MIMF

I'm having some trouble bending my purfling around the cutaway. This is my first cutaway attempt. I bent the maple binding with no problem but the purfling is giving me fits. Its walnut/maple/walnut finishing out about .125" wide by roughly 1/16" tall. When i try to prebend on the hot pipe it bends about half way there and then starts delaminating and breaking. I've decided to let it soak a while in super soft 2 and try again later.
How do you guys normally do this?

Assuming you're talking about the side purfling, cutting a slot the width and depth of the purfling line in your bending iron helps keep things together and going in the right direction. Or you can just glue the purfling to the binding and bend it all at once, with the strips tied or taped tightly together to keep the purfling from buckling.

In any case, I've found that gluing purfling together with Titebond 3 seems to work a bit better. Also, if it's the top/back purfling, don't try to bend more than three strips at a time. That sets up too much shear in the glue lines and it is hard to keep it from coming unglued. If one of the strips is really curly, using a straight grained strip on either side helps keep it from breaking.

Thanks, Alan, for your extremely speedy response. And just to clarify it is the top/back purfling. I went back in this evening to give it another go and had a little better success, but not something i would want to repeat if there's a better way. This morning I was trying to bend from the headblock end down. This time I started at the waist and worked my way back up. I still had a couple breaks in the outside piece of walnut, but I think it will go back together okay. I taped the entire purfling in place all the way around the guitar (top and back) and am letting it sit over night. Hopefully in the morning it will be used to it's new shape and make for an easier install.
Binding and purfling seems to be my Achilles' heel. I got in to the habit of gluing the 3 pieces together for two reasons. First, I couldn't hardly rip down a piece that small without it breaking. Then if I did manage to mill a piece that small successfully they always broke when installing. So I got the idea to just make a bunch of strips 1" wide by .040-.050" thick, glue them together as a purfling sandwich and then rip those into 1/16" strips. Worked much better as far as making them, but they sure are stiff going around the guitar. I've mostly been able to manage though, with a few exceptions on regular dreadnaught designs. Going up around the shoulders is usually the hardest part. But the cutaway is just way too tight for this. Maybe I'm making my purflings too big in the first place. I don't know, I'm afraid I may be stumped.
Btw Alan, thanks for the suggestion of the Titebond 3 for this.

Hi Ryan,
I may not be the best person to answer this since I just finished my first build but my build was quite perfling heavy so maybe I can help.

You can see what I did here:

http://www.mimf.com/phpbb/viewtopic.php?f=3&t=3027

I essentially made a modern version of a late 1800's parlor that has 17 strips of alternating maple/walnut perfling with a 0.135 Rosewood binding.

I had a really difficult time bending the extra wide binding and cracked a couple of them trying but I did manage to bend them. I used a hot pipe which is a 2 1/2" piece of stainless automotive exhaust pipe with a heat gun pointing in the pipe. What I found is with the thicker pieces I need to bend them in a couple of passes. I started at the waist and moved out from there. Since it is a parlor guitar it has a pretty tight radius at the waist so that is where I started. Once I had the shape close I then fine tuned it to the exact shape. I found trying to do it in one pass was too much and that is when I snapped the bindings. Doing it in multiple passes seemed to help a lot.

As for my perfling I used Peruvian Walnut which wanted to splinter at almost every bend so I had to pre-bend the shape prior to installing them. The Maple was no problem and I didn't pre-bend. How I ended up doing it was to cut the channel for the binding first and installing it. Then I came back and cut the channels for the perfling which is 1/2" wide. Then I laid in the perfling 3 strips at a time Maple/Walnut/Maple and pinned them in place and moved on to the next 3 until I filled the channels up. That way the Walnut didn't split because it was partially bent and it was sandwiched between the Maple.

I think your problem is that you are gluing them together first and then trying to bend them. I can see where the glue joint would just separate before bending.

So even though you are not doing the number of perfling strips it may be better to try pre-bending them to a rough shape first and then glue them up as you put them in as I did. Or if they will bend individually just by placing them in the channel you may be able to just do them loose and glue them in as you go. I think that is the way most people do simple perflings that are thin enough to bend.

Not sure this helps but... there it is

Cheers,
Bob

More practice, Ryan.

There is a good reason so many folks use "plastic" purflings, they bend nicely and are easier to get more complex lines. However, even with plastic purflings the key is to install them as separate pieces so there is no buckling to deal with. All the better if you can manage putting the purflings and binding on at one time. Try that on an archtop with cutaway. It's difficult even when everything goes well, but you push on and make it happen. It gets better with practice, really, it does.

Hi Ryan,
If you are having problems cutting individual strips to 1/16 th, cut them to 1/8th and install them proud of the top. Then use a block plane and sander to make them flush.

Robert: Yes I remember following that thread. Sounds like a good idea. Unfortunately for this time though my channels are all routed.

Michael: That actually makes me feel better. Thank you. I usually do instal the binding and purfs together. This has all been dry run stuff so far. Since the bindings bent so easily it will probably help when I have those to back the purflings

Clay: I have tried that. It is easier to cut, but such a tall purfling has a tendency to "lean" on me in the channel. but if I can get it to sit flat may still be worth another try.

Okay so maybe i didn't give myself the best starting position by gluing up the purflings the way i did. But i went back in this morning to give it another try. I took to heart Michael Lewis' advice, to loosely paraphrase, 'Quit your whining and just do it.' So i did and it went rather well. I just took my time and went slowly. I'm looking forward to seeing how it finishes out.
Thanks!

Hi Ryan,
Another way I have done purflings Is to glue wider strips (1" +) on the bending form and then cut 1/8 inch strips off on the tablesaw using a fine tooth blade (this can get a little squirrelly when cutting the waist section). I did this more as a "production" thing, but it could also work to make doing the cutaway a little easier. The resulting strips are easily pushed into place to conform to the purfling ledge.

Hi Clay. Yeah I've just about got myself talked into that. I saw a set up in a recent forum or a stewmac newsletter, i don't remember where, by using a small circular saw blade for dremmel sort of like a router table to cut down the present strips. Looks like it could be worth a try.