Video of limb failure. . . confirmation of tiller error please?

[Rākau]

Hi guys. . . 

So I managed to break my 2nd bow of the week, , , was looking at 68" ntn with 55# at 30" flatbow design following dimensions from one of Clay Hayes' video's on Youtube. On the tiller tree it looked pretty good to my eye, so I sanded her up etc took it to the range and put 8 arra's through her no worries (couldn't do any more as it was dark by then) took it home and waterproofed her with a boiled linseed/beeswax/turps conditioner i made a while ago. while doing this i decided to do a light 10 minute heat treat on the belly, just because I'm a newbie and I hear that's what people do and I liked the colour it bought up in a previous bow (that also broke due to poor tiller) haha. Anyway, silly me didn't re-check tiller, but i wanted a video of bow at full draw so. . .
(very short video)

https://youtu.be/O1CzHyhjfcs

so you guessed it, crack!

Now upon review of the video it seems blaring obvious that the lower limb was far to weak and it snapped right on a potential hinge point... so I should always re-check tiller after heat treat? (seems obvious upon reflection)

But also to note is that my other Kanuka bow snapped in much the same way (albeit in a far less utterly complete and dramatic fashion) in that the belly of the bow held up to the snap so well that there is not a single visible sign of stress. Is this an indication that kanuka is stronger in compression than in tension and maybe I should avoid heat treat, or can the blame be placed fair and square on my well below average tillering ability?

Anyway, I really appreciate the pointers that I have been given so far, time to rough out some more staves and get em drying behind the fire place for the next round of attempts!

Zach

[Del the cat]

Lower limb hinging exactly where it breaks...
I was looking and thinking it's weak th.... bang!
Tillering is very subtle, it takes a bit of practice to get your eye in, and then nothing looks 100% perfect and you can end up tiller blind...
That's why I take video
Del

[Eric Krewson]

Did you tiller your bow with a tillering gizmo?

I heat treated a hickory bow a few weeks ago, the heat treating threw the tiller way off and I lost a good bit of poundage getting the tiller back in line.

[simk]

hi zach, your desings also seem a bit on the limits to me - short bows with even shorter bending sections. doing so requires both, perfect wood and perfect tiller and still is risky. wasnt number one even shorter? cheers and good luck for the next one. basicly you do very nice work. never give up - i lately had 3 bows broken!

[Mesophilic]

Zach, I plan to heat treat my first bow soon so I've been doing alot of reading.   Did you let the bow rest for a week or so to rehydrate after the heat treatment?  It seems to be a common theme that is mentioned frequently.  If so, do you think the sealer you applied may have interfered with this?

[bushboy]

Agreed.great attitude though!that's half the battle!

[RatherBinTheWoods]

If the lower limb was more like the top you would have been just about spot on. Next one :0)
 

[bjrogg]

Now in hind sight that you see that weak spot you'll probably notice it better next time you see it. You've got a great attitude and it'll get you where you want to be. I know how hard it is to laugh when you almost want to cry. If you didn't give it a couple days after heat treatment that may have contributed also. Another caution don't let the heat get around to the back of bow. Heat helps compression it kills tension. Not saying that happened just a warning. As for the effect of heat on this type of wood I can't help you there. A little longer bow will make things more forgiving also.
Bjrogg

[osage outlaw]

I like the sigh as soon as it snapped.  You've recognized the problem.  Now learn from it and improve on #3

[paulsemp]

It happens... Looks like you're building a trailer there?

[Rākau]

You lot are awesome, thanks for all of the feedback!

Yeah I think I might be taking more video from now on Del, well once i think I'm getting close to final tiller anyways.

Did you tiller your bow with a tillering gizmo?
I heat treated a hickory bow a few weeks ago, the heat treating threw the tiller way off and I lost a good bit of poundage getting the tiller back in line.

haha If you can call clamping a bow upside down in a vice a tillering gizmo. . . but yes I will make something proper up for the next one and I need to sort out a clean background, that might help too.

hi zach, your desings also seem a bit on the limits to me - short bows with even shorter bending sections. doing so requires both, perfect wood and perfect tiller and still is risky. wasnt number one even shorter? cheers and good luck for the next one. basicly you do very nice work. never give up - i lately had 3 bows broken!

Thanks simk! haha i dont know if that is reassuring or not  . funnily enough I read Steve's "Build Along (building by mass)" last night, and i punched in these numbers to an excell sheet I made based on the parameters he gave: ntn  67", draw length 33" (based on quite stiff outer limbs), handle+fade 14" (based on the fact that I didnt get it bending enough near the fades) and weight at 55#.
The formula tells me that I should be at 780g (28 oz). . . actual weight of the bow was 670g (23.6 oz)
so as you said, not enough bending area by far!
If i had got the fades bending more, and dropped target draw to 50# i would have been right on the money! haha next time.


dieselcheese: good point, I am impatiant, although it did rest overnight?

If the lower limb was more like the top you would have been just about spot on. Next one :0)

haha I'll cut the top limb off and save it for when the next one breaks and make a take down!!


Thanks bjrogg! next one will be 70" pyramidish with a nice short handle/fade section, maybe even a bit bendy handle. as far as heat treat goes, I can no where near mark the belly with my thumbnail after heat treat, but can still mark the back and sides? does that sound about right? and I'll let them rest a bit longer next time too.

Thanks Bush!
Thanks Osage!

It happens... Looks like you're building a trailer there?

yeah mate, getting a new boat, so a trailer is needed haha

[bradNZ]

Good to see another Kiwi on here making bows from our woods! I've been dabbling for the last year or so but have only made 1 semi successful bow due to lack of time/practise. But getting back into it again and making a bendy handle bow for the next one. You're bows are way better than mine!

Don't give up, Kanuka is a decent bow wood.
Shamusrobert is a member of this forum, I went and checked out his bows in Blenheim the other day, he's been successful making some beautiful bows from our woods.

Just out of curiosity, you arn't chasing a ring are you? With Kanuka all that is needed is for the park to be stripped off, I'm sure you know this.

I'm looking forward to seeing your next bow!

[Bob Barnes]

Make a tillering Gizmo and try it next time...
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiI2rHH7_LbAhXLrVQKHcuBB5IQFggpMAA&url=https%3A%2F%2Fwww.3riversarchery.com%2Fblog%2Fhow-to-make-and-use-eric-krewsons-tillering-gizmo%2F&usg=AOvVaw2DTlZymrYYDTvX_d9wh1YR
 ...and when you heat treat or heat bend a bow, you should allow it time to re-hydrate before straining the wood...

[Rākau]

Good to see another Kiwi on here making bows from our woods! I've been dabbling for the last year or so but have only made 1 semi successful bow due to lack of time/practise. But getting back into it again and making a bendy handle bow for the next one. You're bows are way better than mine!

Don't give up, Kanuka is a decent bow wood.
Shamusrobert is a member of this forum, I went and checked out his bows in Blenheim the other day, he's been successful making some beautiful bows from our woods.

Just out of curiosity, you arn't chasing a ring are you? With Kanuka all that is needed is for the park to be stripped off, I'm sure you know this.

I'm looking forward to seeing your next bow!

Yew!!!! thata one haha bloody stoked you commented mate! I didn't know that cheers mate, but I have just been taking the bark off because i didn't want to attempt chasing a ring but was thinking about chasing a ring later on if i keep getting failures. . .but so far both failures have been my fault, not the woods. but chur bro good to hear that chasing a ring isn't needed cause I wasn't looking forward to attempting it!

Any chance you could enlighten me on some other good woods in NZ? haha I have a few in mind but not really sure.
I have seem some of his Kanuka bows on here, he doesnt seem to be active any more though?

Make a tillering Gizmo and try it next time...
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiI2rHH7_LbAhXLrVQKHcuBB5IQFggpMAA&url=https%3A%2F%2Fwww.3riversarchery.com%2Fblog%2Fhow-to-make-and-use-eric-krewsons-tillering-gizmo%2F&usg=AOvVaw2DTlZymrYYDTvX_d9wh1YR
 ...and when you heat treat or heat bend a bow, you should allow it time to re-hydrate before straining the wood...

haha I'm gonna do it!!

[bradNZ]

Haha yea it would be a mish to chase a ring on!

Apparently Black Maire and Akeake do well. I’m terrible at IDing trees which make it hard!
I’ll try find some others and let you know.