Help me out here.

[mwosborn]

I glued up a FG longbow on a new form the other day.  Things seemed to go great with no problems (should have known).  I pre-mark the limb profiles after taping the limbs before I glue up.

Took the bow out of the form and cleaned off the glue using the sander.  Things still seemed ok.  I went ahead and used the sander to grind down to my marks to shape the limbs.  (I did not check the alignment of the bow before doing this - should have!)  I then glued on some tip overlays and let it sit over night to dry.

So today I filed in some string grooves and strung her up.  Oh crap, looks like I have a limb twist.  I thought no big deal, must not have the limbs even on each side of center.  Won't be a problem to fix.  Thought I better check alignment before going on.

Unstrung the bow and laid it on a flat surface with the side of the riser down (on the flat surface) and measured the distance between the flat surface and the tip of the bow on each end - bow were 1/4 inch.  Flipped the bow over so that the other side of the riser was down against the surface and measured each end again - both were 1/2"!  If things were straight they should have been the same in my mind!   :(

Decided to check it with a  string (which I should have done before cutting out the limbs).  I clamped the unstrung bow in a vise and put my double weighted string from tip to tip.  Sure enough, I was a 1/4" off on one end when I lined the string from one end and through the center of the handle.  

So.....what the hell caused it.  Did I screw up my layout that badly?  Is my form messed up?

Since I did not check alignment before cutting out the limbs I am not sure.

Those with experience, what is the most likely cause?

Kenny - glad I decided to do a "trial" run on this new form using black glass and some basic maple lams instead of the pretty cherry lams and clear glass I got from you.

[monterey]

First, what is an FG longbow??   :confused:  

Warped form seems likely but if your layup is not held tight on the sides it might be squiggling around.  Or maybe your form is a bit wider than the lams.

Probably can be saved if you narrow it down.  But I'd narrow it all the way to the tips to keep the limbs bending evenly.

Don't do anything until you get some other opinions.  My advice isn't always the best.

[kennym]

If air hose, the hose if not centered, can sometimes roll a little with air pressure and scoot stuff around.

Like Mike said, might be form, but you can straightedge it and check that.

If you can pike it a bit without losing too much reflex, the limbs get wider and you might be able to shave more on the one side. Which you will need to get right weight anyway. Assuming it is a D/R ....

I never lay the bow out til glued and cleaned up, I know some guys do, but I figure if its gonna happen , it will happen to me! Plus if a lam or glass slides, I wanna be able to see if I can counter it.

I may make a template tho with holes down center to line up on centerline.

[Bvas]

I'm curious how you determined that one end is off 1/4", or could both end be off 1/8"?  Correcting both limbs a little might require less piking to save limb width.
I'm not doubting, just curious how you came to this conclusion?

I would also double check the form for square. Not sure this would cause your problem, but it's worth checking.

I'm with kenny. I don't layout limbs til it comes off the form. I put a center mark at middle of handle and one at the end of both fades. Then adjust center of limb tips so that string lines up with  all three riser marks.

[mwosborn]

Thanks Monterey and Kenny,

I checked the form over pretty good.  Straight edge along the side and it is straight.  I put the bow back on the form and squared up the riser with the form and the one tip is off center by 3/16th or so.  I am thinking like you Kenny, it moved under pressure.

I do not think it is a twist problem, it is just the tips don't line up through the center of the bow.  

Stuff happens I guess.  I am going to finish it up to where I am shooting it just to see what happens.  Plus I need the practice.  

I will try another one of this form, but I bet I check alignment after it is glued up and before I cut out the limbs.  

[kennym]

You wouldn't think glass would bend edgewise but it does fairly easily. I had some bowed edgewise a few years back. You could lay it on bench with ends together and a gap in center, and with little pressure bring the center together.

[Robertfishes]

sorry this happened to you. When I mark the glass center I use a 72" straight edge, I always make 3 center marks first.. a few years back I laid the 72" straight edge onto the taped glass and the center mark in the middle of the glass was off over 1/8".. I checked the marks and they were fine??? I put straight edge beside the glass and the glass was crooked like a banana..this piece was part of a 12 piece order and was the only one that was banana shaped. Now I check every piece of glass to make sure it is straight. I still cannot figure out how this one piece was cut banana shaped from the factory.. OK, you said your form is straight, are you using washers or wood blocks on form sides to keep lams from sliding?  like you said always check center of bow blank with string after removing glue squeeze out.

[monterey]

When mine come off the form the first thing I do after knocking off the slag is carefully take each side down with a file at the fades on both sides of the bow.  Then I locate center of the blank at each fade and draw a full length center line with a straight edge.

Sometimes it doesn't look so good but whatever comes out of it, it is pretty straight.

[mwosborn]

Originally posted by Bvas:
I'm curious how you determined that one end is off 1/4", or could both end be off 1/8"?  

That could be I don't know for sure.  I put the bow back on the form and squared the riser up with the washers on the form, the one tip was off quite a bit (about 3/16")  and the other one off just a smidge.

I am going to add a set of washers to this form closer to the ends to keep the glass from sliding and I am going to get a 72" straight edge.  Right now I have two sets of washers on the riser section and then a set just past mid limb on each side.

Still, I just screwed up - I knew better than not to check for alignment after the glue up - just didn't do it this time.  Won't happen again.  Well, I hope not.    :D

You also gotta make sure the curves on your form are true...  If not your limbs will go to one side and you will get twist...

  Also make sure you have enough space for your hose... A cross section of your hose should look like an oval race track...  If your cross section looks like a dog bone it will tweak your form and your bow bigtime...  Trust me...  

[kenneth butler]

I am probably misunderstanding but if the tips are in line with each other and it is just a 1/4" off center line at the handle. Couldn't you just work with the handle. Depending on which way it is off and a right or left hand bow make it a little more or less center shot, and remove more wood from the outside thick side. Hoping to help but really just trying to understand.>>>----> Ken   Would like to see pictures.

[mwosborn]

KB,

The limbs are not in line is the problem.  If you run a string from tip to tip the string does not run through the center of each limb.

I went ahead and finished shaping the bow and it actually shoots very nice.  I cut the shelf on the "string side" so it is actually cut past center a smidge.  I am going to go ahead and sand her up and put some finish on it.  I think it will be just fine other than the string is slightly off center.  You have to look pretty close to be able to tell.

[kenneth butler]

O.K. I got ya. I was thinking of some of the "character self bows" They sometimes wander both sides of center line. Sounds like you have it shooting O.K. Good deal. >>>---->

[Mark R]

If thats all you can do to fix it and the string tracks off center to one side of both limbs after awhile you might have both limbs torquing and bending that way, good luck.I laid out a couple of bows on the tape before cooking, and after out of the form and checked for center, one came out fine and one did not.It seemed easy to layout before cooking and made shaping easy after, but if not checked for center can be a problem, as you know. I now lay out after there cooked.

[kenneth butler]

Would make the nock grooves slightly deeper on one side shift it toward center a little?>>--> Ken