Built my BBI form..didn't work

[vanillabear?]

[Echatham]

that sounds like a better idea to me Vanillabear.

[John Scifres]

You won't get much springback at all when gluing in reflex/deflex.  Personally, I would move the center posts out maybe 2" from the handle.

The first time you tiller one of these bows you'll be confused.  But watch the limbs move and don't take too much off until you get it bending about 20".  They really start to come full circle the closer you get to full draw.

You don't have to worry so much about set since you will be really close to final dimensions, assuming you did everything right.  If your design, measurements and layout are really well done, these kind of bows are almost tillered on glueup.

[Zradix]

Thanks for the advice guys.

John..Why would you move the posts out further?
Right now I have them so the actual center of the limb is centered right on the middle of the pad.

From what I read, moving them out further will make the bow like lighter arrows.
Also, it will put a more pronounced/agressive bend at the tips.
Neither of these things sound particularly bad, though I'll most likely be shooting in the 11.5 gr/# arrow range.

I'm not arguing with ya John..
Just asking for an education buddy..
   

[vanillabear?]

[Echatham]

Zradix here is my theory on mid limb post placement... and its based solely on my own ponderings and i took a physics class once.  if the reflex to deflex transition is occuring more towards the handle, it puts more of the limb mass moving in the later part of the power stroke, meaning more momentum, meaning more efficient with a heavier arrow.  if the transition is happening closer to the tips, there is less limb mass moving at the end of the powerstroke, meaning faster.. meaning it throws a lighter arrow more efficiently.

[Zradix]

That's more or less my understanding as well Eric.
Has to do with the efficiency of the wood and the moving mass I believe.

[Mike Most]

Man when you got it, you got a bad case of it, whatever it is that you got......      

[John Scifres]

Mostly visual for me.  I abandoned physics after 2 weeks and the first quiz  

I learned BBOs from Dean and others on the ***********.  I was instructed to get my core to 3/16" thick or so and well tapered so that's what I have always done.  I never got much springback doing that.  That should get you to 50-60# depending with a 1-1/4" width and a 60-64" NTN length.

Every material has a thickness that it will work best at without taking a set.  3/16"-7/16th seems to be a sweet spot for good osage in a BBO.  Adjust width to adjust weight from there.

[Zradix]

Good info

Thanks John

[Draffish]

looking good zradix brave move selling a brought bow to finance making your own but nothing in life is worth doing without a bit of risk. good luck

[Zradix]

 

lol

[Roy from Pa]

Zradixy ole boy, just use the post specs I said above. I learnt form Dean Torges also. And yunzs are right on your theory of mid limb placement. Posts closer to the handle work more limb for shooting a heavier arrow. Posts moved more towards the tips shoots a lighter arrow faster. But I really doubt we could see the difference with the naked eye if both bows were 50 pounds at 28". Lately I have been placing my mid limb posts exactly half way between the tips and the flares. Ya otta flip the tips too before ya glue her up. Makes for a sexy looking bow.

   

[Zradix]

Wait wait wait.!!

I need some lingo edumacation..

What/where are the flares? ( end of the power lam?)
..I have my mid limb posts so the middle of the limb (measured from the center of the bow to the tip) ,rests on them.
I measured and marked my template slat. Then placed the pads so they were right under the mark.

Is that not good?
Now ya got me thinking maybe I should measure the "mid limb" from the end of the power lam to the tips?

What is "flip the tips"?

Thanks

[Roy from Pa]

I don't use a power lam. I glue up the boo and osage first. Then after that's dry I lay the riser section of the bow on top of the side of riser block and trace out the curve onto the riser block, then cut that curve out of the riser block. Then glue the riser block onto the bow with the center of it centered on the center of the bow tip to tip.. I make my risers anywhere from 10 to 12 inches long. The flares are the widest part of the bow limb at the end of the riser. I center my mid limb posts half way between the flares and limb tips. The way you describe is moving your mid limb posts closer to the end of the riser. Flipping the tips is inducing reflex at the end of the limb tips with heat, about 8 inches in from the end of the tips. Gives the bow profile a little recurve look.

[Roy from Pa]

When you glue up the belly wood and boo, the riser section of the bow will now have a curve in it. You see how the center of this glue up is curved? You have to make a riser block to fit that curve.

 

 You then need to cut out a block of wood for the riser/handle section of the bow. You take the bow and lay it on it's side on top of the side of the riser block you have cut out. Trace that outline and cut out the outline. Then you glue the riser block to the bow like in this picture below.


   

   

[Zradix]

I see..

Thanks Roy.
You're exactly right in my mid posts being closer to the riser.

I had heard "middle of the limb".
I shoulda heard middle of the working limb.

I'll be playing with that a bit over the next few days.

Thanks for the help guys.

I truly appreciate it.

The flipped tips do look nice.
Doing that feels outta my skill level at the moment.

That is the way I'm planing on doing the riser..after the boo and ipe are glued.

Read that advice on Eric's build
you guys are great!

[Roy from Pa]

Flipping the tips is a piece of cake. I made a 7 inch long curved block and place it under the belly wood. Clamp the bow at center so it doesn't move. Heat the last 8 or 9 inches on the tips with a heat gun till it's almost too hot to touch, then clamp it down and let sit till it cold.

   

   

[Zradix]

Darnit Roy..
You're making more work for me.
lol

You make it look easy man.

I'll be thinking bout this move.

When you do that, do you keep the same end post height as normal?
Or do raise them a bit to account for the pre glued bend?

I would think it might take some practice to do that evenly on each end.

This is gonna be sweet..

[Roy from Pa]

I keep the end posts still at 6. When making a wooden bow, ya don't want to get too crazy with reflexing tips. Some guys do, not me.