Deep ripples in Pau Ferro sides

[hewitt]

Hello all, I just bent some Pau Ferro sides and have some pretty deep ripples in the lower bout. The rest of the sides are nice and flat. I bent using a heating blanket on a simple form with the waist clamped and the upper and lower bouts slowly bent around the form and held with spring clamps. The sides were .080 and spritzed with water. I tried using an iron with the form to flatten out the ripples, but this didn't seem to help much. My fear is that I will be down under .060 by the time I get the inside and outside flat. Would rebending with the heating blanket on top help? Any suggestions would be greatly appreciated. Thank you.

[John Link]

You could laminate a piece of mahogany veneer to the inside of each side before leveling. Many use laminated sides now, including Ervin Somogyi, on the theory that the stiffer sides force more string energy into the soundboard and back. In any case, lamination virtually guarantees there will be no cracks in the sides as the instrument ages. I've never tried it but intend to. Dave Bagwill is quite experienced with the technique, I believe.

[hewitt]

Thanks John. As much as I hate to do it, your suggestion may be the way to go. Once ripples have been formed, is there any way to eliminate or reduce them? Not sure why this happened...mold too hot or wood too wet. I cooked them for about 3 or 4 minutes at about 300º F and then another 5 at 280º F, then let them cool on the form for a few hours. When I pulled them off there was very little springback and only slight scorching.

[John Link]

It's called the revenge of the trees.

[Dave Bagwill]

Hewitt - is this the first time you've used this particular form and/or blanket?

[ken cierp]

Post some pixs of your bending set up. To start I'd say the sides were too thick to begin, .075" is what Martin uses, bending life became much easier once we went to that blank dimension. We never bend at that high temperature 250 works fine. Seems your ripples were caused by grain configuration, sides that are not 1/4 sawn can do strange things -- slab cut is the worst. Lastly plenty of fine guitars have sides that are 1/16" or even less, put in extra reinforcements.

[hewitt]

Thanks gents,

These are my first real sides that I have bent on this setup. I did bend a 3 inch wide by .090 piece of mahogany as a test and it bent well with no ripples. I have also bent curly maple bindings with good results. I will send a picture of the setup tomorrow. I will check the sides again, but I remember they looked to be pretty well quarter sawn. Would it make sense to sand the outside flat and leave the inside with some slight ripples. I could use epoxy for gluing in the lower bout reinforcements as it could work as a gap filler. This might leave me with finished sides that are between .065 and .070, not counting the low spots on the inside lower bout. Thanks again.