Correcting limb twist

[mgilbert]

I'm working my way through my first recurve bow, and am having trouble getting the limbs straight.  In the photos, the tiller stick is centered on the bow, but tilts ever-so-slightly to the left.  Where do I have to sand?

Thanks.

 

 

 

[Mounter]

Deepen the nock on the left side a little, to make them even. About 5 srokes with your file, then check it, it may need more. If you still need to, sand on the right side...

[Holm-Made]

Mounter is right. When you sand on the right side, do it mid limb.

[mgilbert]

Thanks, Mounter and Holm-Made.  I've searched the net and there seems to be conflicting information about where to sand.  I think my laminating form is good, but I have little experience using a band saw.

[Robertfishes]

mgilbert, I just completed my 4th recurve off of the same form. one thing I experianced during tillering was this, I had some twist in a limb, I unstrung the bow and forgot to mark twist direction, I strung the bow back up and twist was gone..I think the string loop was a little small for the un finished tips so I switched to a thinner string with larger loops. After that experiance I always string and unstring a couple of times checking for twist before filing nocks or if needed sanding the limb edge. I am still learning..

[mgilbert]

Hi Robertfishes.  I have strung and unstrung the bow more times than I can count.  My problems began when I was too willing to trust the line I had drawn down the center of each limb when I traced the limb shape.  This was compounded by my aforementioned inexperience using a band saw- I cut too close to the line in places because I lost control of my cut (I didn't drop the bow or anything, but I got a little off track and the damage was done).

I feel I'm doing a lot of sanding, and not much is changing.  We'll see how it goes.  Thanks for your input.

[Apex Predator]

I would finish the limb edges to almost spray ready before making final adjustments.  I find the rough tooling marks and uneven sanding account for some twisting that will work itself out upon final sanding.

In other words, you appear to have some sanding left on the limb edges.  I would make them straight and smooth before correcting too much.  Sanding a divot out of the edge can take off quite a bit sometimes.

Clear as mud, huh?

[Robertfishes]

Apex has built a bunch of bows and brings up a excellent point about sanding the limbs to the point that you can spray finish them, I think what I was trying to say was to try another tillering string, one with bigger loops if you have one, at the time of my tillering event I had a Small loop Black Widow recurve string on the bow, my tips and nocks are larger than theirs. I found a custom string in my string pile that just happened to have slightly larger loops and it seems to work better for me, I am still learning and am building by myself with only this site and one other that I refer to for info, I use the search function alot

[Robertfishes]

mgil, what I have been doing is to not use my band saw to cut limbs, I have been using my belt sander with a 50 grit belt to grind to near the lines, then switch to a 120 belt to grind to the line. I found that the 50 grit belt will grind about as fast as a band saw will cut, I am using the blue belts from Sears.. I use the band saw for my riser cuts,I use a carbide blade. the carbide blade and grinding the limbs were  tips I read about on this site.

[TradBowyer]

I"m with Robertfishes..I use a 36 grit belt from Supergrit.com...takes it off rather quick

like has already been said (looking at your pics) file the left nock deeper, sand the right side of the limb.

also, make sure your nock grooves are even. If one is higher, the limb will show twist especially on recurves.

[mgilbert]

Thanks Apex Predator and TradBowyer for your thoughts, which are in fact much clearer than mud!  I think I need to move to rougher sand paper.  I'm using 120 grit with a rubber sanding block, which is probably too fine (I'm using it mostly because I have tons left over from my kayak building projects).  The belt sander sounds like a good idea - I first used one only a couple of years ago and was amazed at how fast it removes material.

Another thing I've discovered is that my band saw blades dull quickly.  I'm cutting the riser for my second bow, and found I was able to cut faster with a Japanese draw saw.  I know carbide tipped is the way to go, but can someone suggest the right blade for cutting risers?  In my saw right now is a 6 TPI 3/8" wood blade.  I cut the limbs with a skip tooth blade at the suggestion of Elmont Bingham.

[GaryB]

D

[GaryB]

Does this method work with laminate longbows with reflex deflex? It doesn't seem to be working on mine.

[TradBowyer]

GaryB,
Yes it works on all laminated bow designs. the difference with longbows is it takes more material removal to make a difference due to the thicker limbs. Recurves have much thinner limbs and react a lot quicker to changes.

[GaryB]

Ahh. That's why i'm having to take so much material off. I'm loosing poundage rapidly, but I'm ok with it if I can salvage it.

Thanks Tradbowyer.

[grizz]

A thing to remember "the limb will always lean toward the weaker side" so sand the opposite!