Primitive Archer

Main Discussion Area => Bows => Topic started by: Selfbowman on August 08, 2020, 11:55:31 am

Title: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 11:55:31 am
Iíve done this before with gemsbok horn but this time itís bamboo. Made another caul with a tad more reflex.
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 08, 2020, 11:58:54 am
you made a bow with a gemsbok back?  Looking forward to pics of both...   :OK
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 12:10:47 pm
Pic hopefully
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 12:16:49 pm
Yes Bob . Iíve straightened and prepared the back without violating the back ring . Built a new caul with a tad more reflex. Prepared the bamboo and will glue it up sometime today.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 12:19:38 pm
Pic of gemsbok backed bow
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 12:24:31 pm
Spent some hours on the heat bench and not finished yet.also I heat treated the back also prior to gluing bamboo on. DC did it on his laminates on his last build .  Thought I would try it on this one. Arvin
Title: Re: Bamboo backed selfbow
Post by: willie on August 08, 2020, 12:31:38 pm
Did you post in another thread about the gemsbok backed bow?  how did it shoot?

watching with interest to see the profile of the bow off your new caul
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 12:40:07 pm
Bob the bow tested good . Short of Steveís record but may be a contender with the right conditions. 222 yds was best test shot. Just trying different  backs for simple composite class Arvin
Title: Re: Bamboo backed selfbow
Post by: DC on August 08, 2020, 12:42:11 pm
Is the boo backed bow osage?
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 12:43:33 pm
Yes DC
Title: Re: Bamboo backed selfbow
Post by: DC on August 08, 2020, 12:49:18 pm
 I was a little concerned that heat treating the back of the belly would affect the glue up but it didn't seem to harm it. I'll be watching, I've got a piece of Osage that I can't make a decision on.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 12:57:53 pm

Pic of growth rings
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 01:01:56 pm
The rings are real even but getting that back flat enough to not violate a growth ring took some doing with dry heat. Now if I can keep in one growth ring when tillering the belly. Arvin
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 08, 2020, 01:06:04 pm
that's pretty cool Arvin.  I don't think I have ever seen the horn on the back...usually it's on the belly.  Now, bamboo backed osage is a marriage made in heaven... :)

Seeing the picture of your edge grain reminds me of my favorite bamboo backed osage...but I used the most perfect edge grain osage I've ever seen for the belly slat.  It's the one I shot at MoJam.

Looking forward to seeing the finished bow and the stats on it's performance.    (SH)
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 01:45:07 pm
Miserable bow making weather!
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 01:51:15 pm
Here is a pic of bow on the 2x4 caul before the bamboo is going to be applied. Arvin
Title: Re: Bamboo backed selfbow
Post by: Rākau on August 08, 2020, 02:48:15 pm
how exactly do you go about getting the back of a stave flat to the point that it is good enough to mate with the bamboo backing?
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 04:06:17 pm
1 a good caul
2 a good heat gun
3 a good stave
4 ryobi 4x36
5 scrapers I f needed
6 which is supposed come first . Asking for Gods help!
It was easier with the horn because itís more flexible. That being said I think I can. I think I can. I think I can.  ;D
Arvin
Title: Re: Bamboo backed selfbow
Post by: sleek on August 08, 2020, 04:08:06 pm
Say Arvin, why are you putting so much emphasis in having a flat single back ring to put the bamboo on? I understand the belly ring, but not the back?
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 04:16:56 pm
Well sleek  the real reason I guess my selfbows can shoot farther. The rings are real even and I need a back for the class. I donít know. >:D
Arvin
Title: Re: Bamboo backed selfbow
Post by: sleek on August 08, 2020, 04:21:43 pm
Well sleek  the real reason I guess my selfbows can shoot farther. The rings are real even and I need a back for the class. I donít know. >:D
Arvin

Lol, makes sense! Im gonna have to make a bamboo backed bow too now.  If im going to the flats, I may as well bring an arsenal with me.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 04:46:07 pm
Are you really coming? Thatís fantastic! Need some more folks for sure. Takes more than one old  Californian to keep that arrogant Texan in line! >:D >:D I would love to see more of you guys there. Maybe put Faces to names. Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 06:18:31 pm
More heat . On the bench and the yard! Yuk!!!!!
Title: Re: Bamboo backed selfbow
Post by: PatM on August 08, 2020, 06:23:42 pm
The terminology folks are slipping.  A backed selfbow?   You can't say that!
Title: Re: Bamboo backed selfbow
Post by: sleek on August 08, 2020, 06:32:17 pm
Are you really coming? Thatís fantastic! Need some more folks for sure. Takes more than one old  Californian to keep that arrogant Texan in line! >:D >:D I would love to see more of you guys there. Maybe put Faces to names. Arvin

I'm gonna do my best. Plan is to buy my plane ticket next week I hope.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 07:01:21 pm
Well Pat my other bad subject was grammar  !!!  O:)
Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 07:30:42 pm
This is the best I am willing to do at this time.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 07:49:04 pm
Ok 3-3/4 before bamboo.
Title: Re: Bamboo backed selfbow
Post by: sleek on August 08, 2020, 07:54:02 pm
Whats your width? Is it your standard 2 inches?
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 08:04:09 pm
Puting a little pre bend on the bamboo. Grass donít care for heat much.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 08:09:12 pm
Well I think it will end up a 1-5/8 or there abouts.67ntn 9 inch handle. Pretty much same bow just another inch of reflex if I can manage to hold it thru tiller. Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 08, 2020, 08:12:10 pm
Wish I could load video. Iíd show the back of the selfbow. Oh there I go again with bad grammar.  Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 09, 2020, 11:34:27 am
Surfaces ready to glue up. A quick dry check. Good but not perfect.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 09, 2020, 11:40:24 am
Question? What glue would yíall recommend for boo to Osage? Unibond 800, smoothon, or hide glue are your choices.  Arvin
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 09, 2020, 11:51:47 am
I always used URAC and think unibond is about the same, but everyone seems to be using smooth-on now.  Both will work.
Title: Re: Bamboo backed selfbow
Post by: willie on August 09, 2020, 12:13:23 pm
the epoxy might be better if you are concerned about gaps
Title: Re: Bamboo backed selfbow
Post by: DC on August 09, 2020, 12:19:43 pm
Why do you have the bamboo so thick? Thin boo glues up way nicer, it conforms to the waves.
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 09, 2020, 12:25:17 pm
What DC said...that stave with bamboo that thick and you will have a war-bow weight when it dries... are you adding a power lam?
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 09, 2020, 12:33:27 pm
No power lam. Simple composite. Whatís more heavy bamboo or Osage for a backing? Might want to trap. If I end up with less Osage it might cut down the mass weight and still have a great backing. Just trying stuff. Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 09, 2020, 12:39:54 pm
Well just read unibond sets in 10 min at 90* so I better weight till in the morning.it might be 80.By then . Arvin
Title: Re: Bamboo backed selfbow
Post by: DC on August 09, 2020, 12:42:52 pm
No power lam. Simple composite. Whatís more heavy bamboo or Osage for a backing? Might want to trap. If I end up with less Osage it might cut down the mass weight and still have a great backing. Just trying stuff. Arvin

Gotcha :)
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 09, 2020, 12:51:22 pm
I don't think that adding the 16-18" power lam would make it a complex composite...it's just a small piece to stiffen the riser/grip area... If you glue what you have it might not bend after drying.  LOL
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 09, 2020, 01:01:19 pm
 Bob thatís going to happen in the tiller if I do my job right. Painters tape keeps all that glue I will have smeared everywhere off the back. I hate glue and paint. Avin
Title: Re: Bamboo backed selfbow
Post by: DC on August 09, 2020, 01:57:15 pm
We had a bit of a discussion about how long a power lam had to be to bump you up a class. I don't think we ever got to an definitive answer but it was something like, if the "reinforcement" goes past the fades you go up to complex. At least that's what I got out of it. I think it was in "Flight Bows" somewhere.
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 09, 2020, 02:17:02 pm
I went back and looked at that thread...and I'm wrong about the power lam.  According to Alan "A ďpowerlamĒ or double wedge in the handle between the belly and backing layer risks reclassification as a Complex-Composite."   

Title: Re: Bamboo backed selfbow
Post by: PaSteve on August 09, 2020, 04:33:27 pm
 Looking good Arvin. Anticipating the final result.
Title: Re: Bamboo backed selfbow
Post by: mmattockx on August 09, 2020, 10:10:09 pm
We had a bit of a discussion about how long a power lam had to be to bump you up a class.

According to Alan "A ďpowerlamĒ or double wedge in the handle between the belly and backing layer risks reclassification as a Complex-Composite."

I'm not a flight shooter, so this may be a dumb question. If a powerlam will cause a reclassification can you simply put the same taper on the belly lam as what adding a powerlam would give you and avoid the whole problem?


Mark
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 01:36:12 am
We had a bit of a discussion about how long a power lam had to be to bump you up a class.

According to Alan "A ďpowerlamĒ or double wedge in the handle between the belly and backing layer risks reclassification as a Complex-Composite."

I'm not a flight shooter, so this may be a dumb question. If a powerlam will cause a reclassification can you simply put the same taper on the belly lam as what adding a powerlam would give you and avoid the whole problem?


Yes thatís what Iím thinking. Just make the fade longer.. Arvin


Mark
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 01:37:50 am
Boo is glued to the SELFBOW!  >:D
Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 01:46:59 am
Ok question for the guys with trapping experience. Do we trap the back then tiller or as we go. I think on this pyramid trap then tiller. Ok next question. Would 10% of limb width be about right for bamboo to Osage ratio. This is where you smart guys trump me for sure. Arvin
Title: Re: Bamboo backed selfbow
Post by: Rākau on August 10, 2020, 02:53:11 am
1 a good caul
2 a good heat gun
3 a good stave
4 ryobi 4x36
5 scrapers I f needed
6 which is supposed come first . Asking for Gods help!
It was easier with the horn because itís more flexible. That being said I think I can. I think I can. I think I can.  ;D
Arvin

haha fantastic! do you prep your own boo as well?
Title: Re: Bamboo backed selfbow
Post by: Marc St Louis on August 10, 2020, 06:51:20 am
I'll say like the others.  Your Bamboo thickness will give you a very heavy bow.  Trapping won't help with that.  All that will do is weaken the backing

Bamboo is heavier than Osage
Title: Re: Bamboo backed selfbow
Post by: Eric Krewson on August 10, 2020, 07:05:12 am
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.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 08:38:27 am
Well I do have a heavy war bow.  But I have a guy that can pull 100-120#. Marc is the ryne of the boo heaver than the core. My thinking was the boo would override the Osage and it did thatís why I was going to trap the boo and lighten the bow. This thing may end up 1Ē wide at the fades too. The back did glue up nicely. Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 08:47:20 am
Pic
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 08:51:52 am
I did have to small areas that glue did not fill out on the edges . Not bad maybe 1/8Ē deep. Looks like narrowing the bow will eliminate that.  Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 08:58:33 am
The boo was prepped on the 4x36 ryobi. Some scraping for sure. I will go out on a limb here. This bow will break a record in some weight class in simple composite broadhead.  Arvin
Title: Re: Bamboo backed selfbow
Post by: DC on August 10, 2020, 09:16:50 am
Ok question for the guys with trapping experience. Do we trap the back then tiller or as we go. I think on this pyramid trap then tiller. Ok next question. Would 10% of limb width be about right for bamboo to Osage ratio. This is where you smart guys trump me for sure. Arvin

I've trapped the last 3 bows. I did about 1/8" on each side. Don't know if it did anything for speed. Sometimes you just have to do these things blindly and hope. I kinda like the look though :)
Title: Re: Bamboo backed selfbow
Post by: DC on August 10, 2020, 09:21:17 am
We had a bit of a discussion about how long a power lam had to be to bump you up a class.

According to Alan "A ďpowerlamĒ or double wedge in the handle between the belly and backing layer risks reclassification as a Complex-Composite."

I'm not a flight shooter, so this may be a dumb question. If a powerlam will cause a reclassification can you simply put the same taper on the belly lam as what adding a powerlam would give you and avoid the whole problem?


Mark

I can't see why there would be any difference. Thickness is thickness unless glue has some magic quality I haven't figured yet. I have just left the boo thicker in lieu of a power lam. It seemed to work.
Title: Re: Bamboo backed selfbow
Post by: mmattockx on August 10, 2020, 09:58:48 am
Ok question for the guys with trapping experience. Do we trap the back then tiller or as we go. I think on this pyramid trap then tiller. Ok next question. Would 10% of limb width be about right for bamboo to Osage ratio. This is where you smart guys trump me for sure. Arvin

1) Trap, then tiller.
2) If you want a more precise answer, PM me with your limb dimensions and I will crunch some numbers to try and get you into a more accurate ball park on how much to trap.


Your Bamboo thickness will give you a very heavy bow.  Trapping won't help with that.  All that will do is weaken the backing

Trapping will certainly reduce the weight since it lowers the limb stiffness. It may not reduce the weight enough to make the bow manageable, though.


I can't see why there would be any difference. Thickness is thickness unless glue has some magic quality I haven't figured yet. I have just left the boo thicker in lieu of a power lam. It seemed to work.

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
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 10:08:47 am
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. Yíall might not even know what I am trying to say. Not the best at explaining what I am thinking. :-\Arvin
Title: Re: Bamboo backed selfbow
Post by: DC on August 10, 2020, 10:11:59 am

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.
Title: Re: Bamboo backed selfbow
Post by: DC on August 10, 2020, 10:20:38 am
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. Yíall 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.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 11:07:10 am
Ok DC here it is glued up setting on the caul. Now how good of a bow tiller am I?????
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 11:10:15 am
Here it will t is on my previous caul.
Title: Re: Bamboo backed selfbow
Post by: JW_Halverson on August 10, 2020, 11:30:59 am
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.
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 10, 2020, 11:37:48 am
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.   :OK
Title: Re: Bamboo backed selfbow
Post by: DC on August 10, 2020, 11:42:19 am
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! :D
Title: Re: Bamboo backed selfbow
Post by: willie on August 10, 2020, 12:20:30 pm
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.   :OK

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?
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 10, 2020, 12:52:53 pm


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...
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 01:11:31 pm
Hey guys I have made 4 boo backed bows!!! I donít know what Iím 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
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 01:27:16 pm
So itís bad to have the Osage less than one third the thickness of the limb. More set or what?  Arvin
Title: Re: Bamboo backed selfbow
Post by: DC on August 10, 2020, 01:41:31 pm
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 ;) ;)
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 10, 2020, 01:49:49 pm
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...?
Title: Re: Bamboo backed selfbow
Post by: DC on August 10, 2020, 01:59:47 pm
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.
Title: Re: Bamboo backed selfbow
Post by: mmattockx on August 10, 2020, 02:38:37 pm
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.

Have you measured the difference? Much of the data I have seen indicates that bamboo and osage are similar in terms of the modulus of elasticity (MOE), so the combination shouldn't be much different than either on its own at the same thickness as the lam bow. If one is much stiffer than the other (higher MOE) then the combination would feel much stiffer.


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 ;) ;)

If only, huh? ;)

The wood database calls the tensile strength the Modulus of Rupture. It shows an MOR of 11,020-24,450psi for bamboo and an MOR of 18,650psi for osage. That number is a fair bit lower than other data I have seen for osage, though. MOE for bamboo is 2,610,000-2,900,000psi and 1,689,000psi for osage. Again, that is low compared to other data I have seen on osage. If it is accurate, then bamboo would really stiffen up osage in a lam bow.


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...?

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.

My experience with reflex is limited, but so far I would agree that reflex seems to really stiffen up the limbs out of proportion to the change made/added.


Mark
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 03:01:09 pm
Ok got yíall thinking.
Title: Re: Bamboo backed selfbow
Post by: willie on August 10, 2020, 03:46:23 pm

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

More set if the bamboo and osage differ significantly in their stiffness. I do not see any reason not to feel comfortable with 1/2 and 1/2 in thickness before thinking ahead to different tillering options.  Side tillering may be an option if it's not in an area of the limb that might want to twist on account of the tips being further back.

How thick is the bamboo just before the hook compared to the thickness of your self bows with the shorter hooks (measured in the same place)
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 03:54:36 pm
When you get it figured out . See how this trap stands with your thinking. 1-1/2 at fades is the width=
1-1/16 at the top of the trap. Mid limb 1/1/16 wide top of trap7/8. Tips 3/8 wide 1/4Ē top of trap. Does thickness matter? This is as perfect diminishing mass as I can think of. If you pros do . Do we get the tips bending first on the tiller? Arvin   
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 03:55:44 pm
Pic
Title: Re: Bamboo backed selfbow
Post by: Badger on August 10, 2020, 04:41:55 pm
DC, You are allowed to build up the handle on a simple composite bow, this would include a power lamb as long as it doesn't go past the fades or exceed 12" length I think. I need to double check on the length.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 05:08:11 pm
Ok trapped for now. It will bend like a hundred pounder now. ;D the pic is pretty good representation of the limb and the bamboo thickness. So I could take the Osage to about 3-1/6 and that would put the two materials pretty close on compression and tension. Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 05:12:22 pm
Pic
Title: Re: Bamboo backed selfbow
Post by: mmattockx on August 10, 2020, 06:16:51 pm
When you get it figured out . See how this trap stands with your thinking. 1-1/2 at fades is the width=
1-1/16 at the top of the trap. Mid limb 1/1/16 wide top of trap7/8. Tips 3/8 wide 1/4Ē top of trap. Does thickness matter? This is as perfect diminishing mass as I can think of. If you pros do . Do we get the tips bending first on the tiller? Arvin

You should be trapping as a percentage of width and thickness, not random amounts. Say, reduce the back width to 80% of the full width and then taper down maybe 70% of the side depth. Don't trap to a sharp edge on the belly, make sure you leave at least a bit of a flat on the side. To get a consistent back width, measure every 2" along the limb and mark the reduced width you want on the back  and mark how far down the side you are going to go. Then connect all those dots with a line and rasp up to that line.

This keeps the trapped proportions the same full length of the limb and doesn't result in stronger and weaker areas. Being consistent with the trapped cross section will make your life easier when tillering.


Mark
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 07:59:47 pm
Thanks Marc!!! I will read this probably 10 times before I make another stroke. Tip overlays going on.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 09:16:56 pm
Pic at fades thickness.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 10, 2020, 09:34:05 pm
Ok Steve what should this  bow s draw weight be. 67Ē,9Ē handle. 1-1/2 at fades 3/8 tips you know the design. Thanks. Arvin
Title: Re: Bamboo backed selfbow
Post by: sleek on August 11, 2020, 12:32:58 pm
Boo is glued to the SELFBOW!  >:D
Arvin

Hey, we gadda move this thread now, he is CLEARLY breaking all the rules!!!   >:D
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 11, 2020, 01:19:37 pm
No power lam😁
Title: Re: Bamboo backed selfbow
Post by: Eric Krewson on August 11, 2020, 03:22:03 pm
Narrow bamboo, I don't use it, I cut out the exact bow pattern out of my bamboo then thin and flatten the bamboo until the edges are 1/16", I use a belt sander with a 36 grit belt for the process.

As you can see my bamboo backing is thin, I cut the slats from 4-5" diameter culms that I harvest from a patch across town. It is mandrake, the rind always looks green even when it is completely dry. The bamboo is tan under the rind.



Title: Re: Bamboo backed selfbow
Post by: Eric Krewson on August 11, 2020, 03:31:53 pm
I cut my slats from this, it is freshly cut.

Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 11, 2020, 03:44:53 pm
Eric how long do you season your bamboo? Just asking? Donít know anything about it. My knowledge is call Jaap.   ;). Here are pics of tip overlays. Also a pic of trap at mid limb.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 11, 2020, 03:46:14 pm
Pic
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 11, 2020, 03:47:29 pm
Trap pic
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 11, 2020, 03:54:04 pm
Ok way to hot to tiller so may start that in the morning. The tips and back are about ready for finish except at handle.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 11, 2020, 04:16:01 pm
One more pic for DC before it goes to the tiller tree.
Title: Re: Bamboo backed selfbow
Post by: willie on August 11, 2020, 04:47:28 pm
looking good
Title: Re: Bamboo backed selfbow
Post by: DC on August 11, 2020, 05:42:35 pm
Selfbowman your inbox is full ;)
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 11, 2020, 07:26:59 pm
Whatís in box??? Oh you mean my message box  :-\📦. I didnít know i was suppose  to look there. People from cedar breaks?  Probably some folks think I been ignoring them. That arrogant Texan. I just donít know or care about all this technology. But I do yíall. Iíll look and try to figure out how to address it. Arvin
Title: Re: Bamboo backed selfbow
Post by: Eric Krewson on August 12, 2020, 07:11:54 am
After I cut the bamboo into 6' lengths I knock the internal nodes out with a hoe handle and let the bamboo dry until it turns tan. Letting it dry whole eliminates cupping and warping as it dries, with the nodes out you get a chimney effect and keep air moving through the trunk. if you don't knock out the nodes it will take months for the trunk to dry out, moisture will have to go out through the rind which is a very slow process.

After it turns tan I pop a chalk line on the trunk and run it through my bandsaw to reduce it to 2" wide slats. I use the bandsaw to remove as much of the belly as I can from each slat then give the slats a few passes through my jointer to reduce the belly to completely flat.

At this point I store it for future use.


Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 12, 2020, 07:33:45 am
Got it to.brace. 45@23
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 12, 2020, 07:35:36 am
Some set happing .
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 12, 2020, 07:59:34 am
More off outter  limbs and a tad at the fades??weighs 25oz . Probably 2-1/2 oz in handle to be removed. Got to have my tacky shelf. Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 12, 2020, 08:08:09 am
You guys wake up!!!
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 12, 2020, 08:49:50 am
After I cut the bamboo into 6' lengths I knock the internal nodes out with a hoe handle and let the bamboo dry until it turns tan. Letting it dry whole eliminates cupping and warping as it dries, with the nodes out you get a chimney effect and keep air moving through the trunk. if you don't knock out the nodes it will take months for the trunk to dry out, moisture will have to go out through the rind which is a very slow process.

After it turns tan I pop a chalk line on the trunk and run it through my bandsaw to reduce it to 2" wide slats. I use the bandsaw to remove as much of the belly as I can from each slat then give the slats a few passes through my jointer to reduce the belly to completely flat.

At this point I store it for future use.

Cool Eric thanks for sharing. If I only had bamboo growing somewhere.  Arvin
Title: Re: Bamboo backed selfbow
Post by: DC on August 12, 2020, 10:28:29 am
I like the braced pic. I've just about run out of boo and my supplier doesn't answer any phone or e-mail. Looks like I'm almost dead in the water. have to make selfbows for a while.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 12, 2020, 11:24:31 am
Ok 50@28 and here is a pic of that nasty set. Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 12, 2020, 11:26:20 am
Oh mass about 18oz.now to shoot it.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 12, 2020, 11:50:58 am
Oh how about that single growth ring on the belly? All good except for two little islands.
Title: Re: Bamboo backed selfbow
Post by: willie on August 12, 2020, 12:59:30 pm
You guys wake up!!!
if I get up too early, I have to run the heater to take the chill off.

doesn't look like it took much more set from brace to full draw.  Going to shoot it much before the competition?  how many bows are you taking this year?
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 12, 2020, 01:24:08 pm
Iím taking 5or6 . Then there could be 2-3 of my bows be brought by others. Trying to shoot something every chance I get. Canít learn if ya donít try. Speaking from experience! Arvin
Title: Re: Bamboo backed selfbow
Post by: sleek on August 12, 2020, 01:37:58 pm
How mush set did it take there Arvin?
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 12, 2020, 01:53:53 pm
Donít you look at the pictures? Itís laying on the caul 4 post up. Thatís not set though that was calculated precisely so this bow would have deflex and reflex . So it would shoot arrows far.  I have ocean front property in  Montana also .>:D Arvin
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 12, 2020, 05:21:40 pm
looks like it will be a well mannered hunting bow when shot in... I had a little more set than I wanted when I first started making BBOs.  Then I started doing like Eric... flattening the bamboo, putting my pattern on it, cutting it to bow profile, and then sanding/thinning it to about 1/16".  I then could glue it to the osage slat and use it as the pattern for cutting out my osage as well.  Good job on yours though...I'd hunt with it...    :OK
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 12, 2020, 08:59:23 pm
Bob we need to build some bows together. Arvin
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 12, 2020, 09:43:27 pm
it would be fun...but you work way faster than I do...  :BB
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 13, 2020, 07:57:57 am
All finished except strike plate and rug. Thanks for the interest. Arvin
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 13, 2020, 07:59:15 am
Pic
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 13, 2020, 10:35:38 am
it's a nice back profile...looking forward to hearing your thoughts after shooting it in...and seeing your crony numbers. 
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 13, 2020, 11:07:45 am
I havenít shot it yet but except in a target Maybe 10 shots . To hot. Shoot it and the flats and weíll see what it has.
Title: Re: Bamboo backed selfbow
Post by: sleek on August 13, 2020, 12:29:14 pm
Donít you look at the pictures? Itís laying on the caul 4 post up. Thatís not set though that was calculated precisely so this bow would have deflex and reflex . So it would shoot arrows far.  I have ocean front property in  Montana also .>:D Arvin

The way they talk about global warming,  who knows, ocean front property in Montana may not be a bad prospect. 

Any idea how many inches set it took  my calibrated eye aint what it used to be.
Title: Re: Bamboo backed selfbow
Post by: Will B on August 13, 2020, 03:33:49 pm
Thatís a great looking BBO. Thanks for posting the pics and showing us how you do it. Very helpful!
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 13, 2020, 04:07:15 pm
Sleek it was 3-1:2 off the wall at handle off the caul. Now probably have that. Well see if itís enough to shoot 235 or so. The good thing I think is it weighed in at 18 oz. Arvin
Title: Re: Bamboo backed selfbow
Post by: JW_Halverson on August 13, 2020, 04:52:55 pm
Wishing you nothing but good luck and long flights, brother!
Title: Re: Bamboo backed selfbow
Post by: M2A on August 14, 2020, 06:38:54 am
Thanks for showing your work! Enjoyed following along with the build. Good luck with your flight shoot.   
Mike   
Title: Re: Bamboo backed selfbow
Post by: bownarra on August 14, 2020, 12:49:42 pm
Nice bow :)
I'd have gone with a little more bend out of the fades.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 16, 2020, 06:50:24 am
Thanks guys it was a fun build . Arvin
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 16, 2020, 06:59:35 am
thank you Arvin.   :OK
Title: Re: Bamboo backed selfbow
Post by: Marc St Louis on August 16, 2020, 12:54:27 pm
What ratio of Bamboo to Osage did you wind up with
Title: Re: Bamboo backed selfbow
Post by: PaSteve on August 16, 2020, 03:15:55 pm
Very cool Arvin. Wish you the best of luck at the Flats!
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 16, 2020, 04:41:25 pm
What ratio of Bamboo to Osage did you wind up with

Marc Iím going to say45-55 to 40-60 . The lower numbers being  bamboo. I think with this design  and these materials this would have made a better bow with less set at 40-45#. That would have gotten the materials more even . That is one thing about flight shooting and building bows for flight.  Trying to hit those weights with unpredictable materials. I have heard it on here that the bow will be what it has if tillered right. So if a bow starts taking set early on the wood does not have that draw weight in it. Compromise and make less draw weight bow.  Hope your able to understand my thoughts . Please respond if you are or arenít in agreement. Arvin
Title: Re: Bamboo backed selfbow
Post by: Marc St Louis on August 17, 2020, 08:37:21 am
Well that's not too bad.  Usually the ratio is more like 20/80.  Who knows, maybe with those ratios there will be better performance, I tend to think not but you never know.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 17, 2020, 10:46:09 am
Marc I only built a hand full of bamboo backed  bows . So much to learn!!
Arvin
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 17, 2020, 10:57:14 am
that's the only way you'll ever know what works best for you and the intended purpose.  I agree with Marc about 20-25% bamboo maximum for a BBO... "Less is more" 
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 17, 2020, 11:39:29 am
Ok guys I could not wait. Shot two 454 gr bamboo broadhead arrows one 245yds and one 240 yds. That was with D97 . Pretty sure Iíll get 240 yds with linen at the flats with it. Weíll see. Better than I thought. I think the 18 oz had a good bit to do with it. Arvin
Title: Re: Bamboo backed selfbow
Post by: willie on August 17, 2020, 01:04:56 pm
Quote
Shot two 454 gr bamboo broadhead arrows one 245yds and one 240 yds.
Very Nice, but doesn't that make the waiting even harder?
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 17, 2020, 04:38:58 pm
Ummm no.
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 28, 2020, 03:31:22 pm
Ok I shot 2 arrows at the house elevation 780í. 240yds and 245yds. Next I shot 1 arrow in Co . At 7500í elevation. 252yds I was standing about 60 Ď above landing field when I shot it. Bonneville is 4200 elevation. How far will it shoot there??  ??
Arvin
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 28, 2020, 03:45:42 pm
hhhmmmmm...you sound either excited or disappointed...so I'll say either 235 or 255... :)  either way it's a great shot.   :OK
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 28, 2020, 04:25:48 pm
Would it be leagal to have a just for fun pot- bragging rights on the flight distance of this bow. Mine doesnít count but if it did 247yds. Arvin
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 28, 2020, 04:35:24 pm
mathematically you would be correct... :)  actually it might be 248...  (SH)
Title: Re: Bamboo backed selfbow
Post by: Selfbowman on August 28, 2020, 07:58:59 pm
Ok bob your number is 248? We have a start.
Title: Re: Bamboo backed selfbow
Post by: Bob Barnes on August 28, 2020, 08:16:35 pm
 :OK 248