Using Glued in laminations to create reflex... Bamboo backed bows.

[Tommy D]

I’ve started another bamboo backed ipe and was wondering if anyone has ever used tapered laminations in just the sections one wants to induce more reflex or in recurving bow tips. So rather that a full length triple lam bow, one makes a sort of “power lam” between the bamboo backing and the belly in the part where one wants it to bend more?

[Del the cat]

IMO
Simplicity is the watchword, especially if you are having glue up problems, it's always tricky to get a perfect blend where an additional piece is glued on, and any discontinuity is  asking for a void in the glue line or a stress concentration.
Keep it simple, for get the fancy recurves... they look pretty but don't necessarily add performance. Broken bows never perform well .
Del

[Hilongbow]

I've made a handful of BBI trilam R/D bows with tapered maple cores (usually .003"/inch). Not a huge fan of the work that goes into it (too much fussing with perfect fit). The biggest lesson I've learned is that even with the tapered core, I needed to add a long (several inches beyond the end of the riser block) and fairly thick (at least 1/4” at the center) power lam to prevent the fades and inner limbs from bending too much too early in the tillering process, at least with my designs. My most recent one was my best, but it has no power lam or riser. 54" bend in the handle bow, glued up with about an inch of reflex, and it's a rocket launcher. I think I used .006"/inch taper. Almost perfect tiller off the form.  I personally wouldn't try to put recurve tips in a BBI. I don't know how you'd get the ipe to cooperate (but I've never tried, so grain of salt). Maybe if you spliced in static tips. If you do a power lam or tip wedge, make sure it tapers down super super thin for the last half inch or so. I like Del's advice but I wanted to share what I've learned in a handful of bows sort of similar to what you asked about. One of the many nice thing about wood bows (over gl*ss bows) is that you can tiller the belly to put the bend where you want it, and don't need wedges with perfect tapers and many glue lines

[Tommy D]

I hear y’all! Maybe won’t do it this time but I suspect that I will at some point! Just for fun!

[PatM]

Typically people just put a kerf in the tips to recurve Ipe to any degree.  You need to splice in tips if you want a real static curve though but it's worth the effort.

 A static Ipe/bamboo is a very fast bow.

[Dances with squirrels]

I have. It works great. If I remember correctly, Dean Torges discussed it in his DVD, Hunting the Bamboo Backed Bow.

It's versatile... it can be used to make a working recurve that won't pull out with use, or a more static recurve, depending on taper rate of the insert. You can vary the thickness, length, taper rate, etc. based on your desire.

When cutting the kerf, it's nice to have a resaw fence accurately set up, but it's not necessary. I did several before I had a resaw fence. Just be sure the table is perpendicular to the blade, and the core wood has a nice flat edge so it stands parallel to the blade.

Here's an easy way to find the perfect thickness for the 'insert', regardless of kerf size. Mark the kerf line on the edge of the core wood and run it into the bandsaw, let's say, 10". Ok, whew... that's done.... that's the scary part. Lol

Then take a lam tapered at your chosen rate, but that's obviously too thin on the thin end, and run it sideways into the kerf at your 10" mark where you stopped cutting. Slide it through there gently just until it stops, if it's pinched in there, back it up just a tiny bit to allow room for glue, and mark it. That's where you cut it off. And when you slide it in properly, lengthwise, during glue up, it will perfectly fill the kerf where it ends without leaving gaps because it's too thin..., or trying to act like a wedge and split your core wood at the end of the kerf because it's too thick.

Even if you want to glue a parallel piece into your bow blank's kerf, you can still use this technique with a random, tapered piece of wood, mark it, remove it and mic it, in order to determine the perfect thickness for your parallel insert.

[avcase]

I do this all the time.  I also prefer using lams or wedges to glue in reflex, deflex, or any other limb curvature because it stays put and improves strength.

Here's an easy way to find the perfect thickness for the 'insert', regardless of kerf size. Mark the kerf line on the edge of the core wood and run it into the bandsaw, let's say, 10". Ok, whew... that's done.... that's the scary part. Lol

Then take a lam tapered at your chosen rate, but that's obviously too thin on the thin end, and run it sideways into the kerf at your 10" mark where you stopped cutting. Slide it through there gently just until it stops, if it's pinched in there, back it up just a tiny bit to allow room for glue, and mark it. That's where you cut it off. And when you slide it in properly, lengthwise, during glue up, it will perfectly fill the kerf where it ends without leaving gaps because it's too thin..., or trying to act like a wedge and split your core wood at the end of the kerf because it's too thick.

That’s a great method!

Alan

[Tommy D]

Thanks guys ... that’s great info. Much appreciated. Must one cut a kerf? Or can one stack a lam between the bamboo back and the belly wood. A kerf seems the nearer solution but I am not sure I trust my combined bandsaw blade wonder and skills ... may do it by hand.

[Dances with squirrels]

Perhaps you could do it that way. Depends on how much curve you're trying to get. But one of the benefits of the kerf is that it turns the core into two thinner pieces, three including the insert, making them MUCH easier to bend into the shape you want. That's not going to happen by laying it between the backing and core.

There are other ways you can get and keep the core parallel to the blade of the bandsaw if you're not confident doing it by hand. You could clamp it to a bigger block of wood or something. I keep a chunk of 3" steel angle several inches long right next to my saw that I clamp stuff to to hold it in position for the bandsaw... mainly use it for Z splices in odd shaped billets, but it would work for this too.

[Hilongbow]

The other responses above reminded me of a few threads I have read in the past that have great info on this type of bow. I entered "bamboo ipe kerf" into Google and got several good results