Wood prods, general question

Do people just not mess with them? It seems like most are metal or fiberglass. I have been playing with treating and tying bamboo for fun but it seems like there could be some potential there. Also, fiberglass backed hardwoods seem light and efficient but I don't know the what the upper limits are on poundage. I imagine that it takes a much longer wood prod to match the draw weights of the short metal ones.

I suppose it's all down to what type of bow you are after but I would be interested to hear thoughts about this from people who have thought a lot more about it than I have.

I think that making a wooden prod in a crossbow weight (80lb +) would be difficult. Probably more do able with a good wood and a bamboo or fiberglass backing. But I think it would still be on the long side. I believe that I have some Ipe around here somewhere and some fiberglass, so one of these days I might try making a wooded crossbow prod. Have some experience making wooded bows but I think it will be a challenge. any hinges or imperfections are going to be punished.

I don't Know about modern Wood bows but there are some suprisingly powerfull historical wood bows, reaching through time as far as the 1900's as norwegen whale bows. The most powerfull wood bows were the rampart bows in vogue in the 14-15C. Some mesurements from a smaller example in the armoury at Solothurn, Switzerland measures; 127cm long and 113 in the cherry tiller. Ivory lined lock, boxwood nut and steel trigger. The bow is yew 1.5m of eliptical cross section 7.2cm broard and 7.5 cm deep. At the end of the limbs it is 2.4cm broard and 3.6cm deep wraped in parchment for weather proofing. the bolt grove is 43cm long. The end of the bow is square section meaning it was probably spanned with an english windlass. an incredably powerful wood bow.
A Norwegen whale bow in Nordsks Muskeet, Stockholm is 95cm long has a bolt grove 38.1cm long. The bow is yew127cm long 7.3cm broard at centre and 3.5 cm thick it has a flat belly rounded Back and narrow flat edges. It is spanned by a primitive goats foot lever.
info from English Royle Armoury monograph 3 isbn 0 948092 20 3.

So powerfull all wood bows will be large but the upper limits on poundage are limited only by the size of yew stave you can cut and tiller. DaVinci demonstrated the max wood span to 30' or so.

Horn (composite wood, horn and sinew) and steel bows will have similar sizes to each other. Steel prevailed because of ease of maintenence and construction not because they were any more powerfull.

Bamboo laminated bows ! Had a friend who was making regular bows from bamboo and with bamboo laminates. Not a one of the 6 was a sucess. The all bamboo bows broke at the knots as basilisk120 sugested. laminates using bamboo with the knotts shaved off were less problem to work with but not much more durable. Laminates made with zig zag glued sections without knots were superior but only good in compression.
Some one who makes the japanese Dikyou bows could advise on bamboo bow construction. ( I think they might be made using green and seasoned wood)

In the European composite cross bows the laminates of horn or whale bone always run horizontaly through the prod rather than along the length of the bow as in regular bow construction and are bound in considerable thickness of sinew up to a third or half the volume of the bow.
Some asian crossbow bows do have horn laminates running along the belley of the bow.

Thanks guys, some great info there. Where does a guy get whale bone these days?

I live in Austin Texas and I was wondering if longhorn cows are a good source of bow bone?

Testhero- That was definatly an informative run down on whaling bows. I had no idea how they were made but good to know. Oh a friend of mine might have some information on making a bamboo laminate bow and more specifically on the joints used. I'll see what I can find.
jake-owa- Yeah I'm sure that longhorn would be a fine source for cow bone and an even better source for horn If you could find a good source for horn that would rock. And seriously yet anouther person from Austin on this forum? Whats up with you Texas guys (and gals) and crossbows. I'll have to wave to all of you when I drive by Austin this Thanksgiving. Going to visit my parents in Houston and maybe hit up the Texas Ren Fest.

You know, I just moved here from Oregon so I don't know. It may be something in the water. I used to make bows, but since moving here all I can think about is crossbows.

I suggest making the wooden bows for crossbows as large as possible, as small wooden bows are very weak. For example, one of my crossbows has a small 75cm/2,5ft long wooden bow and has draw weight of ~15 pounds. The bolts have maximum energy of ~5 joules and optimal bolt weight is mere 4 grams (1/6oz). As a comparison, 30 pound handbows seem to generate around 20-25 joules of energy, so my little crossbow is pretty much a toy. Also, a steel bow of similar dimensions would weigh about 10 times more and generate roughly 10 times more energy.

My next wooden bows will definitely be much longer (100cm+) and heavier. I've reasoned that using a short draw length and making the bow thick helps in getting higher poundages out of the bow. Of course, dry-fire speed (and efficiency of energy transfer?) suffers, but that's not an issue unless aiming for maximum distance with very light bolts. Another trick would be to tiller only/mostly in thickness; this allows balancing the stresses in each part of the bow with minimal reduction of mass (and energy output). See this link for more thorough information.

My most recent prods are around 55 cm and quite strong but I have put their effective stacking power beyond the pull of the bow. It suffices and does quite a job slamming the 5"X5/8" bolts through 4 layers of cardboard but I definitely know more for the next prods.

Learning, a little at a time. Thanks for the link, very useful.

jake-owa wrote:My most recent prods are around 55 cm and quite strong but I have put their effective stacking power beyond the pull of the bow. It suffices and does quite a job slamming the 5"X5/8" bolts through 4 layers of cardboard but I definitely know more for the next prods.

Learning, a little at a time. Thanks for the link, very useful.

No probs. You might find some other interesting articles on my site's main page:

• http://users.utu.fi/sjsepp/#tinkering_in_the_physical
  

Great stuff there. It's guys like you who make the internet a wonderful thing.

I have arrived at about a 20" red oak prod with 3 layers of glass weave and 4 coats of resin that seems pretty resilient. I am not shrink wrapping it or anything like that but it seems to work pretty well for these little toy bows. I haven't seen any cracking or lifting of the regular FG resins. I will buy some shrink wrap and mess with glass layers between woods next.

This weekend: trip to the junkyard for....well, you know.

All the powerfull Medeval wood bows I am seeing dimensions for are both Broard and very deep looks like a deeply built Prod is nessesary. from memory the horn bellied wood bow in the tower of london is also very deep.
(er why are we refering to the bow as a prod ? I am willing to go with the convention but would like to know)
basileus I was about to argue your assertion thet Steel bows are 10 times more powerfull than wood but once I got into the guts of your article and stats I am happy. They can be constructed to10x the draw weight if they are 10x the mass of a wooden Bow using the high stacked pryamidal tapering limbs design you specify.I havn't seen a bow pre 1700 that is constructed using all thoes improvments. Can you point me towards one. I would love to find one.
Almost all of the Wood prods I have seen illustrated or displayed unstrung right down to the Accubalista tomb carvings are recurves. So plan your Building and tillering for this.
jake-owa Cattle bone will be an exelent source of bone for reinforcing and decorating your tiller. I come from NZ and know quite a few bone carvers they especialy value the shin bone. It is harder/dencer afrer a lifetime of repeated impact and compression. It has a shorter/tighter grain. and is a flat good sized piece. It will be very Strong for the lock plates and in addition carves beautiffuly too. other leg pieces and portions of the skull are also good for carving. Less dence bones like ribs do not carve as easily because of the grain and some of the pelvis bones have contrary grain. Long horns should provide suitable Horn. I will check out my friend Sigmunders Longhorn drinking horn when I next visit and see if looks suitable. Having sizeable horns should make your job easier. you can cut longer pieces which should meen fewer joints. you will need a bigger steamer to shape the pieces though. Over here the available supplies of horn are buffalo imported from Africa.
Sinue from the necks of oxen or horses seem to have been prefered.
Records of the Tuetonic knights show principally goats horn was used but also ox horn.
If we want to go into further detail about composite bows we should perhaps start another topic so others interested can join in.

Every one Seems to be shooting very light bolts. One of the secrets the Europeans learned that the west africans with a history from 15C with their niger type crossbows never seemed to learn is that a heavy bolt will do more damage. Taking some of that northern red oak and turning some barrel shaped bolts should make a considerable difference with your casts especialy as you go up in poundage.

The use of the term 'prod' for the bowstave on a medieval crossbow seems to be mostly an American convention. Many european and ancient sources use 'lath', or even 'bowsteel' when appropriate. I have a sneaking suspicion that the word 'prod' actually comes from the term 'prodd' meaning a stone or bullet-shooting bow. Whatever the case, 'prod' is commonly used in the US by most manufacturers and shooters. Personally I don't care what we call it, just so everybody understands. 'Noodly-doodly' might serve just as well.
Geezer.

Thanks Geezer
Yeah European terminology shifts over time and by region too, up untill bowsteel comes into wide use for steelbows (what we call crossbows with steel bows. Crossbow seeming to be a victorian era name).
Prod is good. We all know just what we are refering to when we use it.
We couldn't use 'Noodly-doodly' anyway it is to close to Niddy-noddy and the weavers guilds would be pissed with us.

testhero wrote:
basileus I was about to argue your assertion thet Steel bows are 10 times more powerfull than wood but once I got into the guts of your article and stats I am happy. They can be constructed to10x the draw weight if they are 10x the mass of a wooden Bow using the high stacked pryamidal tapering limbs design you specify.I havn't seen a bow pre 1700 that is constructed using all thoes improvments. Can you point me towards one. I would love to find one.

I don't think there are any historical steel crossbow prods/laths/bows which were constructed with the pyramid front-view profile (with only/mostly width tapering). However, that design itself was used on many traditional _wooden_ handbows dating back to prehistory. I'm guessing that such a design would have been difficult to execute in steel with tools of the period (1350-1600 AD). For example, thin tips of the bow would very easily bend during hardening, and cutting the bow to shape after hardening would be very difficult. Also, I've noticed that forging the traditional medieval nocks works best with wide bow tips: with narrow tips like mine a thin, weak spot is formed between the nock and bow's limbs. Of course other nock designs could have been used instead.

A few words regarding steel and wood as bow materials... steel weighs ~7,8g/cm^3 and I believe most hardwoods used to make bows weight ~0,70 - 0,80g/cm^3. This is also where the ~10x difference in draw weight and power output come. Of course other physical properties of the material do affect this; for example, fiberglass has roughly the same properties as steel but weights much less. Somebody could perhaps provide a link to a comparison?

testhero wrote:
Almost all of the Wood prods I have seen illustrated or displayed unstrung right down to the Accubalista tomb carvings are recurves. So plan your Building and tillering for this.

I would suggest that most recurved bows in illustrations are horn-wood-sinew composites. Recurving all-wood bows does not make (as) much sense, given the limitations of wood as material. This is especially true with short bows (e.g. crossbow prods), which have a very limited draw length where every centimeter counts. Prestressing the material (by recurving) is in fact counterproductive, as it greatly limits the potential draw length of the crossbow. This is also why it does not make sense to recurve heavy steel prods: the act of putting on the bowstring would (pre)stress them so much that they could not be drawn much before breaking. Recurving / prestressing is most useful when the materials used can stretch (sinew, ~10%) and compress (horn) a lot and there are practical draw length limitations (e.g. ~30" in archery).

In the Roman (arcuballista) context recurving makes sense, as bows of composite, recurved construction were widely used in the mediterranean in classical/late antiquity. For example, gastraphetes ("belly bow", a kind of crossbow) invented by Greeks ~480 BC had such a bow.

testhero wrote:
If we want to go into further detail about composite bows we should perhaps start another topic so others interested can join in.

Sounds good. When I get a good supply of sinews I'll definitely make a composite bow for a crossbow. That, and sinew springs for my cheiroballistra .

testhero wrote:
Every one Seems to be shooting very light bolts. One of the secrets the Europeans learned that the west africans with a history from 15C with their niger type crossbows never seemed to learn is that a heavy bolt will do more damage. Taking some of that northern red oak and turning some barrel shaped bolts should make a considerable difference with your casts especialy as you go up in poundage.

There seems to be an optimal bolt weight for each crossbow, depending on what features you consider important. For my ~300 lbs steel crossbow ("Gamma v2" on the stats page) bolts weighing ~50 grams (2 oz) seem to be optimal, giving 60m/s (200fps). Heavier, ~80 gram (3 1/5 oz) bolts are slightly more powerful, but much slower, 49m/s (163fps). Going past 80 grams with this crossbow would increase bolt energy slightly, but drop the velocity too much to be worth it. The same happens at lower bolt weights, but the other way around.

Anyways, it's very difficult to make heavy bolts from factory materials (premade points and round dowel). That's why I have to forge my own boltheads and plane my own bolt shafts.

Well, my newest prod is about 43" and just got the steam treatment last night. The reflex/deflex took at about 50% of what I had it clamped down at. I was thinking of resteaming and curving it more but after reading that I think it will tiller it and glass it.
The last thing I want is to overstress the wood. The prod seems really long for the bow. The draw length will end up about 11.5" or 12" so I wanted to make sure it has enough wood to get the job done. I am hoping to get it's draw weight to over 100# with curves, glass and general thickness. But if it blows I have three more in line.

Here is an interesting article for wooden prod crossbows of 126# across a 14" draw : http://paleoplanet69529.yuku.com/topic/15054/t/A-Simple-Crossbow.html?page=1
Having made a crossbow to this pattern, I can say red oak is probably not the ideal wood. It is stressed right up to the max at 39"ntn. The Skane crossbow this is based on used Yew. It is also better to go to a somewhat longer prod for the sake of longevity. Maple breaks more explosively than Red Oak in the short length. 48" is a better length. The Notch lock trigger is rather stiff at higher poundages, I can see why the Roller Lock became popular. Still, an all-wood crossbow is fun and rather easy to build, and reasonably powerful.

I had not read this thread until Clinker brought it back up. Here is a crossbow I made years ago with a hickory bow/lathe/prod. It draws about 150lb. (68kg.).

Mac

That is a nice looking bow Mac. I really like the thin lines of this bow.

Basilisk120 wrote:That is a nice looking bow Mac. I really like the thin lines of this bow.

Thank you! It's easy to "overbuild" these things. I work hard to try to capture the slimness of the real ones.

Mac

Nice bow Mac, question, How long is the bow and what is the draw length?

Todd

Todd,

Here are some measurements of the bow..

--total length (unstrung) 35 1/2" (900mm)
--distance between nocks on back of bow (unstrung) 33 1/2" (851mm)
-- " " (strung) 33" (838mm)
--total brace height 4 1/2" (114mm)
--stroke 8 1/4" (209mm)
--height of bow near center 1 5/8" (41mm)
--thickness of bow near center 11/16" (18mm)

Note, that the bow is deflexed, and stringing only pulls tips of the limbs back about 1" (25mm)

Mac

Thanks Mac, that is very interesting.
Any idea on it's performance?
Todd

my crossbows with wooden bows

Todd the archer wrote:Thanks Mac, that is very interesting.
Any idea on it's performance?
Todd

It's been years since I shot it through a chronograph, but I think it was in the neighborhood of 150fps. The bolts were relatively light: 5/16 shafts with (70gr?) target points.

I used it as a target bow. I,m sure it is heavy enough for small game, but probably not large.

Mac

Here's a wooden prod crossbow I made. It has undergone a slight transition since the video, mostly cosmetic, but there is yet another short lamination added on the back of the bow. The prod measures at the longest point 37" long (93 cm) and draws about 100 #



And this is it's current look:



The shortest layer of wood is honey locust. The middle layer is sassafrass, and the outermost layer is hickory.