Riser/limb length and preformance

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Longtrad
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Riser/limb length and preformance

#1 Post by Longtrad »

I'm not sure how these two correlate. it seems every other thing I read says something different. Now i'm confused.


Some say shorter limbs are faster since they have a shorter distance to travel.. something to that effect, others say longer limbs are faster and store more energy. So which is it? or are there more factors to consider?

Captainkirk
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Re: Riser/limb length and preformance

#2 Post by Captainkirk »

Sounds like a question for Tony or Kirk (Lavender)
Aim small, miss small!

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Ole Dave
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Re: Riser/limb length and preformance

#3 Post by Ole Dave »

I agree with Cap'n... that is a gnarly question and I'd bet some $$$ that there are varied factors that come into play...

Kirk (Bigfoot) is one who not only WOULD share factual information, but if he had the time, he'd willingly share the why's and wherefores of it all.

My recent Semi-Static designed for the different riser block angle of the Sasquatch LB riser (which has some kick ass 47# LB limbs I love) is only 60" and that sucker forced me to go UP in spine over arrows tuned for other bowyer's 48-50# bows!!!

Now I have the semi static and wanted them to be 37 or 38# to keep me in the game longer...

Kirk wanted to give me the most energy possible with the drop in weight, so he made those limbs come out for a 64" bow... to if I recall his words correctly, "capture the most energy for that draw weight".

I'm betting big time there are a bunch of things... I'd also bet that there is just not one simple answer and most guys just don't have the time, money or inclination to build and test, test, test, the way Kirk (Bigfoot) has to find out the facts!
All we have and call our own, once belonged to someone else, and will again. Our purpose here is not to serve ourselves.

Bigfoot SAS LB (47# LB limbs 38# Semi Static RC limbs)

Couple of old Bear bows

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Shadowhntr
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Re: Riser/limb length and preformance

#4 Post by Shadowhntr »

Ive always believed short limbs are a bit faster, and long limbs are smoother shooting. In both, I think its only a slight difference, unless absolute extremes are compared. It will be interesting to hear Kirk weight in on this.
The element of surprise can never be replaced by persistence.

Big Foot
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Re: Riser/limb length and preformance

#5 Post by Big Foot »

Well..... There are a lot of factors to consider regarding a bows over all performance, and making a blanket statement that short limbs are faster than long limbs , or the other way around would be like saying sports cars go faster than pick up trucks.... It really boils down to what's under the hood.

Now if you were to take 3 ILF risers of the same make and model at 17", 19" & 21" for example, and 3 sets of limbs made by the same company in long, med, & short lengths. typically the short limbs on the 21" riser will give you the best speed because the energy is stored in a shorter working section of the limb, and the longer riser limits the limb travel.....

The mitigating factors are draw length, draw weight, and the stacking point of the limb design.
How the bow is set up, and how much pre-load on the limbs at brace is a huge factor too.... with one piece bows or TD bolt down set ups, it all boils down to the bowyers limb design , amount of pre-load, & type of materials used to build the limbs....

Bottom line is i have built 52" to 68" long bows, & 48" to 66" Recurve bows that varied in speeds from 190 to over 200 fps in every length , make and model..... Mot of the extremely fast bows seem to be longer bows with shorter working limbs, drawn to 30-32" with high pre-load or early weight..... btw..... higher draw weights from mid 50's to mid 60's are generally going to give you better performance on the average limb design because the pre-load is higher, and the energy transfer to the shaft itself much is higher....... if you guys are wondering what this "Pre-load" or early weight thing is all about.... well simply put... the tighter the string is at brace, the higher the pre-load is... that tension on the string is what stops the limbs dead and transfers the stored energy to the shaft..... If you got any vibration or hand shock at all, that is stored energy staying in the limbs & going back into the riser instead of the shaft.... Wasted energy....

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Shadowhntr
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Re: Riser/limb length and preformance

#6 Post by Shadowhntr »

Big Foot wrote:If you got any vibration or hand shock at all, that is stored energy staying in the limbs & going back into the riser instead of the shaft.... Wasted energy....
I have been saying this for several years now. Nice to hear it come from a reputable bowyer....

Awesome Post Kirk. Thanks for taking the time to explain it in a good and understandable way. I learned something.
The element of surprise can never be replaced by persistence.

Carpdaddy
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Re: Riser/limb length and preformance

#7 Post by Carpdaddy »

Good explanation Kirk; thanks.

Big Foot
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Re: Riser/limb length and preformance

#8 Post by Big Foot »

One of the biggest disappointments of my life was finally getting my hands on a very high end bow from a very popular bow maker only to find the grip hurt my hand and the vibration in the limbs was terrible. The tiller measurement was only an 1/8" positive, but i could see the limbs were out of balance BIG time.... I can't help wonder if somebody had tried to reduce the draw weight on it and screwed those limbs up... it was sad....... The guy was bragging about how cheap he bought this $1200 beauty...... It didn't shoot worth beans.

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