flat spots in glass lam bow

[OBX]

I just braced a first lam bow out of new form.It is a fairly radical R/D design.Lams are 2 parallel,one .002 taper,an one .001 taper with .050 glass. The bow looks great unbraced but has a 7" flat spot on each limb at the deepest part of the deflex.Would less taper have prevented this?

[Apex Predator]

Do you have any photos?

[jsweka]

How does it shoot?

[GREG IN MALAD]

When you put a radical bend in a limb it isn't uncommon for it to create a flat spot when strung. If it looks ok at full draw I wouldn't worry too much about it. If it is the first bow out of a new form, consider it a learning experience, rework the form and build another bow.

[OBX]

I`ll try to get photo`s posted. I have not shot the bow yet as I need to shape the riser. It does look much better at full draw,maybe a little more bend in the outer limbs than I`d like. My form is much like that of a MOAB by thunderstick archery.

[kennym]

If I'm thinkin right ,the MOAB has a special lam with it being stiffer at center and ends.

That may work the midlimb more,doing away with the flat spot. You may have this built in,if so,then I'm not sure!!

 Each change in lam design,let alone bow design makes somethin different happen.

Makes it interestin!!

[BenBow]

The gentleman that taught me how to build bows had a moab. It had what I called a dual taper center lam. It tapered narrower at the middle from the riser then wider to the tips. It was very much like what the fast wtt bows are doing. We built a special taper sled to grind the taper so it would be thinner in the middle. Pain to do and now you can do the same thing with power and tip wedges. So not sure that's any help but you might want to use more taper and add a tip wedge to stiffen the tip. This would force that flat spot to bend. You could even glue an tapered piece of glass on 6" of the tip end.

[OBX]

Well it seems I`m not smart enough to post any pictures,but thats another story. I didn`t use a dual taper lam in this bow even though I knew the Moab did. No tip wedge either. Still wondering if less taper would have helped. the flat spots are about 6" long right in the deepest defelx part of the  limbs. If a tip wedge were used, any sugestions on thickness an taper rate. This bow is 62" ntn, 18" riser. 1.25" wide at fades to .5"at nocks. Stack is .375 and looks to be about 50lbs at 26" if my scales are accurate.

[Jason Scott]

Does a reverse taper serve the same purpose as a tip wedge or dual taper as described above? What is the difference between using tip wedges vs dual taper vs reverse taper? On a bow like OBXs. Seems like using a dual taper is similar to the result you would get with reverse taper but only harder to grind.

[kennym]

Reverse full length taper is like having a parallel limb.

The special taper in the MOAB (dual taper?) is like having a tip wedge plus a power lam at the riser.

The tip wedge only stiffens the tip.

[Jason Scott]

What if say you had a four taper stack. Three .002 and one .002 reverse. Would that essentially be a total... never mind, I get it.

[OBX]

the last 12" or so of the limbs are bending good, so I`m thinking a wedge would be the easiest fix,but not sure how much thickness it would take. I buy my lams so is this something bingham or someone would routinely prepare for a customer.

[kennym]

What kinda wedge do you want Danny?

I just made some .050 to 0 in 11" for the test bow. I can make whatever you want.

[OBX]

I`m not really sure what it would take to correct the problem. Trial and error probably. It just gets exspensive  to do alot of testing. Is cost  similar to a pair of regular tapered lams.

[kennym]

No ,more like TD wedges,it is mostly time,the material isn't much.  

11.00 a pair is what I get for TD wedges...

[OBX]

Kenny, thanks for the help. I`m going to finish this bow and see what happens. After New Year`s we`ll talk and see if we can come up with a plan for #2. Till then God Bless.

[sw]

When i started building Magyar horsebows i ran into this. It ended up that i had to reduce the thickness mid limb. Had to build a special laminate to grind out the tapers needed to corrct the issue. I've found this problem at times in some of the shallow R/D bows as well and have been slowly doing the same.

Dave