Recurve limb tips/nocks to fill or file??

Mark31121

Member
Ironman
I've recently swapped my setup around and I've noticed that my string doesn't sit in the top limb very well, which is making alignment awkward as it causes a slight twist.

The reason for this is a difference in the depth/position of the nocks on either side of the limb (I think they're called nocks anyway??). If I reduce the draw-weight the effect isn't as noticeable (which is why I've only just realised), but I need the extra draw weight to keep my arrows in tune...

So my question is this - should I fill in the deeper nock and with what (I was thinking some kind of epoxy) or should I file out the shallow one to bring them level? I'm only talking about a 2 mm-ish difference, but it's enough so that the string will pop out of the groove. After I've got it sorted one way or another I'll be able to sort the alignment out hopefully.

The limbs are nothing special, just some intermediate level wood/carbon SF's I picked up off eBay so I wont be too bothered if I kill them, but I don't want to get more quite yet as I'm still hoping to get up an extra few pounds before committing to something better. Even with the twist they shoot really well though...

I'll post some pics to show everyone how I get on
 

Del the Cat

Well-known member
Yes and no. :)
Adjusting and repairing your own kit is to be commented and encouraged IMO.
BUT, only if you have a good idea what you are trying to achieve.
Things like "(I think they're called nocks anyway??)".
Don't fill one with confidence.

I often say "solving problems is easy...The hard thing is working out what the problem is".
People often confuse the symptom with the problem and effect with cause.

I'd say take it to bits, clean up the mountings and make sure everything is cleanly and correctly fitted.
If you are absolutely certain there is some limb twist caused by the way the string sits in the nock, try temporarilly padding one 'shoulder' of the nock with something like masking tape or slivers of softish plastic (say cut from a milk carton).
That way you can experiment without ruining anything.
I'm a great believer in experimentation.
There has been a preveious thread on here where Border Bows explained some of the intricacies of string nock and goove dynamics on a recurve.
Hopefully he may step in and offer some advice..
Del
 

Timid Toad

Moderator
Staff member
Supporter
Fonz Awardee
Ironman
How long have you had these limbs? If they are under a year take them back to the shop.
 

dvd8n

Supporter
Supporter
Have you checked the limb alignment adjustment on the riser? I think that that should come first ......
 

Mark31121

Member
Ironman
How long have you had these limbs? If they are under a year take them back to the shop.
not quite a year but they were off eBay and an auction.

Have you checked the limb alignment adjustment on the riser? I think that that should come first ......
yes, which is when I noticed the problem, in this case I'm fairly confident it's the limbs that need the attention - the string just doesn't naturally want to go where it should and I've checked it on two risers.

BUT, only if you have a good idea what you are trying to achieve.
Things like "(I think they're called nocks anyway??)".
Don't fill one with confidence.Del
nomenclature can often be confusing, just because I'm not sure what it's called doesn't mean that I don't understand its function. for a longbow they're called nocks, so I was assuming that they were for recurve, but things aren't always that simple. I've stripped down a corsa engine and rebuilt it and I don't have a clue what most of the parts are called (the car even worked after)

In this case the vertical string groove is fine (it's nicely in the middle) but the shoulders (thanks, a much better word) on the side are different heights so if I tape over the groove then the string doesn't naturally want to run down the middle - sort of like trying to tow a trailer with a wonky tow bar.


I often say "solving problems is easy...The hard thing is working out what the problem is".
People often confuse the symptom with the problem and effect with cause.
I'd say take it to bits, clean up the mountings and make sure everything is cleanly and correctly fitted.
If you are absolutely certain there is some limb twist caused by the way the string sits in the nock, try temporarilly padding one 'shoulder' of the nock with something like masking tape or slivers of softish plastic (say cut from a milk carton).
That way you can experiment without ruining anything.
I'm a great believer in experimentation.
There has been a preveious thread on here where Border Bows explained some of the intricacies of string nock and goove dynamics on a recurve.
Hopefully he may step in and offer some advice..
Del
I had already tried the padding and it seemed to help a great deal (I should have mentioned that earlier!), but a permanent fill would be a hassle I think, thus the reason for the thread. I'm going to set the bow up today and have another check before I do anything, just in case the differences are for some other reason.
 

Del the Cat

Well-known member
Hi Mark, sorry if I sounded patronising/snotty etc.
That's the problem with not being face to face. We only have the written word to go on.
It sounds like you know what you are doing and already know the solution but were waiting for reassurance.
I'd say go for it, even if worst case it ruins a limb, you will doubtless learn a good amount which will put you ahead of the 'armchair experts'.
To answer the Q, I'd say to fill or file depends on how much filling and what sort of section of filler will be present, bearing in mind the load which will be applied. The big plus with filling is you can get back to close to the original poition if it all goes wrong. (e.g the shoulder will need roughing up a tad before building up with filler)
Out of interest (or not ;) ) I get a similar problem making self wood longbows. Sometimes a nock needs moving across to prevent twist and maintain good string alignment. For this reason tips are usually left wide until the last minute, but I still sometimes have to fill temporary nock grooves on the edge of the bow with wood dust/epoxy mix. These fixes will disappear under a horn nock when the bow is finished.
Cheers...
Del
(Anyone who's stripped and rebuilt an engine is good to go IMO :) , and I like your analysis and wonky tow bar analogy.)
 

Mark31121

Member
Ironman
No worries Del...

I had a bit of a play in my lunch break today, firstly I re-centered the limb alignment on the riser and checked using a pair of limbs that I know are straight (but unfortunatly too heavy for my dodgy wrist) and then swapped to my current limbs - the top tip was way off, I put the limbs on upside down and the same limb was out, the other on was fine on either the top or bottom.

I had a closer inspection of the limbs and I could see where the string had been running etc and there was a bit of a lump on the wood layer so I filed that lump off and restrung everything, a few twangs to get the string to sit where it wants and using beiter limb tip guages to keep the string out of the groove and... it was a huge amount better! not perfect but well within adjustability - so with a bit of tweaking of the limb alignment it's all looking straight :) (much easier than with a longbow).

I can't shoot it til tomorrow, but I'm much happier. If I need to do any more adjustments I'll probably fill the other side, so as not to weaken anything.

I love the idea of making my own longbow, I've read loads of your posts Del - but, I should probably finish revovating my house first though else my other half will kill me.
 

Mark31121

Member
Ironman
Success!

My first end and the arrows were well grouped, but way to the left - a quick swap of the spring in the pressure button for the normal one (rather than the extra hard) and that put them towards the gold. An hour of tuning later and they were grouping well, so much so that I shot out two nocks in my last two ends...

Overall I'm happy with how it worked out - my arrows are now showing as a little stiff rather than weak (as they should be based on the charts) and by the end of the session there wasn't any sign of the twist so I think I'll leave the limbs alone now and just shoot it as it is for a while and do some more tuning once I can get some more distance as it seems to be fine at 20 yards anyway.
 

Mark31121

Member
Ironman
Excellent! :)
Did you fill or file in the end?
Del
I filed a little bit to smooth out the one groove (the wood layer had a lump), which was just enough so I could get everything aligned using the adjustment on the riser. if I needed any more and I would have filled the other side as the gap between the shoulders was much smaller on that limb to the other one.
 
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