Face or back

[Flem]

Some of us weirdos actually design/build our bows so they have a tiny bit of string follow

Mike, are you going to pre-impregnate and cook your bi-axial fabric before lay-up?

[Roy from Pa]

Some of us weirdos actually design/build our bows so they have a tiny bit of string follow :say what:

A little string follow yields a quiet smooth shooting bow, especially with a long bow!

[Longcruise]

Managing set in wood/glass ASLs is what got me thinking about the "face/back" question.  With thick cores, I think the use of glass thicknesses that are are appropriate for given bow weights in r/d and rc bows is reducing the glass wood ratio to a point where set becomes inevitable.   You will see it on many if not all "hill style" bows.  Sometimes it's a smooth arc resulting in a string follow effect and often it's abrupt in the face area.

Based on this information, the real answer we are looking for is probably thicker glass or graphite on the belly to prevent the high compression.  In a nod to Shredd, perhaps it could also be attacked from a design perspective by designing a trapezoidal limb to mimic a D-shaped cross-section?

 Set could be alleviated by having the proper width taper for the chosen thickness taper.

Yes, that is an important consideration.

[Longcruise]

Some of us weirdos actually design/build our bows so they have a tiny bit of string follow

Mike, are you going to pre-impregnate and cook your bi-axial fabric before lay-up?

I'm thinking about that and can't quite make up my mind.   My small test hasn't been examined yet but so far I think it can be layed up the same way as stabilcore if the glue is thin enough.

I squeezed the test strip together in a foodsaver bag and left it on a floor heat vent yesterday afternoon.   I'll give it a few more hours. 

[Longcruise]

Some of us weirdos actually design/build our bows so they have a tiny bit of string follow :say what:

A little string follow yields a quiet smooth shooting bow, especially with a long bow!

Won't argue with that but OTOH, if I want string follow I'd rather put it there intentionally.

This playing with the bi ax is not primarily to deal with the "face back" question.   It's just come up coincidentally as a possible approach.   The bi-ax is going into the swap bow for stability since,  so far it has some serious hooks.......  Unless I decide to completely change to another style. 

[Longcruise]

There are air bubbles in the test strip.   I forced the EA-40 in pretty aggressively.  Think the epoxy needs to be thinner.  What to use??

[EvilDogBeast]

EA 40 should be fine.  We impregnate dry cloth by putting the cloth on a sheet of our nylon vacuum bag material, pouring the needed resin on top of the cloth, folding the nylon over top, and then squeegee the resin into the cloth.  This will allow you to see the air bubbles and chase them out.  After that take the impregnated cloth out and apply it to whatever.  Use a little extra resin when doing this because you will lose some to the nylon when you peel it apart.  I'm at work now and can do a little sample to show you if you like.

[Longcruise]

I would like to see that.

[EvilDogBeast]

Sounds good, I'll have it up in about an hour!

[Longcruise]

Sounds good, I'll have it up in about an hour!

Thanks.   I'm about to head out for a long walk.   Getting bow shop fever. 

[EvilDogBeast]

[EvilDogBeast]

[williwaw]

if I want string follow I'd rather put it there intentionally.

Intentional means to deflex the limb on the form rather than have the bow take set after being drawn? The object being to create a lower string tension at brace possibly?

My suggestion about proper limb taper was to prevent set/damage being taken at the fades. Isn't set at the fades what causes excessive handshock?

[Flem]

Nice demonstration I am surprised how transparent the resin cured, considering how dark it looked in the cup.

Mike, I think I would look for a epoxy with a viscosity rating of 600 CPS or less. The fabric will wet out a lot easier and you are less likely to end up with excess resin content, especially if not pressing or vacuuming the lam while curing.

[EvilDogBeast]

Flem, I didn't wait for it to cure.  It keeps that greenish tint enough that I wouldn't use it on a bow with clear glass.  It's a shame though because it's a really strong resin.  Nearly double the shear strength of EA 40.

[Longcruise]

if I want string follow I'd rather put it there intentionally.

Intentional means to deflex the limb on the form rather than have the bow take set after being drawn? The object being to create a lower string tension at brace possibly?

My suggestion about proper limb taper was to prevent set/damage being taken at the fades. Isn't set at the fades what causes excessive handshock?

Yes,  that's how "string follow" is induced when it's intentional.   Many ASL stle bows that are layed up flat take on the string follow with use just as a self bow does. 

I don't think hand shock is related to set at the fades.  One of my bows is built with an arc of reflex in the outer 24 inches of the limbs.   It was originally destined to be a wide pyramid bow with. O02 total taper.  68" NtN.  There was a huge bit of squiggle in the form and it ended up being 1 1/8" at the fades.  . It took some set at the fades but it doesn't have hand shock.  It's actually a pretty good bow.   It was meant to be 55# but ended up at 43#.  DFC is a plumb straight line, whereas a string follow bow tends to have a bit of perch belly in the DFC.

I think hand shock is from an incorrect grip (chockin the chicken) and/or poor tillering.

[Longcruise]

Flem, I didn't wait for it to cure.  It keeps that greenish tint enough that I wouldn't use it on a bow with clear glass.  It's a shame though because it's a really strong resin.  Nearly double the shear strength of EA 40.

I see what you did there and it makes sense.  I would prefer to stay with EA40  since it is well proven and that approach looks like it would work.   I'm going to do a run like that with EA40 and see how it works out.   

I did another test strip like the last one with some epoxy that is a bit thinner than EA40.   It’s the stuff that is sold in the hobby stores usually packaged under the store name.   It’s 15 minute stuff so it didn't take long.   Still a bit of air bubbling.

Flem,  I agree on the thinner stuff and maybe I'll go against the tech support advice and try the epic with the EA40 or maybe use Epoximite if you think it will hold up in a bow.

[EvilDogBeast]

EA40 should work fine for impregnating the cloth.  After you pour it out on the cloth and cover it with the plastic, spread it out on the cloth lightly with your squeegee or your hands and let it sit.  Once its been there for a few minutes start chasing air bubbles.  You will know the cloth is fully impregnated when you can flip the plastic over and see resin between it and the cloth on both sides.  You may see pin-point bubbles on the cloth but they should pop when you peel the plastic open to get your cloth out.

[williwaw]

if I want string follow I'd rather put it there intentionally.

Intentional means to deflex the limb on the form rather than have the bow take set after being drawn? The object being to create a lower string tension at brace possibly?

My suggestion about proper limb taper was to prevent set/damage being taken at the fades. Isn't set at the fades what causes excessive handshock?

Yes,  that's how "string follow" is induced when it's intentional.   Many ASL stle bows that are layed up flat take on the string follow with use just as a self bow does. 

I don't think hand shock is related to set at the fades.  One of my bows.....

I think hand shock is from an incorrect grip (chockin the chicken) and/or poor tillering.

Coming from a wood bow background, its common to discuss tillering and limb design alongside full draw pics illustrating the final bend. It's been difficult for me to understand some of the pros and cons of ASL design, as I have seen very few pics on the tiller tree.
 Did your 68" bow carry it's bend all the way out into the tips?  A 20" stiff handle?

Is there room in this thread for example pics of poorly tillered designed /shocky bows and full draw pics of bows that  get it right? I know it is a bit off topic, and can open another thread if you think best.

[Longcruise]

Let's go ahead and post them up.