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
