Flatline Raptor one piece recurve build-along
Posted: Sat Apr 13, 2013 12:31 am
Here we go again. In this build-along I'll try to get down to some of the more basic stuff so it is a little easier for the first timers to understand. I'll also be using some of the text and photos from my other build where the steps are identical.
The Raptor is a rather complicated and difficult bow to build but it has a very smooth draw all the way out to 30 inches is dead in the hand, very fast and very forgiving. With performance values like that in a 58 inch bow its well worth the extra effort.
Having said that the basic construction methods set out here can be applied to any composite laminated bow design keeping in mind that this is how I build bows. I’m sure there are many totally viable variations to the methods I use.
Now for a bit of a dodgy start I forgot to take any photos of the riser block prep so I will describe it as best I can.
All Flatline risers are made from 4 separate pieces of timber glued together with thin, usually contrasting veneers between. This is done to guard against the inherent instability and movement you get in all timbers due to temperature and humidity. I use “Techniglue CA” an Australian made epoxy with very good flexibility and tensile and bond strength stats for all of my bow work.
I start by milling the selected timber (in this case Purple Gidgee and Silver Ash) into pieces the appropriate size and 1 or 2 mm thicker than I want them to finish at. They are then ground to the required thickness using a 36 grit belt on the lam grinder and glued into a 45 mm wide block. The Raptor riser is made from a block like this and another crescent shaped piece (in this case Hairy Oak)which forms the back of the riser because the glass on the back of the bow goes through the riser as opposed to over the back of the bow. These 2 pieces are marked out using stencils, cut on the band saw and have to be ground to match perfectly and the crescent piece must match the bow form (mould). This is the form I will be using. It has some pretty extreme curves which make the lay-up quite challenging. Here’s where the Raptor is a little different from most one piece bows, usually in a one piece the riser incorporates the fades (the thin wedged part that leads into the limbs) in the one piece of timber. But in the case of the Raptor I’ve made the wedges separately and glued them into the riser block. I’ve done this for several reasons, being; the unusual shape of the riser, I can get a much finer, longer, accurate taper leading into the limb and I can use my timber of choice Silver Ash for wedges.
Here’s how it’s done, the main block is marked out using the same template, then clamped into a 17 degree jig and using a 10 degree dove tail bit in the router the limb planes are formed as I would do if I was making a take-down. These surfaces are roughened up to insure that when the wedges are glued they have a good bond. The block is then marked and pieces cut out to allow for clamping and gluing of the wedges. Wedge blanks are cut on the band saw using a wedge template against the fence. Then ground on the lam grinder using the same template. The wedges are 8 1/4" long and 300 thou thick at the butt end which makes them very finely tapered. The butt end of the wedges are cut at 10 degrees to match the angle left by the router, this helps to key them into the riser block. Your wedges (or fades) need to have a consistant taper that ends in a finely feathered edge.
When you hold the wedge up to the light it should look like this. Here they are ready to be assembled and glued. I leave the wedges a little wider than the riser block to allow them to be dressed down to size once they are fixed in place. I've run out of atachment space, to be continued in the next post.
Rob.
The Raptor is a rather complicated and difficult bow to build but it has a very smooth draw all the way out to 30 inches is dead in the hand, very fast and very forgiving. With performance values like that in a 58 inch bow its well worth the extra effort.
Having said that the basic construction methods set out here can be applied to any composite laminated bow design keeping in mind that this is how I build bows. I’m sure there are many totally viable variations to the methods I use.
Now for a bit of a dodgy start I forgot to take any photos of the riser block prep so I will describe it as best I can.
All Flatline risers are made from 4 separate pieces of timber glued together with thin, usually contrasting veneers between. This is done to guard against the inherent instability and movement you get in all timbers due to temperature and humidity. I use “Techniglue CA” an Australian made epoxy with very good flexibility and tensile and bond strength stats for all of my bow work.
I start by milling the selected timber (in this case Purple Gidgee and Silver Ash) into pieces the appropriate size and 1 or 2 mm thicker than I want them to finish at. They are then ground to the required thickness using a 36 grit belt on the lam grinder and glued into a 45 mm wide block. The Raptor riser is made from a block like this and another crescent shaped piece (in this case Hairy Oak)which forms the back of the riser because the glass on the back of the bow goes through the riser as opposed to over the back of the bow. These 2 pieces are marked out using stencils, cut on the band saw and have to be ground to match perfectly and the crescent piece must match the bow form (mould). This is the form I will be using. It has some pretty extreme curves which make the lay-up quite challenging. Here’s where the Raptor is a little different from most one piece bows, usually in a one piece the riser incorporates the fades (the thin wedged part that leads into the limbs) in the one piece of timber. But in the case of the Raptor I’ve made the wedges separately and glued them into the riser block. I’ve done this for several reasons, being; the unusual shape of the riser, I can get a much finer, longer, accurate taper leading into the limb and I can use my timber of choice Silver Ash for wedges.
Here’s how it’s done, the main block is marked out using the same template, then clamped into a 17 degree jig and using a 10 degree dove tail bit in the router the limb planes are formed as I would do if I was making a take-down. These surfaces are roughened up to insure that when the wedges are glued they have a good bond. The block is then marked and pieces cut out to allow for clamping and gluing of the wedges. Wedge blanks are cut on the band saw using a wedge template against the fence. Then ground on the lam grinder using the same template. The wedges are 8 1/4" long and 300 thou thick at the butt end which makes them very finely tapered. The butt end of the wedges are cut at 10 degrees to match the angle left by the router, this helps to key them into the riser block. Your wedges (or fades) need to have a consistant taper that ends in a finely feathered edge.
When you hold the wedge up to the light it should look like this. Here they are ready to be assembled and glued. I leave the wedges a little wider than the riser block to allow them to be dressed down to size once they are fixed in place. I've run out of atachment space, to be continued in the next post.
Rob.