My first three piece take-down proto-typing!

[Apex Predator]

All right folks, I'm in the prototyping phase again. I'm developing a shorter D/R, forward riser, three piece longbow. I'm thinking 58" nock-nock. I drew up a riser that is 14" long. The bow will be built with 1.5" stock. My limb wedges are 8.25" long. I roughed out a pine riser this morning, but forgot to take any photos. I'll get you guys caught up tonight! I've got one of the pirate riser/limb drilling jigs. I plan to lay the mock-up riser on a piece of butcher paper and start drawing limbs until I hit on what I think is right. I'm thinking around 3" deflex, and bring the string nocks back to just above the back of the riser in reflex. I don't know what my limb pad angles are, because I just drew it out until I thought it looked right. I will know more tonight when I start drawing limbs.

1. What kind of limb pad angle are you guys thinking on this? I'd like to be able to make recurve limbs for this model as well.

2. The holes in my drilling jig are spaced 2.5" on centers, but I was thinking of going 2" between the insert and alignment pin, since the longer spacing is crowding my grip area. What are your thoughts on 2" spacing?

3. How short can I go on the limb pads?

4. The riser will be action-wood from Kenny. I plan to lay up the riser with a 3/16" phenolic I-beam. The riser depth will be 1.25" where the limb bolt insert will be. Is this enough depth?

5. Any good tips in general regarding this project?

I should get me riser block, wedges, and take-down hardware today from Kenny, so I will probably answer some of my own questions when playing with the parts. I'll post some photos of my riser tonight.

[walkabout]

sounds like a worthwhile endeavor. wish i could help but ive never built a takedown. im sure reverse engineering one will help you though, then from there you can change things to how you like them.as far as limb pad angle i think ive read most are 20 degrees, although someone who knows better can probably give you absolute specs. good luck and keep us updated on how it goes. looking forward to some future pics.

[Pennsyltuckey pete]

Marty,

Do you have the binghams pronouned LB plans?  I can dig mine out and take some coparative measurements if you would like.  The 2" separation between limb bolt and pin doesn't sound like an issue to me.  The locking bolt should easily handle the torque.  The only "downside" I see is the decreased accuracy for lining up the limbs.  With your craftmanship abilities I see no issue there either. good luck.

pete

[Apex Predator]

I think I am in somewhat uncharted seas here Pete.  The overall length I am aiming for is not common.  Isn't the Bingham plans for a much longer bow?

[Apex Predator]

Allright folks, this is where I'm at.  I scrapped the 14" riser in favor of a 15" one.  More room for grip and sight window.  I have 10 degree limb pads.  Here is a rough riser with the critical elements only.

 

 

Using the jig hole locations that I have ruins the asthetics of the riser.  I refuse to make the ends any deeper.  I think I can just shift the hole jig over 1/2" and have enough meat for the insert.  Here is the jig location, and the modified insert location.  What do you guys have to say about using two bolts, instead of a bolt and a pin?

 

 

 

Here is my first limb drawing.  The limb deflexes 1" behind the limb pockets and then reflexes 1/2" beyond the back of the riser.  That's 5" of curve.  The black line will represent a 60"AMO bow.  I plan to build a 58" as my mainstay on this form, so it will have the string grooves even with the back of the bow.

 

 

 
 
That is a lot of curve to my eye, but what do you guys think?

[walkabout]

i think for looks one bolt would be easier to make nice than two, however im sure it wont hurt overall to have two bolts. you could always build your prototype and change later to suit your needs based on your first one.as far as the limb reflex/deflex if its not far from any other bow you build it should be ok, far as i figure it wouldnt be much different from building any other bow aside from the bolts holding it together rather than it being one piece. everything ive seen you post has turned out great im sure no matter what you decide it will be fine. thanks for taking us along with the build.

[PZee]

Marty,

I love the design of your new bow. Very interesting that you've chosen to have the limbs secured on the 'belly' of the riser instead of the back. What was the reason for this? If it is just for looks, then you've made a good move!!!!!

As far as the bolts are concerned, (and this is from a very inexperienced bow builder) I would put the 2 in. My reasoning is leverage. Maybe I'm wrong and maybe a engineer could clarify this for us, but if you only used 1 bolt, in my mind it would have to be the one closest to the riser end. I'm not sure you have enough material at the end of the riser, so I would put both in. Thats just my opinion! Other than that, I'll be watching this with interest, as I love the look!

Pete

[Apex Predator]

It's been recommended that I make the limb pads shallower, to avoid having a 9" brace height.  I am sort of leaning that way, since it will be easier to make a recurve limb around the same riser.  Let's see what I can come up with.

PZee,  the forward riser design is unique in looks, but also makes for a very easy shooting bow.  They also point very well.  The design challenge is getting good early draw weight, and not winding up with too much brace height.  Everything is a trade-off between shootability and performance.

[Apex Predator]

Here is the latest.  I have incorporated several good suggestions into this third riser/limb profile.  I cut 6 deg limb pads on this one.  I left the limbs straight for a good portion, turned the reflex into a tighter radius, and reduced the net reflex by one inch.  The black line represents a 58" amo bow.  Here are the two risers side-by-side.

 

 

 

 

Top profile is prototype #1, and bottom is #2.

 

[kennym]

I can see you have put lots of thought in this!

I would use the 2 bolt also on a bellymounted limb. I would think less vibration and noise. Just think about all the posts of backmount limbs that squeak,pop etc. Those are pulling against the riser.

I agree on the foward handle being easier to shoot.

[Pennsyltuckey pete]

Marty,

how about using a pair of lugs or T nuts that are counter sunk in to the belly of the limb and then covered. In other words the bolt would go through the riser in to the limb.  this would  make the mounting hardware disapear.

pete

[Apex Predator]

I'm still taking belly steps Pete!  Next thing you will want is a carbon riser, and 90% let-off!    

That is a fancy system you describe, and I'm sure I'll be looking at a better way down the road, but right now I want to build my "first" three piece.  I may pick your brain later, but right now mine is about to explode.

[fish n chicks]

I am by no means as experienced as the guys who have already replied (it took me about 3 visits to this thread to figure out what a limb pad was! lol) but I must say that 10 degree pad sketch above the 6 degree one looks like it would draw smoother. maybe it's the more gradual bend of the limbs but it's also just appealing to the eye.

I would also recommend going with 2 anchors per pad than one for this engineerical (I make words as i need em!) reason:

Moments. You are going to creat a very big moment (which is a rotating type of stress found at your connection in the direction of your load) with one connection, and being that it is on the belly side i'm afraid you'll shear your inserts right out of your riser one day. With two anchors you're obviously dispersing the load over two connectinos per limb, greatly reducing your moments affected area.

On a side note, have you considered what your brace height would be? maybe that can help you decide which limb pattern you like?

Otherwise thanks for taking us along Apex!

[Apex Predator]

The brace height is driving the shallower angled riser pads.  I fear that the 10 deg pads will require a 9+" brace, which I want to avoid.  I think the 6 deg will work much better in getting near 8", which is more acceptable to me.  This is all conjecture until I strap a pair of real limbs on her though.  The shallower angle will also make it easier to fit some recurve limbs to this riser.  Most forward riser recurves have 0 deg limb pads.

[Jason Scott]

Apex, I've yet to try a takedown myself but I will give you my opinions though. I like two bolts too. Bob Lee and Palmers both do it and in my subconscious mind it just seems sturdier, of course they are bolting to the back which is opposite your design but I think it makes even more sense on the belly anyway. If you don't you will need at least three inches of pad from the bolt toward the center of grip for leverage. On the net reflex thing, I don't think it is correct to measure from the back of the riser as much as measuring from the back of the imaginary line as if you were to draw the arc from the pad angles through the grip. That apex point, pardon the pun, is the true back location. If you try to go all the way out to the back of the riser you will get a little radical in reflex.

[Apex Predator]

Good points Jason.

[TNstickn]

[ron w]

[Apex Predator]

I took a few hours today, in between the two other builds I have going on, and worked on my proto-type riser.  Ive got two layers of glass laminated in the riser and I plan to laminate at least two more on the risers back.  She has 1/8" phenolic limb pads.  Hopefully my drilling fixture will be done soon.  It will have three holes for drill inserts, so I can go with either two pins and one bolt, or two bolts and one pin.

 

 

 

[2treks]

What drilling jig are you getting Apex? Custom?
Looking good. Chuck