Sunday, August 2, 2009

Mandolin Post 3 and Wood Bending 101

Well its time for post 3 on my Mandolin Project . I ended the last post with a contraption I had assembled and asked for guesses as to what it was for. Sadly I got no response . The unit was made to bend Hard Maple wood. If you look closely at the picture there is a Torch pointed into the pipe . The pipe bent on an angle in the vise and the vise mounted solidly to a table.

This was the part that scared me the most and turned out to be the most fun. I cut my Hard Maple sides to the approx size I wanted ( slightly over Size) Then I put them in a PVC Tube I have glued an end on and filled it with water , closed the top so that the wood was completely submerged for a day .

The wood has to be quite soaked. I then took the individual pieces out and fired up the torch , as the pipe got hot , I rolled the wood pieces back and forth over the pipe applying SLIGHT PRESSURE.

This is the hardest part, as the wood begins to steam , I lifted it up and continued spraying the back of the wood with water to keep it wet . It started getting ply able and the first reaction is to press harder BAD MOVE . IT WILL BREAK ! I went through 5 pieces to get 3 Bent as I needed.

After an experiment , and a broke piece , my first part was ready for the mold. As you can see I have made a Plywood Mold from my pattern I showed in post 1. Clamp the part in place and let it set for 24 hours . As the wood drys out it will retain what ever shape you have it molded into .
I strongly recommend the plastic footed claps as you see below , the Quick Grip Type . The others will leave marks that are very hard to sand out , as I discovered the hard way .

After the bending and shaping was done I moved to an Internal Mold as shown below to fit the parts together . I have said they will hold their shape, that's true to about 98% there is slight movement or was on my unit. As you can see I have also put the Tail Piece and Head Piece in to fit the sides to here

These parts are being Glued into place in this Jig at this point , so that when its done you have the outer ring made up of the 1/8" side parts as well as the Tail Piece and Head Stock.

After the Sides and Ends have been glued together I started Gluing the " Kerfing " into place . This material is slotted to bend to the shape your making nicely and is glued in a approximately 1/64" below the surface of the edges . I did this on purpose so that after I had the unit Glued up , I could run it through my Sander and make sure it was Level and flat prior to working on the back.

I suspect most will have the unit in the Jigs until the back is glued in place . I however chose to allow the sides to expand and move to the exact figure that the bends took them to and then applied it to the back. This was a choice I made to let any stress that had been created from the above gluing to be relieved . Good / Bad I don't know , however it did seem to work

If you are going to allow the stress to relieve as I did DO NOT notch the head piece prior to this because then the alignment may be slightly off. It does make the notching a bit harder , however I felt the possibility of relieving as much stress as possible was good on my first attempt.

The Next post will involve shaping and gluing the back and internal supports

Thank You for stopping by and following my little project


Heidi said...

I was still working on the guessing part!!! DANG IT - now ya done spoiled it for me!!!! **Mutters under breath**

Karen Deborah said...

this is stinkin cool! I am still trying to guess if you can play the thing after it's built!

COFFEE MAN said...

No I cant really play the mandolin , I do know a few cords , however the person playing it in the end will be a musican not me