Why did this bow break? Give opinions please.

[mole]

Howdy folks.  This is my first real post here. I met a few of you at Pat's.

This piece of red oak has a lot of history. It was a 1x3 red oak board from Lowe's. It was made into a 74" 70# mere heath bow, but it had too much hand shock. It was cut down to 72" modified version that was 2" wide for most of it's length. It came out to 55# and bent too much on the inner limbs and was a very poor performer. It was then cut down to 68" and tapered from 2" at the fades down to 1/2" at the nocks in a pyramid style.

The bow had a good bit of set at the inner limbs, so in was coated in vegetable shorting pulled into 1 1/2" of reflex and heat treated on 10/03/07. The bow kept about 1/2" of reflex.

Tillering began on 10/11/08 after much humid weather. A long string with about 4 " of play was used to tiller the bow to 55# at 25". A shorter string was then used that gave the bow a brace height of about 1". As I pulled the bow to about 50#, she broke. Tillering was done on a tillering stick and with a knife used as a scraper.

Bow profile


Belly


Back


Side of break


Side at break


This is the first bow break I have had. I've had good success until now, so I blame the heat treat. Maybe it was too dry. Help restore my confidence please. I've got a beautiful piece of Eastern Red Cedar that is begging to be an English Longbow.

Thanks,
John

[snedeker]

I would say it had been over stressed by the overbendiness in the lower part of the limb and the additional tension requirements of shortening caused a tension fracture. It was a pretty nicely shaped job for an early try.  get a new board and start immediately.\
Dave

[DanaM]

Don't overlook backing it with linen, silk or something

[Justin Snyder]

To me there is no doubt it was because of the grain run out into the handle area.  The fades should have been a little farther away from the handle so the grain run out was not under so much stress.  I made a tiny black line to show the grain direction, and a red arrow to show where it let go.  Justin

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[1/2primitive]

I agree with Justin,      thing is, you should keep it completely stiff until the limb reaches full width. Especialy with board bows.
     Sean

[Ryano]

I agree with Justin. To much bending into the handle fade.

[mullet]

  I agree with Justin ,Ryan.But I don't think it really came into play as a factor till you started shortening it and heating.Then you put the stress closer to the fades as you shortened the limbs.I also think it should have been backed to start with.Some of those boards have really been "cooked" and I think when you heat treated it you really dried it out and took away any flexibility left in the fades.

[M-P]

Just to put in my two cents worth.  I agree that the main problem was the handle/ fades.  To throw in an enineering term I learned along the way, putting the fades too close to the handle created a "stress riser".   Over drying during the heat treatment may have had an effect, as did shortening the limbs, but the real defect was always there.    Ron

[Coo-wah-chobee]

                 Grain runout like everybody said. Dosent really matter how close fades were, grain runout would have done it (snap) anyway at some point. Build another nows not the time ta stop ! ..........bob

[Hrothgar]

Looks like a compression problem at the handle. I agree with Mullet, re-heating and straightening a kiln dried board is courting diseaster.

[Robinwho]

Your Handle is too long so you stressed that area where it broke.

[huntersim]

Mole,
I'm gonna be contrary (at the risk of being banned or beaten) and say the break started at the mid limb area in the corner. I think everyone is right when they say grain, but I think one of the biggest problems is that the edge of your limb is to sharp. So iffy grain coupled with a sharp corner on the limb is why it broke. If you round the edges of your limbs more you tend not to get a break that starts on the edge like I think that one did.

The first photo has an arrow showing where I think the break started. The second photo shows in my opinion the last area that let go.

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[a finnish native]

I have to agree with hunterism.

[mole]

Thanks for the replies and advice.  Would using a three inch fade instead of a two inch fade and more rounding of the corners have prevented this from blowing.

Mullet,  If you remember Bruce from Pat's, he has now officially renamed you "The Wildman"

Thanks everyone,
John

[Justin Snyder]

Would using a three inch fade instead of a two inch fade and more rounding of the corners have prevented this from blowing.

Now that is the question.  We can look for causes and second guess ourselves all day long, but sometimes they would have broken no matter what you did.  My best guess is it would have helped. To say it would have prevented is a step I wont make. It is possible that you could have done all that and backed it and it would have broken.  But all those things would significantly reduced those chances.  Its like the old saying,  a bow under stress is already 95% broken.  Now I will add, what we do just determines if the remaining portion that isn't broken is 4% or 6%. 
It isn't really longer fades you are after.  It is making sure you get to a non bending thickness before you start to reduce width to much.  You could make the fades longer, or you can make it a steeper angle.  You want to keep the bending in the full width limb as much as you can.  Justin