confused

[mergy]

Hi Eric:

I'm confused on layout showing XX for drill angle on SYMS.

How do you start the layout if not using the PIN 2 CG line to start the Drill Angle?

Another ?, is it always best to place the CG(on SYMS) near the center & midline?

Thanks 4 help!

[Dustin]

Hi Eric:

I'm confused on layout showing XX for drill angle on SYMS.

How do you start the layout if not using the PIN 2 CG line to start the Drill Angle?

Another ?, is it always best to place the CG(on SYMS) near the center & midline?

Thanks 4 help!

xx is listed as drill angle because the PSA on a sym. cored ball ends up in or close to the thumb hole after drilling. Just place the cg in a position where you would like depending on if you plan on using a balance hole or Motion Hole or no hole at all. You could also reference the Most Versatile Sym. Drilling that Mo had posted on another thread. viewtopic.php?f=13&t=11114 Post #5.

[JohnP]

For symmetricals I find it easier to revert to the old pin to PAP and pin to cg system to locate the PAP on the ball, then draw the pin through cg line and use the angle to the VAL to complete the layout. Pin to PAP determines the amount of the flare potential that is used and affects the length of the skid phase, pin to cg positions the cg for potential use of a balance hole, and the angle to the VAL affects the second transition. This is a very easy system to use if you have an armadillo, a little more complicated if you have to draw the arcs with a compass. -- JohnP

[EricHartwell]

If I do not know Pin to Cg distance and top weight I don't want to give a recommendation that might throw the static weights so far out you have to have an undesirable weight hole or worse yet a ball that ends up illegal on static weight with a max size hole.

When I give a layout with xx as drilling angle I guess I expect the driller to understand static weights well enough to place the Cg accordingly.

Should I give the Drilling Angle as measured from the Cg for Symmetrical layouts?

[JohnP]

Using the system I described in my earlier post it's fairly easy to figure how to position the cg. Look at the horizontal and vertical components of the PAP. If the vertical component is fairly low keeping the cg to PAP distance equal to the horizontal component will position the PAP close to the grip centerline. For example, if the PAP is 5" over and 1/4" up using a cg to PAP distance of 5" will put the cg very close to the centerline, while using a pin to PAP of 4" will put it almost 1" away from the centerline. As the vertical component increases or decreases a smaller cg to PAP distance is required to get the same cg distance from the centerline. For example if the vertical component is 1 1/2" up I would probably use a cg to PAP of 3 1/4" to move the cg 1" from the centerline (rough estimate). When the layout is complete you can always test the weights on a dodo scale before drilling. The side weight will be almost exact and the finger weight can be estimated (if you want to get very close, compare the weight to be removed by the thumb hole against the weight to be removed by the finger holes to adjust the weight determined by the dodo scale). -- JohnP

[mergy]

O.K., my dense head still doesn't grasp. I understand placing CG near center for BH. So lets do a 4 example. I get a SYM ball and it has drilling instructions with it. So 4 instance,I select a 60x4x30 drilling from the manufactures list. So now with Prosect I draw a line from Pin thru CG & now place prosect point on Pin & align with Pin to CG line & select 60' & draw line from PIn to 60 degree. Then measure 3" down this line to get Pin to Pap. Revert Prosect & place point on 3" mark & select 30' to get Val. Now on Val,drop down from 3" mark & mark vertical PAP number. From that mark,go left for RHer & mark Horz. PAP & midline. from Horz.PAP mark,use prosect to make centerline. Now from MIDLine point on Centerline,measure up & down to get cut-2-cut fingerholes. Now,with modern thoughts(XX) when I have ball drilled, I do not have layout selectd as PSA moves to thumbhole WO BH.
So,now that I have the thumbhole marked,do I now start layout over & mark Pin thru Cg to thumbhole & place point of prosect on Pin & using line to thumb & select 60' to get Drill angle & rest of layout as described above?
Need help Understanding the XX for drill angle.
BTW,my ball driller is old school & haedheaded,but my friend. I lay out my balls & he's got the drill press!
Anyways thanks for help!

[snick]

I usually develop symm layouts in reverse on a fitted ball.

ie: VGL, midline, VAL, PAP, desired VAL angle, desired PIN-PAP (fake pin), then draw the drilling angle to position the CG for the desired static weights.
Measure the drilling angle.
You can then use this information to layout the blank symm ball.

[DarkHorse]

O.K., my dense head still doesn't grasp. I understand placing CG near center for BH. So lets do a 4 example. I get a SYM ball and it has drilling instructions with it. So 4 instance,I select a 60x4x30 drilling from the manufactures list.......
Now,with modern thoughts(XX) when I have ball drilled, I do not have layout selectd as PSA moves to thumbhole WO BH.
So,now that I have the thumbhole marked,do I now start layout over & mark Pin thru Cg to thumbhole & place point of prosect on Pin & using line to thumb & select 60' to get Drill angle & rest of layout as described above?
Need help Understanding the XX for drill angle.
BTW,my ball driller is old school & haedheaded,but my friend. I lay out my balls & he's got the drill press!
Anyways thanks for help!

As far as anyone can tell, whether you drill that ball 60x4x30 or 30x4x30 or 180x4x30, the difference between the layouts should be fairly minimal. Changing the surface of the ball would have more of an affect.
On a SYM ball, the drilling angle for a supplied layout, as in your example, will rarely be the actual drilling angle, as measured to the PSA, once the ball has been drilled. That's OK, don't worry too much here.

So when someone suggests a layout of XX x 4 x 30, on this forum, the bowler is supposed to understand that CG placement has a minimal effect on ball motion, and therefore can use whatever drilling angle gets a CG placement that allows use of a particular balance hole, or none at all. Since this angle would vary based on PAP and span length, a generic XX is given.

I have some SYMs laid out with 110 drilling angle, because that puts the CG on the centerline to set up a Motion Hole, or on a 50 to use a hole down the VAL to rev up sooner.
There is no need to lay the ball out twice to get the drilling angle to line up with the thumbhole.
Personally, I throw away almost all drill sheets included with bowling balls. Most drill sheets are like house balls - drilled to fit everyone equally poorly.

Clear as mud yet?

[ads]

I was confused before.

Undrilled Sym ball has no PSA (that's why it is symmetrical). But once it is drilled, it has a PSA and happens to be somewhere near the thumb hole. Paradoxically, you need a reference point to layout the drilling angle but you can't have that reference until you drill the thumb hole.

My driller lays out sym ball using CG to determine drilling angle. He doesn't understand xx-5-40. I have to give exact drilling angle. For example, I gave him 80-5-40 for my IQ Pearl. How did I come up with 80* drilling angle?

1. Use a drilled ball, mark my PAP from the grip centerline
2. Draw the VAL from my PAP
3. Use the target VAL angel (40*) and PAP-PIN dist (5") to spot the virtual PIN location (don't bother the real PIN on the ball)
4. Mark a virtual CG , 0 or 1/2" away from the grip centerline (the virtual CG can be further away if you want to have more side weight to drill a bigger balance hole)
5. Draw a line from virtual PIN to virtual CG. Get the virtual drilling angle (80*).

My common virtual drilling angle of sym is 70-80* (depends on the undrilled side weight) for 40* VAL angle and 5" PAP-PIN. This usually leaves less than 1oz positive side weight. So, I can omit the balance hole if not necessary. For other VAL angle and PAP-PIN combination, the virtual drilling angle will probably be different. Will repeat the above steps.

The undrilled side weight does affect the result. My first guinea pig, IQ Pearl has quite some undrilled side weight . Even with 80-5-40, it left a bit more than 1 oz side weight. A very tiny balance hole is drilled to make it legal (7/8 oz). My guess is the final dual angle is ~70-5-40. I bowl it on THS with #4000 grit and adjust the surface if necessary.

[DarkHorse]

I was confused before.
...
The undrilled side weight does affect the result. My first guinea pig, IQ Pearl has quite some undrilled side weight . Even with 80-5-40, it left a bit more than 1 oz side weight. A very tiny balance hole is drilled to make it legal (7/8 oz). My guess is the final dual angle is ~70-5-40. I bowl it on THS with #4000 grit and adjust the surface if necessary.

Even better - I have found that marked CG's are often incorrect.
Usually less than 1/4", but I've had a couple off by over 1" which could definitely cause an issue.

If you want to make sure any ball won't NEED a balance hole, you must check static weights after layout and before drilling, and be aware of how much the gripping holes affect these numbers.

[mergy]

thanks all ,the lite finally went on!

[Deerehunter]

I think I am following but I have some questions now:

I am experimenting with a plugged sym. ball that has a 4" pin to CG. I placed the PAP 4" from the pin and 4" from the CG. I drew the line through the pin and PAP and then marked out a 35 degree angle to VAL. I measured down the VAL 1.5" and over 5" to get my grip mid point and marked out the proposed grip. As JohnP mentioned, the CG is about 1" from grip centerline. Using the thumb as the MB, the drilling angle is about 80 degrees. If a balance hole causes the MB to migrate somewhere between the thumb and BH, would equal size thumb and balance holes put the MB in the middle? This would yield a drilling angle of about 50 degrees (my sym benchmark - 50 x 4 x 35).

My benchmark asym layout (45 x 4 x 40) has the MB 2.5" from the thumb hole. If the MB migrates on this ball when the thumb hole and any required balance hole is drilled and is dependent on the size of the holes, does the dual angle system already loosely account for such MB migration (does the benchmark layout yield the approximately correct drilled ball angles, or are the benchmark angles the desired final result of the drilled ball)? With a sweetspot of 85* +/- 20*, could MB migration throw the ball out of the optimum range? Should theoretical MB migration be designed in to the ball? What is an undesirable balance hole? What is the max allowable balance hole? Are my questions above insignificant to ball design and surface?

I hope I am communicating my questions clearly. Thank you for any answers.

Kevin

[EricHartwell]

I think I am following but I have some questions now:

I am experimenting with a plugged sym. ball that has a 4" pin to CG. I placed the PAP 4" from the pin and 4" from the CG. I drew the line through the pin and PAP and then marked out a 35 degree angle to VAL. I measured down the VAL 1.5" and over 5" to get my grip mid point and marked out the proposed grip. As JohnP mentioned, the CG is about 1" from grip centerline. Using the thumb as the MB, the drilling angle is about 80 degrees. If a balance hole causes the MB to migrate somewhere between the thumb and BH, would equal size thumb and balance holes put the MB in the middle? This would yield a drilling angle of about 50 degrees (my sym benchmark - 50 x 4 x 35).

My benchmark asym layout (45 x 4 x 40) has the MB 2.5" from the thumb hole. If the MB migrates on this ball when the thumb hole and any required balance hole is drilled and is dependent on the size of the holes, does the dual angle system already loosely account for such MB migration (does the benchmark layout yield the approximately correct drilled ball angles, or are the benchmark angles the desired final result of the drilled ball)? With a sweetspot of 85* +/- 20*, could MB migration throw the ball out of the optimum range? Should theoretical MB migration be designed in to the ball? What is an undesirable balance hole? What is the max allowable balance hole? Are my questions above insignificant to ball design and surface?

I hope I am communicating my questions clearly. Thank you for any answers.

Kevin

Max size balance hole 1-1/4"

Yes you can consider the MB movement for the intended ball and its specifications and how the layout will affect it. Adjust as necessary.
A ball with higher mass bias strength will result in post drill numbers like the layout intended.
Weaker cored Asyms you can compensate with the layout and predict the end result. Much like Symmetrical layouts and positioning the Cg to plan a balance hole to get the reaction your looking for.