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https://luthiersforum.com/forum/viewtopic.php?f=10101&t=50960		 Page 4 of 10
Author:  banjopicks [ Tue Sep 17, 2019 8:08 am ]
Post subject:  Re: Build started
Disaster!!!! wow7-eyes oops_sign idunno I somehow managed to do this when I clamped the brace in. The reason was that I found a couple of spots where I hadn't clamped or didn't get enough glue or something so I added some glue and reclamped. I remember hearing a tick but I didn't see anything wrong until I took the clamps off this morning. I guess I'll be removing the braces and fixing the crack. I'll be sure to use my go bar deck for braces in the future. [xx(] [headinwall]
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Author:  SteveSmith [ Tue Sep 17, 2019 10:05 am ]
Post subject:  Re: Build started
Tough lesson - we all get them from time to time. At least it's repairable.
Author:  Ken Nagy [ Tue Sep 17, 2019 10:37 am ]
Post subject:  Re: Build started
I may be a hack, but it seem that just wiggling some glue in the crack between the brace and the sound hole would be plenty enough to fix that. With the braces there, it isn't going to crack anymore.

Clamps are VERY EASILY over tightened. A screw can put incredible pressure on things. Finger tight is enough. Often I don't even use clamps. Hold with fingers until it sets, and set aside. Gluing braces would need clamps. But some things don't.

It seems like there was just a gap. Was it buzzing? Some thick glue, like Epoxy or something could fill the gap without clamps or anything. Even without the glue that gap might not have been a problem; the clamp was the problem.

Yesterday, I split a violin peg I was making just by tapping on the back that was in a fixture in the chuck jaws with a hammer to try to true it up, while the end held with the center. The center was maybe 1/16th" deep, just a poke with an awl. No fixing that. About an hour and a half to make a new one. I didn't beat on that one.

Ken
Author:  Joe Beaver [ Tue Sep 17, 2019 11:05 am ]
Post subject:  Re: Build started
I hope it is not as bad as it looks. That is a beautiful top, and well-done rosette.
Author:  banjopicks [ Tue Sep 17, 2019 11:26 am ]
Post subject:  Re: Build started
It's got a big hump there so gluing the crack won't help IMO.
Author:  Clay S. [ Wed Sep 18, 2019 6:45 am ]
Post subject:  Re: Build started
You could put a spruce reinforcing ring around the soundhole just inboard of the edge and use a caul to hold things flat during glue up. That might take the "hump" out of the soundhole and reinforce it at the same time.
Author:  banjopicks [ Wed Sep 18, 2019 7:44 am ]
Post subject:  Re: Build started
I took the braces off and glued the crack, reinstalled the braces and it looks OK now. I just need to forge ahead.
Author:  banjopicks [ Tue Jul 07, 2020 10:07 am ]
Post subject:  Re: Build started
I have had a lot of distractions over the past year and just moved into a new house with a nice large basement. So I'm moving ahead again and here's where I'm at.

I don't have a GO-Bar deck yet but I wanted to get this box closed so I went the old fashioned way. I didn't want to have to worry about glue time so I didn't use hide glue, just regular Tite_bond. I feel I just need to get guitar #1 done so I'm taking those shortcuts for now. The center lines moved a little and I need to find a better way to lock it in place before clamping in the future.

I don't plan on using lacquer for the finish either. I'm going to use shellac applied with the french polish method. I'm done with the nasty finishes and if it wears quickly, so be it. Shellac is very easy to touch up. I would like to commit to doing all my instruments this way from now on.

Things should start moving along quickly now. I have the neck almost complete, the fretboard is done.

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Author:  bcombs510 [ Wed Jul 08, 2020 11:19 am ]
Post subject:  Re: Build started
Welcome back!


Sent from my iPhone using Tapatalk Pro
Author:  banjopicks [ Wed Jul 08, 2020 12:22 pm ]
Post subject:  Re: Build started
Well so much for moving ahead. After removing the strapping I noticed about half of the treble side wasn't clamped down tight due to misalignment. I'll be taking the back off and I used freakin Titebond. I'm thinking heat gun and knife.
Author:  Clay S. [ Wed Jul 08, 2020 9:15 pm ]
Post subject:  Re: Build started
Heat gun and knife should work. If you have a stainless knife you can also use vinegar to soften titebond (as well as many other glues). It may help you with the cleanup as well. Then rinse with clean water and let dry. Carbon steel knives react with vinegar ans cause a black stain.
Author:  banjopicks [ Thu Jul 09, 2020 3:59 am ]
Post subject:  Re: Build started
I have the back off. It's in pretty bad shape with some large cracks and other shop rash. It's amazing what this piece wood must have gone through while i was doing other things and moving from place to place. I'm going to put it aside for something else and use another back I have glued up. Just need to add a back strap to it and braces.
Author:  banjopicks [ Thu Jul 09, 2020 7:46 am ]
Post subject:  Re: Build started
Before I go any further I want to build a go-bar deck. I noticed some folks double up on the bottom 3/4" MDF but go single on top? Why would that be?
Author:  doncaparker [ Thu Jul 09, 2020 8:18 am ]
Post subject:  Re: Build started
Hutch—

The direct answer to your question is because flexing of the deck is an issue on the bottom (even a little bit is unwelcome), but not a problem (as long as it is only minor flexing) on the top. On the bottom, the deck is the surface against which the dished workboard registers. The workboards flex if you let them. Having a floppy bottom deck would allow the bottom deck to bulge out the middle, potentially making the deck unstable (imagine a flat deck with a bulge in the middle, on the bottom), but it would also allow the dished workboard to flex, taking a shape slightly off from the curve you intended. That might not be a big deal, but it is easily prevented by making the bottom deck less flexible. The upper deck can flex a fair amount and it doesn’t matter, as long as your go bars are long enough to stay flexed when the upper deck bulges out a bit.

Going a bit beyond your question, I recommend not using MDF for the upper or lower decks. MDF is fine for the dished workboards, but you should want something than can hold up better for the upper and lower decks. Maybe MDF will work fine, but construction grade plywood is available, cheap, and works great.

Finally, just so you know, I made a torsion box for my lower deck. Absolutely no flexing. But I just use a single layer of plywood for the upper deck. It flexes a fair amount, but it doesn’t matter.
Author:  banjopicks [ Thu Jul 09, 2020 8:31 am ]
Post subject:  Re: Build started
Thank you. Plywood it is. I have some 1/2" plywood that was left behind in the house I just bought. Now I know where to use it. I can double it up or make a torsion box.

Next is the size of the threaded rods, seems to be anywhere from 1/4" to 3/4". I'm thinking 3/8" would be good. Then, rods. I have a bunch made out of scrap walnut that seem to work ok but I think I'd like to make some spring loaded ones like I saw in one the threads here. I think it was Waddy's setup.
Author:  banjopicks [ Thu Jul 09, 2020 8:48 am ]
Post subject:  Re: Build started
I've also seen the deck connecting rods made from wood. What's the drawback to that method as I don't see a lot of it. I'm guessing they're held together with deck screws so the would probably need to be hardwood of some kind. The less stuff I have to buy the better. At least for now.
Author:  doncaparker [ Thu Jul 09, 2020 9:42 am ]
Post subject:  Re: Build started
Hutch--

There are a few downsides to using wood for the four posts that separate the upper deck and lower deck.

First, you were admiring my 4" spacer idea in the other thread. I don't think you can make that work unless you are using threaded rods for (or as part of) the four posts. But I can see the virtue of using both the wood and the threaded rod. I used thick plastic conduit, and ran the threaded rod through it. You can use the wood the same way I used the conduit, and have 4" pieces of wood as spacers.

Second, while it might be OK to screw into the end grain of each post, I would constantly worry about how strong those connections are. If you use a lot of go bars, and if the go bars exert significant pressure, that's a whole lot of pressure trying to push those deck screws out of the end grain of the posts.
Author:  banjopicks [ Thu Jul 09, 2020 9:51 am ]
Post subject:  Re: Build started
Thanks, I'll stick to the threaded rods.
Author:  doncaparker [ Thu Jul 09, 2020 10:09 am ]
Post subject:  Re: Build started
No worries. Regarding the size of the rods, I use 1/4" with no problem. But I am also using it inside the plastic conduit, and through the slots in the 4" wooden spacers. On their own, 1/4" rods might allow too much side-to-side flexibility. Something thicker might be better if you are not going to use wood (or plastic conduit) for the posts along with the rods.
Author:  banjopicks [ Thu Jul 09, 2020 10:16 am ]
Post subject:  Re: Build started
I'm going to use PVC pipe with 1/4" rods.
Author:  SteveSmith [ Thu Jul 09, 2020 10:26 am ]
Post subject:  Re: Build started
5/16"-18 or 3/8"-16 all-thread are cheap at the local hardware or box store, plenty strong enough (not likely to bend), and you can get jig handles for either one (eBay Innovative Components). EDIT: I saw you were going to use 1/4" and that should work fine too. Max pressure is probably around 300 lbs.

My GoBar deck is made of 2 layers of 24" square, 3/4" plywood for top and bottom. I used 1/2"" all thread (too big but I had it)) covered with vinyl tubing. The deck sits on a cart with casters that stores the go-bars and other gluing stuff along with my vacuum pump. The cart is on casters so I can pull it out and spin it around while I work which Is a super-convenient feature. Go-bars are 3/16" (I think) fiberglass from a kite supply place that provide about 7.5 lbs of force each.

I ended up making a booster seat for mine which works just fine but I probably would have made the spacers if I had seen this sooner (or thought of it myself).

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Author:  doncaparker [ Thu Jul 09, 2020 11:04 am ]
Post subject:  Re: Build started
Hutch--

Steve and I are on the same page regarding the virtues of a dedicated cart for the go bar deck. See this thread for my "pre-spacer" setup (you already know about the "post-spacer" setup, which was a small but important improvement):

viewtopic.php?f=10101&t=51518&hilit=deck

I particularly like my USS Enterprise D feature of being able to separate the saucer section. :D
Author:  BradHall [ Thu Jul 09, 2020 11:53 am ]
Post subject:  Re: Build started
I have a 3/4” base on my go bar deck. When gluing braces I just put rubber type shelf liner on the correct radius dish and it sits in the base. No deflection or slippage. I also put a piece of pegboard on the bottom side of the top deck plywood to lock the rods in place. I use an elevated OM shaped piece of plywood to set the box on to clamp the top and bottom plates. A 1/4” thick x 2” wide guitar shaped caul Between the clamps and the plate distributes pressure evenly around the perimeter and protects from clamp marks.
Author:  banjopicks [ Thu Jul 09, 2020 12:06 pm ]
Post subject:  Re: Build started
I like the cart idea as well. I have space on one of my benches for now, the cart will come later. I'm trying to put everything in the shop on wheels. I'm getting there. I have so much to do in this new basement. I'm really really short on receptacles, everything is plugged into the lighting circuit, unbelievable.
Author:  CarlD [ Thu Jul 09, 2020 12:12 pm ]
Post subject:  Re: Build started
Here's a pic of the torsion box and cart for mine. Note the box has space for the rods and provision for F clamps.
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