Tillering 101

July 31, 2005

This page shows how I get a bow from the floor tiller stage to final tiller. I use a faceted tillering technique that was taught to me by Dean Torges and his book "Hunting the Osage Bow" (HOB). I highly recommend this book. It is only around $20 and is great reading as well as the best way to get from a tree standing in the field to a beautifully tillered and finished hunting bow. It can be purchased at Dean's website "The Bowyer's Edge"

This bow is being made for Dan Frein for an elk hunt this fall. He wanted something in the 60# at 27" range. I make my bows slightly longer than Dean recommends but other than that, pretty much like he prescribes. This one is 65" nock to nock and a 1-7/16" wide at its widest.

I almost always get my bows to floor tiller and then use a heatgun and caul to correct side to side deviations and also induce about 1-1/2" of reflex in the profile. This must be done on dry wood or it will check. If you are correcting wet wood, it is best to use steam and the technique Dean lays out in HOB. The heat gun technique was taught to me by Gary Davis at the first MOJam. Gary is as liable or creditable as Dean for starting a bunch of aspiring bowyers out.

<>Here is the first picture.

A beautiful piece of Indiana osage properly shaped in profile and ready to become a bow. A critical lesson I have learned from Dean and others in making bows and practically anything in life is that a good creation is laid upon a good foundation. Diligently following steps and building excellence on excellence is the best way to achieve the best. Sure, shortcuts and patches abound and allow us to tailor our creations, and creating, to our lifestyles but don't expect the best if you can't or aren't willing to put the best into it.

I like to begin tillering with a long string that has leather boots attached to the ends. Floor tiller only reveals so much to me and I've found if I can get a bow bending to around 16" before putting a short string on it, I'm typically happier with the outcome.

Here's a close-up of the boot.

The first pull to about 10" or so. I judge the weight pretty subjectively to about 50# here. I've made a few dozen bows and can guage it pretty closely. Some folks hang a scale on the string to get closer. It isn't critical to hit a specific weight as long as you aren't pulling more than 10# below your target with the long string. There is no reason to overstress your bow at this time. We are just trying to make sure the limbs are about even and there are no stiff spots or hinges before we get her on the short string. This one looks OK but I am going to correct a couple things.
First, the left limb is a bit stronger than the right.
Secondly, the left limb is hardly bending mid limb.
It is useful to divide the limbs in thirds; inner, middle, and outer. As long as no hinges or really stiff spots appear, you can work those areas and approximate a nice round tiller at this point. The bow is aweful heavy yet so I will adjust the weight too.

I start by rasping 10 strokes in the middle third on the left limb. This is pretty agressive and if you are new, use only a scraper from here on out. Dean's method calls for adjusting weight on the side facet and tiller on the top facet. I kind of combine those at this early stage. Don't dish your rasp or put a lot of pressure on your scraper. Incremental and predictable amounts of wood removal are the key. I count my rasp strokes and my scrapes. Usually 10 at a time unless I have a lot of work to do.

I also give both limbs 10 full length rasp strokes on each side facet to lower the weight a bit. I give the top facet maybe 5 strokes just to knock off the peak a bit.

OK, the bow is a little lighter so I pulled it a couple inches farther. It's about 50# or so at that point. The left limb is bending a little now. The right limb looks pretty good.
I still need to adjust the middle third on the left some. I use the scraper from here on out since I'm getting closer on weight. She's still heavy so I'll repeat the process from aboveexcept using a scraper instead of a rasp, 10 scrapes middle third on the left and 10 full length scrapes on both limbs.

I always exercise the bow between scraping sessions by bending to weight 30 times. I'm up to 12" or so and she's coming around. 10 more full length scrapes.

It's really important to use a sharp scraper to get predictable and effective wood removal. Here's a nice pile of scraper curls from my Sandvik scraper. Here's how to do it.

I'm now pulling it about 14" and getting around 50#. Tiller is getting more round but that middle third on the left is still a bit stiff. I'll touch that place 10 more times and 10 times full length on both sides and we'll see where we are.

She's really about as close as we need her before we brace her up. No hinges, no serious flat spots, limbs are fairly even. The upper limb is on hte left here. It is longer and I will finish with about 1/4" positive tiller so it's OK that it is bending a bit more than the left. I think she's ready for a short string.

OK I got her braced to about 3". Looks OK

And here she is pulled to about 20".

She's pulling 50 pounds at that draw length. I got some correcting to do. The right limb is stiffer than the left and has a weak spot at the junction between middle third and outer third. The left limb is stiff midlimb.

August 1, 2005

Back at it. It's nice to see a bow that is close to tiller at brace height. You can tell by this pic at about 5" brace that she is positive tiller (upper limb on left has more space between the string and the belly) by about 1/2". I like it to be more like a quarter inch and the last drawn pic shows that the right (lower) limb is too strong.

Based on the last drawn photo, she needs a little work from the handle to the weak spot on the right and just a touch midlimb on the left. I gave here a good 15 scrapes on all facets on the right and about 5 on just the top facet on the left at those spots
.

Here's what we got. Left limb looks nice except at the tip which I always work last. Still just a bit stiff midlimb. Right limb still has that weak spot. This is drawn to 21" which is about 50# now. I'm going to hit just the top facet on the right limb from the handle to that weak spot 10 times.

Bending just a bit more there now. She's drawn to 21" and weighs about 48# there. I drew her to 60# since ther really is no danger in damaging the bow now. She weighed 60# at 25". That's close to go time. I like a bow to weigh target weight at 1" less than target draw so I have some wiggle room for tiller adjustments and finsh and shooting in. THis will be fine. We'll nail weight and tiller is real close. I'm going to finesse the tiller from here on out. A few scrapes on the top from the handle to the midlimb on the right.

Here she is drawn to 24". Tiller is coming around. She's slightly positive and I still have a full 2 inches to finesse tiller and shoot her in. Still weighing 60# at 25". You gotta like that string angle. That's why I like a slightly longer bow. They just seem to draw more smoothly. I might do a force draw curve just to see how she stacks up. I still have to work the tips. They will stay fairly stiff but I'll take the bend out a couple more inches from where it is now. I'll also narrow them to reduce mass. I like to leave them wide so I can move the string in the handle if need be.
You'll also notice that I leave the handle full width too for that same reason.

I can lay a weighted string across the tips and really make sure she lines up nice.

This one is so close it really isn't necessary but sometimes you can shape your handle to make sure the string lies in the center.

The mark is where the string lies now. I didn't want the handle to look real weird so I'll take the string the rest of the way to center using the tip narrowing I'll do later.
I got a littl ebusy to take too many pics. Tiller finished up nice. Here's the finished pics with a set of prairie rattlers and some Mother Earth Brown dye from Larry Maggard.