Primitive Archer
Main Discussion Area => Bows => Topic started by: Ifrit617 on June 05, 2013, 08:32:02 pm
-
Hey all,
I've made 8-9 red oak bows now and I've learned quite a bit about the wood. 5 have chrysaled, 2 due to tillering error when I first started, 1 due to an over-strained design, and 2 for no particular reason that I could deduce. I have never had one break in tension, and all have been unbacked, some with questionable grain. Out of the 20 or so bows that I have made, those 5 are the only ones that ever chrysaled/failed on me.
Therefore, I used to HATE red oak.
I found out with the last two I've made that the secret to red oak is to highly crown or trap the back. For all you newbies out there, this increases stress on the back and decreases stress on the belly. By doing so, chrysals are much less likely to appear.
This also helps with set. For example, I've made 4 red oak ELB that were 1 1/8" through the handle straight tapering to 3/8" tips. They were just over 3/4" wide at mid-limb and 70" n2n. Many people would say this is two narrow for red oak. I disagree. I trapped the back to 50% width on the back on two bows and left the other two alone.
Of the 4, none have chrysaled, but the two I didn't trap took nearly 2-2.25" of set after shooting in, due to the belly being somewhat over strained.
The two I did trap both only took between 3/4" and 7/8" of set after shooting in (around 500 arrows) and are noticeably faster. All the bows pulled between 40-45#.
I've seen many beginners ask how to reduce set in their oak boards limbs and I believe this is the key. I've found that a board with good grain will fail in compression long before it fails in tension. So don't be afraid to put an aggressive trap on the back of your board before you begin tillering. It will make a world of difference.
Jon
-
Thanks for sharing that.
-
Good to know.
-
Curious what trapping the back has to do with belly compression?? I read what you wrote...although interesting... not sure how trapping would help a wood like red oak. Can you elaberate your reasoning?
VMB
-
Curious what trapping the back has to do with belly compression?? I read what you wrote...although interesting... not sure how trapping would help a wood like red oak. Can you elaberate your reasoning?
VMB
Tension and compression forces are spread over surface area. As the surface area of the back decreases, the tension is more cconcentrated, causing the back to work harder than it would if wider. This relieves forces on the belly, as more of the force acting on the bow is forced onto the back, since the back to belly ratio is decreased. Instead of a 1:1ration of forces, the back is narrowed by 50% in my case, causing the ratio of back to belly surface area to be 1:2... Therefore the back takes half of the compression felt by the belly, reducing likely hood of the red oak failing in compression... For me the results speak for themselves.
Jon
-
essentially what your doing is balancing the woods forces so that they are close to equal, an equalized wood like yew or osage takes less set without having to do much of this if anything...wonder why, oh yeah, they are closer to equalized ::) ;) it really does help i believe
-
101 Curiousity Ifrit617; Is it possible to post a side profile pic of a red oak bow..?
thx, cheers
-
True. I round the backs on my red oak bows. Works well.
-
jon an other biggie with red oak as far as i'm concerned is pyramid, best design in my book for red oak
-
That's quite interesting indeed!
Someone posted in another thread a while back that, for ash bows, it is better to trap the belly.
Interesting how the two woods contrast like that.
-
I love these little nuggets of experience!
Thanks for sharing the results of your puzzlings.
-
The beauty of experimentation, is you stumble on to "The right way of doing things". ;D
The end result is, you can't argue with the end results, and if a different process works, then by all means use it.
Good job, and excellent effort at being observant.
-
That's quite interesting indeed!
Someone posted in another thread a while back that, for ash bows, it is better to trap the belly.
Interesting how the two woods contrast like that.
Surely you mean trap the back, not trap the belly? Ash is tension strong, not compression strong. Trapping the back works excellently with ash, whereas rounding (essentially trapping) the belly into a D section for instance, causes set, chrysalling and sometimes breaks.
-
That's quite interesting indeed!
Someone posted in another thread a while back that, for ash bows, it is better to trap the belly.
Interesting how the two woods contrast like that.
Surely you mean trap the back, not trap the belly? Ash is tension strong, not compression strong. Trapping the back works excellently with ash, whereas rounding (essentially trapping) the belly into a D section for instance, causes set, chrysalling and sometimes breaks.
I'm almost positive it was trap the belly to 50% the width of the back :o
When I get a bit of time later I'll try find the post. Think the title of the thread was something to do with "ash bow"... :-\
-
That's quite interesting indeed!
Someone posted in another thread a while back that, for ash bows, it is better to trap the belly.
Interesting how the two woods contrast like that.
Surely you mean trap the back, not trap the belly? Ash is tension strong, not compression strong. Trapping the back works excellently with ash, whereas rounding (essentially trapping) the belly into a D section for instance, causes set, chrysalling and sometimes breaks.
I'm almost positive it was trap the belly to 50% the width of the back :o
When I get a bit of time later I'll try find the post. Think the title of the thread was something to do with "ash bow"... :-\
Do you believe everything you read on the internet?
-
So for a pyramid bow, since it is thinner anyway, do you still round the back? Would you make it more of a sword profile? Full thickness in the center back, tapered to a thin edge, with a flat belly? Almost a D profile in reverse? Or with pyramid bow do you leave it as is, from what I have read that is the point of a pyramid bow, same thickness tip to fade.
For now I am just playing and making bows for fun. They won't get a lot of shooting, but I would like them to work and to last a long time. Resources and experience - lack of - direct me to red oak pyramid bows for now.
-
I just round the edge real good, not totally trapped
-
That's quite interesting indeed!
Someone posted in another thread a while back that, for ash bows, it is better to trap the belly.
Interesting how the two woods contrast like that.
Surely you mean trap the back, not trap the belly? Ash is tension strong, not compression strong. Trapping the back works excellently with ash, whereas rounding (essentially trapping) the belly into a D section for instance, causes set, chrysalling and sometimes breaks.
I'm almost positive it was trap the belly to 50% the width of the back :o
When I get a bit of time later I'll try find the post. Think the title of the thread was something to do with "ash bow"... :-\
Do you believe everything you read on the internet? of coarse, they cant put anything on the internet that aint true >:D
-
Sounds good but I think the experiment is highly anecdotal. Never before this have I heard that red oak is so tension strong that it forces itself to take set. I've seen some very successfully trapped red oak board bows but I don't think it's a true solution to red oak bows taking set. I believe its more likely that the design or building technique was poor in the first place.
-
The actually amount of tension strength may not be so important is the relative tension strength to the resistance of the belly. Red oak bows that I've trapped also have taken less set than those I've not trapped.
Gabe
-
Haven't y'all gotten the memo......YOU CANT MAKE A "BOW" FROM A BOARD!!! That's why your having problems,your not using real bow wood...try some osage ;)
-
Haven't y'all gotten the memo......YOU CANT MAKE A "BOW" FROM A BOARD!!! That's why your having problems,your not using real bow wood...try some osage ;)
Send some my way Chris and I'll pump one out. ;)
-
I still can't wrap my mind around this trapping concept....in my mind it's only creating a crowned back??? I have read how it is suppose to work, but I am not sold on it. :)
VMB
-
Haven't y'all gotten the memo......YOU CANT MAKE A "BOW" FROM A BOARD!!! That's why your having problems,your not using real bow wood...try some osage ;)
Send some my way Chris and I'll pump one out. ;)
As soon as ya send me out some primo straight clean 50rpi+ yew I will >:D
-
try it VMB go buy a board and try it and see if does anything vs a non trapped
-
Haven't y'all gotten the memo......YOU CANT MAKE A "BOW" FROM A BOARD!!! That's why your having problems,your not using real bow wood...try some osage ;)
Send some my way Chris and I'll pump one out. ;)
As soon as ya send me out some primo straight clean 50rpi+ yew I will >:D
You can put it on my tab :P >:D ::)
-
Haven't y'all gotten the memo......YOU CANT MAKE A "BOW" FROM A BOARD!!! That's why your having problems,your not using real bow wood...try some osage ;)
Send some my way Chris and I'll pump one out. ;)
he's probably got plenty of kindling muffy >:D :laugh:
-
Haven't y'all gotten the memo......YOU CANT MAKE A "BOW" FROM A BOARD!!! That's why your having problems,your not using real bow wood...try some osage ;)
Send some my way Chris and I'll pump one out. ;)
he's probably got plenty of kindling muffy >:D :laugh:
I know! he probably needs to do a bit of cleaning, i can definitely use some of that useless golden firewood. >:D
-
Sorry..but I got some bad news...just went thru my stash and didn't see any that had the name ionicmuffin written on any of them.... >:D
And wait till you guys see the "stave" I've been working on now...I'll give ya one hint...its red...lol :laugh:
-
Sorry..but I got some bad news...just went thru my stash and didn't see any that had the name ionicmuffin written on any of them.... >:D
And wait till you guys see the "stave" I've been working on now...I'll give ya one hint...its red...lol :laugh:
Try looking for Graham, or Gates, Or Everett.
So what you're saying is that your dipped your stave in beet juice?
-
<snip>That's why your having problems,your not using real bow wood...try some osage ;)
I thought we'd all decided to switch to Poplar???... ;) :o ::)
OneBow
-
I still can't wrap my mind around this trapping concept....in my mind it's only creating a crowned back??? I have read how it is suppose to work, but I am not sold on it. :)
VMB
Not sure if this is actually what is going on. But here is the way I wrap my mind around it.
When you draw a bow you feel a single resistance force. That force is made up of two reaction forces from the bow. The belly resists in compression and the back resists in tension, and they sum to the total resistance force.
The force you apply to a bow is evenly distributed throughout the back and the belly. But if a wood is tension strong, you need to apply a large force to overcome its tension resistance. Since the load you apply is balanced on the back and the belly, you need to apply that same high force on the belly. By doing this you are blasting right through its compression limits and causing set.
By trapping the back, you are reducing the force you need to apply to overcome the wood's tension resistance, bringing it closer to the wood's compression threshold. So now when you draw the bow, the compression and tension resistances are balanced and you are not overstressing one or the other.
-
<snip>That's why your having problems,your not using real bow wood...try some osage ;)
I thought we'd all decided to switch to Poplar???... ;) :o ::)
OneBow
Nope....just Ryan ;)
-
Surely you mean trap the back, not trap the belly? Ash is tension strong, not compression strong. Trapping the back works excellently with ash, whereas rounding (essentially trapping) the belly into a D section for instance, causes set, chrysalling and sometimes breaks.
I do indeed stand corrected. When reading the comments, I visualised a trapped belly - possibly because I plan on rawhiding the back and maybe it was mentally "off limits" to me.
http://www.primitivearcher.com/smf/index.php/topic,39032.0.html
-
Well... I might try this. Cool idea Jon!