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I am thinking of building an all-koa jumbo 12-string.

Knowing that there is significant more force from 12-strings than 6, I have been doing some research to try to learn as much as possible.

I stumbled onto a website that sells plans that are based on existing guitars.

Here is a plan they say is similar to the Taylor Jumbo 12-string. http://ultimate-guitar-online.ultimate-online-services.com/zencart/index.php?main_page=product_info&cPath=1_14&products_id=20

Have any of you used something like this for a starting point?

Just wondering how accurate these things are.

Thanks

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P A U L B U R N E R
Burner Guitars

Have I used these plans? No! I have used others in the past. What I have always found out about plans is they no matter how good they look they lack something. Scott Antes plans are pretty good he has a lot of various plans on many different instruments but many of them the measurements are not dead on compared to the actual models he is basing his plans on. Maybe it has to do with copyright and patent laws and not directly wanting to copy these instruments 100%. I don't know. Michael Collins plan on the J-45 is great. He covers a lot of detail. Many of the G.A.L plans and others leave a lot to be desired. They leave you guessing. I checked out your website and you are building some nice guitars. Instead of using a plan that may or may not be right I would do a little more research on bracing patterns for 12 strings and try to adapt a style you have already built to a 12 string....Mike

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Another day, another dollar.

Actually I've been looking at the same site over the last couple of days. (12 fret dread)
Does it really matter how "accurate these things are"?
If you like the shape/proportions of a plan, I can't think of any reason not to use them, unless someone has asked for an exact copy of something which is patented.
Just go for it, but just check how the mechanics of it work out first of course, (e.g. machine head layout/string clearance with head-stock shape - easily changed)
Things like bracing patterns and sizes etc. can be detailed on a plan but, even if faithfully measured from an original guitar, will still be only a guide, as you say a "starting point" for a build.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Mac Rostie plans are better check out the Guitar of American Luthiers , Antes plans are so heavy and over braced. Agree that all plans seem to be missing something . Mac Rostie plans were the as good as I have seen out there.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I can't speak for the 12 string plans, but I just looked over some of the 6 string plans and they're nothing like the actual guitars they represent.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Actually the MacRostie plan is pretty close to the guitar ( Martin HD 28 ) . Also you have to look at the guitars being drawn . Many examples were of hand made guitars without patterns or jigs so there may be honest variability between the samples . Production instruments may intentionally changed for copy write reasons.
As a toolmaker never assume that the print you buy is a true scale drawing. Blue prints are representational drawings, this means they appear to be what the represent but are not scale. Unless it is marked SCALE drawing assume it is a full scale drawing . They are different from each other. Prints will be in sizes a scale drawing will be an exact drawing a full scale drawing is one that is full size but not true scale so go by the numbers on the print not the actual drawing. While the shape may be close do not assume it is perfect.
Also If you have a copy or a plotter drawn print. Copies are often stretched from the copy process . Plotter made prints are more accurate but again go by the numbers do not assume the print is correct . ( It may be ) but it may not.
Just a heads up for you guys

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Like John has mentioned the very first plan I bought years ago from stew mac was the Martin HD 28 MacRostie plan. It is a great plan. I also own his mandolin plans. These are some nice plans.

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Another day, another dollar.

Thank you ALL for your input - it is so great to have a community of builders with experience WAY beyond mine!

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P A U L B U R N E R
Burner Guitars

Paul, I have built two twelve strings and own another (I'll come back to this). I have also measured a bunch of them and did purchase the Ultimate plans referenced above. In my opinion, they are very similar to Taylors standard models (not the LKSM) - and have some of the features that Taylors uses including thicker top plate, third tone bar, non scalloped braces. If you want to make a Taylor clone that would be a very good starting point.

There are many questions that I think should be answered before starting a 12 - how do you plan to string it, tune it and play it? With "normal" light guage 12 string sets at concert, you are looking at approximately 50 percent more top tension. If you want to tune down, which many players do, obviously the tension goes down unless you increase gauge or scale or both. So I have an old Martin D12-28, short scale, big fat dread body, tuned to D# with 10's, an OM bodied long scale (25.4) strung with 12's and tuned to D and a very long scale ladder braced 000 with cables tuned in the cellar - each one a very different guitar. I think Taylors tend to be very good overall guitars when tuned to concert, but they often get kind of muddy when down tuned (unless it is the LKSM which is a totally different critter).

It is also interesting to see what people do to brace a 12 - my Martin has exactly the same 5/16 bracing and top thickness as an unscalloped D28 (larger bridge plate), where Taylor adds the third bar and thickens the top. I followed Taylors lead on the OM 12 - the smaller body makes it a wonderfully balanced finger picker. Unfortunately there aren't a lot of 12 string plans out there so this might be your best starting point.

Freeman - sounds like you'd be a good starting point

I'll shoot you a PM soon.

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P A U L B U R N E R
Burner Guitars