How do you tell when a bow is at optimum?

[Del the cat]

Dear Agony Uncles
A fiend of mine is building an RD Boo backed Yew bow  .
He's started aiming at a nominal 35# at about 24" which he's nearly at.
But I suspect it would draw out to maybe 27" at about 40# at which point it would be a damn sight faster... but I don't want to over stress it.
should I keep taking it back until I start getting set? and if so, how much set counts as set....?
Or do I quit at 35# @ 24" and then just remove as much mass from the tips as I dare?
Worried of Harlow
Del

[Badger]

           Del, you can weight the draw weight at a given distance such as 24" or even less. Everytime you pull the bow an additional inch go back and check to see if it had changed the weight where you took the original measurement. If the bow has set over night I would suggest you measure it at about 20", and then when you get to 24" go back and check it at 20" again. If it looks good there and you want to proceed recheck every 1".

          Several year ago I brought some bows to a walk the talk event. As an experient demonstration I brought one bow that was to be shot through a chrono at 24" and then slowly proceed to 28". The registration was too large for the demonstration so we went directly to 28". Having tested the bow the previous night it weighed 50#@24" and was shooting 10 rians at a very fast 175 fps. After several pulls working it up to 28" the bow was only 52# at 28" and shot the same 175 fps at 28" which was ok but not great for that draw length.

[Del the cat]

Great reply thanks.
I'll proceed slowly and post pics.
I fear my enthusiasm is outstripping my ability at the moment.
Still I guess that's better than it being round the other way.
Del

[avcase]

Del,
Another approach might be to leave the bow alone and work on the arrow. A longer draw does not always yield a benefit in flight shooting. You may be able to safely draw a 23" long arrow an inch into the bow and get enough spine at only 125-130 grains for clean and fast arrow flight.

As you lengthen the draw length, you also need to increase the length of the arrow and increase the diameter of the arrow to get enough stiffness for clean arrow flight. The longer draw arrow will be heavier and may not be leaving the bow any faster than the light short draw arrow. In addition, you may be fighting some risk of set and hysteresis losses in the bow.

It is a challenge for sure.

Alan

[Badger]

     I find my bows I build tend to peak at aroundd 24" for efficiency and then start dropping off, hopefully not by much. For flight bows I like to be able to uses a 23" arrow if I can.

[Del the cat]

Cheers guys... I'm prob' being caught out by being used to long draws and sort of wanting to use it as a field bow too .
A bit like wanting a sports coupe with FWD and off road tyres
The fact that my longest ever shot was from 32" draw is also skewing my perception.
Maybe I need to make something to be deliberately short draw.
As for arrows, I hear what you are saying, and I've done some work but it's not my fave. Mind, having said that, I managed to shorten a couple of shafts yesterday while shooting in the woods so I've got some stiffish spine shafts to play with.
Always the same too many bows and arrows to make, too little time

I'll post it when it's done, good or bad.
Del