Official Luthiers Forum!
http://www.luthiersforum.com/forum/

Cumpiano method for plate joining
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=49789
Page 2 of 2

Author:  SnowManSnow [ Sun Oct 08, 2017 8:53 am ]
Post subject:  Re: Cumpiano method for plate joining

—- scratching my head. Seems small bungee cords would be useful here in some way. Hmmmm


Sent from my iPhone using Tapatalk Pro

Author:  jshelton [ Sun Oct 08, 2017 9:42 am ]
Post subject:  Re: Cumpiano method for plate joining

Mike Lindstrom wrote:
Last I saw, Robbie O'Brien had switched to the LMI jigs, but when I was learning, we pre-cut the scrap from the top, making the whole plate into a wedge and we'd put that on a board between 2 angled fences and drive the wedge shaped top into the fences. It's better to weight it down before banging it into place to keep it from bowing on you.

I've used this method for over 50 years. Simple and works great; however if the edges of the top are uneven or the plates are not wide enough for tapering the wedge method is required. Caution should be taken when weighting the top since if you wash the glue off the top and lay steel on the damp wood it will make a permanent black stain. I use aluminum plates to insulate the steel bars from the wood.

Author:  Ken Jones [ Sun Oct 08, 2017 10:39 am ]
Post subject:  Cumpiano method for plate joining

Clay S. wrote:
"I taped a few guitars and liked the simplicity of it, but there were times when the plates wouldn't be perfectly flat along the joint, which made gluing thinner plates impossible for me. "

Using slightly thicker plates with the tape method solves two problems - fibers torn out by tape removal and any slight misalignment of the plates is removed when the plates are (semi) final thicknessed after the glue has fully cured. I like to check the stiffness as I sand to thickness.


I’m with Clay. The tape method is so easy and quick, I doubt I’ll ever use any other method. I, too, always join up stuff over-thickness, as I deflection test my tops, so I always like to sneak up on my target thickness. It also eliminates concern about tape pulling up a few fibers. KISS.

I should also mention the space and time-saving aspect of the tape method. I recently jointed and glued up four tops and three backs in maybe an hour and a half. As soon as one was taped and cleaned up, I’d stack it vertically between two thick pieces of plywood, conveniently out of the way. Regarding alignment, it’s really just a matter of getting comfortable with your process, and being conscious of alignment while pressing the sides down to the surface. And yes, I use hide glue. This is now the quickest, easiest, and most reliable step in the whole build process for me.


Sent from my iPhone using Tapatalk Pro

Author:  Clay S. [ Sun Oct 08, 2017 10:42 am ]
Post subject:  Re: Cumpiano method for plate joining

Brad wrote:
"the joint is straight from the power jointer. I still have some work to do, it's not totally invisible."

How sharp are the knives on your jointer? If sanding improves the joint they may not be sharp or you may be running the wood across the jointer too fast (not enough cuts per inch) If one knife is slightly higher than another slowing down should also give a better result.
The joint should be tight enough that you can make it "disappear" with hand pressure even without glue. Hide glue shrinks as it dries which should make the joint tighter and less conspicuous than most other glues.
If the joint is giving you fits, you can- slightly- relieve the section from the lower edge of the soundhole to the top of the upper bout (assuming the fingerboard covers the upper edge of the soundhole). In those areas a less than perfect joint wont be seen and can allow the lower bout area to come together better. Although it's nice to have a perfect joint from the top to bottom of the soundboard it's really only needed from the lower edge of the soundhole to the bottom of the lower bout.

Author:  Woodie G [ Sun Oct 08, 2017 8:42 pm ]
Post subject:  Re: Cumpiano method for plate joining

These are current student work. With finish. 5x, 3x, 1.5x.

Attachment:
IMG_6375.jpg


Attachment:
IMG_6376.jpg


Attachment:
IMG_6377.jpg


5x and 2x.

Attachment:
IMG_6371.JPG


Attachment:
IMG_6373.jpg

Author:  AndyB [ Mon Oct 09, 2017 12:33 am ]
Post subject:  Re: Cumpiano method for plate joining

Tape works fine on thick plates and hot hide glue. But if your plates are close ... not the way to go.

Andy

Author:  Hesh [ Mon Oct 09, 2017 4:32 am ]
Post subject:  Re: Cumpiano method for plate joining

Using one's thumbs for leveling the joint very quickly when the tape is stretched and the plates are now laying flat with the tape method initial plate thickness is not all that critical.

What is critical but it's critical with any joining method IME is the joint itself has to be well prepared, freshly planed (preferred) and absolutely gapless.

I always thicknessed all my top stash to .140" for stickering, storage, deflection testing and joining. I found .140" to go fine with the tape method but you do have to check that center seam as soon as laying things flat and be quick about it too with HHG.

Before I got sick of building and the dust didn't agree with me much I built in batches of four. With the tape method I did not need a jig to join plates meaning that I could join four tops all at once and set them aside. For other things depending on jigs such as side bending it always slowed me way down because of the dependency on jigs and of course I only had one bender.

Author:  James Orr [ Mon Oct 09, 2017 2:29 pm ]
Post subject:  Re: Cumpiano method for plate joining

Clay S. wrote:
"I taped a few guitars and liked the simplicity of it, but there were times when the plates wouldn't be perfectly flat along the joint, which made gluing thinner plates impossible for me. "

Using slightly thicker plates with the tape method solves two problems - fibers torn out by tape removal and any slight misalignment of the plates is removed when the plates are (semi) final thicknessed after the glue has fully cured. I like to check the stiffness as I sand to thickness.


But unfortunately not always possible. I had a great Italian top I wound up not being able to use. It was just too thin (previous owner) when I tried to glue it up.

The tape method certainly works, it's just not my preferred.


Sent from my iPhone using Tapatalk

Author:  James Orr [ Mon Oct 09, 2017 2:33 pm ]
Post subject:  Re: Cumpiano method for plate joining

doncaparker wrote:
I'm uneasy about the idea of using hot hide glue with a ropes and wedges jig (i.e., the LMI jig or any homemade version). I am just imagining how much time it would take me to figure eight the ropes and slide in the wedges. But that's just me. Like I said above, the Cumpiano/Natelson method goes really fast after you set up the dry run; probably less than a full minute. I'm happy with my tailored version of it until something better comes along, and nothing has so far.


I hear you. It's actually pretty quick unless the ropes are unnecessarily long. Since HHG pulls itself tight (the proper term is escaping me), it should only take a few quick taps of the wedges.

I use Tightbond, but used to be an HHG guy. I would want to be prepared (have things laid out), but wouldn't worry about timing.


Sent from my iPhone using Tapatalk

Author:  SteveSmith [ Mon Oct 09, 2017 3:47 pm ]
Post subject:  Re: Cumpiano method for plate joining

HHG works fine for either method. I use the LMI jig and HHG. I warm the plates with a heat lamp - I warm most everything that way when using HHG. Anyway, plenty of open time to get the ropes cinched and the wedges tapped in.

Author:  SnowManSnow [ Wed Oct 11, 2017 12:02 pm ]
Post subject:  Re: Cumpiano method for plate joining

Used the tape method on back and top a few days ago. Seems to have worked just fine:) really simple.


Sent from my iPhone using Tapatalk Pro

Author:  Hesh [ Wed Oct 11, 2017 12:20 pm ]
Post subject:  Re: Cumpiano method for plate joining

SnowManSnow wrote:
Used the tape method on back and top a few days ago. Seems to have worked just fine:) really simple.


Sent from my iPhone using Tapatalk Pro


Yup and nothing to store or build either. It reminds me of using go-bars where it's highly possible that way back when long sticks were used in caves as go-bars. Simple is often very effective!

One of the things that I like the most about the tape method is that I can see the entire joint and examine it closely (except under the tape) before calling it a day and having to live with the result.

Author:  SnowManSnow [ Sat Oct 14, 2017 8:52 pm ]
Post subject:  Re: Cumpiano method for plate joining

Hesh wrote:
SnowManSnow wrote:
Used the tape method on back and top a few days ago. Seems to have worked just fine:) really simple.


Sent from my iPhone using Tapatalk Pro


Yup and nothing to store or build either. It reminds me of using go-bars where it's highly possible that way back when long sticks were used in caves as go-bars. Simple is often very effective!

One of the things that I like the most about the tape method is that I can see the entire joint and examine it closely (except under the tape) before calling it a day and having to live with the result.


It appears everything was jointed correctly:) now to wait for my drum sander and take some off to see what the wood will look like:)



Sent from my iPhone using Tapatalk Pro

Author:  Colin North [ Sun Oct 15, 2017 6:42 am ]
Post subject:  Re: Cumpiano method for plate joining

doncaparker wrote:
I'm uneasy about the idea of using hot hide glue with a ropes and wedges jig (i.e., the LMI jig or any homemade version). I am just imagining how much time it would take me to figure eight the ropes and slide in the wedges. But that's just me. Like I said above, the Cumpiano/Natelson method goes really fast after you set up the dry run; probably less than a full minute. I'm happy with my tailored version of it until something better comes along, and nothing has so far.

Heat gun could be used on a HHG jointed top using the ropes and wedges clamping jig to ensure any gelled glue is reheated?

Author:  Clay S. [ Sun Oct 15, 2017 7:29 pm ]
Post subject:  Re: Cumpiano method for plate joining

"Heat gun could be used on a HHG jointed top using the ropes and wedges clamping jig to ensure any gelled glue is reheated?"

Probably- if you were careful and didn't "cook" the glue. Some heat guns run at 1100 degrees F.

Doing a few dry runs with ropes and wedges might give the necessary proficiency for using HHG.

Author:  doncaparker [ Mon Oct 16, 2017 5:44 am ]
Post subject:  Re: Cumpiano method for plate joining

. . . or I could just keep doing what already works just fine, and save my "trying new things" time and energy for a different task that is more in need of improvement.

Author:  Colin North [ Mon Oct 16, 2017 6:39 am ]
Post subject:  Re: Cumpiano method for plate joining

Clay S. wrote:
"Heat gun could be used on a HHG jointed top using the ropes and wedges clamping jig to ensure any gelled glue is reheated?"

Probably- if you were careful and didn't "cook" the glue. Some heat guns run at 1100 degrees F.

Doing a few dry runs with ropes and wedges might give the necessary proficiency for using HHG.

Good point, but my Dewalt is adjustable, goes down to 50 C (perfect for HHG) at the tip. less an inch or two away from it.

Page 2 of 2 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/