I just got in from tillering the bow. It is completely tillered now. I took pictures as I went along and wrote down the draw weight and length as I went along so I wouldn't forget which description goes with which pictures. But there is something I forgot. At various stages, I would notice flat spots or some other little thing I wanted to adjust, and now I can't remember it all. I'm going to have to make some guesses, so bear with me.
Yesterday (yes, page 8 turned out to be tomorrow after all), we braced the bow kind of low. Maybe it was 3". Now what I wanted to do is draw the bow out some more and eventually brace it higher. Since I braced the bow after 10" of limb travel, I was curious to know what 10" of limb travel would give me now that the bow is braced. Since the string comes to 3", I pulled it to 13" and got 20#.
And then since I braced it when it was 30#, I wanted to see how far I had to draw it to get to 30#. I ended up drawing it to 17".
I don't remember when it was, but at some point, I noticed a couple of flat spots on the right limb. Now lemme explain how I found them. You see, these flat spots were imperceptible to the naked eye. Instead, I took a short little block of wood about 4" long and slid it along the belly of the bow.
Do you see that little gap between the black curve and the red block? Well, just slide the block down the limb. If the gap gets bigger then smaller again, that means you found a hinge. If it gets smaller then bigger again, that means you found a flat spot. It's a nifty little trick.
Another nifty idea (Dare I say 'niftier'?) is the tillering gizmo invented by Eric Krewson. It's basically just a block of wood with a pencil through it that marks flat spots when you slide it along the limb, so you'll know where to remove wood. Simple and effective. It only works on straight bows, though. It doesn't work on reflex deflex bows or bows with a lot of character.
Anyway, remember that whenever you find any kind of flaw, you don't want to draw the bow any farther until you've corrected the flaw. From this point on, I go one inch at a time. I wanted to creep up to 40# or around 20", whatever I felt like, and then brace the bow fully. Once I have all perceptible flaws fixed, I take the bow another inch and measure the draw weight. Remember to excercise the limbs every time you remove any wood. At 20", the bow came to 35#.
I don't remember when it was, but at some point, I wanted to start getting the limbs bending closer to the fades. Oh, that reminds me. After I braced the bow, I vowed to leave the tips alone for about 5 or 6 inches. Leaving the tips stiff will allow me to narrow them later if I feel like it. Also, having stiff tips is supposed to help performance. There's debate about that, though. Still, I feel more comfortable with the tips being a bit stiff. If anything, it would have to at least reduce stacking.
Anyway, I finally reached 40# at 22"
Now's a good time to bring it up to a full brace. First, check out the string alignment.
Now bad, eh? Here it is with a full brace.
"Full brace," usually means the distance between the handle and the string is the same as when you put your fist on the handle with your thumb sticking up. But in my case, the brace is just slightly lower than that. Some of us prefer a lower brace. It's supposed to improve cast, but it sometimes increases wrist slap and archer's paradox.
Anyway, I continued pulling on the bow and inching toward my draw weight and draw length and making adjustments as I went. You should go really slow at this point. Remember we're shooting for 45# at 28". Since 45# is my final target weight, though, I'm actually going to try to get there at 27". You see, I figure with all the sanding I'm going to do on the bow, and the fact that it will likely weaken some more as I shoot it, it will lose a little weight. If I get 45# at 27", I'm sure it will eventually be 45# at 28" once it's been shot in.
Here, I've reached 45# at 25".
It's tempting at this point to think, "Well, why not just have a 50# bow instead of a 45# bow? Then I could pull it to 28" and call it quits. To tell you the truth, I was really tempted to do that. I decided I needed to work on my committment issues, though, and since I committed to 45# at 28", I stuck with it.
Before getting it to 27", I wanted to check the tiller. Now's a good time to introduce a new term. You already know the idea. Now you just need to know the word that codifies the idea. The word is "positive tiller." Oh, I know. That's not really a word; it's a phrase. I'll give you that one. But that's neither here nor there. What's important is what it means. A positive tiller is when the top limb bends more than the bottom limb.
There are two popular ways of shooting bows in the Anglo-American world. There's split finger and there's three-under. Split finger is the usual way when you've got your index finger above the arrow, and your middle and ring fingers below the arrow. When you shoot an arrow, the arrow is actually going to rest above the center of the bow. When you draw the string with split fingers, you're pulling above the center of the string. That puts more stress on the bottom limb than on the top. To compensate for that, some people like to have a positive tiller.
When shooting three fingers under, all three fingers are under the arrow. In that case, the fingers are drawing the string closer to the middle. So when people tiller a bow for three fingers under, they try to get both limbs bending perfectly even. There is no positive tiller.
I, and most people, shoot with split fingers. So I try to shoot for the limbs being pretty close to even, but when I get to the end, I measure to see if one limb is bending slightly more than the other. If one limb bends more than the other, I make that the top limb. I measure from the end of the fade to the string on both sides.
If the top limb is has a gap 1/4" bigger than the bottom limb, then you have 1/4" of positive tiller. That is a typical positive tiller for split finger shooting. In this case, though, the limbs came out pretty close. One limb has a gap 1/8" bigger than the other limb, which is fine with me. The limb with the bigger gap will be the top limb.
At this point, we're just reducing weight. I seem to have gotten all the flat spots and hinges out. I don't want to get anymore in while I reduce the weight. So remember to take long steady strokes from the fade to within 5 or 6" of the tips. Count the strokes, repeat the same number on the other side, and don't take off too much wood at a time. Go slow. Do about five strokes, then check it again.
Here it is finally at 46# at 27".
46# is close enough for me. After all, I have serious doubts about the accuracy of my bow scale anyway. What's one pound gonna hurt?
I measured the string follow immediately after unstringing it. I layed the bow on its back and measured how high the tip came up.
1.5" is unusual for me. Usually, I get 2 or 3 inches. 1.5" is really pretty good. I think the reason it came out so well is because I was far more careful tillering this bow than I usually am. Since I'm doing a build-along in front of lots of other people, I didn't want to goof it up, so I was extra careful. It paid off, huh?
Now of course, even though I hit my target weight at 27", I still want to make sure I can pull it to 28" without it breaking. In fact, in a situation like this, I will usually go ahead and pull it to 29". That way, if anybody with a 28" draw ever brings it to 28" and then hick-ups, it won't cause a problem. It gives me a feeling of security knowing the bow is safe to pull an inch farther than I intend for it to be pulled.
That's it for tilling. On page 9, we'll work on the tips and the handle.