Trad Gang
Main Boards => The Bowyer's Bench => Topic started by: BFreed59 on June 24, 2015, 10:28:00 PM
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So I have been working on a Bingham bow, and I have developed a severe limb twist, and not sure how to fix it. I have searched on here and found the picture showing to deepen the nock on one side and to remove wood to mid limb on the other side.
(http://i.imgur.com/wseCMaw.jpg)
Am I right in thinking that for this picture I would need to remove the wood from the right hand side of the limb??? Which is what I have tried but the twist seems to get worse when I do that and am getting to nervous about doing anything else.
So my question is what can/should I do to fix this limb twist? Or is it even fixable?
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I dont have much experience in the glass stuff but twists are a dam nuisance for sure. I hate 'em. :(
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Assuming this is glass in an epoxy resin:
You could try running the limb under very hot water in the kitchen sink and twisting it back. You will probably have to over compensate because of spring back. Once it is twisted back into shape and still hot, run cold water over it to set it. Most epoxies will start to soften around 125°F. Soften it, bend it, set it.
Make sure the bow is not strung when doing this. That is why bow makers will not warranty a bow if the damage is caused by leaving it in a hot car. Also epoxy can sometimes cold creep, that's why you shouldn't leave an unstrung bow resting on its tip in a closet like it is a broom.
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Hily Cow that's some twist! Is this your first? Reason I ask is that with takedowns especially, it's really easy to get the pin and bolt holes just a tiny bit off causing the limb to be way out of alignment which will cause the problem you have right there. Have you checked to make sure that everything is in perfect alignment?
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Yeah this is my first build, I thought the alignment was good but it may be off some. I was wondering if the lams got warped before glue up if that could be contributing to it. I put everything in the oven then let them cool back to room temperature and the parallel was pretty warped.
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That's some twist allright, is your bow form correct, with the surface you lay the lams on at 90 degrees with the sides?
Looks far gone to me and perhaps for safety reasons it should not be used. Most annoying when things go wrong.Bue--.
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That is most likely an alignment issue. The methods that utilize heat, groove deepening, and removal of edge material may not be enough to correct a misalignment due to misplacement of alignment pins and/or threaded inserts.
Did you try to switch the limbs, bottom to the top position, top to bottom? Doing so may improve the alignment or help deduce whether it's a hardware alignment issue or a problem within a single limb.
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How does it look unstrung if you run a tight string or use a laser beam from tip to tip?
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Here is a look at it unstrung with a string on it just enough to keep the string straight. The limb with the twist is the one closest in the picture.
(http://i.imgur.com/DVMmuVM.jpg)
And one from the string side. In this picture the problem limb is the farther one.
(http://i.imgur.com/kzKghjX.jpg)
I will check my form to make sure it is square, but if the form was not square shouldn't both limbs be twisted? Instead of just one?
I will also try to flip the limbs around and see if that does anything.
And I was kinda thinking along the same lines of not being very confident with shooting it even if I am able to fix it
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Sure looks like a limb alignment problem in those pictures.
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Is there anyway to fix an alignment issue, or would it be best to just start over
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Try using a different string, like a Flemish twist string. Then work from there. The limb pads need to be Square with the limbs too. You might be able to glue a hard wood dowel into the holes and redrill if needed?
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Robert- what effect does a Flemish twist string have for fixing a twist? I'm still new to this and don't see how that would help, but I'm sure there is a reason. I will make one up tonight and see of if helps any before moving on to other methods.
Thanks for all the help so far, any other input would be greatly appreciated
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I'm not sure what I am seeing..is that a paracord string you are using? the large diameter and large twists near the loops concern me. For tillering in my shop I like to use a nice fast flite flemish twist string with evenly made loops. One of my friends makes nice strings for me when he has time. there are several vendors on tradgang that also make quality strings.
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how wide are your tips at the string groove? how taper did you use in limbs? I usually taper the limb edges starting 3 inches past the end of the fades to 5/8" wide at the string grooves.. you may have plenty room to adjust limb center if the limbs are still wide at the string grooves..I use thin 120# spiderwire type of fishing line to check limb centers
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In the pictures other than the first one it is paracord just show how things line up there is no tension on it and i'm not using it for anything other than those pictures. The kit from Binghams came with two continuous loop strings both 16 strands of B-50. One of which is shown in the first picture on the bow when it is strung.
And the limb tips are 7/8" at the string grooves
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Looks to me like the riser was the start of your issues although it could just be the pictures. The pads don't look like they are at 90 degrees. In the one pic the closest limb si sitting flat on your railing but the riser looks twisted, if it is that would tell me the pads aren't square.
Did you cut and sand the pads while you had a square riser block?
You might be able to save it but it's gonna take some work and some luck, might as well get another one started if you have an addictive personality! :thumbsup:
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Sorry friend, but it sure looks like either limb pads or alignment issue. My first takedown was like that. I ended up saving it by filling the alignment pin holes in the limb and re-drilling them. But you'll have to make sure those limb pads on the riser are absolutely, perfectly square first. Maybe save the limbs and make up a new riser, just to be sure it's not exclusively the pads?
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Looks like limb pads are not at 90 degrees. Easiest fix, make a new riser. You can cut you fittings out of old riser.
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Like someone said earlier, switch the limbs top to bottom and brace it again.
If the problem moves it is the limbs. If it is the same the problem is in the riser.
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From now on I'm not just going to assume that the tools in using are square, probably better to check just in case.
To cut the pads I used a radial arm saw so that I could get both pads cut to the same angle, I'm thinking that where it could have gotten off, if it is the riser, is if the blade was not a 90 degree angle or I didn't think to re-square the whole riser block after I glued it together into one block.
So I flipped the sides the limbs were on just to see if that changed anything, and now when I set it on my railing only one limb will sit flat. In the picture below the far limb which can't be seen is flat on the railing and the close limb is definitely not flat
(http://i.imgur.com/CyuxhUB.jpg)
I'm not really sure what that means since with the limbs attached the other way both sit flat.
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I would build a new riser and make sure everything is perfectly square get your inserts and pins centered and see how the limbs fit on the new riser.
Your limbs look pretty narrow and with them being out of alignment you may have taken to much material off one side already. You might be able to shorten the limbs and file new nock grooves but you won't know until those pads are square.
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If pads are not square could he shim the pad or limb with an overlay, then sand overlay to correct angle?...you might have to redrill the locater pin since it will be at a different angle if you shim..
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I check my saws and sanders continually during build for square. Just a degree out of square is an issue. Also I have found that riser blocks from Bingham or anyone else are not always square to start with. Make siue you start with a square riser block.
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So I strung it up with the limbs switched, and to my surprise it looks better, at least to me, it has some twist in both limbs going opposite directions. I used a Flemish twist string I made up last night, 16 strands of B50. How does it look to all of your more experienced eyes, would this be easier to deal with or just as bad?
(http://i.imgur.com/4qT4PUf.jpg)
And just for reference the closer limb is the one that had the bad twist before
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You could certainly get it 'shootable'. You will need to remove quite a bit of material and have some wide string grooves but you can get it shooting.
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Looking at the pic above tells you have an out of square limb form. Even though it looks like the riser is way narrower than the limbs the pads don't look to be that out of square. Also, if the limbs aren't in alinement with the riser it would exaggerate the twist in the limbs.
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Have you stretched a string end to end and checked where it hits on riser? Flip that baby over, clamp a strind at centerline on both nocks and note where it crosses the riser center.
The TDs I just finished, I did that to lay out limb centerline,bolted em on and ran the string. Without some fine equipment it's hard to get the limbs perfectly straight.
Then with a square, check the limb pads to side of riser if you haven't.
Then check the side to face of your form.
And my last bit of advice, go with a 3 pc TD D/R longbow! LOL
I have to really be cautious when doing recurves, the D/Rs are easier to get right for me.
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Originally posted by kennym:
Have you stretched a string end to end and checked where it hits on riser? Flip that baby over, clamp a strind at centerline on both nocks and note where it crosses the riser center.
The TDs I just finished, I did that to lay out limb centerline,bolted em on and ran the string. Without some fine equipment it's hard to get the limbs perfectly straight.
Then with a square, check the limb pads to side of riser if you haven't.
Then check the side to face of your form.
And my last bit of advice, go with a 3 pc TD D/R longbow! LOL
I have to really be cautious when doing recurves, the D/Rs are easier to get right for me.
Thats good to know about the D/Rs. One way I check risers other than the square is I clamp it in the vise and place small straight edges on both pads and eye them up. Sometimes a window works for truing up bows.
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So from everyones input, it looks like I have both an alignment problem and my form I out of square. My first bow has definitely been a learning experience.
I was hoping too pick your brains for a few more questions?
1. For my next bow, I'm trying to figure out what to build, would a one piece be easier than a takedown, and are long bows easier than recurves?
2. Is there a way to get my current project to be safely shootable? Without building another riser or set of limbs? Since I am a college student funds are limited.
Thanks for all the help
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One piece longbows are the easiest to build for me- look up the plans for a KennyM bow- they are nice shooters.
Have you figured out if your form is the problem (out of square) or is it the limb pads? If its the limb pads you should be able to salvage the riser.
Just another quick question- what is the width of your limbs at the nock, mid limb and the butt end?
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I checked my form and it appears to be square, but the square I was using is and old cheap-o square so not sure how reliable it might be, I will check again with a better square when I get the chance.
As for the limb width, at the limb bolts it is 1.5" and stays that wide till the middle of the limb length, then tapers to 7/8" at the string grooves
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The limb width has me wondering...are the limbs easy to twist when you string it up? narrow recurve limbs can have stability issues.
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They seem fairly easy to twist but I dont have much experience to provide a good reference too, but I am able to twist them to line up right, but they always come back to same place when back at brace after drawing a bit
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My .02 -- one piece longbows are cake compared to takedown recurves, especially if you're just starting.
You might save that bow if you fill the pin holes in the limbs and re-drill them. Fill them with a mix of super glue and sawdust, then sand flat. Bolt the limbs on and use the string method to line them up to center, like Kenny said. Then crank the bolts down tight and clamp if possible, and drill the new pin holes completely through the limb into the riser. You'll have to add an overlay to cover up the pin holes on top, but that's small stuff.
And another $.02, if you're going to use 1.5" wide recurve limbs, try using the ULS glass. It has another layer of glass fibers running cross-wise to help stabilize those narrow curvy limbs. Not saying it'll fix all the problems, but it should help. Otherwise, stick with 1.75" or 2" limbs.
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I have been making some good progress and was able to get it shooting. I pulled the alignment pins out put the limbs on and tightened the limb bolts way down, using a thin string lined the limbs up so the string passed directly over the center of both limb bolts and the center of the riser, I then held it in place using clamps and some shims on either side so the limbs wouldn't slide either way and strung the bow up to see how everything looked when strung. Once I was happy with that after drawing it a few times to make sure the string tracked good and came back to the same point I drilled new alignment holes through the limbs and into a new spot on the riser so it wouldn't jump back into the old holes. I then plugged the old holes using the high impact gorilla glue and a piece of an oak dowel. On the back of the limb I covered the new hole with a piece of glass I had extra so the hole didn't show.
Here are some pics of the progress and thanks alot to everybody that helped out. And a big shout out to Jess Stuart who has walked me through much of the process with about 15 emails between us, this is one of the reasons that tradgang is such a great place, the willingness to help and reach out to someone. I hope to be able to someday provide the same level of support that I have experienced here to new bowers on the future.
Here is a picture showing the alignment after about 10 shots without realigning the string at all this is just where it rests. Dont mind the pitiful shots
(http://i.imgur.com/5hlFDo1.jpg)
Another view of the alignment, this picture has the string Binghams supplied, the first picture is the Flemish twist I made that stretched out more than I thought it would reducing the brace height a bit, but I did shoot it with both strings and it lined up in the same spot.
(http://i.imgur.com/R05qEOH.jpg)
And here are two pictures of the bow so far,the tiller looks a little off but I will shoot it for a bit then decide if I want to work that out.
(http://i.imgur.com/RhkafZc.jpg)
(http://i.imgur.com/baIAyIK.jpg)
Thanks again for all the help!
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Tiller looks pretty good to my eye. Nice save sir!!
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Thanks, I was thinking that the bot to limb looked softer than the top, may that's how its supposed to be? But it seems to shoot good anyways so I probably wont mess with it
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Didja measure it? Most guys have it 0 to 1/8" stronger lower limb measured at fades(or end of riser is easier on a TD). I just quick checked the pic with a pc of paper, my long distance measure may not be the best! LOL
I have gotten to checking my limbs every 6" and trying to get them equal all the way, then carefully sanding the top limb a bit if I want positive tiller.
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I just measured it quick and it is showing a 1/4" negative tiller, I measured at the ends of the riser
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1/4 less on top? Larger measure on top is positive tiller
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Yeah the top measured less
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If it shoots good for you and as much as you narrowed the limbs. I think I would call it good. I hate to open a can of worms and this is my opinion so, take it for what it is worth. Just an opinion. Tiller measurement, is over rated and if a bow is quite and shoots with little handshock or buzz I let the tiller measurement be what it wants to be. Having said that I always check it and it usually is between even and 1/8" positive.
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So today I got to do a good bit of shooting with the bow and have to say I am happy with it, shot consistently for well over 100 shots today. Before I put a Flemish twist string and bear puff silencers on it it had a good amount of buzz when shot, but is nice and quiet after they were added.
Here are a few pics of the bow at the 3-D shoot I went to today, still have some work to do on the finish but otherwise I'm calling it done.
(http://i.imgur.com/tOvHu6P.jpg)
(http://i.imgur.com/wiPVwR8.jpg)
(http://i.imgur.com/isV5azw.jpg)
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Looks like you straightened that out quite a bit! Nice work.
If you want to straighten it the rest of the way you could try the hot water trick someone else mentioned. Might take some side sanding too, but you could get it perfect from there. You're very close.
Again, well done!
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Good job Brian, nice save and it is very easy on the eyes as well.
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Good save!