Limb Thickness figuring question

[J. R. Harp]

I'm planing on making some Pronounced Take Down Longbows (by Binghams).  I have ordered the dvd's, prints, components, ect. from them but wanting to buy laminations and woods else where for more options.  Looking to build a 62" version 45-50#.  They told me I would need a limb thickness of .250" for that draw weight.  The limbs use a reverse taper, parallel, and a taper.  Was wondering how to figure what taper measurements I would need to order to get that limb thickness?  Thanks

[kennym]

Pretty sure they measure all 3 at the butt (riser end) of limbs,so thin end of reverse, thick end of forward and your parallels.

[kennym]

Pretty sure they measure all 3 at the butt (riser end) of limbs,so thin end of reverse, thick end of forward and your parallels.

[fujimo]

anybody figured out why they use the reverse taper?

[Crittergetter]

My guess is someone screwed up one day and put a taper in backwards! It worked out ok so they called it a reverse taper to save face!  

[J. R. Harp]

Is there a suggested taper size I should get?  What should both ends of the tapers be? First time ordering and tapers are the only things confusing me.  Thanks

[fujimo]

[fujimo]

iffin you are ordering from binghams they will know what to send you- they are very helpful- otherwise it should be in the plan specs somewhere- i have the same plans here- but in a takedown- so really cant help you. but someone will come along right quick with the answer.

[monterey]

I think the reverse taper is used under the lay up rather than as part of it.  For example, when doing an ASL with tapers under the riser You need equal taper under the lay up.  Otherwise, you need to put an equal and opposite taper in the riser block to keep the lake and the riser block matched.  If all the taper is in the top lam (the face side) Then no compensation is needed.  I guess this is as clear as mud!    

Your materials from Bingham Will clarify all this.  If not, call them for information.  They are very willing to help.

[jess stuart]

They do use a reverse taper, one taper and a parallel which makes the limb parallel.  The only taper in their design is in the limb width.  I built a 62" years back it mikes out at .260" total thickness, and weighs 45# @ 28".  Probably something like .040 glass x2 (.080").  Two .070 tapers (.002) and a .040 parallel.  One of the .070 tapers needs to be reversed.  It is possible I put more side taper into the limbs than the Bingham plans call for.
I am pretty sure a bunch of guys have built that design so someone will probably have more info for you.  Good luck on your build.

[monterey]

Wonder why they don't simply use two or three parallel lams??

[kennym]

I know guys have built them with 3 parallels, that's where you end up anyway, with a parallel limb.

I was told Binghams said the thick end of the reverse taper made the tip more stable. I can't really see it, but that's just me.....

[monterey]

Can't see that either.

[jess stuart]

The only possible advantage I can see.  If you slide the reverse in or out you can easily vary the stack by a few thousands.  Kind of micro tune the limb thickness to exactly what you desire.  Real value over all parallels probably none.

[Buemaker]

I am with monterey, the reverse taper is not part of the lay up.

[kennym]

The reverse is part of the bow layup. I have built 2 of these, still don't know why it is designed that way.

[mikkekeswick]

Could it be that the reverse taper is thinner at the riser end and therefore conforms to the fades curve better? I'm guess here!