limb vs riser lenght?

[kirkwhitehead]

What makes a more stable,faster,harder hitting bow. One that has longer limbs and a short riser or long riser and short limbs?

I have a roy hall 3 pc td and was looking into shorter limbs for it and got to thinking about how limbs about 3-4" shorter would effect the performance. It may not do anything I guess.
But it came to me due to the fact that everybody is making a "SR" or short riser.

thanks

kirk

[Tater John]

Just saw your post kirk. Unfortunately I don't have any idea, so I'll put this up top.

I wonder about 'formulas or givens' between riser and limb lengths too?

I have a neat 'little buckshot' 48" T/D recurve #20@22" but its a tad to heavy for my daughter and she doesn't last very long attempting to shoot it. So its become a dust magnet  :(  
I would like to make some lighter limbs for it but don't have a clue what to do.

Rusty

[Apex Predator]

I'm thinking you will gain quite a bit of weight for each reduction in limb length with same riser.  I inadvertantly cut a one piece longbow riser short by one inch, and lost 5 pounds draw weight from another build with my normal riser.

[TradBowyer]

basically the physics behind bow design is working limb length. the more working limb length you have, the less your bow is going to stack but the more stored energy you are going to lose as well. Bows with shorter working limb lengths will typically be faster and more efficient but will stack quicker. Take a look at some of the fast performing bows of the day and you'll see most have larger risers with shorter limbs. You modify working limb length by increasing riser length, wedge length, ect.

When you cut the limb length down you are shortening the "working limb" length adn therefore, making the bow heavier.

There is really no formula for this. when designing a bow, its best to pick a riser design and design the limbs off of that or vica versa. Trying to modify the limbs and riser at the same time will get you going in circles.

Shortening the limb length on a straigh limbed longbow is okay but cutting the limb length on recurves or R/D longbows will rob your speed (sometimes drastically) cause you just threw off the reflex to deflex ratio. If you don't care about speed, then no biggie.