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Main Boards => The Bowyer's Bench => Topic started by: Dan Landis on February 28, 2016, 05:02:00 PM
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Working on an osage self bow 65" TTT, 1-3/8" wide fades to mid limb then tapers to 3/8" tips . Bow is tillered to 28" and at my desired draw weight using the pulley system where you track the string hook. I have the handle mostly shaped, and have tried holding the bow with a high grip, low grip, full hand grip and nothing seems to make a difference. This is the first time that I made a self bow with the top limb an inch longer than the bottom. Any suggestions?
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Will you post some pics...unbraced, braced and full draw. The way the bow is drawn is different in your hand than on the static tiller tree.
Generally hand shock is because the limbs are out of time or the tips are too heavy. How heavy are your arrows. Light arrows absorb less vibrations.
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I too would like to see pictures before I offer much in the way of advice. Pictures of it unstrung, braced on the tree, drawn on the tree, and perhaps drawn by hand.
What's the draw weight?
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The arrows weigh arrows 570 gr. The top limb has a hump in it just above the fade. When pulling it on the tree the top limb was always about 1/2" ahead of the bottom one, but the hook followed the line real well.
Here's the photos:
(http://i1101.photobucket.com/albums/g433/DanLandis/P2280018_1.jpg) (http://s1101.photobucket.com/user/DanLandis/media/P2280018_1.jpg.html)
(http://i1101.photobucket.com/albums/g433/DanLandis/P2280019_1.jpg) (http://s1101.photobucket.com/user/DanLandis/media/P2280019_1.jpg.html)
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Missed the full draw one.
(http://i1101.photobucket.com/albums/g433/DanLandis/P2280022.jpg) (http://s1101.photobucket.com/user/DanLandis/media/P2280022.jpg.html)
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Jeff, weight is 53#
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The limb tips look awful thick to me, Dan.
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Top limb should bend a little more in the outer third... though NOT midlimb where the reflex is at brace... it's doing fine there.
I would either begin the width taper a little sooner off the flares, or tiller it a little more elliptical.
Regardless, both limbs could be narrowed and thinned some out near the tips.
Got a picture of it on the tree?
Oh, and after you work the outer limbs, open up your string grooves with a round file so the string can pivot in there throughout the draw. See how the string is kinked at the loop where it contacts the bow? You don't want that. The shape of the tip inside the groove should also allow the loop to be rounded/tear drop shaped, with no corners or edges that it can rub on.
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Roy, They measure 5/8" at the tip and taper to 3/8" in about 5".
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Roy, They measure 5/8" at the tip and taper to 3/8" in about 5".
Are you saying the end of the tip is 5/8th and then they narrow to 3/8th in towards the riser direction?
I do a straight taper from a little outside the flares to my tip ends, which are 3/8th to 1/2 wide at the most.
And as Jeff said, the outer 3rd of the top limb looks a little flat.
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Jeff, will get a pic on the tree tomorrow.
Roy, Yes, 5/8" tapering to 3/8". I usually let them thicker so I have more to work with when I do the tip overlays, and thin everything down after the overlays are shaped.
I'll give the outer 1/3 of the limbs more width taper and re tiller.
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Your handshock in this cause is because of the tiller.
The real key to this bow making lark is to understand the difference between a pyramid width taper and a parallel width for most of the limb then taper into tips and how your width taper determines your tiller shape.
Bows need to taper somewhere - thickness or width.
A pyramid bow does all of its tapering in width and therefore needs very little thickness taper.
A bow that has parallel width limbs for most of its length obviously isn't tapering in width so it has to have all of its taper in thickness.
These two bows should have a completely different tiller.
The other thing to consider is that any given piece of wood can only bend so far before taking too much set. Make this piece of wood thinner and it can bend further, thicker it can only bend to a lesser degree.
So the pyramid bow has very little thickness taper - It should bend in an arc of a circle.
The other parallel width limb bow will have plenty of thickness taper - the thicker wood near the handl;e can't bend as much as the wood further along the limb (thinner) so that bows tiller should be elliptical.
If you apply this logic to every wooden bow you will never get that handshock.
Tiller is dictated by the width profile you choose right at the start.
So without seeing how your bow tapers in width nobody can really tell you about how to change the tiller other than to match one limb to the other.
Honestly though your handshock is not to do with your tips. I've done experiments where I purposely left the tips large....with perfect tiller guess what - no handshock. Knock the tiller off and ....handshock!
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Look like a tiller problem. You have a hinge at the left part of the cross. Mark an x there to leave that spot alone. Retilelr above it which is to stiff anyway.
Adjust the bottom limb so it is a little stronger than the top.
Bottom limb is right on. Match the top to it.
Jawge
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Basically what Roy says
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Fat tips don't cause hand shock. Poor limb timing is responsible for 90% of it. It looks like the bow tips forward. Get that flat spot worked over on the top limb and I bet your hand shock is gone.
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Thank you all for all the responses. I re-tapered the front profile, started the taper 10" from the fades. I also removed some wood from the outer third. Pics to follow. The adjustments so far have helped, still not gone, but much better. The neighbors think I'm a little strange shooting a bow in the dark, oh well.
First pic shows bow on tree, second shows before the adjustments made tonight, third shows after tonight's adjustments.
(http://i1101.photobucket.com/albums/g433/DanLandis/P2290023.jpg) (http://s1101.photobucket.com/user/DanLandis/media/P2290023.jpg.html)
(http://i1101.photobucket.com/albums/g433/DanLandis/P2290024_1.jpg) (http://s1101.photobucket.com/user/DanLandis/media/P2290024_1.jpg.html)
(http://i1101.photobucket.com/albums/g433/DanLandis/P2290025_1.jpg) (http://s1101.photobucket.com/user/DanLandis/media/P2290025_1.jpg.html)
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Looking better, Dan. Only thing I see is it's a little flat out of the flare on the limb to the right and then all the bend seems to start where I have the arrow pointing down, and a little bit flat about a foot in from the limb tip on the right limb. Maybe others see something I don't..
(http://i47.photobucket.com/albums/f165/ROY-CHRIS/dan.jpg)
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Don't do anything to fix that spot Roy pointed out, there's a natural hump there in the unstrung bow. It SHOULD look like that.
Handshock is due to limb timing issues more than any other factor.
This is an odd shaped bow, so it offers additional challenges.
See how, in the unstrung profile, the handle is angled a little bit?
Did you shim the handle in the cradle to do any leveling, and if so, to level the handle or level the limbs, or...?
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On that right limb, perhaps a few scrapes mid limb on would help.
As you draw the limb by hand, check to see if the handle pressure is even and if the limbs are tipping or not.
Remember that hand shock is relative.
I remember helping a friend make an osage bow.
I thought the bow was quiet and gentle. He thought it was shocky.
It was the first selfbow he shot and he came from FG bows.
Jawge
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Jeff, yes, the cradle is tilted a little to level the bow.
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Dan, that COULD lead to imbalance(and shock) when shot by hand, that is, if you don't 'heal the grip' enough to mimic what the tree is doing.
Try taking the shim out, or out enough that the grip itself is perfectly level, then draw the bow on the tree and take note of any difference in how the hook tows the line, or not.
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Thanks Jeff, I'll re-adjust to level the handle and see how it tracks.