The Acoustic Guitar Forum

The Acoustic Guitar Forum (https://www.acousticguitarforum.com/forums/index.php)
-   Custom Shop (https://www.acousticguitarforum.com/forums/forumdisplay.php?f=38)
-   -   McKnight Guitars are coo-coo for Coco (https://www.acousticguitarforum.com/forums/showthread.php?t=528049)

cigarfan 01-03-2019 09:04 AM

Quote:

Originally Posted by Tim McKnight (Post 5936999)
After the vinyl sealer dries for 48 hours we pore fill the peg head and body with a super hard epoxy resin. We drizzle (another highly technical term for Dennis) "a little dab will do ya" on the wood:

Then squeegee the excess resin from the surface of the wood:

The drizzling continues on the sides:

Followed by more squeegee work:

Finally the back is the last surface to experience the drizzle:

And squeegee:

All this technical talk ... I have goosebumps! :)

Tim McKnight 01-03-2019 09:51 AM

Quote:

Originally Posted by cigarfan (Post 5937043)
All this technical talk ... I have goosebumps! :)

Well ... technically speaking ... we call em goosebimples ;)

pandaroo 01-03-2019 06:57 PM

Wow, wow and wow!!

Since your logo is on the fingerboard, so the headstock will be inlay free?

Tim McKnight 01-04-2019 11:31 AM

Quote:

Originally Posted by pandaroo (Post 5937618)
Wow, wow and wow!!

Since your logo is on the fingerboard, so the headstock will be inlay free?

Yes pandaroo, you are correct. That is what our client wanted on this build and we aim to please ;)

Tim McKnight 01-08-2019 07:40 AM

After the 2nd coat of epoxy resin grain pore filler dried sufficiently we sanded it with 320 grit in preparation for the final finish:
https://lh3.googleusercontent.com/-K...=w1207-h904-no









All surfaces are wiped with a tac-rag to remove any surface dust:
https://lh3.googleusercontent.com/8m...Q=w679-h904-no









Then we spray a final coat of sealer over the pore filler on the neck:
https://lh3.googleusercontent.com/n8...=w1207-h904-no


https://lh3.googleusercontent.com/n4...=w1207-h904-no











and over the filler on the body:
https://lh3.googleusercontent.com/I9...=w1098-h904-no




https://lh3.googleusercontent.com/Ys...=w1207-h904-no

ruby50 01-08-2019 07:49 AM

When you sand the filler, do you take it down to bare wood or leave a layer of epoxy on the surface. I have always been curious about why some leave a layer of a fairly dense material that could effect the sound of the instrument.

Ed

ruby50 01-08-2019 07:50 AM

When you sand the filler, do you take it down to bare wood or leave a layer of epoxy? I have always been curious about leaving a layer of fairly dense material on the wood that might effect the sound of the instrument

Tim McKnight 01-08-2019 09:47 AM

Quote:

Originally Posted by ruby50 (Post 5941824)
When you sand the filler, do you take it down to bare wood or leave a layer of epoxy on the surface. I have always been curious about why some leave a layer of a fairly dense material that could effect the sound of the instrument.

Ed

Hi Ed. That's a great question. My first coat of filler will fill 90% of the open wood pores. I sand the first filler coat level to the surface of the wood using 220 grit and this sanding course does expose some bare wood. The second and final [skim] coat of filler covers any bare wood which was exposed and generally fills the remainder of any open pores in the wood or any new pores that were exposed during sanding. The final filler sanding course, with 320 grit, is basically to mechanically abrade the filler to provide a tooth for the sealer to adhere to with a goal of NOT exposing any bare wood.

The trick to the entire filling process is to NOT apply the filler too thick and to judiciously squeegee ALL excess filler from the surface of the wood. As you eluded to in your question, excess filler build up on the surface of the wood would indeed have a negative impact on the wood's ability to vibrate.

I use a 4" wide auto body "bondo" spreader to apply the filler and squeegee most of the excess off with. As a follow up I use a 12" wide rubber window squeegee to do a final removal of any ridges of filler that may be left over from the edges of the 4" spreader application course.

I apply a LOT of downward force on the application spreader to force the filler into the wood pores. The downward force bends the spreader at a 45* angle to the surface of the wood and hardly leaves any filler standing proud of the surface of the wood. This process isn't like icing a cake to leave a thick layer of icing (filler) on the surface. This is more akin to scraping ice off your car's windows so you can see through the glass.

I hope that makes sense?

Tim McKnight 01-08-2019 10:37 AM

Through the magic of time travel, the finish is almost done. Sorry I didn't show any pics of the finish spraying and sanding process but its really rather boring to see repetitive and redundant photos. I have three more coats of catalyzed urethane lacquer to spray and its at this point that I stop and cut the sound port into the sides. I do it now so that I don't get too much finish build up around the exposed edges of the sound port(s).
https://lh3.googleusercontent.com/Bj...s=w679-h904-no










https://lh3.googleusercontent.com/Dg...0=w679-h904-no

ruby50 01-08-2019 12:36 PM

It does make sense. That leaves the question of WHY leave it - why not take it back to raw wood. Does it show off the grain better?

Ed

FLRon 01-08-2019 03:39 PM

Quote:

Originally Posted by Tim McKnight (Post 5941924)
Hi Ed. That's a great question. My first coat of filler will fill 90% of the open wood pores. I sand the first filler coat level to the surface of the wood using 220 grit and this sanding course does expose some bare wood. The second and final [skim] coat of filler covers any bare wood which was exposed and generally fills the remainder of any open pores in the wood or any new pores that were exposed during sanding. The final filler sanding course, with 320 grit, is basically to mechanically abrade the filler to provide a tooth for the sealer to adhere to with a goal of NOT exposing any bare wood.

The trick to the entire filling process is to NOT apply the filler too thick and to judiciously squeegee ALL excess filler from the surface of the wood. As you eluded to in your question, excess filler build up on the surface of the wood would indeed have a negative impact on the wood's ability to vibrate.

I use a 4" wide auto body "bondo" spreader to apply the filler and squeegee most of the excess off with. As a follow up I use a 12" wide rubber window squeegee to do a final removal of any ridges of filler that may be left over from the edges of the 4" spreader application course.

I apply a LOT of downward force on the application spreader to force the filler into the wood pores. The downward force bends the spreader at a 45* angle to the surface of the wood and hardly leaves any filler standing proud of the surface of the wood. This process isn't like icing a cake to leave a thick layer of icing (filler) on the surface. This is more akin to scraping ice off your car's windows so you can see through the glass.

I hope that makes sense?

Tim,
I have always wondered about the grit of sandpaper being used on tonewood. To my way of thinking,320 grit paper is extremely rough and would leave deep scratches, which would then require finer grits to sand out the scratches.

My reference points come from my career in the automotive industry. Various components that have been heat treated for example must be hardness tested to ensure they meet the required specifications. Now, I have considerable experience in polishing small test parts that will be placed under a Microvickers machine for the purposes of determining this surface hardness. These surfaces must be polished to a mirror finish and completely scratch free. I usually start with a 320 grit paper but work my way up to 1200 grit paper and finally a buffing pad to achieve the needed results.

In working with tonewoods, why are you not striving for a completely smooth surface finish before applying the lacquer? Or is 320 grit smooth enough because the wood surface will eventually be covered up? Or maybe itís because you arenít polishing the wood surface, but rather leveling it in preparation for lacquer? Sorry for so many questions, but Iíve wondered about this for some time.

Love your threads BTW, especially the engineering that goes into what you do. Weíre I ever able to have a guitar built, I canít imagine having anyone but you build it.

ruby50 01-08-2019 04:04 PM

FLRon
It has to do with giving the finish something to hang onto. I got this chart off another forum posted by someone who had taken the tour of the Martin factory and saw it hanging on the wall of the finishing shop:

https://www.flickr.com/photos/ruby16...posted-public/

Click the image to enlarge it

Note it says - do not sand with 320 grit on any body that receives a hand rubbed stain

Ed
Very frustrating - can't figure out how to post a picture

runamuck 01-08-2019 04:32 PM

Quote:

Originally Posted by ruby50 (Post 5942363)
FLRon
It has to do with giving the finish something to hang onto. I got this chart off another forum posted by someone who had taken the tour of the Martin factory and saw it hanging on the wall of the finishing shop:

https://www.flickr.com/photos/ruby16...posted-public/

Note it says - do not sand with 320 grit on any body that receives a hand rubbed stain

Ed
Very frustrating - can't figure out how to post a picture

I've been making furniture for 35 years and have built a few guitars. But wood is wood.

The thing about sanding and stain is that the finer the grit, the less texture an oil stain has to grab onto: if you sand 1/2 a piece to 120 and the other 1/2 to 220, the 120 will stain darker. That's true for all oil stains but not so much for analine dyes.

As far as adhesion of wood to finish goes, the claim that 320, or 600 grit, for that matter, is too fine, is a myth. 600 grit is unnecessary that's for sure, but 320 on some fine woods, especially if you're using a random orbital, is going to reduce the chance of fine scratches showing than if you were to use 220.

Hope that clarifies things.

FLRon 01-08-2019 05:47 PM

Thanks! That does help to clear things up. So sanding the wood too fine increases the chance that scratches and swirls wil show through the finish.

Thanks for the link ruby50!

Tim McKnight 01-08-2019 06:05 PM

Quote:

Originally Posted by ruby50 (Post 5942128)
It does make sense. That leaves the question of WHY leave it - why not take it back to raw wood. Does it show off the grain better?

Ed

When you sand the resin filler back to raw wood you expose additional wood pores, defeating what youíve just accomplished. Additionally, the pore filler I use is almost clear but has a hint of amber. If I sanded back to raw wood in a few spots, those spots would show up as different colored splotches under the finish. Donít ask how I know that tid bit of information :cry:


All times are GMT -6. The time now is 07:56 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Copyright ©2000 - 2020, The Acoustic Guitar Forum

vB Ad Management by =RedTyger=