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Long weekend = box close-out fun....RIGHT!!!!

The back and top are built up and ready to be fitted to the rim.

The back is fitted just fine...just need to add some of the kerfed-feet over the brace ends.

The Top is a different story...Turns out that my top (which I got for a song as a Martin factory second) is cut pretty tight to the final dimensions (NOT alot of overhang here) So when I position the top on the rim using the alignment pins (references the top to the rim and helps reference the finger board)...the top is too narrow just above the lower bout (or below the waist where it flares out to form the lower bout). In this area (both left and right sides) have about 3/32 of rim showing where I shouldn't. I plan on using 1/8" thick binding with about 0.040" of purfling so I think that I am ok...but...I really feel like I'm just cutting it close.

Any idea on if I should shim the rim in the mold to bring the sides in abit to cheat it??? OR do I just fit the top and leave the mis-match and "hope" i'm really good at fitting the purfling and binding???

I'll take any ideas at this point...

I'm sure that I'm not the only one to have a top pre-cut too small...so hopefully no one is too imbarassed to admit it.

Thanks for your help,
JP

PS: I guess this is what I get for using a factory top...big manufactures are always going to keep things trimmed really neat to save on scrap...I just couldn't help myself from a great deal on this top...I guess...pay me now or pay me later...

   If it's a factory top, it should fit the intended guitar model.

Sounds maybe like your sides are flared open a touch. Have you checked if these are square? Has the back been glued on for a long time? I ask because on my first, I had glued on the sides to the top and taken a long vacation from building.   As a result, the sides had time to start flexing on me.

   3/32's is not much. Maybe you could just push the sides in a bit to take up some of that space, if not all. You could probably cover the gap with the binding/purfling, but like you said, you won't have much left to spare.

   Heaven forbids, but what if something happens while you're routing the binding channel and you have to excavate a wider channel than expected to add an extra purfling (ask me why I thought of this example... ) You'll be happy for the extra 'meat' in the kerfing area then...

   Hope this helps,

AlAlain Desforges38865.3916666667

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I'd like to be able to prove, just for once, that money wouldn't make me happy...

JP,

It sounds like the outside width is not the problem but more like the lower bout curve doesn't match curve on the top.

Using the purfling to make up the difference could be a problem since, if I understand your problem correctly, there won't be any top wood under the purfling. That would leave little or no top wood in contact with the linings. I wouldn't count on the purfling to provide the strength lost.

Are you using a form? If so, perhaps a little judicious shimming to coax the sides into a shape closer to the top's shape would help.

I have six Martin reject tops. I'll be extra cautious when I use them.burbank38865.5488657407

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now known around here as Pat Foster
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http://www.patfosterguitars.com

Yep, that's what I experienced with my StewMac top. It was cut TIGHT, and there was NO room at the inn, so to speak.

Alain is exactly correct. My problem was that my sides weren't matching the pattern properly. They had just the slightest bow out. Once that was corrected in the mold, the top fit properly, tight but properly. AND, even then, there was a small gap that the binding covered up perfectly, so it wasn't an issue.

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Eagles may soar, but weasels don't get sucked into jet engines.

Thanks for the replies...I've decided that I probably can shim the mold such that the sides are brought into the top. Plain'ol cardboard should do the trick.

My mold is pretty much dead on (some minor nicks on the interior profile. I think this all came about using 2 different sets of plans (I built the mold from a set of dreadnought plans purchased from a good vendor won't name names...) but...then got the Martin plans (AND top) while on a trip to Nazareth visiting family.

Looks like my mold is just a bit oversized from Martin specs in the lower bout on top of having the rim out of the mold for 3 months (not the brightest move)

I'll check into the oversize and decide if I'm going to re-work the mold for my next build...shouldn't be too hard to do...cut a template 1/8 oversized...router the mold and then bend some 1/8 sheeting to shape and glue to the interior.

Thanks again,
JP

[QUOTE=Dread1916] shouldn't be too hard to do...cut a template 1/8 oversized...router the mold and then bend some 1/8 sheeting to shape and glue to the interior.

Thanks again,
JP[/QUOTE]

JP, i don't mean to hijack your thread but i would have a question that really needs an answer! That sentence made me think about the crack that occured on one of my sides, do you guys always cut your templates 1/8" oversized to build the body mold? That alone could explain a great deal of what happened to me.

Thanks in advance !

Serge

Serge

To be 100% accurate I do the following when making forms and molds.

1. My half template is made to the exact size of half the guitar (When cutting out the profile of the top or back I always stay well outside the line).

2. I make my mold to conform with the half template.

3. My bending form is made 2.0mm all round undersize to allow for the thickness of the sides. Some people compensate the bending form more at each end to allow for spring back, personally I don't do this as I take my sides through two drying cycles and clamp into the mold whilst still hot. I do own some pre made forms and they are compensated.

I suspect you are right that if you made everything the same size, you probablly got too tight in the mold and caused your crack.

Hope this helps

Thank you very much Russell, it makes plenty of sense and you potentially just saved me another crack for my 3rd build, i'm just gonna reduce the bending form by 2 mm and will probably be ok next time!

The two drying cycles before clamping to the mold is something i did too so i feel confident that it was just my mold that was a bit oversized.

thanks!

Serge

Yeah yeah Grandpa, excuses, excuses!

No problems with your question here Serge...glad this may have help ya...I know that I...WISH...I could have known about this forum prior to making my mold...Its pretty close...so I'll probably just leave it alone and be sure next time to have a top and back cut oversized enough to compensate.

The top is 90% fitted..i'll be finishing this part up today. Then its time to replace the kerf feet over the braced portions on the top and back...THEN...I can finally get this baby closed up.

I think that since the top has less overhang than the back...I'm going to attach the top first and then add my Kerf Feet (so I get better compression from the Kerf Feet to the top braces...the back to follow.

If the humidity is lower than it was when the back braces
were glued on, the consequent shrinkage can cause the sides
to open up at the top.   Carey