Mulberry -- SNAAAAAAAAAAAP!

[adb]

Yikes... blew a chunk right out. Definitely a tension failure. Hope you didn't get any flying bits in the head!

[DarkSoul]

Waiting three days for the wood to regain moisture again and reach EMC after heat treating is sufficient. Especially with those thin limbs, the wood will have reached EMC by the time you started tillering. BUT...EMC is not the same as a healthy moisture content! The kind of tension break displayed does look like a break from brittle wood and/or wood that has a moisture content that is too low. Just the fact that this mulberry probably reached EMC again after heat treating, doesn't mean it has enough moisture in it. What has the weather been like in your area, for the past week or so? What temperature and what relative humidity? I don't trust wood moisture meters, but it seems probable that the wood was too dry.

Tatanka, oil does not replace moisture (=water). You can soak wood in oil as long as you wish, but it does not increase or decrease the moisture content of the wood. You're just adding oil to the water that is already present. However, the oil will absorb part of the heat from the heat gun, and will therefore lower the temperature of the wood and effectively lower it's 'boiling point'. The oil will also hold the heat better than wood, since wood cools pretty rapidly in my experience. I wouldn't recommend soaking a bow in oil, but a few drops of oil in the crooked area will help in heat bending with a heat gun.

[mwosborn]

Thanks for all the input gents.  No one was hurt when she blew - the middle piece didn't even go very far just a few feet.  It hasn't dampened my spirits with mulberry.  My first mulberry has numerous knots in the lower limb and still shoots very well - a bit different design than this one as it bends a bit in the handle and is narrower and thicker limbed.  Will have a go at it again - plenty of mulberry in the shed.  I am still going to be careful with the heating - may even go with steam if I don't have too much straightening to do on the next one.  Nothing like experience as a teacher.

[TatankaOhitika]

I may be lacking in serious bow physics ( as did all primitive cultures who used the bow ) but regardless , I do find lots of oil extends the life of a bow . So I do it because it works . Simple is better . I even have a video on my youtube channel of a firekilled ironwood bow that survived over a month exposed in the open because of the oil treatments . It's still sluggish , but in the end of the day it makes meat . But in my opinion , this is EXACTLY why I back ANY bow that I can , OR build the limbs wide . I don't build bows for speed , power , or cosmetic look . I simply build them for what they were orginally created for- hunting . Because you can spend 30 hours making a perfect bow that shoots 170 FPS , draw it back , and break it . Or spend 10 hours making a trully primitive bow that shoots 120 FPS and drive an arrow through big game at 10 yards . I know our ancestors didn't give a damn about looks . Function equated to survival .

So with that said , I wouldn't dig too deep in science with something so primitive . Hell , even tape measures and blueprint designs will stir your head up and make you think too much . Don't give up on mulberry . It works . It bends , and shoots . Thier will always be failure with even the most carefully designed project . It's a fluke . And most the guys agree here that it was a tension failure from very low moisture . So ? Don't overheat . Substitute low MC with grease or water . They both work .