BBI verses BBO

[Mad Max]

How many more pounds would a BBI have verses a BBO ?
Everything else being the same.

[Badger]

 just a somewhat educated guess on my part as I never measure the thickness. I would say about 25 to 30#. They both finish at the same mass weight.

[Hamish]

That depends on the style of bow you make, width, length and belly design. In a practical sense an ipe bow will always need smaller dimensions in width and depth than an osage due to ipe's extreme density.

An osage elb around 60lbs at 28" draw, and around 1 to 1 & 1/8" wide, if made from ipe, it would only be7/8", or even 3/4" wide to make the same weight. An ipe made to the osage dimensions could easily make 100lbs, or more depending upon the skill of the individual bowyer.

A flatbow from osage around 1 &5/8" wide, 60lbs, can be made from ipe 1 &3/8"- or 1 &1/4".

What is your goal, or are you just interested hypothetically?

[Mad Max]

Ok let's try another way.

My stack is .558 thick now
Boo is 1/16" at the nock's and 1/8" at the center of the bow, 66" NTN
center lam is Osage, 3/16" .002 taper / 1/8" at the nocks and 3/16" at the center
Ipe is 1/4" parallel
I can make it 1-1/8" wide at the fades and 1/2" at the nocks
shooting for 45 to 50# at 28"

Nothing is glued up yet

Center post is 3-3/4" high
Mid limb is 2-3/4"
at the nock is 5"

https://imgur.com/a/2yROAeK

[Hamish]

Should work well.

[Mad Max]

 

[mmattockx]

This is based in ignorance of this particular combo in an R/D bow, but I would say your ipe is too thick. Unless you are going to remove a bunch in tillering, in which case it is probably OK. You only need a thin layer of it on the belly to carry the big compression loads, especially with an osage core that is very good in compression as well. If you had a maple core then I would say maybe 3/16" ipe, but the osage doesn't need that much help and a 1/8" belly lam should be enough for the load and would keep the limb weight down for more speed.



Mark

[Mad Max]

This is based in ignorance of this particular combo in an R/D bow, but I would say your ipe is too thick. Unless you are going to remove a bunch in tillering, in which case it is probably OK. You only need a thin layer of it on the belly to carry the big compression loads, especially with an osage core that is very good in compression as well. If you had a maple core then I would say maybe 3/16" ipe, but the osage doesn't need that much help and a 1/8" belly lam should be enough for the load and would keep the limb weight down for more speed.



Mark

It has to be scraped for tiller. Bamboo has nodes and some dips also.
BBI means Bamboo and Ipe, mine is a tri lam to keep the Ipe thinner.
If I made them all the time maybe I could get the Ipe thinner.

[Pat B]

Mark, have you talked to Roy. This seems to be his expertise.

[Mad Max]

Mark, have you talked to Roy. This seems to be his expertise.

Yes, I'm building off his form design and he gave me a stack height, I reduce the stack some because of the Ipe.
Same Ipe I gave you, any plan when you are going to build?
It was good to see and talk at the classic 

[mmattockx]

It has to be scraped for tiller. Bamboo has nodes and some dips also.
BBI means Bamboo and Ipe, mine is a tri lam to keep the Ipe thinner.
If I made them all the time maybe I could get the Ipe thinner.

Yes, I understand those things. With your 1/4" ipe thickness that in nearly half the total stack thickness. That means pretty much the whole compression side of the stack is ipe and it doesn't need to be, you only need the outer half of the compression side at most (which is where my 1/8" thickness came from). If you get your tapers right on the lams then you won't need too much scraping to get it bending nicely, but that is a practice thing, as you mention.

Post pics of the bow as you work on it, I am curious to see how much ipe you need to remove during tillering.


Mark

[Pat B]

Not sure when I'll be working on it. I'm in leather mode now. I'll bring it to the next Classic for your inspection and approval. 
 Good to see and talk to you at the Classic too.

[Mad Max]

Not sure when I'll be working on it. I'm in leather mode now. I'll bring it to the next Classic for your inspection and approval. 
 Good to see and talk to you at the Classic too.

I'm sure it will turn out nice.