«^. I ^ 
 
 TECHNICAL NOTE number 226 
 
 UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE 
 
 FOREST PRODUCTS LABORATORY 
 
 madison 5. Wisconsin revised December 1952 
 
 GLUES FOR WOOD IN ARCHERY USES 
 
 Glues are used (l)to splice billets for bowstaves, (2) to splice "footings" 
 to arrow shafts, (3) to attach feathers to shafts, (4) to attach facings 
 and backings of a variety of materials to bows, (5) to lay leather or other 
 bindings on bow handles, (6) to laminate bows from layers of thin-JKO_od 
 or wood with other materials, and (7) to attach nockff and points to arrow 
 shafts. 
 
 Properties of Glues— 
 
 The woodworking glues that are available to amateur archers may be 
 grouped into several types based on durability of the resultant joint, 
 conditions required in gluing, and cost. The following generalizations 
 are given for the guidance of archers who do not wish to make a special 
 study of the literature on gluing. 
 
 (1) No glue will produce joints of maximum strength unless the joint fits 
 closely and unless the glue is prepared and used correctly. Directions 
 for use are furnished by the manufacturer or supplier. Conditions that 
 give best results in gluing with one type of glue may not give best re- 
 sults, or even fair results, with another type of glue. 
 
 (2) Generally high-grade glues of all principal types of woodworking 
 glues will give equally high initial, dry joint strength on commonly used 
 species when used under the most favorable conditions for that type of 
 glue. 
 
 (3) Woodworking glues vary widely in their water resistance. In addi- 
 tion, the water resistance of the joint will vary according to the quality 
 pf the gluing and the effectiveness of the protective coatings. 
 
 —The characteristics of various glues are described in greater detail 
 in Technical Note Nos. 257, 258. 
 
(4) Animal glues are characterized by high dry strength, low water re- 
 sistance, and quick gelling. These glues are available in a series of 
 grades, the higher grades gelling more quickly than the lower grades 
 under similar conditions. Formulas have been developed to improve 
 the moisture resistance of animal glue, but their use is not recommended 
 for amateurs. Hot animal glues, prepared by the user and used as soon 
 as possible after melting, give best results. Control of wood and glue 
 temperatures and of assembly time, however, are critical with hot ani- 
 mal glue. Liquid animal glues appear to vary considerably from sample 
 to sample. 
 
 (5) There are a number of kinds and grades of casein glue. For gluing 
 wood used in archery, a water-resistant or "joint" grade of casein glue 
 should be used. Casein glues are used cold. Because of their high 
 alkalinity, these glues tend to stain woods containing extractives. 
 
 (6) Urea-resin glues (one type of synthetic-resin glue) set at 70° F. or 
 above. They are generally available in local hardware and building sup- 
 ply stores as powders to be mixed with water before use. These glues 
 are convenient to use, develop a high degree of water resistance, are 
 colorless, and do not stain the wood. Their rate of strength develop- 
 ment can be increased by heating the joint. The glue mix will set hard 
 and insoluble in water within a few hours, so that it cannot be cleaned 
 away or used after this hardening. The sensitivity of urea resins to 
 long exposure at elevated temperatures should not be a significant limita- 
 tion for archery applications. Special gap-filling formulations of urea 
 resins are preferred by some archers. 
 
 (7) Resorcinol-resin glues are the most recent type of woodworking glue. 
 These glues cure or harden at 70° F. or above, generally somewhat 
 more slowly than urea resins. They are available in liquid form to which 
 a separate powdered hardener is added before use. Resorcinol-resin 
 glues produce a dark red or brown glue line, set hard within a few hours, 
 and are the most durable of all room -temperature -setting woodworking 
 glues. Generally excellent, durable bonds should be possible when they 
 are properly used. At least one brand of resorcinol glue is available 
 in retail shops, but the cost is higher than that of other glues. 
 
 (8) Various phenol-, melamine-, urea-, and other resin glues are avail- 
 able that cure at 240° F. or higher, but these are not generally feasible 
 for the amateur archer. 
 
 (9) Polyvinyl-resin emulsion glues are supplied as liquids ready to use 
 at room temperature. Since they lack the water resistance of casein 
 
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glues and other resin glues and are subject to some slippage and flow 
 in joints under load, they are not recommended for most wood-to-wood 
 joints in archery equipment. They may be very useful, however, for 
 gluing leather, plastics, and other flexible materials to wood for trim 
 where high stresses are not exerted on the joint and where their quick 
 setting and colorless glue lines are distinct advantages. 
 
 (10) Nitrocellulose -.base cements (pyroxylin) are particularly useful for 
 attaching feathers to arrow shafts, plastic nocks or points to arrow 
 shafts, and leather grips or handles to bows. Nonaqueous cements of 
 the hot-melt type, such as DeKhotinsky cements, are often preferred 
 for attaching metal points to shafts. 
 
 (11) A number of new adhesive -bonding procedures have been developed 
 in recent years for bonding metals and plastics to wood in conjunction 
 with the manufacture of aircraft and other specialized equipment, but 
 many of these processes are still in the experimental stage and cannot 
 be easily adopted by the typical archery enthusiast at this time. They 
 will offer, however, to the archer with a technical interest a variety of 
 opportunities to experiment with interesting new composite materials, z. 
 Interest in such materials has increased because of the increasing short- 
 age of the most desired species and quality of wood for bows. 
 
 Special Use Requirements 
 
 (1) For fishtail splices in staves and for footing joints in arrows, high 
 strength and water resistance are important. A good fit and a larger 
 bearing surface affect dry strength more than the type of glue. In staves 
 the bearing surface may be enlarged by keeping plenty of thickness under 
 the handle. In shafts a sufficient bearing surface is assured if the length 
 of the splice is at least 15 times the diameter. 
 
 (2) The choice of glue for attaching feathers to shafts depends on the 
 degree of water resistance desired and on the rate of gelling of the glue 
 for the particular mechanical method used for feather attachment. Ani- 
 mal glues have been used, but nitrocellulose -base cements (pyroxylin) 
 now seem to be preferred and appear to have acceptable moisture resist- 
 ance. Glues of the woodworking types, known to be more moisture re- 
 sistant, are not generally convenient to use for attaching feather s because 
 of their slow hardening under normal conditions. 
 
 —The bonding of wood to metal is discussed in Forest Products Labora - 
 tory Report No. R1768. 
 
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(3) Glues for attaching bow backings and facings must produce bonds that 
 have high strength and high moisture and water resistance and that are 
 able to bend with the bow without failure. Glue films applied to the wood 
 for laying sinew, silk, or high-tenacity rayon fibers as backings and 
 facings must bend without cracking. Animal and certain resinglues have 
 been used for these purposes. 
 
 Gluing Properties of Archery Woods 
 
 Since a good glue joint is usually considered to be one that is stronger 
 than the wood being bonded, the stronger high-density species require 
 stronger bonds than the low-density woods. Therefore, more careful 
 control of the gluing conditions is required to produce satisfactory joints 
 in hickory than in spruce or pine. Oily woods, such as yew, osage or- 
 ange, or lemonwood, that are commonly favored for bow staves may be 
 more difficult to glue than woods of the same density but without oils, 
 resins, or extractives. Oily woods may glue better when freshly ma- 
 chined than later. Sponging oily wood surfaces with a 10 percent solu- 
 tion of caustic soda, wiping off the excess, and drying before gluing often 
 improves gluability with animal and casein glues. Since residual alkali 
 is likely to interfere with the catalyst systems of many urea- andresor- 
 cinol-resin glues, this alkali surface treatment should not be used with 
 these resin glues. Gluability with these resin glues may, however, be 
 improved by the use of somewhat elevated curing temperatures -- 100° 
 F. or so -- during the pressure period. Care must be taken to avoid 
 excessive drying of the wood during such curing of the glue. 
 
 UN1 VERSITY OF -FLOmDA 
 
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