Let's Build a Trilam! (Finished pics on page 12... Refinished pics on page 13)

[PatM]

Upper limb needs a bit more bend.

[Springbuck]

Pat's right of course.

Ty, you have done really great work all along, and this has been fun to watch, so I'm sorry I didn't see this earlier.  First, here is a picture.

[Springbuck]

See this?  Your upper limb is too strong.

[Springbuck]

  Here is what happened and I MISSED IT.  I was watching this thread, but you had plenty of help, so I wasn't thinking too hard as I read.

  You were tillering with the bow held flat and level, fairly securely balanced on two points above and below the throat of the grip.  That is the actual point of pressure from your hand, on the bow, when drawing.  Look at the full draw pic and you'll see your hand is pushing into the bow right in the deepest part of the grip and for a couple inches below onto the palm swell. If you tiller using that point as a fulcrum, the hook on your tillering string should be opposite the upper end of that zone.

Every bow has a physical middle, as measured tip to tip with a ruler, divided by two, right?   Every bow also has a DYNAMIC middle, where the forces pushing the bow forward and pulling the string back are balanced, nearly opposite each other.  Then, there is a balance point regarding the amount of bend, or the strain on each limb, if the bow is asymmetrical. Tiller usually has small compromises we make inherently.  You were GOING for DYNAMIC  balance close to the PHYSICAL middle, I think, but tillered to have dynamic balance ABOVE the middle, up by the arrow.  So, enough big words.......

 In this case, you were pulling the string back at the arrow, but the way the bow balanced on the tillering tree was several inches below that (maybe only 2-1/2", but maybe as much as 4).  So the pull force (string) is above the push force (grip), and the bow resting securely on two points on the tree couldn't tip to show you that.  So, that gave the string more leverage to pull against the lower limb, making it bend as much as the upper limb, despite being stiffer.  So, now you have a stiffer lower limb.

This is all fine if you plan for it, or know it's going to happen, but that is where I feel I/we failed to warn you, sorry.  The fix is simple, though. You just gotta weaken the upper limb a bit, or stiffen the lower limb a bit.  I suggest the former.

 Since the curve looks good on the tree, crayon or pencil mark the whole upper limb and scrape it clean, then check the full draw again.  This, unfortunately means your finished draw weigh will be a couple/few pounds lighter than intended.  Happens to me all the time.

Good luck.

[ty_in_ND]

I think that's why the advice was shoot some arrows through it, get a full-draw-in-the-hand picture, and see how she's doing, so there's no harm at all in saying the upper limb is a bit stiff (which it is!) at this point in the game. 

I'm going to be waiting a week for the leather dye to get here, so I might as well get it tillered spot on before finishing the bow.

Mr. PatM, thanks for pointing it out!  Here's what I'm thinking: I like the shape of the lower limb better than the upper... to my eye, it looks like the upper limb is bending a hair more out of the fade than the lower and it's lightly flatter at midlimb.  So, take a few scrapes off of the middle 1/3 of the upper limb?

[ty_in_ND]

Well, I was able to work a little on that upper limb. I scraped a little (12 plus a touch of sanding)from about 6 inches from the fade to about 12 inches from the tip. I shot 20 arrows through her and took a full draw picture (with a slightly better background).



Still a little stiff compared to the bottom limb. I'll try to get another round of scraping in tonight.

[PatM]

 A trick you can use to make the bend register after scraping is flipping the bow and drawing it several times.  You will stress that limb preferentially.

[ty_in_ND]

A trick you can use to make the bend register after scraping is flipping the bow and drawing it several times.  You will stress that limb preferentially.

I'll give that a shot when I get home (and before I scrape it more, just in case if the scraping hasn't registered from shooting it), thanks for the tip!

[ty_in_ND]

Well, after holding the bow upside down and drawing a bunch, I didn't notice a change in the tiller. I just got done scraping that upper limb again, exercised it holding it upside down, then shot a few arrows out of it.  Here's where she stands:



I think it Still looks a touch stiff, but I think it's getting closer.  I thought I'd leave a picture of where it's at now (especially since I need to get to work!).

[Aaron H]

Looks to me like it's just a touch stiff directly out of the upper fade

[PEARL DRUMS]

 Does it feel like its trying to tip towards you as you draw?

[DC]

It looks to me like the nock point is high. In this case is that a cause or a symptom?

[ty_in_ND]

Does it feel like its trying to tip towards you as you draw?

Hmm... I don't think so.  I'll try to get home for lunch and draw it back a few times to make sure, but the best way to describe it is it the bow sits pretty evenly in my hand when I draw it back.

[ty_in_ND]

It looks to me like the nock point is high. In this case is that a cause or a symptom?

Well, it's nocked a little high right now because the arrow is resting on a bare shelf.  Once I finish the bow, I was going to put some material on the shelf and I had the nock point where it is with that in mind.  I can adjust it, though, when I get home.

[DC]

I was just wondering if the high nock point was making the lower limb bend more. But something in my brain says it's the other way. Help?