PETE WARD
PETE WARD
"WELCOME TO MY OUTDOOR WORLD"
My Thoughts on ILF limbs and Short Riser setups.
With the popularity of the ILF limbs today on short risers I think there is some misunderstanding on just how to set up the short riser with the ILF limb. Perhaps it is me that is not getting it.
This system has been developed for Olympic/FITA bows that have longer 23 to 25"+ risers.Recently there is a trend to use it on short risers, ranging from the 20" , down to the 14" riser.When we take a limb that was designed for long risers and place it on a short riser the weight increases.The ILF system also allows us to adjust the draw weight even more, and this is where we can get into trouble by over stressing the limbs on short risers.
We enter the danger zone in 2 ways, the first is by choosing a limb that is too short for our draw length. The second is by turning in the limb bolt like a compound bow and paying no attention to our draw length.
From my research on how to set up an ILF bow I have come to see that quite often we have bows that are set for far more pre stress than they should have.
My understanding on ILF limbs and efficiency is that these limbs are designed so that they perform at their best/optimal efficiency just before they start to stack. We have become used to a bow stacking at a higher pound per inch than where an ILF limb is stacking, so often it is not recognised without a scale.
These limbs draw very smooth and normaly gain close to 2# per inch if the right length is selected for our draw length. When we see a 3# increase the ILF limb is starting into it's stack and 4# is definately entering the danger zone.
The Border HEX V ILF is the exception to this.It was designed for a DAS 17" riser.However it is imperitive that you follow the Border draw length/bow length giudelines for all Border ILF limbs.
With other makes the draw length and bow length plus stacking need to be adhered to.
Ilf limbs are available in extra short, short, medium and longs.
DAS has a guide that keeps us within 12 pounds maximum of the stated 25" riser weight on it's bows.
Trad Tech has a guide that defines the limb length for its'risers based on draw length.
To achieve a proper set up bow that is not going to have a short life we need to make pre load adjustments for our draw length, and keep out of the stack. Those of us with short draw lengths have less concern than the guy with a 30 or 31" draw. The adjust ments are not there to achieve the maximum weight possible at all draw lengths.They are there for tiller adjustment and a smooth stack free , efficient limb setting.
For my 27" draw on the Titan I will normaly have a medium length limb on the 17" riser set at or near the maximum draw weight depending on the limb. It will start stacking at just past 27"". On a short limb I will have the limb bolts backed out about 3 turns so that it is not developing stack untill just after 27". I am not over stressing the limbs this way. A long limb would be turned all the way in but it is not a best choice as I am not drawing into it's effeciency range.
When a shooter is drawing lets say 29" the Medium limb is his best choice with the long also being in his draw length range. A short or extra short limb is definately not the right choice here.In this case the 29" draw would most likely be set with the medium limb backedout a couple turns from the minimun, or heaviest setting, or the long limb would be screwed down at or close to the maximum weight setting.
The 30" draw will be best suited with long limbs turned in close to maximum and a longer draw will begin to back out the limb bolts acordingly.
We need a scale to properly do this.
I read and hear of people that do not pay any heed to limb length and pre load settings.Some have limb failures some don't, and some don't talk about the failures. If you want a heavier draw weight buy heavier limbs.
I like to think of the adjustment the ILF allows as a draw length adjustment rather than a draw weight adjustment.
I will attach the charts and information from Morrison, Trad Tech, Das, and an excerpt from Sid at Border
Morrison ILF Riser and limb combinations Below is a direct quote from Morrison Archery's site. All "A " limbs were specifically designed for the short draw shooters to increase arrow speed and performance @ a maximum draw length of 26". They are were not designed to be used at draw lengths over 26" . Listing below are not recommended draw length , They are the actual Maximum Draw length...... Exceeding these maximum draw lengths will void your warrantee.
ILF Riser and limb combinations Riser Length Sight Window Riser Bow Length / Maximum draw Length Mini 14 2 1/2 14 52/26 54/28 56/29 58/30 60/30 62/30 A Short 16 2 1/2 A 54/26 56/28 58/29 60/30 62/30 64/30 B Med. 18 3 1/2 B 56/26 58/28 60/29 62/30 64/30 66/30 C Long 20 4 1/2 C 58/26 60/28 62/29 64/30 66/30 68/30 Combination of riser and Limbs Limb Size A B Short C Medimum D Long E F Brace Height 6 1/2 -7 6 1/2 -7 6 1/2 -7 6 1/2 -71/4 6 1/2 -71/4 6 1/2 -71/4 Trad Tech Titan Manual reference
Determining Correct Bow Length and Setting Draw Weight & Tiller
Bow Length:
Your choice of bow length is a personal one, guided primarily by your draw length in order to get your best shooting performance and smooth draw that doesnt stack increasing draw weight above 2-3# per inch.
For archers with less than a 26.5" draw, a 58" bow (short ILF Limbs, 66"/25" riser) is recommended.
For archers with a 26.5-29.5" draw, a 60" bow (medium ILF Limbs, 68"/25" riser) is the most popular.
For archers with a 29-31.5" draw, a 62" bow (long ILF limbs, 70"/25" riser) is generally preferred.
Additionally, the limb bolt position modifies the ILF limb angle. The shorter your draw
length within the range of any limb length above, the more pre-load can be built into the limb
angle by shooting your bow near the top of the weight adjustment range to slightly increase
performance. At longer draw lengths within any range, shooting the bow toward the bottom half of
the weight range will minimize any stacking and provide peak overall performance and shootablity.
Draw Weight:
Your
TradTech Titan bow features a 17" riser that results in a shorter bow and extremely efficient use of world-class ILF Olympic Recurve Competition Limbs. To convert the weight for an existing ILF limb to your TradTech Titan, add approximately 8 lbs. to the weight posted on your ILF Target limbs for a 25" target riser. If youve ordered your bow complete with our TradTech Limbs, then the base weight and bow length are accurately marked on the bottom limb label. In general, purchase limbs on the lighter side as you can increase the draw weight from 2-5# over the base weight. For shorter archers with less than a 27.5" draw, shooting the bow in the top/heaviest ½ of the weight range will yield added performance by building pre-load into the limbs increasing stored energy for you. For draw lengths over 29", shoot the bow in the bottom ½ near the base weight for the smoothest, most comfortable and forgiving draw cycle. Add or subtract ~2½# of draw weight for each inch of draw length that is over or under 28" as measured to the backside of your bow.(26Ό" to grip pivot or plunger hole + 1 Ύ")
Border Archery Recomendations from Sid.
Limb length needed for your set-up. The results may vary depending
On manufacturer and model
The paragraph below is copied form the 3 Rivers Daala Manual
Maximum Allowable Draw Weight
The maximum draw weight attainable at your draw length with any given limb must not ever exceed
±5% of the limbs set draw weight at 28". To do so voids the warranty, and may result in bow damage or
personal injury. An example would be a 50# Dalaas weight being adjusted outside of 47.5 lb - 52.5 lb.
The maximum allowable draw weight on the Dalaa is 66#.
|
Limb weight (H25) ή |
34 |
36 |
38 |
40 |
42 |
44 |
46 |
48 |
50 |
|
ί Draw / limb length ί |
|
|
|
|
|
|
|
|
|
|
25 (S) |
37 |
39 |
41 |
43 |
45 |
47 |
49 |
51 |
53 |
|
26 (S) |
38 |
40 |
42 |
44 |
46 |
48 |
50 |
52 |
54 |
|
27 (S) |
39 |
41 |
43 |
45 |
47 |
49 |
51 |
53 |
55 |
|
28 (S or M) |
40-42(M) |
42-44(M) |
44-46(M) |
46-48(M) |
48-50(M) |
50-52(M) |
52-54(M) |
54-56(M) |
56-58(M) |
|
29 (M) |
44 |
46 |
48 |
50 |
52 |
54 |
56 |
58 |
60 |
|
30 (M or L) |
45-47(L) |
47-49(L) |
49-51(L) |
51-53(L) |
53-55(L) |
55-57(L) |
57-59(L) |
59-61(L) |
61-63(L) |
|
31 (L) |
47 |
49 |
51 |
53 |
55 |
57 |
59 |
61 |
63 |
|
32 (L) |
47 |
49 |
51 |
53 |
55 |
57 |
59 |
61 |
63 |
By now it should be clear they winding down the bolts to the maximum setting without paying attention to draw length and choosing a limb that is to short seems to be the wrong aproach. Choose the right length limb for your draw length, set the pre load for a stack free smooth draw where the limb is at it's most efficent setting. If you want more draw weight , get a heavier limb, and use a scale.
I have tried to show as much information as possible. There are some varriances between manufacturers but the botton lime is they all have reccomendations.
Not one reccomends a 30" draw and a short limb at the maximum setting.A bit of comon sense is all it takes to extract a safe and sensible setup for you and the bow. Failures can and will happen no matter how we set up the bow, but we can do our part to minimize the risk.
When limb failures are hapening on 25" risers it is easy to see that the probability just increases on shorter risers.
The choice is yours to make, but if you go outside the recomended limb size and weights I do hope that you are honest about it and don't ask for warranty if problems arise.
Because you have adjusted the bow to one particular set of limbs it does not mean that you can swap limbs out without cheaking the settings for the new limbs. Each set of limbs is different, and they may require a new setting .
I hope that you did not get the impression that I don't like the ILF limbs. I think they are excellent, and the choices they offer us is wonderful .
Pete Ward
"Welcome to my outdoor world