Gillo GT Riser 2019

JohnK

Well-known member
It still changes the position of the limb tips relative to the riser, so the limbs will behave differently at the extremes. Don't get me wrong: it's clear that some very good archers are having great results with it, but the engineering problem doesn't change.

I'd be interested to hear from an experienced and non-sponsored archer who has done some objective testing with limbs set at different angles.
 


KidCurry

Well-known member
I would be interested to know what my 42lb limbs would draw up at on the GT25. On Whitehart's figures it's about 35 to 47lb. Not sure why I would want to go down to 35 from my 41 OTF and I doubt I will ever get up to 46 unless shooting every day for hours a day. I'm in the market for a new barebow riser, but I'm not sure if I need a GT or want to spend that amount when a standard G1 is so much cheaper and do a perfectly good job.
Besides I'm not thinking for buying 46lb limbs in the expectation of winding them down to shoot at 41 and going up to 54lb. I suspect at £500 most GTs on the line will be shot by good archers already shooting about their optimum weight.
 


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geoffretired

Supporter
Supporter
Just wondering if the wide range of limb angle adjustment might be there to allow different brace heights as well as draw weights.
So for any draw weight requirement you could move the limbs, change the string length and get a different BH but on the same draw weight. It's a bit like changing a riser from reflex to deflex but without the need to replace a riser.
 


LAC Mark

Member
I can see this being a good barebow riser for a few reasons, one being tiller adjustment for large crawls, at present my tiller bolts are maxed out (one all the way in, the other all the way out) and I still need more adjustment.
It also has good weight to it.

And the most important thing, they look good and very few will have them, at least not yet.
 


geoffretired

Supporter
Supporter
And the most important thing, they look good and very few will have them, at least not yet.
Heehee. I like that sort of thinking. I suppose that is why manufacturers keep bringing out new stuff, even before the old version has become really popular.
 


Hawkmoon

Member
Very interesting discussion on the geometry but isn't it the point that as the pocket "tilts" the limbs will stay in the same plane as the poundage is increased or decreased so the effect on the limbs will be minimal if anything at all. Anyway good enough to win gold at the Roma barebow finals
You have to think what is happening when the limbs on a normal riser or a GT are wound in or out, the difference with the GT is that the whole limb pocket moves keeping the dovetail at a constant angle and possible giving better stability. What doesn't change is that as you wind the limbs in, without altering anything else the brace height will go up and as you wind them out it will go down. This will change the amount of contact that the string has with the limb and the pre-load. Until now most risers had a maximum of +/-5% and so limb manufactures have been producing limbs optimised for this range. The GT has the potential to take them way beyond this range and the concern is, you could be pre-loading the limb to the point that even before it is drawn you are into the working range of the limb and at full draw you may be well beyond it's designed working range (this is also true at the other end of the scale).
Time will tell if this is an issue or not, I cannot see many archers using the extremes as it would really screw with your tune, there is also the case that this riser costs about twice as much as a pair of EX1 limbs so if you are shooting a apair of 36lb limbs you could buy a pair of 30lb and a pair of 40lb limbs and have the same range of weight but possible a better tune with less compromise.
 


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geoffretired

Supporter
Supporter
As you wind the bolts in and out, I don't think the brace height changes that much. After all, the string is the same length, so the limb tips are held captive. With a bit more bend in the limb, the distance from butt to tip is changed very slightly. So a slightly different BH but not by very much.
If you adjust the pockets, fit the limb, then fit a string you can see how much pre bend is needed to string the bow. If it seems too hard to string, you probably have the wrong string for that setting at the pockets. Or the wrong pocket setting for that string.
 


JohnK

Well-known member
The BH definitely changes a bit, but more importantly, changing the limb bolt positions will *require* you to run a different bracing height. In other words, a bow with bolts all the way in will definitely need a different bracing height to shoot well than if its bolts were all the way out.
 


Iaincope

New member
I have a GT 27" on order, unfortunately Vittorio loves to make us wait so its around a 3 month back order by the time it arrives :)

I have been shooting a 27" G1 for some time along with Long Uukha Limbs @46lbs. I only have a 28.5" draw so in no way do I need a 72" bow for draw-length reasons, I just enjoy the stability of it.

Having read through the previous pages of this thread something has occurred to me that hadn't previously. The trade-off for me running a 72" bow with a 28.5" draw is that I never really get into the optimal working range of the limbs. With the GT I should be able to move the angle of the limbs forward (increasing the draw weight to 50lb which I am comfortable with). This would mean that I am in effect drawing the limbs further back and hopefully further into the optimised draw length for the limbs.

This all seems to make sense in my head at the end of a long, weary day. Can anyone see any flaws in my cunning plan?
 


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Stretch

Active member
Sorry, but IMHO no. You’ll get more speed because of the weight. You might get a tiny bit more efficiency because of the limb angle... but even on an Uukha limb that is way out of the designed profile. Effectively you’re underutilising the shape. However, it might be what works for you and Uukha do have strange recommendations for length vs draw length. The folks at Perris would probably have a better idea of how that would work from an energy/efficiency point of view.

Draw your bow back and get someone to take a photo. Then draw it another 4” and get someone to take another photo. Then overlay the photos and you’ll see how differently you’re working the limbs.

At 28.5” a 72” Hoyt would feel like a rubber band. And with a 27” riser I found a medium limb to be more stable at drawlength around 31.25”. At 32” a long limb is more stable and works in a 25” or 27” riser.

To get energy efficiency you’d need to drop to medium or even short limbs in the 27” riser. But efficiency is not the same as accuracy. You may even find that the setup makes you more comfortable at the higher weights. String angle may also be a sweet spot for you. So if you like it and it works for you, GREAT... stop thinking about it.

Only other drawback I can see is correlating arrow spine to the setup. But then you are kind of having to extrapolate with most of the hyper recurve limbs anyway.

2p

Stretch
 


Iaincope

New member
Sorry, but IMHO no. You’ll get more speed because of the weight. You might get a tiny bit more efficiency because of the limb angle... but even on an Uukha limb that is way out of the designed profile. Effectively you’re underutilising the shape. However, it might be what works for you and Uukha do have strange recommendations for length vs draw length. The folks at Perris would probably have a better idea of how that would work from an energy/efficiency point of view.

Draw your bow back and get someone to take a photo. Then draw it another 4” and get someone to take another photo. Then overlay the photos and you’ll see how differently you’re working the limbs.

At 28.5” a 72” Hoyt would feel like a rubber band. And with a 27” riser I found a medium limb to be more stable at drawlength around 31.25”. At 32” a long limb is more stable and works in a 25” or 27” riser.

To get energy efficiency you’d need to drop to medium or even short limbs in the 27” riser. But efficiency is not the same as accuracy. You may even find that the setup makes you more comfortable at the higher weights. String angle may also be a sweet spot for you. So if you like it and it works for you, GREAT... stop thinking about it.

Only other drawback I can see is correlating arrow spine to the setup. But then you are kind of having to extrapolate with most of the hyper recurve limbs anyway.

2p

Stretch
Let’s just wait and see what happens with a 29” riser and short limbs 😂

Thanks for your input, appreciate your thoughts
 


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