Author Topic: non-matching grooves  (Read 3231 times)

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Offline stuckinthemud

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    • avenue woodcarving
non-matching grooves
« on: November 23, 2016, 12:02:07 pm »
Afternoon!

OK. so, matching grooves run the full length of both the limb and the horn so that the pieces interlock.  Karpowicz' book says this is a modern technique and none of the older bows he has examined are built like this.  So, if you are cutting non-matching grooves, as long as they are running parallel, would it be OK if they do NOT run the length of the horn since, I believe, the point of the (non-matching) groove is to maximise the faying surface and to prevent the horn and the core from inter-locking - a series of overlapping, shorter grooves might be more effective than full length ones? Or would this be more hassle than its worth and possibly create a problem you don't need for tillering?  Perhaps more importantly, he suggests that on matching grooves, the surfaces must be clinically clean as even the smallest particle of dust can cause delamination by creating voids, effectively preventing a full inter-lock and pushing the horn and core apart.  Presumably this phenomenon is not present in non-matching grooves?
« Last Edit: November 23, 2016, 12:20:08 pm by stuckinthemud »

mikekeswick

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Re: non-matching grooves
« Reply #1 on: November 24, 2016, 04:42:42 am »
They need to run full length of the horn and be absolutely straight. To do non-matching grooves you need to make two different scrapers.
The idea of the non-matching grooves is that they are filled with glue at glue-up and provide a material that has a stiffness somewhere between horn and wood.
Matching or non matching both require no dust etc on the surfaces.
The key is to not touch the horn or core with bare hands and do many sizing coats of thin glue with the parts hot. It normally takes me about 20 coats to get the parts glossy.