Main Discussion Area > English Warbow
250 pounder attempt
markinengland:
Rudderbows,
I remain interested in how such a narrow bow will reach the weight you want. This might be possible just with Ipe/Boo or Ipe/Hickory but is it possible with Hickory/Hickory?
I don't claim much experience with heavy bows having made them up to 120lb or so but I have found that early high draw weight makes heavier bows harder to pull. A progressive build in weight can be managed better, with weight building in the last six inches or so of draw. A long straight bow helps, perhaps with a degree of set to help keep early draw weight low so you can get it past the "wall". This would perhaps rule out a perry reflex effect increasing the weight and also increasing the early draw weight.
Fancy answering this?
Mark in England
RyanY:
I haven't built any really heavy bows but I understand what you guys are saying about how this bow needs to be wider to even think about getting to this weight. Now if you try to make a bow this heavy from boo and ipe wouldn't those be the best materials to work with? I'm just thinking that since you don't want to make this bow too much wider that bamboo has enough tensile strength and ipe has enough compressive strength for this bow to be thicker? I don't have any experience with bbi bows but from what I hear bamboo is pretty much the strongest thing you're gonna back a bow with while ipe is equal in its compressive properties. I realize that there must be some flaw in my thinking since you guys haven't said much about just having a thicker cross section. I understand that hickory couldn't probably take the compressive forces of a bow this extreme but why not bbi?
markinengland:
Ryoon,
I reckon that ipe/boo at about 2 inches wide and somewhere over 80 inches long glued up straight should be a good start to get 200lb plus in as manageable a way as possible.
If it isn't to be drawn by a human but by a machine then it could be made less wide and some perry reflex glued in for sheer performance.
The draw force curve would be interesting to see if the bow is made.
Mark in England
rudderbows:
Mark, I fully intend on taking your advice to heart about width and Marlons advice about length. One issue I am concerned about is someone getting hurt. I do not want that to happen AT ALL. Bow stability is important. I think different materials will require different measurements. the thing that I can afford to do is experiment with the different materials on the crank. If it blows on the crank it will miss everyone including myself and employee and the shop Dogs because I am going to have a couple pieces of plywood set up on each side of the crank. . . haha;/. . Anyways I fully intend on making it a wider and longer. I also know that an Englsih style rounded belly can bend farther than a flat belly before breaking. My buddy Phil tried some experiments some time ago with this. He simply made flat bows and english style bows and decided to pull them on a pulley system untill they broke. He discovered that rounded bellied bows go 15% to 20% farther before snapping. Maybe thats why the English bowyers made them with rounded bellies. More stable perhaps.
--- Quote from: markinengland on December 13, 2009, 04:23:04 am ---Rudderbows,
I remain interested in how such a narrow bow will reach the weight you want. This might be possible just with Ipe/Boo or Ipe/Hickory but is it possible with Hickory/Hickory?
I don't claim much experience with heavy bows having made them up to 120lb or so but I have found that early high draw weight makes heavier bows harder to pull. A progressive build in weight can be managed better, with weight building in the last six inches or so of draw. A long straight bow helps, perhaps with a degree of set to help keep early draw weight low so you can get it past the "wall". This would perhaps rule out a perry reflex effect increasing the weight and also increasing the early draw weight.
Fancy answering this?
Mark in England
--- End quote ---
markinengland:
One route to this might be to make an 84 inch 125lb bow. From this you can almost just double the width to get what would be needed for 250lbs. Initially doubled up it would be somewhat over strength but basically in the right ball park so all you need to do is reduce the depth a little which will make it even safer than the 125lb bow was. Experimenting at 125lbs might be a little more manageable and less risky but should give a really useful steer on what is needed for the heavier bow.
Regards,
Mark in England
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