Tillering a glass bow....?????

[skeaterbait]

Howdy all. I am getting setup to build my first glass bow and have been doing a fair bit of reading.  So far, my understanding is that if you can tiller a selfbow that building a glass bow should be a cake walk. I am very anxious to discover this, however, I can't seem to find any information on HOW to tiller a glass bow.

Does anyone have a build along for a glass bow that encompasses the actual tillering. I find tons of them that cover making the riser, laying out, gluing up and even on the tiller tree, but no one describes the tiller.

I would assume that it will be like an pyramid selfbow where the thickness is determined and achieved then the tiller is done by taking down the sides of the limbs?

[JamesV]

PM sent

[KenH]

Basically the tillering for draw weight that you do on a wood bow by sanding/shaving off limb thickness; is done in a wood-fiberglass bow by selecting the right thickness of wood and fiberglass lamination.  And that depends a great deal on the design of the bow you want to build.  

Basic concept is that the fiberglass provides 88% of the strength of the bow.  That said, the actual thickness of the two glass lams isn't as important in determining draw weight as is the total overall thickness of wood and glass.  

In other words .03 vs .04 vs .05 glass lams doesn't matter as much as a total lamination thickness of say .28". You can get that .38 by several combinations of wood and glass lam thicknesses such as 2x .04 glass plus 3x .07 wood lams.  Or 2 x .05 glass plus 2 x .07 wood. Or 2 x .03 glass plus 3 x .09 wood, etc.

[jsweka]

Ken's right, most of your tillering is "engineered" into the bow.

However, there may be some cases where you do have to do some.  If you do need to do some tillering, sand the edges of the limbs in the areas where the limb is a little stiff to narrow it a bit.

Some folks will sand a little bit on the glass.  I just don't like that idea.

[Robertfishes]

I check each lamination thickness and make sure they match in each limb. I like to draw a centerline on the back glass, then draw a line across belly glass every inch from center to tip, then draw limb profile lines..I number each mark from center, after glue up I sand excess glue from edges and using a string I make sure center line is still straight down the center..after sanding limb edges close to line on my edge sander, I check limb widths at every other inch mark, I make sure limbs are same width from center of bow and at each corrosponding number on other limb.I am always within 1/8" or less when I string and check tiller. There may be a better way but this is my way.  

[Robertfishes]

I tried the yellow frog tape, it is the best Ive used  and comes off soooo easy. But I had trouble seeing my lines, I fixed that by putting cheap white masking tape over the yellow or green frog tape . both pull off the same time with no problems.Here is a handfull of longbows I prepped for a mass glue up,,I started the double taping after this. as far as tillering I use a tillering stick and trace limbs onto a piece of butchers paper then flip over trace and compare, not sure if this is a good way to tiller but its what Im doing. If any adjustment is needed I lightly sand limb edges..        

[skeaterbait]

Thank you all for the replies and James for the PM, every one is helpful and gives me a bit more confidence going in to this.