by Eric Meier
First off, a few brief disclaimers:
- Aside from a few archery classes I took back in in college, I am neither an archer nor a bowyer.
- The ideas presented here would apply only to simple or self bows made from a single piece of wood, and may or may not be directly applicable to other types of bows such as composite or laminated bows.
With that being said, I have access to consolidated data on a lot of different kinds of wood. While there are almost endless ways to measure wood strength (which I discuss in more detail in my article World’s Strongest Woods), when you broaden the scope out to all woods worldwide, there are three tests that seem to come up most often. Listed in order of their commonness, they are: modulus of elasticity (MOE), modulus of rupture (MOR), and crushing strength. Of the three, we will be looking more closely at the first two tests.
Cracking the Code
Archery bows present a somewhat unique challenge in finding the right requirements for the best wood. In the simplest and crudest terms possible, the wood should be able to bend, but not break.
“As a rule of thumb, the best bow materials are those that combine a high specific bending strength with a relatively low specific modulus (Hickman et al. 1947). In general, a good bow is one to which a high force can be applied under a large elastic deformation, which guarantees that a large amount of elastic energy stored during the draw is transferred effectively into kinetic energy of the arrow when the bowstring is released.”Bjurhager, I., Gamstedt, E., Keunecke, D., Niemz, P. & Berglund, L. (2013). Mechanical performance of yew (Taxus baccata L.) from a longbow perspective. Holzforschung, 67(7), 763.
To summarize the above recommendations, the authors call for a wood with “high specific bending strength” (MOR) along with a “relatively low specific modulus” (MOE).
Dealing in the simplest terms:
- The modulus of rupture (MOR) measures how easily the wood will break—the higher the number, the harder it is to break or rupture.
- The modulus of elasticity (MOE) measures how easily a wood will bend—the higher the number, the more stubborn and stiff it will be.
So in terms of looking at the raw mechanical data of woods, the best bow woods tend to be those that have a low MOE and a high MOR. Stated another way, the best bow woods tend to be those that will bend easily, and not break. This is perhaps an oversimplification, but it is at least a good starting point in evaluating new woods for suitability to use as an archery bow.
Creating a “Bow Index”
Instead of displaying the absolute values of each wood species, I thought it would be an interesting pursuit to come up with a ratio that compares the two pertinent values, MOR and MOE. This would in effect emphasize those woods with the special properties of having a disproportionately high MOR and/or a low MOE.
Given the rationale and requirements, an equation can be formed to roughly assess a wood’s suitability for bow use:
(MOR/MOE) * 1000.
(The added factor of 1000 is simply to bring the number to a more manageable size and avoid dealing with tiny .00XX decimal values.)
For lack of a better term, this ratio will simply be referred to as the wood’s “bow index.” Results are listed in the table below, sorted from highest to lowest bow index.
Bow Index Listing
|Bow Index||Common Name||Scientific Name|
|13.06||Iron birch||Betula schmidtii|
|12.61||Pear Hawthorn||Crataegus calpodendron|
|11.90||African Blackwood||Dalbergia melanoxylon|
|11.61||Lebombo ironwood||Androstachys johnsonii|
|11.27||Pau Ferro||Machaerium spp.|
|11.26||Pacific Yew||Taxus brevifolia|
|11.15||Tropical black sage||Cordia curassavica|
|11.05||Osage orange||Maclura pomifera|
|10.98||River Sheoak||Casuarina cunninghamiana|
|10.85||Norway maple||Acer platanoides|
|10.57||Turkey Oak||Quercus cerris|
|10.52||Pau Santo||Zollernia paraensis|
|10.50||Bur Oak||Quercus macrocarpa|
|10.49||River Red Gum||Eucalyptus camaldulensis|
|10.47||Western sheoak||Allocasuarina fraseriana|
|10.44||Siamese Rosewood||Dalbergia cochinchinensis|
|10.42||Field maple||Acer campestre|
|10.40||Monterey Cypress||Cupressus macrocarpa|
|10.37||Algarrobo Blanco||Prosopis alba|
|10.31||English Walnut||Juglans regia|
|10.31||Alligator Juniper||Juniperus deppeana|
|10.18||Downy Birch||Betula pubescens|
|10.08||Crab apple||Malus sylvestris|
|10.04||Black Mesquite||Prosopis nigra|
|10.00||Eastern Red Cedar||Juniperus virginiana|
|10.00||Rough-barked apple||Angophora floribunda|
|9.98||Ceylon Satinwood||Chloroxylon swietenia|
|9.94||East Indian Rosewood||Dalbergia latifolia|
|9.93||Rhodesian Teak||Baikiaea plurijuga|
|9.90||African Padauk||Pterocarpus soyauxii|
|9.89||Sycamore maple||Acer pseudoplatanus|
|9.86||Peruvian Walnut||Juglans neotropica|
|9.86||Blue Ash||Fraxinus quadrangulata|
|9.82||Burma Padauk||Pterocarpus macrocarpus|
|9.80||Sweet Cherry||Prunus avium|
|9.76||Nutmeg Hickory||Carya myristiciformis|
|9.74||Siberian Elm||Ulmus pumila|
|9.72||Pau Rosa||Bobgunnia fistuloides|
|9.72||Pau Rosa||Bobgunnia madagascarensis|
|9.69||Brazilian Rosewood||Dalbergia nigra|
|9.63||American Hornbeam||Carpinus caroliniana|
|9.61||Rock Elm||Ulmus thomasii|
|9.58||Shellbark Hickory||Carya laciniosa|
|9.56||Chakte Kok||Simira salvadorensis|
|9.55||Bitternut Hickory||Carya cordiformis|
|9.53||European Yew||Taxus baccata|
|9.52||Prosopis juliflora||Prosopis juliflora|
|9.46||Black Locust||Robinia pseudoacacia|
|9.46||Nigerian pearwood||Guarea cedrata|
|9.44||Horse chestnut||Aesculus hippocastanum|
|9.38||Southern Silky Oak||Grevillea robusta|
|9.37||African Mesquite||Prosopis africana|
|9.36||Oregon White Oak||Quercus garryana|
|9.36||Gaboon Ebony||Diospyros crassiflora|
|9.35||Shagbark Hickory||Carya ovata|
|9.34||Oregon Ash||Fraxinus latifolia|
|9.29||Live Oak||Quercus virginiana|
|9.28||Sessile Oak||Quercus petraea|
|9.25||Yellow Gum||Eucalyptus leucoxylon|
|9.25||Grey myrtle||Backhousia myrtifolia|
|9.21||Texas Ebony||Ebenopsis ebano|
|9.14||African Walnut||Lovoa trichilioides|
|9.14||Japanese Larch||Larix kaempferi|
|9.14||Ceylon Ebony||Diospyros ebenum|
|9.13||English Elm||Ulmus procera|
|9.13||Dutch Elm||Ulmus x hollandica|
|9.13||Pink Ivory||Berchemia zeyheri|
|9.12||European Hornbeam||Carpinus betulus|
|9.12||Cedar Elm||Ulmus crassifolia|
|9.12||English Oak||Quercus robur|
|9.10||Scarlet Oak||Quercus coccinea|
|9.06||Amazon Rosewood||Dalbergia spruceana|
|9.06||Santos Mahogany||Myroxylon balsamum|
|9.06||Cascara Buckthorn||Rhamnus purshiana|
|9.06||Macassar Ebony||Diospyros celebica|
|9.06||Argentine Osage Orange||Maclura tinctoria|
|9.05||Tamo Ash||Fraxinus mandshurica|
|9.03||Yucatan Rosewood||Dalbergia tucurensis|
|9.02||Chico Zapote||Manilkara zapota|
|9.02||Honey Locust||Gleditsia triacanthos|
|8.99||Canadian Serviceberry||Amelanchier canadensis|
|8.97||Winged Elm||Ulmus alata|
|8.89||Pignut Hickory||Carya glabra|
|8.88||Afzelia xylay||Afzelia xylocarpa|
|8.87||Overcup Oak||Quercus lyrata|
|8.85||Okoume / Gaboon||Aucoumea klaineana|
|8.84||Black Poplar||Populus nigra|
|8.82||Black Palm||Borassus flabellifer|
|8.82||Wych Elm||Ulmus glabra|
|8.81||Water Hickory||Carya aquatica|
|8.81||American Elm||Ulmus americana|
|8.80||Queensland Walnut||Endiandra palmerstonii|
|8.79||California Black Oak||Quercus kelloggii|
|8.76||Mexican Cypress||Cupressus lusitanica|
|8.74||East African Olive||Olea capensis|
|8.74||Post Oak||Quercus stellata|
|8.74||Pumpkin Ash||Fraxinus profunda|
|8.72||Red Elm||Ulmus rubra|
|8.72||Endra endra||Humbertia madagascariensis|
|8.71||Yellow Box||Eucalyptus melliodora|
|8.69||Black Walnut||Juglans nigra|
|8.66||American Beech||Fagus grandifolia|
|8.65||Mockernut Hickory||Carya tomentosa|
|8.65||Mountain Hemlock||Tsuga mertensiana|
|8.64||Red Mulberry||Morus rubra|
|8.63||Hard maple||Acer saccharum|
|8.63||Giant Chinkapin||Chrysolepis chrysophylla|
|8.62||White Ash||Fraxinus americana|
|8.62||White Meranti||Shorea hypochra|
|8.58||African Mahogany||Khaya senegalensis|
|8.58||Swamp White Oak||Quercus bicolor|
|8.57||Staghorn Sumac||Rhus typhina|
|8.55||Maritime Pine||Pinus pinaster|
|8.55||Virginia Pine||Pinus virginiana|
|8.55||White Cypress Pine||Callitris columellaris|
|8.54||Swamp Mahogany||Eucalyptus robusta|
|8.52||Gray Birch||Betula populifolia|
|8.49||Green Ash||Fraxinus pennsylvanica|
|8.45||Brown Ebony||Libidibia paraguariensis|
|8.44||Mediterranean Cypress||Cupressus sempervirens|
|8.43||Grey Box||Eucalyptus moluccana|
|8.43||Suriname Ironwood||Bocoa prouacensis|
|8.42||Andaman Padauk||Pterocarpus dalbergioides|
|8.42||White Oak||Quercus alba|
|8.41||European Ash||Fraxinus excelsior|
|8.40||Amourette (snakewood sapwood)||Brosimum guianense|
|8.39||London plane FS||Platanus x acerifolia|
|8.39||London plane QS||Platanus x acerifolia|
|8.36||Chestnut Oak||Quercus prinus|
|8.36||Monkey pot||Lecythis zabucajo|
|8.34||Black wattle||Acacia mearnsii|
|8.34||Panga Panga||Millettia stuhlmannii|
|8.32||Cape Holly||Ilex mitis|
|8.32||Monkey Puzzle||Araucaria araucana|
|8.31||Black Oak||Quercus velutina|
|8.31||European alder||Alnus glutinosa|
|8.30||Sweet Chestnut||Castanea sativa|
|8.29||Eastern Hophornbeam||Ostrya virginiana|
|8.29||River Birch||Betula nigra|
|8.28||Shumard Oak||Quercus shumardii|
|8.27||Scots Pine (R)||Pinus sylvestris|
|8.27||Huon Pine||Lagarostrobos franklinii|
|8.26||Gum Arabic||Vachellia nilotica|
|8.26||Yellow Birch||Betula alleghaniensis|
|8.26||Black Cherry||Prunus serotina|
|8.25||Horsetail Casuarina||Casuarina equisetifolia|
|8.25||Smooth-barked apple||Angophora costata|
|8.24||Willow Oak||Quercus phellos|
|8.23||Slash Pine||Pinus elliottii|
|8.23||Sand Pine||Pinus clausa|
|8.21||Black maple||Acer nigrum|
|8.21||Queensland kauri||Agathis robusta|
|8.19||Black siris||Albizia odoratissima|
|8.19||Silver Birch||Betula pendula|
|8.17||Red maple||Acer rubrum|
|8.17||Water Oak||Quercus nigra|
|8.17||Red Oak||Quercus rubra|
|8.16||Crack Willow||Salix fragilis|
|8.14||Indian Laurel||Terminalia elliptica|
|8.14||Southern Red Oak||Quercus falcata|
|8.13||Grey Ironbark||Eucalyptus paniculata|
|8.13||Northern White Cedar||Thuja occidentalis|
|8.12||Parana Pine||Araucaria angustifolia|
|8.12||Cedar of Lebanon||Cedrus libani|
|8.09||Pin Oak||Quercus palustris|
|8.08||Mora (glued)||Mora excelsa|
|8.07||Lemon-Scented Gum||Corymbia citriodora|
|8.03||Southern Redcedar||Juniperus silicicola|
|8.03||Honduran Mahogany||Swietenia macrophylla|
|8.02||Angelim vermelho||Dinizia excelsa|
|8.00||Black Tupelo||Nyssa sylvatica|
|8.00||Southern Magnolia||Magnolia grandiflora|
|7.99||European silver fir||Abies alba|
|7.99||Laurel Oak||Quercus laurifolia|
|7.99||Cuban Mahogany||Swietenia mahogani|
|7.97||Blackheart Sassafras||Atherosperma moschatum|
|7.97||African Juniper||Juniperus procera|
|7.94||Cherrybark Oak||Quercus pagoda|
|7.88||Black Ash||Fraxinus nigra|
|7.87||Radiata Pine||Pinus radiata|
|7.86||Patula Pine||Pinus patula|
|7.85||Swamp Chestnut Oak||Quercus michauxii|
|7.84||Red Palm||Cocos nucifera|
|7.82||Yellow Cedar||Cupressus nootkatensis|
|7.81||Peroba Rosa||Aspidosperma polyneuron|
|7.81||Silver maple||Acer saccharinum|
|7.80||Tiete Rosewood||Guibourtia hymenaeifolia|
|7.79||Sweet Birch||Betula lenta|
|7.78||Limber Pine||Pinus flexilis|
|7.78||Tasmanian Myrtle||Lophozonia cunninghamii|
|7.77||Northern Catalpa||Catalpa speciosa|
|7.76||Spanish Cedar||Cedrela odorata|
|7.76||Australian Red Cedar||Toona ciliata|
|7.74||Paper Birch||Betula papyrifera|
|7.73||Red Bloodwood||Corymbia gummifera|
|7.72||Black Willow||Salix nigra|
|7.71||Water Tupelo||Nyssa aquatica|
|7.70||European Beech||Fagus sylvatica|
|7.69||Incense Cedar||Calocedrus decurrens|
|7.65||Brazilian Pau Rosa||Aniba rosaeodora|
|7.64||Caribbean Pine||Pinus caribaea|
|7.63||European Larch||Larix decidua|
|7.62||Rose Gum||Eucalyptus grandis|
|7.62||Grey alder||Alnus incana|
|7.59||Hormigo Negro||Platymiscium dimorphandrum|
|7.58||West African albizia||Albizia ferruginea|
|7.57||Yellow Meranti||Shorea spp.|
|7.55||Pitch Pine||Pinus rigida|
|7.54||New Guinea Walnut||Dracontomelon mangiferum|
|7.54||Pacific maple||Aglaia cucullata|
|7.50||Jeffrey Pine||Pinus jeffreyi|
|7.49||Shortleaf Pine||Pinus echinata|
|7.48||Queensland Maple||Flindersia brayleyana|
|7.48||Table Mountain Pine||Pinus pungens|
|7.47||Port Orford Cedar||Chamaecyparis lawsoniana|
|7.42||Eastern Hemlock||Tsuga canadensis|
|7.38||Bigleaf maple||Acer macrophyllum|
|7.36||Yellow silverballi||Aniba hypoglauca|
|7.36||Northern Silky Oak||Cardwellia sublimis|
|7.34||Mexican alder||Alnus jorullensis|
|7.33||Jack Pine||Pinus banksiana|
|7.33||Spruce Pine||Pinus glabra|
|7.32||Longleaf Pine||Pinus palustris|
|7.31||Atlantic White Cedar||Chamaecyparis thyoides|
|7.31||White Poplar||Populus alba|
|7.30||New Zealand kauri||Agathis australis|
|7.30||Dark Red Meranti||Shorea spp.|
|7.29||Common Lime||Tilia x europaea|
|7.29||Ponderosa Pine||Pinus ponderosa|
|7.27||Alder-leaf Birch||Betula alnoides|
|7.25||Rose sheoak||Allocasuarina torulosa|
|7.25||White Willow||Salix alba|
|7.24||Lignum Vitae||Guaiacum officinale|
|7.22||Hoop Pine||Araucaria cunninghamii|
|7.20||East Indian Kauri||Agathis dammara|
|7.18||Nyatoh||Palaquium spp. Payena spp.|
|7.18||Blue Gum||Eucalyptus globulus|
|7.17||Spotted Gum||Corymbia maculata|
|7.16||Alaska Paper Birch||Betula neoalaskana|
|7.15||Burmese Blackwood||Dalbergia cultrata|
|7.15||Loblolly Pine||Pinus taeda|
|7.13||White Seraya||Parashorea spp.|
|7.12||Quaking Aspen||Populus tremuloides|
|7.10||Red alder||Alnus rubra|
|7.10||Khasi Pine||Pinus kesiya|
|7.07||Goncalo Alves||Astronium graveolens|
|7.05||Siam balsa||Alstonia spatulata|
|7.05||Red ash||Alphitonia excelsa|
|7.03||Raspberry jam||Acacia acuminata|
|7.01||Lodgepole Pine||Pinus contorta|
|6.99||California red fir||Abies magnifica|
|6.99||American Chestnut||Castanea dentata|
|6.99||Australian blackwood||Acacia melanoxylon|
|6.98||Heavy hopea||Hopea iriana|
|6.95||Western Larch||Larix occidentalis|
|6.94||Eastern White Pine||Pinus strobus|
|6.93||Western Hemlock||Tsuga heterophylla|
|6.89||Mountain Ash||Eucalyptus regnans|
|6.89||Sugar Pine||Pinus lambertiana|
|6.84||Red Mangrove||Rhizophora mangle|
|6.84||Pinyon Pine||Pinus edulis|
|6.81||Tree of Heaven||Ailanthus altissima|
|6.81||Norfolk Island Pine||Araucaria heterophylla|
|6.79||Light Red Meranti||Shorea contorta|
|6.76||Western Red Cedar||Thuja plicata|
|6.75||Red Pine||Pinus resinosa|
|6.71||Rock sheoak||Allocasuarina huegeliana|
|6.70||Indian Silver Greywood||Terminalia bialata|
|6.69||Black Cottonwood||Populus trichocarpa|
|6.69||Pin Cherry||Prunus pensylvanica|
|6.66||Noble fir||Abies procera|
|6.66||Ocote Pine||Pinus oocarpa|
|6.64||Western White Pine||Pinus monticola|
|6.64||Black Spruce||Picea mariana|
|6.63||Pond Pine||Pinus serotina|
|6.59||Indian pulai||Alstonia scholaris|
|6.58||Engelmann Spruce||Picea engelmannii|
|6.57||White Spruce||Picea glauca|
|6.55||Andean alder||Alnus acuminata|
|6.53||White fir||Abies concolor|
|6.49||Norway Spruce||Picea abies|
|6.48||Coracao de negro||Swartzia panacoco|
|6.47||Sumatran Pine||Pinus merkusii|
|6.41||Yellow buckeye||Aesculus flava|
|6.39||Yellow poplar||Liriodendron tulipifera|
|6.36||Bigtooth Aspen||Populus grandidentata|
|6.36||European Aspen||Populus tremula|
|6.36||Subalpine fir||Abies lasiocarpa|
|6.35||Balsam fir||Abies balsamea|
|6.34||Sitka Spruce||Picea sitchensis|
|6.27||Hard milkwood||Alstonia spectabilis|
|6.24||Broad-leaved apple||Angophora subvelutina|
|6.20||Eastern Cottonwood||Populus deltoides|
|6.18||Balsam Poplar||Populus balsamifera|
|6.18||Manil montagne||Moronobea coccinea|
|6.17||Nepalese alder||Alnus nepalensis|
|6.14||Red Spruce||Picea rubens|
|6.14||Black Ironwood||Krugiodendron ferreum|
|6.12||Fijian kauri||Agathis macrophylla|
|6.09||Pacific silver fir||Abies amabilis|
|6.05||Pink ash||Alphitonia petriei|
|5.96||Austrian Pine||Pinus nigra|
|5.71||Grand fir||Abies grandis|
A Closer Look at MOE and Wood Anatomy
Regardless of one’s feelings about the results of the bow index list above, it is almost universally recognized that modulus of elasticity (MOE) is a very important measurement for wood bows. After all, the very act of bending an archery bow has direct bearing on this measurement. But unlike wood hardness, which has been shown to have a very strong and predictable relation to wood densityWiemann, M. C. (2007). Estimating Janka hardness from specific gravity for tropical and temperate species (Vol. 643). US Department of Agriculture, Forest Service, Forest Products Laboratory., MOE has shown much more of a variation with relation to a wood’s density. In short, there appears to be some woods that are heavy, where you’d expect them to be commensurately stiffer as well, but that’s not always the case. There appears to be at least one other factor in play in determining MOE.
Microfibrils are tiny strands found within the cell walls of wood. Usually they run parallel with the wood grain, but that’s not always the case, and they can sometimes run at varying degrees off of parallel, which is called the microfibril angle (MFA). (See the notes in red lettering pertaining to the central S2 layer in the reference image below.)
Note this is not to be confused with interlocked or spiral grain found in some wood species, as microfibrils are much smaller—it’s possible to have a wood with straight grain but angled microfibrils.
It appears that the microfibril angle (MFA) is the hidden variable that accounts for (most) of the remaining variation in predicting MOE, since the value is so hard to predict if relying on wood density alone. In studying species of Eucalyptus, it was found that “MFA alone accounted for 87 percent of the variation in MOE, while density alone accounted for 81 percent. Together, MFA and density (as Density/MFA) accounted for 92 percent of the variation in MOE.”Yang, J. L., & Evans, R. (2003). Prediction of MOE of eucalypt wood from microfibril angle and density. Holz als Roh-und Werkstoff, 61(6), 449-452. So an increased off-axis microfibril angle contributes to a decrease in MOE. (Specifically, the microfibril angle in the larger central S2 layer pictured above.Donaldson, L. (2008). Microfibril angle: measurement, variation and relationships–a review. IAWA Journal, 29(4), 345-386.) But perhaps equally important, though easy to overlook, the same study found that “MFA had little independent influence on MOR.”Yang, J. L., & Evans, R. (2003). Prediction of MOE of eucalypt wood from microfibril angle and density. Holz als Roh-und Werkstoff, 61(6), 449-452.
In practical terms, the microfibril angle acts as a special variable that allows otherwise dense and strong woods to have a disproportionately low MOE with no effect on the MOR. An increased density would also mean an increase in both MOE and MOR, which would have little to no effect on a wood’s bow index. But woods with a high MFA could have the peculiar combination of a high MOR and a low MOE, exactly what we’re hunting for.
Are you an aspiring wood nerd?
The poster, Worldwide Woods, Ranked by Hardness, should be required reading for anyone enrolled in the school of wood nerdery. I have amassed over 500 wood species on a single poster, arranged into eight major geographic regions, with each wood sorted and ranked according to its Janka hardness. Each wood has been meticulously documented and photographed, listed with its Janka hardness value (in lbf) and geographic and global hardness rankings. Consider this: the venerable Red Oak (Quercus rubra) sits at only #33 in North America and #278 worldwide for hardness! Aspiring wood nerds be advised: your syllabus may be calling for Worldwide Woods as part of your next assignment!
|↑1||Bjurhager, I., Gamstedt, E., Keunecke, D., Niemz, P. & Berglund, L. (2013). Mechanical performance of yew (Taxus baccata L.) from a longbow perspective. Holzforschung, 67(7), 763.|
|↑2||Wiemann, M. C. (2007). Estimating Janka hardness from specific gravity for tropical and temperate species (Vol. 643). US Department of Agriculture, Forest Service, Forest Products Laboratory.|
|↑3, ↑5||Yang, J. L., & Evans, R. (2003). Prediction of MOE of eucalypt wood from microfibril angle and density. Holz als Roh-und Werkstoff, 61(6), 449-452.|
|↑4||Donaldson, L. (2008). Microfibril angle: measurement, variation and relationships–a review. IAWA Journal, 29(4), 345-386.|
do you think that Australian black wattle would make a good bow
I am brand new to this, really just decided to try and make a bow. I am in Tucson Az, not alot of wood like Hickory or Oak ect. Does Mesquite make a good bow? What other suggestions. A silly question about the above index….here goes…lol so the higher the index number the better?
I live in the highlands of PNG and recently bought a 6 foot long bow from an American expat. It is only about 35 pounds draw weight and I would like to back it with something to bring the weight up to at least 45, preferably 50-55. Any suggestions for a wood I could access here that would work well?
Bamboo may be your best bet
As others have mentioned below, you can use the modulus of resilience as a guide for how good a wood will be for making bows. Dividing this quantity by the density of the material gives you the amount of energy the wood can store per unit of mass before breaking. The higher this value, the lighter the limbs will need to be for any given draw weight, which makes for a more efficient bow. The formula to calculate this is E/kg = MOR^2 / 2 / MOE / rho, where rho is the density of the wood. The two is… Read more »
Was planning on planing down a small branch of ash and some stout boxelder maple before gluing them together. Does that seem like a good combination for composite recurve wings?
Could you possibly use crêpe myrtle or Mamosa?
Yes it will bow
The foremost metric of bow performance is speed of cast. The speed of cast of a bow has a hard upper limit at the speed attained by the center-most point of the string during a dry-fire. Obviously, you don’t want to damage the bow, so the arrow should be massive enough in relation to the draw weight of the bow so as to keep the release speed of the arrow much slower than the dry-fire speed. The faster a bow is capable of dry-firing, the faster it can propel an arrow sufficiently massive so as to prevent the limbs from… Read more »
Hallo John, I could not quite figure out the formula used here, would it be possible to let me me know how to calculate this for other woods. Thanks
Of course Tim. The simplest form of the formula I used for the self-fling speed v in ft/s is: v=68.07*R/sqrt(E*W), Where R is the modulus of rupture in psi, E is modulus of elasticity in psi, and W is average dried weight in lb/ft^3. Note also that the maximum possible tip speed of a limb can be substantially faster than the self-fling speed of the wood from which it is made. The tip speed attained is a function of both the self-fling speed, as well as geometric properties of the limb, such as its cross section shape, its length, and… Read more »
I’m confused. Where does time enter the equation for self-fling? There is no time in any of the components of the formula that I can see.
The time dimension is buried in both the modulus of rupture and elastic modulus. Note that each of these has units of pressure, or psi. lbf/in^2. lbf is a unit of force, which is mass times acceleration. And finally, acceleration is ft/s^2. That’s where the time unit comes from.
That’s about what I figured. Thanks much.
it does not make sens to me that the wood has to BEND EASILY… I would say that it has to be HARD TO BEND and hard to break.if its easy to bend no power will be stored in it. if you put it to the extreme…..if it were so easy to bend that just holding it from one end horizontaly … the other end would drop under its own weight.if its hard to bend then you have to put energy in pulling it thus loading the limbs does that make more sens.
Dan, I can see how the effect of varying the resistance to bending might be counterintuitive. At least for non-engineers/physicists. Usually stronger woods tend to also be stiffer in proportion, and being that the modulus of resilience is more sensitive to changes in strength than to changes in stiffness, so we have a case of confounding variables. Say for instance wood species A has half the elastic modulus of wood species B. Given no other information about these materials, there is a greater likelihood that species B will store more energy than species A and perform better as a bow… Read more »
Yeah—like rope is easy to bend, hard to break. I’ve never seen a rope bow.
the Inuit make there bows with sinew rope as both string and backing material. As there is very little in the way of good long pieces of material for the purpose of bow making in the arctic circle, they take small sections of very straight grained wood; interestingly enough, Spruce, being some of the poorer quality species mentioned, is one of the primary sources chosen. The sections are spliced together with pieces of antler or bone, using cables of sinew instead of glue, as the arctic temperatures would instantly turn hide or fish bladder glues, used in nomadic step cultures… Read more »
I’m really surprised by the results, especially by the downy birch. Almost everywhere I’ve looked people tend to frown upon birch for making bows. I recently acquired a nice stave of downy birch but didn’t think much of it, wasn’t sure I’d even use it. but it turns out turns out I might have stumbled on gold which is nice cause there’s tons of it around here.
not one mention of Australian native trees
Maybe as there’s no historical aboriginal use of bows?
I do know that Spotted gum makes a good flar bow, i’ve made one.No, I do not think the Aboriginals were developed enough for bows they were still throwing pointy sticks,200 years ago,
I am impressed by the response to my test entry “cedar”. I have an excellent Virginia Juniper in my front yard, and I disdain the practice of calling it and the Thuja plicata “red cedars”
So, in the event someone wanted to give a metal bow a try, I did a little digging with comments here and elsewhere to look at the viability of Grade V Titanium for bow making after seeing how springy it was in another application. Based on MOR/MOE, titanium is on the correct scale with a value around 8 or 9. Based on MOR/Density (suggested by some comments as more helpful), grade V titanium initially appears to have a .22 compared to .15 for Osage Orange (MPa/(kg/m^3)). Given this math, it seems reasonable to say that this treatment of titanium would… Read more »
Just from playing around in the yard I believe wild shrubs would make a good bow wood so I think i’ll make a full size bow to to see
Honeysuckle shrub is very interesting for bows and arrows.
yes, better than yew, especially the sapwood. mock orange, sea buckthorn, plum and laburnum also make very good bows
What about carambola wood? It s main to be flexible wood and strong
Young’s modulus is determined by measuring short deflections under load. It is a constant which reflects a material’s inherent stiffness. Modulus of Rupture is measured at the final breaking point where the wood gives way under load regardless of the amount of bend before the breakage occurs. A bow needs to flex in a dramatic way, so while these two measurements are important, they can’t tell the whole story. A low stiffness wood like pear could be too brittle and woods with higher stiffness to breakage ratios like hickory and black locust could make excellent bows. Since stiffness is a… Read more »
Bornean ironwood is it good for bowmaking?
Here is the post with file :) After seeing all the comments about the different ways to calculate the bow wood index I combined the two for a better overview. The difficult part is that even tho the calculations are based on the physical properties of the wood, things like heartwood/sapwood, interlocked grain, great compression strenght or the addition of a rawhide backing could alter these numbers significantly, which would mean that the number as calculated are not a 100% accurate in real life. A great example of this is juniper, the MOR/MOE *1000 gives 10.31 which is not to… Read more »
Hei i cant see the file anymore, can you send it to my email? ( I started a new project making a bow from willow tree) so iwould like to see if yoi have data for it :) )
What is more important than computing an index, for any wood, regardless of the method used, is the fact that within any species of tree the qualities of individual specimens can vary by 25% or more. (US Forest Service Lab) This basically means that the published numbers aren’t relevant to the resulting bow tillered from any billets, stave, or board just because the wood is labeled. Equally significant is that the published values are obtained by testing samples with very significant sectional deviations from the cross sections of tillered limbs regardless of the bow design. (For example: testing a sample… Read more »
Hi there, After seeing all the comments about the different ways to calculate the bow wood index I combined the two for a better overview. The difficult part is that even tho the calculations are based on the physical properties of the wood, things like heartwood/sapwood, interlocked grain, great compression strenght or the addition of a rawhide backing could alter these numbers significantly, which would mean that the number as calculated are not a 100% accurate in real life. A great example of this is juniper, the MOR/MOE *1000 gives 10.31 which is not to bad, the MOR^2/MOE/dried weight gives… Read more »
It is really hard to find good wood with the ability to bend easily without breaking. Thank you for your help.
Higher result = lighter limbs for the same draw weight = faster and more efficient bow
Lower MOE makes shorter and more efficient or more reflexed and powerful bows
The MoR need to be squared because draw weight*length at failure give the maximum amount of energy the wood can absorb and the MoE is the ratio draw weight/draw length
Thanks for all your hard work and effort that it took you to put this posting up for all of us that live the art of bow making. We are always looking for the best way to build our perfect bow and the data you have supplied is a valuable resource for us again koodoos to you and your hard work on this matter
Thank you for posting this – It always crosses my mind when looking at potential bow woods! Incidentally, rowan should feature high on the list too; at 11.61 it would be higher than osage and yew… Norway maple is quite high too, and black locust and hophornbeam (reputably good bow woods are very low…) Where I think the difficulty comes from is dealing with the different potential sizes/geometries of limbs. Perhaps the ‘bow index’ is best used for determining how good a wood is at having narrow/deeper limbs? Yew and Osage are the clear examples – their limbs can be… Read more »
Contrary to what some say a low MOE is in fact desirable in a bow-wood, those that deny this just don’t have a proper understanding of what MOE means. The ratio of MOE to MOR is as good a method as any I have seen of identifying good bow-wood and after more than 20 years of making bow I have seen many. I commend you on your efforts
Be specific as to what species of hickory. They aren’t all equal.
Did you consider bamboo at all in writing this article?
I am reposting my initial comment, because this page still presents its wrong approach to determining the value of bow wood. The page should be taken down because it is harmful to the investigation. : I have been making bows for more than 15 years. My experience and logic say you have the concept diametrically opposed what is desireable for the MOE. You say wood needs to be EASY to bend. Wrong. What is needed is wood that is HARD to bend and hard to break. That allows less wood to do the work. Less wood means less mass to… Read more »
We may be comparing apples to oranges here. It should be noted in this article, the values listed above are for bows made of a single piece of wood, not laminated. It should also be noted that what is really being examined here is the RATIO of MOE to MOR, and nothing more. I think that the equation tends to eliminate most lighter woods anyway, simply by virtue of the fact that lighter woods tend to have a proportionally better MOE (versus MOR) as weight decreases. I don’t think anyone has this subject completely figured out. One of the characteristics… Read more »
As far as the Argentine Osage is concerned, it was probably not known by those making bows during the centuries when wood was the most used bow material. Second, you should be aware that no data exists for DRY Osage orange. Either the Forest Products Laboratories didn’t run tests on dry Osage or the data never got recorded. I’m sure all your data is from the FPL. I have been in contact with them several times and they have no data for dry Osage and no plans to do any testing. If there are numbers for the Argentine Osage, that… Read more »
FPS on release is pretty major…Yew and Bamboo both excel unless I’m mistaken. Also fiberglass (which sucks at most other refined details).
It’s a grass. Yes. …How on earth does that matter in any way concerning how to back a bow?
i live in norway what is the best wood here?
English/Spanish (European) yew, followed extremely closely by the not-almost-extinct…yet ‘Pacific Yew’.
Others would argue osage, and several of the densest tropical woods–say, Ipe or heartwood. Hickory is ‘easy’, but is the most boring, poor-performance wood in the world next to self-backed pacific yew
Do you have elm (wich elm’s traditional)? White ash is good, but regular ‘European Ash’ is better/tougher. And there’s white oak. You don’t have Oregon Oak…but the movement of many European beeches (better than west hemisphere) into Norway expands options. …Also the maples. And the oak comin north, also. Junipers, I assume you have a variety–you need a huge amount of wood. Applewood, pear, and also Laburnum. Various types of maples (Norway Maple is good). Welsh oak (if you can get it, decent, and European Holly isn’t bad–please don’t tell me they have English holly sometimes in the land of… Read more »
Bob, my wife and I visited your incredibly beautiful country two years ago. We were only there for a day and two nights but we did Norway in a Nutshell and saw a lot of the country. I did not see a single yew tree, taxus baccata, but it does occur in Norway. I think that would be your best native wood, but, from what I’ve read, it’s illegal to cut yew in Norway!
What about cupressus macrocarpa? It’s got long straight pieces and the MoR/MoE relation is 10.39, looks nice.. I’ve readed that some have made nice bows laminating alaskan yellow cedar wich has a worse MoR/MoE relation.. I think i’ll try and tell what about it ;)
Stiffer is better in terms of strength resisting the draw, allowing higher poundage– yet at the same time, too stiff with too little MOR to resist the breakage means the limb would not bend that far before it broke, limiting draw length and reflex design. Finally this does not factor in density at all, where higher mass limbs rob cast, because the moment (physics) is further diverted from arrow to limb. In actuality, there is no good metric to say which wood is the best for all the bow designs in the world out there: – Some bows have shorter… Read more »
Elasticity IS still important for short bows–for the arrows as well as the bow. But your point is taken.
-As for the point about more massive limbs….that’s why European Yew will always beat Osage by more than a nose, with faster, better casts and less wasted energy :)
Otzi, the 5000 year old ice man mummy found in Europe had two kinds of wood with him. He had Cornel and Verbinum. The pbs show (Nova) wasn’t clear on which type of wood was used for his bow and arrows and which was used as an axe handle.
I’ve seen a recent article wich said the axe’s wood was yew
Is black cherry a good bow wood
Yes it is, if backed by something else. For much more detail, there’s an entry in ‘The Traditional Bowyer’s Bible’, which you can page through on google books.
Yes and no. Can have truly great characteristics, but it’s unreliable. It fails easily and unpredictably. Chrysals for no reason you can think of. But people tell me it’s almost self-backed yew, sometimes. Treat it right (whatever that is…), if you give it a shot? That’s what the kids are saying, anyway.
I have and odd question has anyone tried crepe myrtle as a bow wood
I recall the name coming up, so I’m going to say yes, and that…it’s probably supobtimal, but possible to use. Mostly guessing.
This is an interesting article to get people talking about how mechanical properties relate to bow performance. There are several problems however. 1) the value the author has effectively calculated is (%strain at failure)x10. In other words the change in length of the material at failure(rupture). 2) it ignores the density of the wood. modulus of rupture is a measure of strain at failure. Strain is force/area. So this is only a relevant value for comparing two woods of identical mass since limb mass will determine performance and not limb cross sectional area. 3) it assumes that a wood which… Read more »
A bow is a spring. How well does MOE describe a spring? An easily bent bow is a weak bow. Rubberbands bend easily. Stronger bows require more strength to bend then weaker bows. So, I doubt a low MOE would describe a good bow.
The MOE would be matched to the strength of the person using the bow to know if it the bow is too stiff for them to draw.
The thing is, a bow with a high MOE and a medium MOR will be strong but will make a bow with a very shallow and wide cross-section which isn’t very aerodynamic. For example although Hickory does make great bows, it relies on its raw strength rather than an efficient transfer of energy. You commonly see hickory short-bows so the ends of the limbs won’t be too far away from the center line to create much drag and the bows tend to not be the highest poundage because the wood is so thin. Hickory is great for backing a bow… Read more »
The two post prominent Australian bowwoods seem to be Red Ironbark and Spotted Gum. Yet using this method they both rank very low (7.37 and 7.17 respectively).
My understanding has always been that high density, high MoR woods were most likely to make good bowwoods.
One thing that should be included in the calculation is the density of the wood. A low density would make the limbs of the bow quicker. The equation would be modified be dividing by the density.
Question: what is the source that supports a low modulus? For 2 identical bows, the one with the higher modulus would have a higher stored energy and draw weight at the same length of draw. If the same draw weight is desired, then the limbs could be made thinner and lighter with the higher modulus wood. This would result in quicker bow limbs.
I wonder if we could get the raw numbers for these? I would imagine you’d want a wood with neither a very high, nor very low Modulus of Elasticity, since a bow too easy to bend ends up with less power, yes?
I live on the West coast of Australia, and have been trying some local timbers in bow building with little success. Has anyone had any success with Australian timbers for bow building
Spotted Gum and Red Ironbark are the two premier aussie bowwoods I’ve heard of. For the most part you want high density, high MoR timbers.
Can anyone tell me what is the best glue to laminate a wooden bow?
Tightbond, epoxy, and hide glue all work fine, if applied properly.
I’m chopping down a Blackwood Acacia (Australian Acacia, Black Acacia, Myrtlewood?) Tree, and I’ve got a few projects lining up, one of which is a Recurve or Long Bow and the other is a Cross-Bow/Mini-Cross-Bow or three. My questions are how does this wood add up for use as a Bow. It seems to be up there with the best Hickory in terms of Strength, Rupture, Harness, Elasticity, and Crushing Ratios. But, it doesn’t show up anywhere as a Material for a Bow. Is it because I only checked the Top Ten Search Listings on Google. Or, because the Australians… Read more »
Any kind of acacia will do the job
Not true. Many tribes in Australia used a spear with woomera, which operated in a similar way to a bow and arrow, in that the woomera launched the spear (a much larger projectile) which increased the speed and accuracy of the throw when done by an experienced practitioner.
This is perfect for what I was looking for! I have been looking for good wood to make bo’s and Jo’s from and I wanted something that would flex, but not break. Perfect.
Unfortunately, I have to agree for bows. Too low an MOE is not ideal. You need the wood to be able to take all the force without bending too much and then deliver it back into the arrow. If it bends too much you will lose force. But I’m no scientist.
However for my purposes this has been fabulous as this is exactly what I was looking for, thank you. I’m making something (it’s hard to explain) that requires exactly this: migh MOR/ low MOE. Imagine my joy!
Thank you very much.
This is an awesome article, but I have to agree with James Davis. The best recurve bow I’ve ever shot (that was mostly wood) was carved in Hickory.
I think the real value to this article is showing woods that work well in tensioned setups.
A furniture design I’ve been working on required tensioned lengths of wood for the legs and armrests, and this article has helped me narrow down the list of woods available for this purpose.
Ugh. Hickory. I’m glad it did something for you, but…it’s the short bus of bow-woods, for me–so often recommended in suboptimal circumstances because “hey, at least you won’t break a hickory bow!” In efficiency, power, subtlety it doesn’t compare to a bow-material that can send arrows down-range through compression, like a rebounding string. It’s just cheap, robust, carries tension and is stable–and is easily covered in fiberglass. Would you like to buy a still-wonderfully functional Hickory longbow?
(Cough) -Just a personal feeling about it–I meant no offense.
This is an interesting article. I agree with Eric regarding the ratio of MOR to MOE. Hickory is known to have an excellent MOR but it also has a very high MOE. That I believe explains its inferiority to osage or yew. Black locust has a slightly lower MOE than hickory but a similar MOR- again explaining its superiority. I have made bows from osage, muninga and chinaberry and of none of them took much set (plastic deformation). The only problem with just using this ratio is that it doesn’t take into account the fact that you still need the… Read more »
A true MOR is measuring the bending strength of the wood, so crush would be included in the value. There is a good article at ask dot com. That is unless you are asking about transverse crush (cross grain). That value is typically directly related to wood density. Balsa would be immediately discounted because the light grades would crush in the archer’s hand.
What a useless response, devoted to demonstrating alleged technical knowledge that’s not useful without context!
A very qualified yes to this: if you’re building laminate bows – not selfbows – you get a different result for the back wood (the part of the bow facing away from the archer, requiring strong tensile strength) and for the belly (where compression strength is most important). One of the reasons yew has the primacy it does in European bowmaking is that it is, in effect, a laminate itself – the sapwood and heartwood have quite different qualities. Hickory is inferior to practically nothing as a back wood (not sure how a hickory-only selfbow would work, though I’ve seen… Read more »
Thank you for your efforts and work in providing these correlations of tests and data. For those of us who battle the obsession of bow-making all additional information and studies are always welcome.
P.S. Your disclaimer “…to foster imagination and exploration” is appreciated but probably not necessary :)).
I have been making bows for more than 15 years. My experience and logic say you have the concept diametrically opposed what is desireable for the MOE. What is needed is wood that is HARD to bend and hard to break. That allows less wood to do the work. Less wood means less mass to be put in motion by the energy stored in the bent bow, resulting in faster arrow flight. Black locust the hickories, white ash and others balance the force required to bend them quite well with the force required to break them. Perhaps a formula recognizing… Read more »
It seems to me that the best bow material for bow making is bamboo. I don’t know the MOE or MOR of the wood but it will flex and return to it’s original shape better than the ones I have made from hickory, hard maple and Pacific Yew. Granted, the grain of these species is sometimes erratic. Tonkin Bamboo is a good species partly because it can be gotten in larger diameters 3″ to 4″ or so and split to 2″ strips, flattened, and planed to thicknesses for laminating. Bamboo in general is straight grained wwhich is part of the… Read more »
What poundage are the so. eastern bamboo self bows? do they shoot arrows or bamboo darts like their crossbows? Although their bows on the crossbows are 4′ Mountain Yard mahogany.
BTW HOWARD HILL never shot bows less than 110 lbs draw weight. the movie with Errol Flynn he used that 110lb draw weight bow and the guys that he shot in the chest had 1″ wood boards backed with 1/4″steel and they hated to get hit with those arrows! they were really knocked off their horses! H.H. loved the bamboo bows.
you would have to change never to most of the time. i still have the pictures of howard hill shooting my fathers recurve bow. my fathers name was frank murphy and he was a skilled bowyer out of new york.
locally his diamond bow company was a favorite among many new york target shooters and hunters. the chance meeting of HH at a field archery event was one of his favorite memories.
Not even during the Great Leap Forward? (42 million dead for no important reason)? The continued Cultural Revolution?
–I guess all the hundreds of millions of historical slave-owners must have been right, too! It’s too many to be wrong.
-Bamboo may be ‘straight grained’ but it simply doesn’t last as long as its partners in crime–great tensile strength, but it needs replacing before a battle’s over.
-It’s unlikely Howard Hill shot the bow-hunting sequences in Errol Flynn’s (thematically rich AND historically accurate) masterpiece. More likely, I’d expect he was, say, stunt choreographer, or an AD.
Hundreds of millions of slave owners?