DAS Tuning Procedure (feel free to add/edit)

[blue_ridge]

With all the wealth of info on this forum, I think it would be helpful if we could get all the experts to contribute to a comprehensive tuning procedure. Start in the beginning, as if a new bow, and go step by step with all the little tidbits of helpful knowledge and advice that is so often given on this forum. Maybe it could become a useful classic that people could refer to in the future.

I'll give a basic overview to get things started, (but I am not an "expert" and would appreciate all the input we can get from those that have mastered this process.

1. Tiller - is the difference in limb weight between the upper and lower limb. this is measure by comparing the distance from the string to the very base of each limb. The longer the distance, the lighter the preload. A rule of thumb is to set the tiller to 1/8 to 3/8" positive for split finger because you're drawing the upper limb farther due to the nocking point being above center string. With three under, an even tiller is the rule, because you're drawing closer to center string, thus the limbs should draw closer to even. Of course this varies from one person to the next and one bow to the next. An exceptional description of tiller tuning by David Soza is here: http://www.tradtalk.com/forums/showthread.php?t=13991

2. Preload - this is how far the limb bolts are turned in/out. Once the tiller is set, you should always turn the upper and lower limb bolts the exact same amount. It is also a good idea to check the tiller again any time you change the preload. Generally, the shorter your draw the more preload is recommended. Longer draws use less preload. Of course, it also depends on the length of your limbs. (Refer to the bow and limb manufacturers recommendation for draw length range.) Preload adjustment is intended to maximize the performance of the limbs for your draw length. One way to test this is to back the limb bolts all the way out and measure the weight at your draw length. Then turn both bolts in one turn and measure the draw weight again. Repeat this until the bolts are all the way in. Now look at the weight figures for each measurement you took and see if there was a flat spot where the draw weight did not change as much. This is likely the sweet spot for your draw length. An exceptional explanation for limb preload by David Soza is here: http://www.tradtalk.com/forums/showthread.php?t=7710

Note: at this point you will need to be able to shoot some arrows to tune for brace height and nock point. It you plan on using an elevated rest, then you will need to install it. If using a plunger, you will be best served to set it to the maximum spring tension. Some people actually remove the spring and insert a piece of matchstick so there is no spring tension in the plunger, for initial tuning purposes. Also, to set the depth of the plunger, look at the bow so the string is centered in the libs vertically. Now nock an arrow and adjust the plunger so the arrow is pointing just slightly to the left of the string (for a RH bow)

3. Brace Height - I believe the DAS manual suggest 7 1/4"-7 3/4" for a17" riser and 60" limbs. Short Draw pointed out that short limbs (58") would likely need slightly less BH and long limbs - more. In addition, a 21" DAS BH range is more like 8 1/4"-9". I set my 17" riser BH to 8 1/2" initially, figuring this beyond the high end of the BH I will eventually settle on. I shoot some arrows without any string silencers. Then I just listen to the bow. I adjust down in 1/4" increments and shoot a few more arrows listening and feeling for excessive vibration and noise. Usually I can find a BH that seems to be the quietest.

4. Nock point - Usually somewhere between 1/4" and 5/8", although lower or higher is not unheard of. General rule is to start with a high nock point, 5/8" and shoot some fletched and bare shafts at 10-15 yard target. If the bareshafts group high compared to fletched shafts, then nock point needs to be higher and vice versa if bare shafts group low.

5. Bareshaft tuning should continue after the up/down flight for nock point is set. You still need to get the left/right arrow flight tuned. Generally a shaft too stiff will fly left compared to fletched shafts (for RH bows). Too weak of a shaft will fly right comparably. You can weaken a stiff shaft by adding point weight. You can stiffen a weak shaft by shortening it, reducing point weight and adding a shaft wrap on the nock end. So, it is easier to stiffen a shaft than to weaken one. You will want a shaft that is very slightly weak (right) because when you add fletchings to the shaft, the added 10-20 grains of the fletchings will slightly stiffen the shaft (similar to adding a 10-40 grain wrap) You have to balance these considerations with your desired final weight of the arrow. If you string walk or gap you may even need to consider the desired final length of the arrow if you want a certain point on distance.

6. Plunger tuning - great explanation of plunger tuning here: http://www.tradtalk.com/forums/showthread.php?t=9751

7. Fletching bump - As the arrow passes the rest, the fletching could hit in such a way as to cause the fletching to jump up. You can rotate your nocks to adjust the angle of the fletching so this doesn't happen. Shoot at a target a few yards away and if the arrow is angled noticeably downward you may want to make some adjustments for better flight.at some point during or after tuning you may want to check for fletch bump. More common with off the shelf shooting, many elevated rests shoot cleanly enough that this isn't a problem, but if you don't check it, you could be compensating for it with a higher nocking point.

The above can be improved upon, and is only a rough draft. I will defer to anyone who wishes to add or change anything written above. The idea is to provide a sequential procedure to help people set up their bows. I've specified DAS because it is what I have and includes such things as Preload, tiller and plunger adjustments. it would most likely work for many bows out there. There is a lot more that can be added by more knowledgeable people than me. So please, add your comments. You can even copy and paste what I've written and re-write anything you see fit.

[Short Draw]

Paul

An excellent description on tuning a DAS.

Only addition I can think of is the brace height stated is for a DAS Master 60 inch bow and for a 58 inch bow it is less and the 62 inch bow has more.

For an Elite it is 8 1/4 to over 9 inches. Some use more, some less. I shoot 8 1/2 on a Elite with long limbs.

Brace height will also quiet the bow and you can move your arrow impact point with brace height.

Erich

[blue_ridge]

I figure some people will have some more insight on the various tuning sections or add some new sections. I'm still learning how to best tune the elevated rest and plunger. There are some people who know a lot more about nock to string/serving fit and tuning nocks to avoid fletching bump upon release, etc.

[bradd7]

Great description blue ridge...just what I have been needing!!!

Thanks for taking the time and energy to post this!

[van_fl]

First On my Elite with long limbs the brace height that tuned the best for me was 7.25 in.
The other thing is I use a 3/16 nock height.
I have tested from 7-9 inch brace and end back to 7.25 -.5 inches every time.
That’s shooting with arrow rest and plunger.

[bradd7]

I set, then lost, my sweet spot when I cranked the limbs all the way in. Short Draw helped me find it again with the simple words,

Crank the limbs all the way down then start turning each one 1/4" out at the same time.

Yep, got my sweet spot back at zero tiller, and now my 35lbs feels like I am pulling and holding 20lbs! Amazing!

Thanks Erich!

[Short Draw]

Bradd
I think it should be 1/4 turn out until you hit the spot.
Erich

[bradd7]

Opppssss....yep! Sorry!

[Free Range]

I have a question. I got a DAS used, the tiller is neutral, so I know that both limb bolts have been turned the same amount if any change was ever made to them, before I got it. My question is how do you know how much they have been turned if any? In the owners manual it says to not turn the bolts past where the set screw will engage the limb bolt. But since I can’t see the bolt while it’s in the riser how do I know when I’m getting too close? Can I loosen the set screws then crank the limb bolts all the way in until they bottom out, then start from there? I guess what I’m asking is where is the factory set point and how far each way can I go?

[Short Draw]

Free Range

You have a maximum of three turns in the adjustment.
From the bolt full in where you still can remove the limbs without resistance to full out should be three turns. You can add another turn but I wouldn't recommend it.

I usually tune my limbs to 8 pounds over for Winex at 28 inches.

Samicks are a little heavier so maybe 6 pounds over.

Under 28 tighten the bolt and over 28 loosen it off.
Most limbs will be in that range.

You need to know your draw length and get close to what you want the limbs to achieve.
Plus 2 pound for over 28 inches, minus 2 pound for under.

Preload is one of the neat things you can achieve with this bow and it will dial in any weight you want with the proper limbs and lets you tune the bow to the arrows too.


What are your stats? Draw length, poundage and length of bow.

Cheers

Erich

[blue_ridge]

Edited and added some more info to the procedure. Found a wealth of awesome and in depth explanation of some crucial tuning steps that were already in the Classics section. So I posted the links in the procedure for some of them. Man there is some good info in the Classics section!

[Free Range]

Thanks Shortdraw, bow is 62” one set of D limbs, one set of (I think F) limbs, I will have to check, anyhow the “F” limbs come in at 59lb at 29.25” draw. My draw is 29.25 to the center of the plunger button. I haven’t weighed the D limbs yet from what I can tell in the DAS owners manual they should come in around 48-49lb.

[blue_ridge]

Free Range,

Any way you can measure the draw weight at 29.25" starting with the bolts all the way out and then turn them in a 1/4 turn at a time to see if there is a flat spot? (like described in step 2? and in great depth by David Soza in the Classics link?) You'll get great performance from that sweet spot. Just make sure you've got some idea of your proper tiller first.

[Free Range]

Yes I can. I’ll see if I can do that this weekend. As for proper tiller, I’m going to leave it at neutral for now I’m not at all sure I know enough to know the difference minor adjustments to tiller would make.

[blue_ridge]

Me either, about tiller. Reading David Soza's classics thread on the subject sheds some serious light though. I think tiller coupled with nock point is his main concern. That a bow is not tillered such that you need a really high nock point to compensate, thus an inefficient bow.

[Broken Arrow 7]

Me experience with my DAS was initially good but after 1,000 arrows passed through it I noticed unwanted movements appearing when at full draw, 30" on my 62" bow. Un-wanted limb movement along with muffled noises were coming from the limb seats. Apparently the limb pads were compressing during my draw allowing additional movement of the limbs, this was also causing the limb to slide up and down the limb bolts. I dissassembled the limb bolts, set screws, mounting plates, thumb bolt, and limb pads, and this is what I did. I took the phillips head bolt and machined the bolt to approximately a 1/4" dia. directly under the taper about 3/8" long. I made 1/4", 5/16", and 3/8" diamerter spacers 1/2" long. I slid a set, (2 under each limb plate bracket), tightening down the plate with the newly machined philleps head bolt. I changed out the vibration dampening pad for a thinner piece of rubber cut from an old garden hose I had lying around the house. I changed out the thumb bolt with a hex head SS bolt using nylon and SS washers. I tightened down the limbs to the limb plate brackets as tightly as I could. With this change the limbs seated tightly to the limb mounting bracket and with the other pin diameters I'm able to change poundage easily. As a result of this the excessive movements dissapeared along with the muted noises at full draw. My DAS poundage now varies from 52, 55, 58# depending on which spacers I use. Also, I did not re-install the set screws on either side of the limb bolts. As a reult of this the bow is extremily rigid and all I do to fine tune it is adjust the brace hieght and knock point.

Ryan

[Short Draw]

Ryan

Not to make light of your modification, but didn't you just remove all that makes a DAS so versatile?

The whole idea of making the limbs solid to the riser just negates everything David built into the DAS bow.

Your bow is just a Hoyt Dorado on steroids now. Not that there is anything wrong with that.

The machining of the bolts worry me the most.
They are now a lot weaker and at your draw weight could cause a major problem.
I don't understand how you limbs can move once they are at full draw.
The pressure on the end of the limbs should make the bow rock solid.
Interesting way of overcoming a problem just the same.

I have shot thousands of arrows thru my bow and have not replaced anything yet. My Elite and Master still shoot great.

Blue Ridge

You draw length is 31 inches to the front of the riser. That is a lot. You are at the top end of the limbs working range. Are you still at or under 12 pounds over the marked weights on the limb?

Erich

[blue_ridge]

Erich,

My draw length is shorter than 31". More like 29.5. Maybe you read my reply to Free Range about his 29.25" draw and added the 1.75" for AMO?

[Short Draw]

Sorry Blue Ridge.

Message was for Free Range.

I measure my bows at 26 1/4 at the button and add 1 3/4 to get 28 inches.

Erich

[Broken Arrow 7]

Short draw, not that it matters, but all I care about is tuning my DAS so I can hit a fly at 25 yards. The modification to my DAS has created a very stable bow. The tuning now required is minimal. It's short extremily well for 4 years with no side effects. The riser material itself is what contributes to such a stable bow. It's like nothing on the market.

Ryan