Laburnum is a wonderful bow wood, I even think it´s my favourite wood.
Unfortunatelly, laburnum wood tends to crack during the drying process. This happens, because the wood at the surface is drying quicker and therefore shrinking quicker, than the inner wood.
But there´s a way how you can avoid this. All you have to do is to slow down the drying process so the wood will dry evenly throughout the whole stave. So right after splitting, you can apply some linseed oil on the entire stave and put the stave into a cool place, which is not too dry. The cellar might be ideal. The stave will dry slower an more evenly. I have never had any cracks with this method!
lonbow