sinew backed bow help

[Jjpso]

hello everyone! this winter I plan to do my first sinew backed bow! It will be a wytch elm bow, with 4 inches stiff handle and 2-3 inches each fade, and short static recurves. My question is, how short (in length) can one go using sinew? And how many layers of sinew should I put? My draw length is 26" max I need a good day and I am looking to get around 55 pounds... thanks in advance, and regards from Portugal....

[bassman]

Wych is one of the best Elms for making a bow. I just posted a 50 inch self bow made from American Elm. 50 lbs. at 25.5 inch draw ,that shot a 425 gr.arrow at 160 fps. 4 inch stiff handle with 2 inch fades. So judging from that if you like a little longer bow 56 to 58 inches.If you like a shorter bow 52 to 54 inches long.JMO, and others may vary. Keep the sinew under heavy strain to get the most out of it by using reflex.

[bownarra]

60 inch.

[bradsmith2010]

I would say 54 would be fine,, but longer is ok too
three or four layers depending on how thick they are,,
if you weigh the sinew before applying,, it will give you a starting point for next time,, if you want more or less depending on the desired results,,
for example,, if the performance is poor,, maybe too much sinew was used,,
if the bow blows up,, maybe to little,,make adjustment for next bow....

[maitus]

I think elm belly cant resist more than three lyers of sinew.

[PatM]

I think elm belly cant resist more than three lyers of sinew.

Huh?

[bradsmith2010]

 

[SLIMBOB]

My thought was also somewhere around 54 inches being very doable.

[loefflerchuck]

Elm is a unique wood that is stronger in tension than compression. That means it makes a great self bow with a round back and flat belly but it's not a good wood to use with a sinew backing.  You can't make the bow shorter because of the sinew backing. The belly will fail.

[PatM]

Whoa now , Chuck.  That's not really true.  Elm makes a great sinew backed bow, even if  not heat treated.  It's exceptional when heat treated.

[Marc St Louis]

Elm is a unique wood that is stronger in tension than compression. That means it makes a great self bow with a round back and flat belly but it's not a good wood to use with a sinew backing.  You can't make the bow shorter because of the sinew backing. The belly will fail.

All depends on the species of Elm.  I've had a sinew backed Elm bow chrysal badly, but then anything I made with that tree chrysaled, and I have had some that shine

As to the question.  You could go with 54" but then you would have to deal with string angle.  I have always used 4 layers of sinew on any bow I backed.

[loefflerchuck]

Marc and Pat, Do you think you could make a faster sinew backed elm bow than self elm bow? Good point about species. Around here we only have invasive Siberian elm and the young trees(round back) make a exceptional bow. Every stave I have used has taken reflex on drying and with a pyramid design kept that reflex through tillering and shooting. One of the fastest  self bow woods I have used. I just don't think i could take advantage of sinew to tweak that design more without overworking the wood and to the point of breaking or losing cast. I could be wrong but I have heard all elms are stronger in tension than compression.

[PatM]

Siberian Elm is a bit of an outlier for sure.  American Elm and Rock Elm or similar species are a bit different.

 Technically almost every wood is stronger in tension than compression  The failure just manifests much differently.

 The sinew versus unsinewed is a good question and I think that would depend on design, wood variability and area used.
 
  I you heat treat the balance between tension strength and compression resistance changes and sinew starts to be a safety margin, even for a wood like elm with its tension strength.

[bradsmith2010]

A longer self bow would shoot close to the sinew shorter sinew bow,,.I think a shorter self bow might not shoot as hard as the short sinew bow,..the sinew bow being able to hold reflex,,.a self bow might take some set at the shorter length,..

[loefflerchuck]

Thanks Pat. Out here many of our native bow woods are stronger in compression(choke cherry and juniper). Juniper is the most plentiful bow wood and along with incense cedar probably the best sinew backed wood. When I get my hands on good hardwood from the east I don't consider backing, except sometimes woods that take a lot of compression like ash and osage.