Primitive Archer

using the 5# of spine for every 25 grains of point weight removed rule I should have ....

this is a rule of thumb for approximating dynamic spine from static spine with hunting weight arrows.

So should I make a 50# spine arrow with no tip or fletching and just keep planing it down until it flies well

this method seems more reasonable with the extreme weight reduction and tapering going on with these flight arrows

   ok im over simplifying ,, if you have an applied back,, some wood, and its too thick it will crush the belly cause it doesnt stretch enough,,
  sinew will stretch more than wood so it does not crush the belly in reasonable design,,
so you dont want to make the bow take set and then put it on,,
put it on so it reduces the crushing effect as you tiller,,
someone will chime in and explain it better,,
   if you take the sinew off a shot in bow, ,the wood part will not have take much set at all,,because of the way the sinew effects the bow,,
   that being said,, you can put sinew on a shot in bow, and get good results, but I think you will get better results putting it on before it is shot in,,there are just so many variable its hard to explain,, I have found that if you draw a sinew bow too far,, past the point it was designed for, ,and there is not enough sinew, it will take set too,,
   you can see it when you are test with a chrono,, for example if you draw to 25 inches and you get 170 fps,, and then tiller it to same poundage at 27 inches and get same fps,,,the bow is probably taking set and you have gone past the sweet spot,, or the set the bow is taking is keeping it from shooting harder at the longer draw,, these are just observations from my experience, and may not apply to some bows 

I tend to overthink things, but I don't think it's possible to overthink the physics that determines what you end up with when you set out to make a self bow.  I have read TBB vol 1 and use it like a field guide in the garage.  I have read Clay Hayes' bow building book.  I watch a lot of youtube also.  It is my understanding that the physical crushing of wood cells somewhere along the belly is what causes a bow to take take set.   Cells getting crushed could be the result of 1. pulling the bow when too wet (I assume the dryer the wood, the stronger the cells...why heat treating strengthens the belly and gives cells more resistance to crushing), 2.  pulling too far too soon during tillering, 3. having uneven tiller resulting in a weak spot or hinge that bends too much during tillering, or 4. having uneven limb thickness from one side to the other in an area of the limb. 

Things about this that make me scratch my head and make me think I'm not understanding what I think I'm understanding...or make me realize that I'm not fully understanding it...need more info.

1.  too wet...easy...don't start the process of tillering until the bow has reached moisture equilibrium.

2.  Pulling the bow too far too soon in the tillering process.  The idea here is never pull bow past intended draw weight and you will be good to go.  So, can you not build a 66" long, 1.75" wide flat bow to be 90#@28"?  We all see in various books and publications that you should build your bow to be at least twice as long as your intended draw-length.  You read and we know that weaker woods need to be shaped into wider, longer bows.  I don't think I've ever read the correlation between intended final draw weight and length/width.  Is an 80# at 28" bow of the above proportions destined to take a good bit of set vs a 60# bow at 28"?  How would you make a higher poundage flat bow design without crushing belly cells?  Another way to look at is....If I am after a 55lb flatbow and I never draw the bow past 55# thru tillering, and I get it bending evenly and beautifully and it pulls 55# at 28"....then I decide I want the non-stacking smoothness of a recurve and I recurve the tips resulting in a 68# bow...have I not basically done the exact same thing as I would have by drawing the bow (and bending the limbs) to much higher poundage than my intended weight during the initial tillering?

3.  Uneven tiller resulting in a hinge... I get this.  I get that this is why you never draw past where you notice any weak or strong spots in the arc.  Once you identify a hinge, you are limited to what poundage that hinge spot will give you once the stiff areas on either side are reduced and even tiller is achieved.  If you crush belly cells at the hinge, you are stuck with set or you will be limited to the poundage that hinged area will give you after reducing everything to proper tiller and removing the crushed belly cells...ie. its going to be a way light bow.

4.  Uneven limb thickness from side to side at any spot on the limb.  This one messes with me too.  I know this must happen from time to time (on osage at least) because of having to work with blemishes that happened during growth, but in an ideal world...Is there any situation where it is acceptable or desirable to have a portion of the limb cross-section that shows uneven thickness from side to side?  I ask because I have read  somewhere that you can use this technique in tillering to counter natural limb twist to get tips alligned.  It seems to me that if you did this and anytime you have uneven thickness from one side to the other at any point along the length of the limb, the weaker side would bend much more than the thicker...and cause the belly cells there to crush and take a set at that spot.

Any my last question...if my understanding of all the above is correct, then how is it that sinew will prevent string follow or how will sinew correct too much set?  I get that sinew will shrink and pull a bow into reflex.  Sinew backing also raises the tension/neutral/compression planes of the bow toward the back...so once the sinew is applied an you have a bow with really nice reflex...when you go through the tillering process, if the crushing of belly cells is what causes the set, then wouldn't any of the same issues cause the sinew backed bow to take set also.  If we are relying on sinew tension forces to actually overpower the crushed belly cells tendency to pull the bow into deflex, then shouldn't we always wait until a self bow has been shot in and taken the set its going to take before applying the sinew?

Any insight into any of these ideas that twist my brain will be much appreciated.

Don't give up on your bows that develop a problem.The beauty of wood is you can fix them, re-work, and sometimes save them.  They might even shoot better than before the problem.

Pic of the rawhide in place.  This might look like no other rawhide you have ever seen.  Its from a mule deer a friend of mine harvested a couple years ago when I took them hunting.  They didn't want the hide so I took it.  I left the hair on the hide.  Laid it out in the NM sun with salt on the flesh side and let it dry.  After drying, cut it into strips.  When I'm ready to use a strip, I cut the hair off, soak it in water until it is soft and put it on the bow.