Gluing in Multilam Reflex

[mmattockx]

Here is a question for those who have built a number of Perry reflex bows. Have you done an FDC and what does early draw look like with the bending force coming from the internal stresses in the limb rather than the belly and back surfaces?


Mark

[Tommy D]

Broke my tillering tree! But I thought I would try my GIFF skills to elicit some tillering advise for anyone with suggestions as to where to start removing wood - whilst I fix the tillering tree!

[DC]

I'm pretty sure that early draw weight comes from more than just internal stresses. String shortening due to recurves for one. Limb shape possibly for another. Telling one from the other could be difficult.

[DC]

Broke my tillering tree! But I thought I would try my GIFF skills to elicit some tillering advise for anyone with suggestions as to where to start removing wood - whilst I fix the tillering tree!

I'm not sure. The left limb may be bending more. Can you pull it with just one hand on the handle?

[mmattockx]

I'm pretty sure that early draw weight comes from more than just internal stresses. String shortening due to recurves for one. Limb shape possibly for another. Telling one from the other could be difficult.

In a Perry reflex bow much of the early weight will come from the internal stresses and some back tension as the belly surface doesn't see actual compression forces until it is drawn back past whatever position it was reflexed from into the glue up. For instance, if I deflex the belly lams and glue them up with 6" of deflex, then pull that assembly into 3" of reflex when I glue the back on (assume these are final numbers after spring back has occurred), the belly surface won't see any compression until the bow is braced past 6". If you braced it right at 6" the surface of the belly lams would have zero stress, either compression or tension and would be contributing nothing to the string tension. All the force the string is seeing would be coming from the internal stresses in the limb and tension stress on the back.

Tommy, I agree with DC, it looks like the left limb is bending a bit more. The bend doesn't look bad to my eye, maybe the inner limbs are bending a touch too much and you might want to get the mid limbs bending just a bit more. The recurves look like they are uncoiling pretty well.


Mark

[Tommy D]

Ok I will fix the tillering tree and resume work in the morning! Thanks for all the help.

[Tommy D]

Cleaned things up a little. Pulling 60lbs which is my target. I can see the left limb still a bit stiff. Can’t decide if optical illusion or slight hinge developing on the right straight out of the fade?

The transition on the recurves already quite thin - won’t touch those for now I don’t think.

Should I leave everything on the tip side of the recurve for now?

String still seems aligned... but I’ve never tillered this much recurve so any suggestions welcome.

At what point does one consider a short string? When would one file string grooves?

[willie]

the gif is cool, I can "explode" it into the components. looking at giphy.gif.048  It does seem like the fade area over your left knee is bending more, and not sure if the other limb is too stiff, it looks as good as the rest, (except as noted above your knee)

[DC]

I think I would try bracing it. Is you hand on the handle? It looks a little to the(my) left to me. I also see a bit too much bend by your knee. I'd leave that area for now.

[Tommy D]

 I wasn’t quite sure what you meant about the left limb?  Yes my hand is on the handle. But I haven’t glued the handle on yet. That part is thicker because of a power lam and also I left my belly and core lams thicker. Will try brace it tomorrow

[Tommy D]

Ok so I’ve filed some string grooves ...
 and strung it!




But the string pops off when I pull it...

I have to say these recurves are making me a bit nervous... anyone have a string pop off in the shot? What happens? What’s it like if it does? I am beginning to think I am a straight limb guy!!!

Close up of the grooves and alignment ...



Here is a short GIF of why the string wants to pop off. Seems one limb tip has a weak side. I can see that I thinned this side more then the other side at the deflex/reflex transition.

Not sure where to try and correct this ... I know the tip bends to the weak side ... so supposed to take material off the strong side... just not sure where? And whether to work on balancing the other limb first...

[PatM]

I find it is better to manually torque the twist the opposite way rather than trying to thin one edge.  Clamp in a vice at the handle to do this. 

[Tommy D]

Hi Pat that twist develops in the draw... at brace height everything seems lined up. Is it still worth torquing in this situation?

I guess I could try and deepen the string groove on the weak side...

[PatM]

Yes, you need to torque it as you bend it.  The wood needs to be "trained".

[Tommy D]

Yes, you need to torque it as you bend it.  The wood needs to be "trained".

Sounds like my dog! Ok will give it a go!