it might be easier to work the cramps from one end only rather than start from the centre. It will depend upon the curved shape you are creating and will be a fairly obvious decision to make. When all the cramps are in place, you must check to make sure the laminates haven’t lifted up from the base board and also that the cramps are all fully tightened. It’s wise to go over the cramps a few times to make certain of this and, by now, you will have realised why you needed the gloves.
- When all has been completed and the glue has fully cured you can remove the cramps and release the tiller from the jig. All that remains to do now is clean up and shape the tiller to the finished article. This may seem a bit of a drawn out and complicated process but it really is not and you will have the satisfaction of knowing you have constructed something beautiful which will give you a lot of satisfaction. For all types of laminating, especially marine use, I personally prefer phenolic resin glues. Some people prefer epoxy resin which is also very satisfactory. What these adhesives have in common is their strength. Both types of adhesive will give joints that are stronger than the wood itself when used correctly. This should include ensuring the ambient temperature is controlled during extremes of weather.