The thing with Ipe is that it is NOT a workable wood. The front porch stair railing was a composite of 2″×2″ Ipe pieces joined using butt joints. The problem with Ipe is that you can’t just use any old glue, and complex joints are difficult, to say the least. When I built it years ago I used dowels and polyurethane glue, which lasted for a time, but as half of the railing is exposed to the elements, not forever. Ipe is too dense, and oily to use normal glues on. Now rebuilding the piece, I have endeavoured to make it more robust. How?
One possibility is using large robust fasteners – While stainless steel screws work for holding-down applications and pre-drilled Ipe, they do not have the strength to hold in end-grain (i.e. they may shear off). Using a GRK structural fastener requires precise pre-drilling. In normal wood, the screw body compresses the wood as it winds in, and the threads cut into the wood fibre. Not so in Ipe end-grain. I tried screwing a No.8 GRK screw into end grain, in a pre-drilled hole (the width of the screw shaft), and it burst the end of the 2″×2″ (see photo below). The trick may be to predrill just shy of the thread width of the screw threads. The problem with Ipe is that the wood is just too dense.
A better way is to use 2-part epoxy glue, and dowels. I’m using JB Weld epoxy, and 3/8″ dowels 2″ in length. It may also help that these pieces of Ipe have been exposed to the elements for 10 years, so some of the oil has dried out. I have joined a number of the butt joints in this manner and is seems to produce a fairly robust joint. If the wood is fairly new, I would advocate cleaning the area with some form of solvent prior to gluing. Don’t both using water-based glues – they don’t work with these types of tropical hardwood.