Regroup

Following the 2013 US Nationals, I decided one of my first tasks is to repair the bow limbs that damaged with my final shot (set #28). I really liked how smoothly this set drew back and crisp it felt on the shot.  They were not of much use in the condition that they were in so I figured I had nothing to lose.

I started by carefully measuring the dimensions of the good limb, noting the thickness, width, and side profile at one inch intervals. I also measured the thickness of the back and belly glass lamination.  I fed these dimensions into my "Supertiller" bow modelling program to create a virtual version of the bow.  The damage to the limb was too severe to simply glue back together.  If the bow was to shoot again, the width profile of the outer limb will need narrowing.  I was able to use the virtual bow to develop a new width profile for the bow limbs that would have minimal affect on the tiller or way the limbs bent when drawn back and released.  I printed out the pattern and proceeded to reshape both limbs. 

I used several thin hickory laminations with a layer of glass mat between each to form the new tip overlays. I added additional overlay laminates to the sides of the limb tips with the hope that this would help counteract the high shear forces when the string slams home. 

I carefully shaped the new overlays and string grooves and smoothed and patiently blended any sharp corners or abrupt transitions.  It took a lot of patience but I was happy with the results. They looked like new again, and it was time to string them up to check the tiller and make sure it can withstand being drawn back. 

2013 US Flight Nationals

I realize I have missed sending an account of what happened at our Flight Nationals, so here it is:

US Nationals, August 31, 2013
Two of us were equipped to shoot foot bows using Alavekiu's bow limbs at the Bonneville Salt flats 2013 Flight Nationals.  James Sanchez had his beautifully made Drake-inspired foot-bow, and I had my contraption. For the first day's rounds, we disconnected the mechanical release and crossbow-like barrels to make the bows legal to shoot in the regular footbow division.  Unfortunately, nerves, and technical issues kept our distances disappointingly short. It is not as easy as it may look.

James Sanchez, Foot Bow 2013

The second day of competition had a rough start with a mishap on the shooting line. The well-being of our friends are much more important than seeing how far we can shoot arrows.  The nearest hospital is two hours away and James packed up to look after our friend.

The event continued. There was one last chance to shoot a single round of six arrows in the afternoon rounds.  I decided I should at least give it a try.  At the shooting line, I was extremely nervous and drew the first arrow a few inches short of full draw (about 13" draw on a 14" arrow) just to see if everything was working as expected. The string shattered the little Mylar arrow rest, but it fired nice and clean, better than my best expectations. 

Last shot at 2013 Nationals

I started to feel a little more confident.  With five arrows left, I figured there was little to lose.  it was time to push it to the limits to find out what the bow could do.  I replaced the broken arrow rest and took a little more care to line up the arrow and bow string.  For shot two, I adjusted the trigger to release at a 16" draw, and pulled back hard. But the bow unexpectedly released at about 12-13" draw again.  The loop on the string that the release trigger hooks into suddenly gave way, releasing before it hit full draw.






I fixed the release loop issue, reset the trigger for about a 15-1/2" draw and pulled hard again. This time everything worked perfect and the bow shot felt absolutely clean. I felt a rush of adrenaline as I knew it was going to be a long time before that arrow would find the ground. I cranked back the trigger for a 16" draw with arrow #4 and pulled hard again. I am certain arrow #4 left the bow just as cleanly as arrow #3 but the bow let out a nasty sound and the string came to rest at an awkward angle on the limbs. The high string forces of slamming the arrow down range blew the nocks off the ends of the bow limb, tore right down the right limb, and split the limb into a three pronged fork.





There were two arrows remaining to shoot, but there was no time to re-limb and re-string the bow.  The remainder of the day was dedicated to searching where those four arrows ended up.

GPS Trail Showing Arrow Search Pattern

My daughters and I hopped on the ATV and headed downrange perpendicular to the shooting line. Slow at first, then faster. Scanning at 400, 500, 600 yards. Sometimes, depending on light conditions, it is relatively easy to spot the little black arrows against the white salt from as far as 150 yards.  Sometimes it is almost impossible to see it 2 yards away. We continued on: 7, 8, 900 yards and no sign. 1000 yards, 1100, then I felt a rush of excitement as I spotted my first arrow. I marked it in my GPS then continued past 1200 yards where I spotted a second arrow and marked it in my GPS.  We slowly continued outward past 1800 yards with no sign of the other two arrows. For the next three hours, we searched the area, working our way back to the shooting line with no sign. The sun was setting and we were out of time.  An official measurement was taken of the longest found arrow at 1217 yards.  It was short of a mile and not a new record but I was ecstatic with the results!

Verification of the serial number on the longest arrow measured revealed it was from my first shot. The second, closer-in arrow, was my second shot.  It was my last two shots taken at full draw that were not found. I am certain that the last two arrows must be either farther out or they buried themselves below ground.  Regardless, these results were very encouraging that these 45 year old bow limbs are capable of mile+ shots after all. James, the ghost of George, and I will just need to return to prove it!

The next day, the broadhead events were held and we returned to the shooting area to continue the search but quickly conceded.  At the conclusion of the broadhead event the awards handed out, the ATV was packed up and competitors began leaving for home.  It was time we left too.  Overall, it was a great success.  Our girls broke three records in their classes and we had a fantastic time together as a family.  Steve Gardner broke long held records in the 50# primitive flight and broadhead classes.  Amy Haile smashed her prior 50# record.  I came away with a personal best, GPS map of the search area, and motivation to come back in 2014 to do it again! 

By the way, our injured friend set a new record of her own immediately before her incident. She is doing well and plans to shoot again this year.

The Alavekiu “1-mile” Series Bow Limbs

George Alavekiu built a final series of at least 90 foot bow limb sets in his race to exceed Harry Drake’s foot bow and crossbow record accomplishments. In addition, there are numerous prototype pairs and 1-piece configurations.

There are numerous surviving limb sets of the "1-mile" design, plus a couple dozen prototypes and test limbs. Of these, 60 pairs are in good enough condition to be shot today. In fact, a majority of these look as if they just came off the form this year. Why were so few ever used?  I find only about twenty of the total show evidence of being heavily shot. About half of these are damaged beyond repair.  It leads me to wonder if George continued to build these after 1970 when Harry Drake officially achieved the mile distance?

I gave a quick look through the arrows George had built. There are at least 200 complete arrows plus several in various stages of completion (I'll go into more detail on these in a later post). Some of the arrows have George’s name, arrow number, and date on them in the customary format used at our US National Competition. Some of these were dated September of 1989.  This was nearly 20 years after Harry Drake established his unlimited foot bow record. Did George compete again?  Or, was he planning to?  I was told that he continued to shoot on his own. What else might he have achieved? Maybe some of these bow limbs are not as old as I had originally thought?  It is a bit of a mystery.

Anyone out there able to fill in the details?

Alavekiu’s Arrows

George Alavekiu made some beautiful flight arrows. These “one mile” arrow designs look ridiculously tiny considering the power of the bow used to propel them. The heaviest limb sets store as much as 280 ft-lb of energy over 18" of draw. If I assume 50% of that energy makes it to the arrow, and given a typical arrow mass of 125 grains, then the bow would yield speeds in excess of 700 fps.   Given the same assumptions, the lightest limb sets would deliver more than 550 fps to a 125 grain arrow.  I have no idea what efficiency to expect yet, but these limbs should shoot like never before with the latest advances in string material.  

A little more on the Alavekiu Bow Limbs

Here’s a little summary of my survey of the Alavekiu "1-mile" Foot Bow limbs. They are all very well made and each one a little unique from the rest. George was obviously looking for the magic combination of design elements and used a very exhaustive trial and error approach. Based on stories passed down to me, Harry Drake seemed to take on a similar trial and error approach. 

George’s 1-mile series were intended to be drawn 18”-20”. String lengths varied between 44” and 46”. The limb length ranged from 18.5” to 22” with the working portion of the limb taking up 11” to 13” of the total. There were two primary widths produced, 1-3/4” wide and 2” wide. The side profiles were produced on at least three forms. Type one is labeled “Turkish” which is a very wide open reflexed recurve. Type two has relatively shallow reflex and then sharply recurved at the end. Type three has a more open and less abrupt recurve shape with no reflex. 

 

There are draw weight numbers marked on some of the limb sets taken at 1” of draw and 2” of draw. The heaviest set lists a draw weight of 67 pounds at only two inches of draw. Such a bow should exceed 400lb drawn 18”, and I estimate 270-280 foot pounds of stored energy!

Construction is pretty conventional. All designs fall the static recurve category, where the outer third of the limb does not bend. The limb core is made from several hard maple laminations with additional tapered pieces at the fades and reverse tapered wedges to form the rigid recurved tips. A majority of the bending takes place over a six inch section of the limb. This creates a hinge-like tiller which has proven to be most effective at reducing efficiency losses from limb vibration and deflection with high arrow speeds. The Turks used it. Harry Drake used it. It is pretty much universal among successful flight bow designs. The limb is backed and faced with either clear or black uni-directional glass laminations and are around 0.05” thick. Plain E-glass is used on almost all of the limbs, but small portions were made with S-glass. In many cases, there is an additional thin layer of woven bi-directional glass cloth under most of the outer glass laminations which help prevent longitudinal splits. Many of the limbs which were shot heavily show small uni-directional splits in the outer lamination even with the use of the reinforcing underlayment.

The broken limbs I have most often failed by delaminating at the fades on the belly side or elsewhere between the maple laminations. I feel that the limb would be more robust if the curvature of the belly side fade was not so severe. Many limbs also show damage where the string cut through the nocks. I will use reinforced loops to prevent this. One set had severe compression failures in the glass at the fades. It formed a set of chrysalis that I normally only see in overstressed all-wood bows.

The limb tips are wider than I would consider with my designs. A limb set with 2” wide working limb section typically tapers down to .88” wide at the tips. I assume that this area is a common point of failure as the string pulls taught at the end of the shot and stops the limbs. I am not convinced that it has to be this way. A lighter and narrower limb tip should be quicker and transfer less force to the string, but I am a relative new comer and may change my mind after building a few more limb sets of my own. The tips are often reinforced with glass cloth and glass wedges to prevent splitting. George grooved the belly side of the limb where the string and string loop rests against the outer recurved portion of the limb when at brace.

All Together

I'm very happy with how it all turned out but need to hurry things along in order to catch up where I am with it today.  In addition to being able to sweep the limb angle through a very wide range, I can move the limbs in and out and adjust up and down to fine tune tiller and string tracking issues.  The possibilities are endless.  I imagine I could find myself endlessly tinkering with these adjustments too so I don't know for sure if it is a good thing yet.  Hahaha!

Foot Bow Limb Riser Assembly

The adjustable limb angle allows me to easily and gently string even a very high draw weight set of limbs with little more than a ratchet and socket.  I love it!  No bow presses necessary.

Shown Assembled with limbs back and loose string

Rear View Showing Arrow Pass-Thru and Limb Angle Adjustment Screws

Shown rotating limbs into position and increasing string pre-load

Braced and Ready to shoot!

Frame

I have very limited machining tools, so the design of the frame for the bow had to be simple enough to be made with little more than a drill press and band saw. The top and bottom plates are 1/4" thick aluminum plate.  I simply drew up the outline and hole locations, printed it out, and pasted it to the plate.  After a little careful drilling and some tap-and-die operations, it was pretty much complete.

Top and bottom plates

The limb pivots are made from thick wall steel tube that is drilled and tapped for a 5/16" cap screw.  This allows the limbs to pivot and provides a very large range of limb angles.  It will probably make more sense when I show how it all goes together next.

All parts with arrow pass-through & limb holders