Author Topic: Penobscot (exploring the puzzle) SUCCESS (Read 35128 times)

half eye · « **Reply #60 on:** December 26, 2015, 10:46:43 am »

Well guys, the model is no more. it went away at 60+ @ 23 when a backbow cable string went away at a defect....I did pictures of it at brace w/ closeups. Thats the first 3 pictures.....then there are 4 pictures of the aftermath....it is clear that the flat cable broke where it had been previously bent while dry (I believe).

I find the break dynamics interesting on the mainbow limb, because it helps to show just how much strain the cables are under....anyways it's on to the real deal now....and while I'm going to use the flat ends slit method I believe that I will twist the cable in-between the bow tips. The thought being that perhaps the twisting will help with flat strip weak points....anybody got any ideas on twisted VS: flat strengths I'd be glad to hear about it. Another observation is that the break the good limb had the exact profile as it started....and even the broken limb had the same shape.....for as skinny as everything was I am pleasantly surprised. I really believe that if the caqble had not broken that baby would be flinging arrows as we speak.

Any questions please ask....2 sets of pics.
rich

half eye · « **Reply #61 on:** December 26, 2015, 10:47:42 am »

second set

Oglala Bowyer · « **Reply #62 on:** December 26, 2015, 11:52:41 am »

Man, sorry to hear that Rich. It was looking real sweet too. If it's any consolation to you I had two gull wings give way while tillering yesterday and the day before. I feel ya $:-\$

bowandarrow473 · « **Reply #63 on:** December 26, 2015, 12:30:06 pm »

Shame that it had to go, I was looking foreward to seeing the finished product!

half eye · « **Reply #64 on:** December 26, 2015, 12:55:00 pm »

Oglala, hey man no biggy....it was just the experimental model....just about ready to strat stringing up the "real" bow....just hope I can get 'er up to your weight range

Bows....No issues on the real bow we'll get her shootin here shortly. This just part of the learning curve. Really these hiccups are the reason I do the experiments in the first place....part of trying to understand why these fellas did what they did.....it dont tell ya for certain but you can come up with some common sense reasons for why they might have done things a certain way.

rich

willie · « **Reply #65 on:** December 26, 2015, 05:24:30 pm »

Rich

just a hiccup you say? I will bet you already had the next one designed before the break.

on twisting....

in general, twisting induces friction between strands, and reduces the amount a string or rope has to be "overbuilt" in order to work to "rated" load in actual practice. the trade off is that twisting increases elasticity. Ropes can be sized by desired elasticity instead of actual tension strength limits. Is the next design going to depend on the rawhide to do the work of the back?, or is it just acting as a theoretically unstretchable tension member to transfer the actual work to the back bow?

half eye · « **Reply #66 on:** December 26, 2015, 06:20:48 pm »

Willie,
I'm glad you brought that up sir !!!! I noticed at 23" before she blew that I wasn't getting that rusty hinge sound. Before with the flat straps you hear them "groan" as they stretched so when that stopped I should have too. There are a couple reasons why I got myself in this situation.....

1. the model bow was really short by the original standard, and then to top that off my back bow was too long....Should have been 1/3 length not 1/2.....what that did was make the backbow string VERY short on working length. While the strap failed the bow did not....we are talking a 3/4 to 7/8 inch wide stick pulling over 60# at nearly half it's length.....cant figure out why that dont work duh

2. If I had paid more attention I would have realized that I had wrapped the grip area to 20" (increased the draw weight)....but at the same time I took all the working area from the backbow limbs so I basically made it fail.....the lesson here is ya got to have give in the backbow limbs if the strips are short....or you have to have longer strips/ strings if the backbow does not have working limbs.

I'm quite sure that had I made it right the rawhide would not have broken. Since Oglala wants high weight and the no limb backbow style, I believe I will partially twist the cords even though the flats would work fine being 5-6 inches longer. By big take-away from this is....the design is great but the bowyer is an idiot

rich

Buckeye Guy · « **Reply #67 on:** December 26, 2015, 09:20:56 pm »

Sweet prodgect you have here Rich!
keep up the good work

half eye · « **Reply #68 on:** December 27, 2015, 07:13:04 pm »

Thought I'd update the progress through today. The 2 bows are steamed to shape, and they only need to be finished sanded and greased prior to binding them together. Also the backbow will need to be shortened slightly depending on what tips I decide to carve.

I took one of the 10" elk rawhide circles I cut earlier, soaked it and cut into a 3/8" wide strap that came out to over 14 feet long. That I doubled over and twisted for a bow string over 6 feet long. It has a slide loop on one end so I could stretch and twist it and was tied in a simple knot so I could lightly stretch it our over night to dry.

I also took one of the remaining buffalo hide 1/2" strips and did a twisted cord with flat ends. the idea is that I can check if I like that or not. If not I can twist up another elk hide string for the back bow.

Judging from the mainbow string, I should be able to cut a second 3/8" strip from the remaining circle and use that for the complete two bow wrap.

What remains now is simply sanding the bows, cutting the knocks, coat them w/ pitch?grease....and then assemble the bow. Enjoy the pics....if any questions please speak up.
rich

burchett.donald · « **Reply #69 on:** December 27, 2015, 08:15:47 pm »

Looking sweet Rich...Can't wait

The twisted rawhide looks good from here...
Don

half eye · « **Reply #70 on:** December 27, 2015, 08:19:57 pm »

Thanks Don, I may need to get with Mr. Oglala and see how they should be twisted up, mines ok but not as uniform as I would like.....either I aint doin it right or I need a whole bunch more practice

rich

half eye · « **Reply #71 on:** December 29, 2015, 05:56:50 pm »

OK got caught up some...got the bows (2) tied together with elk rawhide. The smaller bow is one I'm putting together for testing and fun etc etc. The grip wrap dried up faster than the larger bow so I went ahead and tied up the tip to tip cables....these are buffalo rawhide utilizing flat ends then twisted to another flat end.

I will need to fit Joe's bow with tip to tip strings next....once dry I will string both up and final tiller while at brace....and check the draw weights....I'm thinking that Joe's may be too light maybe 60# but we'll see.

Next post should have some those money shots ya all like. These pics will be 3 posts and have some closeups but if any questions just let me know.
rich