BBI R/D design help please.

[John Malone]

Hey Guys been awhile since I made a bow so here we go.
 I need some tiller practice on a r/d so I'm going with boo and ipe at 72 inches #50. Ive always wanted a really long bow just because, and it will be easier to tiller.
Ive profiled the boo to 1 inch wide a 12 (14?) inch riser parallel to mid limb taper to half inch.
Question is were should I place the block and clamp that pulls it down into deflex? Looked at every ones set up but no specs on that that I could find. Should it be a third of the way up? mid way? is there a formula or general rule for that? Roy's looks half way?
Also, how much should I put in there?

[John Malone]

Also would a q/s red oak riser work? Not that crap from Lowes the good stuff, I have a piece that's one inch thick.

[ty_in_ND]

John, you should take a look at Sam Harper's website (poorfolkbows.com). He has a BBI build along that is an R/D longbow that is fairly thorough.

As far as your handle goes, I don't see why qs red oak wouldn't work. I think you don't see it often because it's not purdy like those fancy exotic hardwoods. If you have it, use it!

[Roy from Pa]

I normally place the mid limb posts half way between the flares and limb tip. The closer you place the mid limb post closer to the riser, the more deflex you get. And the more of the limb that will work.

Being that you want a 50# with a 72 inch bow, you better leave the ipe thicker. 1/2" at least, maybe thicker.

The red oak will work.

[John Malone]

Thanks Guys, I noticed BMorv seemed to have his closer to the flares in a pic he posted on the bow swap thread.

[John Malone]

So I should place the post midlimb because its so long??

[Roy from Pa]

Ya that would be ok.

You just need to remember since the bow is so long and you want 50#, ya better make the belly lam a good 5/8th thick, or wider...

[John Malone]

Thanks Roy, I can get 5/8. I could shorten it if I really needed to but this piece of boo would be perfect for 72 inches. My other piece of boo is better, the nodes are all are pretty evenly spaced at 12-12.5 inches, I'm saving it for when I know more about what the heck I'm doing.

[Roy from Pa]

Make it the 72. You can shorten it later if you want or need more weight.

Start keeping a journal of bow dimensions, lam thickness, etc. And the weight they produce.

Them gwass guys call it stack. LOL

[John Malone]

I'm ready to glue fellows. But I'm still trying to figure out how much. Should the tips be 2 inches higher than the handle and the deflex post be one inch lower than the handle?

[John Malone]

Any one?

[Roy from Pa]

My center of handle post is 3 3/4", the mid limb posts are 2 3/4" and end posts are 5".

[John Malone]

Thanks Roy, I forgot it was Sunday.

[Roy from Pa]

No problem, was at daughters for her birthday party.

 

[Bob at Work]

Ipe is so dense, is there a chance that making it so long could give the limbs a bit too much mass creating a bit of thump?

[John Malone]

No idea Bob, but were gonna find out.

[BMorv]

Bob, ipe is dense but it's strength is in line with it's weight.  What I mean by that is you end up with narrow thin tips that are super aerodynamic and close to the same weight as any other wood, assuming that excess mass isn't left there.  The end result is a fast bow compared to other woods.

[BMorv]

Where are you on this one John?
I saw the comments made on PA about this bow and this length.  I agree that you won't gain much from the deflex with this long of a bow, and it will make the tiller harder to figure out.

[John Malone]

BMorv, That ipe is now riser and power lam material. Going by what was said on PA like you mentioned I decided to cut it down to 66. Just go ahead and learn how to tiller a real R/D that I could get the full benefits from. I tapered it down some more to allow for the shorter length, but as I was cranking it down at the mid limb post, CRACK! So that's where I'm at on this one. I started and finished in all of 30 minutes.
No need to fear though I have more wood.
Goining to make a new post For advice on lemon wood core lam thickness.
Its 7/16 tapering to 3/8 and I have ipe belly lams wht do you think?

[John Malone]

Oh yea, I was able to save the boo backing strip so that's a plus.