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Summer Uke Build #10: Gluing the back... or not.

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Blog entry by onoitsmatt posted 12-30-2016 08:55 PM 579 reads 0 times favorited 4 comments Add to Favorites Watch
« Part 9: Not summer anymore but still a uke build Part 10 of Summer Uke Build series Part 11: Glue the back / go-bar deck »

Last night I picked up a bunch of #64 rubber bands from Office Max and decided to use them to glue the back on the uke.

The back was radiused using the radius dish I made, so I thought I’d screw some 1” drywall screws part-way through the back side perimeter of the radius dish to use as anchors for the rubber bands.

I tied rubber bands together to get them long enough. I decided 4 in a row was a good number, allowing enough length span the 2’ radius of the dish and if I wanted to use 3 rubber band lengths, I could just hook the third rubber band in a chain of 4 instead of using all 4. I covered the top with part of an old T-shirt to protect it from the rubber bands and stretched a few accross connecting each end to opposing screws on the underside of the dish.

After gluing up and adding a lot of rubber bands, there were still two small areas that didn’t appear to be getting enough pressure to make proper contact between the back and sides. I kept adding more and more rubber bands, but it didn’t seem to help. The clock was ticking on the glue setting, so decided to take the rubber bands off and pull the back off and clean up and try another approach. It seems the 2’ radius dish (I built to use for guitar building) is just too wide for the Uke to sit on and get adequate downard pressure. The rubber bands were stretching too much across the width of the dish and not pulling straight down at all. So I decided to abandon the rubber band approach and use a go-bar deck instead. I was planning to build the go-bar deck anyway, but was able to get away with bracing the radiused back using clamps and thought I could do this rubber band business for gluing the back to the sides. But since it didn’t work out and I was planning to do the go-bar deck anyway, I decided to do that instead.

I used some repurposed (from an old project) baltic birch plywood, 4 pieces of 36” long threaded rod (7/16” diameter was the only diamter they had 4 pieces of in stock, otherwise I would’ve used 1/2”), washers, nuts, 1/2” PVC pipe and some rubber shelf liner. Using the 3M spray adhesive, I attached the rubber shelf liner to one of the pieces of plywood (Plywood is 24”x24”).

I drilled holes in all four corners of both pieces of plywood. I stacked the two pieces on top of each other to ensure the holes were alligned for both pieces of plywood. Then threaded a nut and washer onto the threaded rod, dropped the rod into one hole, and put a washer and nut on the underside to hold it in place. Put a piece of 1/2” PVC over the top of that and you have this:

The top of the PVC will provide additional support to the top sheet of plywood and adds rigidity to the whole structure.

I bought a bunch of 4’ long fiberglass reflector rods from Home Depot to use as the go-bars. After measuring, it seemed around 29” length was about what I’d need to maximize the overhead space to work in with the go-bar deck, but decided on 24” just to be sure and also because I can cut the rods in half and get twice as many go-bars. I bundled them up with tape and used a hack-saw to cut them while wearing a respirator and safety glasses to avoid exposure to the fiberglass dust.

The end result was a bunch of 2’ long rods. I bought some wire-shelf rubber nib thingys to go on the ends of the bars to give them a little more staying power.

I wound up with a bunch of 1/2” nuts instead of 7/16” nuts (someone must have hung them on the wrong rack at the store!) so I couldn’t complete the construction of the deck today. Will hopefully get the go-bar deck done tonight or tomorrow and will try to use it to glue the back in place over the weekend.

-- Matt - Phoenix, AZ



4 comments so far

View robscastle's profile

robscastle

4873 posts in 2169 days


#1 posted 12-30-2016 11:10 PM

Go to a hardware store again and buy some good quality sandbags partialy fill them with sand and use some to he flex to form the contour you want then pile the rest them on!

otherwise raid the linen cupboard and use old pillow cases, (get permission firist, or you may hear an odd noise then see stars)

-- Regards Robert

View onoitsmatt's profile

onoitsmatt

389 posts in 1140 days


#2 posted 12-31-2016 03:57 PM

Ha. Yeah. I wonder how well the top will hold up to the stress of that kind of downward pressure. I did finish up the go-bar deck last night and am hoping to get out there for an hour or so today and try to glue-up the back. If I can have the box finished before 2017, that’ll be a small win. Still a long way to go with the neck, fretboard, frets, tuners, bridge, nut, saddle, and on and on. But finishing the box feels good.

Thanks for reading/commenting, Robert!

-- Matt - Phoenix, AZ

View Smitty_Cabinetshop's profile

Smitty_Cabinetshop

15280 posts in 2583 days


#3 posted 01-02-2017 01:53 AM

That sandbags suggestion is a solid one. There are three of them in my shop currently, and it’s when I forget to use them that things don’t go well. Especially for non-standard glue-up situations like uke building (? what am I saying, I’ve never built a uke..)

Anyway, I’ve enjoyed following along Matt!

-- Don't anthropomorphize your handplanes. They hate it when you do that. -- OldTools Archive --

View onoitsmatt's profile

onoitsmatt

389 posts in 1140 days


#4 posted 01-02-2017 03:47 PM

Thanks Smitty! I do like the sandbag idea, but is likely better suited to clamping things that require a little less finesse.

Thanks for your input and encouragement!

-- Matt - Phoenix, AZ

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