A couple of build questions

[Bob Schmidt]

I am building an archtop guitar shaped octave mandolin and have a couple of questions.

1. I read in Robert Benedetto's book that he puts a sealer coat on the inside to help against rapid humidity changes. Is this common practice?

2. I have seen videos of reinforcing the F holes with gauze and glue. Wouldn't this change the response of the top. Are there other ways of reinforcing the F holes, and is it even necessary?

[Bill McCall]

Interesting questions.

1. Some folks do, but not common AFAIK
2. a. Yes, the response will change. Whether you can hear it is another matter.
b. I'm sure there are other ways to reinforce, like veneer.
c. Probably not.

[Rob Roy]

Sealing the inside of the instrument to slow down humidity change makes sense but it's never traditionally been done in the violin or archtop world, not sure why.

Gauze reinforcement of the F holes may prevent a crack if the instrument takes a sharp blow in that area, but again, very few builders bother with it. How often do you see damage to an F-hole?

Please post a picture of your build. I love the sound of the GOM but there's precious little out there in the specifics of their construction.

[Bob Schmidt]

The build is still in progress. The back and sides are together, and the top is carves to a uniform 0.2" (~5mm) which is what prompted there questions. I am ready to put the F holes in the top and glue it on. I have another top that i carved a bit too thin so I decided not to take a chance with it so I have done a second one. They currently tap quite a bit different, so I thought I would take some time to compare them. I am quite new at this and am not sure what to look for in the tapping process, but it seems a good opportunity to at least compare how 2 different but close to identical pieces of wood behave.
I will be in the shop later today so I will take a couple of pictures and post them in this thread.

[sunburst]

Sealing the inside makes some internal repairs difficult to impossible when things go wrong, it is of debatable and minimal value, and most of us don't do it.
Gauze "reinforcement" of f-holes does not prevent cracks and it makes repairing them much more difficult. My opinion is: there is no advantage, only disadvantages for repair.

[peter.coombe]

+1 What John said.

[Bob Schmidt]

Thanks everyone. It appeared to me that these things were not done in general, but it is good to know why. I hope to never have to take it apart, but building with repair in mind makes sense. Your help and experience is a terrific asset.
Here are a couple of pictures of the ongoing project. The top is almost ready for the F hole placement. Is there a good way to prevent the drill bit from tearing the exit point on the curved surface?