Help Tillering This one...

[arachnid]

Hi Guys.

I`m working on my white oak backed ipe R/D bow and I need some help with the tillering.
The bow is 64" long, the right limb came out 1/2" shorter then the left limb. I`m now tillering with FULL BRACE.
Here are some pics:

Unbraced:
https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-ash3/t1/1779803_586409388115456_879247602_n.jpg

Braced:
https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-ash3/t1/1932235_586409451448783_807291946_n.jpg

20" draw:
https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-frc1/t1/1972269_586409471448781_868893795_n.jpg

I can see a hinge on the right limb, about 3" from the handle, but I don`t know how to go on from here since
it`s only my second R/D bow.

Any advice will be helpful.

Thanks,
Dor

[Hrothgar]

I haven't done many R/D bows, but the left limb looks like it needs to be bending more mid-limb, its a bit flat.

[Hrothgar]

The right limb is bending quite a bit off the handle, you could probably scape a little off about 2/3 the way down the limb.

[burchett.donald]

Arachnid good to see you posting another build...Never tried an R/D but Pappy is working on one...Check out his post on "Yew in the works" and it might help...
                                                                                                Don

[burchett.donald]

Arachnid,I agree with Hrothgar, after going back and looking and If it were me with the little knowledge that I have on R/D I would scrape MID to RIGHT OUTER enough to take some pressure off the INNER. On the LEFT I would scrape the INNER to match the RIGHT. I wouldn't call that a hinge yet looking at the unbraced pic, I think your close to a hinge though. Go slow...Is the top of your tree square? It looks to be leaning in the photo at the handle in the braced picture...
                                                                 Keep us posted and maybe someone with R/D experience will chime in on this...  Don

[adb]

Your bow is bending WAY too much in the middle.

[arachnid]

Your bow is bending WAY too much in the middle.

What can I do to fix it?

[SLIMBOB]

Make it bend more out toward the midlimb to tip area.  I agree with adb.  Far too much bend inboard.
That is frankly where it should be bending the least.  If it takes set there, it will project out in inches, no bueno.

[arachnid]

Thank you all for replying. I posted this question on paleoplanet too and
I was told that since the D/R are not really pronounced, the tiller should look
almost like a straight bow.

I`ll get to work and see where it leads...

Dor

[SLIMBOB]

Just think of it this way.  If it's bending too much in one spot, then it is bending too little elsewhere.  You therefore have two problems compounding each other here.  1. Excessive bend near the handle. This is the worst place you can have it because of the tip deflection when set occurs can be severe.  2.  Not enough bend near the outer limbs mean they're to thick and heavy, further degrading performance.  By taking wood off the outer 1/2 of the limbs you fix both problems.

[DarkSoul]

I agree that the bow is bending too much in the center. That's exactly why I've come to prefer a powerlam in the handle area...it shifts some of the bend away from the center, into the midlimbs. Of course you can also tiller it so it doesn't bend that much in the handle, but the powerlam seems like an easy method that results in less time spent on tillering (but more on making the actual powerlam). I personally think you are already overdrawing the bow in the last pic. You should have seen the excessive bend in the center earlier on in the process. Did the wood take a lot of set so far?
You can easily correct the tiller by scraping both midlimbs, out to the tips. The left limb is also stiffer than the right, so take a bit more wood off the left side. If correcting the tiller means you'll come in underweight, then so be it. Good tiller is more important than reaching a high draw weight.

By the way, you can make those pictures appear right into your post, without the need for people to click those links. Use the [IMG ]-tags for that. Place [IMG ] (minus the space!) in front, and [/ IMG] (minus the space!) behind the direct link. Or: when making a reply/post, use the first icon on the second row of icons: this one.
More info here...

[adb]

Your bow is bending WAY too much in the middle.

What can I do to fix it?

Don't remove any more wood from there. Tillering can be very simply described as: remove wood where the limb is not bending enough, and do not remove wood where it is bending too much. That's a simple statement... the hard part is knowing what to do when.

When you look at your bow on the tiller at draw, what's the first thing that jumps out? To me, it's too much bend in the middle. The limbs are flat and straight and don't bend much from the fades to the tip.

Trust your eye, it will immediately tell you what doesn't look right. If the bow is doing all the work in one small spot only, all the stress of the bend is concentrated in that small area. As a result, your bow will either break outright, or take unnecessary set. If you have a problem like this, sort it out BEFORE you stress the bow anymore.