D/R tiller- the outer limbs

[DC]

I'm not really sure about this so take it with a grain of salt. I've had trouble with tillering some RD's where "all of a sudden" I have a weak spot. You've probably heard me whine about this before. I think I've discovered what causes it. I believe that if the string is touching the bow(hasn't lifted off yet) there is very little(if any) bending effort being placed on the part of the limb that the string is touching. With these highly reflexed bows if you are using a short "long" string and aren't braced yet this can be a good portion of the limb. More than half in a few of mine. You can carry on happily tillering, scraping the whole limb, and everything looks great. What you may be doing is scraping too much off the outers and don't know it because the string is touching the limb and there is no bending force on it. As the bow starts to bend and the string lifts off, "all of a sudden" there is a bunch of bending force on the weakened limb and you're in trouble. The work around for this is to use a "long" long string so that the string doesn't rest against the bow. This way there is close to full bending force on the limb the whole time and you can see what's happening. You have to keep in mind the problems associated with using the long long string and leave the tips a little stiff until you get it braced. For a normal bow the short long string is still the way to go but I plan on using a long string on my RD's from now on.
I may be out to lunch on this but I've had too many "all of a suddens" with RD's and I had to try something. I've used the long string on the last couple of bows and had no problem but not all RD's gave me trouble. This "all of a sudden" thing has only happened with RD's though.
OK thick skin turned to "max"

[bjrogg]

That's interesting thought DC. I've never ran into that problem but never tillered that type of bow. Only static recurves with a very even gentle reflexed profile of a inch or two. It makes sense to me for whatever that's worth.
Bjrogg

[upstatenybowyer]

I've had trouble with tillering some RD's where "all of a sudden" I have a weak spot. You can carry on happily tillering, scraping the whole limb, and everything looks great. What you may be doing is scraping too much off the outers and don't know it because the string is touching the limb and there is no bending force on it. I may be out to lunch on this but I've had too many "all of a suddens" with RD's and I had to try something.

This is very interesting indeed. I've had this happen a number of times. I need to chew on this a while...

[upstatenybowyer]

Jeff, do you bend both limbs at the same time? I have a one sided caul that I made so I can bend different length bows. I sometimes bend the limbs one side at a time so that I can overlap the backing. Anyway I find that if I do one limb at a time I have a hard time getting them even. I get way better results(as far as eveness goes) when I use my adjustable caul and do both limbs at the same time. However with the adjustable caul I have a harder time getting more curve toward the tips. My adjustable caul is just a 2x4 with three posts(one fixed in the middle and two movable ones at the tips) and I use clamps to pull the limb down to make the reflex. Oh, all of this is for backed bows. For self RD I use a single limb caul and steam bend.

I heat/shape the reflex one limb at a time, but when I glue up I do the whole bow on a full-length caul. The problem is I wasn't meticulous enough when I made it and I think the two sides aren't totally the same. They will be though... 

[upstatenybowyer]

Some may be wondering why all this fuss about the D/R design? The reason I've been so obsessed with it lately is that so far, no design I've made has even come close when it comes to speed.

BJ, I'd love to see what you come up with if you ever decide to give it a go. They are a ton of work, and not the most primitive, but the one's I've made shoot 20 fps faster than any of my selfbows. Still nothing like a selfbow though. 

[bjrogg]

Jeff I was really impressed with the one Paulsemp shot at Elm Hall. My Simply Orange is a pretty flat shooter, but Knoll, Paul and I shot the money bear I think it was called. I forget the yardage exactly. Maybe 80 or 90 yards. Knoll and I both couldn't believe how flat Paul's R&D shot. Never seemed like a good fit for me with my short draw, but it got me wondering if I was wrong with my thinking. I could probably make a pretty short bow I'm thinking.
Bjrogg

[bradsmith2010]

I have made some self bows holding some reflex that would shoot pretty close to 180 fps,, is that design really faster,, our you just like making it more,,,give me some numbers so I can appreciate what you are saying,, I dont doubt you,, I know I have heard of them shooting really well,,,,, just remind me,,

DC,, I think you are right about the tillering,, thing,,and I think its a bit difficult to see the tiller on that shape profile for me,,

[upstatenybowyer]

BJ, you could definitely make a shorter one. 

Brad, I guess I should clarify a bit. I've made some selfbows that have held reflex pretty well, and shot around 170, but from my experience so far (I am certainly not making any universal claims) no bow has ever held it's reflex as well as a tri-lam D/R. It must be all that glued-up surface area. It loses some, but with Steve's no-set tillering it's very little. The one above is only my 3rd successful tri-lam D/R, but all of them shoot in the high 180s. Not only that but I'm always shocked at the early draw weight factor. The string tension is crazy when braced. And then somewhere around halfway you can feel it get easier to pull. It's really cool.

[DC]

I think there is a stepping stone thing here. First there is a straight self bow. Then a backed straight bow will be a little faster. A self RD will be a little faster. A backed or lam RD faster again and I've found a backed RD with static recurves has been the fastest for me, so far.

 I think the backed or laminated hold the reflex better because as PatM said a glued on back is shorter. I'd be willing to bet a nickel that the reason you lose some(I do to) is because the glue creeps a bit.

[bradsmith2010]

Cool....thanks for explaining,,.those are nice shooting bows....

[Stick Bender]

Jeff Im enjoying your D/R fetish mine to ,whats not to like great performance smooth shooting I personally think the excellent performance comes from the early draw weight & superior string angle, as counter intuitive as it sounds I have found the designs with more deflex that are still holding positive reflex are the fastest ones I have made by a fair margin, I really like the design having a long draw it allows me to shoot a shorter bow with a superior FDC , but there is always trade offs in any design and there is some guys here that have made some highly reflexed static leaver bows that are ringing the bell at the same numbers ,I think the long bow shoots heavier hunting arrows at better speeds but for 10 gpp & under its hard to beat the D/R design !

[DC]

I'm just finishing the tillering on my lastest DR. It started as a Yew branch with about a foot of reflex. I cut it in half and spliced in about ten degrees of deflex. This gave me a DR with about 3" of reflex. I used the long string I mentioned above and started tillering. It's a knotty piece so it was mostly rasp and scraper work. I got it so the tips were a couple of inches past the brace height mark. In this time it had actually gained about a half in of reflex. I've had this happen with Perry reflexed glue ups but never with a natural stave. I decided to brace it even though I thought I had lots to go. It braced really easily so I went to full brace. Gave it a little tug and it felt real light. Put it on the tree and pulled. It went right to 40#@27". I was really surprised, I figured I had another hour of tillering to go. Measured the reflex and somewhere in the bracing process I had lost 1 1/2". Fortunately the tiller was good and all I had to do was tidy up the tool marks so it should be OK. Even though I used the long string the "all of a sudden" thing still bit me. I think the long string helped keep the tiller even but even so I came "that close" to coming in under weight. There is still something I'm not doing or doing wrong. Maybe the string was too long. Anyway just a little report on trying the "long" long string.

[bradsmith2010]

u just didnt string it soon enough,,

[Badger]

  DC, I bet your bow also read 40# @27" on the long string. I always brace them 4" or 5" before target draw length. Your long string will measure just like your braced bow instead of watching the tip movement.

[upstatenybowyer]

I decided to brace it even though I thought I had lots to go. It braced really easily so I went to full brace. Gave it a little tug and it felt real light. Put it on the tree and pulled. It went right to 40#@27". I was really surprised, I figured I had another hour of tillering to go.

I would be surprised by that too. Bracing is always one of the most, if not the most difficult part for me. I'm shooting for 65# at 27" and I usually get the string on around 65# at 20" (although it feels like a heck of a lot more than). If I get to this point and the tiller is even, I'm usually home free. From there it's just even removal till I get to my target draw.

Looking forward to seeing that bow Don.