Riser length effect on performance {PICS ADDED}

[perry f.]

The first glass longbow I made was a mild R/D with a 26 1/4" riser fade to fade, based on the guys design that I bought form and hot box from. I haven't made anymore on that form, but want to make another with a 18" riser. How will it compare to the first one? Thanks

[heartlandbowyer]

26.25 seems a bit long, did he have a power lamb added to the back get to that length in his design? I think you'll have a better(smoother) working limb if you shorten your riser to 18. I would guess 26 on the riser would work if you were making a 68 plus inch bow. I've never made one that long though, maybe some of the other guys have some better thoughts on that. How did the last one shoot for ya?

[perry f.]

The last one shoots great. I always thought it was long, but I didn't know any better, there was no power lam. If I used the same stack thickness as I did on first one bow, how will it effect poundage with shorter riser.

[heartlandbowyer]

All things being the same except riser length I would say you will end up with a lower weight, how much is hard to say. I'll bet you end up 5lb less it's gonna be a different ratio than shortening the actual bow tip to tip. Hard to say how its gonna affect performance, depends on the bows shape, how the 26inch riser laid into the deflex ect. All of that will change with 12 inches less riser. One way to find out. :D

[perry f.]

The riser in first one has long fades kinda like a power lam

[Crooked Stic]

You will lose draw weight and preload. If the long one shoots and bends good I would not change it. Think about this. Lets say you had a TD with a 20 in. riser and 3 in. of wedge past each end then you effective riser length would be 26 in.

[Swissbow]

Just by making the riser shorter that much you will change completely the design and most likely it will not work. If you want to build a bow with a shorter riser I would suggest to take a proven design like Kenny's D/R-Bow or Binghams longbows as a starting point.

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Andy

[bjansen]

Also would love to see a pic of the form/ finished long riser bow.

[jess stuart]

A buddy of mine had a Jack Harrison longbow back before I began to build bows.  I remember it had a very long riser something like 24" or so shot great.  I think one would gain all the advantages of a longer riser by using a powerlam.

[perry f.]

 

Here's a pic of form, riser template and finished bow. I guess you could say it is like a power lam and riser together

[Shaun]

Long riser equals short working limb equals fast! The disadvantage is short working limbs do not push heavy arrows as efficiently and are not as smooth drawing. Jack Harrison's goal was to make a 200 fps long bow - his only goal. Every change that adds speed also subtracts from stability and power.

If you want a shorter riser, you will need to make a new form - fitted to the new riser shape.

[Roy from Pa]

I was at our indoor trad shoot this past Thursday night. There had to be 15 bows hanging along one wall. SO naturally I just walked down the wall checking them all out. I got to comparing all those bow designs to my old Bear Takedown hanging amongst them. It never dawned on me how long the riser is on my old Bear Bow. It has to be almost 3 feet long. I though holly crap that's long for a riser. But that bow is the best shooting bow I have ever owned. It's 68 inches tip to tip, and it is quick.

[Crooked Stic]

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  posted January 12, 2013 07:55 PM                        
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Long riser equals short working limb equals fast! The disadvantage is short working limbs do not push heavy arrows as efficiently and are not as smooth drawing. Jack Harrison's goal was to make a 200 fps long bow - his only goal. Every change that adds speed also subtracts from stability and power
Shaun that last sentence you posted what exactly are you basing that on?
Speed adds power and stability is in bow design.

[perry f.]

I bought this form from Randy Lotz. He is the brother of Mickey Lotz "The Ferret". He told me that it was modeled off a Morrison longbow. Never been around a Morrison, so not sure. Bow is fast, however, based on other people's stack info, I am way off when shooting for goal weight. Randy didn't have much stack info to go by, so there is still some guess work involved.  This design is fast, I just need to build a few more on it!

[bjansen]

Interesting.. I had a Morrison 58" longbow once and it has a 21.5" riser.  It had very little working limb but I really liked the bow and how it shot.  I do believe my Morrison had more deflex in in that the pics of yours (but just as much reflex). Thanks for the pics.