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

Limb Holder

I've settled on a standard limb holder that is two inches wide on the outside and can accommodate limbs that are up to 1.75" wide.  The length of supported limb end will be 4.5".  This means that I can take advantage of many of the Alevekiu limbs that I already have but it will also work with my own limb designs.  The design is simple and requires little more than a drill press and cut-off saw.  I am using 2"x2"x1/8" square steel tube.  I also made another set from 2"x2"x3/16" square aluminum tube, but it only accepts limbs up to 1-5/8" wide. 

Limb Holders, 1-5/8" wide with my limb top, Alevekiu's 1.75" wide at bottom.

I use a single screw to clamp the limb in place so it works with multiple thickness limb ends.  I feel this works pretty well but also feel it may be an unnecessary complication.  The more I think about it, the more I realize that the limb doesn't need to be clamped down.  It will be held in place by string tension alone and perhaps all I need is to add blocks to fill the gap between the top of the limb and the limb holder.  I will keep it as is for now and see how it holds up when I put it through several full draw trials later this year.