What is a heavy chested bow tiller

[Part time Archer]

I read this on a Longbow site that they made their upper limb 4 lbs weaker to help shoot various spines can anyone explain please?

Fisk  Longbow
This produces a bow with a tiller between top and bottom limbs that varies by four pounds. In other words, the top limb pulls four pounds less than the bottom limb. This produces a "heavy chested" longbow. With this design, any of my longbows will shoot a variety of differently spined arrows well, including graphite, carbon, wood and aluminum.

[Badger]

  I don't buy this, spine is spine. The heavy chested tiller would have more effect on the nocking point.

[Del the cat]

Sounds like it's been somewhat embroidered.....
How do you measure the draw weight of an individual limb?
Most bows have a slightly stiffer lower limb... I can picture what they mean by "heavy chested" ( like a bloke standing up puffing his chest out, giving a more rounded top) but I've not heard it used of bows before.
Del

[PatM]

The term used in the past was breasted tiller.  Sounds like he's made up some stuff to make it seem worthwhile.

[Part time Archer]

Thank you both. For the sake of argument , I could imagine the handle in a vise  and not moving . 2 separate strings , not connected , attached to 2 scales against a very detailed tillering board measuring the 4 lb difference. Would be a more standardized way to always ensure bottom limb is timed, or maybe the bottom limb is not over strained , instead of using the old adage of + 1/4 tiller or comstock says 3\8 to 1\2 positive tiller in his book.

[Del the cat]

Thank you both. For the sake of argument , I could imagine the handle in a vise  and not moving . 2 separate strings , not connected , attached to 2 scales against a very detailed tillering board measuring the 4 lb difference. Would be a more standardized way to always ensure bottom limb is timed, or maybe the bottom limb is not over strained , instead of using the old adage of + 1/4 tiller or comstock says 3\8 to 1\2 positive tiller in his book.

Very difficult to pull a single string in the correct direction to match up with how a normal string would draw.
Del

[Part time Archer]

True but with the angles drawn out on a tillering board at a given draw length then sure, but then you take the primitive out of bow building and replace it with standardized measureing techniques. Love to see a primitive archer myth busters style approach in an upcoming issue for fun! And discuss 3\8 to 1\2 positive tiller.different weight bows would be different positive tillers if you trying to achieve 4 lb lighter limb on top!

[Del the cat]

True but with the angles drawn out on a tillering board at a given draw length then sure, but then you take the primitive out of bow building and replace it with standardized measureing techniques. Love to see a primitive archer myth busters style approach in an upcoming issue for fun! And discuss 3\8 to 1\2 positive tiller.different weight bows would be different positive tillers if you trying to achieve 4 lb lighter limb on top!

No, it's bonkers. It would remove a key aspect of the bows design... that it is fundamentally balanced.
To test one limb at a time would necessitate clamping it and introducing unbalanced stresses.
If you think it is in some way a good idea, you need to sit on the naughty step and have a careful think
Del

[Bob Barnes]

If the person that made the claim was making 100+ pound warbows, then 1/4" positive tiller might equate to 4# lighter on the top limb...  but if it was a 20# bow 4# would be ridiculous...

[George Tsoukalas]

Is the term referring to all wooden bows or FG bows?
I never heard of it which doesn't mean much. LOL.
Jawge

[Part time Archer]

  You guys rock. Makes me wonder. But wait the site says , When the bows are tillered, I avoid sanding down the surfaces of the FRP to achieve balance between the top and the bottom limb. The top limb lamination are ground 0.004 of an inch thinner than the bottom. .... Hmm which makes it 4 lbs lighter. So is this just for the average 50 lb bow? Your right a 20 lb wouldn't equate but is Fisk using a formula of just a percentage based on weight that would give him for example 4 lb for a idk 50 lb bow and a 2 lb difference for a lower poundage bow. .......    Is there a simple formula that would allow us to assign a lb difference according to bow weight that would be idea of at least ball park for even limb strain and timing because we all know split finger puts uneven stresses on the limbs causing set in the lower unless positive tiller is placed on top. 

[Part time Archer]

  George I would like to apply it to a wooden bow. But this whole talk is about fun and seeing where it goes. It is from a fiber glass site. Don't understand why Fisk would go through all of that. I build I shoot and it doesn't break if I'm lucky. 

[bradsmith2010]

This I s .ca wood bow site

[Pat B]

I never measure positive or negative tiller. I simple look at the fully drawn bow and make sure the bottom limb a bit stronger. If this were rocket science or we were building Swiss watches perfection is probably necessary but with wood bows close enough is enough. IMHO!
 FG mentality is rarely pertinent in wood bow building. That why we build wood bows.   

[bradsmith2010]

A good release will let u shoot a wide range of arrows,,.from a well made wood bow