Bamboo backed selfbow

[Selfbowman]

DC I do know bamboo is very strong !!!!! I was just wondering if you guys have figured out a formula for boo - Osage in tension using a average Density for comparison . Alan where are you. Y’all might not even know what I am trying to say. Not the best at explaining what I am thinking. :-\Arvin

[DC]

I wasn't asking if it would work the same, because it will (as you note). I was asking if using a tapered belly lam avoids the problem with the rules.


Mark

I think the rules say a backed bow is one lamination(the back). Any more(a power lam or third lam)bumps it up to complex. The subject came up because I had put a short lam across the handle to reinforce the splice and it was thought that might bump it up.

[DC]

DC I do know bamboo is very strong !!!!! I was just wondering if you guys have figured out a formula for boo - Osage in tension using a average Density for comparison . Alan where are you. Y’all might not even know what I am trying to say. Not the best at explaining what I am thinking. :-\Arvin

I'm pretty sure I understand what you're doing. I'm also pretty sure that the density of boo drops as you move from outside to inside. How much I don't know. I've thought about doing the same thing you are but I wasn't using a dense belly wood so I never acted on it. I'm thinking that Yew is lighter than any part of the boo. I'm making a boo backed Ocean Spray at the moment. This may be the combo that could use thick boo because OS is heavier than Bamboo. I had no idea how much OS to use so I just went with thin boo this time to see how it works.

[Selfbowman]

Ok DC here it is glued up setting on the caul. Now how good of a bow tiller am I??

[Selfbowman]

Here it will t is on my previous caul.

[JW_Halverson]

THIS was the year I could afford to go to this event, doing everything on the cheap like camping out of my vehicle, eating out of a cooler, and not playing the fool in the casinos....and along came Covid-19. I am in a higher risk category and I kinda have to be kinda careful.

Lemme just wish you luck from here.

[Bob Barnes]

If you have a warbow shooting friend...get out the boat winch and put a string on it... LOL  I could only venture to guess at how heavy that bow is right now but I'd say way more than anyone could ever draw.  Bamboo backing PLUS the power the glue line creates is like a modern bow with natural materials...and hard to beat.   

[DC]

Ok DC here it is glued up setting on the caul. Now how good of a bow tiller am I??

It looks good. Now find a big piece of paper and make a tracing of the outline. Before you pull on it!

[willie]

When I bamboo back a bow, I have backed about 50 so far, I make every edge of the bamboo stem to stern 1/16" thick, this naturally tapers the bamboo to the tips.

If you make your bamboo very thin you end up with bamboo backed osage bow. If you leave your bamboo thick you will end up with an osage belly bamboo bow with very little osage on the belly at normal poundages.

Eric, 
If your boo gets naturally tapered when you do the 1/16" everywhere method, then I assume you are using a smaller diameter diameter boo that what I see in Arvins pics? In which case the high crown serves as a trapping?

Having a flatter back would, in theory, reduce the the likelihood of a tension break in a highly strained bow. Arvin can proportion the back width to the belly width as he chooses to balance the materiel properties.

If you have a warbow shooting friend...get out the boat winch and put a string on it... LOL  I could only venture to guess at how heavy that bow is right now but I'd say way more than anyone could ever draw.  Bamboo backing PLUS the power the glue line creates is like a modern bow with natural materials...and hard to beat.   

Bob,
 I think Arvin intends to tiller the belly until he reaches his weight goal for the class? If his osage gets less than 1/3 the limb thickness, he can always tiller the width if he is concerned?
Not sure about the "power the glue line creates" with this bow. Do you do a perry reflex on boo backed glue ups?

[Bob Barnes]

Bob,
 I think Arvin intends to tiller the belly until he reaches his weight goal for the class? If his osage gets less than 1/3 the limb thickness, he can always tiller the width if he is concerned?
Not sure about the "power the glue line creates" with this bow. Do you do a perry reflex on boo backed glue ups?
[/quote]

I have been gluing bamboo backing on osage for a very long time, and the sum of the 2 is way more than a single piece of the same thickness.  I have just figured the glue added that extra...  no...I don't do a Perry reflex.

I know Arvin well enough to know he has plans and will make it work, but some of us were just trying to share our experience doing what we have done many times before since it's a first for him.  He shoots the 50# class mostly I think...

[Selfbowman]

Hey guys I have made 4 boo backed bows!!! I don’t know what I’m doing. Keep the info coming. I made a bamboo backed , bamboo core and gemsbok horn belly bow shooting for 50# it came out about 108 @29. Great bow but not for me. Tried again managed to get a fifty pounder but it was narrow. Had good cast then I found out some one shot 259. Mine might hit 250 on a good day. Arvin

[Selfbowman]

So it’s bad to have the Osage less than one third the thickness of the limb. More set or what?  Arvin

[DC]

I'm thinking that all we care about in a backing is tensile strength. Correct me if I'm wrong. I was looking at the Wood Database and it doesn't give tensile strength. Is one of those things listed there equivalent? Oh, if we only had an engineer

I have been gluing bamboo backing on osage for a very long time, and the sum of the 2 is way more than a single piece of the same thickness.  I have just figured the glue added that extra...  no...I don't do a Perry reflex.

What I'm thinking is that the boo has a higher tensile strength than the Osage and that's where the extra grunt comes from. I can't see it being a glue line but who knows. Maybe an engineer

[Bob Barnes]

I'm thinking that all we care about in a backing is tensile strength. Correct me if I'm wrong. I was looking at the Wood Database and it doesn't give tensile strength. Is one of those things listed there equivalent? Oh, if we only had an engineer

I have been gluing bamboo backing on osage for a very long time, and the sum of the 2 is way more than a single piece of the same thickness.  I have just figured the glue added that extra...  no...I don't do a Perry reflex.

What I'm thinking is that the boo has a higher tensile strength than the Osage and that's where the extra grunt comes from. I can't see it being a glue line but who knows. Maybe an engineer

could well be the boo but if I glue two wood lams together with a little reflex, they become several times stronger than the original wood it seems...?

[DC]

That could be the reflex. I was searching for info on gluelam vs wood beams and there was a few comments that it was because the gluelams are arched. I dunno, I'm way out of my depth here.
A while back I cut the back off an OS stave, reflexed it and glued it back together. It held the reflex way better than a heat treated stave. But, the final dimensions were not a lot different than a straight bow of the same DW. It doesn't take much difference though.