how do I deal with a "rollercoaster" bow

[Gwynnin]

Making a light warbow (aiming for 85# at 34"). Right now it's 60# at 20". 78" long. Reflexed ~2" with 2 major waves in the upper limb.
   Untitled  by  gwynnin , on Flickr
braced at 4"
   Untitled  by  gwynnin , on Flickr
I'm taking a pause on this one while my belongings make their way across the country to my new home. Also, till I figure out how to get a bow heavier than I can draw tillered.
Thanks!

[George Tsoukalas]

I don't see anything that would prompt such a severe bend in that upper limb about 8 inches from the tip. Looks like it is hinging.

Basically, even though areas are deflexing they still have to do their share of the bending but I think that area is doing too much of its share.

Tough to decide without seeing a pic of the bow at partial draw. Don't draw it 20".

Jawge

[Bowjunkie]

I think it's good so far. That isn't a hinge, it's just the deflexed area doing its share of the work. There are reflexed areas to either side of it, so yeah, it's going to look worse than it is. As you judge bend, always do so relative to the unbraced profile.

There are a couple of things you can do to help. You can use a thickness gauge, slide or roll it down the limb to keep track of your taper accuracy. That alone will keep you from getting in too much trouble.

You can also draw a straight line along the edge of the bow while unstrung, then watch IT change as the limbs are flexed. Some folks find this a great help.

[Eric Krewson]

I would get out my heat gun, take the waves out, even out both limbs and start over with the tillering.

[snapper1d]

I would do like Eric says and that top limb sure looks like it has a hinge! There is a little deflex but when strung up it bends way to much to be from that little bit of deflex.

[Bowjunkie]

I disagree. The reflex to either side has straightened out and the deflex took on a little more bend. That's what I would want.

Straighten it. Pffffft. You guys take all the fun out of it  

[Eric Krewson]

My goal is to always make a top notch bow which will never happen if you leave that much deflex in the limb. You will have a bow that shoots an arrow from point A to point B and that is about it.

[snapper1d]

A hinge like that is a weak spot.The more you bend it the worse it will get till it fails.I want my bows to be perfect as I can get them.I guess I am a perfectionist and mediocre is just not my style!

[Bowjunkie]

Let's try it this way. A hinge is an area of a bending limb that, relative to the unstrung profile, is flexing considerably more than the wood to either side of it. Now, please explain why that's the case here.

I see no hinge. It has some natural curves and they all seem to be bending a little more to get to brace... so it looks good to me... though I would verify in ways such as mentioned above.

Mediocrity? By tillering an odd-shaped limb so that each inch contributes equally to the cause? Not in my book. That's a marker of experience and depth of understanding.

Tillering an odd shaped limb to bend in an arc like a straight limb isn't perfection, it's a big mistake... and THAT'S what creates weak areas, shifting tiller, set, and/or limb failure.

[snapper1d]

Your last sentence is correct but that top part of that limb is bending more than it should.If you can see it I am sorry.

[George Tsoukalas]

Look at the unstrung pic and compare to the strung pic. The hinge is above the deflexed area. Jawge

[Bowjunkie]

Sorry guys. I am certainly comparing the two photos. I looked and looked and then looked again.... and don't see a hinge. Show me. Put an arrow pointing to it or something.

[Ice Mike]

I think this is what they are referring to Junkie..

   

While I think you're correct that it's not a "full-fledge" hinge, this area where the natural deflex is, is bending WAY more than the rest of the limb at low brace, which by definition is the start of a hinge. The other areas of deflex in the same limb are not showing that amount of movement when braced, so it's not just the "deflex phenomena". If this bow were drawn too far this limb would have a true hinge and damage would occur. The limb needs to be worked more to try and correct that before the bow is braced any higher. It isn't to the point where there is wood damage yet, but it will be if any more stress is placed in that area..

[Bowjunkie]

That's what I suspected. If so, I don't think that area is doing anything wrong. That's the most naturally deflexed area that, to me at least, seems to be simply contributing to the overall effort. It SHOULD be bent more at brace than when unstrung... and should continue to bend more throughout the draw.

[Ice Mike]

I agree although I'm no expert by any means, but I think that what they're trying to say is that if this area is bending this much at a 4" brace, then it will compound at full brace and will wind up with this one spot taking on all of the work. That being as it may, will most likely lead to a severe hinge and eventually a break if the limb is not balanced so that the stronger portions are made a tad weaker to take some of that natural load off of the area.

[John Scifres]

I can't tell nothin',  Pull it to 20" and get another pic up.  Preferably perfectly side-on and drawn by hand or on a tillering tree.

[Gwynnin]

I'll do that, though probably not until next week. All my stuff is currently in a shipping container not quite arrived in North Carolina. I'd be happiest with myself if I could get it done without straightening the stave, but since I'm not sure if it's just the deflex or a hinge I'll probably take it out. Hasn't taken much set, but it does look like it bends too much there. Plus, the tip alignment needs to be adjusted a bit.

When you do a major bend like this with a heat gun and not steam how do you like to go about it? I've mostly used my heat gun for tempering the belly and minor adjustments, usually pre-bent on a form. I worry about just clamping a bend this big straight and applying heat - would love to hear some voices with more experience at this kind of operation.

Thanks for all the input!

[PEARL DRUMS]

I dont see a hinge. Id like to see it drawn, at least 15-20". That portion below said spot better start moving or said spot will become a hinge fast. Looks like the outers are stiff on the bottom limb in the picture.

Im with Eric on symmetry. I want to start with a perfect blank. I like perfect bows.

[Bowjunkie]

I like a nice clean, straight selfbow on ocassion, but I like character in them more often. Symmetry bores me sooner than later. I especially value the challenges in making a bow loaded with character AND with the qualities of a really good bow.

[Gwynnin]

Moved across the country, which put this on hold for a bit. Used a heat gun to lightly straighten the problem section and took quite a bit of wood off the stiff section of the upper limb. 65# at 28" now, most of the reflex gone after use. I feel like the tip of the upper limb could bend a bit more, but the stave has some reflex there, so I've been a bit reluctant to push it. Aiming for 85# @ 34". Might have to pike it or heat treat to make that now.

   10620962_10154490295255253_2095734760_n  by  gwynnin , on Flickr

   10609383_10154490305035253_1759154595_n  by  gwynnin , on Flickr