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Making fast bows

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willie:

--- Quote from: lonbow on September 22, 2025, 07:30:45 pm ---: The grip area should bend as little as possible, but as much as necessary.

--- End quote ---

good observations,
are the mary rose bows a good example? I would think they were tillered for maximum cast which would also be "fastest"
could you post pics of different examples at full draw?

sleek:

--- Quote from: lonbow on September 22, 2025, 07:30:45 pm ---Over 90 percent of the bows I build are ELBs. I like that this design appears very simple at first glance, but the devil's in the detail. I would argue that it is relatively easy for an inexperienced beginner to implement the basic design of the longbow, but it requires more experience compared to a flatbow to build an ELB with high to maximum efficiency. The reasons are as follows: due to its design, the flatbow is stiff at the grip, which automatically reduces limb vibration. In addition, the average flatbow is shorter than a longbow, which means that it is not quite as important to distribute the limb mass correctly (i.e., close to the grip).

However, this does not mean that a longbow cannot be built to be just as efficient as an excellent flatbow. Here are a few observations I have made: The grip area should bend as little as possible, but as much as necessary. A grip that bends too much (one of the most common mistakes) reduces efficiency, as both the limb vibration and the moving limb mass are unnecessarily increased. On the other hand, a grip that is too stiff puts too much strain on the middle and outer limbs.
 
A shorter longbow must bend relatively more at the handle at a given draw weight in order not to overstrain the mid and outer limbs. The more draw weight a longbow has at a given length and limb width, the more the grip must bend. A longbow made of very pressure resistant woods such as yew, osage, and laburnum can be tillered more elliptically at a given length and draw weight than a longbow made of white woods. With white woods, I make sure that the set is distributed over the entire length, while with woods like osage, yew and laburnum,  it's okay if the set is only present in the mid and outer limbs, which makes the bow more efficient. The maximum acceptable amount of set is about 1 1/4 inches.
 
Another common mistake I often see on longbows is that the limb tips are too stiff. This unnecessarily increases the moving limb mass and, in my opinion, puts too much strain on the mid limbs. Unlike flatbows, the limbs of longbows are allowed to bend all the way to the tips. Arrow speeds of over 170 fps at 10 gpp are entirely achievable when these tiller rules are taken into account.


I have also been building laminated English longbows for about a year or so. I noticed that the choice of glue used plays a significant role and has a major impact on arrow speed. In my experience, a bow glued with Titebond III retains less reflex and shoots about 10 fps slower than a bow glued with epoxy resin or good fish glue. I suspect that Titebond III yields more under shear forces (i.e., is more chewing gum-like) than epoxy resin or fish glue. A well-built English longbow made of two or three lams glued with the latter two glues can achieve arrow speeds of over 180 fps.


@sleek: I would like to ask you a little more about your approach to heat treating flight bows. At what draw lengths do you perform the heat treatments during tillering? Are there woods that you heat treat stronger than other woods? How dark is the wood your heat treatments?

Thank You and cheers,
lonbow

--- End quote ---

I first focus on getting my tiller correct, and I take reading on the scale as I near my final draw weight, not draw length. I draw 26, and like to have my tiller perfect before I hit 15 inches. I like to have my projected draw weight to hit 26 by time im at 20 inches. Then I heat treat it and start the process over again. If Im gonna do a 50 pound bow, I dont hit 50 until the first and last time I hit my final draw length. This process keeps wood strain down. Many folks dont realize, just bracing your bow when its too heavy causes set and damage. There's no reason to brace and pull to 50 if you are gonna hit 50@15 and you pull 28. Ypu should hit your final draw weight and draw length at the same time.

Selfbowman:
I have found 9grains per inch of draw gives me better distance on 50 pound bows in broadhead head flight. Not because that the rules are 450grain.  My best shots have been with 462 grains. It might be that that’s the sweet spot of arrow weight vs bow weight on a fifty pound bow or better  distance with that particular bow design. I don’t have a shooting machine but after 150 Pyramid design bows with 1-1/2 reflex in the last 8-10” of the limb. This design has broke many flight records in fifty pound class and unlimited class. The English have gotten the English longbow rules oked to shoot synthetic strings vs all natural materials. I would like to see all primitive classes ok the synthetic strings in flight shooting. Jim Davis convinced years ago that the pyramid bows are the most efficient design. I built one English longbow from Osage years ago. I built it to the flight shooting rule design. It was full of shock and a dog. It was probably the builders fault!!!🤠🤠🤠

JW_Halverson:
Ok, that multiple heat treatment idea is stuck in my head like a piece of kale in my teeth in a critical job interview.

I have a theory working in my head that the belly needs to not just reach a critical temperature but also STAY AT THAT TEMP FOR A PERIOD OF TIME. Doing that all in one heat session would likely cause the heat to migrate too deeply and damage the tension strength of the back. But by doing it over several sessions one can get up to the critical temp again and again until it adds up to the point where the changes are complete. Or expressed as a formula, a matter of Time X Temperature.

Or am I overthinking this?

sleek:

--- Quote from: JW_Halverson on September 25, 2025, 12:17:01 pm ---Ok, that multiple heat treatment idea is stuck in my head like a piece of kale in my teeth in a critical job interview.

I have a theory working in my head that the belly needs to not just reach a critical temperature but also STAY AT THAT TEMP FOR A PERIOD OF TIME. Doing that all in one heat session would likely cause the heat to migrate too deeply and damage the tension strength of the back. But by doing it over several sessions one can get up to the critical temp again and again until it adds up to the point where the changes are complete. Or expressed as a formula, a matter of Time X Temperature.

Or am I overthinking this?

--- End quote ---

No, I think you are about right. Its not just getting it hot, it does require a specific time for a heat soak. Like treating metal with heat. I dont know all the science, but I know this works. My bows consistently beat the computer models Alan Case pits together for whats supposed to be possible. And Alan, for those who dont know, is probably one of the smartest guys out there who builds bows. He just broke Harry Drakes record for longest arrow shot, well over a mile. Alan and I are on and off discussing heat treat recently and are considering different tests to learn more.

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