Disadvantages to long risers/short working limbs?

[bornofmud]

Just wondering why the standard for longbows seems to be a 16-18" riser.  Seems to give people the ratio of riser to limb length that they are looking for, and I'm a bit curious as to why?  From what I can tell, wouldn't longer risers offer more stability and faster speeds? I use a 22" riser (bow length usually 60-64"), and have considered pushing it another inch per side to 24", but wanted to make sure I'm not missing something here haha.  

also, talking glass here, obviously making your riser too long on self bows or trilams is going to push the stress in parts of the limb beyond what the wood can handle (course, that's an assumption, don't have the experience to back it up haha).

[heartlandbowyer]

Depending on your design I think 24 would be fine, would be relatively the same thing as adding a power lam. One note though if you get to short of a working limb your gonna have to change stack and taper formula.

You will have to watch tip/string angle if you got the outer 1/3 of the limb doing most of the work. The angle will come to 90 deg sooner in the draw cycle.
 
Go for it but plan on making a couple bows to get the stack and taper to equal the weight you want.

Cory

[bornofmud]

Indeed, I already have a powerlam that extends 4" past the riser fades, don't think the extra 1" will make too big a difference.  Think i've got the limbs working well though might try reducing the taper slightly and thinning the tip wedges a little. Would be a fun experiment.  More of just wondering I think why 18" seems to be the choice other than 'lot's of bows are made that way.' Hahah. Guess people tend to stick to reducing as many variables as possible and probably don't experiment too much on riser length.

[bamboo]

this----
    You will have to watch tip/string angle if you got the outer 1/3 of the limb doing most of the work. The angle will come to 90 deg sooner in the draw cycle.
have to go longer I reckon and play with the tapers---look at the 21st centuries
and I think prodigy makes fairly long riser/short working limb bows--it can be done

[bornofmud]

I see, so when the ratio of riser length to limb length reaches it's max, it'll be impossible to make a bow that doesn't stack within normal draw ranges.  I get it!  Think I'll keep it how it is, though I'd imagine you could push that concept a bit further with a recurve.

[bamboo]

I'm not an expert--but I have noticed that bows that stack --have run out of limb to bend--and a 90*string angle is a symptom of this--
 its an art-the manipulation of tapers and profiles to maximize energy storage--minimizing [shortening working limb]is one way
I have a static tip recurve with a 12" working limbs and a 26" riser-@ 62"-and it smokes an arrow--but doubt a long draw shooter would like it much!