Correcting Bad Tiller

I was tempted to call this post "A Tillering Tutorial", but thought that sounded pretentious. The point of it is to show that we all have problems and that a methodical approach will get it sorted.

Target weight/draw length 40# at 28"
The bow is made of spliced billets which can sometimes give a slight miss match to the way the limbs behave if the wood is from two different staves.
To cut to the chase, I've got it at a low brace and pulling to 40# at about 19" or so. Always pull to full draw weight as long as the tiller looks ok.... errr.
I got a shock, the tiller looks hideous, but let's not panic, let's look at it dispassionately as there are several things going on, all of which all work together to make it look awful.
1. There is a slight downward bend in the lower (left) limb just left of the grip.
2. There is a slightly weak point in the left limb at the bend mentioned above.
3. The right limb is stiff.
4. I had it sitting on the tiller slightly too far to the right and was pulling the string a little too far off centre.

I check the simple things first, I re-position it on the tiller and even try it round the other way. It still looks bad. I also unstring it and look at how much of that bend is in the stave (probably a couple of inches).
First fix, I use heat  to remove that bend (15 minutes with a hot air gun and the bow strapped up).
Ah, it looks great unstrung, but still ugly as sin on the tiller.

I take some off the right limb with a rasp, but it doesn't make any difference... it just doesn't seem to want to bend any more. It does have some stiff areas where there are knots, but I want to get some method into the panic.

I compare the thickness of the right and left limbs where that bend is (about 6" from the centre line) using my verniers as a go/no go gauge rather than an actual measurement.
Ah, the stiff right limb is indeed thicker! (despite looking generally thinner, maybe it's just colour variation or heartwood/sapwood difference)
I rasp that area of the right limb until the verniers will just slip over it.
That gives some sort of reference point at the start of the limb. From there I can slide the verniers along the limb, and of course it should become loose as the limb gets thinner. It soon jams on a thick part where there is a knot. Now conventional wisdom tells you to leave some extra at a knot, but how much? I know I have plenty of draw weight still to play with, so if I rasp it down until the verniers only just fit over it, that will still be a little thicker than it should be, (because the limb should have tapered a bit by then). I then check just beyond the knot and the verniers rattle loosely at that point, so I adjust them to be snug and slide them along the limb some more.

I do this along the limb to check that the knots aren't too thick and that there is a gradual taper all along. By the time I've finished I've taken off a good deal of wood with the rasp. I've also taken care to look at the limb from both sides as it's easy to work at an angle giving an uneven thickness across the limb. Having taken some off the belly, the corners where sides meet belly are now a bit sharp, so I rasp these corners off.
Back on the tiller ... groan... the right limb is still stiff... will it never bend. I take the bow in my hand and draw it rapidly back and forth about 20 times, and then decide to try it the other way round with the stiff right (upper) limb as the lower instead.
I re-measure the centre of the bow, mark the new arrow pass 1" above the centre line and put it up on the tiller.
Much better...
Quit while I'm ahead, and decide that writing this up will be a useful post for everyone getting frustrated with limbs that won't bend!

Now I've taken more pics and you can see the improvement.
The main point is that in correcting the tiller the draw has now increased from about 20" to 24", the tiller isn't perfect yet, but it's well on it's way to decent tiller and 28" draw.
Hopefully this shows why you need to get the tiller sorted early.
It's ready for horn nocks now, which will involve tapering the outer limbs too and should get them coming round more.
Youtube video here:-
https://youtu.be/kWaO9K4yko8

I see someone has ticked the "explain more" box. I don't really know what specifically explain. Maybe it's the FAQ about why I have the bow tilting to the right and why reversing the bow on the tiller can make a difference?
To explain briefly, the bow is held at some point roughly in the middle, but the arrow sits above that and the string is pulled in line with the arrow. So the whole thing isn't symmetrical! This doesn't make too much difference on a long bow, but can be very significant on a short bow. If you clamp a bow dead centre, pull the string from dead centre and tiller it like that, when it is held in the hand and shot, the tiller will look slightly off.