Reverse Tapers

[Pennsyltuckey pete]

What do you feel about reverse tapers?  I have not used them in any of my bows.  It has been suggested that I  build one with reversed tapers.   When I look at the math I see that I can get the exact same limb dimensions without using them simply by decreasing the normal taper.  I understand the idea of keeping the tip a little weightier for stiffness but I see no gain at all over simply modifying the tapers in my limb stack.

I am sure that there has to be something to this that I am missing!  HELP

pete

[jess stuart]

I have used them a few times building t/d longbows.  I now use tapers with a powerlam and tip wedge, which I like better.  I think the idea of the reverse taper is to keep the tips stiff, and by sliding the taper around you have good control over stack thickness.  

The tip wedge keeps the outer limb stiff with less mass and generally gives better performance.  One can affect where and how much the limb bends with the use of powerlam and tip wedge.  I don't know if that answers your question or not and it is only my ideas and they could very well be incorrect.

[Jason Scott]

I agree with you Pete. A reverse taper only cancels out some of the forward taper no matter how you slide it around. The thickness profile will be no different than if you build the limb with the lesser forward taper rate using all forward tapers. The tip will be the same in relation to the mid limb too. The only difference is where the glue lines shake out. Like jess said, tip wedges offer the performance options.

A couples rules of thumb I have learned about tip wedges: One is that you may need a longer tip wedge the higher the forward taper rate and shorter tip wedges for mild forward taper rates. Mild forward taper rate limbs realize less benefit from tip wedges. And two, you only need enough wedge thickness that will allow enough wedge taper to cancel out the forward taper and maybe a smidgen more, any thicker is just added tip weight.

As for power lams, the higher the forward taper rate the less need for them. The lower forward taper rate limbs benefit more from them.

[Jason Scott]

The only benefit I can see in using reverse tapers in a limb is if there is a material availability issue and the only way to get the stack/taper rate I need with the laminations on hand is to flip one of the tapers around. I wouldn't design a bow utilizing them. I grind my lams before layup of each bow so I shouldn't have that problem.

[Pennsyltuckey pete]

Jason,  
Thanks for confirming "My take" on the one cancelling out the other.  I too grind my own lams so material is not an issue.

Should I try reverse tapers or wedges on the design I have come up with?

On the longbow that I am developing (Still playing with the limb design) i built the stiffness in to the tip by managing the shape of the bow form. This way I am keeping the tip of the bow as light as possible.

here is a pic of the bow at a full 30 inch draw.  you can see that the tip has not rolled over yet.

 

is there any reason to try a reverse taper?  

Any input will be greatly appreciated.

pete

[BoWyo]

Pete, you hit the nail on the head. Reverse tapers add stiffness, but so does bending more in the form.
Dictating where your limbs bend is one of the fun and challenging things about bow design.
Being able to reduce weight in your limb is key.
Both methods  can work depending on your design.
Harry Drake always used reverse tapers in his recurves. He also used alot of parallel lams and reverse tapers. He felt he had more control over his design and that it  performed better.

[Jason Scott]

Need to see an unstrung profile and strung along with this full draw profile to guess what it could benefit from. Without shooting it too it is really just a guess. Your tips look great in the pic but not knowing how they effect the midlimb and fade area during the draw it is speculation. I think your reflex is sufficient for stiffening them up. The fades look like they are not overworked too. It would be easier to see from a straight on shot on the tiller tree.