Tip Reinforcements for non-B-50 Strings

[Dave Worden]

Is there anything "special" about a bow that can use the newer string materials or is it just that the tips are reinforced better?  If it's just the tip reinforcements, is there any reason that one couldn't a 60's-70's vintage bow, add more/thicker reinforcements and then use the newer string materials.  If it is just tip thickness, how thick does it need to be?  Is there some kind of rule of thumb or a chart that says, for example, minimum thickness is .00x " plus .00y" per 10 lbs of draw wt?  Sure would make things easier if there was such a chart.
Thanks in advance for your help.

[atatarpm]

I have a 1969 Bear Kodiac Hunter and took it to several people to look at. Although the tips are reenforced on this bow  most of them said that the bow would not handle Fast Flight string mat. Bill Foreman of Great Plains Bows told me the the gules of that time were not near as advanced as they are today.
  I also read in some research on my bow that the manufactures of Bear Bows said the older vintage bows such as mine and yours would delamanate if the newer strings were used on them.

[Sal]

Those bows shoot great with dacron, that's what they're made for.  There is no need to alter those beautiful bows for the sake of a few extra fps.

I was shooting my Howatt Hunter (mid 90's, not fastflight safe) and that bow was smoking those arrows.  I don't see how fastflight could improve on its performance.

[Dave Worden]

I'm not looking to change what I shoot.  I'm looking to UNDERSTAND the "don't use Fast Flight on old bows" thing and to know what I have to do on a bow that I make so that it can use FF.

Thanks for the info on the glues.  I hadn't thought of that.  With that being the case, does that mean any bow I make with Smooth-On will be OK with FF?

[Pat B]

You can pad the loops with B-50 and help to soften the stresses on the tips but, like Sal said, why risk damaging your bow for a few fps? I have been using B-50 on all my bows for 25 years and never had a string break and never missed those extra fps.

[jess stuart]

I have used fast flight on everything I have built for several years.  I use care in shaping the nock and use micarta overlays.  Having said all that I don't think I could bring myself to use it on a vintage bow.  The reward doesn't justify the risk in my mind.  Your opinion may differ and that is fine, many use it on older bows with no apparent ill effects.  Long term? Time will tell us the answer to that.

[atatarpm]

I would think also that you would want to use fiberglass over lays on the bow you are planing to build. All the bows I've seen that are FF capable have fiberglass overlays. That will prevent splintering of the wood.
I would like to hear from Jess Stuart though if he uses fiberglass or not?

[Lee Robinson .]

I have added tip overlays to old bows and used dynaflight97 and never had an issue. They were light weight bows though and I did add extra strands of dynaflight97 to the loops of those strings AND I never shot light weight arrows and never had a dry fire. I did it because I won't shoot a bow with dacron (I don't like it), and I could afford losing the bow.

[jess stuart]

atatarpm, I sometimes use fiberglass as part of the overlay usually for the color 1.e. red, white etc.  I have always used micarta in my overlays with ff type strings.  I have heard that fiberglass overlays are good enough, I personally haven't used them so I can't say form experience.

Several years ago I recall seeing several bows with damaged limb tips due to ff.  I am probably over cautious, better safe than sorry.

[Silent Bear]

I personally dont think that fastflight has that much effect on bowtips as people make it out to be, I dont use tip overlays on by bows the only problem I ever had with fastflight was with a 130 pound warbow the string cut through the nocks but with lower poundage bows never had a problem

[Swissbow]

I think if the tips and your string are well built there is no need to take special precautions regarding the tip overlays. If the string is very thin ( like 12 or 14 strands ) then I would pad the loops by interlacing some more strands. I often use phenol but it's more of a cosmetic/optic concern, because it looks nice. If the tips are well shaped with no sharp edges and the string can move freely when the bow is drawn you don't need it.

On an older bow however I wouldn't use FF. Because after all that time you don't know how the bow was treated or how much it was exposed to UV rays or heat. You don't know if maybe the glue joints got a little brittle or not.

----------
Andy

[BoWyo]

I was building bows when ff strings came along.
Some of the major changes that took place after some broken limb tips were, Linen micarta tip overlays, rounding all the faces and shoulders of the string nocks, and probably the most important, not filing a Y in the belly of the string groove.
You might get away shooting ff on an older bow if you use a heavy arrow, but one dry fire and you may have a wall hanger.

[stickmonkey]

If I understand the original question you want to know why you are not supposed to use FF on vintage bows, correct?

B-50 has a great deal of stretch to it as compared to other string material. All strings have some degree of stretch even if you can't decern it.

The vintage limbs needed the shock absorbing power of the B-50 to lessen the strain of the recouping limbs. If a FF string  were used the added stress to the limbs upon return may or in some cases have cause the bows to delaminate due to the left over energy in the bows.

As mention by someone in this post ,shooting a heavier arrow will absorb more energy as it takes move to move it there by reducing the strain on the limbs when they return, however I don't think it would be enough over time to prevent the tip from delaminating

[Dave Worden]

Shane, you got closest to the question, but I'm not trying to find out how to use FF on an old bow.  I'm trying to find out how one KNOWS that a bow can use FF.  I understand that old bows want a stretchier string.  Why don't new bows?  What's different between old and new bows that FF is OK?  Is there a minimum limb tip thickness that is OK for FF?  Do the old bows break because the tips are too thin, because the glue is old, all of the above?  Do the newer bows work because the glue is better?  I've made three fiberglass laminated longbows.  One of Bingham's design, two from two other forms.  Are they OK for FF?  If so, why.  I'm trying UNDERSTAND this issue.  Following a rule of thumb (don't use FF on old bows) is OK if your goal is to not break old bows.  It doesn't even come close to helping determine if my new bows can use it.  As Shane said, the old bows need the shock absorbing characteristic of the B-50.  I hear that.  I know that.  I don't know WHY.  I appreciate the responses so far, but it's frustrating me that I can't find some kind of rule of thumb or some kind of data on what is required for a bow to be safe for FF.  Please guys, keep 'em coming.  I know the knowledge I'm seeking is somewhere on this site.

[Dave Worden]

ttt

[ibehiking]

I think you are asking a great question. I am a fan of knowing the "why" behind some rule/guideline/statement.

If I think about what happens at the end of a shot at the limb tip, I realize that the string stops the motion of the limb tip. If there was no string the tip would go past its resting point and oscillate back and forth like a spring until it came to rest. So what we have is a rapid deceleration of the moving tip. Two key factors seem to be how much energy needs to be stopped, and how abruptly does it stop. The weight of the bow, the weight of the arrow, the draw length of the archer and efficiency of the limb design/string combination determine how much energy is stored at the release of the arrow. The string characteristics seem to determine how abruptly the tip stops. The characteristics of the string that seem to be important is its strength and stretch.

A 16 strand string with each strand having 25# tensile strength has a 400# tensile strength. A 16 strand string with each strand having 50# tensile strength has an 800# tensile strength. What about stretch? Let's say the 25# strands stretch 10% with a 50% load (for discussion sake). The 50# strands stretch 5% with a 50 % load. So the 16 strand 25# string will stretch 10% when subjected to a 200# load. The 16 strand 50# string will stretch 5% with a 400# load.

Using a 50# bow, for illustration purposes, let's say that all 50# is available when the tip needs to stop. The 16 strand 25# string will stretch 2.5% (50#/200# x 10%). The 16 strand 50# string will stretch 0.6% (50#/400# x 5%). This says with full strength FF strings the tip is stopped in 1/4 of the distance that the B-50 string stops the tip. Talk about slamming on the brakes!

Another aspect to consider is the area over which the stopping force is applied. If the 16 strands of FF are smaller diameter than 16 strands of B-50 then the force exerted at the point of contact with the string is also increased. Let's pretend the FF string is 1/2 the diameter of the B-50 string.

Now you have 4 times the force applied over an area 1/2 the size. This might indicate that at a minimum you need 8 times the resistance to the force. This could be in 8 times the thickness of the tip material, or 8 times stronger glue, or some combination of the two.

The actual thickness could be better estimated by knowing the real values for strength, stretch, diameter and force to be stopped.

For the same bow, same arrow and same archer the ratios hold true, so all that is really needed is the strength, stretch and diameter of the strings.

This seems to be consistent with some of the thinking on skinny FF strings with padded loops. An 8 strand 50# string now has a 400# tensile strenght with a 5% stretch at a 200# load. So the 50# bow will stretch 1.25% (50/200 x 5%). The paddled loops make the diameter at the contact area the same. Now the tip stops in 1/2 the distance (brakes aren't slammed quite as hard) and the force is applied over the same area.


The reduced stretch of the FF string probably adds to the amount of force to be stopped, unless it imparts that force to the arrow in the form of greater speed.


Just some of the thinking that goes on in my head about this subject.

[Sixby]

Ok. The bow has to be built with modern glass and smooth on or equivilant. The overlays have to be made out of phenolic or equivilant and the grooves have to be cut in a teardrop shape. I pretty much ditto what Bruce Said. I know for a fact that glass overlays will split and ruin the bow. /Been there, Done that. Antler , horn and Micarta work. I use at least one thin layer of phenolic as the bottom overlay. Over that I can use Elk antler, Phenolic, Deer antler., Bison, Antelope, Sheep horn, and many exotic woods such as cocabola. The shape of the nock is as important as the materials. However it is less important on a thin , wide tip like a recurve than it is on a deeper stack on a longbow or D and r. God Bless you all and Merry Christmas, Steve.

[Dave Worden]

Now we're getting somewhere!  Thanks guys.  Steve, are you saying that making a longbow tip (which we'll assume is fairly narrow) thicker (say adding a quarter inch of additional WOOD) from belly to back is fairly ineffective when dealing with FF?  I'd be better off with a thin piece of phenolic than a thick piece of wood?  Ignoring of course, the loss in efficiency generated by thicker, heavier limb tips.  Also I understand what Bruce was saying about rounding all the edges and not grooving the belly of a recurve, but I'm a little unclear about "teardrop shaped".  Are you saying the widest part of the nock would be at the center of the bow (back to belly) and the "end" of the nock would be tapered both on the belly and the back?  I suspect we're also saying that filing any kind of groove on the back of the bow to guide the string would be a no-no?

[ChristopherO]

Dave, from what I've learned it is not so much how thick the limb tip is or how much wood is in the tip but the material used to protect the tip from the cutting ability of FF strings.  This is why Sixby said no to fiberglass overlays and yes to micarta, horn or antler.  Those mediums won't splinter or allow the cutting as fiberglass and wood overlays will over time.
I confess I am not sure what exactly they meant on the tear drop shape but I know this and incorporate it into my builds:  On the tip shape it is on the sides where the string groove is that matters.  As the string is pulled to shoot an arrow the string at the nocks will move, rubbing the groove and shoulder of the groove.  It is best to open up the belly side of the string groove to allow the string room to move without binding along with dimenishing the effect of the pivot point.  
Conduct a search of Apex Predator's build alongs and Tip threads to see some of the mose excellent shaped and finished tips for a visual example.

I just had to replace the wood overlays due to filing too deep in to the tip.  This time I glued antler on the tips and am confident the man who will be using this bow can use FF strings if he so wants to.

[Pat B]

This is an osage selfbow that Dano(Dan Gren) sent me a few years ago. No tip treatment and Dano always used FF type string material...

top limb...
 

bottom limb...
 

I love the way Dano ends his snake skins; cutting around the scales!