glue, backings, sinew & such

[willie]

Also remember that reflex is often just pulled in on a sinewed bow by reverse bracing.  We do also tend to heat treat it in as well but it bears mentioning that it often is just the glued backing retaining the reflex, in which case it is responsible alone.

So some boywers like to reverse brace in order to encourage the shrinkage? Are there pros and cons?, or different schools of thought about how aggressive one should assist the shrinkage? I realize that there are many designs out there, and more than a few eastern traditions that I wish I knew more about.

[BowEd]

That can be a personal choice a lot willie.Once a person gets used to tillering extreme designs they seem to go back to it occasionally.

[DC]

When I did my only sinewed bow I put a some reflex by stringing it backward. The string kept going slack. Something was pulling those tips together.

[willie]

That can be a personal choice a lot willie.Once a person gets used to tillering extreme designs they seem to go back to it occasionally.

By saying "go back to it" you mean that the technique is used selectively? Can you help with the whys and why nots?

[PatM]

Also remember that reflex is often just pulled in on a sinewed bow by reverse bracing.  We do also tend to heat treat it in as well but it bears mentioning that it often is just the glued backing retaining the reflex, in which case it is responsible alone.

So some boywers like to reverse brace in order to encourage the shrinkage? Are there pros and cons?, or different schools of thought about how aggressive one should assist the shrinkage? I realize that there are many designs out there, and more than a few eastern traditions that I wish I knew more about.

Almost everyone seems to reverse brace now.  It does elminate potential for the backing to  separate  as the outside dries faster than the interior if you do one thick layer.

[BowEd]

When I did my only sinewed bow I put a some reflex by stringing it backward. The string kept going slack. Something was pulling those tips together.

That's right DC.Usually no matter how far I reverse brace it.It will slacken the string and gain another good 3/4" on it's own.After a couple weeks the string is no longer needed.It'll hold on it's own.

That can be a personal choice a lot willie.Once a person gets used to tillering extreme designs they seem to go back to it occasionally.

By saying "go back to it" you mean that the technique is used selectively? Can you help with the whys and why nots?

They are just fun to make and shoot.Very durable also.At least for me anyway.I like preparing one then moving on to make more self bows while it's curing.I'm learning to leave them cure a bit longer each time I make one for reasons of gaining poundage.

[willie]

hoosierf.....Nice contributions of experiences you have about backings.Your an experimenter and that's good.I'm a user of combed flax myself to fix things on bows.
I'm wondering if you kept track of the amount or percentage of reflex that your sinewed bow kept after tillering and shot in done with TB II glue?You know there's a reason the asians don't use TB II with sinew on their horn bows.

Ed, I am hoping Hoosierf has a chance to tell us more about his successes. As for the the Asians and TB2, it almost sounds like you already know the the reason why? Can you point to the attempts you are referring to? or enlighten us further?

[GlisGlis]

sinew is strong and has a spring like flexibility
It's the best combination of characteristics we may want on a bow back
other natural backings are usually less flexibles (vegetables fibers) or flexible but not as springy or strong
glue is the medium to keep our backing where we wants
probably an extremely solid glue wont allow sinew to flex well but hide glue is not  that solid (crystallized)
I wont consider sinew putting tension on the back while drying (yes it's a feature but let's consider only finished and shootable bows)
we can put tension on any backing with reverse bracing at glue time but onl the backing with the right flexibility can take advantage of such feature
that's why I think hairs could never match sinew. they'll never spring back ad fast once tensioned
I think that it's as simple as that and that our ancestor already did all the (natural) materials tests electing sinew at first place

[willie]

probably an extremely solid glue wont allow sinew to flex well but hide glue is not  that solid (crystallized)

Good point Glis. properly matching the fiber to the matrix/resin/glue seems to be an essential requirement of composite building. Both for the proper execution of a hide glue/sinew application or any other fiber.

Perhaps there are better more well matched glues for a fiber that has different tensile qualities? 

[PatM]

Of course but then you're likely going down the road of epoxy  or similar for other fibers.

[BowEd]

Sometimes we gotta accept the components for what they are and capable of doing and handling.Remembering what some natural materials strong and weak points are putting them in their strongest position and using them to the best of their ability.The difference in performance then is just a matter of design and tillering.There's plenty enough experimention out there yet for natural materials to not abandon ship on them quite yet.In fact technology tries to copy the strong points natural materials show to enhance their performance.I still think natural materials is the leader in that quest.For them to follow.At least for long bows & even asiatic styles.All because so many designs have been proven by expert bow makers from the past.
The compound bow is the exception though.

[PatM]

In the composite structure world natural materials are getting a renewed life now that technology has figured out ways of working around their drawbacks.

   Particularly in Europe a lot of Flax and Hemp goes into automobiles.

[willie]

Of course but then you're likely going down the road of epoxy  or similar for other fibers.

Not just yet, I am hoping Ed can tell us something about Asians and TB2

[BowEd]

Never seen or heard it used as a glue by them as I said earlier.There is no connection between asians and TT 3.That was my point.Personally I've never seriously considered using it with sinew.
Do you have experience with it willie?

[willie]

You know there's a reason the asians don't use TB II with sinew on their horn bows.

I guess I misunderstood what you were saying, Ed.

No I have not tried it TB2 yet. Although TB3 worked well with some linen.  PVA's are said to be susceptible to creep, but whether a matrix's is strained enough to initiate creep would depend on the glue line loads, or its interaction with the fiber used, so I can see where it might give poor results with a highly strained fiber.

As mentioned earlier, the fiber and glue probably need to be matched adequately, as sinew and hide glue seem to be.  But without knowing the fiber properties in an matrix with a different glue,  it might be premature to assume that epoxy or similar is required.