# ILF Riser planning



## hannibal smith (May 20, 2015)

Getting the materials together for my riser build-

Hunting bow
50# Recurve utilizing ILF (Tradtech Blackmax Carbon medium) limbs
99% set on a shelf- maybe a rest?
Attachments for quiver

When I get the limbs delivered I will have a better idea, but I am just starting to get some ideas together.

Tentative riser height 17"
Pocket angle 15-17-19-21 deg.???? (this is where I am at an impasse)

Any input?


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## hannibal smith (May 20, 2015)

Back on the planning! 

Got the limbs. They weigh 7.8oz. each, and are short! If I go with my initial planned 17" riser, I will have a very compact bow at 56" (not strung).

Tentative plan is 3-3/4" preload if my brace height is 8-3/4"-

I like the limb angle if I go with 20 deg. pockets, but I am just guessing on all of this. This is my first time messing with ILF limbs.


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## guyver (Jan 3, 2012)

Trad Talk is a similar forum that may offer you some good info regarding limb pad angles.


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## hannibal smith (May 20, 2015)

guyver said:


> Trad Talk is a similar forum that may offer you some good info regarding limb pad angles.


Thanks. Stuck on machining an all aluminum riser, or an aluminum/walnut hybrid......................hmmmmmmm


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## hannibal smith (May 20, 2015)

Just finished making my ILF pocket interface. My bow will utilize an aluminum/walnut combination for warmth in the hand, and the rigidity of an aluminum riser.

I am making snag free limb bolts that won't get caught up in the grasses of where I hunt.

Each interface weighs 2.9 oz. Riser weight should be around 2 pounds, give or take.

Pictures are horrible, but you get the idea.


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## 4nolz (Aug 17, 2011)

This is very impressive.I think 20degrees might not be the best choice. 17 or19 better.Awesome skills.


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## summertime416 (May 28, 2015)

Wow.. that is very impressive. I want to see the finished project..


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## hannibal smith (May 20, 2015)

4nolz said:


> This is very impressive.I think 20degrees might not be the best choice. 17 or19 better.Awesome skills.


Just did the math. If 20 degrees is baseline, then 17 degrees will have my 56" bow's limb tips "higher" by 0.9424" - Gaining about an inch of preload from the 20 degree design, brace height being equal. These numbers are only relevant to a 56" bow.

Hmmmmmm.

Just did some more math. With a target brace height of 8.75", I am getting 2.006" (20 degrees) of preload vs. 2.946" (17 degrees)-

This is where the deflex/reflex of the riser comes into play, and this is where I am kind of in the dark for ILF limbs. I can make any preload I want by just adjusting shelf/handle location, but where I am just kind of winging it is on preload distance. Any thoughts????


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## st8arrow (Apr 25, 2005)

Very impressive work !!


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## hannibal smith (May 20, 2015)

Just measured one of my favorite bows, and it is running right around 3" of preload (static to brace)-

I should just shoot for 3" maybe. I can keep my 20 degrees and just move handle/shelf back, or keep that and go to 17 degrees. My draw is 28-28.5" on a recurve, so either way I go, I don't think it's going to stack.


Ok. I am going to just move my handle/shelf back to get my target preload. This keeps a little mellower limb angle (20 degree), but also gets my grip more "vertical", not so boomerang if you will. I prefer a more vertical grip anyway.


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## Markliep (May 6, 2012)

I think 17deg is an average LPA for oly ILF style risers - have seen lower angle reccomends for ILF LB risers in the 13-15 deg range vs recurves - riser deflex is interesting too - recently acquired a 21" SF axiom with 2" deflex vs my oly rigs with 1.5" and it's a more forgiving set up - last bit to is to make sure your limb pads themselves are in the same plane...the first riser I made had good alignment & it worked out well ... for my second one I paid more attention to routering out limb pockets & got the limbs angled off centre ... that ones sitting on the work 
bench still - have fun - M


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## hannibal smith (May 20, 2015)

Markliep said:


> I think 17deg is an average LPA for oly ILF style risers - have seen lower angle reccomends for ILF LB risers in the 13-15 deg range vs recurves - riser deflex is interesting too - recently acquired a 21" SF axiom with 2" deflex vs my oly rigs with 1.5" and it's a more forgiving set up - last bit to is to make sure your limb pads themselves are in the same plane...the first riser I made had good alignment & it worked out well ... for my second one I paid more attention to routering out limb pockets & got the limbs angled off centre ... that ones sitting on the work
> bench still - have fun - M


Thanks for the info. Doing the math, it seems that my riser deflex/reflex numbers seem to trump limb pocket angles in the 17-20 degree range. When I start running the numbers with the limb length, then everything gets magnified. This is my first trip into making an ILF riser, so I am kind of working backwards it seems. If I was making my own limbs, I could make it work with just about any riser angle or offset. I think as long as I am in the ballpark, I can adjust brace height to fine tune it.

Maybe go 18.5 just for peace of mind. The reason I am so hung up on 20, is that I determined this angle "blind", it's just what happened after I inputted what I wanted, and the math came back.


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## hannibal smith (May 20, 2015)

I had an accidentally perfect chunk of Black Walnut in the stash. It is from an old growth monster tree. The grain orientation is perfect. 

I am going to square it up and get it cut for lamination in the mill.


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## visionquest69 (May 17, 2015)

hannibal smith said:


> I had an accidentally perfect chunk of Black Walnut in the stash. It is from an old growth monster tree. The grain orientation is perfect.
> 
> I am going to square it up and get it cut for lamination in the mill.


Ok, so I am really interested to see how this turns out.


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## Stub (Aug 13, 2013)

Same here. Tagging this tread on tapatalk!


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## BarneySlayer (Feb 28, 2009)

hannibal smith said:


> I should just shoot for 3" maybe. I can keep my 20 degrees and just move handle/shelf back, or keep that and go to 17 degrees. My draw is 28-28.5" on a recurve, so either way I go, I don't think it's going to stack.


I am probably missing something, but you're using short samick limbs on a 17" riser with a 28-28.5" draw, and you're not going to stack?

Is this an uber deflexed design that's going to minimize the power stroke, or are you using less preload than normal with these limbs?

Just wondering.

Looks like a really cool project


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## JParanee (Oct 13, 2009)

Looks interesting 

I'm tagged to follow


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## grantmac (May 31, 2007)

I would not decrease deflex since it's an important part of stability. If anything I'd got for as much as you think you can achieve with those pockets and make the pockets steeper to compensate.

-Grant


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## hannibal smith (May 20, 2015)

After reading what Border had to say about the deflex riser, I understand what he was saying. He covered a super important aspect that I totally missed in my planning.

I neglected to maximize the configuration when the bow goes static. I used a 20 degree angle to compensate for my reflexed riser (reflex by .300") to get a brace height that wasn't too short, and with a preload that wasn't crazy. I could always use 60# limbs to get a 50# bow.

I have not cut my riser in the mill yet, because the epoxy is still curing, and I have not finalized the design.

I am going to tweak my numbers, and optimize the limbs from draw to static.

If this riser comes out cool, I am going to get some Border limbs.


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## DDSHOOTER (Aug 22, 2005)

grantmac said:


> I would not decrease deflex since it's an important part of stability. If anything I'd got for as much as you think you can achieve with those pockets and make the pockets steeper to compensate.
> 
> -Grant


I agree. You can always change the pocket? Well I have totally different look for the pocket. 
Dan


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## visionquest69 (May 17, 2015)

Really looking forward to seeing this. Curious as to the mill you are using. How many risers have you made?


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## hannibal smith (May 20, 2015)

visionquest69 said:


> Really looking forward to seeing this. Curious as to the mill you are using. How many risers have you made?


That one is a HAAS VF2 in the prototype room. I don't design/make bow stuff for a living, I manufacture other fun stuff. I just do projects at night with my machines to chill out.


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## visionquest69 (May 17, 2015)

Any progress on this?


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## 4nolz (Aug 17, 2011)

I'd love to see you mill a "wedge adapter" to fit the riser pocket to allow any ILF limb pocket to be adjusted to 2-3 different angles(or 2-3 different wedges) and accept standard ILF limbs.I think it would sell.


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## visionquest69 (May 17, 2015)

4nolz said:


> I'd love to see you mill a "wedge adapter" to fit the riser pocket to allow any ILF limb pocket to be adjusted to 2-3 different angles(or 2-3 different wedges) and accept standard ILF limbs.I think it would sell.


Yes, or why not place a an adjustable thru riser limb fulcrum bolt to allow infinite adjustment of the limb angle.


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## BaconPower (Jun 9, 2015)

Make sure you laminate your walnut riser otherwise 50# will crack it. Also laminate the boards "cross-grain".


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