Grahame's work helped me to refine the core lamination thickness and the required degree of taper. The back and belly laminations were not an issue as they could be modified during the tillering process. I did however run a taper from mid limb to the tips on the back lamination.
The American ash lamination [almost vertical grain] which was to be the back of the bow was a little "banana shaped" in the plan view so a string line was used to mark a true center line. The plan of the bow was marked out according to the center line.
When gluing up all wood laminated bows never force the laminations to a straight line as they will want to go back to their memory when you shape the bow to the laid out plan. As a side note bamboo can fight even harder to get back to its original state.
I do not need to go into the detail of preparing the laminations etc as Grahame did an excellent job with his commentary and photos in his “Not Rocket Science" post.
The bow that I am building has equal length limbs which will require a little more effort in the tillering department. If push comes to shove I can modify the little bump in the handle area to lengthen a limb.
The halfway length of the stave, 36"] was marked and 4" either side of this mark would approximate the handle section. The limbs were then marked out in 6" increments.
Although I knew the back and belly laminations were over the required thickness it left various options open for tillering and poundage adjustments.
Unlike selfbows made from bush billets where the back of the bow is left intact or worked down to a satisfactory growth ring the growth rings have already been violated in bows made from milled timber.
After shaping the plan of the bow on a hi-speed belt sander I was able to mark out the belly profile of the stave. After some work on the belly using a sharp spokeshave [thanks Grahame] I could start to floor tiller the stave. After removing what seemed like half a log from the belly the stave it would hardly bend. After awhile the penny dropped, I was dealing with a laminated stave with built in reflex and not a bush billet.
During the stages of removing wood from the belly the verniers were used at the markings to ensure wood was removed equally from each limb. At this early stage plus or minus the thickness of a sheet of paper was close enough. Between each spoke shaving session I would sandpaper the belly to true up the "D" profile. Having removed as much wood as I dare from the belly I suspected that the back was too strong.
A quick session on the tiller board confirmed my thoughts. The handle to just past the mid limb section was too stiff. I also had to take into account the amount of reflex built in from mid limb to the tips.
After spoke shaving and sanding the back of the bow the verniers were used to check the uniformity of the limbs.
The photo illustrates the tiller of the bow using the verniers to arrive at this point. The tiller is marginally out but I will make the adjustments on the braced bow.
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In hindsight [which is a wonderful thing] I would opt for the tips of the horn rather than a slab.
The photos will illustrate the various steps.
Step 1; mark out the section of horn to be used and the position for the pilot hole. A 1/8" drill bit is a good size. As the top nock was to have a second groove for a looped bow stringer I made it a little deeper. I used a drill press which allows you to set the drill depth.
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Although the tiller has moved a little it will be adjusted as the bow settles into full draw. I am happy with the belly of the bow so all adjustments will be made to the back of the bow. When the bow has settled in it will get a final cleanup/sanding and a good rubbing with bees wax.
Tiller boards can be a useful tool but I prefer to do final tillering on a braced bow rather than chasing it all over the tiller board.
Suitable timber and accurate measurements can save you a lot of trips to the tiller board.
Laminated wood bows can be made with basic tools and cost less than taking the family to a fast food outlet.
After a busy day I like to relax with a home brew or two.
Daryl.
But there have been other lessons - eg you can make bows "by eye" which appeals to artist in me and you can "engineer" bows using careful measurement and in both cases end up with a great bow.