recurve limbs?

[USAFdad]

I'm building my first recurve which is a 3 pc TD. My 40 year old Howatt recurve has slight grooves in the belly of the limbs that lead into (or out of) the string nock grooves. They are about 4 inches long or about half way around the curl. Question is: Why are they there, and are they necessary. Only thing that comes to mind for me is to keep the string in the middle of the limb. These grooves are very shallow. What happens if you file thru the glass? Scrap limb?
I have built 4 reflex/deflex long bows but never thought about those grooves until I happened to look at my old Howatt the other day.
Thanks

[Bowjunkie]

They're there to help keep the string where it's supposed to be, at the center of the limb. They don't have to be very deep to accomplish their goal. Use your Howatt for reference on depth.

Their length should extend to the point where the string no longer lays on the limb when the bow is braced. In other words, anywhere the string is touching the limb, it should be in a groove.

You can start them before stringing for the first time, just extending them an inch or two beyond the V at the tip, then extend them to their proper length once the bow is braced at its proper height and the limbs are properly aligned. That way you know exactly where to stop, and exactly where it should be side to side.

[Trux Turning]

X2 what bowjunkie said. I've seen older bows with the groves completely through the glass. On my recurves I usually glue on a thin wood overlay on the belly side and just file the string grove through that.

[USAFdad]

Looking at the Howatt with my glasses there is no way that the groove is not all the way thru the glass. When you say thin overlay Trux Turning how thin, .020-.030?
Thanks again

[Trux Turning]

.020-.030 is probably where they start and taper to zero. Once I start seeing the glass beneath I quit filing the grove- I sttll file into the glass a little- just not all the way through.
 

[USAFdad]

That's a great visual for me. Clears up the fog in my brain. I appreciate it.
If this thing works out planning to give it to my son when he gets back from Afganistan.

[Dan Bonner]

I like to string the bow and get the limbs aligned perfectly first and then trace the outline of the string and file between the lines. If you file before you brace the bow you may find you have to adjust the nocks to get the limbs to track straight and your string groove will wind up in the wrong spot. I used to use veneer overlays and cut the grooves in them. Now I'm lazy and just cut it in the glass. My personal hunting bow I accidentally filed through the belly glass. I've been hunting with it for two years and thousands of practice arrows with no problems.

Bonner

[LittleBen]

I don't think filing through the glass should matter. If you think about it, most glass recurves don't bend very much in the curve. Also, the width of the groove is not much, ,aybe 10% of limb width at absolute most.

So unless you're talkign about really heavyweight bows it's probably no big deal.

Should be any more stress on the glass than shotting a bow with 10% more draw weight.

[talkingcabbage]

Anyone remember the old Bear bows? Every one of them are filed clean through the glass.  I still can't bring myself to do that on my recurves, but I've never heard of a problem with the old Kodiaks.

[Crooked Stic]

Here is one thing you will be happy you done before filing those grooves--Get your tiller perfect so the string lands dead center every time BEFORE you do any filing. Don't ask  

[Bivyhunter]

My string groove overlays are .060" wood X 5" in length, if that helps at all.