I have let the sinew on my first crossbow prod dry for 5 months now and have started tillering my prod. Thanks to everyone on my first post. I went for dimensions based on what you guys were saying and so far so good. A few questions. This is my first go at this so can't expect perfection. I have a youtube link here showing where I am at right now minus a few mm.
Bareing in mind I have a loading mechanism that is able to draw 700lbs to a 12 inch draw I would like to see if i can keep the power on the prod as high as I can.
So far I have the following dimensions and weight in my tillering process.
The prod has 3 layers of sinew with animal glue.
My prod is:
knock to knock 775mm (30.5")
width -46mm at the centre tapering to 38 at the tips
Thickness is varying at the moment based on what I am seeing is bending but roughly speaking the centre is 25.5 tapering to 20 mm with the thinest part being 19.5
So far I have a draw length from it being unstrung (brace height not included) of only 4.5 inches. At this length the draw weight is 220lbs.
I am aiming to achive a brace height of 3" - 76mm and a draw length of 8" - 203mm
My questions regarding how I proceed.
It was suggested in my first post that 18 mm at the tips tapering up 1 mm every inch to the centre would give me 220 lbs at an 8 inch draw. My concern is that if I proceed to this thickness I will start getting into the sap wood on the side of the yew as the back of my bow is quite arched. see video. Is this a problem?
I have one central knot in the middle of the prod and dealt with this on the back by layering extra sinew and leaving more sap wood around. Is it safe to go straight through it on the front of the bow? currently it is flat and in line with the limbs but should I leave more wood around it as I take more heart wood off?
The rest of the process i am relatively familiar with as I have watched many tutorials. I am taking my time and watching to see where I might be over stressing any parts.
So far During the tillering process there was a audible crack but we thought it might have been a bit of sinew as the wood was in tact and when we drew it even further no more cracks were heard. Is this normal?