Design Changes Affecting Draw Weight

[matt_w]

This winter I made a form for an aggressive R/D design and after gluing the first bow up on the form I decided I need to make some changes. The bow I glued up was lacking vertical limb stability and the limbs were too floppy for my liking. I am planning to redo the form and drop the reflex in the limbs and was curious how much of an affect that will have on draw weight. I have searched on here and can't seem to find any information on the affects of dropping reflex by 1'' or 2'' on a bow design. I know it will be different from one design to another, but a ballpark figure would help me in determining my stack for the next bow.  So, anyone have any ideas on how much dropping 2'' of reflex with affect draw weight? I don't need to hit the weight just right, but want to be somewhat close.
Thanks for your help

[rmorris]

Don't know how much this will help ya but a change of 5 degrees on my takedown bow changes the weight by about 10 pounds.

[matt_w]

I'm assuming you are referring to the angle at which the limb attaches to the riser which I would assume is going to affect the preload on the limb. I'm not changing anything coming off the riser and am keeping the same deflex in the limb, just taking out some of the reflex in the outer portions of the limb. So it is a different type of change to the limb profile than what I think you are referring to, but at the same time, I don't know how it will affect things. I would think it would have less of an affect than what you experience by changing your takedown limb angle but I don't know for sure. Ultimately I won't really know until I glue up a bow, but if its going to be a 10 pound change like you experience it would be good to have somewhat of an idea on it.
Thanks for the reply and the info

[Ice Mike]

Seems to me that if you are just changing the amount of reflex on the outer portion of the limbs, you could get an accurate measure of the amount of change by bracing the bow you've already made and pulling it to around 25-26" with a scale. If you are not changing the profile of the deflex or the any of the length/width/taper dimensions I don't know why this wouldn't be pretty accurate because the only thing that would be changing is the distance the outer limbs will move while at full draw.

You could then take that measurement  and calculate how much you would need to add to the stack to bring it back to target weight at full draw with the decreased reflex.

[LittleBen]

Hey Matt how long is the bow you're talking about and how much reflex?

May just need a higher brace height o stabilize, might need to reduce reflex as you said and increase brace height.

[matt_w]

Its a 60 inch bow. Not exactly sure the proper way to measure reflex, but if I run a line from tip to tip and measure from the throat of the grip to the line it is about 5.5 inches. I am planning to drop it to 3.5 inches of reflex. I haven't messed with the brace height much on the current bow.

[Black Mockingbird]

You'll lose approximately 5 pounds and prob no more than that...that is a bit of high reflex,but it shouldn't cause the bow to be "floppy" as ya put it,can you explain further please...I think there's some pieces of the puzzle missing to solve your conundrum,and not sure if just reducing the amount of reflex will solve it? And also there is other factors affecting limb stability as well other than high reflex,and there are ways to adjust that with limb widths as well etc etc...

[savage1]

Dropping the taper rate of the lams .001 or. 002 might be all you need for stability.

If you raise the brace it may get to where it takes a good strung shape yet you can move the limbs. It will look more like a string follow bow but it may shoot sweet depending on stack point. If you draw and hit a wall forget trying less taper and lay the limbs back more on the next one.

I know of a custom longbow out there that you can move the limbs easily out of shape and they shoot sweet.

Lou

[matt_w]

Sorry it's taken a while to reply back to this post. I appreciate all of your advice. As far as 'floppy limbs', what I mean is if I hold the limb tip in my hand and extend the bow out the weight of the bow causes a good amount of flex in the limb. Also, it's not hard to get the limb to cave in toward the string when I apply pressure to it. This all said, I went up with the brace height to 8 and it seems to have helped with stability. I was shooting it and I think it will at least be worth finishing and shooting. As far as the form goes, I'm thinking I will drop the reflex and then start fresh.
Thanks for the help guys