Tillering advice please!

[kbear]

After my last fail at tillering a reflexed bow, I thought I would get some advice from the guys in the know. I really want this bow to be a shooter.

Specs:

Queensland Silver Ash (Flindersia Bourjotiana) I have used this wood before to some degree of success.
1/4 sawn very straight grain, no imperfections (QSA is diffuse porous)
70" TtT
Asymmetric; bottom limb 1" shorter than the top
1 3/4" Wide at fades, and for half the limb length, tapering to meet a pyramid profile at 2/3 length, to 7/16 at tips
Trapped
Heat treated at 1/2" thickness
Rawhide Backed
2" Reflex
MC around 9%: It has been around 50% RH for the last couple months and averaging around 26°C(80°F) ish of late.

Aiming for 40#

Profile by korey Aitkenhead, on Flickr

This picture really exaggerates the asymmetry.

Bout 2" reflex by korey Aitkenhead, on Flickr

The reflex.....

Limb profile by korey Aitkenhead, on Flickr

Limb profile.....

Trapped n backed by korey Aitkenhead, on Flickr

Trap and back......

Heat treated by korey Aitkenhead, on Flickr

Heat treated........ I apply pine resin dissolved in gum turpentine during the heat treat, and keep the gun moving. This ensures an even treatment. I have run my cabinet scraper over each limb so that the concave can be clearly seen.

Quite warm today by korey Aitkenhead, on Flickr

It's hot in the workshop today. Probably wait til tonight, or tomorrow to start..... supposed to be cooler.

My aim was to give it a circular tiller out of the fades, with the end 7-8" stiff, kind of Holmegaard meets Mollegabet (I do not wish to spark any debates here, since I see the two names are often used interchangeably)

What are your processes/techniques when tillering a bow with reflex?

Any advice on any aspect of the bow is much appreciated.

[kbear]

Wow.... those images really came out larger than expected. Click on each for the full image......

[willie]

Korey

nice design, and some clean wood.Almost reminds me of birch here in the US, diffuse porous. seems like 70" gives you plenty to work with. after reading about your chrysals with the last bow, I wonder if you might be wanting to do something like badgers no set tillering? in order to stay ahead of the set/chrysal potential? you have the option to get the tips bending more before reaching full draw, if it seems you are working the wood too hard .

[kbear]

Thanks Willie. Good advice. That is where I failed last time. I will definitely be focusing on getting the outer limbs bending and developing an even curve. Something that eluded me in my impatience.

So normally I will exercise the bow and look at it from a distance on my tiller tree. Depending on the bend, I will transfer it to the tiller stick at a height where stiff spots may have been noted, clamp it back down on my bench, and use a gizmo to mark stiff spots. I also compare limb height from the bench. I then remove it from the tiller stick, clamp it to the bench top, back down, and remove the marks with scraper or file, before then repeating the process.

Can I use this same method for tillering a reflexed bow? Perhaps I should clamp it on top of a block to preserve the reflex?

I think I just answered my own question.......

[Hamish]

 Stave looks good.  I reckon most of the American guys would give up bowmaking  if they had to use commonly available native Australian trees. You guys have no idea how fortunate you are for good bow wood. Some of our timbers chrysal if you look at them harshly.
Always keep an eye out how much set one limb takes compared with the other.
Remember if you start to get chrysals don't worry its probably the wood and not you.

[bjrogg]

Koreybare, I'm certainly not a expert. Far better bowyers than me on here. I've made a few reflex and static recurved tip bows. To me if it a even gradual reflex the biggest difference is that when I first started making them I was fooled into thinking they were heavier draw weight than they really where. The reflex gives them more string tension and make them feel heavy as soon as you begin your draw. It's also tricky to get them braced. Also if you have reflex in one area and not in another you have to remember that when tilering. In the area with the reflex the bend will look like it isn't bending when it really is. It's easy to remove to much wood a develope a hinge. Watch to see if the wood is bending. Use your fingers like calipers to feel the thickness of the limbs. Sometimes I make short straight lines on edge of limbs where reflexed to make my eyes happy. I can look at the line as I bend the bow.
Good Luck down under.
Bjrogg

[kbear]

Thanks BJ. That's gonna be the tricky part. A reflexed limb that is straight is actually bending! Thankfully the reflex on these bows is more or less consistent throughout the length of the limbs........