Ilf riser question

[kennym]

Are all or most ilf risers made with the same pad angle?

[Orion]

Within a range of pad angles, but not the same, in my experience.  The pad angles usually change with the riser length, and between bows of different makers even of the same length.  Not always, and not a lot, but occasionally.

[kennym]

Hadn't given a thought to riser length. Any idea what the angle would be on a shorter, say 17" riser??

[KevinK]

I am not an expert on ILF but have been researching them. Supposedly a 17" riser gains 8# over the marked weight on limbs rated for a 25" riser. So 8 inches shorter, 8 pounds heavier or 1 pound added for every inch below 25". I think they change the angle on 15 and 13 inch risers so they are smoother and don't gain as much weight, etc. Also some say they gain only 1/2# of 17" rated limbs (8-1/2# of 25" rated limbs) for 15 " risers, and 1# (17)/9#(13) for 13" risers. Dryad states that they are 8# over for all riser lengths if I am reading their website correctly. So for that to happen I think the limb angle has to change. I am curious to see what someone more knowledgeable than me says. Any time I get interested in ILF I do more research and it exhausts my mind and reminds me why I switched from my compound to traditional.

[kennym]

LOL , I know what you mean. I built a set of longbow limbs for the 17" riser I have, but don't like em all that well. So thinkin on how to redo form and things.

[katman]

I have found it a little frustrating figuring out weight gains on various makers risers due to the limb pad angles. Best to talk to the designer. No standard that I know of. Most ilf risers are built for recurve limbs. Check out borders ilf longbow limbs for pics and look at the limb butts thickened to add preload.

[kennym]

Thanks, I knew I was going to have a funky wedge to pull it off....

[Orion]

kenny:  I don't think there's any agreed upon standard.  The pad angles will be close, probably within a degree or two for the same riser length, probably more than that between a very short vs a very long riser, but different builders/manufacturers use different angles.  Time for the AMO to get involved.  Maybe it has and I just don't know about it.    

[Roy from Pa]

Where are the ilf risers measured from, end to end or limb bolt to limb bolt? I am having my compound riser converted into an ilf riser and I am clueless about how these different length limbs work out? I know for a given set of limbs, that a shorter riser will yield a higher draw weight than a longer riser will. After that I'm lost.

[Orion]

Not sure about that, or whether folks do that consistently either.  On Bob Morrison's site, his metal riser ILF bows are 1.25 inches longer than their designation.  For example, for his 15-inch riser, he says the OAL is 16.25.inches.  

Thus, he has 3/4-inch more length on either end of the riser than the designated length of the riser.  The limb bolts aren't located that close to the end of the riser, but the center of the slots that hold the limb might be.

   

[TOEJAMMER]

On my wood ILF risers made by Bob, they are marked 13" and they measure 13" from end to end.  No idea on metal risers or other makes.

[M60gunner]

Lay the riser on its side. Draw a line from each pad. Where they intersect measure that angle. Divide by two, then subtract from 90 degrees.

[M60gunner]

Lay the riser on its side. Draw a line from each pad. Where they intersect measure that angle. Divide by two, then subtract from 90 degrees.

[KevinK]

Originally posted by Roy from Pa:
Where are the ilf risers measured from, end to end or limb bolt to limb bolt? I am having my compound riser converted into an ilf riser and I am clueless about how these different length limbs work out? I know for a given set of limbs, that a shorter riser will yield a higher draw weight than a longer riser will. After that I'm lost.

Measure distance between the limb bolts on center and add 5 inches. To determine approx AMO formula is (limb length x2)+(riser length - 5) inches.
Shorts are 23", Mediums 24", Longs 25" for ILF limbs
Source:
 http://www.skyarchery.com/questions_answers.htm

[Scott E]

limb pad angels vary depending on manufacturer. Some risers have more deflex than others.

Generally when going from a longer riser to shorter riser add one pound of draw weight per inch of riser.

So from a 21 inch riser to 17 inch riser you'll gain 4lbs in draw weight.

[Roy from Pa]

Thanks, Kevin.

[kennym]

Originally posted by KevinK:
 

Originally posted by Roy from Pa:
Where are the ilf risers measured from, end to end or limb bolt to limb bolt? I am having my compound riser converted into an ilf riser and I am clueless about how these different length limbs work out? I know for a given set of limbs, that a shorter riser will yield a higher draw weight than a longer riser will. After that I'm lost.

Measure distance between the limb bolts on center and add 5 inches. To determine approx AMO formula is (limb length x2)+(riser length - 5) inches.
Shorts are 23", Mediums 24", Longs 25" for ILF limbs
Source:
  http://www.skyarchery.com/questions_answers.htm  [/b]

Good info right there!

[BenBow]

Kenny I made plans to build an ilf longbow limb that bends right off the riser so that the limb matches the profile of my 17" riser.  According to supertiller it will match or exceed the performance of my takedown now. There's something to think about. I don't know if or when I'll have time to follow up on it.
BTW I plan on keeping the limb width at 1 1/8" or less.

[kennym]

Yep Galen, after my first go thinking I could do it by manipulating taper and wedges, I found the limb will have to bend at wedge .

[Wheels2]

One of the reasons that I like Morrison risers is that he varies the limb pad angle with each riser length.
Very little or any difference in draw weight going to different riser lengths.