Lesson Learned...

[Christian Soldier]

In a nutshell: "Never settle for an imperfect tiller."

Here's the back story. I've got this hickory pyramid bow which is coming out to be pretty much my dream bow. Perfect length, draw weight, good looks even pre-stain, and everything about it was great except the lower limb was a little weaker but it had some reflex so I figured it'd be alright.

This bow was a rebound off of a hickory west coast bow which fretted and that was a rebound off a black walnut bow which just snapped because of a slight error in ring chasing.

So today I was just about to put a finish on this hickory bow and I see what I thought were rasp marks that I just neglected to sand out when it fact, they were frets. 

I've made a dozen or so hickory self bows with very few problems and now two in a row with cryssals. 
So, that dream bow goes in the utility room of remembrance and I'll start on a new one and I definitely won't settle for anything but perfection on this one.

I'm guessing pretty much all of you more experienced bowyers knew this lesson well but I figured it would help with the coping process if I shared it with others. 

[BOWMAN53]

R.I.P hickory pyramid bow, atlease you dont have to rest in pieces lol.

[PEARL DRUMS]

A good trick to find them earlier is to take a damp cloth and wipe the belly down under a good light. It will darken up frets, scratches or any other imperfections.

[JW_Halverson]

A good trick to find them earlier is to take a damp cloth and wipe the belly down under a good light. It will darken up frets, scratches or any other imperfections.

Oooh!  Gonna steal that for my trick bag!  Nice tip.

[Osage Mark]

what are frets and why do you get them?

[Bryce]

what are frets and why do you get them?

Fret or "stress fractures" happen when the wood cells on the belly side of the bow collapses and makes little horizontal wrinkles.

[Thesquirrelslinger]

what are frets and why do you get them?

Frets are caused by belly compression- if you have a hinge in the bow, the belly is compressed quite a bit in that area, usually it is compressed more than the wood can take- most wood fails at about 1% compression(according to several sources I have read). in a well-made wooden bow, the compression is lower than that. horn fails at about 4%. Softer woods are GENERALLY weaker in compression, but may be more elastic, compensating for that- Yew is one.

[Osage Mark]

Thanks guys    http://www.primitivearcher.com/smf/Smileys/default/smiley.gif

[mikekeswick]

You said your lower limb had reflex but was acting weak so you left it. Well if a limb is more reflexed than the other it should look proportionately stiffer not weaker.
Squirrelslinger - Horn can take a lot more deformation than 4%...have you made a horn bow?
Yew is an exception among softwoods (apart from junipers) so you really can't use it to describe the properties of softwoods.
Pines are actually quite often stiffer than hardwoods....if you don't believe me try making arrow shafts from various timbers. Would you believe that redwood arrows of the same diameter spine out at about the same as ipe shafts.

[blackhawk]

Are you sure it was tiller that caused the frets and not an under designed bow pulled to far? What are all the stats...length,widths,draw weight and draw length?  Just trying to solve your problem and make sure it wasn't something else....an imperfect tiller+under designed can easily lead to frets as well...

And use osage next time

[Gordon]

A good trick to find them earlier is to take a damp cloth and wipe the belly down under a good light.

You can use mineral spirits if you are concerned about adding moisture to the wood.

[George Tsoukalas]

2 thoughts.

Some crave that photo of a great tiller. The picture perfect tiller is not aways the best one for that particular stave. For example, knotted areas (weak) should not bend as much as the rest of the limb but should bend slightly. Dips and bends need to work as do areas of reflex. All of those affect how the tiller looks to the eye.

Frets (large) and chrysals (tiny) are cracks across the grain on the belly.

There are 2 causes. First, is an imperfect design for the stave. The stave is too narrow or 2 short and then the chrysals will appear all along the limb. Second, localized chrysals in  one area mean the limb is bending too much in that spot. In this case the fix is too retiller leaving the chrysalled area alone. Retiller the other limb to match. I've had some success gluing on some rawhide over that spot.

The eventual end result is the bow will fold up like a book if the chrysals are not fixed and even if they are.

Christian Soldier, look at the chrysals as learning tools. They'll show you a poor tiller or design to be avoided on the next stave.
Jawge

[Josh B]

I take it that this is the same bow that you just heated reflex into a couple days ago?  Are you sure they're compression fractures and not tears from reflexing a shot in bow?  I too would like to help in the post mortem so you will be sure to avoid repeating whatever caused it.  You always learn more from the screw ups than the successes.  Well at least I do anyway.   Some pics would certainly be helpful.  Josh

[George Tsoukalas]

When you've found them, it's too late. They never go away. But the  damp cloth wiped on the stave is a good finishing technique because it raises the grain and shows unsightly nicks which can be sanded.

As an aside sanding chrysals just makes the tiller even worse.

I wipe and sand with 220 grit until the grain is no longer raised. Then finish with 300, 400 and 600 grit. This is an old woodworker's trick. I guess at 65 I'm an old bowyer. Thank God!

Jawge

[Christian Soldier]

Yes, this is the same bow that I heat treated but, reflecting to the past I remember those 'marks' being there before I heat treated it.

It was right below the fade and it was 2" wide so it wasn't a design thing. Just that the lower limb was weaker and that was the weakest point of the lower limb.

It's one of those light hinges that is painfully obvious now but I just ignored earlier.

My camera would focus on the Frets (definitely big enough to qualify) but here's the profile and tiller pictures. Lower limb is at left and the hinge is just below the fade.







I attributed the weak limb thing because the lower limb was an entire 'ring' lower on the belly, I figured I'd let it go.

Live and learn. Maybe someone else can learn from my lesson too. I was also kind of rushing this bow to finish it for hunting this year. Apparently its easy to miss things when rushing.

Debarked the new stave yesterday. Its got some snake to it but no knots so the tillering should be pretty straight forward and I'll be sure to keep this one a little wider too. It'll probably be done in a month or so.