Indo Persian Glas/wood/carbon Lam

[JacobkurtD]

Hi,
Im new.            

Ive been experimenting with composite horn bows the last couple of years, and  they still have most of my interest, but learning to make such a bow  takes next to forever! So i decided that this time i wanted to spend money on materials that im most likely going to get a bow out of at the end of it.            


But i need some answers that i haven't yet come across on the web.

Ive chosen to stay with the composite/horn bow/horse bow shape (indo-persian)   and for any that don't know, they have a rather short bending section. Only half the limb bends, and the other half is the rigid recurved tip.

Pic to get the idea:
  http://www.grozerarchery.com/index_b.htm  
So my question is: How flexible is a fiberglas/wood/carbon laminated limb? The bending section in each limb is 30cm (not including the fades of the handle and recurved other half of the limb)

Do you think Glas/wood lam will bend like that in the pic?

Correct me if im wrong, but to get this eventual thing to full draw, there will have to be a fair bit of de-flex set in the limbs, no?
Can someone say how i would need to set the limbs in the form?
Any help here would be amazing!
( i Know this won't be the most efficient bow with these materials, but it will look good i promise!!)      :D      

The stack is: (also criticisms an suggestions are welcome)

BACK
Clear glas: 1mm/.039"
Walnut vinier: 0.6mm/.0236
carbon: 0.35mm/.0137"
CORE: Bamboo (back side) 1.5mm, glued to Osage(belly side) 1.5mm/.0590"
Carbon: 0.35mm.0137
Walnut vinier: 0.6mm/.0236
clear glass: 1mm.039"
BELLY

Overall width= 3.8cm/38mm/1.496"     And length 58"

If someone could tell me about how heavy the draw would be on this, i would really appreciate it!!!! (i also don't know if tapered lams would help this design with regis tipps? if so i would de 2mm/.7874-1mm/.039"
 I saw that post with the calculator, but i didn't want to sign up and I've got a mac and don't think its compatible....??

Any suggestion on my whole project would be really helpful!!!
Thanks in advance,
Jacob  

[scars]

Glass is capable of the bend. I have an Attilas archery U-finish bow. At full draw the both kasans eye are past parallel. Active sal is about 33cm or 12" same width as yours.
However mine is only 50.5 inches when braced and is 55# at 30" and I draw it to 32" with no sence of stack.

I am building a glass horse bow like you. But I am using the one I have as a template to help me out. I do not know how much the carbon will help. I do know that the siyahs will be able to address the stability of the bow.

My riser is reflexed at 20 degrees, including the fades it is 33cm. The sals are 33cm and 34cm. My siyahs including fades are 23cm. My thickness is 5-6mm. In the sal the width is 38mm to midlimb and then tapers to 19mm-20mm. But I am using ipe and maple for the core and .030 glass for back and belly and it is my first glass bow. Not sure if I am of any help to you. But that is my measurements.

[fujimo]

i have one of grozers bows, a sort of a combination between his mongol and his hunnish bows. it is the only bow that i have ever bought, and it is a superb bow, nice to shoot and FAST!!
so if there is anything i can help you with, measurements, templates drawings, pictures- just let me know and i will see how i can be of some help- but with the design of it- there are a lot of very experienced glass builders on here- give them time, and they will all clock in at some point.

[scars]

fujimo
They are snappy.3 under and split does pinch some but thumb ring is nice. Makes a nice thump!!

[fujimo]

i have never tried a thumb ring- sure would be neat- i shoot 3 under.
i almost hate mine-'cos it shoots so well but someone else made it. in fact have been tempted to sell it a few times, then i always remember how well it shoots, and makes a great ambush type bow!

which one do you have?

[KenH]

Here's the glued-up shaped core of the Yanghai Scythian profile replica  I'm building.  It's 44" end-to-end and will finish just over 1" wide.  This is the Mark II prototype.  The Mark I was far too strong for my taste -- drew over 75#.  The stack was .24 -- .03 glass on back & belly, plus the 3 x.06 wood core and an extra piece foot long piece of .03 wood at the handle as a 'riser'.  The Mark II stack is a .125 core with .03 back & belly glass.


  [/url] [/IMG]

[scars]

fujimo,
I have attilas Ufinish bow It looks like the balgarian hun bow. Handle is on the belly side of bow. here is a pic of the Attila bow:
  [/url] [/IMG]

And here is a bow started with the same shape to the kasans or fade to the siyah before I messed it up. It is .005 thicker at the midlimb on the left limb, somehow I missed the sanding to thickness on that limb.
  [/url] [/IMG]  

 KenH,

Now that looks nice You should start a bowyers log (blog) on the build.

[JacobkurtD]

Thanks guys!
Its good to know that it will take the bend!
Those U finish bows are quite interesting! I guess it is necessary to taper the limbs i that bending section?? would that be done by hand or by thicknesser?? does that mean i should order parallel lams?

This is the strung profile i aiming for (just done with rope and cutouts  

 

This is my main question, if i should do a small reflex in the riser and deflexed limbs? Or straight riser and a tiny reflex in limbs??

[JacobkurtD]

Pic didn't work, here is a link:
 http://www.flickr.com/photos/photosarestories/12011206586/

[KenH]

Any thickness tillering you do by sanding.  For Horsebows like these I prefer parallel lams.  If you need to taper you can, but if you bought tapered and need to add, it's really hard!

Scars - .005" wouldn't bother me!  Nice looking build.  What did you mess up?

I'm taking pix as I go along, and plan on posting a sort of Build-along once I'm done.  Waiting now for a warm enough couple days to glue-up the glass to back and belly.  It has been cold enough the last week (even here in FLorida) that I couldn't glue, since I do not use a curing box.  But Tomorrow and Monday are supposed to be back to low/mid 70F.

Fujimo - Personally I like a bit of set back in thd handle/riser.  For you, not as much as my Scythian, but about like the setback on Scars' bows -- say an inch.

[scars]

The ufinish bow Has 3 lams and it has: parallel, custom, parallel. with a 6" tip wedge from 0-.3/8" thick. On my blank I wanted the main part of the bend to be right below the mid limb. So I was sanding the ipe to make it thinner at that point. The thickness measurements at midlimb on the right side is .246 and on the leftside it is .251. I think I sanded the same limb twice and right after glued the glass on. Nothing to do but sand the sides down on the left limb. The main part of the core is ipe and it does make a difference. Binghams says you can sand the glass but with this short of a bow I am not sure if it is worth the attempt. So it will sit till I have more knowledge.

I don't have much confidence in my limited knowledge of glass or horn bows. So I made the core up and shaped it on the forms glued it all up with unibond 800. Did some lite tillering to see where my bends would be. Then used smoothon to glue the glass to the core.

Jacob I think the choice of handle reflex and deflex is up to you. Your choice should conform to the style you are after. The more parallel your lams are the closer to the riser fades the sals will bend. I choose to reflex my handle to move the bend farther out and deflex the midlimb with thinning of the core right before the mid limb to help direct where I wanted my active part of the sal to be. I am not sure if my thinking was correct but it seems like a logical process.

Binghams has a chart for lam thickness that will get you in the poundage you are looking for. Then there is super tiller an excel sheet to work out your specs.

I have 4 bows to make plus my swap bow so this project is going to be put on hold for awhile.

[JacobkurtD]

So finally finished the bow (unstrung) shape.Here is the outline for the form. what do you guys think?

Too much de-flex?

 http://www.flickr.com/photos/photosarestories/12036137143/

jacob

[scars]

I don't think you need the deflex in it if that is the profile you want. Most of your active limb will be near the fades, so I think tapered lams would be a good choice for you. It will get more of your sal active in its bend.

Some food for thought, with siyahs at that angle of degree you might want to use some kind of fastners to keep them attached. I'll post a picture of how Attila made his connection.

Also can you make a mock up of it with your string profile and make sure that at brace the string is off of the kasan area, and where the string loops would touch the siyah. Same principal and rules apply as with horn and sinew.

[JacobkurtD]

Thank you Scars!!
I was also thinking the same about the reflex. I just really wasn't sure if such a 30cm sal could bend that much without horn and sinew???

Also with the siyahs. i am sandwiching them between the glass, also with fades just like at the riser end.
So does that mean it would bend still mostly at the riser fades?

Here is a link to my inspiration:

 https://plus.google.com/photos/100344514090479456506/albums/5622949266958961985/5622949288083984962?banner=pwa&pid=5622949288083984962&oid=100344514090479456506

That bow just bows my mind!!!!!!!  

How much of a taper would you recommend?  (45-50lbs ,039 glass, 1,57" wide)

Jacob

[JacobkurtD]

I was also planning on laying down a 0,00079" Carbon fiber sheet under the glass on the back to give the arrow speed a small boost...

would that be too complicated? Ive read in a couple of other posts that carbon creates a lot stress between belly and back,
Does anyone know if that one layer would be ok?

Or not worth it?

[scars]

I don't know anything about carbon, I think you would get more responces if you post that as a single question.

I don't think you need more than .002 per inch on your taper. You just want to get your whole sal working together.

On the link you posted you if you look at his string at brace. The string touches the kasan, you don't want that to happen. That's what I was wanting to see with your mock up. His bow when releasing the arrow will slap the kasan so loudly it will wake the moose up in northern Norway. 5 degrees less of and angle on the siyahs more curve where the string loop contacts the siyah will solve that and may reduce the brace height.

Personally I think you could put more reflex into it and give it more stored energy. Preloading your bow is what composite bows are about. Glass can handle it. I'm going to refer to adams book I think it was in the 2nd chapter. the limbs of a ottoman bow would have to move almost twice as fast as the limbs of a English longbow to achieve  the same results. That means go thicker and narrower. The glass now a days is uni directional the lams if straight grain all help in limb twist prevention. Your siyah is the main area for correction so keep them wide until you get your string aligned.

[JacobkurtD]

Hmm, Thats true with the siyah. Ive had a little play around with it and have got a new "less contact" siyah shape now..

 http://www.flickr.com/photos/photosarestories/12048543625/


Also have made the unstrung limbs straight with a tiny deflex at the fades. for the first one with glass i don't want to push it too much.

I also recall that info in Adams book, I just didn't know, because modern recurve limbs are quid wide and thin...??

This is real good 2nd and info scars, thanks!!

[scars]

Yes, they look like they will work. I believe your back profile will stay the same. And you will still capture the image of the bow that inspired you.

I thumbed through your gallery, and remembered your horn bow from atarn. Loved the color contrast and horn in the siyah.

Modern recurve is wide and thin  but I think the siyahs have a lot to do with stableness. Back in the late 70's early 80's I had two bear recurves. The Attila bow feels better than both ever did.

[JacobkurtD]

Thanks! It still isn't finished.... in still shredding sinew!! For some reason it takes me FOR EVER!!  the strands always break in the middle... haha anyway...

So everything i want stacked in the core ads up to 7.5mm, which would be a rather high draw weight!!! Do you think i could just keep narrowing the limbs till i get to about 45-50 lbs??

With that stack, (7.5mm) the core is 3mm thick... could i go thinner with the core?

here in germany i can only find gordons bow tuff glas in 1,3mm

should i just use 0.8mm bear paw glass?

[scars]

I think you should go thinner with the core 6,5mm
Thinner if you go with the carbon. I would keep it at 35mm to 38mm wide.

Gordon is .050" here or 1,3mm over there. with the short active limb we are after I think with just the glass alone you are already at 2,6mm even at 6,5mm totals your going to be close to 50 to 55# but at 38mm you will be able to get your bending where you want them.

Maybe fujimo can post some measurements from his bow.