HBI R/D might have issues?

[JWMALONE]

Thanks guys, The first came out great #45. I sort of had the same problem. I think if had more experience I could have got #40 from this one. But I will book mark this post or wright it down for the next one. Thanks Springbuck.

[Badger]

Yes stiff as all get out. I tried to get the limbs even and bending, I never pulled it to weight because there was no bend in the mid and outer limbs. By the time I got them to bend proper it was under weight. Lesson learned.

  This is one of the reasons I put the bow on the tree when it is still far too strong, like 100# or so. Right from the beginning I am pulling to full draw weight. You can't hurt the bow if it is too strong even if it is uneven. R/D bows can still be finicky doing it this way but they are very difficult to finesse in to proper tiller. Every part of the limb responds to the angle of the string according to its own angle. On an R/D bow you have several angles going on at once, when it starts to break over your angle suddenly changes and the limb will start to cave in on you.

   Once any area of the bow starts to bend too much you have no other option but to lower weight.

[Bayou Ben]

I have a slightly different approach to tillering R/D bows.  I guess it's sort of cheating, but I've had that exact thing happen to me countless times, and I can't for the life of me see the right tiller on these style bows.  The more I mess with the tiller, the more I screw up the tiller. 
So, I take detailed notes on every build.  My goal it to get pretty close to final dimensions at glue up, maybe leaving the belly 5 or 10 lbs heavier than target weight.  I get my thickness taper very precise before glue up.  Once it's glued and I have all the edges rounded and the width taper correct, I start pulling to target weight on the long string.  From here, I'm just cleaning up a couple flat spots and evening up the limbs, then reducing weight to reach my goal.  I let the shape take whatever shape it wants to be not what I expect it to be.  I know some may disagree with this method, but it has worked for me. 

[Badger]

    Ben, I like that method if I could get it to work. Every time I try it I end up with a weak spot.

[BowEd]

I've only done a a dozen or so BB hickories/pecans/osages in a D/R forms but whenever I went tillering past flat in the reflexed area it was no good.The bow lost it's zing.The proper way to tiller these is to work your way from the inner limbs out?

[Bayou Ben]

I've had the same experience BowEd with the reflexed areas.  That's why I now "let it be what it wants to be".  When I say I remove the flat spots, I'm talking about a handful of scrapes here, a handful there, not much at all.  If I thickness taper precisely, I should have a nice gradual transition from deflex to reflex.  I'm only looking for abrupt changes with my gizmo.  I try my best not to make one whole area move one way or the other that's when I get into trouble. 
The downside to doing it this way is that there's a lot of experimenting involved and you can't make changes to your design without starting over with experimenting.  I probably have 10 experiment r/d bows that came in under weight, overweight, had wrong design, wrong materials, etc...
I'm not the person to answer your question on the proper way.  Maybe one day I'll have seen enough of these and I'll develop an eye for the correct shape, but for now it's experimenting till I get it right. 


   

[Badger]

   Ben, I like your method. Once you nail it down I think you will find you can apply it easier. I still look at every R/D bow as an experiment. I started staying away from the r/d and just went into a gradual reflex. I think the r/d is a slightly superior design when done right.

[Springbuck]

Badger: "On an R/D bow you have several angles going on at once,"  Yeah, this is it, too.  They are interrelated and at different stages from resting to brace to draw they effect each other.

BayouBen, that doesn't sound like cheating to me, but good planning.  Probably took me longer, but I do the same.  I  thickness taper my belly or cores on a table I made using my power hand planer, then add kind of long reverse wedges to the tips.  MY biggest problems came from bows that were WAY stiffer than intended draw weight so that by the time I got it down under ridiculous, I'd messed up somewhere.

Ben, what do you recommend for thickness taper?  I never got very scientific about it, but say I take a healthy 70" long x 3/8" lam and I'm adding a 1/8"-3/16" backing and a powerlam.   Do you taper it to half the thickness?  Or,  until it bends evenly to an arc? 

 I'll leave a foot untapered in the middle (so my fades will come off about where the limb taper starts) and thickness taper from there to just under 1/4" thick at the tips.   Then, I may add back 1/8" tip wedges 10" or so long.  Can you add anything to improve my method?

[Bayou Ben]

I can PM you or we can start another thread.  I don't want to high jack John's topic any more than I already have.

[Springbuck]

Either.  Thanks.  I have a method, but I love learning more.

[JWMALONE]

No keep going, this is why I post all the stuff I get into.