CLMAPING RESSURE FOR HORN AND CORE
I have my horn and core ready for glue. each has been grooved with a handy little triangualr toothed blade a freind of mine machined for me in his shop.
the dry fit between horn and core is near perfect. To ensure that I do not starve the joint of glue what clamping presure should I aim at?
With other hide glue based bow applications (wood composites) I have had great sucess with ~150lbs of clamping pressure. My concern is due to the denisty of the horn. does a higher density amterial require a higher or lower claming pressure than more porous wood. How much pressure before I starv the joint?
Thank you in advance for your assistance.
Chris
the dry fit between horn and core is near perfect. To ensure that I do not starve the joint of glue what clamping presure should I aim at?
With other hide glue based bow applications (wood composites) I have had great sucess with ~150lbs of clamping pressure. My concern is due to the denisty of the horn. does a higher density amterial require a higher or lower claming pressure than more porous wood. How much pressure before I starv the joint?
Thank you in advance for your assistance.
Chris
Chris:
Starving the joint is not an issue here, because before the final glue-up you make sure there is a fairly thick, glossy layer of glue on the wood and horn. It is done with multiple applications of hot, thin glue, until the horn is dark and glossy, the same with wood. Once this preparatory layer is dry, the parts are heated, a thicker hot glue (25-30%) brushed on both surfaces and the clamping begins. As to the pressure, it is sufficient to have glue squeezed-out at the sides. Many 2 to 3 inch C-clamps through some padding, tightened rather well, work fine. You need many clamps for uniform pressure along the horn strips, because horn is very flexible when hot.
Adam
Starving the joint is not an issue here, because before the final glue-up you make sure there is a fairly thick, glossy layer of glue on the wood and horn. It is done with multiple applications of hot, thin glue, until the horn is dark and glossy, the same with wood. Once this preparatory layer is dry, the parts are heated, a thicker hot glue (25-30%) brushed on both surfaces and the clamping begins. As to the pressure, it is sufficient to have glue squeezed-out at the sides. Many 2 to 3 inch C-clamps through some padding, tightened rather well, work fine. You need many clamps for uniform pressure along the horn strips, because horn is very flexible when hot.
Adam
I now see the need for multiple sizing coats. makes good sense - starv proof joint!
Thank you again for your valuable insight...if you decide to write a book on the subject fo horn bows, put me down for the a copy.
Thank you again for your valuable insight...if you decide to write a book on the subject fo horn bows, put me down for the a copy.
I am always surprised that no one else uses inner tube strips to assemble horn to wood core. The first strip can be put on widely spaced to quickly assemble and the next ones can be put on more densely for maximum pressure, even to overlap eachother. The whole can also be heated to achieve squeeze out. This method does not exclude a form which can be added to the mix before wrapping or after.
I thought that I was the only wierdo who favored this technique untill several years ago I read about a Brit, I think Chris Boynton who also uses this technique to assemble slats for glued up wood bows. His bows hold distance records for heavy bows.
In Korea the bowyer adds only water to the edges of the layers during assembly and capillary action sucks it into the innermost openings activating the glue. -j-
I thought that I was the only wierdo who favored this technique untill several years ago I read about a Brit, I think Chris Boynton who also uses this technique to assemble slats for glued up wood bows. His bows hold distance records for heavy bows.
In Korea the bowyer adds only water to the edges of the layers during assembly and capillary action sucks it into the innermost openings activating the glue. -j-
Inner tube? I have used inner tube on laminated wood bows joined with epoxy with good success.
However, I was under the impression that hideglue required higher clamping pressure than the rubber strip could provide.
If rubber strrip work as well as mutiple clamps - my life will be much simpler - anyone else have thoughts on this?
However, I was under the impression that hideglue required higher clamping pressure than the rubber strip could provide.
If rubber strrip work as well as mutiple clamps - my life will be much simpler - anyone else have thoughts on this?
Chris W
Myself and several other bowmakers here in Australia have been using the inner tube wrapping for some time with great success on laminated longbows. Here's a link to a recent RD bow buildalong by one of our members. http://www.ozbow.net/phpbb2/viewtopic.php?t=5295
Building composite horsebows is still a fledging stage although the number of trad archers buying Grozer/Kassai horsebows have really taken off. I'm interested in your thread so far ~ I have all of the components ready to put together for a Mongolian horn bow but have not been able to find any good pictures of the next step. Do you have some progress pictures, especially some of the tool used to make the grooves in your horn and core?
Myself and several other bowmakers here in Australia have been using the inner tube wrapping for some time with great success on laminated longbows. Here's a link to a recent RD bow buildalong by one of our members. http://www.ozbow.net/phpbb2/viewtopic.php?t=5295
Building composite horsebows is still a fledging stage although the number of trad archers buying Grozer/Kassai horsebows have really taken off. I'm interested in your thread so far ~ I have all of the components ready to put together for a Mongolian horn bow but have not been able to find any good pictures of the next step. Do you have some progress pictures, especially some of the tool used to make the grooves in your horn and core?
Hey Adam! Is this where it all began?CHRIS W. wrote:
I now see the need for multiple sizing coats. makes good sense - starv proof joint!
Thank you again for your valuable insight...if you decide to write a book on the subject fo horn bows, put me down for the a copy.
Chris,
I suggest you get a copy of Adam's book. It is the most easily available and the most comprehensive. The techniques are easily applicable in the manufacture of other bows and Adam discusses some different ideas for sinew application etc. http://www.ottoman-turkish-bows.com/
Regarding the inner tubes, I am also familiar with it from old books on bow making, particularly earlier works on laminated bows. I thought though that the different ways that glues cured might have some effect. Epoxy and polyester resin adhesives cure chemically, but hide glue cures by evaporation and subsequent polymerisation.
What are you using for your source of sinew?
I suggest you get a copy of Adam's book. It is the most easily available and the most comprehensive. The techniques are easily applicable in the manufacture of other bows and Adam discusses some different ideas for sinew application etc. http://www.ottoman-turkish-bows.com/
Regarding the inner tubes, I am also familiar with it from old books on bow making, particularly earlier works on laminated bows. I thought though that the different ways that glues cured might have some effect. Epoxy and polyester resin adhesives cure chemically, but hide glue cures by evaporation and subsequent polymerisation.
What are you using for your source of sinew?
You may know from woodworking lore that if the fit is good the clamping pressure does not need to be so great. Wind an inner tube strip around the finger several times and tell me the pressure generated.
I?ve tried a lot of different ways to clamp horn to the core. A proper fit and and a well done coating are the first steps, to heat the glue at a max. of 65C, to heat the horn and the core and a well heated workshop are the next steps.
I don?t advice the use of an inner tube, cause it is airtight and is extending drying time highly.
I prefer these selfmade clamps: http://redhawk55.wordpress.com , search for selfmade clamps.
Easy to do and very effective, cause you could do a very fine tuning of the pressure where you need it.
Michael
I don?t advice the use of an inner tube, cause it is airtight and is extending drying time highly.
I prefer these selfmade clamps: http://redhawk55.wordpress.com , search for selfmade clamps.
Easy to do and very effective, cause you could do a very fine tuning of the pressure where you need it.
Michael
Inner tube clamping is only air tight if you cover the entire surface. You may have read from my previous posts that it is desirable to leave spaces between the wraps to check for squeeze out. The other advantages are 1. the speed of assembly is unrivaled 2. the economy of the tools, 3. you can work on a form 4. you can lift the assembled bow core over a heat source to induce further squeeze out. The tube strips do not loosen 5. you can check for twist without the clamps interfering with the view, 6. tube strips have the most even pressure including the sides. Only rope clamping also affects the sides, and then maybe excessively.
A second or third layer of strips may be added DIRECTLY OVER THE TOP OF THE FIRST LAYER ALLOWING SPACE FOR SQUEEZE OUT.
You do not need all that cumbersome hardware which slows down the assembly and obscures the view of the bow. I make numerous dry runs to check the fit and get a feel for the final glue up. So quick!
Comments welcome.
A second or third layer of strips may be added DIRECTLY OVER THE TOP OF THE FIRST LAYER ALLOWING SPACE FOR SQUEEZE OUT.
You do not need all that cumbersome hardware which slows down the assembly and obscures the view of the bow. I make numerous dry runs to check the fit and get a feel for the final glue up. So quick!
Comments welcome.
This is a very interesting topic.
I think each method has it's pro's and con's. I like the fact that when using modern clamps there is little chance of inducing twist.
After experimenting with the traditional rope method I have got a lot faster - the clamping pressure that can be applied this way is immense. I practised on a piece of lemonwood and the rope actually left imprints on the wood!
I think each method has it's pro's and con's. I like the fact that when using modern clamps there is little chance of inducing twist.
After experimenting with the traditional rope method I have got a lot faster - the clamping pressure that can be applied this way is immense. I practised on a piece of lemonwood and the rope actually left imprints on the wood!
Hey Jack, I?m almost sure that you haven?t had any view on the selfmade clamps. I?ve experienced inner tube, rope, usual clamps. The wooden selfmade clamps I?ve made and I?m using are really unrivaled. I got the idea from a guy who is making wooden toys for children.
It costs you some wood, screws, nuts, some thread rod. Thats all, well done they will outlast every inner tube.
Used with a torque key you are able to fine tune the pressure where you need it. Sidewards slipping away of the horn or the core is impossible, twisting could be adjusted by tuning the pressure or by clamping the lamination to a straight timber.
These clamps could produce much more pressure than an inner tube, the whole glueing could be done much faster than any other method.
Jack, take this! Michael
It costs you some wood, screws, nuts, some thread rod. Thats all, well done they will outlast every inner tube.
Used with a torque key you are able to fine tune the pressure where you need it. Sidewards slipping away of the horn or the core is impossible, twisting could be adjusted by tuning the pressure or by clamping the lamination to a straight timber.
These clamps could produce much more pressure than an inner tube, the whole glueing could be done much faster than any other method.
Jack, take this! Michael
Michael; I did go to your site and did see your home made clamps. I do like these; they are less bulky than traditional clamps. However it would take an equal number of these to make a hornbow as, for instance, C-clamps. And a hornbow would require a curved form, not a straight beam. To allow for a form, a longer bolt would be required.
I do not see how adjusting two screws is any faster than one, at any rate is slower than winding with strips.
I am using a belt sander somewhere in the joining process, as I see you also do, so close fitting surfaces should be a natural outcome. The pressure requirements are not so great.
Technique is unimportant; there is nothing but technique.
Keep up the good work. I always enjoy your contribution. Jack
I do not see how adjusting two screws is any faster than one, at any rate is slower than winding with strips.
I am using a belt sander somewhere in the joining process, as I see you also do, so close fitting surfaces should be a natural outcome. The pressure requirements are not so great.
Technique is unimportant; there is nothing but technique.
Keep up the good work. I always enjoy your contribution. Jack
habe mir eine holzform gebaut um den holzkern und die hornstreifen zu verleimen weil ich letztes mal probleme gehabt habe.jetzt ist der holzkern sicher beidseitig genau gleich und gerade was sich positiv auf den tiller auswirken sollte.[/img]
Old topic - Adam describes in his book very well how to solve this issue the old or the "modern" way with clambs, he even provides an excellent picture.
If the corewood is strong/thick enough no other jig is necessary - you may also do it the "Japanese way", which is extremy fast, once you have the wedges made.
http://198.170.107.188/phpBB2/viewtopic ... sc&start=0
Reto
If the corewood is strong/thick enough no other jig is necessary - you may also do it the "Japanese way", which is extremy fast, once you have the wedges made.
http://198.170.107.188/phpBB2/viewtopic ... sc&start=0
Reto