Bending high pressure laminate (HPL)

[Alan Peterson]

Borrowing a subject from the Repair Forum about fixing up a laminated HPL Martin ... does anyone know how the sides for (the unfortunately-tagged) 'formica' guitars are bent to shape?

I've looked up the specs on both Formica and Wilson materials, and it seems the time and temperature range to get the job done is quite limited before things begin to warp and bend unpredictably, and the resin starts to bubble up; to say nothing of how tight a curve these materials can handle. Has anyone done it on a small scale, and does it require a 'special' HPL formulation or can the stock stuff be used?

[John Cross]

I built a resonator guitar for one of the $100 challenges using formica from home depot. It bent fine without heating - just gently forcing it to shape of the frame I made and gluing it on. The bends were similar to that of a national 12 fretter so nothing very sharp but I didn't have any problems. I'd suggest taking a scrap and seeing if you can squeeze it into a mold.

[John Hamlett]

Bends of radii around 1" or less are regularly done by counter top makers. Next time you are in a kitchen, look to see if the counter tops are 'post formed'. They're the counters with one sheet of laminate that rolls over the front edge, rolls up to form the back splash, and rolls over the edge of the back splash. I would think that the 'best' way would be to form the laminate in the shape you want. In other words, if you're going to manufacture laminate guitars, form the laminate in the shape of a guitar and not have to bend it at all.

[Bob Menzel]

Years before getting bit by the instrument building bug and having a bending pipe, I bent HPL over a coffee can using a heat gun as my heat source. I've not attempted to craft a guitar using HPL, but it seems to me that it would be a whole lot easier to manage pre-bent sides.

[Alan Peterson]

I would think that the 'best' way would be to form the laminate in the shape you want. In other words, if you're going to manufacture laminate guitars, form the laminate in the shape of a guitar and not have to bend it at all.

Ok, how?
Are you talking about manufacturing my own laminated plastic from scratch, or just taking a piece of conventional stuff and curving it around inside a mold without concerning myself about setting the shape with heat? 'Cuz I can do the latter, but not the former.

[John Hamlett]

I don't know how they do it, I assume they lay up layers of craft paper and resin and press the plastic laminate onto the surface somehow, with heat, inside and outside molds. If they can make it flat, they can make it curved. It doesn't seem to me that it would be a good way to make them at home, that's why I said;
"I would think that the 'best' way would be to form the laminate in the shape you want. In other words, if you're going to manufacture laminate guitars, form the laminate in the shape of a guitar and not have to bend it at all."
The key word there is "manufacture". You'd have to be setting up to make lots of units to make it feasible to do it, and frankly, unless one is going to make lots of inexpensive units, I can't think of many good reasons to make plastic laminate guitars.

[Clay Schaeffer]

I've made several HPL dulcimers and a few HPL guitars, even before C.F. Martin did. Standard grade laminate can be bent to a 3" radius before the color coat will crack. For postformed tops a thinner grade material is used and will take a tighter radius. The HPL is thermoformed to the particleboard substrate.
Standard grade HPL (the thicker stuff) can be bent on a pipe or with a heat blanket, and bends more easily than most woods. It is best to apply the heat to the backside of the laminate to avoid scorching or blistering the color coat (which is actually a photo finish).
When I built the guitars I stuck them together with 5 minute epoxy and no linings. If you used linings then titebond would probably work. I used western red cedar for the soundboards.
Most cabinet shops generate enough scraps that a few trips to the dumpster would get you all the material you can use.

[Louie Atienza]

I used to bend laminate quite often when I had a cabinet shop. We normally used a heat gun and special crayons. We would draw a few lines with the crayon at the bend. When the crayon melted from the heat gun, it was ready to bend. In a pinch a regular crayon would work fine...

You can get laminate in different thicknesses. The thicker stuff is usually called 'horizontal grade' and is the thicker stuff used on countertops, about 1/16" They also have a 'vertical grade' which is about 1/32", and a 'post forming' grade' which is somewhere in between.

You might be able to bend without heat with one of the thinner grades and even laminate two pieces together...

[Steve Senseney]

Clay mentions the finish is a photo finish.

Does this mean you could use photo shop and make this brazilian rosewood?

[Clay Schaeffer]

You could add Brazilian rosewood to a photo shopped picture and if you ordered enough laminate you could have them print it using a Brazilian rosewood print . C.F. Martin could have made the guitars have Brazilian rosewood HPL if they so desired, but I guess they didn't want people to lose their guitars at the border. <g>
There are a lot of interesting patterns of HPL that don't look like wood. I think they are more fun to build with.

[Louie Atienza]

Steve, check out Alpi laminates, they use real wood formed, and resliced, and bonded to phenolic, that mimic other woods, even figured woods... The geometric patterns are really cool...

Aaaah the days when we can buy synthetic Brazilian rosewood...

[Clay Schaeffer]

The down side of Alpi laminate is the cost. It can cost as much as some sets of real wood does. <g>

[Ryan Mazzocco]

with as many HPL guitars as I'm seeing lately (seems like just about all my friends have one) the average player will probably soon start to recognize the HPL sound as what a guitar is "supposed" to sound like. Soon, our real wood guitars will sound just a little too "unnatural." so it makes sense that the Alpi laminate would cost as much as real wood. that way you can get the pure, true sound of a guitar without all the warmth and overtones you get with a cheap real wood guitar.

[Louie Atienza]

with as many HPL guitars as I'm seeing lately (seems like just about all my friends have one) the average player will probably soon start to recognize the HPL sound as what a guitar is "supposed" to sound like. Soon, our real wood guitars will sound just a little too "unnatural." so it makes sense that the Alpi laminate would cost as much as real wood. that way you can get the pure, true sound of a guitar without all the warmth and overtones you get with a cheap real wood guitar.

I expected to see a few emoticons here... but I somewhat agree with you. Maybe the Alpi stuff will be in such high demand that we cold finally afford BRW again!

Really though, at $315 shipped for a 4 x 10 sheet, tubed, that's well under $10/sqft. Not cheap, but not overtly expensive either...

[Clay Schaeffer]

Considering that there are about 4 1/2 sq ft in a back and side set that puts Alpi on a par with sapele, and unfigured maple, walnut, and mahogany. It does offer some advantages in being prefinished and easier to bend.
One disadvantage HPL has, is that above a certain price point there is a lot of buyer resistance. As a hand builder I have fun building them, but I don't take them too seriously. They do offer a good opportunity for a novice to construct a guitar with little investment in tooling and materials. Perhaps we should have an HPL instrument challenge!

[Ryan Mazzocco]

I expected to see a few emoticons here... but I somewhat agree with you. Maybe the Alpi stuff will be in such high demand that we cold finally afford BRW again!

Is that better? I was hoping my sarcasm would show sub-textually <--now that one I meant.

[Rodger Knox]

+1 on the HPL Challenge!

[Louie Atienza]

I made a suggestion for an alernative materials challenge. I thokn it would be fun. actually, my last build was sort of in that line, with its plywood bracing, Alpi sides and back....

[Clay Schaeffer]

Alpi is pretty much just an HPL with a wood veneer. People on the forum have made both acoustic and electric instruments out of HPL in the past. It does offer low cost and is readily available. It's also fairly easy to work with. But it does have limited "bragging potential" <g>

[Louie Atienza]

Alpi is pretty much just an HPL with a wood veneer. People on the forum have made both acoustic and electric instruments out of HPL in the past. It does offer low cost and is readily available. It's also fairly easy to work with. But it does have limited "bragging potential" <g>

I must say those back/side sets that Arnt displayed in the other thread are amazing. How about the "Sky's the limit" challenge! No dollar limit!