Top Plate thickness?

[Pat Comeau]

Here's another question...i received some endplates from Scott and it only has 5/8" high from where the top plate sits from the top of the endplate, will it make a big difference in sound instead of 3/4" thick wood top plate?, cause if i use a 3/4" top plate it'll be 1/8" higher than the endplate and i would like to have it flush with the endplate cause i think it would look better.


Pat C.

[Allan]

Can you post a picture of the inside of the plate? I am guessing that you are talking about a flange or something being higher than you would like?

Allan.....

[Pat Comeau]

Here's what i'm talkin' about....

[Bent]

Pat, Get the plate changed so it will hold a 3/4" top. Anything less and you would invite cabinet drop and all those goodies.
That is unless you build a steel out of aluminum . Then the wood don't matter much other than for decoration.

[Pat Comeau]

Bent...i was thinking maybe just weld and build up the top 1/8 " to make it 3/4", what do you think?, me i think it would be easyer that way .

[Bill Ladd]

You could also extend the top plates (decks) above the level of the end plates, like a 'Bud round front.

edit -- Oops, never mind. Should always completely read the first post before I reply!!!

[Allan]

I don't feel that making a 1/8" rabbit at the ends of the deck would add anything to cabinet drop. Keep the length of the rabbit strictly to the width of the flange and I feel you will be OK. From a structural point of view, the connection between the deck levels and the skirts is much more important and if they are done correctly you will have plenty rigidity.
Can you tell which builder made the end plates and then possibly get a look 'up the skirt' of one of their instruments to see what they do?

Allan.....

[Scott Howard]

Pat

I had planned on shaving the very end of the boar down to 5/8" and the the bottom would be about flush with the endplate when mounted . You could use the thicker board but the last 1" or so of the top be cut down to 5/8" . I can draw out what I am thinking if I need to later. This would be the easiest fix . I was told by one person that they are JCH but could say for 100 % .

[Bent]

Allan, in keeping with your sense of humor, a rabbit is an animal that goes hippety-hop. A rabbet is a cutout on wood. (there, I'll quit being difficult for now)

I could be wrong on this point but I feel that "the weakest link" applies here. One part of the board that is milled down to a smaller size, makes this its weakest link.
IM not so HO. Pat, if you can possibly move the ledges down a 1/8 of an inch, I would recommend you do so. Don't know if you can, considering the placement of the changer window right below the ledge. Welding a bead on top, would invite warping due to excessive heat. Aluminum is sensitive to this.

Recently I saw the results of too thin materials used and the results. The Dekley I worked on has a 1/2" pakkawood top deck. This had been milled out for placement of the changer mounting blocks underneath(1/8" grooves) plus about a 1/16" rabbet all around the outside perimeter to receive the outside aluminum ledge. It is hard to say what caused the cracking since this guitar had been over-stressed due to heavy modification. But the end result was this: A crack, right down the middle of the top, right from the changer hole clean thru to the other end. The crack followed every screw hole and notching.

This is not to say that the Dekleys were sub-par. These were very solidly built guitars, with their aluminum frames, so the 1/2" top maybe didn't matter that much structurally.

So, with a wood top that is expected to carry the whole load, I would notch out that piece as little as possible.

[Allan]

Rabbit/rabbet - LOL Yeah, that's an example of me relying way too much on my speel chucker. When I use a wrong word, that is still a word, it just doesn't help me out at all. Stoopid thing!!!

I can understand your concern regarding reducing the thickness of the wood at the ends, or indeed anywhere. I am speaking only while wearing my structural engineers hat. I don't want to get into a way deep discussion on this because I can't put numbers onto it. However, I do know that if you were to reduce the stresses in the body of a steel guitar to a pin joint analysis, centered around the skirt attachment points, with the skirts treated as an anti-buckling (stiffening) component, you would find that flexure is not significant at the ends of the deck. The flex does not happen in that last small length. The fulcrum points are there and the flexure can only take place inside of those. In this case, the load at the fulcrum is mainly torsion and tension (longitudinal in both cases). Now, I am aware that a full blown pin joint analysis (Bowes diagram, the works) can not be done due to the structure not being composed of triangular elements but the words associated with that kind of analysis will still work for this discussion since they are in common usage. That is why I am saying that that I can't put numbers to it. But try this - think of the metal bridges that you have seen in your various travels. Remember how they all taper down at the ends? The stresses, caused by movement and flex, in a structure of this nature, are not concentrated at the ends. A girder bridge, with the roadway at the bottom and the trussed girders along side you as you pass through it, bears many of the same loads (different magnitude) as a steel guitar. (an upside down steel guitar that is!)
In the 'short section' of a box girder the top member is the compression member while the bottom member is in tension (assuming top loading). The PSG bodywork forms an inverted 'U' girder which is a box girder with the tension member removed. The analysis is much more complex but the top remains in compression with the tension being thrown more onto the side members (the skirts in this case). So, as I said before, I can not put numbers onto this, but, with a properly attached set of decks and skirts, I would not PERSONALLY worry about rabbeting the extreme ends to suit the castings as they exist. If worry remains, simply cut a metal support piece and attach through it, through the casting and then into the deck.

I don't have HUMBLE opinions, just opinions! Gawd, I don't like me sometimes! Opinions will vary, but, at the end of the day, you need to make up your own one (and generally live with it for a while) so go with what ever carries the greatest comfort factor.

Regards, Allan.....