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As I finished gluing on the top bracing on my WRC top this evening and was admiring my work, I realized I should get some clarification prior to gluing on the top. The top of my rims are level from tip to tail as shown on the plans. But in checking the radius this evening, I noticed the following:


Notice that I have the tail of the soundboard along with the waist supported by three shims. This ensures the top is level around the lower bout. When I set my 28' radius on the top, all looks well except the top sloping down 1.5 degrees towards the neck leaves the top sitting about an 1/8th below the plane set by the tail and waist shims. If I put the shims under the neck area and push down on the soundboard to get contact at all four sets of shims (which would happen if I were to glue the top on my level rims), the area under the fingerboard extension goes from having this nice 1.5 degree slope to practically flat. The plans show that the top should be sloping 1.5 degrees at this point. As my neck joint is also set up for a 1.5 degree slope, I somehow need to fix this. In my previous two OM builds with 28' radius tops, I sloped the rims. But the SJ plans do not show the rims having any slope. I am concerned about taking material off the rims to get the 1.5 degree slope as this will lower the neck relative to what is shown on the plans, making me wonder about a potentially high action.

Maybe it is just understood that I should slope the rims, but I want to check before doing anything.

Many thanks,

Ken

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Ken,
I have built several of these. I have done the radius thing on the rim and I have made it flat, with the 1.5 degree angle sanded into it. Both ways work well currently, I prefer the flat top with the 1.5 degree upper bout. I also build with a 18' radius.

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Thanks Gents for the responses. As the top was built with bracing radiused as shown on the plans, I think the best approach is to slope the top of the rims on the upper bout. Steve, you mentioned this is your favored approach. Do you have any issues with the plane down the fingerboard to the bridge as long as the neck is 1.5 degrees? Sounds like it should work.

Todd, I'm not totally clear on your approach. Do you radius your x-bracing to 25' as well? And are the rims on the upper bout left flat even though you radius the lower bout? I can sort of see how those could work as the rims would be lowered at the tail, bringing the top at the upper bout down in contact with the rim. Never thought of doing it that way.

As I wasn't exactly sure how to tackle the top, I glued the back on first. Don't normally do it this way, but I didn't see any harm in it. This is where I am so far:

The x bracing and tone bars look a little fatter than they actually are. They have a pretty steep peak to them, the tone bars especially. The top is WRC. When I tap it, I get a pretty good ring, so I hope I am close.

Thanks again,

Ken

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That should work. Of course the normal fine fitting of the neck and fingerboard extension will be needed

Is this what you want? I tap tone with the top on. I would think that a good ring would be too stiff. Perhaps you want to take it a bit past that point knowing that the top will more stiff when attached to the rims. This would make a great thread subject......

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I have no idea. I didn't want it sounding like a 2x4. I think I have succeeded with that . I am sure there are a number of threads out there on this already. I have only built a couple of guitars and this is my first with WRC. The whole tap tuning thing is little out there for me. Not having access to dozens of tops makes getting a feel for this a little tough. I see maybe two tops a year.

Ken

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I've built 5 WRC toped guitars and all of them had braces that were lower than yours. I'm sure you went off the plans which is fine, but I also think you can take them down some more.

Here's a picture of the last one that I built, maple WRC to boot. I wouldn't suggest going this low on the lower tone bars (and I'd want to put some back, but it was a good learning experience) but it shows you the lower end of things. I listen for long, low drone notes when I tap. I also made this one for finger style so it's a little bit to loose, but only by a little bit.

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Thanks Rod and Todd for the input. This SJ is certainly the heaviest braced guitar of the three I have built. I scalloped the braces on both my OM's. The OMC has a very nice sitka top and has beautiful tone with great sustain and wonderful overtones. I am hoping it wasn't just beginner's luck. I braced the second OM the same way, but it hasn't been strung up yet, so I have no idea how it sounds. It has a red spruce top. The SJ is entirely new as is the use of cedar. I figured I should brace per the plans. But you both seem to have a fair amount of experience, so I'll skinny up the bracing. I am building the guitar for my Dad who is mostly a strummer but mixes in a bit of picking. He doesn't play hard. Mostly uses the guitar as background for singing.

Can you provide a little more guidance? My x-braces are 0.31" thick at the base and 0.61" high. About half way up, I carved a sharp taper so the brace narrows considerably at the peak. The tone bars are 0.26" wide and 0.77" high. These also begin to taper about half way up and are even more pointed than the x braces. No scalloping at all. You can see how the braces taper off towards the side. Do I lower the height of the tone bars or x braces? Scallop? How much? I'd like to string the guitar with light gauge strings.

Rod, did you find your spray gun yet? We now have warmer weather in Michigan so I should be able to get mine going again and get the OM sprayed.

Ken

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Hey Ken, I found the gun I want, just need to sell a few things (time to list on the classifieds) to pay for it.

That top I posted is strung with light's.

I make all my top braces 1/4" wide on all my guitars, but for the two upper face braces. Some will say that is too thin for a larger body, but the 16" guitars I've made have all 1/4" and all sound pretty good (at least their owners think so). I also don't make them higher than 9/16" (0.563") at the center of the x-brace. My lower tone bars are not higher than 1/2" and as you can see, they don't stay that high for much of the brace though.

It's sort of tough to give guidance based on pictures because no two pieces of wood are the same. Stiffness in the same billet of wood can vary let alone from one tree to the next, and than there's one species to the next. One really has to have the piece in hand to feel it, tap it and flex it to see where it stands (in relation to one's past experience and understanding), but I'll give you some of my thoughts on it.

If I were making that guitar there, I would lower the height of the x-brace a bit and keep the taper all the way down to the rims and just leave 1/16" to tuck under the liners. I would drastically reduce the tone bars down to 1/2" high and taper those both down to nothing just before the rim and almost nothing at the x-brace. The other thing you can do to keep stiffness (good thing) but remove mass (bad thing) is to taper the cross section of your braces. You can make them like this /\ where it is triangular or you can make them more of a parabolic shape (not really a parabola, but that's the image which fits the shape) and taper them length wise.

I think making these changes will render you a fine sounding guitar and one that you shouldn't have any issues with.

This tapered style of bracing, generally speaking renders a more pronounced tone and good separation of the notes, with not so much overtones. The cedar will add a warmth to the tone and the maple will add just a bit of brightness. I really love my cedar/maple guitar and would certainly build another.

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<Shaking my head> Here we go again. first the area (volume) of the SJ is considerably more than an OM. if I weere at home I have the differance in volume.

Ken the gap you see is is caused from the X-Braces flatting out at the lower bout because they are thinner there. as far as sanding the dome into the rim top I have done it both ways but I no longer sand the dome profile into the top of the rim. I have some 30 built with pure flat top of rims, not one seam failure. yes i have to ever so slightly force the top to contact the flat linings but I have had no issue. Foggy Bottom and others do exactly the same thing. this is your choice. i like to work with the true flat rim on the top side but this may bother you or other.

Think of the plan as a guide more than a hard and fast rule Ken. Everyone does things a bit different to arrive at the same general outcome.

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What does that mean? You need to explain yourself, we can't read your mind. What is this referring to?

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"There's really no wrong way, as long as the results are what's desired." Charles Fox

"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman

"Generosity is always different in the eye of the person who didn't receive anything, but who wanted some." Waddy Thomson

Yes liner area is close I was speaking of sound chamber volume. So yes the area of the tops are close .

Fine

both time I took it you were speaking of volume not surface area. that was my bad in either case I never took offence was just responding that there was a lot of differance in an OM and my SJ based on typical specs. you are right the top surface areas are close.

In regards to the neck angle issue using a flat plane for the top rim and a flat UTB. One must notice that the neck block detail on the plans has a 1.5 degree FB extention flange that the top will glue to. this elimenates any need to sand the top to avoid the 14th hump. If you choose to not use a neck block with such FB extention support then it would be a good idea to pre plan for a top profile that produces a 1.5 degree pitch at the FB extention.

In regards to tapering the the upper legs of the X-brace I do recommend following the plans as shown with stiff spruce tops. With a WRC or redwood top I start the taper a bit closer to the upper bout typically by about 1/2" to stiffen the area around the lower sound hole and waist some.

Thanks Michael. My mistake for not looking at the neck block detail on the plans. My neck and block came from Hanalei Moon, and as the block has no fingerboard extension, I'll go ahead and slope my upper bout.

The OM's I have built have had a 1/8" x 1" brace on the neck side of the UTB to reinforce the top under the f/b against cracks. I don't have my plans here with me, but I don't recall that piece being on MP's plans. That is likely due to the neck block configuration Michael is using. I also presume that if the f/b is not glued to the top, this extra brace is not really required even for the neck block I have. I am still debating whether to float the f/b or put a pocket beneath the top so I can bolt on the f/b extension. I am leaning towards the latter. I need to hurry and make up my mind so I can get the top glued on.

Ken

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For future referance you can ask Chris at HM to provide the Michael Payne neck block if you wish. he has the specs for my necks. The angle on the flange is not pre slopped but that take 1 min to do by hand.

At present I do glue my extension to the top but am about to move away from doing so and go to a bolted extension. You are correct the flanged neck block did away with the upper transverse graft. I never used the A-frame popsicle stick method but use to include a 1" wide x 1/4" thick upper transverse graft between the upper transverse brace and neck block.