Modifying a Bow Riser?

[Matlax]

Hey bowyers, I’m looking for some advice. I have a bow that’s cut 3/32” before center and for the life of me I haven’t been able to eliminate the arrow kicking left when shot bare shaft. It’s a R/D long bow, 48# at 28” drawing to 29”. I shoot carbons and have done 1/4” cut increments from full length with as much as 362 gn up front with 400, 500, and 600 spine arrows trying to clear that riser to no avail. I’ve also varied BH 7-1/8” to 8-1/2” to no avail. Is there risk to using a dremel or file to remove some riser material to get a little closer to center shot? As much as 1/8”? I hate modifying the bow and feel like I’m covering up for my inadequacy but if there’s no harm, I’d like to give it a shot. Riser is wenge and cocobolo. Edge of shelf to opposite side is 1-1/8” and narrowest part of window is 7/8” (angle of pic makes it look 3/4” but it’s 7/8”). I’ve removed the Velcro and shot bare and with just stealth tape and still get the arrow tail kick to the left and slo mo video confirms it. Level 2 instructor watched me and says form looks good, definitely not anything that would cause contact. So aside from covering up tuning inadequacy, is there risk to safety or bow performance? Thanks!

[Matlax]

Is it such a silly question no one will even answer? 🤣

[Stagmitis]

Not silly- I have tuned bows that were 1/2 outside of center- assuming your form is good, you understand bareshaft tuning and have played with your nock point I would look elsewhere- string alignment and grip shape in particular- unless you’re an experienced bowyer and understand the design tolerance I would not touch the bow- I think the issue is elsewhere

[Stagmitis]

Btw if you’re right handed and the arrow is kicking left it’s presenting weak- cut a 400 spine to 29 1/2 “ with a standard non weighted insert and a 125grn head and see what happens

[Stagmitis]

Yet one more consideration Lol- pad the riser out to 1/8” or so. You might need to move further out from center not closer

[Matlax]

Yet one more consideration Lol- pad the riser out to 1/8” or so. You might need to move further out from center not closer

Thanks! Hadn’t considered building out. Definitely willing to try anything at this point! Could you explain the physics or reasoning for building out? Really appreciate it!

[Kirkll]

This will explain the spine difference the best…. There is no reason to consider touching your bow… that should tune well with 500 spine shafts, and 600’s will be weak even with 150 grain points.

https://youtu.be/rqO6WkXJ87A?si=SuaMSkGtpSYvBUY_

[dbeaver]

Stag has this one nailed.   Your pushing 50lbs at your draw length stiffen those babys up or give them something to bend around

[Stagmitis]

Matlax building the riser out causes the arrow to bend more, increase in paradox, and present stiffer.

[Matlax]

Thanks guys! Everything I’ve seen and been told is to go weaker for more paradox. Today I shot a 32” 500 spine bare shaft with 250 gn up front and foot powder sprayed on the shaft. The riser contact is 18-3/4” to 23” back from the tip (pic below yellow shows contact, black is the rest of the shaft). I was expecting the contact to be at the tail. Is it possible it’s flexing around then beginning to correct (flex inward) before clearing the riser? Bow is cut 3/32” before center. Thanks again!

[Stagmitis]

If your BS is tail left it’s weak- I would suggest going to the opposite extreme with a very stiff arrow and get the tail to present to the right, then start weakening the shaft- A 500,32”shaft with 250grns out front and close to center shot would shoot out of a 40lb bow. If you truly draw 29” the bow is pulling around 51lbs

[Kirkll]

Now here is a silly question for you.... How are you placing your hand on the grip? Are you wrapping your hand clear around the back of the riser and gripping it hard? If so, you are torquing the riser into the arrow as soon as you release.

There is no reason you shouldn't be able to tune arrows to to that bow... something weird is going on here...

[Matlax]

Thanks everyone for weighing in. I pulled out some old 30” GT hunters in 340 spine. I put a 50 GM screw in weight in with a 150 gn point and bare and fletched are now grouping great! Definitely stiffer than I thought I would be! Kicking myself…when I noticed the issue with my 400’s, everyone was telling me I was overspined until I came here. Wasn’t expecting to get to 340 but it’s shooting great.

[dbeaver]

nice work man