Shaping a Strat Forearm Contour

[carbonti]

Building a partscaster seems at times like using Linux - The process of building or using it forces a participant to know something about it so a decision can be made in order to move forward. Some of the arcane Linux stuff I woudn't care to know but arcane guitar stuff is all good.

Case in point: Forearm contour. Fender used many different cuts for the forearm contour. The Duchossoir book shows 2 production blueprints. Both are different spec, non-vintage cuts and IMO don't look right on a strat. A USACG strat body is also delivered with the modern version of the forearm contour.

The modern version cuts across the lower bass bout ending at the strap pin whereas most of the photos of vintage strats show a much deeper contour ending near where it would bisect the high-e. The black line shows where the USACG cut is and the red line shows where it needs to go.

So I find 50grit paper from a drum sander used to refinish floors with and use it to take off the additional wood to make the contour the correct way as I see it. If anything approaching this coursness of grit is used, be sure to stop well short of sanding to the desired end point because the grit puts deep furrows that have to be evened out with medium & finer grits. These grits are also used to recontour the curve because the fall-away starts from a different angle than before. The end result looks like this.

There's more wood than the lighting shows in the photo in the area of the deepest part of the contour. Then again, some of the photos of vintage strats show a pretty deep cut so depending on the day sometimes they belt sanded a lotta wood.

In any case, the underpinnings of this story might be: Things you don't think you need to know about you won't know about untill you find out, you gotta know about. Forearm contours, knock 'em dead with that at your next dinner party. Thanks for reading.

[phantomman]

I b'lieve you're correct, Bill. An' I think you're well into the "ballpark" for a vintage-contoured body. Many of the MIM guitars (my own included) have that shorter bout relief on the topside. Yours looks right on the money -- or day-amm close!

[Cogs]

The forearm contour angle has been a pet peeve of mine for a long time. USACG makes a great body, but that front contour is off & has been for years. They aren't the only ones, either. Even Fender can't seem to nail it. I had to do the same re-contouring on both my Fender & USACG bodies using 60 grit on a hand-held belt sander.
I'm not sure but you might find the radii on the edge of the body to be 3/8" instead of 1/2", too.

[carbonti]

It's all in the details to whatever degree to focus on and remedy. Agree that parts from anywhere, even from Fender itself, can show spec differences from the vintage strat ideal.

I'm not sure but you might find the radii on the edge of the body to be 3/8" instead of 1/2", too.

Yep, looks to be off so it's 3/8". Any hints on the best way to re-radius to 1/2"? If I don't think I can do it accurately and consistently across the entire body then I'd be tempted to let it pass. But knowing the inaccuracy would bug me so it can't be left alone. Dang, ignorance is bliss...

[phantomman]

I usta be relatively indifferent to the minor variations in the body contours compared to true vintage Strats -- but that was before my custom-built ash hardtail arrived. It looks about as close to spec as any "correct" Fender body can be and the differences between it an' the re-issues from Corona, Ensenada, an' Japan are palpable.

[Cogs]

Some tips for fixing that radius:
*Get some large blocks of wood that are exactly the same thickness as the body, & affix the body & the blocks to a perfectly flat surface (like a workbench) w/double stick tape. Make sure the blocks surround the body in such a way that you can move the router around the body & have it supported at all times. These blocks will keep the router from "falling off" the body.
*After setting the router bit, make a few test runs on scrap to make sure that it is running at the perfect depth. Too low & it will cut a channel around the body perimeter. Too high & it won't really cut anything.
*Difficult areas: ONE- The back of the body where the cutaways meet the neck. This area is kind of tapered by pushing the router into the wood WAY BEFORE THE CUTAWAYS MEET WHERE THE NECKPLATE WILL LAY. If you are not careful you will round over the area & that will be BAD. Here's where you need to be wearing your safety glasses & get down there to eyeball the cut. Don't worry if it's not a "smooth" taper; most vintage Strats aren't very clean in this area & it is one place where the hand-made aspect of older Strats is apparent. Here's a pic of the problem areas:

There should be no problem at all in this same area on the top. Just let the router bit ride into the empty space. The router itself will rest upon the blocks & the body.
Two other problem areas are the rounded edges where the back & forearm contours have been cut from (I'm pretty sire that they rounded the edge before they cut the contours back in the day). There's no wood for the router bearing to ride on so you will definitely cut into the body if you are not careful & that will be another bad thing. You can either sculpt some blocks that fit into these areas to keep the router bearing rolling along the edge, or you can do what I did: Go freestyle & then shape any imperfections in the radius w/a palm sander or a sanding block, & some heavy grit paper. If you are going to do this then you have to move FAST. Be careful not to push into the body or you are screwed. You'll know how Tom Anderson came up w/his nifty "Drop Top" concept. Just move fast while eyeballing it the whole time & keep the bit moving toward the part of the body where there is some wood for the bearing to ride on & you are safe. Always remember that you can sand more wood off if you need to but you can't replace it once it is gone. At least not easily, anyhow.
*After you have the body completely re-radiused, use a piece of sandpaper on a wide block to make sure the surface is flat. Then gently sand the radius. I go back over the top again lightly after that to give it kind of a "crisp" look. You don't want an abrupt edge like you see in that first pic you posted (that's a raw body w/very little finish sanding done), but you want a smooth transition, & you want it to be as consistent as you can get it around the entire edge. Sloppy work here gives the body an uneven & amateurish look & is a dead giveaway that a guitar has been refinished. That's one of the things the big boys look for to indicate if the finish is original on a vintage guitar. After all, you want the thing to look "store-bought".

[carbonti]

As noted by phantomman, the most accurate body I own is the CAR CIJ and that one has accuracy issues as well so my benchmark reference is a little short.

71818 thanks for the walk through on re-radiusing. I will need to review this again in detail. I'm less than confident in going to town on this body with a router.

I'll check back in later when I'm home and have thought this through over a single malt.

[phantomman]

Glenlivets, I trust?

[Cogs]

Back in the '90s the radius was terrible on the USA RI guitars. Once I tried fixing one (it was nerve-wracking, believe me) I decided that EVERY project of mine would have this done.
It's one of those things you wish you didn't know; but because you do, you notice it right off.

[phantomman]

Ayup. It's like the upper bout radius goin' into the neck pocket on a late model Tele.

It's hard not to be anal-retentive once you know what you're lookin' at an' what it's s'posed to look like.

(they say "ignorance is bliss", Robert)

[carbonti]

A dram of Laphroaig to bring me to my senses.

Viewed as a rational decision, recontouring the rollover radius from 3/8" to 1/2" is not doable for me. I'm not setup to do this with the precision needed for a successful outcome. A strat body is 1 3/4" thick and I can't create with enough precision a 1 3/4" surrounding platform to circumnavigate a hand held router.

As doing this is not a rational undertaking, I'm not quitting yet and will look into 1 more thing: Rent a table router for a few hours. If I can rent the tool I'll only need buy the 1/2" roundover bit. This method should be more accurate and controllable than a hand held router.

To be continued...

[carbonti]

There are no rentals for router tables. So my partscaster build will have to look like all the other strats in the house in the finer details. I'm all for pushing the envelope on getting the details right but for this reworking of radii - maybe next time.

I'm really more of a tele player - what did you guys say was wrong with USACG tele contours?

[Cogs]

Absolutely nothing. Tommy even puts the "router's hump" in the cutaway.
BTW- I don't think a table would help anyhow. I'm not sure about this but I think the fence would prevent you from getting the bit inside the waist on the body.

[carbonti]

Good to know there is not a hidden side project to do the tele.

As far the router table, I thought the fence could be removed so the table could be used as a shaper, dunno never used a router table before. Y'know, I was gonna build the support platform for the router around the body with scrap shelving using elevator bolts rigged to allow height adjustment to the 1 3/4" of the body face. Sounds nuts thinking up this stuff but workshop time is therapeutic. That's what my psychiatrist tells me.

[Cogs]

I told my psychiatrist, "Nobody takes me seriously."
He said, "You're kidding."

[Wilko]

I went to my shrink and said, "Doc, you gotta help me. I feel like I'm invisible"

He said "Next!"

[Cogs]

I told my psychiatrist that all my peers belittle me. He said, "Don't be stupid!"

[Wilko]

My psychiatrist told me he thought I was crazy.

I told him I wanted a second opinion.

He said I was ugly, too.

[Cogs]

We need this:
http://instantrimshot.com/

[jerryjg]

Some tips for fixing that radius:
*Get some large blocks of wood that are exactly the same thickness as the body, & affix the body & the blocks to a perfectly flat surface (like a workbench) w/double stick tape. Make sure the blocks surround the body in such a way that you can move the router around the body & have it supported at all times. These blocks will keep the router from "falling off" the body.
*After setting the router bit, make a few test runs on scrap to make sure that it is running at the perfect depth. Too low & it will cut a channel around the body perimeter. Too high & it won't really cut anything.
*Difficult areas: ONE- The back of the body where the cutaways meet the neck. This area is kind of tapered by pushing the router into the wood WAY BEFORE THE CUTAWAYS MEET WHERE THE NECKPLATE WILL LAY. If you are not careful you will round over the area & that will be BAD. Here's where you need to be wearing your safety glasses & get down there to eyeball the cut. Don't worry if it's not a "smooth" taper; most vintage Strats aren't very clean in this area & it is one place where the hand-made aspect of older Strats is apparent. Here's a pic of the problem areas:

There should be no problem at all in this same area on the top. Just let the router bit ride into the empty space. The router itself will rest upon the blocks & the body.
Two other problem areas are the rounded edges where the back & forearm contours have been cut from (I'm pretty sire that they rounded the edge before they cut the contours back in the day). There's no wood for the router bearing to ride on so you will definitely cut into the body if you are not careful & that will be another bad thing. You can either sculpt some blocks that fit into these areas to keep the router bearing rolling along the edge, or you can do what I did: Go freestyle & then shape any imperfections in the radius w/a palm sander or a sanding block, & some heavy grit paper. If you are going to do this then you have to move FAST. Be careful not to push into the body or you are screwed. You'll know how Tom Anderson came up w/his nifty "Drop Top" concept. Just move fast while eyeballing it the whole time & keep the bit moving toward the part of the body where there is some wood for the bearing to ride on & you are safe. Always remember that you can sand more wood off if you need to but you can't replace it once it is gone. At least not easily, anyhow.
*After you have the body completely re-radiused, use a piece of sandpaper on a wide block to make sure the surface is flat. Then gently sand the radius. I go back over the top again lightly after that to give it kind of a "crisp" look. You don't want an abrupt edge like you see in that first pic you posted (that's a raw body w/very little finish sanding done), but you want a smooth transition, & you want it to be as consistent as you can get it around the entire edge. Sloppy work here gives the body an uneven & amateurish look & is a dead giveaway that a guitar has been refinished. That's one of the things the big boys look for to indicate if the finish is original on a vintage guitar. After all, you want the thing to look "store-bought".

Whoa!! Absolutely brilliant attention to detail!