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How I cut the top/front taper (lots pics)
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=9546		 Page 1 of 1
Author:  Rod True [ Tue Nov 28, 2006 4:05 am ]
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So I was cutting the taper on the rims at the front on the top last night and thought I would share with you all the way I do it.

Now, I certainly can't take credit for this method, I got if off Charlie Hoffman's website, who says he got the idea from Jim Olson.

Anyway here it is.

Starting with the rims in the mold, I level them out on the sanding rim (I use a flat top, most use a domed top, but this will work for either) but make sure that you have the radius or level on the rims with the linings in place first.

Than I've made up two maple blocks which have the taper of the front bout cut into them (I use 0.75* taper from the front of the sound hole to the front of the body). I double side tape them to the top of the mold with aligning lines I've drawn onto the mold and the block







Next I mark a line on the rims where the line of the front of the sound hole will be.



Next, you have to check and make sure that the body is all the same height off the mold all around, so I check with the ruler and adjust at the head and tail block for front and back height and at the soundhole mark for side to side height. Make sure it's right, double and triple measure to get it right. Tap the rim down in the location that's high to get it in place.









Now tighten the spreaders, check to make sure nothing has moved and your ready to route.

I bolt the router to a sled that runs on the tapered runners. Mark the side of the linings where the line of the top of the sound hole is and adjust the height of the bit till it just touches at the line.





Now you route down along the rims till the taper is cut.

Hope this can help someone out.
Author:  Pwoolson [ Tue Nov 28, 2006 5:17 am ]
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Rod, when I was at Jim's last week, that top design was one thing that I really wanted to get more information about. But we kept getting on to bigger and "better" things.
So, can you explain it a bit? If I'm understanding it right, there are two flat planes. One below and one above the soundhole. The top is essentially bent at the union of those planes. I've seen old mandos that do that and that's the only way I can invision what's going on.
Thanks in advance. Paul
Author:  Rod True [ Tue Nov 28, 2006 9:07 am ]
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You got it Paul.

When I talked to Jim about 5 years ago, he told me that everything below the soundhole was flat, perpendicular to the mold and everything above the soundhole was flat at 0.75* taper from the rest of the top.

So yes, two flat planes.

Charlie's web site explains it pretty good too. Here's Charlie's description, and This is Jim's link about 1/2 way down on the right side, and closer to the bottom on the left side, he mentions the 0.75* break angle for the upper bout.

Jim sure has some very cool and nice jigs hey, I bet his jig set up is luthier eye candy of a different sort.

I know that the "flat" versus "radius" top is and can be a controversial subject, which I'm not willing at all to get into, but there are some notable builders doing it, so I thought that I would do it too, that's all.Rod True39049.7141087963
Author:  James Orr [ Tue Nov 28, 2006 9:46 am ]
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Ron, that's an intense way to cut that taper! I bet it goes a lot faster than
it looks.

Do you mean soundboard tapers? So above the soundhole, the
soundboard is thinned to a .75 degree angle?
Author:  Rod True [ Tue Nov 28, 2006 10:08 am ]
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Correct Jim (it's Rod though )

And it does go very quick, about 5 mins and it's done. Took me longer to write the proceedure than to actually do it
Author:  Joe Beaver [ Tue Nov 28, 2006 10:19 am ]
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Rod,

Very interesting thread but... being slower than most I don't get one thing.

You use the taper blocks and router to cut the taper (or slope) in the upper bout. I get that but how can you attached the linnings first? Don't you cut a fair amount of them away with the router? (sorry if the answer is evident but I just can't see it)
Author:  Rod True [ Tue Nov 28, 2006 10:32 am ]
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Joe, with only a 0.75* taper (slope) it's only about 1/16" of material at the deepest being removed so it's really not a big deal installing the linings first, your not taking much away.
Author:  Pwoolson [ Tue Nov 28, 2006 10:48 am ]
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Joe, you could also scooch them down a bit so that not as much is removed if it is a concern. I'm guessing it's not though.
Rod, I'm quite intrigued by this process. So if you are using a flat top, are you using an arched back? If so, I'm curious to know your reasoning of using a flat top.
Author:  Rod True [ Tue Nov 28, 2006 11:07 am ]
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Well Paul....

I am using an arched back and the reasoning for the flat top is because both Jim Olson and Kevin Ryan use a flat top. Nothing scientific at all, just thought I would copy them rather than the majority of the other builders out there. Thats all.

Of course we could bat around the effects of lower humidity on a non domed top versus the domed top or the greater strength of the domed versus the none domed, but I don't have any answers for that discussion, just a lemming is all I am, mind you, there are only a small handful of builders doing this method granted, they have some pretty nice guitars and a very good following, so they must be doing something right.

I certainly don't say it's the only way, right or wrong, it is viable.

Just the path I've chosen.
Author:  Pwoolson [ Tue Nov 28, 2006 11:14 am ]
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Fair enough. I don't have an opinion one way or the other about flat tops and I'm not trying to move this discussion in that direction. I was just curious if you had a specific reason for doing a flat top and an arched back. You answered the question quite well. And you are right that Jim and Kevin build some decent guitars so there must be something to it.
One of the reasons Jim and I didn't get into it much when I was there is that he hinted toward the fact that he's gotten a LOT of criticism about his tops and he was really sick of fighting that fight.
Author:  Rod True [ Tue Nov 28, 2006 12:45 pm ]
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Yes I can believe that. He is such a giving man and when he has exasperated his reasoning with continual "hounding" it would be taxing on the soul.

So Paul, have you adopted this technique, not the flat top, but the ramped front end of the top? I seem to recall that you were looking for a more predictable or repeatable method of getting the front angle set some time ago.
Author:  Rod True [ Tue Nov 28, 2006 1:21 pm ]
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Cool Terry...thanks for sharing your method.

Yes, the Woolson/Fox jig is the next thing I want to build. I think that will certainly make setting the neck that much easier.
Author:  James Orr [ Tue Nov 28, 2006 4:19 pm ]
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Sorry Rod. I blame it on my sudafed!
Author:  Rod True [ Tue Nov 28, 2006 5:11 pm ]
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No worries Bud, just razin' ya a bit.Rod True39050.0499884259
Author:  JBreault [ Wed Nov 29, 2006 12:19 am ]
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Terry, how did you figure out how high to shim your board?
Author:  Serge Poirier [ Wed Nov 29, 2006 1:09 am ]
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Great tutorial Rod, thanks! Saved to file!
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