boo backed acacia rd bow my 6th try

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Preston
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boo backed acacia rd bow my 6th try

#1 Post by Preston » Sat Jun 11, 2016 2:45 am

I haven't been active on any forums for a long time but I was busy building and learning all I could
I started off with board bows and got bored with them...so I tried boo backed acacia bows
After 5 of them I got the last three done OK.....
I'm still learning got a lot more to learn and I love the rd bows they look awesome and I still have got to get the hang of tillering them correctly....please see the pics of my last attempt and feel free to criticise and point out any errors...
Thanks
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rodlonq
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Re: boo backed acacia rd bow my 6th try

#2 Post by rodlonq » Sat Jun 11, 2016 7:19 am

I like it Preston. Very hard to pick out tiller issues with D/R bows. If it shoots quietly, thats usually a good sign. You bamboo has a long space between nodes, good find.

What poundage is the bow in the picture?

Cheers... Rod

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Re: boo backed acacia rd bow my 6th try

#3 Post by Gringa Bows » Sat Jun 11, 2016 9:45 am

looks great

Preston
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Re: boo backed acacia rd bow my 6th try

#4 Post by Preston » Sat Jun 11, 2016 9:55 am

Its 33# at my draw length of 26". I was trying to make a 45# at my drawlength but I got a hinge near the fade on the bottom limb which i saw when i first strung the bow after using the long tillering string.....and had to drop the weight to correct it and save the bow!
Those long tillering strings cannot be trusted!!!!! Got to try a different approach with the next one I make as this is happened to me too many times..... :(
Yes its very quiet and definitely faster than my board bows its also smooth to the draw...so I'm actually quite pleased with it....

Rhino1
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Re: boo backed acacia rd bow my 6th try

#5 Post by Rhino1 » Sat Jun 11, 2016 12:04 pm

Thats a gorgeous bow, well done
"As far as I can tell my place is right here, on the smart end of this rifle" H.Glass-Revenant.

Preston
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Re: boo backed acacia rd bow my 6th try

#6 Post by Preston » Sun Jun 12, 2016 12:09 am

Thanks for your compliments! Its encouraging. I will be starting on another one soon and hope to get a bow of around 45# @ 26". I have enough glue for two bows possibly 3....by which time I hope to get it right....wish me luck!!!!! :)

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greybeard
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Re: boo backed acacia rd bow my 6th try

#7 Post by greybeard » Sun Jun 12, 2016 2:06 pm

Preston wrote:..........but I got a hinge near the fade on the bottom limb which i saw when i first strung the bow after using the long tillering string.........
Preston,

From the first photograph the nodes appear to be just outboard of the fade area.

As nodes usually create a stiffer spot in the limb they become more of a tillering issue when in close proximity to a rigid riser. Bows that bend through the handle are usually less prone to this happening.
Preston Bow.jpg
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Preston wrote:.......Those long tillering strings cannot be trusted!!!!! ........
I have mentioned this in other posts that I do not trust the long string and as to why.

If I need to use one it is only until the bow is bending satisfactorily to slightly past brace height and then I use a string of the correct length.

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

Preston
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Re: boo backed acacia rd bow my 6th try

#8 Post by Preston » Sun Jun 12, 2016 9:08 pm

Hello Daryl, thanks for your valuable insight....yes the nodes too close to the riser is a problem...for me to make a 66" ntn bow with the boo I have, I will end up like this because of the way the boo was cut....to avoid this problem I can increase the riser length and treat this portion as part of the non bending area..... Or design the bow about 62" in length....which will bring the node in the center of the same length riser...what do you think would be better?
Thanks for taking the time to help me find the problem.....I never thought of the node placement contributing to my mistake....and I do need to stop using a long tillering string earlier in the process and switch to a short string...

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Re: boo backed acacia rd bow my 6th try

#9 Post by greybeard » Tue Jun 14, 2016 10:31 am

Preston wrote:.......to avoid this problem I can increase the riser length and treat this portion as part of the non bending area..... Or design the bow about 62" in length....which will bring the node in the center of the same length riser.......
Preston,

Although possible, either of the above options will result in shorter working limbs which could change the bows effective draw length and overstress the limbs.

I would try a smaller riser similar to a longbow riser with longer fades to just past the nodes to help spread the load. If done correctly you should be able to get some bending through this area without creating hinges.

In the following photo you may notice that the nodes are off centre and the fadeouts are not symmetrical. The fades taper past the nodes and then blend into the limbs. By doing this I was able to avoid hinges and keep the bow in tiller.

The bamboo backing is not as thick as it appears in the photo; this was a result of the camera angle.
Handle Section.jpg
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It is difficult to see the ratio of bamboo to timber in your photos but too much bamboo will over power the timber, especially around ‘ramped’ nodes.
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Although wasteful another alternative would be to cut two pieces of bamboo at suitable nodes and splice them over the handle. Maybe the off-cuts could be joined to make children’s bows.

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

Preston
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Re: boo backed acacia rd bow my 6th try

#10 Post by Preston » Tue Jun 14, 2016 2:17 pm

Daryl thanks for the advise I'll think about it and make a decision....the boo I used had very high/thick nodes after flattening the boo evenly with the thickness between nodes a bit under 1/16" I still ended up with the boo being a bit too thick at the nodes if I reduced the thickness there I would have had a kind of cup shape under the node and possibly have a bad glue line...so I left it like that...would it have been OK to reduce the thickness there? I don't know!
I measured the boo with a node falling between the fades and the boo is too short only about 58" so I will have to increase the fades as you have suggested.....I'll decide soon and continue with my build and definitely post some pics of my progress....,once again thanks for your help.

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Re: boo backed acacia rd bow my 6th try

#11 Post by Preston » Mon Jun 20, 2016 1:08 am

Hello Daryl
I ended up cutting the bamboo in the center and joining the pieces together to get a 66" ntn bow....I just done the glue up today. I reduced the belly thickness of the acacia and I'm not sure what DW to expect it should be about 30 to 40# max......I'm not worried about that !!!! Just would like to get it tillered properly....rd bows are new for me and its hard to know where to concentrate my efforts while on a long string....
If I reduce the outer portion to get it to brace I run the risk of whip ending it when I change to the short string and if I get it bending closer to the fades to midlimb it may develope a hinge when I go to the short string both situations have happened to me before!!!!
Any advice to get it right will be much appreciated.....
Thanks.

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Re: boo backed acacia rd bow my 6th try

#12 Post by greybeard » Mon Jun 20, 2016 9:46 pm

Preston,

I have made a couple of deflex/reflex laminated glass bows that come off the form basically tillered so unfortunately I can not offer you advice from personal experience on the bamboo/wood combination.

My own view is that the deflex/reflex design is a poor choice for a bamboo backed wooden bow.

As you are aware selfbows and bamboo bows can be prone to string follow which can have a detrimental effect on performance; building in deflex only adds to this problem.

This loss has to be compensated for and you only have the reflexed limb sections to recoup these losses.

You need to design a bow so that when it is tillered it takes on the deflex/reflex profile whilst maintaining high string tension at brace height.

There may be other bowyers on this site that can assist you.

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

Preston
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Re: boo backed acacia rd bow my 6th try

#13 Post by Preston » Tue Jun 21, 2016 1:31 am

Daryl from what I read the deflex part is to help with accuracy and smooth out the bow at release and the reflex to keep early draw tension good. With just reflex we get good early drawweight but its more difficult to shoot straight with the bow being a bit rough at release.
I did build reflexed bamboo backed bows before and from experience I can say they are more rough and a bit noisy but the rd bows are definitely smooth while drawing and don't jerk at all on release moreover they are whisper silent.
The bow I am making now is tillered and the tips are about 0.75" forward of the back of the handle after resting and it defiantly shoots faster than my board bows....it came in light 28# @25" but I'm happy with the progress I'm making...I've learnt a lot so far and slowly creeping up on a design that I can reproduce anytime I want to make a rd bow....my next one will defiantly hit the draw weight I want....which is at least 45#@25"
:)

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Re: boo backed acacia rd bow my 6th try

#14 Post by greybeard » Tue Jun 21, 2016 9:34 am

Preston, it is good news that you are getting this style of bow working for you. :Bow

If possible can you post photos of the bow unbraced and braced?

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

Preston
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Re: boo backed acacia rd bow my 6th try

#15 Post by Preston » Tue Jun 21, 2016 3:22 pm

Here is my last 3 tries unbraced....
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Here they are braced.....
rps20160621_104704b.jpg
rps20160621_104704b.jpg (99.76 KiB) Viewed 7423 times
The unfinished bow is the one I tillered yesterday.....let me know your thoughts....
Thanks.

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Re: boo backed acacia rd bow my 6th try

#16 Post by Preston » Fri Jun 24, 2016 12:46 am

Hello Daryl...what do you think does the unbraced profile match the braced one? Waiting to hear from you.
Thanks

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Re: boo backed acacia rd bow my 6th try

#17 Post by greybeard » Fri Jun 24, 2016 8:32 pm

Hi Preston,

Looking at the unbraced bow is the amount of deflex similar to what was built into the bow or did you get some string follow?

Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken.
[Ascham]

“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]

I am old enough to make my own decisions....Just not young enough to remember what I decided!....

Preston
Posts: 68
Joined: Sun Jan 04, 2015 4:54 am

Re: boo backed acacia rd bow my 6th try

#18 Post by Preston » Fri Jun 24, 2016 11:32 pm

I glue in some deflex and a bit more reflex, after shooting the bow for sometime over a couple of days the bow settles into the profile you see in the pics...there is definately some string follow over the whole length of the limb though I try to minimise it as much as possible.

Sometimes I wish I had a chronograph to check the arrow speed with all the various designs I've tried so far!!!! As of now I shoot for distance and compare my bows that's how I know my rd bows are shooting better than my board bows of comparable weight with the same arrow.

I am trying to get some Ipe as I've read many nice things about bamboo backed Ipe bows....I will be able to make bows in a higher draw weight range.... :(

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