First Laminated Longbow. A Few Questions.

[b0whunter]

Originally posted by okie64:
 Heres a pic of a riser design typically used on wood bows. Top to bottom its hickory backing,purpleheart powerlam, cherry core, and hickory belly and  handle. Be careful adding a lot of reflex. It can make tillering a little tricky.

How thick were your laminations?  I think I can draw something up like that, but the lam thicknesses and limb widths, I am not sure of yet.  

I was hoping to come up with a design that would work with both wood and glass longbows, but from what I am learning, this may not be possible?

[okie64]

The backing is 1/8", core is 1/8", and the belly is 1/2". The belly lam doesnt have to be that thick. I'd rather have it a little too thick than too thin though. The powerlam is 1/4" thick in the middle and tapers to a feathered edge on both ends. You can probably come up with something that will work on wood and glass. I've only built wooden bows though.

[7 Lakes]

The 1/8" backing and 1/8" core are Red Oak?

Sorry but I'm developing CRS.   Can't Remember Stuff  

[b0whunter]

Mike,

Yes, the picture of the design showed 1/8" back, core and belly of all Red Oak for the practice run.  I have changed the design a little, lengthening the riser block to 18" and reducing the severity of the curves at the fades.   I also reduced the amount of deflex to 1" and changed the reflex to 3", so if it loses some to string follow, hopefully I'll still have a little left.  

I am also playing with a design using two tapered lams for the core.

[7 Lakes]

Think about backing the Red Oak lamination on the back.  Maybe linen or silk.  Something that will not apply more compression to the belly.  

I'd be a little worried about the Red Oak on the back with nothing to hold down tension splinters.  

Increasing the riser length will also cut down on the working length of the bow creating even more of a tension problem on the back.  So does the additional reflex.

I know you are using three laminations but I'd start thinking of this as a unbacked Red Oak board, which is what it will be after glue up.

[b0whunter]

Mike,

Would bamboo T-molding, like they use for doorway thresholds between two rooms of hardwood flooring work as a backing?

[7 Lakes]

That's a dang good question.  Give me a day or two to go down to Lowes and take a look at it.  I can't quite picture (in my mind)how it's glued up.  

I'm thinking any wood will add compression to the Oak belly.  Maybe a very thin piece of Hickory.

[7 Lakes]

That's a dang good question.  Give me a day or two to go down to Lowes and take a look at it.  I can't quite picture (in my mind)how it's glued up.  

I'm thinking any wood will add compression to the Oak belly.  Maybe a very thin piece of Hickory.

[okie64]

I'd kinda like to know if that bamboo flooring will work on bows too. I kinda figured it would probably work good for belly wood but I'm not sure about backing?

[7 Lakes]

Okie64 the Verticle cut flooring will work for a bow belly.  It actually makes a pretty snappy bow that's easily rasped and tillered.  It needs a backing & I like Hickory.  You have to use the expensive flooring.  The cheap stuff at Lowes is full of glue voids.

[rimes]

Would this be an example of the bamboo flooring you could use to make a bow with?

   

Kris

[b0whunter]

Would a red oak core with hickory back and belly lams work?

[okie64]

Yeah that would work fine. Hickory is not the best belly wood but it will work. Ive used it as belly wood a few times. You just have to be  careful tillering or it will take a lot of set.

[b0whunter]

Ok, thanks.  I picked up a bunch of hickory today and a little bit of ash too.  Would ash work better on the belly?

[okie64]

I dont think it would be any better than hickory but I'm not for sure. I've made selfbows from ash but never tried it as a belly wood in a laminate. I've heard of people using ash as a backing for lighter woods like cherry.

[b0whunter]

OK, thanks for the help.   I finished my form this evening.  I built one like 7 Lakes showed in his link earlier.  I was going to start on my bow, but things went to crud.  I was trying to make my own tapered lam, using 4 small shims that I planed down with my lam grinder (.072" down to .018" , spaced 9" apart).  It probably would've worked, but the piece of wood that I was using to make the tapered lam was to thin and would just bend in between the shims.  I guess I'll have to buy one to use to make them.  In the mean time, I guess I'll just use parallel lams.

[7 Lakes]

Ash makes a nice belly wood but leave it wide.  You can thin down the Hickory a bit.  Are you still looking at making a three lam bow?  If so The Ash needs to be relatively thick compared to the backing and core.

[b0whunter]

Mike,

Yea, I'm planning a 3-lam bow, kinda like the one in the picture that okie64 posted.  

The place I got the wood from also had a bunch of maple.   Is maple good for bows?

Thanks,
b0whunter

[7 Lakes]

Maple will make a fine bow if left wide enough.  But perhaps you are asking the wrong question.

You are looking for 3 bow woods with different properties.  Just because one is a good backing doesn't make it good on the belly.  I would think in this application Maple would make a good, thin core lamination. Your real problem here is to find a belly wood that can be cut thin enough to go up the belly side of the riser that's also strong enough in compression to stand the pressure from the core and backing.  For that I would look at Osage or Ipe.  

In a three lamination, all wood bow you need a combination of wood.  A backing that's strong in tension.  It's thickness is determined by the strength of the Belly Wood.  The belly needs to be strong in compression or it will be crushed by the backing.  Some of that strength may be substitued by building the bow wider with longer working limbs so the compression can be spread out.  Thickness does matter on the belly.  The core cannot be very thick or it takes away from the compression strength of the belly wood.

[b0whunter]

Mike,

I am going to wait until I get some tapered lams and some fiberglass to build the bow with the belly lams that run up the fades.  

I decided to do one similar to the picture that okie posted. It is a more conventional all wood tri-lam longbow.