Primitive Archer

Main Discussion Area => Bows => Topic started by: alfaguy on June 13, 2019, 09:11:24 am

Title: String Not Along Centerline
Post by: alfaguy on June 13, 2019, 09:11:24 am
I have come by a Vincent Minor all bamboo bow with a serious string offset problem.  Holding it at arms length the string lines up with the right side of the bow. 

Can this be corrected by re-tillering it?  It is marked 58 lbs at 28 inches so can stand to loose a little draw weight.  I have problems with over 50 lbs.

Are there any other solutions to explore?
Title: Re: String Not Along Centerline
Post by: Pat B on June 13, 2019, 10:21:57 am
Is that how it lines up braced? Will you post a braced pic?
Title: Re: String Not Along Centerline
Post by: alfaguy on June 13, 2019, 10:48:05 am
It is braced in the photos.  Here are a couple more.
Title: Re: String Not Along Centerline
Post by: bjrogg on June 13, 2019, 12:50:26 pm
Hard to tell for sure from pictures on my phone, but it looks like if it was mine. In second picture I would clamp limb in vice and heat area about 7 to 9" from tip. I'm guessing that not measuring it. Heat a small area on belly and just by hand with a glove on  straighten that area up to line string up better.
What type wood is it?
Bjrogg
PS I'm thinking it's Osage and it will bend easy with a little dry heat.
Title: Re: String Not Along Centerline
Post by: bradsmith2010 on June 13, 2019, 01:27:17 pm
I think I would need to see it in person to make a judgement,,
would it be possible to turn it upside down,, re adjust the handle and shoot it so the string is over the arrow side of the bow,,
 )P(
try shooting it like that now,, and see how it does,, if it shoots good,, put the rest where it needs to go and re do the handle,, I have a feeling it will shoot ok like that,,then your done,,
Title: Re: String Not Along Centerline
Post by: Pat B on June 13, 2019, 01:47:52 pm
Vinson Minors boo back/belly bows used to have 5(I think)core lams, parallel across the limb with the boo back and belly. I have one of Vinson's bows similar to yours. With some glues a little heat could be used for minor adjustments. I don't know what glue Vinson used in these bows.
The only other adjustment would along the limb edges.
Title: Re: String Not Along Centerline
Post by: Eric Krewson on June 13, 2019, 02:22:05 pm
If it is glued with urac you can heat it, anything else may be questionable. Does it have a dark glue line?
Title: Re: String Not Along Centerline
Post by: bjrogg on June 13, 2019, 02:29:11 pm
Ignore everything I said. Don't know how I missed that all bamboo part.
Bjrogg
Title: Re: String Not Along Centerline
Post by: alfaguy on June 14, 2019, 09:47:12 am
I will check the color of glue lines tonight.  Turning the bow over is an option - the  previous owner was left handed so it worked fine for him. 

Would heating the lower limb work with the finish on the bow?  I can sand it off, but do not know what Vincent used to finish his bows to restore it back.

Title: Re: String Not Along Centerline
Post by: alfaguy on June 14, 2019, 10:22:57 am
The post on the Mechanics of Limb Twisting seems to offer a solution - remove wood from the belly on the strong side......
Title: Re: String Not Along Centerline
Post by: bradsmith2010 on June 14, 2019, 11:48:01 am
this is just me,, I wouldnt do anything until you see if it will shoot well,, with the bottom limb on top,,

then you can decide if you need to do anthing else,,


Title: Re: String Not Along Centerline
Post by: kbear on June 14, 2019, 01:31:35 pm
I am no expert in all-bamboo bows, but from what I do know - the bows aren't tiller-ed in the normal manner. The laminations (back and belly) are thickness-ed and profiled to predetermined dimensions prior to glue up. I am not sure how Vincent made his bows, the Japanese Yumi, and Chinese bows of similar construction were wrapped with cordage and had bamboo wedges applying pressure to specific locations on the back and belly to create reflex, curves etc. The bowyer would never quite know if the bow was going to be right until bracing, and subsequent shooting.

Minor adjustments can be made side tillering, but it is critical on a boo belly that the ultra-dense outside "shell" of the boo is not compromised, otherwise it will hinge horribly. Side tillering may or may not be an option on this bow, as it may weaken the side seam and cause a delam. Not really sure of Vincent's glues though....

Heat bending -hmmmmm ........ risky

Belly tillering - very risky

Side tillering - maybe, but may ruin the look of the bow and compromise the lams

Flip it - flip and reposition the shelf, maybe cut a little of the former top limb if the bow is asymmetric (that'll increase the poundage a little though.......). I think this'd be your best option.

I have always wanted to try this style of build......... Have to get good at regular self bows first......... Could be a ways off!

 (AT)
Title: Re: String Not Along Centerline
Post by: Hamish on June 14, 2019, 04:21:39 pm
 I would be very hesitant to tamper with the tiller or heat bend. Too many unknowns, glue etc.

I would first try nocking an arrow, then flipping it around to the opposite side. Compare the angle of the arrow to the side of the bow. That will give you a more accurate look at how much the string is off centre, in a practical sense. You can increase the brace height(within reason) and that will help to reduce the angle of the arrow to the bow.


How does the bow shoot? Try arrows with a weaker spine until the arrow goes consistently straight at what you are aiming at.


From memory Vinson was a pretty decent bowyer. I believe it wasn't until he overcommitted on orders that he got into a bit of trouble not being able to deliver a product in a timely manner. I'm not sure if taking deposits or upfront full payment was involved, sorry if I am incorrect I don't want to defame him. Whatever the reason he's not making them anymore, so you have a collectors item.

 Sometimes you just have to trust that a recognised bowyer has done all that they can with an unusually troubled stave that doesn't behave the way the normally do. The bow ends up being a compromise of sorts.
I have a second hand ebay bow from a well known maker of elb's from England, with a similar problem. Otherwise it is a beautiful example of his craft. Not ideal, and I would be disappointed if I brought it brand new, but it still shoots fine with correctly spined arrows.


Perhaps these bows were originally sold as seconds, at a reduced rate. If worst comes to worst and you still don't like shooting it, you can re sell it to a lefty.
Title: Re: String Not Along Centerline
Post by: bradsmith2010 on June 14, 2019, 04:47:28 pm
he mentioned the bow was originally set up for left hand, that is why the string is on that side,,,probably shot fine that way,,
if you took one of my bows made for right hand ,, and shot it off the left hand side,, it would not line up as well,,I usually let the string favor the arrow side a bit,, yes you could probably find a weaker spine arrow to shoot the way it is,, I guess that would just be personal preference,, I agree heating or scraping might not be the way to go,,,