Primitive Archer
Main Discussion Area => Bows => Topic started by: arachnid on April 23, 2014, 07:44:47 am
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Hi guys!
I`m planning to build an ipe flat bow, backed with white oak (or maybe ash...) and thought- why
no make a tri-lam bow. Then I thought- Why should I make it tri-lam?
So , I have some tri-lam questions:
1) What are the pros and cons of a tri-lam vs. a double lam bow?
2) Assuming I do want a tri-lam- are there any major design differences?
3) What are the characteristics of a good core wood?
I`ll add that I`m talking about wood in board form- no staves here...
Thanks in advance.
Dor
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http://www.primitivearcher.com/smf/index.php?topic=18845.5
http://www.primitivearcher.com/smf/index.php/topic,43255.0.html
http://www.primitivearcher.com/smf/index.php?topic=40725.0
https://www.primitivearcher.com/smf/index.php?topic=7282.10
http://www.primitivearcher.com/smf/index.php?topic=4766.0
http://www.primitivearcher.com/smf/index.php?topic=10892.0
https://www.primitivearcher.com/smf/index.php?topic=43520.0
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WOW!!
Thanks a lot Jorik! I tried to search to forum but for some reason didn`t got
all these results.
Dor
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The search engine on this forum is usually less than adequate for finding old topics here. You will have much more success searching google.
Type this into google search, no need for the quotation marks.
site:primitivearcher.com "whatever your searching for"
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When you search, try putting important words or phrases in quotation marks to make your search more specific.
For example if I search the phrase -> bow and arrow - then the search engine will search for any instances of the word bow and the word arrow separately. Any thread that has either of those words in it will show up in the results. And even words that contain those words within them will show up like bowyer or sparrow. I believe that the search engine automatically filters out words like "and" so you don't need to worry about them.
But if I search the phrase -> "bow and arrow" - then the search engine will return only results with that exact phrase, in that exact order, which would narrow it down quite a bit.
I find that without using quotation marks it is sometimes difficult to get meaningful results on a forum search.
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Thanks guys.
I still haven't found an answer to my third question- what do I look for in a core wood?
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Maple.
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Why make a trilam, cause you want to :laugh: maple is good but walnut will looks better
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I use compression strong core wood, like ipe, Osage, cherry, yellow heart, Purple Heart, etc. I believe the core is also experiencing mostly compressive forces. The lams I use are thin for the core, often 1/8".
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The best tri-lam ELB I ever built has a maple back, thin ipe core, and Osage belly. It shoots like a demon at 52#, and took very little set with a slight elliptical tiller. Plus, it looks great with the contrasting dark core.
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One reason is it's easy to add perry reflex (glued in reflex) with a trilam.
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Maple.
;D
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I use compression strong core wood, like ipe, Osage, cherry, yellow heart, Purple Heart, etc. I believe the core is also experiencing mostly compressive forces. The lams I use are thin for the core, often 1/8".
Isn't that just making the belly thicker, basically? Giving me more material to make a heavier bow or make the limbs thinner?
One more-
Is there any difference in tillering?
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I use compression strong core wood, like ipe, Osage, cherry, yellow heart, Purple Heart, etc. I believe the core is also experiencing mostly compressive forces. The lams I use are thin for the core, often 1/8".
Isn't that just making the belly thicker, basically? Giving me more material to make a heavier bow or make the limbs thinner?
One more-
Is there any difference in tillering?
No and no!
Cores experience sheer.
You need a not too dense wood, diffuse porous and has excellent gluing properties.
Maple is the way to go.
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Any other options besides maple and walnut?
Something that may improve performance
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One reason is it's easy to add perry reflex (glued in reflex) with a trilam.
Exactly the opposite! Perry reflex uses a thick laminate, that is basically too thick to use for heavily curved recurves or severe reflex. It will lose some shape due to spring back, but it will again gain some shape as you remove belly wood during tillering. To quote Dan Perry: "By reflexing a thicker than finished dimension bow before applying the backing." Read more about Perry reflex HERE. (http://leatherwall.bowsite.com/tf/lw/thread2.cfm?forum=23&threadid=188683&category=)
Toomany, your statement should be: "it's easy to add [more] reflex (glued in reflex) with a trilam."
Arachnid, many wood species will work as a core. Some folks use a pretty wood, just for looks. Then you could use purpleheart, bloodwood or bubinga. If you're looking to increase performance, then maple is probably best. But also walnut, cherry, vertical bamboo flooring, yew or juniper would work just fine.
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The best tri-lam ELB I ever built has a maple back, thin ipe core, and Osage belly. It shoots like a demon at 52#, and took very little set with a slight elliptical tiller. Plus, it looks great with the contrasting dark core.
Adam- Would you mind giving more detailed spec's on this bow build ? I'd like to give it a go. If you have a mind, pics would be great too. Thnx- Ron
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Why? I'll tell ya why....cus there SEXY!!!! 8) ....that's why :laugh:
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Any other options besides maple and walnut?
Something that may improve performance
I totally forgot to mention yew heartwood. It's a really great core. It's very light, strong in compression and glues very well. I've used it a few times, but not often because it's hard for me to get.
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Does the core need to be straight grained like the other lams? If not, with how many runoffs can I come by?
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Straight grain is obviously best, of course. But while the backing MUST be absolutely straight grained - no exception - the belly and core can have a few grain run offs. Stay away from knots and sudden wild grain patterns. I use laminations that do not meet the criteria for backings (or selfbows) as cores, since they are about the same thickness.
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Sometimes it's because it's all you have to work with. I generally avoid tri-lams if I can, they are more work than they are worth
I've heard the argument of using a dense core wood being better before and I don't believe it. The only time you might get any work out of the core is if the belly lam is very thin. If the backing and core together amount to 50% of the thickness of your bow then the core is unlikely to do any work. The only forces a core wood in such a situation may experience are shear forces and any wood that glues well will tolerate those. I've used BC, Maple, Ash and they all worked quite well. I know that the horn bowyers like Maple as a core and there is a reason for this, it glues extremely well and strong enough to resist high shear forces
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Sometimes it's because it's all you have to work with. I generally avoid tri-lams if I can, they are more work than they are worth
I've heard the argument of using a dense core wood being better before and I don't believe it. The only time you might get any work out of the core is if the belly lam is very thin. If the backing and core together amount to 50% of the thickness of your bow then the core is unlikely to do any work. The only forces a core wood in such a situation may experience are shear forces and any wood that glues well will tolerate those. I've used BC, Maple, Ash and they all worked quite well. I know that the horn bowyers like Maple as a core and there is a reason for this, it glues extremely well and strong enough to resist high shear forces
Rubbish. Gluing 3 lams in no more work than 2. If I'm cutting and sanding lams anyway, it's no more work, and gluing them takes the same amount of time.
Of course the core lam is going to be doing some work. Resistance to shear is still of benefit. I do agree that lighter woods are good for cores, but they still need to be strong in compression. Yew or cherry is probably the best I've used. However, I save the maple for the backing, as it's superior in tension.
As heat treating is your 'speciality' Marc, tri-lam ELBs are mine. I've stopped counting how many I've made, and in my experience, a tri-lam ELB with a harder, compression strong core wood is superior. As long as the core lam is thin, like <1/8". Bows made like this take less set and shoot faster in my experience. Believe me, I've experimented. I've found a whitewood backing, like maple or ash or hickory, with a core of maple, only makes a thicker backing. Adding a compression strong belly, which ends up being thinner, will make a bow which will take more set. Similar, I believe, as having a yew selfbow with too much sapwood.
I do agree with less is more. I can make more bows using a tri-lam style, because I need less of each type of wood.
Making a horn bellied, sinew backed horsebow is NOT the same as a tri-lam ELB. With a horsebow, I do agree that maple is great, but not for an ELB.
There was a post here not long ago... I think it was toomanyknots. He made a tri-lam, and used bloodwood (I think) as the core, and it chrysalled. It was clear and easy to see. I've never seen chrysalles or frets on the back of a bow. This is just more evidence to me, that the core is experiencing mostly compressive forces. The bow didn't fail in tension, but in compression, and in the core.
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Sometimes it's because it's all you have to work with. I generally avoid tri-lams if I can, they are more work than they are worth
I've heard the argument of using a dense core wood being better before and I don't believe it. The only time you might get any work out of the core is if the belly lam is very thin. If the backing and core together amount to 50% of the thickness of your bow then the core is unlikely to do any work. The only forces a core wood in such a situation may experience are shear forces and any wood that glues well will tolerate those. I've used BC, Maple, Ash and they all worked quite well. I know that the horn bowyers like Maple as a core and there is a reason for this, it glues extremely well and strong enough to resist high shear forces
Rubbish. Gluing 3 lams in no more work than 2. If I'm cutting and sanding lams anyway, it's no more work, and gluing them takes the same amount of time.
Of course the core lam is going to be doing some work. Any wood in a bow is going to be doing something. I do agree that lighter woods are good for cores, but they still need to be strong in compression. Yew, osage, ipe, etc., all make great core wood. I save the maple for the backing, as it's superior in tension.
As heat treating is your 'speciality' Marc, tri-lam ELBs are mine. I've stopped counting how many I've made, and in my experience, a tri-lam ELB with a harder, compression strong core wood is superior. As long as the core lam is thin, like <1/8". Bows made like this take less set and shoot faster in my experience. Believe me, I've experimented. I've found a whitewood backing, like maple or ash or hickory, with a core of maple, only makes a thicker backing. With a compression strong belly, which ends up being thinner, a bow like this will take more set.
No more work? Right. Everybody knows that cutting 3 lams is the same amount of work as cutting 2 and then spreading glue on 4 surfaces as opposed to 2 is the same amount of work. Whatever ::)
If the core is that thin then it is not working in compression, it may be working in tension though. If the bow has less set then it will shoot harder anyway.
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It was padauk (which in my opinion is very brittle and just sucks all around as a bow wood). I do have to respectfully disagree that maple does not work as a core wood in an elb, I use it often and it is my favorite corewood, I use it on target weight and warbows alike. Looks pretty nice sandwiched between an ipe belly and a boo backing too. I use yellow heart for cores too, I like it a lot for cores. I find it is pretty weak in compression though and chrysals easy as a belly wood (or at least my stock is). First trilam I did with it as a belly I got some huge chrysals. I know of you guys Adam and Mark have used it though, plus I see some UK bowyers using it as a belly wood, so I don't know if mine just sucks, or I suck, or what? :) Something is this situation sucks, ;D. Didn't Jaro make a bow out of it too?
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The problem is with using a white-wood backing and a white-wood core. If you use a Bamboo backing with that white-wood core then the results are quite different.
Now I know that the dense tropical woods can, can being the operative word here, work extremely well as backings, almost as well as Bamboo. The only problem is they are generally to brittle and fail. Putting a high density wood, such as Ipe, under the backing increases the overall tension strength of the backing while giving support to the Ipe, sort of like putting rawhide over a questionable bow's back.
I have a bit of high density Bubinga which is a bit low in elasticity so it does chrysal when stressed too much, in compression. It is a very straight grain board so as an experiment I decided to try it as a backing, in an RD design, with Yellowheart (Satinwood) as the belly wood. The bow kept a great deal of the glued in reflex while tillering and the backing behaved much like a Bamboo backing would, up until it failed. The bow was not under built but at around 24" it exploded ending up in several pieces scattered around my shop. Probably if I had glued on a very thin Maple backing the bow would have survived
P.S. The Yellowheart I have is quite nice and works well as a belly wood.
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I was just wondering something Marc... have you ever built a classic tri-lam ELB? I've searched your website, and this forum, and I can't find one. Not one. Not reflexed, or anything else... just a straight up tri-lam ELB. Deep rounded belly, follows the 5/8 rule more or less, at least 72" long, slight elliptical tiller... you know.
I was also wondering something else... do you think it's possible for one person to be an expert on all aspects of bow building? Even if it's a design or type of bow they've never made?
I don't offer any advice about heat treating, horsebows, sinew backing, or a whole raft of other subjects because I've never done it. Is it appropriate to offer advice on something I have zero first hand experience with?
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The term "classic tri-lam" combined with the 5/8 rule are ridiculous concepts.
The longbow history is nothing to do with those things and I'm surprised it has ever come to that.
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The 5/8 rule was implemented to prevent people from showing up to a BLBS shoot with a flat bow.
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The real reason is that they don't want people showing that other designs work better and destroying the longbow myth.
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The real reason is that they don't want people showing that other designs work better and destroying the longbow myth.
Ha!!!!!
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The real reason is that they don't want people showing that other designs work better and destroying the longbow myth.
LOL! I can't dispute that! However, I think the BLBS is looking to preserve a very specific type of bow, which is what they call an ELB.
I think the EWBS is similar. They have some very specific criteria to limit the type of bow they're using, to preserve a specific type of archery.
But, I fear this thread is straying dangerously off topic!
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The real reason is that they don't want people showing that other designs work better and destroying the longbow myth.
Love you pat:-)))
On topic: Bamboo flooring works well as core. I dont subscribe to the idea that core wood should be dense or compression strong...never seen a tri-lam collaps due to core failure (extension or compression). I also dont think there is anything gained using 3 instead of 2 lams if its a simple glue up, maybe with some reflex added. Hell while were at it....I dont think there is anything gained making lam bows when you can make a self bow (can we call it a "selfie"?);-)
Cheers
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The only reason I make a tri-lam is to use less belly wood - good clean yew slats are hard to come by.
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The real reason is that they don't want people showing that other designs work better and destroying the longbow myth.
You have two statements there.
1. Other designs work better.
Yes, in a modern context, but not for killing armoured foe at 200 yards. This is why the longbow evolved into the Victorian style target bow and the modern laminate longbow. Ultimately it was redesigned by Clarence N Hickman becoming more rectangular in section, the American longbow. http://www.archeryhalloffame.com/Hickman.html (http://www.archeryhalloffame.com/Hickman.html) He then went on to design the modern take down target recurve. He did that because he has lost some fingers in a rocketry accident and couldn't pull the necessary draw weights of the time. He needed a more efficient bow to enable him to compete.
2. There is no myth that the longbow / Warbow performed it's task admirably. The only slight myth is that it was all about the bow... it was just as much about poor French organisation.
It is ironic that in my youth most of the "how to make a 'longbow' " literature I could read was of American origin and based on the American version of the English longbow using woods like Osage that no timber merchant in the UK had ever heard of!
The rise of the internet and forums like this has ensured that the huge variety of bow types are there to be enjoyed.
To show I have no Longbow bias, I usually shoot a Yew Neolithic style bow :laugh:
Del
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The only reason I make a tri-lam is to use less belly wood - good clean yew slats are hard to come by.
That's a good reason too. When belly wood is expensive (like ipe) it can save money substantially. I was forced to buy some 1" thick ipe recently opposed to the 3/4" I prefer and resawed a good amount of it into 1/2" or so belly laminates which will hopefully make some nice lighter weight trilams.
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I was just wondering something Marc... have you ever built a classic tri-lam ELB? I've searched your website, and this forum, and I can't find one. Not one. Not reflexed, or anything else... just a straight up tri-lam ELB. Deep rounded belly, follows the 5/8 rule more or less, at least 72" long, slight elliptical tiller... you know.
I was also wondering something else... do you think it's possible for one person to be an expert on all aspects of bow building? Even if it's a design or type of bow they've never made?
I don't offer any advice about heat treating, horsebows, sinew backing, or a whole raft of other subjects because I've never done it. Is it appropriate to offer advice on something I have zero first hand experience with?
I guess you just haven't searched hard enough then
Bamboo backed Ash core and Ipe belly pulling about 90# @ 31" built about 3 years ago. It lost very little of the glued in reflex.
(http://img.photobucket.com/albums/v355/Marc-St-Louis/IPE%20Composite%20Bows/BBIPE%203%20Lam%20Warbow/Braced.jpg)
There's another I built several years before that but those pictures might be somewhat harder to come by and I don't have the bow anymore. It was Ash backed with BC core and Bubinga belly and pulled about 55# @ 29". It lost all of the glued in reflex and took a bit of set, about what you would expect from a bow.
No, one cannot know everything and I have never claimed to but I do know a fair bit about a large number of different styles of bows, including static recurves ;). Remember I have been at this for a lot longer than you have and this is not the first PA board.
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The only reason I make a tri-lam is to use less belly wood - good clean yew slats are hard to come by.
That's the only reason I would make another
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The real reason is that they don't want people showing that other designs work better and destroying the longbow myth.
You have two statements there.
1. Other designs work better.
Yes, in a modern context, but not for killing armoured foe at 200 yards. This is why the longbow evolved into the Victorian style target bow and the modern laminate longbow. Ultimately it was redesigned by Clarence N Hickman becoming more rectangular in section, the American longbow. http://www.archeryhalloffame.com/Hickman.html (http://www.archeryhalloffame.com/Hickman.html) He then went on to design the modern take down target recurve. He did that because he has lost some fingers in a rocketry accident and couldn't pull the necessary draw weights of the time. He needed a more efficient bow to enable him to compete.
2. There is no myth that the longbow / Warbow performed it's task admirably. The only slight myth is that it was all about the bow... it was just as much about poor French organisation.
It is ironic that in my youth most of the "how to make a 'longbow' " literature I could read was of American origin and based on the American version of the English longbow using woods like Osage that no timber merchant in the UK had ever heard of!
The rise of the internet and forums like this has ensured that the huge variety of bow types are there to be enjoyed.
To show I have no Longbow bias, I usually shoot a Yew Neolithic style bow :laugh:
Del
That's the part that's debateable.. Can a more complex selfbow be built that has better long range cast with heavy arrows be built that doesn't adhere to the 5/8 rule and string not touching the limbs at any point when strung?
I think so.
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The real reason is that they don't want people showing that other designs work better and destroying the longbow myth.
You have two statements there.
1. Other designs work better.
Yes, in a modern context, but not for killing armoured foe at 200 yards. This is why the longbow evolved into the Victorian style target bow and the modern laminate longbow. Ultimately it was redesigned by Clarence N Hickman becoming more rectangular in section, the American longbow. http://www.archeryhalloffame.com/Hickman.html (http://www.archeryhalloffame.com/Hickman.html) He then went on to design the modern take down target recurve. He did that because he has lost some fingers in a rocketry accident and couldn't pull the necessary draw weights of the time. He needed a more efficient bow to enable him to compete.
2. There is no myth that the longbow / Warbow performed it's task admirably. The only slight myth is that it was all about the bow... it was just as much about poor French organisation.
It is ironic that in my youth most of the "how to make a 'longbow' " literature I could read was of American origin and based on the American version of the English longbow using woods like Osage that no timber merchant in the UK had ever heard of!
The rise of the internet and forums like this has ensured that the huge variety of bow types are there to be enjoyed.
To show I have no Longbow bias, I usually shoot a Yew Neolithic style bow :laugh:
Del
That's the part that's debateable.. Can a more complex selfbow be built that has better long range cast with heavy arrows be built that doesn't adhere to the 5/8 rule and string not touching the limbs at any point when strung?
I think so.
Pat, do you mean like a flatbow? The flatbow would have to be a heavy draw weight, which means it would need to be close to as long as a warbow to distribute the stress. Maybe a smidge shorter would work due to the flat profile, but it couldn't reasonably be much shorter with a 100 lbs and over draw weight. And the wider the limbs get, the more shock you get at those lengths and weights with a flatbow design. I've made some pretty high draw weight flatbows out of hackberry. Hackberry takes better to handshock though being a lighter wood. Maybe yew is the same way. I would think supplying armies with flatbows would be inefficient though because of the design taking more wood, and maybe even more time to tiller. The presence of a non-working handle alone would cause more stress to the belly, limiting the life and efficiency of the bow off rip. I think the string not touching the limb shouldn't really be that huge of a deal though. I think you do get a nice string angle advantage which smooths out the draw if you flip your elb tips just a bit. I wouldn't really see it being too much time to just boil a big batch of limb tips and flip em on some forms, I wouldn't see that being that all time consuming. It really only takes 10 minutes or so for it to cool and keep the bend so you can take it out of the form (as long as you don't bend it for a good while, I wait 24 hours). So you could do a big batch with just a couple forms? I get it though they don't want people shooting some fiberglass recurve or something though, :).
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Of course it can!
You can't really compare a self bow with a laminate using boo and exotics, but, at the end of the day, it's the skill of the bowyer that counts.
It's just that a warbow is relatively more efficient when throwing heavy arrows than it is when throwing target ones.
I think you need to spell out what the 'myth' is, else I can't debate it... mind... I'm not sure I want to anyway, the history speaks for itself.
IMO The biggest Myth is that Warbows have a D profile... I don't think any of the MR Bows have what most people would think of as a D section.
Next!
Del
@ Toomany... nice post :)
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I meant purely a selfbow that has been tweaked to get the max performance. The myth is that the longbow is the ultimate bow for the type of warfare it was used in but the truth is that it was really the only one.
Now if the French had bothered to gather all their Laburnum and make heavy recurved flatbows, the picture might have been entirely different. ;)
It is not much more difficult to make recurved selfbows of extremely high draw weight in shorter lengths. Those are the bows that the WBS don't want showing up.
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I wouldn't know .. I shun "societies" where possible.
Anyhow do such bows have the long draw length? (It's not all about draw weight). And did they exist at the time?
Del
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It is not much more difficult to make recurved selfbows of extremely high draw weight in shorter lengths.
I think they are. Especially when the tips don't line up on a recurve, and the string wants to come off the recurve. With a longbow, if the tips don't line up and the bow wants to twist, you can scrape one side/weaken one side of the bow until it corrects itself. Tools at the time were probably easier to work on a longbow with a round or round-ish cross section opposed to a flatbow. I think scrapers are easier to use nowadays on a longbow verses a flatbow. Supposedly though, to my uneducated understanding, the manchu used high draw weight recurves just like you are talking about in war, effectively enough to conquer China! Although they would horn bow construction.
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The real reason is that they don't want people showing that other designs work better and destroying the longbow myth.
You have two statements there.
1. Other designs work better.
Yes, in a modern context, but not for killing armoured foe at 200 yards. This is why the longbow evolved into the Victorian style target bow and the modern laminate longbow. Ultimately it was redesigned by Clarence N Hickman becoming more rectangular in section, the American longbow. http://www.archeryhalloffame.com/Hickman.html (http://www.archeryhalloffame.com/Hickman.html) He then went on to design the modern take down target recurve. He did that because he has lost some fingers in a rocketry accident and couldn't pull the necessary draw weights of the time. He needed a more efficient bow to enable him to compete.
2. There is no myth that the longbow / Warbow performed it's task admirably. The only slight myth is that it was all about the bow... it was just as much about poor French organisation.
It is ironic that in my youth most of the "how to make a 'longbow' " literature I could read was of American origin and based on the American version of the English longbow using woods like Osage that no timber merchant in the UK had ever heard of!
The rise of the internet and forums like this has ensured that the huge variety of bow types are there to be enjoyed.
To show I have no Longbow bias, I usually shoot a Yew Neolithic style bow :laugh:
Del
That's the part that's debateable.. Can a more complex selfbow be built that has better long range cast with heavy arrows be built that doesn't adhere to the 5/8 rule and string not touching the limbs at any point when strung?
I think so.
Pat, do you mean like a flatbow? The flatbow would have to be a heavy draw weight, which means it would need to be close to as long as a warbow to distribute the stress. Maybe a smidge shorter would work due to the flat profile, but it couldn't reasonably be much shorter with a 100 lbs and over draw weight. And the wider the limbs get, the more shock you get at those lengths and weights with a flatbow design. I've made some pretty high draw weight flatbows out of hackberry. Hackberry takes better to handshock though being a lighter wood. Maybe yew is the same way. I would think supplying armies with flatbows would be inefficient though because of the design taking more wood, and maybe even more time to tiller. The presence of a non-working handle alone would cause more stress to the belly, limiting the life and efficiency of the bow off rip. I think the string not touching the limb shouldn't really be that huge of a deal though. I think you do get a nice string angle advantage which smooths out the draw if you flip your elb tips just a bit. I wouldn't really see it being too much time to just boil a big batch of limb tips and flip em on some forms, I wouldn't see that being that all time consuming. It really only takes 10 minutes or so for it to cool and keep the bend so you can take it out of the form (as long as you don't bend it for a good while, I wait 24 hours). So you could do a big batch with just a couple forms? I get it though they don't want people shooting some fiberglass recurve or something though, :).
Well said, Mr Knots.
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Of course it can!
You can't really compare a self bow with a laminate using boo and exotics, but, at the end of the day, it's the skill of the bowyer that counts.
It's just that a warbow is relatively more efficient when throwing heavy arrows than it is when throwing target ones.
I think you need to spell out what the 'myth' is, else I can't debate it... mind... I'm not sure I want to anyway, the history speaks for itself.
IMO The biggest Myth is that Warbows have a D profile... I don't think any of the MR Bows have what most people would think of as a D section.
Next!
Del
@ Toomany... nice post :)
The majority of the MR bows I saw had a D xsection. :o Certainly, some of the heavier bows where a bit more square in xsection (or slab sided, as some people refer to them as), but certainly a rounded high crowned belly, with a flatter back.
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They are more round in section or like an inflated square some are a bit like the letter "D" in this font (but with the sharp corners heavilly rounded so as to be almost circular) None are like the "high arched" D of a Victorian bow.
I've handled them and studied the cross section illustrations in Weapons of Warre.
If you disagree, we'll just have to differ on the point.
Which of the ones in the attachment do you call D section?
Del
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All the ones on the right appear as a D xsection to my eyes. Certainly round, but the back appears plainly in all the images, and can be determined by the fact that it's flatter.
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One thing I don't understand... how does all this advocating for a 'lighter' core wood apply to the mass principle??
I follow the mass principal, more or less. It makes sense. It takes less of a more dense material to make the same bow... design accordingly. So, if I'm making ELBs, regardless of material (including the core), and all else is equal, I want the bows to weigh the same when they're finished. Someone please explain. Marc?
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The only reason I make a tri-lam is to use less belly wood - good clean yew slats are hard to come by.
Yep, or wanting to make a PERRY.
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One thing I don't understand... how does all this advocating for a 'lighter' core wood apply to the mass principle??
I follow the mass principal, more or less. It makes sense. It takes less of a more dense material to make the same bow... design accordingly. So, if I'm making ELBs, regardless of material (including the core), and all else is equal, I want the bows to weigh the same when they're finished. Someone please explain. Marc?
I remember reading somewhere I think where Steve said something along the lines of the mass theory needing to be tweeked a bit for longbows. Please don't quote me on that, if anyone knows what I am talking about or if I am wrong please correct me. Edit: Wait a min, I found it:
"ADB, the mass theory was more based on hunting weight bows, I have found on circular tillered bows it starts to wander off to the high side after about 70#, also as discussed in the book certain woods will tend to come in lighter, yew and cherry for instance. Your bow comes in at around 829 grams not allowing for yew wood if it is circular tillered. If I were to rewrite that chapter for heavier bows it would come in about 10% lighter. Tillering the bow for low set as you achieved will always overide predicted mass which is more of an estimated mass to arrive at close dementions anyway."
I think the woods that come in lighter would probably have better performance. I know using dense cores with dense bellys and dense backings does not give me the best performance, no matter how much glued in reflex they have or how careful I tiller them. And then there is beam theory, where by the result of having one tensile strain, and one compressive strain, there has to exist a neutral axis by default that is under no strain. If you taper your cores to reflect this neutral axis, in theory (which yes is incredibley different when comparing a steel beam to a bamboo/osage etc bow!, :) ) but still, in "theory" you should be able to fill this neutral axis with anything you want, given that it can take the sheer. So, in theroy, why not fill it with the least dense material that can take it? Although tapering does take a while on my end, I am using a 4 x 36 belt sander, which takes a while. I cut my lams 1/4 or more and taper the tips on the sander to less than 1/8", maybe 3/32". It is nice to just be able to glue up a bow with a 1/8" core without having to taper. If I was gluing up like 10 in a session, I would want to do 1/8" cores probably.
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All the ones on the right appear as a D xsection to my eyes. Certainly round, but the back appears plainly in all the images, and can be determined by the fact that it's flatter.
Oh? Well there you go.
Yeah, the back can be "determined" but it is not glaringly obvious in any of 'em, as to my eye they are all fairly symmetrical about a horizontal axis, with the back being only very slightly flatter than the belly.
In fact the one lower right is flatter on it's right side than the back.
I'd have described them as being more like an inflated square or having slightly rounded bellies not at all like the Victorian D.
Obviously we have a different interpretation of the term and concept of D shaped.
I think I'll quit and go hide in my secret cat nest :laugh:
Del
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The bow on the right could be have the profile flipped the other way and be perfectly feasible as a crowned back and flatter belly.
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One thing I don't understand... how does all this advocating for a 'lighter' core wood apply to the mass principle??
I follow the mass principal, more or less. It makes sense. It takes less of a more dense material to make the same bow... design accordingly. So, if I'm making ELBs, regardless of material (including the core), and all else is equal, I want the bows to weigh the same when they're finished. Someone please explain. Marc?
I remember reading somewhere I think where Steve said something along the lines of the mass theory needing to be tweeked a bit for longbows. Please don't quote me on that, if anyone knows what I am talking about or if I am wrong please correct me. Edit: Wait a min, I found it:
"ADB, the mass theory was more based on hunting weight bows, I have found on circular tillered bows it starts to wander off to the high side after about 70#, also as discussed in the book certain woods will tend to come in lighter, yew and cherry for instance. Your bow comes in at around 829 grams not allowing for yew wood if it is circular tillered. If I were to rewrite that chapter for heavier bows it would come in about 10% lighter. Tillering the bow for low set as you achieved will always overide predicted mass which is more of an estimated mass to arrive at close dementions anyway."
I think the woods that come in lighter would probably have better performance. I know using dense cores with dense bellys and dense backings does not give me the best performance, no matter how much glued in reflex they have or how careful I tiller them. And then there is beam theory, where by the result of having one tensile strain, and one compressive strain, there has to exist a neutral axis by default that is under no strain. If you taper your cores to reflect this neutral axis, in theory (which yes is incredibley different when comparing a steel beam to a bamboo/osage etc bow!, :) ) but still, in "theory" you should be able to fill this neutral axis with anything you want, given that it can take the sheer. So, in theroy, why not fill it with the least dense material that can take it? Although tapering does take a while on my end, I am using a 4 x 36 belt sander, which takes a while. I cut my lams 1/4 or more and taper the tips on the sander to less than 1/8", maybe 3/32". It is nice to just be able to glue up a bow with a 1/8" core without having to taper. If I was gluing up like 10 in a session, I would want to do 1/8" cores probably.
I remember Steve talking about this before, and him mentioning it needing tweaking for warbow weight (70+#) ELB type bows. But, I'm talking target/hunting weight at around 50#. I just don't think that the core matters as much as some people think it does, especially if bows of different material are designed and tillered to have the same limb mass (in other words, following the mass principle). I think I'll continue to make tri-lam ELBs with compression strong core wood, and be very happy with them, and you'll likely continue to use maple as your favourite, and we'll both be very happy bow makers!
I think the only way to truly test this, and reveal any meaningful result, would be to make 2 ELBs... similar design, similar draw weight, same tiller and set, both with identical mass, and one made with a lighter tension strong core (like maple) and the other with a compression strong core like osage or ipe, and then wring them out for performance... cast, arrow speed at various arrow weights. I don't know, but I would guess their performance would be so close, you couldn't tell any difference.
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The bow on the right could be have the profile flipped the other way and be perfectly feasible as a crowned back and flatter belly.
Sure, it could be... but it's not.
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Going back to arachnid’s questions on why to make a tri-lam since I have no experience with ELBs ;)
….
> 1) What are the pros and cons of a tri-lam vs. a double lam bow?
Gordon nailed the prime advantage of tri-lams over backed bows- they use much less expensive (or difficult to obtain) belly wood. Some other advantages:
1. The performance advantage is debatable, but I tend to think a tri-lam yields a faster bow than a backed bow. Methinks this is due to a lighter bow when lighter core wood is used and, it’s said…. there’s another glue line for prestressing. Whether a tri-lam is worth the additional effort in construction is even more debatable.
2. One can use the same form for glueing and the same bow profile and length and get wildly different bows by changing the taper and/or thickness of the lams, changing the length of the power lam or tip wedges. One can in theory get a bow that needs no or very little tillering- something I’ve not accomplished >:(
3. A minor point but, compared with plain backed bows, they have less spring-back (or reflex loss) once removed from the form after glueing- especially if the belly of a backed bow isn’t pre-tillered.
4. Some think they look cooler or whatever than a backed bow.
Cons: More labor intensive. A thickness sander is just about a necessity. Less belly wood for tillering, More glue lines to fail if your glueing is sub-par (use Urac or it's replacement).
2) Assuming I do want a tri-lam- are there any major design differences?
The major design difference is the core. Of lessor import- tip wedges and the power lam.
> 3) What are the characteristics of a good core wood?
Lots of folks suggest maple as a core wood. I agree. I’ve not used it but elm is probably good also. Elm and maple are what are used for inner lams in lots of bows surfaced with that unprimitive stuff we aren't supposed to mention herein. Heck, foam is even being used (albeit expensive hi-tech foam). Which brings up a SWAG: Methinks the core should be light and shear strong. I tend to view a bow limb as a beam wherein most of the stresses are in the extreme fibers- i.e. the surfaces of the back and belly. The catches are that a tri-lam’s limb is a composite beam and is prestressed when there’s reflex glued in or is otherwise “Perryed”. www.bio.vu.nl/thb/users/kooi/#pijl has some interesting but mind-numbing stuff on bow mechanics and composite bows.
c.d.
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3. A minor point but, compared with plain backed bows, they have less spring-back (or reflex loss) once removed from the form after glueing- especially if the belly of a backed bow isn’t pre-tillered.
This is a good point too. Perhaps they tend to hold reflex better after being tillered and shot as well? Never actually thought about that myself. Now that I think about it, it seems to be true on my end.
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This is just my opinion, and I have no evidence to back it up, but... if done correctly (with good glue joints), I believe 3 laminations are stronger than 2. Much the same way plywood is stronger than lumber (I know it's a different process with plywood). I think whatever shape you glue into a multi-lam bow, the more likely it is to maintain that shape, even after being stressed.
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One would think that a multi-lam (complex composite) bow would have better performance but the flight shooting records don't support this theory. The 50# simple composite record, a simple backed bow, stands at 326 yards. The record for a complex composite (multi-lam bow) stands at 321 yards.
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Interesting. Any details on the construction and materials of these bows?
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Well, I`m glad my questions opened this very interesting discussion.
I think I`ll go for a backed bow for now.
I have another question-
I`m planning to make a flat bow using the vintage projects dimensions (more or less).
I`m shooting for a 40#-45# DW and It`s going to be white oak/ash/maple backed ipe (depending what I`ll find).
They are using lemonwood on that build and I was wondering if these dimensions
will suit my target DW while using ipe belly OR do I need some modifications?
Thx
Dor
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With a dense tough wood like ipe, typically you will need less wood.
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I concur with the benefits mentioned so far. Another benefit I've found with tri-lams is that since the pieces are thinner, they can be bent into more drastic shapes than a two piece backed bow... i.e. more severe deflex, reflex, even full recurves are easily glued-in that are impossible to accomplish in blanks with thicker pieces.
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I know it doesn`t take a lot of ipe to make a bow.
I just don`t know how stiff lemonwood is (we don`t have it around here...)
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"Stiffness" appears to be related to specific gravity of the material to a high degree. If your piece of ipé is about 20% more dense than the average piece of lemonwood, I would make your bow about 20% narrower than the lemonwood equivalent.
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Thanks jorik.
Should I make it thinner also?
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The thickness taper will be determined by the tiller. However, if you want around 40-50# and you're backing the ipe, I start with a 3/8" thick belly slat for a pyramid bow, and make it from 1.25" to 1.5" wide at the fades, tapering to 1/2" or less tips.
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The thickness taper will be determined by the tiller. However, if you want around 40-50# and you're backing the ipe, I start with a 3/8" thick belly slat for a pyramid bow, and make it from 1.25" to 1.5" wide at the fades, tapering to 1/2" or less tips.
And if I don`t want a pyramid, but the width taper to start at the last 20" (from 1.5" to 3/8") ? Should I start with
3/8" thick belly? Will it get me close to my target DW (or is it too much)?
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I would.
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Good to know.
Thanks a lot guys.
Dor
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Good to know.
Thanks a lot guys.
Dor
I agree! Info appreciated from all! :) Thank you for the ipe dimensions Adam, will use those as I don't make too many ipe flatbows.
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I think the problem with multi-lam bows, as it pertains to performance, is that the glue line on the multiple laminations slow the bow down through hysteresis which negates any advantages you may get through mass reduction.
Personally I've never found the need to make an Ipe bow any more than 1 1/4" wide even for bows more than 60#. Bows approaching 100# on the other hand would need 1 3/8" to 1 1/2" in width.
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So, the glue line will change the hysteresis of the wood? How? The gluing happens at the molecular level. A good glue line really isn't a line at all. Just because two different woods are glued together, doesn't mean the hysteresis of each type of wood will magically change. The entire hysteresis of the total limb may change depending on the combination of woods used. Sounds to me like you're guessing.
Yes, it doesn't take much ipe to make a bow. But, we were talking flatbows here (I was, anyway) when I offered dimensions. One of my bread & butter bows is a backed ipe flatbow. I easily make more backed ipe flatbows than any other type (and recurves, as well). It just works out for me... easy access to good quality reasonably priced ipe is a no-brainer.
66" ntn for longer draws and heavier weights, and down to 60" ntn for shorter draws and lighter weights. I make them all with an 8" long handle/riser with multilams to a total thickness in the grip of 1.25". They're pyramid bows, 1.5" wide at the fades, tapering to 1/2" or 3/8" tips. For bows up to 50#, I use 3/8" thick belly lam slats, with a 3/16" backing. Above 50#, I go with 1/2" thick belly slats and 1/4" backing. I've made bows with this design from 25#-75# with no failures. Dead simple, foolproof design and material.
For ELBs, even warbows >100#, I would never go more than 1.25" at the handle with ipe.