Author Topic: First r/d has compresion fractures help  (Read 11689 times)

0 Members and 1 Guest are viewing this topic.

Offline Jesse

  • Member
  • Posts: 2,127
First r/d has compresion fractures help
« on: April 05, 2007, 01:10:29 am »
OK. after about 120 more shots a problem has shown up. Compresion fractures on both limbs the entire length. They are barely visible and the bows performance is still right on the money but I don't know for how long. I was thinking about sanding the belly flat and gluing on a thin fiberglass lam. Any thoughts on that? The bow is the one I just made and had posted. Its boo backed ipe 55# @ 27 " The boo was too thick I think. The bow may also be too thin 1 1/4 at widest evenly tapered to 1/2 inch at the tips. This bow shoots awesome and I put a lot of time into it. I really want to save it. Any suggestions? You can see them in the right light . not cracks but the wood has slight bumps on the surface now I can feel them a little bit if I run my finger over them.
« Last Edit: April 05, 2007, 01:25:23 am by WIBOWYER »
"If you can find a path with no obstacles, it probably doesn't lead anywhere."
    --Frank A. Clark

Offline Badger

  • Member
  • Posts: 7,940
Re: First r/d has compresion fractures help
« Reply #1 on: April 05, 2007, 03:10:48 am »
Your demensions are good, if it is showing compression fractures in one area of the limb you just had that area working a bit too much, very easy to do on a r/d design. Depending on the length of the bow I would consider getting the other areas of the limb bending a bit more and if you have to shorten it a tad go for it if it is long enough. Steve

Offline Jbell

  • Member
  • Posts: 256
Re: First r/d has compresion fractures help
« Reply #2 on: April 05, 2007, 09:02:23 am »
Hmmm, that is strange, does'nt look like like chrysals. I went back and looked at your full draw pic and if any thing your not bending to much in the pic your showing us, so if what you are showing us is the begininnings of compression fractures your boo must be way to thick. How thick is it? If you think it is to thick then I suppose the solution would be to sand the belly flat and trap the back of the boo. I would'nt do the fiberglass thing, if you trap the boo and sand ridges out and lose alot of draw weight you could turn this into a tri-lam and glue up another thin piece of IPE. Good luck, someone else may have a better suggestion than mine, I have made quite a few boo backed bow but not with IPE and had a problem with a chrysal in black walnut once but that was because of a hinge. Justin
Justin Blunt

Offline Jesse

  • Member
  • Posts: 2,127
Re: First r/d has compresion fractures help
« Reply #3 on: April 05, 2007, 10:06:10 am »
here is a pic. of the area with the most noticeable problem. I didn't realize the ipe would get so thin.
"If you can find a path with no obstacles, it probably doesn't lead anywhere."
    --Frank A. Clark

Offline Badger

  • Member
  • Posts: 7,940
Re: First r/d has compresion fractures help
« Reply #4 on: April 05, 2007, 12:52:41 pm »
If it is too narrow in that spot in can still get compression fractures without looking like it is bending all that much. Probably could have just spread the bend out a little more. I t may hold up fine just like it is, I have had several bows with shallow compression fractures that held up for a long time. Steve

Offline Jesse

  • Member
  • Posts: 2,127
Re: First r/d has compresion fractures help
« Reply #5 on: April 05, 2007, 01:30:22 pm »
Thanks. What is the downside to the fibergass on the belly? Besides the fact that its fiberglass? I don't care much for fiberglass thats why I made a wood bow but I would rather have a good working bow with glass on the belly than a failing bow thats all wood. I'm only asking because I don't know. You guys have probably tried this and have a reason it wont work good. Thanks again   
                                         Jesse
"If you can find a path with no obstacles, it probably doesn't lead anywhere."
    --Frank A. Clark

duffontap

  • Guest
Re: First r/d has compresion fractures help
« Reply #6 on: April 05, 2007, 02:23:26 pm »
We try hard to keep from even talking about fiberglass but that's not because it doesn't work.  We are all trying to solve problems with natural materials so that's why we don't resort to fiberglass.  One nice thing about natural materials is that they tend to be affordable so you can just rebuild that bow and adjust the dimensions, boo thickness and tiller to avoid the problems you're experiencing. 

         J. D. Duff

Offline Jesse

  • Member
  • Posts: 2,127
Re: First r/d has compresion fractures help
« Reply #7 on: April 05, 2007, 03:01:15 pm »
I understand. I wouldn't make a bow with glass in the original plan but I'm not very good at making wood bows yet. I will change my next one a bit so I don't resort to cheating. I just wanted to know if it would work good. but you are right this is primitive archery. 
    Very Nice cradle by the way.       Jesse
« Last Edit: April 05, 2007, 03:09:42 pm by WIBOWYER »
"If you can find a path with no obstacles, it probably doesn't lead anywhere."
    --Frank A. Clark

duffontap

  • Guest
Re: First r/d has compresion fractures help
« Reply #8 on: April 05, 2007, 03:50:49 pm »
Thanks, I build bows too.   ;D  I've got to start posting bows again.

                 J. D. Duff

Offline Justin Snyder

  • Administrator
  • Member
  • Posts: 13,794
Re: First r/d has compresion fractures help
« Reply #9 on: April 05, 2007, 05:34:21 pm »
Those look a lot like tool marks to me. Some times the scraper starts skipping and makes a washboard surface on the really hard woods. You don't really notice until you get the polished finish on them. I have an osage and a purple heart that look like that without being shot. I guess I haven't seen compression fractures on any of my bows yet though so I couldn't say. Mine usually have problems on the back.  ;D Justin
Everything happens for a reason, sometimes the reason is you made a bad decision.


SW Utah

Offline Pat B

  • Administrator
  • Member
  • Posts: 35,982
Re: First r/d has compresion fractures help
« Reply #10 on: April 05, 2007, 07:03:58 pm »
Look at my "What to do" post. Basically what I did was ground down the faulty belly and added another. You could add more ipe or osage or another tough in compression woods. I would also trap the boo backing to releive some of the tention stresses.
   That ipe looks light in color to me. I have never seen it that light. The little I have dealt with was so dark you could hardly see the grain.    Pat
Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline Jesse

  • Member
  • Posts: 2,127
Re: First r/d has compresion fractures help
« Reply #11 on: April 05, 2007, 09:02:22 pm »
I was wondering if it could be tool marks. I tillered it with a pocket knife. I would think I would have noticed it sooner though.
 The ipe looks lighter in these pics but you can see the grain. Ipe Im told is a name that covers many different trees from the same family.
 looks can vary from one to another.
                                    Jesse
"If you can find a path with no obstacles, it probably doesn't lead anywhere."
    --Frank A. Clark

Offline venisonburger

  • Member
  • Posts: 1,042
Re: First r/d has compresion fractures help
« Reply #12 on: April 05, 2007, 10:16:00 pm »
Jesse, a fret will look like a fine crack, I wonder if like said above they aren't just your tool marks. watch the area and see.
VB

Rich Saffold

  • Guest
Re: First r/d has compresion fractures help
« Reply #13 on: April 06, 2007, 02:01:28 am »
I too think those are tool marks Wibowyer..when you have that high ratio of bamboo, and frets, often the problems could be much greater..If the tiller is holding and the bow is shooting fine then don't worry.

On these bows when I get the bow floor tillered, I sand it smooth so any possible "washboard" is gone during final tillering. also its easier to see the subtleties in the bow when final tillering..

And while it can be nerve wracking thinking something when wrong..remember this bow is probably the first of many you will make, and each one can be an adventure no matter what the skill level..Like mentioned there's 100 species of this tree, and they all work, so each board is going to be different, and this is much more interesting and challenging than if they were all the same.

Yesterday i found what is probably the only ipe tree growing in our area..now I have to sneak back at night with my folding saw! ;)

Rich