Boo Backed Ipe Design Question

[bvalentine002]

Ok...so I've made a handful of  bows: hickory backed, hickory self, glass longbows, etc.

I got some Bamboo at KZoo and I'd like to make a Bamboo backed Ipe bow. I have a qustion about the layout. I'm shooting for 50-55# @ 32" (my long legs keep my knuckles from dragging). I was thinking 68" nock to nock.

I like the idea of a pyramid bow for the fact that there is little or no belly tillering. So I have some questions:

1. The max width I could make this bow is 2". Is that going to be wide enough to make a pyramid with these materials? Mid-limb would be 1.25".
2. Is there any reason NOT to make a pyramid design with these materials?
3. Everyone uses Urac. I have Resorcinol. Anyone ever have trouble using Resorcinol with these materials?
4. Any guidance on how thick to make the Ipe belly lamination? 1/4" sounds about right, but having never done it I'm probably wrong!

Any other thoughts? I'd appreciate everyone's input.
Thanks,
-Brett

[bvalentine002]

BTW...I'll try to do a build-along to help entertain everyone through the long boring winter.
 

[wingnut]

Sparky posted some pics and specs on a BBI not too long ago.  He has like a 31" draw so you should be able to duplicate his with no problem.

Here are a couple links to his bows

 http://tradgang.com//noncgi/ultimatebb.php?ubb=get_topic;f=1;t=039719#000000

 http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=039731


Mike

[clintopher]

2 inches is way to thick for ipe.  I haven't made one in a while, but I made a couple a while back and the bow's were 1 1/8" straight taper to 3/8" at nocks. That gave me a 45lb @28 bow.  Can't remember what the length was...around 64-66.

I used tight bond II so I can't see resorcinal being a problem.

[bvalentine002]

Clint,
What was the thickness of the Ipe belly you used?

Seems like my adjustment to 68" and my longer draw should put me pretty close. I might only have to go up by 1/64" in thickness.

Thanks,
Brett

[clintopher]

It's been so long I'm not quite sure but I think it was around 7/16 in the middle with a taper of maybe 5/16 to the tips.  I know the first one I tried to build was 1/2 at the center and it broke in the form.  Could have been the form though...I use blocks of wood to get the dips instead of a cut out form.

Clint

[bvalentine002]

Interesting. At the KZoo show I looked at a few BBI bows and the belly was quie thin...maybe 1/4"...

Also, I dod a Hickory backed Purpleheart whtat had a belly thickness of about 3/8"

Anyone else got a suggestion to help me get started?

Thanks,
Brett

[PV]

62" NTN Bamboo backed R/D .1 1/4"wide @ fades straight line to 1/2 " @ tips.I use a mid lam of ash or birch with a belly lam of ipe. I taper the lams .002 per inch and reverse them with the butt section of the ash midlam at the tips. Total thickness at glue up is .56 fades .49 tips. I taper the bamboo backing and make the ipe twice as thick as the ash. This will give me a bow of 55-60#

[PV]

The spec's from my first post are for a 28" draw. 32" wow! I would go longer 68-70" and thicker not wider. Maybe somewhere around .60 at the fades. The reason for the ipe twice as thick as the middle lam is it doesn't like thin. Lost a few at the middle of the limb were the deflex is the greatest.The thicker ash at the tips give make for slightly lighter limb. I use a tri lam rather than a single belly slat.It keeps more of the glued up profile off the form.
Good luck
Paul

[bvalentine002]

PV,
It's funny you mentioned using 3 lams.
I was thinking the same thing. I have used cedar on some glass bows and it turned out great. It;s so light and yet relatively stiff, but I'm always scared that the glue joint is going to give way (I'm still paranoid about this after more than 3000 shots).

Does anyone have any thoughts on using a middle lam of 1/4 sawn cedar?

Man, I'm getting my self in deep for this first Boo backed bow!
-Brett

[PV]

Brett,
I've used red birch with ipe and it's worked well. I think it's sg is near cedar.In theory the middle lam is just along for the ride. Got my doubts about that.
"Man,I'm getting myself in deep for this first Boo backed bow!"
Stop now as there's no going back    
Paul

[bvalentine002]

PV,
Thanks. I should have stopped a few years ago...before I started.

Still, cedar scares me...I really wonder how well the cedar will hold onto the resorcinol. I think I'll try that on my 2nd attempt.

I have decided on a 70" overall (68" N2N), boo backed Ipe with a max width of 1.5" with a straight taper to 3/8". It also appears that 7/16 is a good place to start for Ipe thickness (assuming no center lam). Hopefully I won;t have to taper it too much.

I'm going to glue up about 1.5" of deflex and about 4" of reflex.

Go big or go home, right?
   
Brett

[PV]

Sounds like a good place to start.A couple of things that I've found with bamboo and ipe. Keep the nodes as far from the bottom of your deflex as possible.(The nodes on bamboo are stiffer and weaker than the rest of the backing)This makes the deflex easier to tiller.With straight side taper limbs your belly taper is minimal.The crown on the boo has a natural taper and I also taper the thickness of the boo (measured from the top of the crown to the flat not the sides)slightly. My finished limbs usually taper .060-.075 in thickness.Keep us posted.
Go big and good luck
Paul

[Si]

IF ANYONE NEEDS IPE I AM SELLING ON EBAY EACH WEEK. JUST SEARCH ON IPE.